Journal of Pediatric Ophthalmology and Strabismus

Original Article 

Postoperative Nausea and Vomiting and Phase I Post-anesthesia Recovery After Strabismus Operations

Kathleen M. Kratt, RN, CCRN; Erick D. Bothun, MD; Sree Chandralek Kruthiventi, MD; Erica R. Portner, RRT; Juraj Sprung, MD, PhD; Toby N. Weingarten, MD

Abstract

Purpose:

To ascertain postoperative nausea and vomiting (PONV) rates in adult patients after strabismus operations and assess causes for prolonged post-anesthesia recovery.

Methods:

This was a retrospective observational study of consecutive adult patients who underwent strabismus operations at one institution from January 1, 2010, to May 31, 2017. The anesthetic records were abstracted and PONV rates were ascertained. On the basis of the cohort's 75th percentile of anesthesia recovery duration, patients were categorized into goal recovery (lower three quartiles) and prolonged recovery (upper quartile). Multivariable logistic regression analyses were performed to assess associations between clinical characteristics and prolonged recovery.

Results:

A total of 794 adult patients who underwent strabismus surgery were identified. PONV was present in 31 (3.9%) patients. The median (interquartile range) post-anesthesia recovery was 45 minutes (range: 33 to 63 minutes). Prolonged recovery was associated with long-term benzodiazepine use (odds ratio [OR]: 3.07; 95% CI [confidence interval]: 1.23 to 7.80; P = .02). Patients with prolonged recovery had higher rates of PONV (15 [7.2%] vs 16 [2.7%], P = .007), oversedation (107 [51.4%] vs 226 [38.6%], P = .001), and postoperative analgesic administration (138 [66.4%] vs 222 [37.9%], P < .001). Inverse associations were found between desflurane and oversedation (OR: 0.63; 95% CI: 0.45 to 0.86; P = .004) and between acetaminophen administration and postoperative analgesic administration (OR: 0.57; 95% CI: 0.38 to 0.86; P = .007).

Conclusions:

Adult patients undergoing general anesthesia for strabismus surgery had a low PONV rate. However, the presence of PONV was associated with delayed recovery room discharge. Other factors associated with prolonged Phase I recovery were long-term benzodiazepine use and longer operations, which likely resulted in an increased need for anesthetic agents and therefore more intense postoperative sedation.

[J Pediatr Ophthalmol Strabismus. 2019;56(3):151–156.]

Abstract

Purpose:

To ascertain postoperative nausea and vomiting (PONV) rates in adult patients after strabismus operations and assess causes for prolonged post-anesthesia recovery.

Methods:

This was a retrospective observational study of consecutive adult patients who underwent strabismus operations at one institution from January 1, 2010, to May 31, 2017. The anesthetic records were abstracted and PONV rates were ascertained. On the basis of the cohort's 75th percentile of anesthesia recovery duration, patients were categorized into goal recovery (lower three quartiles) and prolonged recovery (upper quartile). Multivariable logistic regression analyses were performed to assess associations between clinical characteristics and prolonged recovery.

Results:

A total of 794 adult patients who underwent strabismus surgery were identified. PONV was present in 31 (3.9%) patients. The median (interquartile range) post-anesthesia recovery was 45 minutes (range: 33 to 63 minutes). Prolonged recovery was associated with long-term benzodiazepine use (odds ratio [OR]: 3.07; 95% CI [confidence interval]: 1.23 to 7.80; P = .02). Patients with prolonged recovery had higher rates of PONV (15 [7.2%] vs 16 [2.7%], P = .007), oversedation (107 [51.4%] vs 226 [38.6%], P = .001), and postoperative analgesic administration (138 [66.4%] vs 222 [37.9%], P < .001). Inverse associations were found between desflurane and oversedation (OR: 0.63; 95% CI: 0.45 to 0.86; P = .004) and between acetaminophen administration and postoperative analgesic administration (OR: 0.57; 95% CI: 0.38 to 0.86; P = .007).

Conclusions:

Adult patients undergoing general anesthesia for strabismus surgery had a low PONV rate. However, the presence of PONV was associated with delayed recovery room discharge. Other factors associated with prolonged Phase I recovery were long-term benzodiazepine use and longer operations, which likely resulted in an increased need for anesthetic agents and therefore more intense postoperative sedation.

[J Pediatr Ophthalmol Strabismus. 2019;56(3):151–156.]

Introduction

Efficient surgical practices rely on an effective interaction between the preoperative, intraoperative, and postoperative care areas to facilitate patients throughout.1 Inefficiencies of post-anesthesia care units (PACUs) related to prolonged patient recovery (termed Phase I post-anesthesia recovery) can create patient-flow bottlenecks and slow surgical schedules. Postoperative nausea and vomiting (PONV) is a well-known risk factor related to a delayed discharge from the PACU. Previously, the authors demonstrated that an anesthesia practice that emphasizes aggressive PONV prophylaxis may be associated with substantial improvements in PACU efficiency and increased patient satisfaction.2

Strabismus surgery has traditionally been reported to have high rates of PONV,3,4 and it has been recommended that patients who have this procedure also receive aggressive PONV prophylaxis.5 In the current study, we examined Phase I post-anesthesia recovery in adults undergoing strabismus operations. We tested the hypothesis that in our practice, which uses an aggressive prophyiactic anti-PONV regimen, PONV is low but is still a substantial factor for prolonged PACU stay. Our secondary aim was to examine the association between patient and procedural characteristics and delayed recovery following strabismus operations.

Patients and Methods

This study was approved by the local institutional review board. Consistent with local state law, all study participants provided authorization for the research use of their health records.

Study Design and Patient Selection

This retrospective study evaluated adults who underwent strabismus operations with general anesthesia care from January 1, 2010, to May 31, 2017, in a large academic institution. Patients who underwent strabismus operations in our hospital-based surgical practice and were transferred from the operating room to the PACU were included in this study, whereas patients who bypassed the PACU or whose operation was performed in our ambulatory surgical center were excluded.

The electronic health records of study participants were reviewed to determine rates of PONV and prolonged PACU stay. The entire cohort was divided into two groups based on the 75th percentile of the observed distribution for recovery room stay. Specifically, patients in the lowest three quartiles were categorized as goal recovery and patients in the upper quartile as prolonged recovery. We assessed patient and procedural characteristics and the potential associations with prolonged recovery using a multivariable model.

Anesthetic Management

Anesthetic care was based on a team-care model including an attending anesthesiologist and an in-room anesthesia provider (eg, certified nurse anesthetist). Based on our previous work, anesthetic management emphasized early Phase I post-anesthesia recovery with short-acting anesthetics and aggressive PONV prophylaxis.2 Typically, anesthesia was induced with propofol after the insertion of a laryngeal mask airway (and less frequently after endotracheal intubation). Anesthesia was maintained with desflurane or sevoflurane and fentanyl was the primary opioid.

In addition, non-opoid analgesics that were frequently used in the current study were acetaminophen and ketorlac (a non-steroidal anti-inflammatory drug) because our practice avoids the routine use of midazolam. Routine PONV prophylaxis included 4 mg dexamethasone at the beginning of anesthesia and 0.625 mg droperidol and 4 mg ondansetron at the end of the operation. For patients considered to be at a high risk for PONV, a propofol infusion was used or a scopolamine patch was applied (or both) preoperatively. However, compliance with this practice was not mandatory, and the attending anesthesiologists were free to alter the protocol as needed for individual circumstances.

PACU Clinical Practice

The PACU was staffed by registered nurses and a first- or second-year anesthesia resident, with the attending anesthesiologist immediately available. Discharge from Phase I post-anesthesia recovery was based on standard discharge criteria, goal pain scores, and control of PONV.6 For an added layer of safety, staff nurses continuously monitored patients for signs of respiratory depression.7 The period for patients to meet discharge criteria for Phase I recovery was recorded by nurses in the electronic anesthetic record. The time, regardless of the actual time when the patient was discharged, was collected for the analysis of duration of PACU stay.

Data Abstraction

Electronic health, surgical, and anesthetic records were abstracted using proprietary software.8 Preoperative variables included patient age, sex, body mass index, smoking status, history of or positive screen for obstructive sleep apnea,9 home use of opioids, benzodiazepines, or gabapentinoids (gabapentin or pregabalin), and the Charlson Comorbidity Index.10 Surgical records were reviewed for the number of muscles repaired, whether unilateral or bilateral surgery was performed, and the duration of surgery.

Anesthetic care records were reviewed for maintenance technique, analgesics, PONV prophylaxis, and Phase I recovery characteristics including PONV episodes (from the use of rescue anti-emetics or notation of its presence in nursing records), medications administered, and an occurrence of “respiratory-specific events” (as a proxy for respiratory depression or oversedation).7 The sedation level was assessed with the Richmond Agitation-Sedation Scale (RASS) and a score of less than −1 indicated oversedation.11 Intraoperative and postoperative opioids were converted to intravenous morphine equivalents according to published guidelines.12,13 The need for postoperative analgesics was defined by the administration of opioids, ketorolac, or acetaminophen during Phase I post-anesthesia recovery. Bronchospasm, hypotension, and hypertension were defined by the pharmacologic treatments of these complications. The duration of Phase I recovery was defined as the time from PACU admission to the time when the patient met Phase I discharge criteria, as noted in the electronic health record. This time was not affected by non-clinical delays in patient transfer from the PACU to Phase II recovery areas due to non-clinical delays for PACU discharge (ie, waiting for patient transport or a postoperative bed).

Statistical Analysis

Data are presented as mean ± standard deviation or median (interquartile range) for continuous variables and as number of patients (percentage) for categorical variables. The primary end point was prolonged Phase I post-anesthesia recovery (defined as recovery in the upper quartile of Phase I recovery duration). Postoperative events that could prolong anesthesia recovery (eg, PONV, oversedation, or additional need for analgesics) were characterized with descriptive statistics. A multivariable analysis was performed to assess the potential associations between a prolonged Phase I recovery and patient and perioperative characteristics. Secondary multivariable analyses were performed for postoperative events that could prolong anesthesia recovery and occurred at an adequate rate for further analysis. These analyses assessed the potential associations between those postoperative events and the same patient and perioperative characteristics used in the initial analysis. A two-tailed P value of less than .05 was considered statistically significant. Statistical analyses were performed with statistical software (JMP Pro version 13.0.0; SAS Institute, Inc., Cary, NC).

Results

During the study time frame, 794 adult patients underwent ambulatory strabismus operations at our main hospital. The median (interquartile range) duration of Phase I post-anesthesia recovery was 45 minutes (range: 33 to 63 minutes), with 586 (74%) patients meeting the goal recovery duration and 208 (26%) having prolonged recovery. The median (interquartile range) time was 39 minutes (range: 30 to 49 minutes) for patients with goal recovery and 80 minutes (range: 67 to 98 minutes) for those with prolonged recovery. Patient, procedural, and anesthetic characteristics of all patients are summarized in Table 1. Of all characteristics explored, only home use of benzodiazepines was associated with prolonged recovery (odds ratio [OR]: 3.07; 95% confidence interval [CI]: 1.23 to 7.80; P = .02). The Phase I post-anesthesia course between goal recovery and prolonged recovery groups is summarized in Table 2. Thirty-one patients had PONV (3.9 of 100 cases [95% CI: 2.8 to 5.5]). The rates of PONV and oversedation (RASS score of less than −1) were higher for patients with a prolonged recovery and a need for additional analgesics. No cases of serious morbidity or 30-day death were observed in this cohort.

Patient, Procedural, and Anesthetic Characteristics of Patients Undergoing Strabismus Surgery

Table 1:

Patient, Procedural, and Anesthetic Characteristics of Patients Undergoing Strabismus Surgery

Course of Phase I Post-anesthesia Recovery After Strabismus Surgery

Table 2:

Course of Phase I Post-anesthesia Recovery After Strabismus Surgery

We performed one additional post-hoc analysis. First, a multivariable analysis was done to assess variables associated with Phase I recovery oversedation. Oversedation in PACU was associated with longer operations (OR: 1.06; 95% CI: 1.01 to 1.10; P = .009 per 10 minutes of surgery) and the use of propofol infusion (OR: 1.50; 95% CI: 1.08 to 2.10]; P = .02). By comparison, use of desflurane was inversely associated with oversedation (OR: 0.63; 95% CI: 0.45 to 0.86; P = .004). Anesthetic administrations with propofol infusions took longer than those without (OR: 65; 95% CI: 42 to 106 minutes vs OR: 43; 95% CI: 28 to 64 minutes, respectively; P < .001). Second, a multivariable analysis was performed to assess variables associated with increased postoperative analgesic administration. The rate of postoperative analgesic administration decreased as patient age increased per decade of life (OR: 0.83; 95% CI: 0.73 to 0.95; P = .06) and preoperative use of acetaminophen (OR: 0.63; 95% CI: 0.42 to 0.94; P = .03). The rate also increased with the duration of surgery (OR: 1.05; 95% CI: 1.01 to 1.10; P = .02).

Discussion

The rate of PONV is low in our practice, which has an aggressive emphasis on PONV prophylaxis for patients undergoing strabismus operations. In the current study, long-term use of benzodiazepines was the only preoperative characteristic associated with prolonged anesthetic recovery. Prolonged Phase I post-anesthesia recovery was associated with increased rates of PONV, increased rates of postoperative oversedation, and an increased need for analgesic therapies in the recovery room for patients who underwent therapy for postoperative hypertension.

The overall PONV rate was much lower than traditionally cited rates following strabismus operations (3.7% vs 25% to 47%, respectively).3,4 The wide range is the result of studies on children undergoing strabismus operations who received one prophylactic PONV agent (ondansetron).3,4 Several reasons may account for the lower rate of PONV in our cohort. First, our study was limited to adult patients, who are known to have lower PONV rates than children.5 Second, our definition relied on charting medications and nursing documentation, which is less sensitive than prospectively collecting a patient's self-report on nausea level.14 Third, our practice uses an aggressive multimodal regimen for PONV prophylaxis2,15 rather than a single agent, which is consistent with current recommendations for multimodal anti-nausea prophylaxis.5

Large proportions of our patients with prolonged post-anesthesia recovery were either oversedated or required additional analgesic therapy. Post-hoc analyses of the two outcomes identified meaningful associations. Increased duration of surgery and use of propofol infusions were associated with increased postoperative sedation. However, propofol infusions were used more frequently for longer procedures and could indicate a prolonged operation, with both factors reflective of greater postoperative sedation. Unfortunately, our data do not allow us to account for the infused propofol doses to more precisely assess associations between propofol use and prolonged post-anesthetic recovery. Furthermore, the rate of postoperative sedation was lower for patients who received desflurane, which was consistent with our previous observations that desflurane use is superior to sevoflurane or isoflurane use for the speed of recovery.2 With regard to observation, the rate of administering analgesics may be reduced for patients who received acetaminophen preoperatively because it is in agreement with reports that acetaminophen provides an opioid-sparing effect following ophthalmologic procedures.16,17 A cost-effective analgesic, acetaminophen, was underused in the current study because only 18.8% of patients in our cohort received it. Further, the opioid-sparing effects of acetaminophen (and other non-opioid analgesic modalities) could have a beneficial reduction of PONV.

Limitations

The current study was limited by its retrospective research design. For example, PONV rates were lower than previous reports, which may reflect our retrospective means of ascertaining this complication rather than the means used in prospective trials. However, we believe that our methodology successfully accounted for all clinically meaningful episodes of PONV. The severity of pain was not different between the two groups. Nevertheless, analgesic administration was greater in the prolonged recovery group, and the design of our study cannot separate whether this outcome was due to more severe pain in this group or the greater analgesic requirement was merely a marker of longer recovery times (eg, due to oversedation or PONV). In our post-hoc analysis, hypertension was associated with longer recovery, which likely reflects our institution's guidelines that after receipt of certain anti-hypertensive drugs, patients must be observed with additional PACU monitoring before discharge. Although this cohort included approximately 800 patients, it is an inadequate size to assess the risk of rare but serious adverse events or mortality, especially because the surgical procedures were low risk. The observation that chronic use of benzodiazepines was associated with prolonged recovery time is consistent with our findings in larger surgical cohorts that use of medications with psychometric properties is associated with increased risk of adverse events, such as opioid-induced respiratory depression.18 Thus, it may be prudent to be conservative when discharging patients after ambulatory surgery.

Conclusions

We found low rates of PONV following strabismus surgery in our practice with an aggressive emphasis on PONV prophylaxis. Despite the low PONV rates, the presence of PONV was associated with delayed discharge from PACUs. Long-term benzodiazepine use was the only patient factor associated with prolonged Phase I post-anesthesia recovery. Other factors are procedural characteristics (eg, longer operations) that likely resulted in an increased need for anesthetics such as propofol and postoperative analgesics, resulting in a more profound sedation in the recovery room.

References

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Patient, Procedural, and Anesthetic Characteristics of Patients Undergoing Strabismus Surgery

CharacteristicsUnivariate AnalysisMultivariable Analysis


Prolonged Recoverya (n = 208)Goal Recoverya (n = 586)POdds Ratio (95% CI)P
Patient
Age, mean ± standard deviation, yb53.1 ± 17.852.9 ± 18.1.890.97 (0.84 to 1.13).71
  Male sex107 ± 51.4257 ± 43.9.061.37 (0.97 to 1.93).07
  Body mass index, mean ± standard deviation, kg/m2 b28.8 (6.9)27.9 (6.1).101.24 (0.94 to 1.62).12
  Smoker (current)31 (14.9)80 (13.7).641.05 (0.65 to 1.68).83
  Obstructive sleep apnea34 (16.3)83 (14.2).500.83 (0.50 to 1.35).45
  Charlson Comorbidity Index, median (IQR)2 (1 to 4)2 (1 to 4).551.04 (0.93 to 1.16).51
Home medication
  Opioids28 (13.5)52 (8.9).081.47 (0.80 to 2.65).21
  Benzodiazepines14 (6.7)13 (2.2).0063.07 (1.23 to 7.80).02
  Gabapentinoids7 (3.4)12 (2.0).300.78 (0.24 to 2.27).65
Procedure
  Surgical duration, mean ± standard deviation, minb75 ± 5466 ± 46.021.03 (0.99 to 1.08).19
  No. of muscles repaired.70
    178 (37.5)202 (34.5)Reference
    2100 (48.1)300 (51.2)1.24 (0.86 to 1.79).25
    > 231 (14.9)84 (14.3)1.44 (0.85 to 2.50).18
Anesthesia
  Desflurane68 (32.7)227 (38.7).110.73 (0.51 to 1.04).08
  Nitrous oxide72 (34.6)207 (35.3).871.01 (0.71 to 1.42).97
  Acetaminophen40 (19.2)109 (18.6).920.94 (0.60 to 1.45).78
  Ketorolac83 (39.9)240 (41.0).811.04 (0.74 to 1.47).82
  Midazolam38 (18.3)110 (18.8).920.90 (0.58 to 1.38).65
  Ketamine6 (2.9)19 (3.2)> .990.73 (0.25 to 1.85).55
  Remifentanil18 (8.7)43 (7.3).551.03 (0.53 to 1.97).90
  Triple antiemetic therapyc115 (55.3)342 (58.4).420.92 (0.64 to 1.31).66
  Propofol infusion121 (58.2)311 (53.1).221.21 (0.83 to 1.75).28
  Scopolamine10 (4.8)30 (5.1)> .991.08 (0.48 to 2.30).82
  Opioids, median (IQR), intravenous morphine equivalent mgb12.5 (7.6 to 19.4)10.0 (7.5 to 15.0).211.01 (0.78 to 1.32).92
  Intraoperative fluids (crystalloids), mean ± standard deviation, L0.67 ± 0.300.61 ± 0.24.0052.01 (0.96 to 4.26).07

Course of Phase I Post-anesthesia Recovery After Strabismus Surgery

OutcomeProlonged Recovery (n = 208)Goal Recovery (n = 586)P
Nausea and/or vomiting15 (7.2%)16 (2.7%).007
Oversedationa,b107 (51.4%)226 (38.6%).001
Analgesic administrationc138 (66.3%)222 (37.9%)< .001
Severe paind27 (13.0%)79 (13.5%).91
Hypotension0 (0.0%)1 (0.2%)> .99
Hypertension12 (5.8%)2 (0.3%)< .001
Bronchospasm4 (1.9%)3 (0.5%).08
Unplanned admissione1 (0.5%)1 (0.2%).46
Authors

From the Department of Anesthesiology and Perioperative Medicine (KMK, SCK, ERP, JS, TNW); and the Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota (EDB).

Supported by the Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota.

Dr. Weingarten is a consultant for Medtronic, chairman of the Clinical Endpoint Committee for the Prodigy Trial, and received research support from Respiratory Motion and unrestricted investigator-initiated grants from Merck & Co, Inc. and Baxter International, Inc. The remaining authors have no financial or proprietary interest in the materials presented herein.

Correspondence: Toby N. Weingarten, MD, Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN 55905. E-mail: weingarten.toby@mayo.edu

Received: November 08, 2018
Accepted: January 07, 2019

10.3928/01913913-20190208-03

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