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Relative value to surgical patients and anesthesia providers of selected anesthesia related outcomes

Relative value to surgical patients and anesthesia providers of selected anesthesia related outcomes Background: Anesthesia side effects are almost inevitable in most situations. In order to optimize the anesthetic experience from the patient's viewpoint, it makes intuitive sense to attempt to avoid the side effects that the patient fears the most. Methods: We obtained rankings and quantitative estimates of the relative importance of nine experiences that commonly occur after anesthesia and surgery from 109 patients prior to their surgery and from 30 anesthesiologists. Results: Pain was the most important thing to avoid, and subjects allocated a median of $25 of an imaginary $100 to avoiding it. Next came vomiting ($20), nausea ($10), urinary retention ($5), myalgia ($2) and pruritus ($2). Avoiding blood transfusion, an awake anesthetic technique or postoperative somnolence was not given value by the group as a whole. Anesthesiologists valued perioperative experiences in the same way as patients. Conclusions: Our results are comparable with those of previous studies in the area, and suggest that patients can prioritize the perioperative experiences they wish to avoid during their perioperative care. Such data, if obtained in the appropriate fashion, would enable anesthetic techniques to be compared using decision analysis. Macario et al [1] obtained rankings for 10 states such as Background Surgery and anesthesia result in the development of pain, pain, nausea, somnolence and sore throat that might be nausea and other adverse effects. Historically, physicians experienced after general anesthesia from 101 patients have applied their own judgments in determining which prior to surgery using an anonymous questionnaire. They of these experiences are most important to avoid and have found that vomiting, gagging on the endotracheal tube, designed anesthetic and surgical techniques accordingly. pain and nausea were the least desirable outcomes in de- However, in order to provide the most satisfactory out- scending order of importance. Subjects were asked to im- come to the person actually experiencing the process, it agine that they had a fixed sum of money ($100) to spend makes intuitive sense to try to understand which adverse on avoiding all of these states and to allocate all the mon- outcomes are most disliked by patients and to incorporate ey in proportion to his/her desire to avoid each state. The these preferences into the design of perioperative care. mean dollar value allocated to each state was taken to be the relative value of avoiding it. Subjects completed the questionnaires without direct assistance from the Page 1 of 8 (page number not for citation purposes) BMC Medical Informatics and Decision Making 2003, 3 http://www.biomedcentral.com/1472-6947/3/3 investigators. Gan et al [2] obtained estimates of how gy applied to a fanciful scenario involving a tornado's ef- much money post-surgical patients would have been will- fect on the subject's home (see Additional File 1:Appendix ing to pay to avoid nausea and vomiting by administering 1). a computer-based questionnaire. They found a median value of $56, and derived covariates (actual nausea, actual Anesthesia Providers vomiting, increasing income, increasing age and presence Each Staff and Resident member of the Department of An- of health insurance), which independently increased this esthesiology at the University of Alberta Hospitals was amount. They did not examine other adverse postopera- asked to participate. tive states. Engoren and Steffel [3] asked 60 patients in the pre-operative holding area of their hospital to complete a Interview and Data collection questionnaire about their previous experience with five Subjects were interviewed according to a standardized common post anesthesia side effects and how much they written sequence (see Additional File 2:Appendix 2) by a would be willing to pay to reduce or avoid such phenom- single, trained interviewer. Demographic data, education- ena for their immediately forthcoming operation. Only al level, and in the case of the provider group, number of about 25% of the group thought it worth spending hypo- years of anesthesia experience, were recorded. Data con- thetical money to avoid nausea, emesis, sore throat, head- cerning the subject's projected anesthesia plan or actual ache or pain, and the dollar values cited ranged widely. anesthesia course as a patient were not collected. Then, descriptions of 10 perioperative experiences (nine experi- We chose to try and validate and expand previous work in ences of interest plus the normal state) were presented to this field. Instead of an anonymous questionnaire-based the subject in random order, both verbally and written on design, we sought to maximize comprehension of and file cards. The descriptions for 5 of these states were taken compliance with the study objectives by applying screen- from a published study [1] ('nausea', 'normal', 'pain', ing tests and performing standardized subject interviews. 'somnolence', 'vomiting'). We chose these states because We also sought to obtain values for some adverse effects they were amongst the ones deemed most unpleasant in that had not previously been studied. previous work. The other five (being intentionally awake during surgery, blood transfusion, postoperative myalgia, The specific objectives of this study were, by using a stand- pruritus and urinary retention) were derived and refined ardized interview technique, to by a focus group of three anesthesiologists from our de- partment. These were chosen either because they each de- 1. Obtain rankings of unpleasantness and relative values scribe something that is associated with the regional for nine known experiences known to be associated with anesthesia experience, or that can in theory be avoided or general and regional anesthesia ameliorated by changes in anesthesia technique in some circumstances (table 1). 2. Obtain the same values from a group of anesthesia pro- viders and describe any differences Subjects ranked the states in descending order of unpleas- antness, and re-ranked them as they wished until they were sure of the desired order. Methods Ethics board approval was obtained, and written in- formed consent obtained from each participant. Thereafter, subjects were asked to imagine that they had a fixed sum of money ($100) to spend on avoiding any or Subjects all of these postoperative states. Subjects were asked to Surgical Patients 'pay' to avoid each in proportion to his or her relative de- Almost all persons undergoing elective surgery at the Uni- sire to do so. Zero ratings and tied ratings were explicitly versity of Alberta Hospitals undergo preoperative evalua- permitted; Subjects were encouraged to reflect their own tion in the Pre-Admission Clinic. The hospital's elective opinions. The interviewer was careful to remind the sub- adult surgical repertoire consists almost entirely of major jects that there was no true or correct answer, and requests procedures, in a population with high co-morbidity. A for information about other subjects' ratings were de- 20% random sample of each day's clinic attendees was in- clined. In the event of a finalized total allocation not vited to participate in the study, by selecting from the equal to $100, the interviewer helped the subject adjust day's schedule using a table of random numbers. Persons the scores, in proportion to those expressed, to total $100. aged under 18, or who were not fluent in English were not When this was necessary, the interviewer took care to en- approached. Data obtained from subjects who demon- sure that the ratio of the values for each state as expressed strated difficulty understanding the study's core concept by the subject were preserved in the final values (for exam- was discarded. This was determined by failure to correctly ple, a subject who rated three states as $40, $25 and $15 answer a screening question using the study's methodolo- and the remainder at $0 (total =$80) would have had Page 2 of 8 (page number not for citation purposes) BMC Medical Informatics and Decision Making 2003, 3 http://www.biomedcentral.com/1472-6947/3/3 Table 1: Descriptions of Adverse Effects Effect Description Awake During Surgery You are lying on your back in the Operating Room. You are wide-awake. You cannot see the surgery, but you can see people moving around the room, and can hear everything that goes on. Your operation is going on but you cannot feel or move the part that is being operated on. There is no pain. Blood Transfusion You are in the recovery room. Your surgery is finished and you feel fine. You are told that you were given two pints of blood from the blood bank during the surgery because you needed it. Myalgia It is the day after your surgery. All your muscles ache for the whole day, as if you had flu. The ache gets worse when you try to move, but you manage to get around Nausea You are lying on your side, awake and aware of your surroundings in the recovery room. You are extremely queasy, as if you were on a boat in rough seas. The least movement makes the nausea worse Normal You are lying on your back, awake and alert. You feel no pain or nausea, feel good and are ready to go home Pain You are lying on your back, awake and aware of your surroundings in the recovery room. Your surgical incision really hurts, as if a knife was stabbing you. Movement makes the pain worse, and no position seems to make it better Pruritus You are sitting up in your hospital bed after the operation. You feel itchy all over and have to scratch yourself often. Somnolence You are in the recovery room and are drifting off to sleep even though you want to stay awake. You are unable, despite your best effort, to stay awake long enough to tell the nurse how you are feeling Urinary Retention You are in the recovery room, awake and alert. You want to pass urine (water) but no matter how hard you try, none comes out Vomiting You are lying on your side, awake and aware of your surroundings in the recovery room. You feel waves of nausea and are throwing up. Your abdominal and chest muscles ache from vomiting these responses adjusted to final scores of $50, $31.25, the study were more likely to be over 65 (65% vs 28%, p $18.75 and the remainder at $0 (total=$100). In this = 0.001) than those who did, but educational levels did manner, we sought to arrive at relative, (but not absolute) not differ. Data was obtained from all 30 anesthesia pro- indices of unpleasantness for each of these states. viders approached out of an available pool of 35 and was complete in every case. Statistical Analysis Data was entered in to a computerized spreadsheet and a Demographic data 10% random sample was crosschecked independently for Both genders, all adult age groups and educational levels coding errors. Statistical analysis was performed using SAS were represented in the subject group: version 8. Frequency distributions for the outcome varia- bles were described using modal scores for the ordinal rat- Ranking of Perioperative experiences ing of each effect, and median values and interquartile Figure 1 shows the frequency distribution of the ranking ranges for the relative value of each effect. Congruence be- for each effect. Table 3 shows the order in which the group tween the rating and relative value attributed to each effect ranked the effects in descending order of unpleasantness, was measured by Pearson's rank correlation coefficient. and the relative value attached to each, as estimated by the Comparisons of effect magnitude between subgroups was median fraction of $100 that the group was willing to pay performed using 2-sided Wilcoxon's Rank Sum Tests and to avoid it a significance level of 0.05. In the subject group as a whole, pain was felt to be the Results most important thing to avoid. Vomiting came second, Subject flow but the value to subjects of avoiding vomiting was of the One hundred and thirty-one surgical patients agreed to same order of magnitude ($20 vs $25). Avoiding nausea participate. Sixteen subjects did not understand the was half as valuable as avoiding vomiting, and 40% as im- screening questions or gave incorrect answers to them, portant as avoiding pain. Subjects placed at least some four interviews were terminated in order to avoid delaying value on avoiding urinary retention, myalgia and pruritus, the subject's progress through the clinic, one subject be- but none, in the aggregate, on avoiding blood transfusion, came acutely unwell, and one withdrew without stating having an awake anesthetic technique or somnolence in why. One subject passed the screening test, and was able the recovery room. The (hypothetical) completely normal to provide ratings, which were used, but not relative val- state was, as expected, rated as the most desirable, and no ues for the perioperative experiences. Thus, 109 patient one was willing to pay to avoid it. subjects completed the study. Their demographic charac- teristics are shown in table 2. Those who did not complete Page 3 of 8 (page number not for citation purposes) BMC Medical Informatics and Decision Making 2003, 3 http://www.biomedcentral.com/1472-6947/3/3 Table 2: Demographic characteristics of subjects Surgical patients (n = 109) Anesthesia providers (n = 30) Male gender 59 (54%) 22 (73%) Age 18–35 24 (22%) 11 (37%) 36–64 55 (50%) 19 (63%) 65+ 30 (28%) 0 Education 12 or less 65 (60%) - Beyond grade 12 44 (40%) - Anesthesia provider experience Less than 8 years - 15 (50%) 8 years or more - 15 (50%) Table 3: Ranking and relative values of adverse effects. Adverse effect Modal ranking Number of subjects ranking this Relative value ($) – median Relative value ($) - as the most unpleasant adverse interquartile range effect Pain 1 (most unpleasant) 68 (49%) 25 17–40 Vomiting 2 33 (24%) 20 10–25 Nausea 3 4 (3%) 10 4–20 Urinary retention 5 4 (3%) 5 0–14 Myalgia 5 1 (1%) 2 0–8 Pruritus 6 1 (1%) 2 0–8 Blood transfusion 8 6 (4%) 0 0–10 Awake during surgery 9 22 (16%) 0 0–11 Somnolence 9 0 0 0–2.5 Normal 10 (least unpleasant) 0 0 0–0 In general, gender did not make a difference in effect rank- unpleasant effects the lowest rank order number but as- ing or relative value, but there was one exception; men at- signed them the largest sums of money. tached a higher value to avoiding urinary retention than women (median $9.50 vs $1.50, p < 0.0001). Discussion Our data confirms the ability of surgical patients to quan- Subjects aged 65 or older attached no value to avoiding a tify their preferences for perioperative experiences result- blood transfusion, while younger subjects did ($0 vs ing from anesthesia and surgery. $2.50, p = 0.002). There were no other age-related differ- ences. Educational level (whether or not the subject had Patient satisfaction with anesthesia is a complex and high- been educated beyond high school) did not affect ratings. ly individual construct [4]. However, it seems logical to as- Anesthesia providers rated and valued effects no different- sume that in a situation where a variety of safe and ly from surgical patients, and being a provider with more effective techniques or drug sequences are available that experience made no difference. We did not collect data on anesthesia experiences that minimize the adverse effects previous surgical or anesthetic experiences because a pre- the patient fears the most will be the most favorably re- vious study in the area did not show these factors to affect ceived. We have made quantitative estimates of how a pre- preferences [1]. surgical population at a tertiary-care Canadian teaching hospital values a selected range of perioperative experi- For the most part, strong correlations were found between ences. The summary data should be viewed in the context the ranking of an experience and the amount of money of wide variation in certain areas (figure 1). This reflects the subject would have paid to avoid it (Table 4). These the fact that these are individual choices, which will nec- correlations are negative, since subjects assigned the most essarily be influenced by many factors not quantified Page 4 of 8 (page number not for citation purposes) BMC Medical Informatics and Decision Making 2003, 3 http://www.biomedcentral.com/1472-6947/3/3 Figure 1 Rating of individual states (1 = most unpleasant, 10 = least unpleasant) Page 5 of 8 (page number not for citation purposes) BMC Medical Informatics and Decision Making 2003, 3 http://www.biomedcentral.com/1472-6947/3/3 Table 4: Correlation between effect rank and relative value for adverse effects Adverse effect Pearson Correlation coefficient p Pain -0.67 <0.0001 Vomiting -0.61 <0.0001 Nausea -0.70 <0.0001 Urinary retention -0.67 <0.0001 Myalgia -0.55 <0.0001 Pruritus -0.60 <0.0001 Blood transfusion -0.74 <0.0001 Awake during surgery -0.74 <0.0001 Somnolence -0.50 <0.0001 Normal -0.21 0.015 here, such as personality and past experience. Nonethe- subjects a list of risks and rates for the various potential less, trends are clearly visible, and by using medians and complications of blood transfusion, we think it unlikely non-parametric statistical tests, we have attempted to that subjects were entirely unaware of this, given the reflect the feelings of the bulk of the sample and minimize amount of attention that Canadian society has paid to this the effect of outliers. topic recently [5]. This result may reflect high confidence in our ability to minimize these risks. Alternatively, since Pain was the most feared effect in our subject group. Sub- we have derived relative, not absolute values for avoiding jects allocated a quarter of their available imaginary re- the perioperative experiences in question, it is possible sources to preventing it. In recent years, the effective that avoiding blood transfusion would have accrued more treatment of post-surgical pain has become a major objec- value if we had offered it alongside a range of less impor- tive of many anesthesia departments, and our results tant choices. would appear to indicate that this is time and effort ap- propriately spent. Interestingly, many of our subjects rat- The rating of 'being awake during surgery' also has a bi- ed vomiting as being worse than pain. In fact, only modal distribution. Although the state was given a low 62(45%) of the group gave pain a worse value than vom- overall relative value, 16% of subjects ranked it as the iting: 47(34%) valued pain and vomiting as equally bad most unpleasant thing. Despite careful explanation, we and 29(21%) were prepared to pay more to avoid vomit- may have failed to adequately specify that the question re- ing than pain. If the values for nausea and vomiting are lated to being intentionally awake, as part of an anesthetic summed, 71(51%) subjects valued prevention and treat- technique in which the body part being operated on is in- ment of nausea and vomiting more highly than the treat- sensate. Some subjects may have confused this with intra- ment of pain. In the work of Macario et al[1] vomiting was operative awareness, a catastrophic complication of actually the most feared outcome, although the relative general anesthesia in which inadequate anesthetic depth values allocated to the treatment of vomiting and pain goes undetected, yet evasive motor response is made im- were similar ($18.05 +/- 1.09 and 16.96 +/- 1.59 respec- possible by the use of muscle relaxant drugs. An alterna- tively). This suggests that we should expend as much ef- tive interpretation is that, the absence of pain fort in the prevention and treatment of nausea and notwithstanding, the idea of seeing and hearing the activ- vomiting as we do for pain, something that most anesthe- ity of the operating room is noxious to some people. sia services, including our own, would find hard to claim. Clinical experience supports the idea that some people find the idea of awake surgery very hard to accept. Three other perioperative experiences were also given non-zero median values: urinary retention, myalgia and There is evidence that our results are internally consistent. pruritus but the values were an order of magnitude small- An outcome free of adverse effects was rated as the most er than pain or emesis. desirable, as one would have expected, and the adversity rating of a given effect was strongly correlated with the We were surprised to find that the avoidance of a blood amount of money a subject would have paid to avoid it. A transfusion was, in the aggregate, not felt to be worthy of measure of external consistency is the way in which our re- expenditure in the context presented, although the bimo- sults are comparable with previous work in the area, from dal shape of the rating curve suggests that for some peo- which we reproduced the written descriptions of five of ple, this is an important issue. Although we did not offer the effects. Table 5 compares the relative values for four of Page 6 of 8 (page number not for citation purposes) BMC Medical Informatics and Decision Making 2003, 3 http://www.biomedcentral.com/1472-6947/3/3 Table 5: Ratings for four adverse effects common to the present study and that of Macario et al Present Study Macario et al Effect Mean relative value ($/100) Standardized relative value Mean relative value ($/100) Standardized relative value (Somnolence = 1.00) Mean (Somnolence = 1.00) Mean (SD) (SD) Somnolence 2.19 1.00 (2.44) 2.69 1.00(0.93) Nausea 12.76 5.80(4.80) 11.82 4.40(3.25) Vomiting 19.41 8.87(6.32) 18.05 6.70(4.07) Pain 29.16 13.3(8.50) 16.96 6.30(5.94) the five perioperative experience descriptions which were aspects comes from the zero value given to avoiding postoperative somnolence. This might suggest that newer, more expensive anes- common to both studies, expressed as multiples of the thetic agents, which are used on the basis that recovery will be faster value of the effect given the smallest non-zero rating [9], are unnecessary, but this ignores any safety enhancement that (somnolence). (Mean values are reported for the present might accrue from having a more awake patient in the recovery study, not medians as in the previous tables, in order to room, or the economic benefits of faster discharge. Whether utilizing conform to the report of the other study). The differences anesthesia techniques that incorporate individual patient preferenc- between the two study populations are not different (p > es results in improved function or quality of life in the postoperative period is not known. 0.05 by t-test), suggesting reliability of the method. We did not evaluate catastrophic or very rare events, believing this to be too burdensome and upsetting for our pre-surgical population. The lack of difference between anesthesia provider and surgical pa- However, the quantification of the relative value of avoiding such tient values suggests that we are sensitive to our patients' needs in events would be necessary if decision analysis of anesthetic choices this regard. It would be unfortunate if the necessary time to discuss were to be fair. Catastrophic yet very rare outcomes might, by their these and other issues with patients prior to surgery were to become values alone, substantially influence decision tree outcome. It may excessively eroded as patterns of surgical care delivery change to pro- be that values provided by anesthesia providers would suffice, since mote the ever more efficient use of resources. this study indicates that in general, anesthetists and patients report Among the limitations of the method we used is the idea that the similar values. $0–$100 framework for expressing relative value may have been too We regard this as an early step on the road to incorporating patient restrictive. In order to value a given effect as more than 100 times preferences into anesthetic decision-making. If fair comparison is to worse than another, for instance, it would have been necessary to be made between anesthetic regimes then a comprehensive list of choose fractional dollar amounts. While this was allowed, few sub- perioperative experiences attributable to each technique must be jects chose this option. The maximum relative value difference al- available, and contain absolute values for patient preference. Choos- lowed in our study would have been $99.99 vs $0.01, but there were ing the best anesthetic, from the patient's point of view at least, then no such choices. In addition, since the dollar amounts expressed had becomes amenable to formal decision analysis. Absolute values, or to add to $100, this was not a true 'willingness to pay' study, a tech- utilities, for perioperative experiences must, in general, be obtained nique that allows subjects (and therefore health care providers and using so called 'standard gamble' questioning[10], and this has yet industry) to determine the market value of an intervention[6]. Our to be done in pre-surgical patients. We concur with previous workers results say little about how much real money one of our subjects in this area in suggesting that that quantification of patient prefer- would have been willing to spend to avoid, say, perioperative vom- ence for perioperative experiences is reliable. iting, and still less about how much another patient, one outside our Anesthesia providers are charged with the responsibility of choosing fully-funded open access system, would approach the same choice if the best anesthetic for the patient. This choice may, in certain cir- it were available. However, since the values expressed by our subjects cumstances, have little or nothing to do with patient preference (for were expressed using hypothetical dollars, our results are unlikely to example, in the case of a potentially difficult airway which must be have been influenced by the subject's financial circumstances, an im- secured prior to induction of general anesthesia for safety). Our portant limitation of willingness to pay studies[7]. We may have study shows that in less extreme circumstances, the shared decision come closer to asking 'how important is this adverse effect to you ?' making dialogue that currently takes place between provider and pa- rather than 'what could you afford to pay to avoid this adverse effect tient is amenable to quantitative preference analysis. Incorporating ?' by choosing this approach. these preferences will better enable us to state that, within the limits Patient satisfaction is, of course, only one part of the anesthesia de- of the technology available, and subject always to considerations of cision algorithm. This is exemplified by the non-zero relative value safety, we are anesthetizing our patients in the way which suits them ($2) of avoiding postoperative myalgia. Taken in isolation, this best. might be said to argue for the exclusion of the depolarizing muscle Competing interests relaxant succinycholine, a strong risk factor for postoperative myal- None declared. gia [8] from anesthetic regimens. However, the practitioner must balance this against the relative risk of an airway problem or the ef- fect on case throughput of prolonged curarisation if an alternative re- laxant is used. Another illustration of this need to view all relevant Page 7 of 8 (page number not for citation purposes) BMC Medical Informatics and Decision Making 2003, 3 http://www.biomedcentral.com/1472-6947/3/3 Authors' contributions SR designed the study, analyzed the data and wrote most of the manuscript. PB contributed to the design of the in- terview tools, recruited subjects, performed the interviews and contributed to the writing of the manuscript Acknowledgements This work was entirely funded by the department of Anesthesiology and Pain medicine of the university of Alberta. Alex Macario MD, Assistant Professor, Department of Anesthesiology, Stanford University, Stanford, CA USA graciously allowed us to use his group's written descriptions of five post-anesthesia states. The following three individuals reviewed the manuscript and made most helpful sugges- tions prior to submission: Heather-Jane Au MD, Assistant Professor, De- partment of Medicine, University of Alberta, Edmonton, Alberta, Canada, Tracy Lieu MD, Assistant Professor, and E Francis Cook ScD, Professor, both of the Harvard University School of Public Health, Boston MA USA. Dr T Gan and Dr M Engoren reviewed the manuscript upon first submis- sion to BioMed Central and provided extremely useful feedback. References 1. Macario A Which clinical anesthesia outcomes are important to avoid? The perspective of patients. Anesth Analg 1999, 89:652-8 2. Gan TJ How much are patient willing to pay to avoid postop- erative nausea and vomiting? Anesth Analg 2001, 92:393-400 3. Engoren M and Steffel C Patient perception and monetary value to avoiding unpleasant side effects of anesthesia and surgery. J Clin Anesth 2000, 12:388-91 4. Fung D and Cohen MM Measuring patient satisfaction with an- esthesia care: A review of current methodology. Anesth Analg 1998, 87(5):1089-98 5. Hoey J The sensibility of safety: reflections on the Krever in- quiry's final report. CMAJ 1998, 158(1):92-4 6. Fisman DN Willingness to pay to avoid sharps-related injuries : A study in injured health care workers. AM J Infect Control 2002, 30:283-287 7. Raab SS Willingness to pay for new Papanicolaou test technologies. Am J Clin Path 2002, 117:524-533 8. Wong SF and Chung F Succinycholine-associated postoperative myalgia. Anesthesia 2000, 55(2):144-52 9. Ebert TJ Recovery from sevoflurane anesthesia. Anesthesiology 1998, 89(6):1524-31 10. Weinstein MC and Fineberg HV Clinical Decision Analysis. Phila- delphia, WB Saunders 1980, Pre-publication history The pre-publication history for this paper can be accessed here: http://www.biomedcentral.com/1472-6947/3/3/prepub Publish with Bio Med Central and every scientist can read your work free of charge "BioMed Central will be the most significant development for disseminating the results of biomedical researc h in our lifetime." 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Relative value to surgical patients and anesthesia providers of selected anesthesia related outcomes

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Springer Journals
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Copyright © 2003 by Rashiq and Bray; licensee BioMed Central Ltd.
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Medicine & Public Health; Health Informatics; Information Systems and Communication Service; Management of Computing and Information Systems
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Abstract

Background: Anesthesia side effects are almost inevitable in most situations. In order to optimize the anesthetic experience from the patient's viewpoint, it makes intuitive sense to attempt to avoid the side effects that the patient fears the most. Methods: We obtained rankings and quantitative estimates of the relative importance of nine experiences that commonly occur after anesthesia and surgery from 109 patients prior to their surgery and from 30 anesthesiologists. Results: Pain was the most important thing to avoid, and subjects allocated a median of $25 of an imaginary $100 to avoiding it. Next came vomiting ($20), nausea ($10), urinary retention ($5), myalgia ($2) and pruritus ($2). Avoiding blood transfusion, an awake anesthetic technique or postoperative somnolence was not given value by the group as a whole. Anesthesiologists valued perioperative experiences in the same way as patients. Conclusions: Our results are comparable with those of previous studies in the area, and suggest that patients can prioritize the perioperative experiences they wish to avoid during their perioperative care. Such data, if obtained in the appropriate fashion, would enable anesthetic techniques to be compared using decision analysis. Macario et al [1] obtained rankings for 10 states such as Background Surgery and anesthesia result in the development of pain, pain, nausea, somnolence and sore throat that might be nausea and other adverse effects. Historically, physicians experienced after general anesthesia from 101 patients have applied their own judgments in determining which prior to surgery using an anonymous questionnaire. They of these experiences are most important to avoid and have found that vomiting, gagging on the endotracheal tube, designed anesthetic and surgical techniques accordingly. pain and nausea were the least desirable outcomes in de- However, in order to provide the most satisfactory out- scending order of importance. Subjects were asked to im- come to the person actually experiencing the process, it agine that they had a fixed sum of money ($100) to spend makes intuitive sense to try to understand which adverse on avoiding all of these states and to allocate all the mon- outcomes are most disliked by patients and to incorporate ey in proportion to his/her desire to avoid each state. The these preferences into the design of perioperative care. mean dollar value allocated to each state was taken to be the relative value of avoiding it. Subjects completed the questionnaires without direct assistance from the Page 1 of 8 (page number not for citation purposes) BMC Medical Informatics and Decision Making 2003, 3 http://www.biomedcentral.com/1472-6947/3/3 investigators. Gan et al [2] obtained estimates of how gy applied to a fanciful scenario involving a tornado's ef- much money post-surgical patients would have been will- fect on the subject's home (see Additional File 1:Appendix ing to pay to avoid nausea and vomiting by administering 1). a computer-based questionnaire. They found a median value of $56, and derived covariates (actual nausea, actual Anesthesia Providers vomiting, increasing income, increasing age and presence Each Staff and Resident member of the Department of An- of health insurance), which independently increased this esthesiology at the University of Alberta Hospitals was amount. They did not examine other adverse postopera- asked to participate. tive states. Engoren and Steffel [3] asked 60 patients in the pre-operative holding area of their hospital to complete a Interview and Data collection questionnaire about their previous experience with five Subjects were interviewed according to a standardized common post anesthesia side effects and how much they written sequence (see Additional File 2:Appendix 2) by a would be willing to pay to reduce or avoid such phenom- single, trained interviewer. Demographic data, education- ena for their immediately forthcoming operation. Only al level, and in the case of the provider group, number of about 25% of the group thought it worth spending hypo- years of anesthesia experience, were recorded. Data con- thetical money to avoid nausea, emesis, sore throat, head- cerning the subject's projected anesthesia plan or actual ache or pain, and the dollar values cited ranged widely. anesthesia course as a patient were not collected. Then, descriptions of 10 perioperative experiences (nine experi- We chose to try and validate and expand previous work in ences of interest plus the normal state) were presented to this field. Instead of an anonymous questionnaire-based the subject in random order, both verbally and written on design, we sought to maximize comprehension of and file cards. The descriptions for 5 of these states were taken compliance with the study objectives by applying screen- from a published study [1] ('nausea', 'normal', 'pain', ing tests and performing standardized subject interviews. 'somnolence', 'vomiting'). We chose these states because We also sought to obtain values for some adverse effects they were amongst the ones deemed most unpleasant in that had not previously been studied. previous work. The other five (being intentionally awake during surgery, blood transfusion, postoperative myalgia, The specific objectives of this study were, by using a stand- pruritus and urinary retention) were derived and refined ardized interview technique, to by a focus group of three anesthesiologists from our de- partment. These were chosen either because they each de- 1. Obtain rankings of unpleasantness and relative values scribe something that is associated with the regional for nine known experiences known to be associated with anesthesia experience, or that can in theory be avoided or general and regional anesthesia ameliorated by changes in anesthesia technique in some circumstances (table 1). 2. Obtain the same values from a group of anesthesia pro- viders and describe any differences Subjects ranked the states in descending order of unpleas- antness, and re-ranked them as they wished until they were sure of the desired order. Methods Ethics board approval was obtained, and written in- formed consent obtained from each participant. Thereafter, subjects were asked to imagine that they had a fixed sum of money ($100) to spend on avoiding any or Subjects all of these postoperative states. Subjects were asked to Surgical Patients 'pay' to avoid each in proportion to his or her relative de- Almost all persons undergoing elective surgery at the Uni- sire to do so. Zero ratings and tied ratings were explicitly versity of Alberta Hospitals undergo preoperative evalua- permitted; Subjects were encouraged to reflect their own tion in the Pre-Admission Clinic. The hospital's elective opinions. The interviewer was careful to remind the sub- adult surgical repertoire consists almost entirely of major jects that there was no true or correct answer, and requests procedures, in a population with high co-morbidity. A for information about other subjects' ratings were de- 20% random sample of each day's clinic attendees was in- clined. In the event of a finalized total allocation not vited to participate in the study, by selecting from the equal to $100, the interviewer helped the subject adjust day's schedule using a table of random numbers. Persons the scores, in proportion to those expressed, to total $100. aged under 18, or who were not fluent in English were not When this was necessary, the interviewer took care to en- approached. Data obtained from subjects who demon- sure that the ratio of the values for each state as expressed strated difficulty understanding the study's core concept by the subject were preserved in the final values (for exam- was discarded. This was determined by failure to correctly ple, a subject who rated three states as $40, $25 and $15 answer a screening question using the study's methodolo- and the remainder at $0 (total =$80) would have had Page 2 of 8 (page number not for citation purposes) BMC Medical Informatics and Decision Making 2003, 3 http://www.biomedcentral.com/1472-6947/3/3 Table 1: Descriptions of Adverse Effects Effect Description Awake During Surgery You are lying on your back in the Operating Room. You are wide-awake. You cannot see the surgery, but you can see people moving around the room, and can hear everything that goes on. Your operation is going on but you cannot feel or move the part that is being operated on. There is no pain. Blood Transfusion You are in the recovery room. Your surgery is finished and you feel fine. You are told that you were given two pints of blood from the blood bank during the surgery because you needed it. Myalgia It is the day after your surgery. All your muscles ache for the whole day, as if you had flu. The ache gets worse when you try to move, but you manage to get around Nausea You are lying on your side, awake and aware of your surroundings in the recovery room. You are extremely queasy, as if you were on a boat in rough seas. The least movement makes the nausea worse Normal You are lying on your back, awake and alert. You feel no pain or nausea, feel good and are ready to go home Pain You are lying on your back, awake and aware of your surroundings in the recovery room. Your surgical incision really hurts, as if a knife was stabbing you. Movement makes the pain worse, and no position seems to make it better Pruritus You are sitting up in your hospital bed after the operation. You feel itchy all over and have to scratch yourself often. Somnolence You are in the recovery room and are drifting off to sleep even though you want to stay awake. You are unable, despite your best effort, to stay awake long enough to tell the nurse how you are feeling Urinary Retention You are in the recovery room, awake and alert. You want to pass urine (water) but no matter how hard you try, none comes out Vomiting You are lying on your side, awake and aware of your surroundings in the recovery room. You feel waves of nausea and are throwing up. Your abdominal and chest muscles ache from vomiting these responses adjusted to final scores of $50, $31.25, the study were more likely to be over 65 (65% vs 28%, p $18.75 and the remainder at $0 (total=$100). In this = 0.001) than those who did, but educational levels did manner, we sought to arrive at relative, (but not absolute) not differ. Data was obtained from all 30 anesthesia pro- indices of unpleasantness for each of these states. viders approached out of an available pool of 35 and was complete in every case. Statistical Analysis Data was entered in to a computerized spreadsheet and a Demographic data 10% random sample was crosschecked independently for Both genders, all adult age groups and educational levels coding errors. Statistical analysis was performed using SAS were represented in the subject group: version 8. Frequency distributions for the outcome varia- bles were described using modal scores for the ordinal rat- Ranking of Perioperative experiences ing of each effect, and median values and interquartile Figure 1 shows the frequency distribution of the ranking ranges for the relative value of each effect. Congruence be- for each effect. Table 3 shows the order in which the group tween the rating and relative value attributed to each effect ranked the effects in descending order of unpleasantness, was measured by Pearson's rank correlation coefficient. and the relative value attached to each, as estimated by the Comparisons of effect magnitude between subgroups was median fraction of $100 that the group was willing to pay performed using 2-sided Wilcoxon's Rank Sum Tests and to avoid it a significance level of 0.05. In the subject group as a whole, pain was felt to be the Results most important thing to avoid. Vomiting came second, Subject flow but the value to subjects of avoiding vomiting was of the One hundred and thirty-one surgical patients agreed to same order of magnitude ($20 vs $25). Avoiding nausea participate. Sixteen subjects did not understand the was half as valuable as avoiding vomiting, and 40% as im- screening questions or gave incorrect answers to them, portant as avoiding pain. Subjects placed at least some four interviews were terminated in order to avoid delaying value on avoiding urinary retention, myalgia and pruritus, the subject's progress through the clinic, one subject be- but none, in the aggregate, on avoiding blood transfusion, came acutely unwell, and one withdrew without stating having an awake anesthetic technique or somnolence in why. One subject passed the screening test, and was able the recovery room. The (hypothetical) completely normal to provide ratings, which were used, but not relative val- state was, as expected, rated as the most desirable, and no ues for the perioperative experiences. Thus, 109 patient one was willing to pay to avoid it. subjects completed the study. Their demographic charac- teristics are shown in table 2. Those who did not complete Page 3 of 8 (page number not for citation purposes) BMC Medical Informatics and Decision Making 2003, 3 http://www.biomedcentral.com/1472-6947/3/3 Table 2: Demographic characteristics of subjects Surgical patients (n = 109) Anesthesia providers (n = 30) Male gender 59 (54%) 22 (73%) Age 18–35 24 (22%) 11 (37%) 36–64 55 (50%) 19 (63%) 65+ 30 (28%) 0 Education 12 or less 65 (60%) - Beyond grade 12 44 (40%) - Anesthesia provider experience Less than 8 years - 15 (50%) 8 years or more - 15 (50%) Table 3: Ranking and relative values of adverse effects. Adverse effect Modal ranking Number of subjects ranking this Relative value ($) – median Relative value ($) - as the most unpleasant adverse interquartile range effect Pain 1 (most unpleasant) 68 (49%) 25 17–40 Vomiting 2 33 (24%) 20 10–25 Nausea 3 4 (3%) 10 4–20 Urinary retention 5 4 (3%) 5 0–14 Myalgia 5 1 (1%) 2 0–8 Pruritus 6 1 (1%) 2 0–8 Blood transfusion 8 6 (4%) 0 0–10 Awake during surgery 9 22 (16%) 0 0–11 Somnolence 9 0 0 0–2.5 Normal 10 (least unpleasant) 0 0 0–0 In general, gender did not make a difference in effect rank- unpleasant effects the lowest rank order number but as- ing or relative value, but there was one exception; men at- signed them the largest sums of money. tached a higher value to avoiding urinary retention than women (median $9.50 vs $1.50, p < 0.0001). Discussion Our data confirms the ability of surgical patients to quan- Subjects aged 65 or older attached no value to avoiding a tify their preferences for perioperative experiences result- blood transfusion, while younger subjects did ($0 vs ing from anesthesia and surgery. $2.50, p = 0.002). There were no other age-related differ- ences. Educational level (whether or not the subject had Patient satisfaction with anesthesia is a complex and high- been educated beyond high school) did not affect ratings. ly individual construct [4]. However, it seems logical to as- Anesthesia providers rated and valued effects no different- sume that in a situation where a variety of safe and ly from surgical patients, and being a provider with more effective techniques or drug sequences are available that experience made no difference. We did not collect data on anesthesia experiences that minimize the adverse effects previous surgical or anesthetic experiences because a pre- the patient fears the most will be the most favorably re- vious study in the area did not show these factors to affect ceived. We have made quantitative estimates of how a pre- preferences [1]. surgical population at a tertiary-care Canadian teaching hospital values a selected range of perioperative experi- For the most part, strong correlations were found between ences. The summary data should be viewed in the context the ranking of an experience and the amount of money of wide variation in certain areas (figure 1). This reflects the subject would have paid to avoid it (Table 4). These the fact that these are individual choices, which will nec- correlations are negative, since subjects assigned the most essarily be influenced by many factors not quantified Page 4 of 8 (page number not for citation purposes) BMC Medical Informatics and Decision Making 2003, 3 http://www.biomedcentral.com/1472-6947/3/3 Figure 1 Rating of individual states (1 = most unpleasant, 10 = least unpleasant) Page 5 of 8 (page number not for citation purposes) BMC Medical Informatics and Decision Making 2003, 3 http://www.biomedcentral.com/1472-6947/3/3 Table 4: Correlation between effect rank and relative value for adverse effects Adverse effect Pearson Correlation coefficient p Pain -0.67 <0.0001 Vomiting -0.61 <0.0001 Nausea -0.70 <0.0001 Urinary retention -0.67 <0.0001 Myalgia -0.55 <0.0001 Pruritus -0.60 <0.0001 Blood transfusion -0.74 <0.0001 Awake during surgery -0.74 <0.0001 Somnolence -0.50 <0.0001 Normal -0.21 0.015 here, such as personality and past experience. Nonethe- subjects a list of risks and rates for the various potential less, trends are clearly visible, and by using medians and complications of blood transfusion, we think it unlikely non-parametric statistical tests, we have attempted to that subjects were entirely unaware of this, given the reflect the feelings of the bulk of the sample and minimize amount of attention that Canadian society has paid to this the effect of outliers. topic recently [5]. This result may reflect high confidence in our ability to minimize these risks. Alternatively, since Pain was the most feared effect in our subject group. Sub- we have derived relative, not absolute values for avoiding jects allocated a quarter of their available imaginary re- the perioperative experiences in question, it is possible sources to preventing it. In recent years, the effective that avoiding blood transfusion would have accrued more treatment of post-surgical pain has become a major objec- value if we had offered it alongside a range of less impor- tive of many anesthesia departments, and our results tant choices. would appear to indicate that this is time and effort ap- propriately spent. Interestingly, many of our subjects rat- The rating of 'being awake during surgery' also has a bi- ed vomiting as being worse than pain. In fact, only modal distribution. Although the state was given a low 62(45%) of the group gave pain a worse value than vom- overall relative value, 16% of subjects ranked it as the iting: 47(34%) valued pain and vomiting as equally bad most unpleasant thing. Despite careful explanation, we and 29(21%) were prepared to pay more to avoid vomit- may have failed to adequately specify that the question re- ing than pain. If the values for nausea and vomiting are lated to being intentionally awake, as part of an anesthetic summed, 71(51%) subjects valued prevention and treat- technique in which the body part being operated on is in- ment of nausea and vomiting more highly than the treat- sensate. Some subjects may have confused this with intra- ment of pain. In the work of Macario et al[1] vomiting was operative awareness, a catastrophic complication of actually the most feared outcome, although the relative general anesthesia in which inadequate anesthetic depth values allocated to the treatment of vomiting and pain goes undetected, yet evasive motor response is made im- were similar ($18.05 +/- 1.09 and 16.96 +/- 1.59 respec- possible by the use of muscle relaxant drugs. An alterna- tively). This suggests that we should expend as much ef- tive interpretation is that, the absence of pain fort in the prevention and treatment of nausea and notwithstanding, the idea of seeing and hearing the activ- vomiting as we do for pain, something that most anesthe- ity of the operating room is noxious to some people. sia services, including our own, would find hard to claim. Clinical experience supports the idea that some people find the idea of awake surgery very hard to accept. Three other perioperative experiences were also given non-zero median values: urinary retention, myalgia and There is evidence that our results are internally consistent. pruritus but the values were an order of magnitude small- An outcome free of adverse effects was rated as the most er than pain or emesis. desirable, as one would have expected, and the adversity rating of a given effect was strongly correlated with the We were surprised to find that the avoidance of a blood amount of money a subject would have paid to avoid it. A transfusion was, in the aggregate, not felt to be worthy of measure of external consistency is the way in which our re- expenditure in the context presented, although the bimo- sults are comparable with previous work in the area, from dal shape of the rating curve suggests that for some peo- which we reproduced the written descriptions of five of ple, this is an important issue. Although we did not offer the effects. Table 5 compares the relative values for four of Page 6 of 8 (page number not for citation purposes) BMC Medical Informatics and Decision Making 2003, 3 http://www.biomedcentral.com/1472-6947/3/3 Table 5: Ratings for four adverse effects common to the present study and that of Macario et al Present Study Macario et al Effect Mean relative value ($/100) Standardized relative value Mean relative value ($/100) Standardized relative value (Somnolence = 1.00) Mean (Somnolence = 1.00) Mean (SD) (SD) Somnolence 2.19 1.00 (2.44) 2.69 1.00(0.93) Nausea 12.76 5.80(4.80) 11.82 4.40(3.25) Vomiting 19.41 8.87(6.32) 18.05 6.70(4.07) Pain 29.16 13.3(8.50) 16.96 6.30(5.94) the five perioperative experience descriptions which were aspects comes from the zero value given to avoiding postoperative somnolence. This might suggest that newer, more expensive anes- common to both studies, expressed as multiples of the thetic agents, which are used on the basis that recovery will be faster value of the effect given the smallest non-zero rating [9], are unnecessary, but this ignores any safety enhancement that (somnolence). (Mean values are reported for the present might accrue from having a more awake patient in the recovery study, not medians as in the previous tables, in order to room, or the economic benefits of faster discharge. Whether utilizing conform to the report of the other study). The differences anesthesia techniques that incorporate individual patient preferenc- between the two study populations are not different (p > es results in improved function or quality of life in the postoperative period is not known. 0.05 by t-test), suggesting reliability of the method. We did not evaluate catastrophic or very rare events, believing this to be too burdensome and upsetting for our pre-surgical population. The lack of difference between anesthesia provider and surgical pa- However, the quantification of the relative value of avoiding such tient values suggests that we are sensitive to our patients' needs in events would be necessary if decision analysis of anesthetic choices this regard. It would be unfortunate if the necessary time to discuss were to be fair. Catastrophic yet very rare outcomes might, by their these and other issues with patients prior to surgery were to become values alone, substantially influence decision tree outcome. It may excessively eroded as patterns of surgical care delivery change to pro- be that values provided by anesthesia providers would suffice, since mote the ever more efficient use of resources. this study indicates that in general, anesthetists and patients report Among the limitations of the method we used is the idea that the similar values. $0–$100 framework for expressing relative value may have been too We regard this as an early step on the road to incorporating patient restrictive. In order to value a given effect as more than 100 times preferences into anesthetic decision-making. If fair comparison is to worse than another, for instance, it would have been necessary to be made between anesthetic regimes then a comprehensive list of choose fractional dollar amounts. While this was allowed, few sub- perioperative experiences attributable to each technique must be jects chose this option. The maximum relative value difference al- available, and contain absolute values for patient preference. Choos- lowed in our study would have been $99.99 vs $0.01, but there were ing the best anesthetic, from the patient's point of view at least, then no such choices. In addition, since the dollar amounts expressed had becomes amenable to formal decision analysis. Absolute values, or to add to $100, this was not a true 'willingness to pay' study, a tech- utilities, for perioperative experiences must, in general, be obtained nique that allows subjects (and therefore health care providers and using so called 'standard gamble' questioning[10], and this has yet industry) to determine the market value of an intervention[6]. Our to be done in pre-surgical patients. We concur with previous workers results say little about how much real money one of our subjects in this area in suggesting that that quantification of patient prefer- would have been willing to spend to avoid, say, perioperative vom- ence for perioperative experiences is reliable. iting, and still less about how much another patient, one outside our Anesthesia providers are charged with the responsibility of choosing fully-funded open access system, would approach the same choice if the best anesthetic for the patient. This choice may, in certain cir- it were available. However, since the values expressed by our subjects cumstances, have little or nothing to do with patient preference (for were expressed using hypothetical dollars, our results are unlikely to example, in the case of a potentially difficult airway which must be have been influenced by the subject's financial circumstances, an im- secured prior to induction of general anesthesia for safety). Our portant limitation of willingness to pay studies[7]. We may have study shows that in less extreme circumstances, the shared decision come closer to asking 'how important is this adverse effect to you ?' making dialogue that currently takes place between provider and pa- rather than 'what could you afford to pay to avoid this adverse effect tient is amenable to quantitative preference analysis. Incorporating ?' by choosing this approach. these preferences will better enable us to state that, within the limits Patient satisfaction is, of course, only one part of the anesthesia de- of the technology available, and subject always to considerations of cision algorithm. This is exemplified by the non-zero relative value safety, we are anesthetizing our patients in the way which suits them ($2) of avoiding postoperative myalgia. Taken in isolation, this best. might be said to argue for the exclusion of the depolarizing muscle Competing interests relaxant succinycholine, a strong risk factor for postoperative myal- None declared. gia [8] from anesthetic regimens. However, the practitioner must balance this against the relative risk of an airway problem or the ef- fect on case throughput of prolonged curarisation if an alternative re- laxant is used. Another illustration of this need to view all relevant Page 7 of 8 (page number not for citation purposes) BMC Medical Informatics and Decision Making 2003, 3 http://www.biomedcentral.com/1472-6947/3/3 Authors' contributions SR designed the study, analyzed the data and wrote most of the manuscript. PB contributed to the design of the in- terview tools, recruited subjects, performed the interviews and contributed to the writing of the manuscript Acknowledgements This work was entirely funded by the department of Anesthesiology and Pain medicine of the university of Alberta. Alex Macario MD, Assistant Professor, Department of Anesthesiology, Stanford University, Stanford, CA USA graciously allowed us to use his group's written descriptions of five post-anesthesia states. The following three individuals reviewed the manuscript and made most helpful sugges- tions prior to submission: Heather-Jane Au MD, Assistant Professor, De- partment of Medicine, University of Alberta, Edmonton, Alberta, Canada, Tracy Lieu MD, Assistant Professor, and E Francis Cook ScD, Professor, both of the Harvard University School of Public Health, Boston MA USA. Dr T Gan and Dr M Engoren reviewed the manuscript upon first submis- sion to BioMed Central and provided extremely useful feedback. References 1. Macario A Which clinical anesthesia outcomes are important to avoid? The perspective of patients. Anesth Analg 1999, 89:652-8 2. Gan TJ How much are patient willing to pay to avoid postop- erative nausea and vomiting? Anesth Analg 2001, 92:393-400 3. Engoren M and Steffel C Patient perception and monetary value to avoiding unpleasant side effects of anesthesia and surgery. J Clin Anesth 2000, 12:388-91 4. Fung D and Cohen MM Measuring patient satisfaction with an- esthesia care: A review of current methodology. Anesth Analg 1998, 87(5):1089-98 5. Hoey J The sensibility of safety: reflections on the Krever in- quiry's final report. CMAJ 1998, 158(1):92-4 6. Fisman DN Willingness to pay to avoid sharps-related injuries : A study in injured health care workers. AM J Infect Control 2002, 30:283-287 7. Raab SS Willingness to pay for new Papanicolaou test technologies. Am J Clin Path 2002, 117:524-533 8. Wong SF and Chung F Succinycholine-associated postoperative myalgia. Anesthesia 2000, 55(2):144-52 9. Ebert TJ Recovery from sevoflurane anesthesia. Anesthesiology 1998, 89(6):1524-31 10. Weinstein MC and Fineberg HV Clinical Decision Analysis. Phila- delphia, WB Saunders 1980, Pre-publication history The pre-publication history for this paper can be accessed here: http://www.biomedcentral.com/1472-6947/3/3/prepub Publish with Bio Med Central and every scientist can read your work free of charge "BioMed Central will be the most significant development for disseminating the results of biomedical researc h in our lifetime." Sir Paul Nurse, Cancer Research UK Your research papers will be: available free of charge to the entire biomedical community peer reviewed and published immediately upon acceptance cited in PubMed and archived on PubMed Central yours — you keep the copyright BioMedcentral Submit your manuscript here: http://www.biomedcentral.com/info/publishing_adv.asp Page 8 of 8 (page number not for citation purposes)

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Published: Feb 13, 2003

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