Clinical Orthopaedics and Related Research®
Clin Orthop Relat Res DOI 10.1007/s11999-013-3336-5
A Publication of The Association of Bone and Joint Surgeons®
SYMPOSIUM: PERIOPERATIVE PAIN MANAGEMENT IN ORTHOPAEDIC SURGERY
Is Regional Anesthesia Associated With Reduced PACU Length of Stay? A Retrospective Analysis From a Tertiary Medical Center John M. Corey MD, Catherine M. Bulka MPH, Jesse M. Ehrenfeld MD, MPH
Ó The Association of Bone and Joint Surgeons1 2013
Abstract Background Postanesthesia care is a costly component of overall surgical care. In the ambulatory setting, regional anesthesia has been shown for multiple surgical procedures to either decrease postanesthesia care unit (PACU) length of stay (LOS) or completely bypass it altogether. This has not been demonstrated in a large hospital setting with a complex surgical case mix. Questions/purposes We therefore determined whether regional anesthesia was associated with a reduced PACU LOS among patients undergoing inpatient and outpatient surgery in a large tertiary-care teaching hospital. Secondary study questions included risk factors for longer PACU LOS and any possible interaction between regional and general anesthesia as it might have affected PACU LOS.
Each author certifies that he or she, or a member of his or her immediate family, has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request. Each author certifies that his or her institution approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research. J. M. Corey (&), C. M. Bulka, J. M. Ehrenfeld Department of Anesthesiology and Pain Medicine, Vanderbilt University Medical Center, 1301 Medical Center Drive #4648, Nashville, TN 37237, USA e-mail: [email protected]
Methods We performed a matched retrospective study on patients who had surgery at our institution and were admitted to the PACU immediately after leaving the operating room. We analyzed between January 1, 2005, and January 1, 2013, with one cohort receiving regional anesthesia, with or without general anesthesia, and the other receiving no regional anesthesia. We measured the association between regional anesthesia and time to successful PACU discharge using a Cox multivariate proportional-hazards model. Results After controlling for potentially confounding variables, including patient age, American Society of Anesthesiologists’ physical classification, and duration of surgery (using multivariate analysis), there was no difference in the time to successful PACU discharge between patients who received regional anesthesia and those who did not. However, when compared to those who received general anesthesia, regional anesthesia was associated with decreased PACU LOS. Further, there was significant effect modification between regional and general anesthesia; patients who received both regional and general were more likely to be successfully discharged faster from the PACU than patients who received only general anesthesia (hazard ratio = 1.50, 95% CI = 1.46– 1.55, p \ 0.001). Conclusions We demonstrated that independently, regional anesthesia is not associated with a reduced PACU LOS in an unselected population at a large tertiary-care hospital, but regional is favored when compared to general anesthesia. Whether the differences are clinically important, and in what procedures they are most pronounced, would be reasonable questions for future prospective comparative trials. Level of Evidence Level III, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.
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Clinical Orthopaedics and Related Research1
Introduction
Patients and Methods
The postanesthesia care unit (PACU) is an expensive and labor-intensive environment [4, 18, 19]. The evidence of benefit from regional anesthesia in decreasing PACU length of stay (LOS) or bypassing it completely in the ambulatory setting is well demonstrated. Patients receiving regional anesthesia for rotator cuff surgery versus general anesthesia were shown to bypass the PACU more often, report less pain, ambulate earlier, meet discharge criteria sooner, and be more satisfied with their care [7]. Similarly, patients undergoing inguinal hernia repair in the outpatient setting with paravertebral blocks compared to general anesthesia demonstrated higher PACU bypass rates, earlier ambulation, less nausea and vomiting, and reduced need for supplemental analgesics [6]. A meta-analysis performed by Liu et al. [14] in 2005 showed that peripheral regional anesthesia in the ambulatory setting was associated with decreased PACU use, nausea, and postoperative pain. For the inpatient setting, decreased PACU LOS associated with regional anesthesia has not been established. The majority of recent work concerning the benefits of regional anesthesia is related to their role in ‘‘fast track surgery’’ or ‘‘enhanced recovery’’ perioperative approaches for specific procedures and the impact on overall hospital LOS [3]. The most studied to date involves colorectal surgery, where use of thoracic epidural analgesia has been a key component in the enhanced recovery pathway [12]. A meta-analysis comparing enhanced recovery protocols versus standard care for elective colorectal surgery between 1995 and 2008 showed a mean hospital LOS reduction of 2.46 days with no change in readmission rate [5]. In Denmark, during the last 10 years, hospital LOS for primary hip and knee arthroplasty has declined from 10 to 11 days in 2000 to 4 days in 2009 [9], with regional anesthesia being an important aspect of care [10, 11]. Recently, Lunn et al. [15] specifically looked at PACU LOS after THA and TKA under spinal anesthesia and found that greater than 85% of patients under low-dose spinal anesthesia achieved predefined PACU discharge criteria in 15 minutes. Outside of that study, however, there has been little focus on time spent in the PACU. We therefore sought to determine whether regional anesthesia would be associated with a reduced PACU LOS in an unselected patient population undergoing both inpatient and outpatient surgery at our large tertiary-care medical center. We also investigated factors that have been identified in previous studies to have effects on PACU LOS (general anesthesia [4, 18], age [17], sex [2, 13], American Society of Anesthesiologists [ASA] class [13], and length of surgery [4, 17]), as well as the interaction between regional and general anesthesia as it affected PACU LOS.
This study was approved by the Vanderbilt University Institutional Review Board. This was a retrospective observational cohort study using the Perioperative Data Warehouse (PDW) of the Vanderbilt University Medical Center (VUMC). The PDW contains data from information systems at VUMC, including electronic medical record data and preoperative, intraoperative, and postoperative data. We identified 203,342 surgical cases that received anesthetic care at VUMC between January 1, 2005, and January 1, 2013, and were admitted to the PACU immediately after leaving the operating room. We excluded stays in the PACU of greater than 12 hours (n = 1232), since these were likely due to a downstream bed availability issue rather than the type of anesthesia the patient received. We used the Clinical Classifications Software (CCS) 2013 (Agency for Healthcare Research and Quality, Rockville, MD, USA) developed by the Healthcare Cost and Utilization Project [8] to group surgical procedures into a manageable number of clinically meaningful categories. We randomly selected one surgical case that did not receive regional anesthesia for every surgical case that received regional anesthesia, matched by CCS surgical procedure category. We only analyzed data from CCS categories that included at least 200 patients. We excluded patients who had surgical procedures that could not be matched. Patients who were missing data regarding PACU LOS (n = 309) and surgical procedure (n = 4436) were excluded from the analysis. Observation of patient time was censored if the patient returned to the operating room or went to the intensive care unit (ICU) after the PACU. The primary outcome was time to successful discharge from the PACU using standard Aldrete discharge criteria [1]. Of the 197,365 surgeries for which data were available and PACU LOS was less than 12 hours, we identified 19,338 patients who received regional anesthesia and 178,027 who did not (Fig. 1). Of these, we were able to match 15,308 surgeries that used regional anesthesia to 15,308 surgeries that did not, for a total of 30,616 surgeries comprised of 25,814 unique patients. Patients who did not receive regional anesthesia were more likely to receive general anesthesia, but 8267 patients in our cohort received both regional and general anesthesia (Table 1). Of the total 30,616 surgeries, 351 (1.2%) were censored because they returned to the operating room or were admitted to the ICU from the PACU. We abstracted the following information from the PDW: age, sex, race, ASA physical status classification, duration of surgery, procedure type (classified using the CCS grouper), use of regional anesthesia during surgery, use of
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Regional Anesthesia and PACU LOS
Fig. 1 A flowchart shows patient selection according to our study inclusion and exclusion criteria.
general anesthesia during surgery, LOS in the PACU, and location the patient was discharged to from the PACU. Patient demographics and preoperative and intraoperative clinical characteristics of the regional anesthesia and no regional anesthesia cohorts were compared using chisquare tests or Wilcoxon-Mann-Whitney tests as appropriate. Hazard ratios (HRs) were used to quantify the strength of covariate-outcome associations for the Cox model. Reported 95% CIs acknowledge uncertainty in all estimated associations. In addition to our main exposure of interest (regional anesthesia), we included additional covariates in the multivariate analysis based on their effect on PACU LOS in previous studies (general anesthesia [4, 18], age [17], sex [2, 13], ASA class [13], and length of surgery [4, 17]), as well as the interaction between regional and general anesthesia. Our Cox proportional-hazards model was stratified by the CCS grouper to account for matching by surgical procedure (Table 2). We selected the best model using backwards elimination. Because some patients were included more than once in our cohort due to multiple surgeries, we used the sandwich variance estimator to correct for clustering. The proportional-hazards assumption for the model was checked by examining plots of scaled Schoenfeld residuals and time. The overall C-index was
used to provide a measure of model discrimination [16]. All analyses were conducted using SAS1 Version 9.3 (SAS Institute, Inc, Cary, NC, USA). We considered p values of less than 0.05 significant.
Results After controlling for patient age, ASA class, duration of surgery, use of general anesthesia, and the interaction between general and regional anesthesia in the final multivariate Cox proportional-hazards model, there was no difference in the time to successful PACU discharge between the cohort that received regional anesthesia and the cohort that did not (HR = 0.97, 95% CI = 0.91–1.03, p = 0.332) (Table 3). However, those who received regional anesthesia were 78% more likely to be successfully discharged from the PACU compared to those who received general anesthesia (HR = 1.78, 95% CI = 1.71–1.84, p \ 0.001) (Table 4). Additionally, those who received regional anesthesia in conjunction with general anesthesia were 50% more likely to be successfully discharged from the PACU compared to those who received general anesthesia only (HR = 1.50, 95% CI = 1.46–1.55, p \ 0.001). With hazard ratios of greater than 1, this translates to shorter PACU LOS. The
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Clinical Orthopaedics and Related Research1
Corey et al. Table 1. Univariate and bivariate analyses Characteristic
All surgeries (n = 30,616)
Regional anesthesia (n = 15,308)
No regional anesthesia (n = 15,308)
p value
Demographics Age (years)* Male (number of patients)
51 (37–62)
52 (38–62)
50 (36–62)
15,178 (49.6%)
7667 (49.9%)
7511 (49.1%)
2 (1–2)
2 (2–3)
\ 0.001 0.0746
Preoperative ASA class*
2 (2–3)
\ 0.001
Intraoperative Length of surgery (minutes) Received general anesthesia (number of patients)
75 (36–121) 21,989 (71.8%)
72 (38–114) 8267 (54.0%)
78 (35–132) 13,722 (89.6%)
3409 (22.3%)
3115 (20.4%)
\ 0.001 \ 0.001
Postoperative \ 0.001
Location discharged to after PACU (number of patients) Phase 2 holding room Phase 3 extended recovery room
6524 (21.3%) 1208 (4.0%)
418 (2.7%)
790 (5.2%)
Floor
11,623 (37.8%)
4316 (28.2%)
7307 (47.7%)
Home
10,916 (35.7%)
Intensive care unit Operating room Private hire vehicle
7074 (46.2%)
3842 (25.1%)
330 (1.2%)
87 (0.6%)
243 (1.6%)
12 (0.0%)
3 (0.0%)
9 (0.1%)
3 (0.0%)
1 (0.0%)
2 (0.0%)
* Values are expressed as median, with interquartile range in parentheses; ASA = American Society of Anesthesiologists; PACU = postanesthesia care unit.
effects of patient age, ASA class, and length of surgery on time to successful PACU discharge, stratified by anesthetic technique, are displayed (Table 5). The Cox regression model had a chi-square test statistic of 3083.66 on six degrees of freedom (p \ 0.001). The model had an overall C-index of 0.78, indicating that the model had fair discrimination.
Discussion Prior studies have demonstrated a significant benefit of regional anesthesia on PACU LOS, sometimes even bypassing it successfully altogether. For the inpatient setting, the majority of studies concerning regional anesthesia have focused on overall hospital LOS, especially in the context of enhanced recovery pathways. Other factors have been identified that reduced PACU LOS in the hospital setting (general anesthesia [4, 18], age [17], sex [2, 13], ASA class [13], and length of surgery [4, 17]), but few data exist regarding regional anesthesia specifically. We therefore sought to determine whether regional anesthesia would be associated with a reduced PACU LOS in an unselected inpatient and outpatient surgery population at our large tertiary-care medical center. We also investigated factors that have been identified in previous studies to have
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effects on PACU LOS and the interaction between regional and general anesthesia as it affected PACU LOS. This study has several limitations. First are those particular to retrospective cohort studies in general. The dependence of data acquisition by others, even when standardized in an electronic medical record, is subject to individual selection and interpretation. Second, factors such as intraoperative medications, postoperative nausea and vomiting, and postoperative pain that may confound the association between regional anesthesia and time to successful PACU discharge were not accounted for, which may have introduced significant bias into the analysis. Third, surgical cases that were missing data on PACU LOS (n = 309) and surgical procedure (n = 4436) were excluded from the analyses. Additionally, surgical cases among patients who did not receive regional anesthesia and could not be matched to patients who did receive regional anesthesia were excluded. Missing data and the inability to match some surgical cases may have introduced selection bias into the study. Despite these exclusions, our sample size was still relatively large. Therefore, we may have identified statistically significant differences that are not necessarily clinically relevant. Another limitation was that there were important baseline differences between the study groups; those undergoing regional anesthesia were older, healthier, and had shorter surgical procedures. While our multivariate regression model sought to control for these
Regional Anesthesia and PACU LOS Table 2. Surgical procedure frequencies* Surgical procedure Amputation of lower extremity
Table 3. Multivariate Cox proportional-hazards regression results Number of patients 676 (2.21%)
b value
Explanatory variable
SE
p value
Received regional anesthesia
0.0326 0.0339
Received general anesthesia
0.6071 0.0324 \ 0.001
0.332
Arthroplasty knee
2212 (7.22%)
Received regional and general anesthesia
0.2003 0.0336 \ 0.001
Arthroplasty other than hip or knee
1080 (3.53%)
Age
0.0019 0.0004 \ 0.001
Arthroscopy
446 (1.46%)
ASA class
0.1636 0.0106 \ 0.001
Bunionectomy or repair of toe deformities
728 (2.38%)
Length of surgery
0.0034 0.0001 \ 0.001
Debridement of wound; infection or burn
568 (1.86%)
Model fit
Decompression peripheral nerve Division of joint capsule; ligament or cartilage
1682 (5.49%) 484 (1.58%)
Excision of semilunar cartilage of knee
1492 (4.87%)
Hip arthroplasty; total and partial
1388 (4.53%)
Hysterectomy; abdominal and vaginal
564 (1.84%)
Lens and cataract procedures
218 (0.71%)
Lobectomy or pneumonectomy
822 (2.68%)
Other OR therapeutic nervous system procedures
362 (1.18%)
Other OR therapeutic procedures on bone
1222 (3.99%)
Other OR therapeutic procedures on joints
4386 (14.33%)
Other OR therapeutic procedures on musculoskeletal system
338 (1.10%)
Other OR therapeutic procedures; female organs
426 (1.39%)
Other diagnostic procedures; female organs Other fracture and dislocation procedure Other hernia repair Other therapeutic procedures on muscles and tendons
280 (0.91%) 1720 (5.62%) 248 (0.81%) 4698 (15.34%)
Partial excision bone
996 (3.25%)
Repair of cystocele and rectocele; obliteration of vaginal vault
434 (1.42%)
Skin graft
320 (1.05%)
Treatment; fracture or dislocation of hip and femur
232 (0.76%)
Treatment; fracture or dislocation of lower extremity (other than hip or femur)
1260 (4.12%)
Treatment; fracture or dislocation of radius and ulna
1334 (4.36%)
* Classified by Clinical Classifications Software categories; OR = operating room.
factors, it is impossible to eliminate the possibility that they may have confounded the analysis at some level. Finally, there may have been differences among different regional anesthesia approaches, but we did not have reliable data on all of the possible regional techniques that might have been employed during the period of study, such as peripheral blocks, catheters, and varied multimodal approaches. When controlling for confounding variables, we found no difference in the time to successful PACU discharge between patients who received regional anesthesia and
Score chi-square (sandwich)
3083.66
p value
\ 0.001
Model prediction C-statistic
0.78
SE = standard error; ASA = American Society of Anesthesiologists.
Table 4. Hazard ratios for anesthetic techniques Explanatory variable
Hazard 95% CI ratio
p value
Regional anesthesia Compared to no regional anesthesia 0.97
0.91–1.03
Compared to general anesthesia
1.78
1.71–1.84 \ 0.001
0.332
Compared to regional and general anesthesia
1.18
1.14–1.23 \ 0.001
0.55
0.51–0.58 \ 0.001
General anesthesia Compared to no general anesthesia Compared to regional anesthesia
0.56
0.54–0.58 \ 0.001
Compared to regional and general anesthesia
0.67
0.65–0.69 \ 0.001
Compared to neither regional nor general anesthesia Compared to regional anesthesia
0.83
0.77–0.87 \ 0.001
0.85
0.81–0.88 \ 0.001
Compared to general anesthesia
1.50
1.46–1.55 \ 0.001
Compared to regional anesthesia
1.03
0.97–1.10
Compared to general anesthesia
1.83
1.72–1.95 \ 0.001
Compared to regional and general anesthesia
1.22
1.14–1.30 \ 0.001
Regional and general anesthesia
Neither regional nor general anesthesia 0.332
those who did not. However, we did find that regional anesthesia use was associated with shorter PACU LOS when compared to general anesthesia. Additionally, when regional anesthesia was used in conjunction with general anesthesia, PACU LOS was shorter than when general anesthesia was used alone. Multiple randomized controlled trials and a recent metaanalysis confirm that regional anesthesia in the ambulatory setting decreases PACU LOS [6, 7, 14]. One of the few articles to show a benefit of regional anesthesia concerning
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Clinical Orthopaedics and Related Research1
Corey et al. Table 5. Hazard ratios for age, ASA class, and length of surgery by anesthetic technique Characteristic
Regional , General
Regional+, General p value
Hazard ratio
95% CI
p value
Regional , General+
Regional+, General+
Hazard ratio
Hazard ratio
Hazard ratio
95% CI
95% CI
p value
95% CI
p value
35 years
0.94
0.91–0.97 \ 0.001 0.91
0.84–0.97
0.008 0.51
0.47–0.55 \ 0.001 0.77
0.71–0.82 \ 0.001
50 years 65 years
0.91 0.88
0.87–0.95 \ 0.001 0.88 0.84–0.94 \ 0.001 0.86
0.81–0.95 0.002 0.50 0.78–0.93 \ 0.001 0.48
0.46–0.54 \ 0.001 0.75 0.44–0.53 \ 0.001 0.72
0.69–0.81 \ 0.001 0.66–0.79 \ 0.001
1
0.85
0.83–0.87 \ 0.001 0.82
0.77–0.88 \ 0.001 0.46
0.43–0.49 \ 0.001 0.70
0.65–0.75 \ 0.001
2
0.72
0.69–0.75 \ 0.001 0.70
0.64–0.76 \ 0.001 0.39
0.36–0.42 \ 0.001 0.59
0.55–0.64 \ 0.001
3
0.61
0.58–0.65 \ 0.001 0.59
0.54–0.65 \ 0.001 0.33
0.31–0.36 \ 0.001 0.50
0.46–0.55 \ 0.001
4
0.52
0.48–0.56 \ 0.001 0.50
0.45–0.56 \ 0.001 0.28
0.26–0.31 \ 0.001 0.43
0.38–0.47 \ 0.001
5
0.44
0.40–0.49 \ 0.001 0.43
0.38–0.48 \ 0.001 0.24
0.21–0.27 \ 0.001 0.36
0.32–0.41 \ 0.001
Age
ASA class
Length of surgery 30 minutes
0.90
0.90–0.91 \ 0.001 0.88
0.82–0.94 \ 0.001 0.49
0.46–0.52 \ 0.001 0.74
0.69–0.79 \ 0.001
60 minutes
0.82
0.81–0.83 \ 0.001 0.79
0.74–0.85 \ 0.001 0.45
0.42–0.47 \ 0.001 0.67
0.63–0.71 \ 0.001
120 minutes 0.67
0.65–0.68 \ 0.001 0.65
0.60–0.69 \ 0.001 0.36
0.34–0.39 \ 0.001 0.55
0.51–0.59 \ 0.001
ASA = American Society of Anesthesiologists.
PACU LOS in a large tertiary-care hospital demonstrated a decrease in LOS for 20% of the 340 patients receiving regional anesthetic [18]. The average PACU time was 71 minutes for the entire cohort versus 47 minutes for the patients with a regional technique (odds ratio = 3.980, 95% CI = 1.909–8.297, p \ 0.001). Interestingly, that study’s main outcome was to examine medically appropriate PACU LOS versus actual PACU LOS and they demonstrated, in 68 of the 340 patients studied, the discharge was delayed due to logistic reasons rather than medical necessity. Along the same lines, in the Danish prospective observational study by Lunn et al. [15], they demonstrated, although an impressive 85% of 163 patients undergoing THA or TKA met discharge criteria within 15 minutes, actual discharge time was greater due to workload of transportation or nursing personnel. Also, consistent with the theme of enhanced recovery methodology, in that study, their protocols were standardized, with the patients receiving the same multimodal preoperative medications, intraoperative technique and doses, and adherence to modified PACU discharge criteria specific for these procedures. Thus, the anesthetic technique may simply be an important component of an even more important established process. We found that the effect of regional anesthesia differed depending on whether it was used with or without general anesthesia. If regional anesthesia was used without general anesthesia, it is likely that some patients received monitored anesthesia care (MAC) as well. Additionally, there are some cases that start with the use of MAC only and then require the addition of regional and/or general techniques. Thus, the unmeasured effect of MAC may have
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confounded the association between regional anesthesia and time to successful discharge. Further, it is possible that those who received regional anesthesia had similar but less extensive surgical procedures than those who did not receive regional anesthesia, which may have also confounded the effect of regional anesthesia on time to successful discharge from the PACU. Our study showed there was no difference in time to successful PACU discharge between patients who received regional anesthesia and those who did not. However, we also demonstrated that regional anesthesia, when used with or without general anesthesia, is associated with reduced PACU LOS when compared to general anesthesia. To understand whether there is in fact a benefit of regional anesthesia on hospital efficiency measures, prospective trials are still needed.
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Regional Anesthesia and PACU LOS 6. Hadzic A, Kerimoglu B, Loreio D, Karaca PE, Claudio RE, Yufa M, Wedderburn R, Santos AC, Thys DM. Paravertebral blocks provide superior same-day recovery over general anesthesia for patients undergoing inguinal hernia repair. Anesth Analg. 2006;102:1076–1081. 7. Hadzic A, Williams BA, Karaca PE, Hobeika P, Unis G, Dermksian J, Yufa M, Thys DM, Santos AC. For outpatient rotator cuff surgery, nerve block anesthesia provides superior same-day recovery over general anesthesia. Anesthesiology. 2005;102:1001–1007. 8. Healthcare Cost and Utilization Project (HCUP). HCUP Clinical Classifications Software (CCS) for ICD-9-CM, 2006–2009. Available at: www.hcup-us.ahrq.gov/toolssoftware/ccs/ccs.jsp. Accessed May 1, 2013. 9. Husted H, Jensen CM, Solgaard S, Kehlet H. Reduced length of stay following hip and knee arthroplasty in Denmark 2000–2009: from research to implementation. Arch Orthop Trauma Surg. 2012;132:101–104. 10. Ilfeld BM, Ball ST, Gearen PF, Le LT, Mariano ER, Vandenborne K, Duncan PW, Sessler DI, Enneking FK, Shuster JJ, Theriaque DW, Meyer RS. Ambulatory continuous posterior lumbar plexus nerve blocks after hip arthroplasty: a dual-center, randomized, triple-masked, placebo-controlled trial. Anesthesiology. 2008;109:491–501. 11. Ilfeld BM, Le LT, Meyer RS, Mariano ER, Vandenborne K, Duncan PW, Sessler DI, Enneking FK, Shuster JJ, Theriaque DW, Berry LF, Spadoni EH, Gearen P. Ambulatory continuous femoral nerve blocks decrease time to discharge readiness after tricompartment total knee arthroplasty: a randomized, triple-masked, placebo-controlled study. Anesthesiology. 2008;108:703–713. 12. Lassen K, Soop M, Nygren J, Cox PB, Hendry PO, Spies C, von Meyenfeldt MF, Fearon KC, Revhaug A, Norderval S, Ljungqvist
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Clin Orthop Relat Res DOI 10.1007/s11999-013-3336-5
A Publication of The Association of Bone and Joint Surgeons®
SYMPOSIUM: PERIOPERATIVE PAIN MANAGEMENT IN ORTHOPAEDIC SURGERY
Is Regional Anesthesia Associated With Reduced PACU Length of Stay? A Retrospective Analysis From a Tertiary Medical Center John M. Corey MD, Catherine M. Bulka MPH, Jesse M. Ehrenfeld MD, MPH
Ó The Association of Bone and Joint Surgeons1 2013
Abstract Background Postanesthesia care is a costly component of overall surgical care. In the ambulatory setting, regional anesthesia has been shown for multiple surgical procedures to either decrease postanesthesia care unit (PACU) length of stay (LOS) or completely bypass it altogether. This has not been demonstrated in a large hospital setting with a complex surgical case mix. Questions/purposes We therefore determined whether regional anesthesia was associated with a reduced PACU LOS among patients undergoing inpatient and outpatient surgery in a large tertiary-care teaching hospital. Secondary study questions included risk factors for longer PACU LOS and any possible interaction between regional and general anesthesia as it might have affected PACU LOS.
Each author certifies that he or she, or a member of his or her immediate family, has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request. Each author certifies that his or her institution approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research. J. M. Corey (&), C. M. Bulka, J. M. Ehrenfeld Department of Anesthesiology and Pain Medicine, Vanderbilt University Medical Center, 1301 Medical Center Drive #4648, Nashville, TN 37237, USA e-mail: [email protected]
Methods We performed a matched retrospective study on patients who had surgery at our institution and were admitted to the PACU immediately after leaving the operating room. We analyzed between January 1, 2005, and January 1, 2013, with one cohort receiving regional anesthesia, with or without general anesthesia, and the other receiving no regional anesthesia. We measured the association between regional anesthesia and time to successful PACU discharge using a Cox multivariate proportional-hazards model. Results After controlling for potentially confounding variables, including patient age, American Society of Anesthesiologists’ physical classification, and duration of surgery (using multivariate analysis), there was no difference in the time to successful PACU discharge between patients who received regional anesthesia and those who did not. However, when compared to those who received general anesthesia, regional anesthesia was associated with decreased PACU LOS. Further, there was significant effect modification between regional and general anesthesia; patients who received both regional and general were more likely to be successfully discharged faster from the PACU than patients who received only general anesthesia (hazard ratio = 1.50, 95% CI = 1.46– 1.55, p \ 0.001). Conclusions We demonstrated that independently, regional anesthesia is not associated with a reduced PACU LOS in an unselected population at a large tertiary-care hospital, but regional is favored when compared to general anesthesia. Whether the differences are clinically important, and in what procedures they are most pronounced, would be reasonable questions for future prospective comparative trials. Level of Evidence Level III, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.
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Introduction
Patients and Methods
The postanesthesia care unit (PACU) is an expensive and labor-intensive environment [4, 18, 19]. The evidence of benefit from regional anesthesia in decreasing PACU length of stay (LOS) or bypassing it completely in the ambulatory setting is well demonstrated. Patients receiving regional anesthesia for rotator cuff surgery versus general anesthesia were shown to bypass the PACU more often, report less pain, ambulate earlier, meet discharge criteria sooner, and be more satisfied with their care [7]. Similarly, patients undergoing inguinal hernia repair in the outpatient setting with paravertebral blocks compared to general anesthesia demonstrated higher PACU bypass rates, earlier ambulation, less nausea and vomiting, and reduced need for supplemental analgesics [6]. A meta-analysis performed by Liu et al. [14] in 2005 showed that peripheral regional anesthesia in the ambulatory setting was associated with decreased PACU use, nausea, and postoperative pain. For the inpatient setting, decreased PACU LOS associated with regional anesthesia has not been established. The majority of recent work concerning the benefits of regional anesthesia is related to their role in ‘‘fast track surgery’’ or ‘‘enhanced recovery’’ perioperative approaches for specific procedures and the impact on overall hospital LOS [3]. The most studied to date involves colorectal surgery, where use of thoracic epidural analgesia has been a key component in the enhanced recovery pathway [12]. A meta-analysis comparing enhanced recovery protocols versus standard care for elective colorectal surgery between 1995 and 2008 showed a mean hospital LOS reduction of 2.46 days with no change in readmission rate [5]. In Denmark, during the last 10 years, hospital LOS for primary hip and knee arthroplasty has declined from 10 to 11 days in 2000 to 4 days in 2009 [9], with regional anesthesia being an important aspect of care [10, 11]. Recently, Lunn et al. [15] specifically looked at PACU LOS after THA and TKA under spinal anesthesia and found that greater than 85% of patients under low-dose spinal anesthesia achieved predefined PACU discharge criteria in 15 minutes. Outside of that study, however, there has been little focus on time spent in the PACU. We therefore sought to determine whether regional anesthesia would be associated with a reduced PACU LOS in an unselected patient population undergoing both inpatient and outpatient surgery at our large tertiary-care medical center. We also investigated factors that have been identified in previous studies to have effects on PACU LOS (general anesthesia [4, 18], age [17], sex [2, 13], American Society of Anesthesiologists [ASA] class [13], and length of surgery [4, 17]), as well as the interaction between regional and general anesthesia as it affected PACU LOS.
This study was approved by the Vanderbilt University Institutional Review Board. This was a retrospective observational cohort study using the Perioperative Data Warehouse (PDW) of the Vanderbilt University Medical Center (VUMC). The PDW contains data from information systems at VUMC, including electronic medical record data and preoperative, intraoperative, and postoperative data. We identified 203,342 surgical cases that received anesthetic care at VUMC between January 1, 2005, and January 1, 2013, and were admitted to the PACU immediately after leaving the operating room. We excluded stays in the PACU of greater than 12 hours (n = 1232), since these were likely due to a downstream bed availability issue rather than the type of anesthesia the patient received. We used the Clinical Classifications Software (CCS) 2013 (Agency for Healthcare Research and Quality, Rockville, MD, USA) developed by the Healthcare Cost and Utilization Project [8] to group surgical procedures into a manageable number of clinically meaningful categories. We randomly selected one surgical case that did not receive regional anesthesia for every surgical case that received regional anesthesia, matched by CCS surgical procedure category. We only analyzed data from CCS categories that included at least 200 patients. We excluded patients who had surgical procedures that could not be matched. Patients who were missing data regarding PACU LOS (n = 309) and surgical procedure (n = 4436) were excluded from the analysis. Observation of patient time was censored if the patient returned to the operating room or went to the intensive care unit (ICU) after the PACU. The primary outcome was time to successful discharge from the PACU using standard Aldrete discharge criteria [1]. Of the 197,365 surgeries for which data were available and PACU LOS was less than 12 hours, we identified 19,338 patients who received regional anesthesia and 178,027 who did not (Fig. 1). Of these, we were able to match 15,308 surgeries that used regional anesthesia to 15,308 surgeries that did not, for a total of 30,616 surgeries comprised of 25,814 unique patients. Patients who did not receive regional anesthesia were more likely to receive general anesthesia, but 8267 patients in our cohort received both regional and general anesthesia (Table 1). Of the total 30,616 surgeries, 351 (1.2%) were censored because they returned to the operating room or were admitted to the ICU from the PACU. We abstracted the following information from the PDW: age, sex, race, ASA physical status classification, duration of surgery, procedure type (classified using the CCS grouper), use of regional anesthesia during surgery, use of
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Regional Anesthesia and PACU LOS
Fig. 1 A flowchart shows patient selection according to our study inclusion and exclusion criteria.
general anesthesia during surgery, LOS in the PACU, and location the patient was discharged to from the PACU. Patient demographics and preoperative and intraoperative clinical characteristics of the regional anesthesia and no regional anesthesia cohorts were compared using chisquare tests or Wilcoxon-Mann-Whitney tests as appropriate. Hazard ratios (HRs) were used to quantify the strength of covariate-outcome associations for the Cox model. Reported 95% CIs acknowledge uncertainty in all estimated associations. In addition to our main exposure of interest (regional anesthesia), we included additional covariates in the multivariate analysis based on their effect on PACU LOS in previous studies (general anesthesia [4, 18], age [17], sex [2, 13], ASA class [13], and length of surgery [4, 17]), as well as the interaction between regional and general anesthesia. Our Cox proportional-hazards model was stratified by the CCS grouper to account for matching by surgical procedure (Table 2). We selected the best model using backwards elimination. Because some patients were included more than once in our cohort due to multiple surgeries, we used the sandwich variance estimator to correct for clustering. The proportional-hazards assumption for the model was checked by examining plots of scaled Schoenfeld residuals and time. The overall C-index was
used to provide a measure of model discrimination [16]. All analyses were conducted using SAS1 Version 9.3 (SAS Institute, Inc, Cary, NC, USA). We considered p values of less than 0.05 significant.
Results After controlling for patient age, ASA class, duration of surgery, use of general anesthesia, and the interaction between general and regional anesthesia in the final multivariate Cox proportional-hazards model, there was no difference in the time to successful PACU discharge between the cohort that received regional anesthesia and the cohort that did not (HR = 0.97, 95% CI = 0.91–1.03, p = 0.332) (Table 3). However, those who received regional anesthesia were 78% more likely to be successfully discharged from the PACU compared to those who received general anesthesia (HR = 1.78, 95% CI = 1.71–1.84, p \ 0.001) (Table 4). Additionally, those who received regional anesthesia in conjunction with general anesthesia were 50% more likely to be successfully discharged from the PACU compared to those who received general anesthesia only (HR = 1.50, 95% CI = 1.46–1.55, p \ 0.001). With hazard ratios of greater than 1, this translates to shorter PACU LOS. The
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Corey et al. Table 1. Univariate and bivariate analyses Characteristic
All surgeries (n = 30,616)
Regional anesthesia (n = 15,308)
No regional anesthesia (n = 15,308)
p value
Demographics Age (years)* Male (number of patients)
51 (37–62)
52 (38–62)
50 (36–62)
15,178 (49.6%)
7667 (49.9%)
7511 (49.1%)
2 (1–2)
2 (2–3)
\ 0.001 0.0746
Preoperative ASA class*
2 (2–3)
\ 0.001
Intraoperative Length of surgery (minutes) Received general anesthesia (number of patients)
75 (36–121) 21,989 (71.8%)
72 (38–114) 8267 (54.0%)
78 (35–132) 13,722 (89.6%)
3409 (22.3%)
3115 (20.4%)
\ 0.001 \ 0.001
Postoperative \ 0.001
Location discharged to after PACU (number of patients) Phase 2 holding room Phase 3 extended recovery room
6524 (21.3%) 1208 (4.0%)
418 (2.7%)
790 (5.2%)
Floor
11,623 (37.8%)
4316 (28.2%)
7307 (47.7%)
Home
10,916 (35.7%)
Intensive care unit Operating room Private hire vehicle
7074 (46.2%)
3842 (25.1%)
330 (1.2%)
87 (0.6%)
243 (1.6%)
12 (0.0%)
3 (0.0%)
9 (0.1%)
3 (0.0%)
1 (0.0%)
2 (0.0%)
* Values are expressed as median, with interquartile range in parentheses; ASA = American Society of Anesthesiologists; PACU = postanesthesia care unit.
effects of patient age, ASA class, and length of surgery on time to successful PACU discharge, stratified by anesthetic technique, are displayed (Table 5). The Cox regression model had a chi-square test statistic of 3083.66 on six degrees of freedom (p \ 0.001). The model had an overall C-index of 0.78, indicating that the model had fair discrimination.
Discussion Prior studies have demonstrated a significant benefit of regional anesthesia on PACU LOS, sometimes even bypassing it successfully altogether. For the inpatient setting, the majority of studies concerning regional anesthesia have focused on overall hospital LOS, especially in the context of enhanced recovery pathways. Other factors have been identified that reduced PACU LOS in the hospital setting (general anesthesia [4, 18], age [17], sex [2, 13], ASA class [13], and length of surgery [4, 17]), but few data exist regarding regional anesthesia specifically. We therefore sought to determine whether regional anesthesia would be associated with a reduced PACU LOS in an unselected inpatient and outpatient surgery population at our large tertiary-care medical center. We also investigated factors that have been identified in previous studies to have
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effects on PACU LOS and the interaction between regional and general anesthesia as it affected PACU LOS. This study has several limitations. First are those particular to retrospective cohort studies in general. The dependence of data acquisition by others, even when standardized in an electronic medical record, is subject to individual selection and interpretation. Second, factors such as intraoperative medications, postoperative nausea and vomiting, and postoperative pain that may confound the association between regional anesthesia and time to successful PACU discharge were not accounted for, which may have introduced significant bias into the analysis. Third, surgical cases that were missing data on PACU LOS (n = 309) and surgical procedure (n = 4436) were excluded from the analyses. Additionally, surgical cases among patients who did not receive regional anesthesia and could not be matched to patients who did receive regional anesthesia were excluded. Missing data and the inability to match some surgical cases may have introduced selection bias into the study. Despite these exclusions, our sample size was still relatively large. Therefore, we may have identified statistically significant differences that are not necessarily clinically relevant. Another limitation was that there were important baseline differences between the study groups; those undergoing regional anesthesia were older, healthier, and had shorter surgical procedures. While our multivariate regression model sought to control for these
Regional Anesthesia and PACU LOS Table 2. Surgical procedure frequencies* Surgical procedure Amputation of lower extremity
Table 3. Multivariate Cox proportional-hazards regression results Number of patients 676 (2.21%)
b value
Explanatory variable
SE
p value
Received regional anesthesia
0.0326 0.0339
Received general anesthesia
0.6071 0.0324 \ 0.001
0.332
Arthroplasty knee
2212 (7.22%)
Received regional and general anesthesia
0.2003 0.0336 \ 0.001
Arthroplasty other than hip or knee
1080 (3.53%)
Age
0.0019 0.0004 \ 0.001
Arthroscopy
446 (1.46%)
ASA class
0.1636 0.0106 \ 0.001
Bunionectomy or repair of toe deformities
728 (2.38%)
Length of surgery
0.0034 0.0001 \ 0.001
Debridement of wound; infection or burn
568 (1.86%)
Model fit
Decompression peripheral nerve Division of joint capsule; ligament or cartilage
1682 (5.49%) 484 (1.58%)
Excision of semilunar cartilage of knee
1492 (4.87%)
Hip arthroplasty; total and partial
1388 (4.53%)
Hysterectomy; abdominal and vaginal
564 (1.84%)
Lens and cataract procedures
218 (0.71%)
Lobectomy or pneumonectomy
822 (2.68%)
Other OR therapeutic nervous system procedures
362 (1.18%)
Other OR therapeutic procedures on bone
1222 (3.99%)
Other OR therapeutic procedures on joints
4386 (14.33%)
Other OR therapeutic procedures on musculoskeletal system
338 (1.10%)
Other OR therapeutic procedures; female organs
426 (1.39%)
Other diagnostic procedures; female organs Other fracture and dislocation procedure Other hernia repair Other therapeutic procedures on muscles and tendons
280 (0.91%) 1720 (5.62%) 248 (0.81%) 4698 (15.34%)
Partial excision bone
996 (3.25%)
Repair of cystocele and rectocele; obliteration of vaginal vault
434 (1.42%)
Skin graft
320 (1.05%)
Treatment; fracture or dislocation of hip and femur
232 (0.76%)
Treatment; fracture or dislocation of lower extremity (other than hip or femur)
1260 (4.12%)
Treatment; fracture or dislocation of radius and ulna
1334 (4.36%)
* Classified by Clinical Classifications Software categories; OR = operating room.
factors, it is impossible to eliminate the possibility that they may have confounded the analysis at some level. Finally, there may have been differences among different regional anesthesia approaches, but we did not have reliable data on all of the possible regional techniques that might have been employed during the period of study, such as peripheral blocks, catheters, and varied multimodal approaches. When controlling for confounding variables, we found no difference in the time to successful PACU discharge between patients who received regional anesthesia and
Score chi-square (sandwich)
3083.66
p value
\ 0.001
Model prediction C-statistic
0.78
SE = standard error; ASA = American Society of Anesthesiologists.
Table 4. Hazard ratios for anesthetic techniques Explanatory variable
Hazard 95% CI ratio
p value
Regional anesthesia Compared to no regional anesthesia 0.97
0.91–1.03
Compared to general anesthesia
1.78
1.71–1.84 \ 0.001
0.332
Compared to regional and general anesthesia
1.18
1.14–1.23 \ 0.001
0.55
0.51–0.58 \ 0.001
General anesthesia Compared to no general anesthesia Compared to regional anesthesia
0.56
0.54–0.58 \ 0.001
Compared to regional and general anesthesia
0.67
0.65–0.69 \ 0.001
Compared to neither regional nor general anesthesia Compared to regional anesthesia
0.83
0.77–0.87 \ 0.001
0.85
0.81–0.88 \ 0.001
Compared to general anesthesia
1.50
1.46–1.55 \ 0.001
Compared to regional anesthesia
1.03
0.97–1.10
Compared to general anesthesia
1.83
1.72–1.95 \ 0.001
Compared to regional and general anesthesia
1.22
1.14–1.30 \ 0.001
Regional and general anesthesia
Neither regional nor general anesthesia 0.332
those who did not. However, we did find that regional anesthesia use was associated with shorter PACU LOS when compared to general anesthesia. Additionally, when regional anesthesia was used in conjunction with general anesthesia, PACU LOS was shorter than when general anesthesia was used alone. Multiple randomized controlled trials and a recent metaanalysis confirm that regional anesthesia in the ambulatory setting decreases PACU LOS [6, 7, 14]. One of the few articles to show a benefit of regional anesthesia concerning
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Corey et al. Table 5. Hazard ratios for age, ASA class, and length of surgery by anesthetic technique Characteristic
Regional , General
Regional+, General p value
Hazard ratio
95% CI
p value
Regional , General+
Regional+, General+
Hazard ratio
Hazard ratio
Hazard ratio
95% CI
95% CI
p value
95% CI
p value
35 years
0.94
0.91–0.97 \ 0.001 0.91
0.84–0.97
0.008 0.51
0.47–0.55 \ 0.001 0.77
0.71–0.82 \ 0.001
50 years 65 years
0.91 0.88
0.87–0.95 \ 0.001 0.88 0.84–0.94 \ 0.001 0.86
0.81–0.95 0.002 0.50 0.78–0.93 \ 0.001 0.48
0.46–0.54 \ 0.001 0.75 0.44–0.53 \ 0.001 0.72
0.69–0.81 \ 0.001 0.66–0.79 \ 0.001
1
0.85
0.83–0.87 \ 0.001 0.82
0.77–0.88 \ 0.001 0.46
0.43–0.49 \ 0.001 0.70
0.65–0.75 \ 0.001
2
0.72
0.69–0.75 \ 0.001 0.70
0.64–0.76 \ 0.001 0.39
0.36–0.42 \ 0.001 0.59
0.55–0.64 \ 0.001
3
0.61
0.58–0.65 \ 0.001 0.59
0.54–0.65 \ 0.001 0.33
0.31–0.36 \ 0.001 0.50
0.46–0.55 \ 0.001
4
0.52
0.48–0.56 \ 0.001 0.50
0.45–0.56 \ 0.001 0.28
0.26–0.31 \ 0.001 0.43
0.38–0.47 \ 0.001
5
0.44
0.40–0.49 \ 0.001 0.43
0.38–0.48 \ 0.001 0.24
0.21–0.27 \ 0.001 0.36
0.32–0.41 \ 0.001
Age
ASA class
Length of surgery 30 minutes
0.90
0.90–0.91 \ 0.001 0.88
0.82–0.94 \ 0.001 0.49
0.46–0.52 \ 0.001 0.74
0.69–0.79 \ 0.001
60 minutes
0.82
0.81–0.83 \ 0.001 0.79
0.74–0.85 \ 0.001 0.45
0.42–0.47 \ 0.001 0.67
0.63–0.71 \ 0.001
120 minutes 0.67
0.65–0.68 \ 0.001 0.65
0.60–0.69 \ 0.001 0.36
0.34–0.39 \ 0.001 0.55
0.51–0.59 \ 0.001
ASA = American Society of Anesthesiologists.
PACU LOS in a large tertiary-care hospital demonstrated a decrease in LOS for 20% of the 340 patients receiving regional anesthetic [18]. The average PACU time was 71 minutes for the entire cohort versus 47 minutes for the patients with a regional technique (odds ratio = 3.980, 95% CI = 1.909–8.297, p \ 0.001). Interestingly, that study’s main outcome was to examine medically appropriate PACU LOS versus actual PACU LOS and they demonstrated, in 68 of the 340 patients studied, the discharge was delayed due to logistic reasons rather than medical necessity. Along the same lines, in the Danish prospective observational study by Lunn et al. [15], they demonstrated, although an impressive 85% of 163 patients undergoing THA or TKA met discharge criteria within 15 minutes, actual discharge time was greater due to workload of transportation or nursing personnel. Also, consistent with the theme of enhanced recovery methodology, in that study, their protocols were standardized, with the patients receiving the same multimodal preoperative medications, intraoperative technique and doses, and adherence to modified PACU discharge criteria specific for these procedures. Thus, the anesthetic technique may simply be an important component of an even more important established process. We found that the effect of regional anesthesia differed depending on whether it was used with or without general anesthesia. If regional anesthesia was used without general anesthesia, it is likely that some patients received monitored anesthesia care (MAC) as well. Additionally, there are some cases that start with the use of MAC only and then require the addition of regional and/or general techniques. Thus, the unmeasured effect of MAC may have
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confounded the association between regional anesthesia and time to successful discharge. Further, it is possible that those who received regional anesthesia had similar but less extensive surgical procedures than those who did not receive regional anesthesia, which may have also confounded the effect of regional anesthesia on time to successful discharge from the PACU. Our study showed there was no difference in time to successful PACU discharge between patients who received regional anesthesia and those who did not. However, we also demonstrated that regional anesthesia, when used with or without general anesthesia, is associated with reduced PACU LOS when compared to general anesthesia. To understand whether there is in fact a benefit of regional anesthesia on hospital efficiency measures, prospective trials are still needed.
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