Opioid-Induced Sedation in the Postanesthesia Care Unit Does Not Insure Adequate Pain Relief: A Case-Control Study

Pupillary unrest, opioid intensity, and the impact of environmental stimulation on respiratory depression

Opioid-induced respiratory depression (OIRD) confers significant morbidity, but its onset can be challenging to recognize. Pain or stimulation effects of conversation may mask or attenuate common clinical manifestations of OIRD. We asked whether pupillary unrest could provide an objective signal of opioid exposure, and whether this signal would be independent from the confounding influence of extrinsic stimulation. We conducted a cross-over trial of healthy volunteers using identical remifentanil infusions separated by a washout period; in both, pupillary unrest in ambient light (PUAL) was measured at 2.5-min intervals. During one infusion, investigators continuously engaged the subject in conversation, while in the other, a quiet environment was maintained; measures of respiratory depression were compared under each condition. We tested PUAL’s relationship to estimated opioid concentration under quiet conditions, measured PUAL’s discrimination of lower versus higher opioid exposure using receiver operating characteristic (ROC) analysis, and assessed the effect of stimulation on PUAL versus opioid using mixed effects regression. Respiratory depression occurred more frequently under quiet conditions (p < 0.0001). Under both conditions, PUAL declined significantly over the course of the remifentanil infusion and rose during recovery (p < 0.0001). PUAL showed excellent discrimination in distinguishing higher versus absent-moderate opioid exposure (AUROC = 0.957 [0.929 to 0.985]), but was unaffected by interactive versus quiet conditions (mean difference, interactive – quiet = − 0.007, 95% CI − 0.016 to 0.002). PUAL is a consistent indicator of opioid effect, and distinguishes higher opioid concentrations independently of the stimulating effects of conversational interaction. Under equivalent opioid exposure, conversational interaction delayed the onset and minimized the severity of OIRD.

Clinical trial registration: NCT 04301895

A randomized control trial to compare thoracic epidural with intercostal block plus intravenous morphine infusion for postoperative analgesia in patients undergoing elective thoracotomy

Objective

The objective of the study is to compare the efficacy of Thoracic epidural with Intercostal block plus intravenous morphine infusion for postoperative analgesia in patients undergoing elective thoracotomy.

Methodology and Design

This study is designed as a prospective randomized clinical trial. Setting: Christian Medical College Hospital, Vellore, India.

Participants

Patients undergoing elective thoracic surgery through posterolateral thoracotomy.

Intervention

In Group A (TEA) patients epidural catheter was inserted at T5-6 level before induction of GA and analgesia was activated using 0.25% of bupivacaine towards the end of the surgery, before chest closure and infusion of 0.1% bupivacaine with 2 mcg/ml of fentanyl was started. In Group B (ICN) patients, an intercostal blockade of the 5 intercostal spaces was performed by the surgeon just before chest closure using 0.25% bupivacaine and a continuous intravenous morphine infusion of 0.015-0.02 mg/kg/hr was started.

Measurements

Assessment of resting and dynamic pain intensity using Numerical rating scale and sedation using Ramsay sedation scale was done and recorded at 1, 6,12,18,24 hours during the first postoperative day. The other parameters that were measured include side effects and the requirement of rescue analgesia. Results: Resting and Dynamic (NRS) pain scores were less in Group A (TEA) than Group B (ICN). In the first 12 hours, the differences in both the resting (P = 0.0505) and dynamic (P = 0.0307) pain scores were statistically significant. By the end of the first postoperative day, sedation scores were more or less similar in both groups. The incidence of side effects and requirement of rescue analgesia were found to be similar in both the groups.

Conclusion

To summarize, though the results show a slightly better quality of analgesia with the thoracic epidural, the difference being clinically insignificant intercostal blockade could be considered as a valid alternative.

Optimal Pain Control in Abdominal Wall Reconstruction

Lack of physician familiarity with alternative pain control strategies is a major reason why opioids remain the most commonly used first-line treatment for pain after surgery. This is perhaps most problematic in abdominal wall reconstruction, where opioids may delay ambulation and return of bowel function, while negatively affecting mental status. In this article, we discuss multimodal strategies for optimal pain control in abdominal wall reconstruction. These strategies are straightforward and are proven to improve pain control while minimizing opioid-associated side effects.

Pupillary Unrest in Ambient Light and Prediction of Opioid Responsiveness: Case Report on Its Utility in the Management of 2 Patients With Challenging Acute Pain Conditions

Pupillary unrest in ambient light (PUAL), the normal pattern of pupil diameter fluctuation present in awake humans, has been proposed as a marker of central opioid effect. We report 2 cases in which PUAL identified the appropriate pain management for 2 patients, each with unique, challenging acute pain conditions. In both cases, PUAL accurately predicted opioid responsiveness, suggesting an effective, individualized analgesic approach for both patients.

Prediction of Opioid Analgesic Efficacy by Measurement of Pupillary Unrest

BACKGROUND

Pupillary unrest under ambient light (PUAL) is the fluctuation in pupil diameter in time around a mean value. PUAL is augmented by light and diminished by administration of opioids. We hypothesized that, because pupillary unrest is a marker of opioid effect, low levels of PUAL may be associated with reduced opioid efficacy, as measured by changes in the numerical rating scale (NRS) pain scores of patients in the postanesthesia care unit (PACU).

METHODS

We used an infrared pupillometer to measure PUAL in patients recovering from ambulatory surgery at 2 different institutions. At both sites, PUAL was quantified using spectral analysis of the Fourier transform of pupil diameter versus time. We measured PUAL and pain scores before and after opioid administration. Protocols for total capture time and lighting conditions varied between the 2 sites. Correlations between PUAL and change in NRS scores were examined using significance testing of Pearson correlation coefficients. Correlations between change in PUAL and change in NRS scores were also examined. Patients were divided into high and low PUAL groups, and high and low response to opioid. A Fisher exact test was used to determine whether there was a significant association between PUAL and opioid response.

RESULTS

For patients with pain in the PACU, low levels of pupillary unrest before opioid therapy were associated with minimal or no reduction in pain scores after opioid administration. We noted a significant correlation at both sites between PUAL and pain score reduction with opioids (r = 0.59, P = .0053, and r = 0.57, P = .022.) The Fisher exact test confirmed that patients with PUAL levels above the mean had a more beneficial analgesic effect from opioids than those with low PUAL levels (P = .018). We also noted that change in PUAL was significantly correlated with change in pain score at both sites (r = 0.56, P = .03 and r = 0.55, P = .01).

CONCLUSIONS

We observe that the pretreatment magnitude of PUAL is correlated with the analgesic response to opioid therapy, and that patients who exhibit higher levels of PUAL change after opioid administration have a more beneficial analgesic effect from opioids. Larger studies with uniform measurement protocols are required to confirm these preliminary results.

Comparison between intravenous paracetamol and fentanyl for intraoperative and postoperative pain relief in dilatation and evacuation: Prospective, randomized interventional trial

Background and Aims:

Dilatation and Evacuation procedure involves pain, for which pain control measures need to be undertaken. The purpose of this study was to compare paracetamol with fentanyl for pain relief in dilatation and curettage procedures.

Materials and Methods:

Sixty female patients were randomly included during the period from March 1, 2012 to February 28, 2013. All patients had received oral midazolam 7.5 mg as a premedication 30 min before procedure in the ward. Group P had received intravenous (IV) paracetamol 15 mg/kg in the waiting area of the operating room 15 min before starting the procedure. Group F had received IV fentanyl 2 ug/kg/min at induction of anesthesia. Pain scores on a numerical rating scale at 5, 15, and 30 min intervals after surgery were recorded.

Results:

Mild pain was commonly observed in both groups, an insignificant difference between groups.

Conclusion:

The study demonstrates the usefulness of IV paracetamol which may be as effective as fentanyl in dilation and curettage procedures.

Nonopioid versus opioid based general anesthesia technique for bariatric surgery: A randomized double-blind study

OBJECTIVE

The objective of this study was to evaluate the efficacy and safety of giving general anesthesia without the use of any opioids either systemic or intraperitoneal in bariatric surgery.

METHODS

Prospective randomized controlled trial. Obese patients (body mass index >50 Kg/m(2)) undergoing laparoscopic sleeve gastrectomies were recruited and provided an informed signed consent. Patients were randomized using a computer generated randomization table to receive either opioid or non-opioid based anesthesia. The patient and the investigator scoring patient outcome after surgery were blinded to the anesthetic protocol. Primary outcomes were hemodynamics in the form of "heart rate, systolic, diastolic, and mean arterial blood pressure" on induction and ½ hourly thereafter. Pain monitoring through visual analog scale (VAS) 30 min after recovery, hourly for 2 h and every 4 h for 24 h was also recorded. Pain monitoring through VAS and post-operative nausea and vomiting 30 min after recovery were also recorded and finally patient satisfaction and acute pain nurse satisfaction.

RESULTS

There was no difference in background characteristics in both groups. There were no statistically significant differences in different outcomes as heart rate, mean blood pressure, O2 saturation in different timings between groups at any of the determined eight time points but pain score and nurse satisfaction showed a trend to better performance with non-opioid treatment.

CONCLUSION

Nonopioid based general anesthesia for Bariatric surgery is as effective as opioid one. There is no need to use opioids for such surgery especially that there was a trend to less pain in non-opioid anesthesia.

Practice trends in use of morphine for control of intraoperative pain: An audit

Background:

When using morphine as the sole analgesic during conduct of anesthesia, the fear of its adverse postoperative effects primarily sedation and respiratory depression may impede adequate dosing and analgesia.

Aim and Objectives:

This audit aims to explore the dosing schedules of morphine used during general anesthesia in our institution and to analyze whether the fear of major side effects leads to suboptimal dosing of morphine with inadequate pain relief.

Materials and Methods:

All subjects scheduled for surgery under general anesthesia wherein morphine was used exclusively for intraoperative analgesia were included in the audit. The audit proforma was completed by the attending anesthesiologist wherein the study period extended from beginning of anesthesia to immediate postoperative period.

Result:

The study population comprised of 158 patients having mean age 33 ± 14 years and mean weight 52 ± 14 kg. The dose of morphine administered at induction varied widely from 0.05 to 0.3 mg/kg i.v. The VAS (Visual Analogue Scale) score in immediate postoperative period varied from 0 to 10 (mean 1.7 ± 2.0) and sedation score from 1 to 5 (mean 3.94 ± 1.05). Inadequate analgesia with a VAS score ≥4 was seen in 15% patients. Morphine dosage of >0.1 mg/kg was associated with highly significant increase in quality of postoperative analgesia with VAS score <4, and an increase in sedation with sedation score ≤3 (P value < 0.01). However, none of the patients required active intervention for cardiorespiratory support.

Conclusion:

The practice of dosing morphine in our institution is highly variable with doses ranging from 0.05 to 0.3 mg/kg. This results in inadequate analgesia in 15% patients in postoperative period. Titrating the dose of morphine to expected pain levels inflicted upon by surgical procedures may result in better pain control and less sedated patients postoperatively.

The associations between OPRM 1 and COMT genotypes and postoperative pain, opioid use, and opioid-induced sedation

Previous studies have associated mu-opioid receptor (OPRM1) genotype with pain and analgesia responses in postoperative and patient populations. This study investigates the role of catechol-O-methyltransferase (COMT) and OPRM1 genotypes in acute postoperative pain scores, opioid use, and opioid-induced sedation after surgical procedures for orthopedic trauma in an otherwise healthy patient population. Verbal pain/sedation scores, opioid use, and physiologic responses in the immediate postoperative period were examined for association with genetic variants in Caucasians genotyped for OPRM1 single nucleotide polymorphisms (SNPs) A118G and C17T and COMT SNPs. The OPRM1 A118G genotype was associated with patients' postoperative Numerical Pain scale (NPS) ratings at 15 min in the postanesthesia care unit (PACU) (p = .01) and patients' sedation scores at 15 min in the PACU (p = .02). COMT genotype (rs4818) was associated with opioid consumption in the first 45 min in the PACU (p = .04). NPS ratings at 45 min were also higher in the group of patients with A/A genotype of rs4680 than in patients with the other two genotypes at this SNP (p = .03). Our haplotype trend analysis identified a COMT haplotype "GCGG" significantly associated with NPS at 15 min (p = .0013), amount of opioids consumed in the first 45 min (p = .0024), and heart rate at 45 min in the PACU (p = .017). The results indicate that genetic variations in COMT contribute to the acute postoperative pain and analgesia responses and physiologic responses in this group of otherwise healthy postoperative orthopedic trauma patients.

Trend of analgesic consumption and pain scores in the post anesthetic care unit (A 9-year survey in surgical cancer patients)

As part of a quality assurance program, we assessed the trend of our analgesic consumption using our anesthesia database which include anesthesia and postanesthetic care records for all patients. In recent years, emphasis was made on anesthesia personnel to decrease postoperative opioid analgesic at the expense of non-opioid analgesics in order to decrease opioid related side effects. The following items were recorded: intraoperative opioid consumption, total morphine consumption, non-opioid analgesic consumption pain and sedation scores in the postoperative care unit (PACU). The database consisted of 57,967 patients for 9 consecutive years from 2002 to 2010, mean data exhaustivity was of 95%. Total morphine consumption per patient in the operative room and in the PACU decreased significantly from 11 ± 4 mg in year 2002 to 7 ± 3 mg in 2010, P < 0.05. In the intraoperative period, remifentanil/sufentanil ratio increased significantly from 33/67 to 87/13% of patients (P < 0.05) without affecting pain scores in the PACU. This multi-year trend shows a significant decrease in overall postoperative morphine consumption, in addition we showed that computerized database can easily follow the trend of analgesic consumption and can be used therefore as a powerful tool with easy access as part of a quality assurance program.

Incidence of severe postoperative pain after cancer surgery despite intraoperative anticipation: a case controlled study

BACKGROUND AND METHODS

Anticipating postoperative pain is a routine practice in our institution. As part of a quality assurance program we used our computerized anesthetic record system database to evaluate incidence of patients having very severe postoperative pain (grade 4 on a subjective pain scale ranging from 0 to 4) in the Post Anesthetic Care Unit during a two year period. These patients were compared to a control group matched on age, type and date of surgery. Demographic characteristics, type and duration of the surgery, preoperative and intra-operative medications were compared between groups.

RESULTS

78 patients out of 12,510 (0.6%) with a pain score of 4 were compared to another group of 78. No significant difference was observed with regards of demographic characteristics, duration, type of surgery, and operative pain medications. Pain scores and morphine consumption were significantly higher in the cases study group in comparison to the controlled group, 4 vs 1.6+/-1.1, (p<0.05) and 13.2+/-6 vs. 6.9+/-7mg (p<0.05). Patients in the cases study group had significantly more preoperative psychoactive medication: antidepressant and benzodiazepine 13 vs. 2, (p<0.05).

CONCLUSION

The incidence of severe postoperative pain scores were less than 1% in our institution. In patients with preoperative opioid treatment, adaptation of analgesic treatment has probably prevented the occurrence of severe pain. Multimodal anticipation of postoperative pain should remain mandatory while efforts should focus to identify such patients before surgery.

Transition from acute to chronic postsurgical pain: risk factors and protective factors

Most patients who undergo surgery recover uneventfully and resume their normal daily activities within weeks. Nevertheless, chronic postsurgical pain develops in an alarming proportion of patients. The prevailing approach of focusing on established chronic pain implicitly assumes that information generated during the acute injury phase is not important to the subsequent development of chronic pain. However, a rarely appreciated fact is that every chronic pain was once acute. Here, we argue that a focus on the transition from acute to chronic pain may reveal important cues that will help us to predict who will go on to develop chronic pain and who will not. Unlike other injuries, surgery presents a unique set of circumstances in which the precise timing of the physical insult and ensuing pain are known in advance. This provides an opportunity, before surgery, to identify the risk factors and protective factors that predict the course of recovery. In this paper, the epidemiology of chronic postsurgical pain is reviewed. The surgical, psychosocial, socio-environmental and patient-related factors that appear to confer a greater risk of developing chronic postsurgical pain are described. The genetics of chronic postsurgical pain are discussed with emphasis on known polymorphisms in human genes associated with chronic pain, genetic studies of rodent models of pain involving surgical approaches, the importance of developing accurate human chronic postsurgical pain phenotypes and the expected gains for chronic postsurgical pain medicine in the post-genomic era. Evidence is then reviewed for a preventive multimodal analgesic approach to surgery. While there is some evidence that chronic postsurgical pain can be minimized or prevented by an analgesic approach involving aggressive perioperative multimodal treatment, other studies fail to show this benefit. The transition of acute postoperative pain to chronic postsurgical pain is a complex and poorly understood developmental process, involving biological, psychological and social-environmental factors.