Definitions of "respiratory depression" with intrathecal morphine postoperative analgesia: a review of the literature

Role of continuous pulse oximetry and capnography monitoring in the prevention of postoperative respiratory failure, postoperative opioid-induced respiratory depression and adverse outcomes on hospital wards: A systematic review and meta-analysis

OBJECTIVE

The current standards of postoperative respiratory monitoring on medical-surgical floors involve spot-pulse oximetry checks every 4-8 h, which can miss the opportunity to detect prolonged hypoxia and acute hypercapnia. Continuous respiratory monitoring can recognize acute respiratory depression episodes; however, the existing evidence is limited. We sought to review the current evidence on the effectiveness of continuous pulse oximetry (CPOX) with and without capnography versus routine monitoring and their effectiveness for detecting postoperative respiratory failure, opioid-induced respiratory depression, and preventing downstream adverse events.

METHODS

We performed a systematic literature search on Ovid Medline, Embase, and Cochrane Library databases for articles published between 1990 and April 2023. The study protocol was registered in Prospero (ID: 439467), and PRISMA guidelines were followed. The NIH quality assessment tool was used to assess the quality of the studies. Pooled analysis was conducted using the software R version 4.1.1 and the package meta. The stability of the results was assessed using sensitivity analysis.

DESIGN

Systematic Review and Meta-Analysis.

SETTING

Postoperative recovery area.

PATIENTS

56,538 patients, ASA class II to IV, non-invasive respiratory monitoring, and post-operative respiratory depression.

INTERVENTIONS

Continuous pulse oximetry with or without capnography versus routine monitoring.

MEASUREMENTS

Respiratory rate, oxygen saturation, adverse events, and rescue events.

RESULTS

23 studies (17 examined CPOX without capnography and 5 examined CPOX with capnography) were included in this systematic review. CPOX was better at recognizing desaturation (SpO2 < 90%) OR: 11.94 (95% CI: 6.85, 20.82; p < 0.01) compared to standard monitoring. No significant differences were reported for ICU transfer, reintubation, and non-invasive ventilation between the two groups.

CONCLUSIONS

Oxygen desaturation was the only outcome better detected with CPOX in postoperative patients in hospital wards. These comparisons were limited by the small number of studies that could be pooled for each outcome and the heterogeneity between the studies.

Intrathecal Morphine and Post-Operative Pain Relief in Robotic Surgeries: A Systematic Review and Meta-Analysis

Despite the potential benefits of intrathecal morphine (ITM), the precise role and dosing of ITM in robotic assisted surgery (RAS) remains unclear. This systematic review explores real-world evidence to evaluate the efficacy and outcomes of ITM in patients undergoing RAS. In accordance with PRISMA guidelines, a comprehensive search was conducted on four databases: MEDLINE, Embase, Cochrane Library and APA PsycInfo. Primary outcomes included pain scores at rest and on exertion at 24- and 48-h time intervals, and secondary outcomes aimed to explore the side effects of ITM. A meta-analysis was conducted to determine mean differences. A risk of bias assessment was conducted via the Cochrane Risk of Bias 2 tool. A total of 9 RCTs involving 619 patients were included in this review, of which 298 patients were administered ITM. Significant pain score reductions were observed both at rest (MD = -27.15; 95% CI [-43.97, -10.33]; I2 = 95%; p = 0.002) and on exertion (MD = -25.88; 95% CI [-37.03, -14.72]; I2 = 79%; p = 0.0003) 24 h postoperatively in the ITM groups, accompanied by a notable decrease in postoperative IV morphine equivalent consumption at 24 h (MD = -20.13; 95% CI [-30.74, -9.52]; I2 = 77%; p = 0.0002). ITM improved pain scores both at rest and on exertion at 24 and 48 h intervals, concurrently reducing the need for postoperative opioid consumption, but at the cost of an increased incidence of adverse events.

Postoperative effects and complications of intrathecal morphine compared to epidural analgesia in patients undergoing intracorporeal robot-assisted radical cystectomy: a retrospective study

BACKGROUND

Analgesia after robot assisted radical cystectomy aims to reduce postoperative pain and opioid consumption, while facilitating early mobilization and enteral nutrition and minimizing complications. Epidural analgesia is currently recommended for an open radical cystectomy, but it is unclear if intrathecal morphine is a suiting, less-invasive alternative for a robot-assisted radical cystectomy.

METHODS

The analgesic method of choice changed from epidural anesthesia to intrathecal anesthesia for patients undergoing a robot-assisted radical cystectomy. This single-center retrospective study aims to investigate if there is a difference between epidural and intrathecal analgesia in postoperative pain scores, opioid consumption, length of hospital stays and postoperative complications. An Propensity Matched Analysis was added to conventional analysis to consolidate the findings.

RESULTS

The study population consisted of 153 patients of whom 114 received an epidural catheter with bupivacaine/sufentanil and 39 received a single shot of intrathecal bupivacaine/morphine. Mean pain scores on the first two postoperative days (POD) were slightly higher in the intrathecal analgesia group (epidural versus intrathecal analgesia, NRS POD0: 0(0-2)[0-8] versus 1(0-3)[0-5], p = 0.050; POD1: 2(1-3)[0-8] versus 3(1-4)[0-7], p = 0.058; POD2: 2(0-3)[0-8] versus 3(2-4)[0-7], p = 0.010). Total postoperative morphine consumption was similar over the first seven days: 15 mg (5-35)[0-148] in the epidural group versus 11 mg (0-35)[0-148] in the intrathecal morphine group, p = 0.167. Length of hospital stay and time until fit for discharge where slightly higher in the epidural group (respectively 7 days (5-9)[4-42] versus 6 days (5-7)[4-38], p = 0.006, and 5 days (4-8)[3-30]) versus 5 days (4-6)[3-34], p = 0.018). There was no further difference in postoperative course.

CONCLUSIONS

This study showed that the effects of epidural analgesia and intrathecal morphine are comparable and that intrathecal morphine may be a suiting alternative for epidural analgesia.

Does the combination of intrathecal fentanyl and morphine improve clinical outcomes in patients undergoing lumbar fusions?

Intrathecal morphine (ITM) has been widely effective in improving postoperative outcomes in patients undergoing a multitude of surgeries, including lumbar spine fusion. A major limitation of ITM administration is the increase in the incidence of respiratory depression in a dose-dependent manner. One way to bypass this is to use a more potent opioid with a shorter half-life, such as fentanyl. This is a retrospective analysis of patients who underwent one- or two-level transforaminal lumbar interbody fusions. The patients received one of two interventions: 0.2mg intrathecal duramorph/morphine (ITM group; n=70), 0.2mg duramorph + 50 mcg fentanyl (ITM + fentanyl group; n=68) and the control group (n=102). Primary outcomes included postoperative pain (Visual Analog Scale) and opioid intake (MED - morphine equivalent dosage, mg) for postoperative days (POD) 1- 4. Secondary outcomes included opioid-related side effects. One-way analyses of variance and follow-up post-hoc Tukey's honest significant difference statistical tests were used to measure treatment effects. Significantly lower POD1 pain scores for both the ITM and ITM + fentanyl groups vs. control were detected, with no difference between the ITM vs. ITM + fentanyl groups. Similar results were found for POD1 MED intake. A multivariate regression analysis controlling for confounding variables did not attenuate the differences seen in POD1 pain scores while revealing that only the ITM + fentanyl predicted a decrease in POD1 MED intake. No differences were seen for postoperative opioid-related side effects. Our study provides support for supplementing a low dose of both intrathecal morphine and fentanyl to improve postoperative outcomes.

Safety and effectiveness of adding fentanyl or sufentanil to spinal anesthesia: systematic review and meta-analysis of randomized controlled trials

INTRODUCTION

Spinal infusions of either fentanyl or sufentanil have been reported in international reports, articles, and scientific events worldwide. This study aimed to determine whether intrathecal fentanyl or sufentanil offers safety in mortality and perioperative adverse events.

METHODS

MEDLINE (via PubMed), EMBASE, CENTRAL (Cochrane library databases), gray literature, hand-searching, and clinicaltrials.gov were systematically searched. Randomized controlled trials with no language, data, or status restrictions were included, comparing the effectiveness and safety of adding spinal lipophilic opioid to local anesthetics (LAs). Data were pooled using the random-effects models or fixed-effect models based on heterogeneity.

RESULTS

The initial search retrieved 4469 records; 3241 records were eligible, and 3152 articles were excluded after reading titles and abstracts, with a high agreement rate (98.6%). After reading the full texts, 76 articles remained. Spinal fentanyl and sufentanil significantly reduced postoperative pain and opioid consumption, increased analgesia and pruritus. Fentanyl, but not sufentanil, significantly reduced both postoperative nausea and vomiting, and postoperative shivering; compared to LAs alone. The analyzed studies did not report any case of in-hospital mortality related to spinal lipophilic opioids. The rate of respiratory depression was 0.7% and 0.8% when spinal fentanyl or sufentanil was added and when it was not, respectively. Episodes of respiratory depression were rare, uneventful, occurred intraoperatively, and were easily manageable.

CONCLUSION

There is moderate to high quality certainty that there is evidence regarding the safety and effectiveness of adding lipophilic opioids to LAs in spinal anesthesia.

The effect of intraoperative intrathecal opioid administration on the length of stay and postoperative pain control for patients undergoing lumbar interbody fusion

PURPOSE

In an effort to control postoperative pain more effectively in spinal fusion patients, intraoperative intrathecal morphine (ITM) administration is gaining popularity and acceptance with clinicians. This study seeks to determine the impact of intraoperative intrathecal opioid (ITO) administration following lumbar fusion surgery on postoperative pain and length of hospitalization as primary outcomes. Secondary outcomes will investigate postoperative opioid intake and side effects.

METHODS

The retrospective analysis of collected data was performed. The study compared patients undergoing one- or two-level transforaminal interbody fusions between 2019 and 2021 who intraoperatively received two different ITO doses (n = 89) vs. the reference group (n = 48) that did not receive ITO. The patients in the ITO group received either 0.2 mg (n = 44) of duramorph or 0.2 mg duramorph + 50 mcg fentanyl (n = 45). The effect of ITO was evaluated for the first four postoperative days (POD) on pain scores (visual analog scale), length of stay (LOS, hours) and opioid requirement (MED, morphine equivalent dose).

RESULTS

In the ITO group, a significant reduction of postoperative pain scores (t(99) = 4.3, p < 0.001) and opioid intake (t(70) = 2.49, p = 0.015) was noted on POD1. Cohen's d effect sizes were 0.76 and 0.50, meaning that postoperative pain and MED intake were reduced by about ¾ to ½ standard deviations (SD) in the ITO group. Further, multivariate regression models revealed that ITO administration predicted lower postoperative pain scores for the two PODs (β =  - 0.83, p < 0.001; β =  - 0.63, p = 0.022) and MED intake for the first two PODs (β =  - 20.8, p = 0.047; β =  - 16.4, p = 0.030). Mean LOS was 15.4 h less in the ITO group (mean ± SD, 63.4 ± 37.1 vs. 78.8 ± 39.6, p = 0.10).

CONCLUSIONS

In conclusion, our study provides results in a large sample of patients undergoing transforaminal lumbar fusions. The results demonstrated that ITO administration is effective in reducing POD1 pain scores and POD1-2 opioid requirement while not increasing the risk of any opioid-related side effects.

Influence of genetic variants on remifentanil sensitivity in Chinese women

WHAT IS KNOWN AND OBJECTIVE

Significant individual differences have been observed in pain sensitivity and analgesic effect of opioids. Previous studies have shown that genetic factors contributed to analgesics requirement obviously. Therefore, we investigated the role of genetic polymorphisms in the sensitivity to the analgesic effect of remifentanil in this study.

METHODS

One hundred thirty-seven patients undergoing gynaecological surgery were observed. Before procedures, we measured the basal pain threshold of each patient, including the pressure pain threshold and pressure pain tolerance threshold. Subsequently, patients received a continuous remifentanil infusion for 15 min at a constant rate of 0.2 μg/(kg min). The pain thresholds were measured again after the remifentanil infusion. Moreover, respiratory depression was estimated using oxygen saturation during infusion. DNA was extracted from peripheral venous blood and genotyped using SNaPshot technology.

RESULTS AND DISCUSSION

Polymorphisms were found in genes associated with the individual variation in analgesia. Participants carrying OPRM1 rs9397685 AA, ADRB1 rs1801253 CC, and GCH1 rs8007267 CC polymorphisms showed higher sensitivity to analgesic effect induced by remifentanil, and the participants carrying the OPRD1 rs2234918 TT showed lower sensitivity to remifentanil-related respiratory depression. Moreover, individual susceptibility to remifentanil increases with age.

WHAT IS NEW AND CONCLUSION

Gene variation in OPRM1 rs9397685 AA, ADRB1 rs1801253 CC, GCH1 rs8007267 CC, and OPRD1 rs2234918 TT were related to the conspicuous interindividual differences in the analgesia and respiratory depression of remifentanil, mainly by affecting the target protein receptors and relative metabolic enzymes.

The use of intrathecal morphine for acute postoperative pain in lower limb arthroplasty surgery: a survey of practice at an academic hospital

BACKGROUND AND PURPOSE OF THE STUDY

Intrathecal morphine (ITM) provides optimal postoperative analgesia in patients who are scheduled for total knee and hip operation with spinal anaesthesia. However, the ideal dose at which maximal analgesic effect occurs with minimal side effects is not known. This study aimed to describe the use of two doses of ITM and side effect profile in patients undergoing elective hip and knee arthroplasty.

METHODS

This was a prospective, descriptive, and contextual study conducted on patients who had total hip and knee replacement at Chris Hani Baragwanath Academic Hospital from 1 September to 30 November 2020. The sample size consisted of 66 patients who were 18 years and older, American Society of Anaesthesiology (ASA) classification 1-3, patients who had received either 100 mcg or 150 mcg ITM dose under spinal anaesthesia and sent to the ward postoperatively. Visual Analogue Scale (VAS) score was used to assess pain in the first 24 h, consumption of rescue analgesia and reported side effects were documented.

RESULTS

There was no relationship between age, weight, ASA classification or type of surgery and VAS score classification groups. Patients who received 100 mcg ITM had a higher median VAS pain score 2 (1-5) compared to those who received 150 mcg ITM 1 (0-2), p = 0.01. The need for rescue analgesia between the two groups was marginally less in the 150 mcg ITM group (p = 0.098). There was no difference in the rate of side effects between the 100 mcg ITM group [12 (41%)] and the 150 mcg ITM group [17 (59%)], p = 0.92. Rescue analgesia was marginally different between groups, p = 0.09. There were no real differences in the VAS pain scores between the total knee and total hip surgeries. None of the patients experienced clinically significant respiratory depression.

CONCLUSION

The 150 mcg ITM dose provided good analgesic effects with longer duration of action and comparable side effect profile to the 100 mcg ITM dose. This dose was not associated with development of respiratory depression and can therefore be administered safely to patients who are discharged to the ward postoperatively in a resource constraint environment.

Comparison of low-dose morphine intrathecal analgesia and sufentanil PCIA in elderly patients with hip fracture undergoing single spinal anesthesia - a randomized clinical trial

Background

The complications of postoperative pain, such as hypertension, hypermetabolism, irritability, and postoperative cognitive dysfunction, significantly affect the postoperative rehabilitation of elderly patients. Intrathecal morphine prolongs analgesia after surgery, but has been implicated in nausea and vomiting, pruritus, postoperative respiratory depression, or apneic episodes. The present study explored the effect and safety of low-dose morphine used adjunctively with bupivacaine during single spinal anesthesia or sufentanil patient-controlled intravenous analgesia (PCIA) in elderly patients with hip fracture surgery. Since elderly patients often need anticoagulant therapy in the early postoperative period, single spinal anesthesia was involved in completing the operation in this study.

Methods

Eighty elderly patients aged 70–85 years who underwent elective hip fracture surgery with single spinal anesthesia were divided into two groups, 12.5 mg of 0.5% hyperbaric bupivacaine with 100 µg of morphine (morphine group, group M) and 12.5 mg of 0.5% hyperbaric bupivacaine with 100 µg of sufentanil PCIA (sufentanil group, group S). The analgesia scores using the visual analogue scale (VAS), the Brinell comfort scale (BCS) were evaluated at 6, 12, 24, and 48 h after operation, and adverse reactions were recorded such as nausea and vomiting, pruritus, sedation, respiratory depression, and POD (postoperative delirium) with Delirium Rating Scale-r 98.

Results

Within 24 h after operation, the analgesic and BCS scores of group M were better than those of group S (P < 0.05). Group M had higher frequency of skin pruritus than group S within 24 h, and the difference was statistically significant. The incidence of POD in group M (2 cases) was lower than that in group S (6 cases) (5.71% vs 18.18%) (P < 0.05) with the DRS-r 98 scores. No significant difference was observed in nausea and vomiting between the two groups, and the difference of severe respiratory depression was not found in both groups.

Conclusion

Compared with sufentanil PCIA, low-dose intrathecal morphine has a satisfactory analgesic effect, and little effect on the patient's cognitive function with low medical cost. Under effective respiratory monitoring, it can be used safely and effectively in elderly patients with hip fracture.

Trial registration

Registered with the Chinese Clinical Trial Registry under ChiCTR2100042706. 26/01/2021.

Serious Adverse Events after a Single Shot of Intrathecal Morphine: A Case Series and Systematic Review

Background

The dose of intrathecal morphine is important because of its narrow therapeutic range. Due to a compounding error, pharmacy-compounded, ready-to-use syringes contained 1 mg ml⁻¹ morphine instead of the intended 50 mcg ml⁻¹. Six patients consequently received this twenty-fold dose. This study aims to describe the serious adverse events in these six patients and a systematic review is added to describe the characteristics of serious adverse events after intrathecal morphine.

Methods

A retrospective case series described all six patients that received the erroneous morphine intrathecally for analgesia after laparoscopic segmental colonic resections. The patients' charts were reviewed for the occurrence, timing, duration and management of adverse events, the vital signs at the night after surgery, and length of hospital stay. A systematic review investigated characteristics of serious adverse events after intrathecal morphine in a perioperative setting.

Results

Four patients had a serious adverse event, which was respiratory depression combined with somnolence (n = 3) and hypotension (n = 1). The review yielded 63 cases with serious adverse events, predominantly somnolence and/or respiratory depression. The onset occurred between 2 and 24 hours after injection. The severity of symptoms varied and life-threatening respiratory depression only occurred after a dose >900 mcg or when potentiating medication was used. Naloxone did not affect analgesia. No prolonged sequalae occurred.

Conclusion

This study reveals that respiratory depression and somnolence are the predominant serious adverse events after intrathecal morphine in a perioperative setting and demonstrated a large variation in the presentation of symptoms.

Postpartum Respiratory Depression

Postpartum respiratory depression is a complex, multifactorial issue that encompasses a patient's baseline preexisting conditions, certain pregnancy-specific conditions or complications, as well as the iatrogenic element of various medications given in the peripartum period. In this review, we discuss many of these factors including obesity, sleep-disordered breathing, chronic lung disease, neuromuscular disorders, opioids, preeclampsia, peripartum cardiomyopathy, postpartum hemorrhage, amniotic fluid embolism, sepsis, acute respiratory distress syndrome (ARDS), and medications such as analgesics, sedatives, anesthetics, and magnesium. Current recommendations for screening, treatment, and prevention are also discussed.

[Neuraxial Morphine for Postoperative Analgesia after Caesarean Deliveries]

The use of neuraxial morphine, in combination with nonopioid analgesic regimens for postoperative analgesia after Caesarean deliveries is common practice, especially in the Anglo-American world. Neuraxial morphine offers a longer-lasting superior analgesia than intravenous opioids or patient-controlled analgesia. If neuraxial anaesthesia is being used for a caesarean delivery, it may be recommended to concomitantly administer neuraxial morphine for the postoperative analgesia.A low dose of neuraxial morphine in a healthy parturient bears a low morbidity and mortality risk. The optimal frequency, duration and modality of respiratory monitoring for patients at low risk for respiratory depression is dependent on the dose of morphine administered and the patient-specific and obstetric risk profile.

Evaluation of Noninvasive Respiratory Volume Monitoring in the PACU of a Low Resource Kenyan Hospital

This research aims to evaluate the use of the noninvasive respiratory volume monitor (RVM) compared to the standard of care (SOC) in the Post-Anesthesia Care Unit (PACU) of Kijabe Hospital, Kenya. The RVM provides real-time measurements for quantitative monitoring of non-intubated patients. Our evaluation was focused on the incidence of postoperative opioid-induced respiratory depression (OIRD). The RVM cohort (N = 50) received quantitative OIRD assessment via the RVM, which included respiratory rate, minute ventilation, and tidal volume. The SOC cohort (N = 46) received qualitative OIRD assessment via patient monitoring with oxygenation measurements (SpO₂) and physical examination. All diagnosed cases of OIRD were in the RVM cohort (9/50). In the RVM cohort, participants stayed longer in the PACU and required more frequent airway maneuvers and supplemental oxygen, compared to SOC (all p < 0.05). The SOC cohort may have had fewer diagnoses of OIRD due to the challenging task of distinguishing hypoventilation versus OIRD in the absence of quantitative data. To account for the higher OIRD risk with general anesthesia (GA), a subgroup analysis was performed for only participants who underwent GA, which showed similar results. The use of RVM for respiratory monitoring of OIRD may allow for more proactive care.

Quantifying the incidence of clinically significant respiratory depression in women with and without obesity class III receiving neuraxial morphine for post-cesarean analgesia: a retrospective cohort study

BACKGROUND

Obesity is a suspected risk factor for respiratory depression following neuraxial morphine for post-cesarean analgesia, however monitoring guidelines for obese obstetric patients are based on small, limited studies. We tested the hypothesis that clinically significant respiratory depression following neuraxial morphine occurs more commonly in women with body mass index (BMI) ≥40 kg/m² compared with BMI <40 kg/m².

METHODS

We conducted a single-center, retrospective chart review (2006-2017) of obstetric patients with clinically significant respiratory depression following neuraxial morphine, defined as: (1) opioid antagonist administration; (2) rapid response team activation (initiated in April 2010); or (3) tracheal intubation due to a respiratory event. The incidence of respiratory depression was compared between women with BMI ≥40 kg/m² and BMI <40 kg/m².

RESULTS

In total, 11 327 women received neuraxial morphine (n=1945 BMI ≥40 kg/m²; n=9382 BMI <40 kg/m²). Women with BMI ≥40 kg/m² had higher rates of sleep apnea, hypertensive disorders, and magnesium administration. Sixteen cases of clinically significant respiratory depression occurred within seven days postpartum. The incidence did not significantly differ between groups (odds ratio 2.2, 95% CI 0.6 to 6.9, P=0.174). Neuraxial morphine was not deemed causative in any case, however women with BMI ≥40 kg/m² had higher rates of tracheal intubation unrelated to neuraxial morphine (2/1945 vs. 0/9382, P=0.029).

CONCLUSIONS

Respiratory depression in this population is rare. A larger sample (∼75 000) is required to determine whether the incidence is higher with BMI ≥40 kg/m². Tracheal intubation was higher among the BMI ≥40 kg/m² cohort, likely due to more comorbidities.

A Phase I Placebo-Controlled Trial Comparing the Effects of Buprenorphine Buccal Film and Oral Oxycodone Hydrochloride Administration on Respiratory Drive

Introduction

Buprenorphine is a partial μ-opioid receptor agonist that, unlike full μ-opioid receptor agonists, has been shown to have a ceiling effect on respiratory depression. Buprenorphine buccal film (BBF) is approved by the US Food and Drug Administration for use in patients with chronic pain severe enough to require daily, around-the-clock, long-term opioid treatment and for whom alternative treatment options are inadequate. This study was conducted to compare the effects of BBF and immediate-release oral oxycodone hydrochloride administration on respiratory drive, as measured by the ventilatory response to hypercapnia (VRH) after drug administration.

Methods

Subjects (N = 19) were men and women, ages 27–41 years, self-identifying as recreational opioid users who were not physically dependent on opioids as determined via a Naloxone Challenge Test. Respiratory drive was evaluated by measuring VRH through the assessment of the maximum decrease in minute ventilation (E_max) after administration of each treatment. The treatments utilized in this study included 300, 600, and 900 μg BBF; 30 and 60 mg orally administered oxycodone; and placebo (each separated by a 7-day washout period). Effects on respiratory drive were assessed using a double-blind, double-dummy, six-treatment, six-period, placebo-controlled, randomized crossover design. Statistical analyses were performed using a linear mixed-effects model.

Results

The least squares mean differences in minute volume E_max (L/min, versus placebo) were as follows: 300 μg BBF (+ 1.24, P = 0.529), 600 μg BBF (+ 0.23, P = 0.908), 900 μg BBF (+ 0.93, P = 0.637), 30 mg oxycodone (− 0.79, P = 0.687), and 60 mg oxycodone (− 5.23, P = 0.010).

Conclusions

BBF did not significantly reduce respiratory drive at any dose compared with placebo, including at the maximum available prescription dose of 900 μg. Administration of oxycodone resulted in a significant dose-dependent decrease in respiratory drive. These data suggest that BBF may be a safer treatment option than full μ-opioid receptor agonists for patients with chronic pain.

Trial Registration

ClinicalTrials.gov identifier, NCT03996694.

Electronic supplementary material

The online version of this article (10.1007/s12325-020-01481-0) contains supplementary material, which is available to authorized users.

Measurement of drug concentration and bacterial contamination after diluting morphine for intrathecal administration: an experimental study

Background

Low concentrations of morphine are required for safe dosing for intrathecal injections. Sometimes, manual dilution of morphine is performed to achieve these low concentrations, but risks dilution errors and bacterial contamination. The primary goal was to compare the concentrations of morphine and bupivacaine between four groups of syringes. The secondary goal was to investigate the difference in contamination rate between these groups.

Methods

Twenty-five experienced anesthesia providers were asked to prepare a mixture of bupivacaine 2.0 mg/ml and morphine 60 μg/ml using 3 different methods as clean and precise as possible. The fourth method used was the aspiration of ampoules prepared by the pharmacy. The concentrations of morphine and bupivacaine were measured by High-Pressure Liquid Chromatography (HPLC). The medication was cultured for bacterial contamination.

Results

Group 1 (median 60 μg/ml; 95% CI: 59–110 μg/ml) yielded 3 outliers above 180 μg/ml morphine concentration. Group 2 (76 μg/ml; 95% CI: 72–80 μg/ml) and 3 (69 μg/ml; 95% CI: 66–71 μg/ml) were consistently higher than the target concentration of 60 μg. The group “pharmacy” was precise and accurate (59 μg/ml; 95% CI: 59–59 μg/ml). Group 2 and “pharmacy” had one contaminated sample with a spore-forming aerobic gram-positive rod.

Conclusion

Manually diluted morphine is at risk for deviating concentrations, which could lead to increased side-effects. Medication produced by the hospital pharmacy was highly accurate. Furthermore, even when precautions are undertaken, contamination of the medication is a serious risk and appeared to be unrelated to the dilution process.

Intrathecal hydrophilic opioids for abdominal surgery: a meta-analysis, meta-regression, and trial sequential analysis

Background

Intrathecal hydrophilic opioids decrease systemic opioid consumption after abdominal surgery and potentially facilitate enhanced recovery. A meta-analysis is needed to quantify associated risks and benefits.

Methods

A systematic search was performed to find RCTs investigating intrathecal hydrophilic opioids in abdominal surgery. Caesarean section and continuous regional or neuraxial techniques were excluded. Several subgroup analyses were prespecified. A conventional meta-analysis, meta-regression, trial sequential analysis, and provision of GRADE scores were planned.

Results

The search yielded 40 trials consisting of 2500 patients. A difference was detected in ‘i.v. morphine consumption’ at Day 1 {mean difference [MD] −18.4 mg, (95% confidence interval [CI]: −22.3 to −14.4)} and Day 2 (MD −25.5 mg [95% CI: −30.2 to −20.8]), pain scores at Day 1 in rest (MD −0.9 [95% CI: −1.1 to −0.7]) and during movement (MD −1.2 [95% CI: −1.6 to −0.8]), length of stay (MD −0.2 days [95% CI: −0.4 to −0.1]) and pruritus (relative risk 4.3 [95% CI: 2.5–7.5]) but not in nausea or sedation. A difference was detected for respiratory depression (odds ratio 5.5 [95% CI: 2.1–14.2]) but not when two small outlying studies were excluded (odds ratio 1.4 [95% CI: 0.4–5.2]). The level of evidence was graded as high for morphine consumption, in part because the required information size was reached.

Conclusions

This study showed important opioid-sparing effects of intrathecal hydrophilic opioids. Our data suggest a dose-dependent relationship between the risk of respiratory depression and the dose of intrathecal opioids. Excluding two high-dose studies, intrathecal opioids have a comparable incidence of respiratory depression as the control group.

Clinical trial registration

PROSPERO-registry: CRD42018090682.

Opioid Alternatives in Spine Surgery: A Narrative Review

Adequate analgesia is known to improve outcomes after spine surgery. Despite recent attention highlighting the negative effects of narcotics and their addiction potential, opioids have been the mainstay of management for providing analgesia following spine surgeries. However, side effects including hyperalgesia, tolerance, and subsequent dependence restrict the generous usage of opioids. Multimodal analgesia regimens acting through different mechanisms offer significant opioid sparing and minimize the side effects of individual drugs. Hence, they are being increasingly incorporated into enhanced recovery protocols. Multimodal analgesia includes drugs such as N-methyl-D-aspartate antagonists, nonsteroidal anti-inflammatory drugs and membrane-stabilizing agents, neuraxial opioids, local anesthetic infiltration, and fascial compartment blocks. Analgesia started before the painful stimulus, termed preemptive analgesia, facilitates subsequent pain management. Both nonsteroidal anti-inflammatory drugs and neuraxial analgesia have been conclusively shown to reduce opioid requirements after spine surgery, and there is a resurgence of interest in the use of low-dose ketamine or methadone. Neuraxial narcotics offer enhanced analgesia for a longer duration with lower dosage and side effect profiles compared with systemic opioid administration. Fascial compartment blocks are increasingly used as they provide effective analgesia with fewer adverse effects. In this narrative review, we will discuss multimodality analgesic regimens incorporating opioid-sparing adjuvants to manage pain after spine surgery.

Effects of Standard and Sustained-release Buprenorphine on the Minimum Alveolar Concentration of Isoflurane in C57BL/6 Mice

Both standard and sustained-release injectable formulations of buprenorphine (Bup and BupSR, respectively) are used as preemptive analgesics, potentially affecting gas anesthetic requirements. This study tested the effects of Bup and BupSR on isoflurane requirements and confirmed that buprenorphine could reduce isoflurane requirements during a laparotomy in mice. We hypothesized that both Bup and BupSR would significantly decrease the required minimum alveolar concentration (MAC) of isoflurane. C57BL/6 mice received either isotonic crystalloid fluid (control), Bup (0.1 mg/kg), or BupSR (1.2 mg/kg) subcutaneously 10 min prior to the induction of anesthesia. Each anesthetized mouse was tested at 2 isoflurane concentrations. A 300-g noxious stimulus was applied at each isoflurane concentration, alternating between hindfeet. In addition, a subset of mice underwent terminal laparotomy or 60 min of anesthesia after injection with Bup, BupSR, or saline to ensure an appropriate surgical plane of anesthesia. Mice were maintained at the lowest isoflurane concentration that resulted in 100% of mice at a surgical plane from the aforementioned MAC experiments (control, 2.0%; Bup and BupSR, 1.7%). Analysis showed that both Bup and BupSR significantly decreased isoflurane requirements by 25.5% and 14.4%, respectively. The isoflurane MAC for the control injection was 1.80% ± 0.09%; whereas Bup and BupSR decreased MAC to 1.34% ± 0.08% and 1.54% ± 0.09%, respectively. Sex was not a significantly different between the injection groups during MAC determination. All of the mice that underwent surgery achieved a surgical plane of anesthesia on the prescribed regimen and recovered normally after discontinuation of isoflurane. Lastly, heart and respiratory rates did not differ between mice that underwent surgery and those that were anesthetized only. Bup and BupSR are MAC-sparing in male and female C57BL/6 mice and can be used for effective multimodal anesthesia.

Prospective Observational Investigation of Capnography and Pulse Oximetry Monitoring After Cesarean Delivery With Intrathecal Morphine

BACKGROUND

Intrathecal morphine provides excellent analgesia after cesarean delivery; however, respiratory events such as apnea, bradypnea, and hypoxemia have been reported. The primary study aim was to estimate the number of apneas per subject, termed "apnea alert events" (AAEs) defined by no breath for 30-120 seconds, using continuous capnography in women who underwent cesarean delivery.

METHODS

We performed a prospective, observational study with institutional review board approval of women who underwent cesarean delivery with spinal anesthesia containing 150-µg intrathecal morphine. A STOP-Bang obstructive sleep apnea assessment was administered to all women. Women were requested to use continuous capnography and pulse oximetry for 24 hours after cesarean delivery. Nasal sampling cannula measured end-tidal carbon dioxide (EtCO2) and respiratory rate (RR), and oxygen saturation (SpO2) as measured by pulse oximetry. Capnography data were defined as "valid" when EtCO2 >10 mm Hg, RR >5 breaths per minute (bpm), SpO2 >70%, or during apnea (AAE) defined as "no breath" (EtCO2, <5 mm Hg) for 30-120 seconds. Individual respiratory variable alerts were 10-second means of EtCO2 <10 mm Hg, RR <8 bpm, and SpO2 <94%. Nurse observations of RR (hourly and blinded to capnography) are reported.

RESULTS

We recruited 80 women, mean (standard deviation [SD]) 35 (5) years, 47% body mass index >30 kg/m2/weight >90 kg, and 11% with suspected obstructive sleep apnea (known or STOP-Bang score >3). The duration of normal capnography and pulse oximetry data was mean (SD) (range) 8:28 (7:51) (0:00-22:32) and 15:08 (6:42) (1:31-23:07) hours:minutes, respectively; 6 women did not use the capnography. There were 198 AAEs, mean (SD) duration 57 (27) seconds experienced by 39/74 (53%) women, median (95% confidence interval for median) (range) 1 (0-1) (0-29) per subject. Observation of RR by nurses was ≥14 bpm at all time-points for all women, r = 0.05 between capnography and nurse RR (95% confidence interval, -0.04 to 0.14). There were no clinically relevant adverse events for any woman. Sixty-five women (82%) had complaints with the capnography device, including itchy nose, nausea, interference with nursing baby, and overall inconvenience.

CONCLUSIONS

We report 198 AAEs detected by capnography among women who underwent cesarean delivery after receiving intrathecal morphine. These apneas were not confirmed by the intermittent hourly nursing observations. Absence of observer verification precludes distinction between real, albeit nonclinically significant alerts with capnography versus false apneas. Discomfort with the nasal sampling cannula and frequent alerts may impact capnography application after cesarean delivery. No clinically relevant adverse events occurred.

The effect of intrathecal bupivacaine/morphine on quality of recovery in robot-assisted radical prostatectomy: a randomised controlled trial

Robot‐assisted radical prostatectomy causes discomfort in the immediate postoperative period. This randomised controlled trial investigated if intrathecal bupivacaine/morphine, in addition to general anaesthesia, could be beneficial for the postoperative quality of recovery. One hundred and fifty‐five patients were randomly allocated to an intervention group that received intrathecal 12.5 mg bupivacaine/300 μg morphine (20% dose reduction in patients > 75 years) or a control group receiving a subcutaneous sham injection and an intravenous loading dose of 0.1 mg.kg⁻¹ morphine. Both groups received standardised general anaesthesia and the same postoperative analgesic regimen. The primary outcome was a decrease in the Quality of Recovery‐15 (QoR‐15) questionnaire score on postoperative day 1. The intervention group (n = 76) had less reduction in QoR‐15 on postoperative day 1; median (IQR [range]) 10% (1–8 [−60% to 50%]) vs. 13% (5–24 [−6% to 50%]), p = 0.019, and used less morphine during the admission; 2 mg (1–7 [0–41 mg]) vs. 15 mg (12–20 [8–61 mg]), p < 0.001. Furthermore, they perceived lower pain scores during exertion; numeric rating scale (NRS) 3 (1–6 [0–9]) vs. 5 (3–7 [0–9]), p = 0.001; less bladder spasms (NRS 1 (0–2 [0–10]) vs. 2 (0–5 [0–10]), p = 0.001 and less sedation; NRS 2 (0–3 [0–10]) vs. 3 (2–6 [0–10]), p = 0.005. Moreover, the intervention group used less rescue medication. Pruritus was more severe in the intervention group; NRS 4 (1–7 [0–10]) vs. 0 (0–1 [0–10]), p = 0.000. We conclude that despite a modest increase in the incidence of pruritus, multimodal pain management with intrathecal bupivacaine/morphine remains a viable option for robot‐assisted radical prostatectomy.

Addition of Intrathecal Morphine for Postoperative Pain Management in Pediatric Spine Surgery: A Meta-analysis

STUDY DESIGN

Meta-analysis.

OBJECTIVE

The objective of this study was to determine whether adjunctive intrathecal morphine (ITM) reduces postoperative analgesic consumption following pediatric spine surgery.

SUMMARY OF BACKGROUND DATA

Previous studies that have tested supplemental ITM to manage pain after pediatric spine surgery have been limited by small sample sizes.

METHODS

A comprehensive search of PubMed, Web of Science, Clinicaltrials.gov, and the Cochrane Central Register of Controlled Trials was performed for clinical trials and observational studies. Time to first analgesic demand, postoperative analgesic use, pain scores, and complication data were abstracted from each study. Mean difference (MD) and 95% confidence interval (CI) were used to compare continuous outcomes and odds ratios (OR) and 95% CI were used for dichotomous outcomes.

RESULTS

A total of 5 studies, including 3 randomized controlled trials and 2 retrospective chart reviews, containing 636 subjects, were incorporated into meta-analysis. Subjects that were administered ITM in addition to postoperative analgesics (ITM group) were compared with those receiving postoperative analgesics only (control group). In the ITM group, time to first analgesic demand was longer (MD, 8.79; 95% CI, 4.20-13.37; P<0.001), cumulative analgesic consumption was reduced at 24 hours (MD, -0.40; 95% CI, -0.56 to -0.24; P<0.001), and cumulative analgesic consumption was reduced at 48 hours (MD, -0.43; 95% CI, -0.59 to -0.27; P<0.001). Neither postoperative pain scores at 24 hours (P=0.16) nor 48 hours (P=0.18) were significantly different between ITM and control groups. Rates of respiratory depression, nausea, vomiting, and pruritus were not different between groups (all Ps>0.05).

CONCLUSIONS

Addition of ITM in pediatric spine surgery produced a potent analgesic effect in the immediate postoperative period. Patients administered ITM did not request opiates as early as control and consumed fewer opiates by the second postoperative day. Furthermore, use of ITM did not increase complications such as respiratory depression, nausea, vomiting, or pruritus.

Postoperative Clinical Monitoring After Morphine Administration: A Retrospective Multicenter Practice Survey

BACKGROUND

The objective of this survey was to describe the clinical monitoring practically used after intravenous, subcutaneous or neuraxial (epidural or intrathecal) administration of morphine.

METHODS

It was a descriptive, retrospective, multicenter (10 hospitals) survey based on the medical charts' analysis, which evaluated the postoperative clinical monitoring after morphine administration.

RESULTS

Morphine was delivered intravenously (69%), intrathecally (19%), epidurally (10%) and/or subcutaneously (12%). Clinical monitoring protocols and protocols for the management of side effects were both present in 60% (n=6/10), only one of the two types of protocols in 10% (n=1/10) and both absent in 30% (n=3/10). Protocols for the management of respiratory depression and consciousness evaluation were present in 70% of cases (n=7/10). These events were reported on medical records without any prescription or protocol in 35% (n=14/40) and 37,5% (n=15/40) respectively. Prescriptions for respiratory rate evaluation and clinical monitoring of consciousness were in agreement with only 20% of the medical data and medical records. Different levels of respiratory rate were observed: 43% (n=3/7) below 8/min, 43% (n=3/7) below 10/min and 14% (n=1/7) below 12/min. Clinical monitoring was not performed in 31% (n=31/100) for consciousness and in 35% (n=35/100) for respiratory rate. Pulse oximeter was used in 48% (n=48/100) of patients. Capnography was never used. Respiratory depression occurred in 1% (n=1/100) of cases.

CONCLUSION

This survey emphasizes an important disparity in the prescription of medical monitoring and a lack of use of protocols when morphine is administered. It demonstrates the need for a standardization of protocols according to the existing guidelines.

Incidence of respiratory depression after epidural administration of morphine for cesarean delivery: findings using a continuous respiratory rate monitoring system

BACKGROUND

Epidural morphine is widely used for postoperative analgesia after cesarean delivery. However, respiratory depression can occur after neuraxial administration of morphine. Previous reports describing respiratory depression in obstetric patients have relied on intermittent visual counting of the respiratory rate. In this study, we estimated the incidence of respiratory depression in patients who had received epidural morphine after cesarean delivery, using a continuous respiratory rate monitoring system with a finger sensor.

METHODS

One hundred patients scheduled to undergo elective cesarean delivery and receive intraoperative neuraxial morphine between April and December 2016 were recruited for this single-center, prospective observational study. Postoperatively, all patients received epidural morphine 3 mg and were equipped with the Nellcor respiratory rate monitoring system. Respiratory depression was defined as both bradypnea (respiratory rate ≤10 breaths/min) and oxygen desaturation (mild ≤95%; moderate ≤90%; severe ≤85%) for longer than one minute. The number of patients with respiratory depression between administration of morphine and first ambulation was recorded hourly.

RESULTS

Complete monitoring was obtained for 89 of 100 women. The median duration of monitoring was 19.0 hours. Forty-six patients (52%) developed mild respiratory depression at least once before ambulation, but only one (1%) developed moderate respiratory depression. None required supplemental oxygen or naloxone.

CONCLUSIONS

Approximately half the women experienced mild respiratory depression, but only one developed moderate respiratory depression. Continuous respiratory rate monitoring until ambulation may assist in early identification of respiratory depression after neuraxial administration of morphine.

Intrathecal Morphine Following Lumbar Fusion: A Randomized, Placebo-Controlled Trial

BACKGROUND

Despite the potential for faster postoperative recovery and the ease of direct intraoperative injection, intrathecal morphine is rarely provided in lumbar spine surgery.

OBJECTIVE

To evaluate the safety and efficacy of intrathecal morphine following lumbar fusion.

METHODS

We randomly assigned 150 patients undergoing elective instrumented lumbar fusion to receive a single intrathecal injection of morphine (0.2 mg) or placebo (normal saline) immediately prior to wound closure. The primary outcome was pain on the visual-analogue scale during the first 24 h after surgery. Secondary outcomes included respiratory depression, treatment-related side effects, postoperative opioid requirements, and length of hospital stay. An intention-to-treat, repeated-measures analysis was used to estimate outcomes according to treatment in the primary analysis.

RESULTS

The baseline characteristics of the 2 groups were similar. Intrathecal morphine reduced pain both at rest (32% area under the curves [AUCs] difference, P < .01) and with movement (22% AUCs difference, P < .02) during the initial 24 h after surgery. The risk of respiratory depression was not increased by intrathecal morphine (hazard ratio, 0.86; 95% confidence interval, 0.44 to 1.68; P = .66). Although postoperative opioid requirements were reduced with intrathecal morphine (P < .03), lengths of hospital stay were similar (P = .32). Other than a trend towards increased intermittent catheterization among patients assigned to intrathecal morphine (P = .09), treatment-related side effects did not significantly differ. The early benefits of intrathecal morphine on postoperative pain were no longer apparent after 48 h.

CONCLUSION

A single intrathecal injection of 0.2 mg of morphine safely reduces postoperative pain following lumbar fusion.

Comparison of the Efficacy and Safety of Morphine and Fentanyl as Adjuvants to Bupivacaine in Providing Operative Anesthesia and Postoperative Analgesia in Subumblical Surgeries Using Combined Spinal Epidural Technique

Introduction:

The combined spinal epidural (CSE) technique involves intentional subarachnoid blockade and epidural catheter placement during the same procedure to combine their individual best features, to reduce the total drug dosage and avoid their respective disadvantages. The addition of opioids to local anesthetics (bupivacaine) for CSE anesthesia (CSEA) is increasingly common to enhance the block. Neuraxial fentanyl is more potent and has shorter duration of action than morphine which provides prolonged anesthesia and analgesia, however at the cost of increased incidence of adverse effects like delayed respiratory depression.

Aims and Objectives:

The aim is to compare the efficacy and safety of morphine and fentanyl as adjuvants to bupivacaine in subumblical surgeries using CSE technique. The characteristics of sensory and motor block, intergroup variations in pain, cardiorespiratory parameters, and adverse effects were compared between the two groups.

Materials and Methods:

A total of 60 patients belonging to physical status American Society of Anesthesiologists Classes I and II, aged 18–60 years were randomized into two groups: Group A (n = 30) received intrathecal 0.5% heavy bupivacaine 12.5 mg and morphine 2.85 μg/kg; Epidural Anesthetic bolus (when required/T11Regression) 8 ml 0.25% isobaric bupivacaine and 0.04 mg/kg morphine; Epidural Analgesic bolus (postoperative visual analog scale [VAS] score >30) 5 ml 0.125% isobaric bupivacaine and 0.04 mg/kg morphine and Group B (n = 30) received intrathecal 0.5% heavy bupivacaine 12.5 mg and fentanyl 0.35 μg/kg; Epidural Anesthetic bolus (when required/T11Regression) 8 ml 0.25% isobaric bupivacaine and 0.7 μg/kg fentanyl; Epidural Analgesic bolus (postoperative VAS score >30) 5 ml 0.125% isobaric bupivacaine and 0.7 μg/kg fentanyl.

Results and Conclusion:

Group A had significantly prolonged two segment regression time, T11 regression time, lower mean VAS score, prolonged effective analgesia, and required lesser number of epidural boluses in 24 h as compared to Group B (P < 0.001). There were no significant differences between the groups considering onset of sensory block, duration of motor block, median maximum sensory block level achieved after spinal component (T6), median highest sensory block level achieved after epidural anesthetic bolus (T7-4seg enhancement after regression to T11), cardiorespiratory parameters and adverse effects. None of the patients had respiratory depression nor was there any failure of spinal/epidural component of CSEA. Thus, addition of morphine to bupivacaine in CSEA produced prolonged effective anesthesia and postoperative analgesia compared to addition of fentanyl to bupivacaine without producing undue adverse effects.

The NAPRESSIM trial: the use of low-dose, prophylactic naloxone infusion to prevent respiratory depression with intrathecally administered morphine in elective hepatobiliary surgery: a study protocol and statistical analysis plan for a randomised controlled trial

BACKGROUND

Intrathecally administered morphine is effective as part of a postoperative analgesia regimen following major hepatopancreaticobiliary surgery. However, the potential for postoperative respiratory depression at the doses required for effective analgesia currently limits its clinical use. The use of a low-dose, prophylactic naloxone infusion following intrathecally administered morphine may significantly reduce postoperative respiratory depression. The NAPRESSIM trial aims to answer this question.

METHODS/DESIGN

'The use of low-dose, prophylactic naloxone infusion to prevent respiratory depression with intrathecally administered morphine' trial is an investigator-led, single-centre, randomised, double-blind, placebo-controlled, double-arm comparator study. The trial will recruit 96 patients aged > 18 years, undergoing major open hepatopancreaticobiliary resections, who are receiving intrathecally administered morphine as part of a standard anaesthetic regimen. It aims to investigate whether the prophylactic administration of naloxone via intravenous infusion compared to placebo will reduce the proportion of episodes of respiratory depression in this cohort of patients. Trial patients will receive an infusion of naloxone or placebo, commenced within 1 h of postoperative extubation continued until the first postoperative morning. The primary outcome is the rate of respiratory depression in the intervention group as compared to the placebo group. Secondary outcomes include pain scores, rates of nausea and vomiting, pruritus, sedation scores and adverse outcomes. We will also employ a novel, non-invasive, respiratory minute volume monitor (ExSpiron 1Xi, Respiratory Motion, Inc., 411 Waverley Oaks Road, Building 1, Suite 150, Waltham, MA, USA) to assess the monitor's accuracy for detecting respiratory depression.

DISCUSSION

The trial aims to provide a clear management plan to prevent respiratory depression after the intrathecal administration of morphine, and thereby improve patient safety.

TRIAL REGISTRATION

ClinicalTrials.gov, ID: NCT02885948 . Registered retrospectively on 4 July 2016. Protocol Version 2.0, 3 April 2017. Protocol identification (code or reference number): UCDCRC/15/006 EudraCT registration number: 2015-003504-22. Registered on 5 August 2015.

Portable respiratory polygraphy monitoring of obese mothers the first night after caesarean section with bupivacaine/morphine/fentanyl spinal anaesthesia

Background: Obesity, abdominal surgery, and intrathecal opioids are all factors associated with a risk for respiratory compromise. The aim of this explorative trial was to study the apnoea/hypopnea index 1st postoperative night in obese mothers having had caesarean section (CS) in spinal anaesthesia with a combination of bupivacaine/morphine and fentanyl. Methods: Consecutive obese (BMI >30 kg/m 2) mothers, ≥18 years, scheduled for CS with bupivacaine/morphine/fentanyl spinal anaesthesia were monitored with a portable polygraphy device Embletta /NOX on 1 st postoperative night. The apnoea/hypopnea index (AHI) was identified by clinical algorithm and assessed in accordance to general guidelines; number of apnoea/hypopnea episodes per hour: <5 "normal", ≥5 and <15 mild sleep apnoea, ≥15 and <30 moderate sleep apnoea, ≥ 30 severe sleep apnoea. Oxygen desaturation events were in similar manner calculated per hour as oxygen desaturation index (ODI). Results: Forty mothers were invited to participate: 27 consented, 23 were included, but polysomnography registration failed in 3. Among the 20 mothers studied: 11 had an AHI <5 ( normal), 7 mothers had AHI ≥5 but <15 ( mild OSAS) and 2 mothers had AHI ≥15 ( moderate OSA), none had an AHI ≥ 30. The ODI was on average 4.4, and eight patients had an ODI >5. Mothers with a high AHI (15.3 and 18.2) did not show high ODI. Mean saturation was 94% (91-96%), and four mothers had mean SpO 2 90-94%, none had a mean SpO2 <90%. Conclusion: Respiratory polygraphy 1 st night after caesarean section in spinal anaesthesia with morphine in moderately obese mothers showed AHIs that in sleep medicine terms are considered normal, mild and moderate. Obstructive events and episodes of desaturation were commonly not synchronised. Further studies looking at preoperative screening for sleep apnoea in obese mothers are warranted but early postop respiratory polygraphy recording is cumbersome and provided sparse important information.

Portable respiratory polygraphy monitoring of obese mothers the first night after caesarean section with bupivacaine/morphine/fentanyl spinal anaesthesia

Background: Obesity, abdominal surgery, and intrathecal opioids are all factors associated with a risk for respiratory compromise. The aim of this observational study was to explore the use of portable respiratory polygraphy for monitoring of obese mothers for respiratory depression the first night after caesarean section (CS) with bupivacaine/morphine/fentanyl spinal anaesthesia. Methods: Consecutive obese (BMI >30 kg/m 2) mothers, ≥18 years, scheduled for CS with bupivacaine/morphine/fentanyl spinal anaesthesia were monitored with a portable polygraphy device Embletta /NOX on the first postoperative night. The apnoea-hypopnea index (AHI) was identified by clinical algorithm and assessed in accordance to general guidelines. Results: Forty mothers were invited to participate: 27 consented, 23 were included, but polysomnography registration failed in 3. Among the 20 mothers: 11 had an AHI <5; 7, AHI 5-15; and 2, AHI >15. The oxygen desaturation index (ODI) was on average 4.4, and eight patients had an ODI >5. Those mothers with a high AHI (15.3 and 18.2) did not show high ODI or signs of hypercapnia on transcutaneous CO 2 registration. Mean saturation was 94% (91-96), and four mothers had mean saturation between 90-94%, but none had a mean SpO 2 <90%. Mean nadir saturation was 71% (range, 49-81%).  None of the mothers showed clinical signs or symptoms of severe respiratory depression, shown by routine clinical monitoring. Conclusion: We found portable polygraphy registration during early post-CS in moderately obese mothers having had intrathecal morphine/fentanyl cumbersome and although episodes of oxygen saturation decrease were noticed, obstructive events and episodes of desaturation were commonly not synchronised. Upper airway obstructions seem not be of major importance in this clinical setting. Monitoring of respiratory rate, SpO 2 and possibly transcutaneous CO 2 in mothers at high risk of respiratory distress warrants further studies. Preoperative screening in obese patients, at risk for sleep breathing disorder, is of course of value.

ANALGESIC EFFICACY OF EPIDURAL MORPHINE AND CLONIDINEIN PATIENTS UNDERGOING DECOMPRESSION OF THE LUMBAR CANAL: A PROSPECTIVE RANDOMIZED TRIAL

ABSTRACT Objective: To evaluate the postoperative analgesic efficacy in patients undergoing lumbar canal decompression using epidural morphine and clonidine at the Hospital Santa Casa de Vitória - ES, Brazil. Methods: Prospective, randomized study of 60 patients with stenosis of the lumbar canal up to two levels with surgical indication, in which decompression of the canal was performed in association with lumbar arthrodesis. In group 1 we performed conventional postoperative analgesia and in group 2, in addition to conventional analgesia, we associated epidural morphine and clonidine. We used VAS as a means of analyzing pain intensity at 1, 12, and 36 hours after surgery. The statistical analysis was performed using Microsoft Office/Excel and the software GraphPad Prism (San Diego, CA, USA). Results: The mean age of patients was 47 years, and 52% were female. The mean VAS in the first hour, 12th, and 36th hours after surgery in the control group was 5.44, 2.13, and 0.55 respectively. In the morphine-clonidine group it was 6.96; 2.21 and 0.60. Comparing one group with another in its absolute values through the Mann-Whitney test, as well as comparing the pain variations between the 1st and 12th hour (1h X 12h) and between the 12th hour and 36th hour (12h x 36h ) through Student’s t test it became clear that there was no statistical difference between groups (p > 0.05). Conclusions: The addition of epidural morphine and clonidine to conventional analgesia is not beneficial to reduce postoperative pain in patients undergoing lumbar canal decompression.

Blood acid-base status in impala (Aepyceros melampus) immobilised and maintained under total intravenous anaesthesia using two different drug protocols

BACKGROUND

In mammals, homeostasis and survival are dependent on effective trans-membrane movement of ions and enzyme function, which are labile to extreme acid-base changes, but operate efficiently within a narrow regulated pH range. Research in patients demonstrating a pH shifts outside the narrow regulated range decreased the cardiac output and systemic vascular resistance and altered the oxygen binding to haemoglobin. These cardiopulmonary observations may be applicable to the risks associated with anaesthesia and performance of wildlife ungulates on game farms. The aim of this study was to compare blood pH changes over time in impala immobilised and anaesthetised with two different drug protocols (P-TMP - immobilisation: thiafentanil-medetomidine; maintenance: propofol-ketamine-medetomidine; P-EME - immobilisation: etorphine-medetomidine; maintenance: etorphine-ketamine-medetomidine). Additionally, we discuss the resultant blood pH using both the Henderson-Hasselbalch and the Stewart approaches. Two data collection time points were defined, Time1 before maintenance of general anaesthesia and Time 2 at end of maintenance of general anaesthesia. We hypothesise that blood pH would not be different between drug protocols and would not change over time.

RESULTS

Significant differences were detected over time but not between the two drug protocols. Overall, the blood pH decreased over time from 7.37 ± 0.04 to 7.31 ± 0.05 (p = 0.001). Overall, over time arterial partial pressure of carbon dioxide changed from 51.3 ± 7.5 mmHg to 72.6 ± 12.4 mmHg (p < 0.001); strong ion difference from 44.6 ± 2.4 mEq/L to 46.9 ± 3.1 mEq/L (p < 0.001); anion gap from 15.0 ± 3.1 mEq/L to 10.9 ± 2.2 mEq/L (p < 0.001); and total weak acids from 16.1 ± 1.2 mmol/L to 14.0 ± 1.1 mmol/L (p < 0.001). The bicarbonate changed from 29.6 ± 2.7 mEq/L to 36.0 ± 4.1 mEq/L (p < 0.001); and lactate changed from 2.9 ± 1.5 mEq/L to 0.3 ± 0.03 mEq/L (p < 0.001) over time.

CONCLUSIONS

The profound increase in the partial pressure of carbon dioxide that worsened during the total intravenous anaesthesia in both protocols initiated a substantial metabolic compensatory response to prevent severe acidaemia. This compensation resulted in a clinically acceptable mild acidaemic state, which worsened over time but not between the protocols, in healthy impala. However, these important compensatory mechanisms require normal physiological function and therefore when immobilising ill or anorexic wild ungulates their acid-base status should be carefully assessed.

Transcutaneous Carbon Dioxide Measurements in Women Receiving Intrathecal Morphine for Cesarean Delivery: A Prospective Observational Study

BACKGROUND

Neuraxial morphine is the most commonly used analgesic technique after cesarean delivery. The incidence of respiratory depression is reported to be very low (0%-1.2%) in this patient population as measured by pulse oximetry and respiratory rates. However, hypercapnia may be a more sensitive measure of respiratory depression. In the current study, the incidence of hypercapnia events (transcutaneous CO2 [TcCO2] >50 mm Hg) for ≥2-minute duration was evaluated using the Topological Oscillation Search with Kinematical Analysis monitor in women who received intrathecal morphine for postcesarean delivery analgesia.

METHODS

Healthy women (>37 weeks of gestation) scheduled for a cesarean delivery with spinal anesthesia with intrathecal morphine were recruited. Baseline STOP-BANG sleep apnea questionnaire and TcCO2 readings were obtained. Spinal anesthesia was initiated with 12 mg hyperbaric bupivacaine, 15 µg fentanyl, and 150 µg morphine. The Topological Oscillation Search with Kinematical Analysis monitor was reapplied in the postanesthesia care unit and TcCO2 measurements obtained for up to 24 hours. Supplemental opioid administration and adverse respiratory events were recorded. The primary outcome was the incidence of hypercapnia events, defined as a TcCO2 reading >50 mm Hg for ≥2 minutes in the first 24 hours after delivery.

RESULTS

Of the 120 women who were recruited, 108 completed the study. Thirty-five women (32%; 99.15% confidence interval, 21%-45%) reached the primary outcome of a sustained hypercapnia event. The median time (interquartile range [IQR]) from intrathecal morphine administration to the hypercapnia event was 300 (124-691) minutes. The median (IQR) number of events was 3 (1-6) and longest duration of an event was 25.6 (8.4-98.7) minutes. Baseline median (IQR) TcCO2 measurements were 35 (30-0) mm Hg and postoperatively, median (IQR) TcCO2 measurements were 40 (36-43) mm Hg, a difference of 5 mm Hg (99.15% confidence interval of the difference 2-8 mm Hg, P < .001). The incidence of hypercapnia events was 5.4% in women with a baseline TcCO2 value ≤31 mm Hg, 22.5% with a baseline TcCO2 between 32 and 38 mm Hg, and 77.4% with a baseline TcCO2 >38 mm Hg (P < .001).

CONCLUSIONS

Hypercapnia events (>50 mm Hg for ≥2-minute duration) occurred frequently in women receiving 150 μg intrathecal morphine for postcesarean analgesia. Higher baseline TcCO2 readings were observed in women who had hypercapnia events.

Analysis of Physiological Respiratory Variable Alarm Alerts Among Laboring Women Receiving Remifentanil

BACKGROUND

Remifentanil may be used by laboring women for analgesia, despite controversy because of potential apneas. We evaluated candidate variables as early warning alerts for apnea, based on prevalence, positive predictive rate, sensitivity for apnea event detection, and early warning alert time intervals (lead time) for apnea.

METHODS

We performed a secondary analysis of respiratory physiological data that had been collected during a prospective IRB-approved study of laboring women receiving IV patient-controlled boluses of remifentanil 20 to 60 μg every 1 to 2 minutes. Analyzed data included the respiratory rate (RR), end-tidal CO2 (EtCO2), pulse oximetry (SpO2), heart rate (HR), and the Integrated Pulmonary Index (IPI; Capnostream 20; Medtronic, Boulder, CO) that had been recorded continuously throughout labor. We defined immediate early warning alerts as any drop in a variable value below a prespecified threshold for 15 seconds: RR < 8 breaths per minute (bpm), EtCO2 < 15 mm Hg, and SpO2 < 92%. We defined alerts as "sustained" when the value remained below the threshold for ≥ 10 further seconds. The IPI value (1 to 10; 10 = healthy patient, ≤4 = immediate attention required, 1 = dire condition) was generated from a proprietary algorithm using RR, EtCO2, SpO2, and HR parameters. Apnea was defined as maximal CO2 < 5 mm Hg for at least 30 consecutive seconds.

RESULTS

We counted 62 apneas, among 10 of 19 (52.6%) women who received remifentanil (total dose 1725 ± 1392 μg, administered over 160 ± 132 minutes). We counted 331 immediate early warning alerts for the variables; 271 (82%) alerts were sustained for ≥10 seconds. The positive predictive value of alerts for apnea was 35.8% (99% confidence interval [CI]: 27.1-45.6), 28.9% (99% CI: 20.8-38.7), 4.3% (99% CI: 1.9-9.6), and 24.6% (99% CI: 18.3-32.2) for RR, EtCO2, SpO2, and IPI, respectively. The sensitivity for apnea event detection was 100% (99% CI: 90.3-100) for RR (<8 bpm) and IPI (≤4); 75.8% (99% CI: 59.8-86.9) for EtCO2 <15 mm Hg; and 14.5% (99% CI: 6.5-29.4) for SpO2 <92%. We found a statistically significant difference in the timing of RR, EtCO2, SpO2, and IPI alerts for apnea; Friedman's Q = 33.53; P < .0001. The EtCO2 had a median (interquartile range) lead time of -0.2 (-12.2 to 0.7) seconds, and SpO2 had a median (interquartile range) lead time of 40.0 (40.0 to 40.0) seconds.

CONCLUSIONS

The majority of women receiving IV remifentanil for labor analgesia experienced apneas. Alerts for EtCO2 (<15 mm Hg), RR (<8 bpm), and IPI (≤4) detected most apneas, whereas SpO2 alerts missed the majority of apneas. All variables had a low positive predictive rate, demonstrating the limitations of the respiratory monitors utilized as early warning surveillance for apneas in this setting.

Intrathecal Morphine in Spine Surgery: A Meta-analysis of Randomized Controlled Trials

STUDY DESIGN

Meta-analysis of randomized controlled trials (RCTs).

OBJECTIVE

The aim of this study was to evaluate the effectiveness of intrathecal morphine (ITM) in reducing postoperative pain and opioid analgesic consumption following spine surgery.

SUMMARY OF BACKGROUND DATA

The use of ITM following adult spine surgery is of particular interest because of the ease of access to the thecal sac and the potential to provide adequate analgesia at low doses. However, previous studies of ITM have been limited by small sample sizes and conflicting results.

METHODS

A comprehensive search of PubMed, Web of Science, Clinicaltrials.gov, and the Cochrane Central Register of Controlled Trials for prospective RCTs was performed by two independent reviewers. Postoperative opioid consumption, pain scores, and complications were documented from the identified studies. Standard mean differences (SMDs) were applied to continuous outcomes and odds ratios were determined for dichotomous outcomes.

RESULTS

Eight RCTs involving 393 subjects met inclusion criteria and were included in this meta-analysis. Patients receiving ITM (ITM group) as an adjunct to postoperative opioid analgesic were compared to patients receiving postoperative opioids only (control group). Postoperative morphine equivalent consumption was significantly lower during the first 24 hours postoperative in the ITM group (P < 0.001). Pain scores were similarly lower in the first 24 hours following spine surgery in those who received ITM (P < 0.001). In patients administered ITM, a greater percentage experienced pruritus (P < 0.001). Respiratory depression was solely encountered in the ITM group (P = 0.25). There were no significant differences between the ITM and control groups in terms of sedation (P = 0.18), nausea (P = 0.67), vomiting (P = 0.62), or length of stay (P = 0.13).

CONCLUSION

In patients undergoing spine surgery, use of ITM significantly reduced opioid analgesic consumption and Visual Analogue Schores pain scores compared to controls within the first 24 hours postoperatively. High-quality, follow-up RCTs with large sample sizes are recommended to determine the potential of supplementary ITM in spine surgery and complete the side effects profile.

LEVEL OF EVIDENCE

1.

ETORPHINE-KETAMINE-MEDETOMIDINE TOTAL INTRAVENOUS ANESTHESIA IN WILD IMPALA (AEPYCEROS MELAMPUS) OF 120-MINUTE DURATION

There is a growing necessity to perform long-term anesthesia in wildlife, especially antelope. The costs and logistics of transporting wildlife to veterinary practices make surgical intervention a high-stakes operation. Thus there is a need for a field-ready total intravenous anesthesia (TIVA) infusion to maintain anesthesia in antelope. This study explored the feasibility of an etorphine-ketamine-medetomidine TIVA for field anesthesia. Ten wild-caught, adult impala ( Aepyceros melampus ) were enrolled in the study. Impala were immobilized with a standardized combination of etorphine (2 mg) and medetomidine (2.2 mg), which equated to a median (interquartile range [IQR]) etorphine and medetomidine dose of 50.1 (46.2-50.3) and 55.1 (50.8-55.4) μg/kg, respectively. Recumbency was attained in a median (IQR) time of 13.9 (12.0-16.5) min. Respiratory gas tensions, spirometry, and arterial blood gas were analyzed over a 120-min infusion. Once instrumented, the TIVA was infused as follows: etorphine at a variable rate initiated at 40 μg/kg per hour (adjusted according to intermittent deep-pain testing); ketamine and medetomidine at a fixed rate of 1.5 mg/kg per hour and 5 μg/kg per hour, respectively. The etorphine had an erratic titration to clinical effect in four impala. Arterial blood pressure and respiratory and heart rates were all within normal physiological ranges. However, arterial blood gas analysis revealed severe hypoxemia, hypercapnia, and acidosis. Oxygenation and ventilation indices were calculated and highlighted possible co-etiologies to the suspected etorphine-induced respiratory depression as the cause of the blood gas derangements. Impala recovered in the boma post atipamezole (13 mg) and naltrexone (42 mg) antagonism of medetomidine and etorphine, respectively. The etorphine-ketamine-medetomidine TIVA protocol for impala may be sufficient for field procedures of up to 120-min duration. However, hypoxemia and hypercapnia are of paramount concern and thus oxygen supplementation should be considered mandatory. Other TIVA combinations may be superior and warrant further investigation.

Monitoring for opioid-induced advancing sedation and respiratory depression: ASPMN membership survey of current practice

Adverse events secondary to opioid-induced advancing sedation and respiratory depression continue to occur during hospitalizations despite efforts to increase awareness and clinical practice guidelines to address prevention strategies. In 2009, ASPMN surveyed membership on current practices surrounding this topic. ASPMN clinical practice guidelines were then published in 2011. In winter of 2013, ASPMN membership was again surveyed to assess progress in preventing adverse events. This is a report of the follow-up membership survey. In general, monitoring practices are slowly improving over time, but there are many facilities that have not instituted best practices for avoiding adverse events.

A retrospective assessment of the incidence of respiratory depression after neuraxial morphine administration for postcesarean delivery analgesia

Respiratory depression can occur after neuraxial morphine administration. In the obstetric population, there are little data on respiratory depression after neuraxial morphine administration in women undergoing cesarean delivery. In this single-center, retrospective study in 5036 obstetric patients (mean body mass index = 34 kg/m) who underwent cesarean delivery and received neuraxial morphine, we did not identify any instances of respiratory depression requiring naloxone administration or rapid response team involvement. Therefore, the upper 95% confidence limit for respiratory depression in our study is 0.07% (1 event per 1429 cases).

Highlights in postoperative pain treatment

Acute pain is a symptom that originates from actual ongoing or impending tissue damage. Pain is an individual subjective experience and varies markedly among individuals. For this reason, patient involvement is essential, with the most reliable indicator of severity being patient self-report. The main objective of postoperative pain management is the achievement of fast rehabilitation, recovery of all normal functions and reduction of postoperative morbidity. Sufficient evidence supports the hypothesis that effective analgesia modifies many of the adverse sequelae that accompany acute pain and assists in recovery. Nevertheless, despite the availability of drugs and techniques for its effective management, postoperative pain remains undertreated. It is now accepted that the solution to the problem of inadequate pain relief lies not only in the development of new analgesic drugs or technologies but also in the development of an appropriate organization to utilize existing expertise. Methods used to control postoperative pain are numerous; this review focuses on pharmacological and anesthetic methods.