Does an Acute Pain Service Improve Postoperative Outcome?

Pain relief after surgical procedures continues to be a major medical challenge. Alleviation of pain has been given a high priority by the medical profession and the health authorities. Improvement in perioperative analgesia not only is desirable for humanitarian reasons, but is also essential for its potential to reduce postoperative morbidity (1–4) and mortality (2). Inadequacies in postoperative pain relief have been evident for decades (5,6). The importance of establishing an organization for the management of postoperative pain relief, with special attention to a team approach, was proposed more than 40 yr ago (7). Although several editorials (8–10) from 1976 to 1980 again advocated the introduction of an analgesia team to supervise and administer pain relief and to take responsibility for teaching and training in postoperative pain management, almost a decade passed before a specialized in-hospital postoperative pain service emerged. Thus, in 1985 the first acute pain services (APSs) were introduced in the United States (11,12) and in Germany (13). Immediate and sustained formal support and authoritative recommendations from various medical and health care organizations promoted a widespread introduction of APSs (14–22). One document explicitly stated "that this service should be introduced in all major hospitals performing surgery in the UK"(15); this is in agreement with recommendations from the Agency for Health Care Policy and Research (United States) and the National Health and Medical Research Council (Australia), which state that all major acute care centers should have an APS (14,18). Furthermore, provision of an APS is presently a prerequisite for accreditation for training by the Royal College of Anaesthetists (23) and the Australian and New Zealand College of Anaesthetists. A Canadian survey from 1991, including 47 university-affiliated teaching hospitals, showed that 25 hospitals (53%) operated an APS and that an additional 17 (35%) were attempting to organize one (24) (Table 1). A survey in Australia and New Zealand in 1992–1993 from 111 larger institutions showed that 37 (33%) had an APS and 58 (53%) would have liked to or had plans to implement the service (25). Repeated surveys in 1994 and 1996 from New Zealand indicated in 22 larger institutions an increase from 12 to 17 APSs (29). In a European survey from 1993, including 105 representative hospitals from 17 countries, 34% of the hospitals had a formal APS (26). Forty-two percent to 73% of US hospitals, depending on size and academic affiliation, had an APS in 1995 (31,32). In the United Kingdom, the number of hospitals providing APSs increased from 3% in 1990 to 43% in 1994 (27,28,36), to 47% in 1996 (37), and to 49% in 1999 (35). In a recent survey from Germany, 36% of hospitals operated an APS, but the quality of criteria for the service was very variable (34).Table 1: National Surveys of the Prevalence of Acute Pain Services (APSs)The introduction of APSs has led to an increase in the use of specialized pain relief methods, such as patient-controlled analgesia (PCA) and epidural infusions of local anesthetic/opioid mixtures, in surgical wards. Implementation of these methods may represent real advances in improving patient well-being and in reducing postoperative morbidity (38). However, a pertinent question is whether the extensive resources allocated to these commitments have been successful and cost-effective. The objective of this study, therefore, was to critically review the literature on APSs regarding outcome: pain relief, side effects of the postoperative pain treatment, patient satisfaction, therapy-related adverse events, morbidity, hospital stay, and cost issues. Literature Search Literature was identified by a MEDLINE search from March 1966 to February 2001. The reference lists from identified articles and from relevant textbooks were then manually searched for additional papers. One-hundred-fifty-four papers were retrieved and systematically evaluated by two of the authors (MUW, PR-N) (Fig. 1). Fifty-eight were classified as expert opinions (editorials or personal experience), 48 as audits, 18 as general reviews (pain, organization, and pain-relief methods), 17 as surveys (regional, national, and international), and 13 as clinical trials.Figure 1: Number of articles (n = 154) and publication year: audit/trial (40%), survey (11%), review (12%), and opinion (38%).Objectives and Organization of an APS A formal APS is an organization dedicated to the management of acute pain in surgical patients, parturients, or other patients with acute pain (11,14,15,20). The APS has the responsibility for the day-to-day management of postoperative pain and obstetric pain and should provide an organizational framework for an appropriate level of care and monitoring adjusted to the clinical condition of the patient and the technique used (15). The APS has an important role to ensure the safety of the techniques (39–41). Establishment of programs for the identification and management of complications by in-service training for medical and nursing staff involved in the management of postoperative pain is important (15,42). The APS is committed to audits and clinical research of the efficacy and outcomes of existing and new methods of treatment (15,16,18,43,44). Recommendations for the structure of the APS were originally a multidisciplinary approach that used medical, nursing, pharmaceutical, and psychological expertise (11,15,20). In 73 of the reviewed articles relating to organizational aspects of the APS, 15 articles reported a multidisciplinary approach (physician, nurse, physiotherapist, pharmacist, or psychologist), whereas in 56, the service was strictly physician based and in 17, strictly nurse based. Twenty-four-hour coverage has been recommended (11,20,45), but in a Canadian survey, only three quarters of the services provided this level of coverage (24). It has automatically been assumed that the APS should be under anesthesiological auspices (11,15,31), but services managed primarily by ward surgeons have been reported (33,46). Outcome Data The 44 audits and 4 clinical trials containing outcome data included 84,097 postoperative patients (Table 2). Data were corrected for apparent duplicate publication. Two audit articles reported 22% of the patients (12,53).Table 2: Audits and Trials in an Acute Pain Service (APS) SettingThe studies were classified as prospective when stated so, when a prospective design was obvious, or when institutional approval was obtained before the start of the study. If none of these criteria was fulfilled, then the study was designated as retrospective. Of the 25 prospective studies identified, 5 were controlled studies, including 1 using historical controls, and 10 studies used a sequential analysis with outcome assessment before and after provision of a formal APS. Twenty-three studies used retrospective data: two studies used a sequential analysis, and one study used a matched control. The outcome variables most frequently studied were pain ratings, treatment-related side effects, and adverse events (Fig. 2). Postoperative complications, cost issues, or length of hospital stay was reported in 11 articles, including 7 prospective analyses.Figure 2: Number of studies assessing outcome variables (shaded parts of columns indicate the number of prospective, sequential studies).Pain Ratings Sequential Studies and Controlled Studies. In the 12 studies (n = 15,265) containing sequential analyses (30,50,65,67,68,72,74,77,79,81,83,86) with assessments before and after the introduction of an APS program, 9 studies (n = 9,921) indicated a lower pain score at rest (30,50,65,68,72,74,77,79,81), and 7 studies (n = 11,845) indicated a lower pain score during dynamic conditions (30,50,65,77,81,83,86). In 8 (n = 12,483) (50,68,74,77,79,81,83,86) of the 11 positive outcome studies, all of which were prospective, a statistically significant difference was observed. In the 3 remaining studies (30,65,72) (n = 3182), statistical analyses were inadequate, either because of the nonrandomized nature of the study (30) or because of an insufficient number of patients (72). The overall reduction in the percentage of patients who experienced moderate to severe pain varied from 0%(67,83) to 8%–27%(30,65,68,72,74,77) at rest and from 19%–64%(30,68,74,77,81) during activity. In the largest prospective sequential study (83), the introduction of an intensive education program in pain management for anesthesiologists, combined with individualized feedback, was associated with a significant decrease in activity-related pain scores (P < 0.01) assessed 6 h after discharge from the postanesthesia care unit (PACU). However, at the control hospital without active interventions (comprising 34% of the study patients), a similar decrease in pain scores was observed during the observation period. A change in the practice of pain management, assessed by the postoperative prescription pattern of analgesics and by the use of nerve blocks and PCA, was, however, significantly more common at the APS hospital. This study deserves attention because it is the only sequential APS study to use a control hospital. Why the introduction of an APS was not associated with a decrease in pain ratings may depend on several factors. First, a confounding factor in the study was that anesthesia residents in the 2-yr study period rotated between the study hospital and the control hospital, which obviously could have influenced practice in the control hospital. Second, during the observation period 1992 to 1994, changes in general attitudes toward pain management in regard to the more effective use of nonsteroidal antiinflammatory drugs (NSAIDs) and PCA may have affected the result. Finally, and perhaps most important, several noncontrolled, sequential studies, most of them prospective, indicate that educational measures have to be combined with preoperative information to the patient (50,68,77), guidelines (68,74), treatment algorithms and protocols (30,50,74), formal assessment and recording of pain (30,50,77), supervision of pain management by an acute pain nurse (65,68), or daily pain rounds by an APS (65,66,68,77) to improve patient pain ratings. In a prospective study by Gould et al. (50), the effect of 5 different clinically relevant sequential changes in postoperative pain management after general surgery was observed during a 9-mo period (n = 2035): introduction of a pain chart, a conventional treatment algorithm, infiltration of the incision with a local anesthetic, extended patient information, and introduction of PCA devices. The median visual analog scale (VAS) scores after major surgery (n = 1421) decreased significantly during rest from 45 (95% confidence interval, 34–53) to 16 (10–20), during movement from 78 (66–80) to 46 (38–48), and during deep inspiration from 64 (48–78) to 36 (31–38). Statistically significant changes were observed only after the two first interventions, i.e., the introduction of a pain chart and a conventional treatment algorithm. In a very large prospective study including 25 hospitals in the United States (n = 5837), by Miaskowski et al. (76), patient ratings of worst pain were significantly less in hospitals with an APS (n = 12) compared with hospitals without an APS (P < 0.00001). Although the reduction in pain on a numeric rating scale (0–10) was very small, from 7.1 to 6.8, the reduction in the number of patients with moderate to severe pain was 9% at the hospitals providing an APS (absolute numbers were not reported). A prospective study assessing a surgeon managed APS indicated a significantly improved pain score compared with control (P < 0.001), at rest (18 vs. 43) and during dynamic conditions (42 vs. 49) (46). However, the use of different scales and assessment conditions (rest/mobilization) makes comparison between studies difficult. Pain Ratings: Conclusion. Available data indicate that implementation of APSs or APS-like programs is associated with a significant decrease in patients' postoperative pain ratings. However, there are several unanswered issues: the contribution of increased awareness and importance of postoperative analgesia, the introduction of more effective regimens (i.e., epidural analgesia), the placebo or undefined effects of the twice-a-day visits of the APS (87,88), and whether there are any specific advantages of APS interventions in high-risk or acute surgical patients. Side Effects The most frequently investigated treatment-related side effects were postoperative nausea and/or vomiting (PONV) (20 of 25 studies), pruritus (15 of 25), urinary retention (7 of 25) and sedation (7 of 25). Nausea and Vomiting. The incidence of nausea reported in APS studies was influenced by sex (49,69), age (69), and surgical (49,69,70) and anesthetic (69) procedure, which is consistent with the literature (89). A significantly less frequent incidence of patient-reported nausea, assessed within 24 h after discontinuation of the primary analgesic modality, was observed in hospitals with an APS compared with control hospitals (14% and 22%, respectively) (76) (P < 0.0001). However, 4 sequential studies (30,74,77,81) (n = 5261) did not find any significant difference, although a similar trend was observed in 2 of the studies (30,74). The management of PCA by an APS seemed to reduce the incidence of postoperative nausea compared with management by a ward physician, despite an increase in opioid consumption (82). However, although PONV may be decreased by an APS, the mechanisms remain unclear as to the role of increased awareness, new strategies for antiemetic treatment, or opioid rotation. Sedation. Although several retrospective studies (n = 10,987) have not been able to demonstrate any effect on postoperative sedation score (48,54,70,81,90), in the prospective study by Miaskowski et al. (76), the percentage of patients reporting frequent sedation was significantly smaller at hospitals with an APS (15% versus 26%). The incidence of sedation has, in retrospective APS studies, been reported to be 0%–7%(48,54,70,90), which could be related to different scoring systems or to a more extensive use of postoperative opioids, as in the study by Miaskowski et al. The incidence of sedation is probably less frequent for epidural analgesia than for opioid-based PCA (48,54,70,90). Unfortunately, APS data on sedation are too heterogenous to make any valid conclusions. Urinary Retention. Surgery, anesthesia, and postoperative analgesia are factors that contribute to postoperative urinary retention (91), which may lead to urinary tract infections (92). Treatment by an indwelling catheter for a prolonged period, however, increases the incidence of urinary tract infections (93), septicemia, and mortality (94). The only sequential study on the effects of postoperative analgesia on the incidence of urinary retention reported an incidence of 5% and 9% (not significant), respectively, before and after the introduction of an APS, compared with an incidence of 6%–7% at the control hospital (83). A study by Stacey et al. (82) indicated a less frequent incidence of urinary retention when PCA was managed by an APS compared with management by primary ward physicians (5% and 28%, respectively) (P < 0.01). Although the morphine dose increased by 35%–100% in both studies after the introduction of an APS, it is interesting to note that the incidence of urinary retention did not increase. In contrast, two retrospectively conducted non-APS studies have indicated at least a sixfold increased incidence of urinary retention in patients receiving PCA compared with IM morphine after appendectomy and hysterectomy (95,96). In the study by Stacey et al., the decreased incidence of urinary retention was probably related to an increased attention to micturition problems on wards cooperating with an APS. Although several other studies indicate an increased use of opioids after the introduction of an APS (30,65,67,82), future studies should evaluate the implementation of opioid-sparing strategies, including use of regional blockade and NSAIDs on postoperative micturition problems. Side Effects: Conclusion. Few studies have systematically and in a prospective, controlled manner investigated the incidence and severity of side effects in an APS-based postoperative setting. This is unfortunate, because patients' of the efficacy and quality of postoperative care may depend on the of the side effects experienced The introduction of an APS may have been associated with less PONV and urinary but these effects are again to from common awareness and improved treatment strategies of these postoperative as to specific effects of improved analgesia by the APS. the large in APS and provided service on potential in and studies (n = assessed patients' preoperative of the postoperative pain treatment, 12 studies (n = assessed with the pain treatment, and 2 studies (n = staff of and attitudes an APS. who were for by an APS were more to less pain than after surgery In 2 of 4 prospective sequential studies (n = and a significant (P < 0.01) in score after the introduction of an APS was Miaskowski et al. (76), using a scale = very 5 = very also observed that a significantly larger percentage of patients in the care of an APS were more than patients at control hospitals (P < although ratings of the two were similar and In a retrospective (n = also observed a frequent i.e., 8 or on a scale the stated that there did not to be any between the experienced severity of pain and the In retrospective APS study the percentage of patients with PCA treatment (n = from to and with epidural treatment (n = between and A number of organizations have that measures of patient should be included in quality or outcome assessment of pain management, although the has been a of First, patient ratings of of opioid based PCA are to of epidural analgesia with local although epidural analgesia is associated with increased analgesic efficacy Second, the between patient and experienced pain severity to be very = more on the quality of between physician and patient Thus, patient ratings of as a of APS efficacy have to be evaluated audits (n = and 3 trials (n = 8 prospective studies (n = 1 survey 1 review and 5 expert opinions treatment-related adverse and blockade (7 The overall incidence of complications = epidural analgesia = was in most The incidence of complications related to the epidural analgesia was reported in 6 audits (n = and in 1 review The incidence of postoperative the of on the analgesic and was during morphine during PCA with infusions of opioids and with a of local and opioid In a study on reporting (n = by an APS, three of to the intensive care unit were Two were to analgesia, and one was by sedation during the use of are data from the sequential studies any change in the of after the introduction of an APS. The incidence of clinically significant APS after epidural analgesia from to In two prospective sequential studies, the incidence of decreased after the introduction of an APS, but the statistical level was not indicated One audit on complications reported an incidence of of In the role of an APS to be because of between The incidence of clinically significant blockade during epidural analgesia, was significantly increased for compared with and in two patients was reported in an audit Two studies reported in level of the epidural catheter was not The role of the APS to reduce the incidence of blockade be by blockade are in two that to performing the and related to an organization of the postoperative at the the or the ward complications related to blockade should be at the to and severe authors have that epidural analgesia with of local on the wards visits including by an APS at least a epidural complications reported included 1 of with urinary (n = 2 of (n = 3 of of the epidural catheter (n = and 5 of of the catheter (n = of epidural was but one was reported in the study by et al. The role of an APS for complications be In a study by et al. were reported during 1 yr in patients managed by an APS. were related to and 15 to of the were by the APS and the In a study severe complications were in of the patients of without The authors recommended in-service training programs for medical and nursing recording of identification of pain-relief and of In a large retrospective audit (n = 2 of epidural opioid of and 3 of PCA of were reported sequential studies are and because of information on and and the effect of an APS on be Conclusion. Implementation of pain management techniques with increased analgesic efficacy may lead to an increase in treatment-related morbidity, i.e., from events such as urinary retention to complications such as an epidural of safety aspects is an important objective of an APS, but the role of an APS to or reduce these events has not been This is unfortunate, because implementation and supervision of epidural analgesia is one important objective of the APS. Postoperative prospective audits (n = 4 expert opinions and 3 reviews reported on postoperative and One study (30) included an analysis of postoperative and The study by et al. reported that the incidence of lower tract on the of retrospectively decreased from to after the introduction of an APS (P < 0.01). The authors that the improved analgesia by the APS could have promoted the patients' to and with the Pain relief was provided with either PCA or epidural analgesia but the authors did not on the between the two analgesic treatment A conducted sequential study (30) (Table also seemed to indicate a decrease of lower tract from of to of after the of an APS. Unfortunately, statistical were but a a statistical difference (P < interesting prospective study by et al. investigated patients with The patients either were by an APS (n = or conventional treatment in a non-APS (n = In the APS patients opioid-based postoperative epidural or analgesia, and in the non-APS IM morphine were A significantly less frequent incidence of (P = and complications (P < 0.001), as as a significant reduction in mortality (P = were reported in patients in the APS The were significant only for patients a procedure, compared with an however, have been because patients in the non-APS were studied from to and in the APS were studied from to The may advances in the surgical in the anesthetic methods, or in the general postoperative care of advantages by methods of analgesia introduced by the APS. The in on the of from APS studies on surgical outcome are in a recent review of clinical studies of the effect of perioperative pain relief on surgical outcome In these studies, not conducted within the framework of an APS, there was that improved pain relief improved postoperative The only was epidural analgesia with local which significantly improved postoperative outcome Postoperative morbidity on and techniques such as pain relief, with or without an APS, may be to control and improve surgical outcome However, pain relief is a prerequisite for in outcome and audits (n = 6 expert 4 general and 3 trials (n = were prospective studies One study reported that patients for by an APS were significantly than patients at control hospitals and respectively) (P < In the study by et al. in patients the hospital stay was significantly (P = in the APS compared with a non-APS versus In prospective controlled study from which included patients the hospital stay for patients in the APS did not from that of and respectively) (46). are consistent with a study by et al. (83). however, to be as to the of hospital stay as an outcome Although discharge criteria are by the postoperative patient (i.e., of and and and of surgical the to discharge is variable It has been that a postoperative care program, including epidural analgesia, and and a postoperative stay after in a median hospital stay of 2 Thus, assessment of the role of the APS in reducing hospital stay is only when care and postoperative and discharge criteria are introduced In a prospective study the cost of an APS by 1 nurse and physicians and including service with was The cost data for included patients various surgical with major surgery (Table on the of surgical procedure, treatment were patient-controlled epidural analgesia PCA and epidural analgesia was used for for and blockade for patients under the care of the APS were a the service h a The cost including cost of was to a daily cost of The introduction of a program with improved pain relief, and decreased the number of patients who an stay in the postoperative period after major of a discharge from the high were (n = to The authors included this in the for a of This is an interesting clinical study and is the only study to the important APS cost Although several authors have for a as an to the more multidisciplinary APS have proposed an more use of Studies of of Acute Pain of health care an analysis of the of the with a and relevant outcome analysis of acute pain management is by the of a and outcome is valid to cost to of analgesia and the effect of perioperative regional analgesia on outcomes has not been If specialized techniques provide pain relief, the management of these techniques a dedicated APS at analyses that and outcome measures have been but studies APS have been analyses of postoperative pain management have to the of and nursing of stay in the and postoperative Studies different in a controlled be to an for the APS on the implementation of or to be a of APS and this the effects of an APS from the effects of the increased awareness of postoperative pain and/or in postoperative pain techniques by techniques and in surgical technique is difficult. Unfortunately, postoperative pain is a that awareness and to improve treatment, despite the of an APS However, the APS an to improve pain relief, although the structure and to be in the of improved pain relief and there to be quality criteria for the provided service from this and other reviews pain relief did not significantly improve postoperative with the of patient and Thus, postoperative morbidity and hospital stay are on including preoperative information, quality of analgesia, and existing programs for postoperative care and including for and discharge criteria to the potential for postoperative pain relief and for an APS to improve postoperative morbidity and hospital stay, programs clinical be in which postoperative pain relief is an program with and with discharge criteria Finally, future strategies should on the of the APS and techniques on outcome in specific as controlled clinical trials or in a is important for the future of because existing data a major in provided that the APS or other strategies are programs the of APSs may be because of the in health care and the for

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