Original contribution
Life-threatening critical respiratory events: a retrospective study of postoperative patients found unresponsive during analgesic therapy

https://doi.org/10.1016/j.jclinane.2010.09.003Get rights and content

Abstract

Study Objective

To identify risk factors for life-threatening critical respiratory events occurring during parenteral analgesic therapy for acute postoperative pain.

Design

Retrospective, observational, cohort study.

Setting

University hospital.

Measurements

The electronic records of patients with sudden-onset, life-threatening critical respiratory events during analgesic therapy for postoperative pain were studied. Critical respiratory event data were identified from the hospital risk management database between 8/1/2000 and 7/31//2007. Patients required rescue treatment with naloxone, endototracheal intubation, or cardiopulmonary resusucitation. Pediatric patients were excluded from the study. In addition to the event description (type of analgesia, opioid dose, patient monitoring data, time of day, and time from surgery), each patient's record was reviewed to extract co-morbidities and outcome data.

Main Results

Over the 6-year period, 32 patients experienced a postoperative critical respiratory event. Twenty-six events and three deaths occurred within the first 24 hours of opioid therapy. Four of 32 patients died. Congestive heart failure, postoperative acute renal failure, obstructive sleep apnea, cardiac dysrhythmia, diabetes mellitus, coronary artery disease, and hypertension were significant associations in adult patients.

Conclusions

The first 24 hours after commencing opioid-based analgesic therapy represents a high risk period. Obstructive sleep apnea, deep levels of sedation, nocturnal presentation, and postoperative acute renal failure were seen in patients who died as a result of these critical respiratory events.

Introduction

Opioids are the mainstay of acute pain management, despite significant side effects that include respiratory depression, which causes alveolar hypoventilation and hypoxemia. Postoperative hypoxemia, defined as oxygen saturation (SpO2) < 90%, is typically multi-factorial and affects 12% to 15% of all patients [1]. While hypoxemia affects large numbers of patients postoperatively, the clinical significance of episodic postoperative hypoxemia is still unknown. In addition, only a small minority of patients with respiratory depression go on to develop a clinically severe respiratory event necessitating rescue intervention [2]. Identifying risk factors for these more serious events constitutes a significant step in advancing perioperative patient safety.

In recent years there has been increasing concern over unmonitored mortality and morbidity in patients during opioid therapy for acute pain [3], [4]. A variety of respiratory monitoring devices have been studied in postoperative patients, including pulse oximetry, capnography, acoustic sensors, and various combinations of each. However, there is a paucity of literature about severe respiratory depression and sudden death during opioid therapy. In this context, we reviewed the risk management incident reporting database at our university hospital for critical respiratory events associated with opioid therapy to treat acute postoperative pain. The purpose of this analysis was to identify risk factors that contribute to adverse outcome during parenteral opioid therapy for acute postoperative pain.

Section snippets

Materials and methods

After obtaining University of Michigan Medical Center Institutional Review Board (IRB) approval, we reviewed the medical records of all patients who were reported to the risk management group of our institution for “respiratory depression”, “respiratory event”, or “respiratory arrest” from August 1, 2000 to July 31, 2007. In addition, postoperative cardiac arrests are automatically referred to the risk management team for root cause analysis, and those deemed on expert review to be related to

Results

A total of 32 LT-CREs were collected over the 6-year evaluation period. An additional 8 cases were excluded for lack of documentation of the critical event, wrong diagnosis, pediatric age group, or those that were associated with death or acute respiratory failure unrelated to opioids. During the same period, 87,650 adult patients were given an anesthetic at our institution. This finding yields a reporting incidence of 3.6 per 10,000 (or 0.038%) adult patients with a LT-CRE during opioid

Discussion

This study describes a low reported incidence of LT-CRE in patients undergoing analgesic therapy after general anesthesia. In patients who develop a postoperative LT-CRE, such an event is more likely to occur in the first 24 hours following surgery and anesthesia. We identified 7 significant co-morbid risk factors, namely, postoperative acute renal failure, OSA, hypertension, CAD, diabetes mellitus, history of CHF, and cardiac dysrhythmia. OSA, hydromorphone therapy, postoperative acute renal

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There are no financial disclosures to be made about this study. This is an internal review of respiratory events in a University hospital.

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