Patients are at risk for respiratory depression in the perioperative period. The opioids used in both patient controlled analgesia (PCA) and epidural analgesia can cause respiratory depression. The progression of opioid side effects usually starts with sedation, respiratory depression follows and, if left uncorrected, this can lead to respiratory and then cardiac arrest and death. Sedation is a common side-effect, occurring in about 13% of patients and the incidence of respiratory depression varies depending on the precise definition used and the analgesia modality, but it has been reported to occur in about 1% of cases. If you continuously monitor patients with oximetry and capnography the incidence of respiratory depression has been shown to be much higher, as high as 12%8. The incidence of cardiac arrest and death from opioid overdose has been estimated at about 2 cases per 10, 0009. Given that the number of patients undergoing surgery annually is about 100 million worldwide, respiratory depression occurs between 1 and 12 million times and it results in about 20, 000 preventable deaths each year10. The troublesome aspect of this complication is that it often occurs in healthy patients where the family and clinical staff do not anticipate a bad outcome.
The problem of unexpected respiratory depression amongst patients treated with opioids is compounded by the challenge of dealing with obstructive sleep apnea patients in the perioperative period. Obstructive sleep apnea, characterized by the complete or partial obstruction of the upper airway during sleep, is not rare, with about 25% of the general population (and a greater proportion of the surgical population) being at risk for this condition. These patients are at even greater risk of perioperative respiratory events and consequently the guidelines from the American Society of Anesthesiology recommend continuous monitoring of these patients13,14. These guidelines are expert-based as no clinical trials have established the efficacy of continuous monitoring in this population.
These two problems (respiratory depression from opioids and obstructive sleep apnea) have caused significant logistic problems in hospitals as many institutions do not have the equipment to provide continuous monitoring of patients outside of the intensive care units and there is limited capacity in the critical care areas to monitor all the patients at risk.
The impact of respiratory depression can be mitigated if it is recognized early enough and appropriate actions are taken to resuscitate the patient. Early recognition of this complication depends on frequent and regular vital sign assessments by nursing staff.
he problem in many surgical wards is that nursing staff, particularly at night, are spread thin and patients can occasionally go several hours without being seen. In this a period a patient can spiral into trouble from sedation to respiratory depression and eventually into respiratory and cardiac arrest. Previously, cardiac monitoring with telemetry has been available and could be used for patients in the perioperative period. Although telemetry has been proven useful for some groups of patients (including those with an automated defibrillator that has fired, those with a prolonged QT interval and those with acute heart failure) this technology will only pick up cases of respiratory depression that progress into a cardiac event15.
Recently technology has become commercially available to continuously monitor pulse oximetry and notify clinical staff wirelessly via a paging system. The advantage of such a system is that clinicians can be notified immediately when a patient begins to decompensate from respiratory depression within enough time to initiate resuscitation before the patient progresses to respiratory or cardiac arrest. Another benefit of these systems is that patients at risk can be monitored on regular surgical wards without utilizing additional nursing staff. A recent literature search (of MEDLINE) that searched the concepts of respiratory monitoring in the perioperative period (using the MESH keywords: monitoring, oximetry, postoperative period and clinical trial) was conducted to see if there was evidence to support the use of these systems. Only a single study was identified in the search that specifically investigated the postoperative period, a before-after study on a 36-bed orthopedic ward found that a respiratory monitoring system was effective in reducing the need for rescue resuscitations and ICU transfers16. Although there is a Cochrane review on pulse oximetry for perioperative monitoring, this study focused only on intraoperative and recovery room monitoring and did not address monitoring of patients while on surgical wards17.
Given these promising results, a respiratory monitoring will be trialed on two surgical wards at the Juravinski Hospital in Hamilton, Ontario. In order to evaluate the impact of this technology the investigators designed a randomized controlled trial to determine if routine wireless respiratory monitoring for 72 hours of surgical patients on two surgical wards (that care for general surgery, urology and gynecology-oncology patients) reduces the need for rescue resuscitations - Naloxone resuscitation of opioid overdose, Code Blues (Cardio-respiratory arrests) and Intensive Care Unit (ICU) transfers. In addition, this study will also evaluate the risk factors for respiratory depression, the types and duration of respiratory alarms that occur and the impact on nursing workflow.
