Ensuring that patient-controlled anaesthesia is safe

Abstract

Pain is now regarded as the “fifth vital sign” and pain relief to be a basic human right. Patient-controlled anaesthesia (PCA) is effective because it enables self-titration to individual requirements. PCA is perceived to be inherently safe because of the lockout interval, and because sedation purportedly stops the patient from pressing the button. Nevertheless, because of respiratory depression, increasing numbers of adverse events are serious cause for concern. Respiratory depression comprises three components: central respiratory depression, airway obstruction and sedation. Together, these effects result in opioid-induced respiratory impairment (OIVI). Strategies for safety improvement include an understanding of opioid pharmacokinetics and pharmacodynamics, appropriate dosing regimens, establishing guidelines and written orders, appropriate monitoring and record-keeping, staff training for PCA competency, preoperative patient education and oxygen administration when appropriate, e.g. sleeping patients. Initial postoperative analgesia should be established personally by the attending practitioner who should titrate small doses of opioid to the desired effect. It is emphasised that counting breathing rates is an unreliable index of OIVI is that the quality of breathing should be assessed, and that sedation occurs before OIVI, is clinically obvious. Therefore, monitoring and recording a sedation score at regular intervals is essential. During opioid administration, sedation should be regarded as the “sixth vital sign”.