Each week we will aim to bring out a concise email that provides 4-5 key pieces of information addressing a specific issue in clinical therapeutics.
This week: Monitoring for Acute Opioid Toxicities (Part 2)
Chis Alderman, Clinical Director, Ward MM
Opiate toxicity is classically defined as a triad of respiratory depression, central nervous system depression, and miosis. In severe cases, hypotension is also present. Fatalities due to opioid toxicity most commonly result from respiratory arrest, even in young healthy adults.
- It should never be assumed that prior exposure to opioids negates the risk of respiratory depression. Respiratory depression, leading to high blood levels of carbon dioxide, can in fact coexist with a normal respiratory rate. Therefore a decrease in respiratory rate is an unreliable indicator of respiratory depression.
- Sedation is a more sensitive indicator of potential respiratory depression. Apnoea can also occur, particularly during sleep or in the context of concomitant sedatives and general anaesthetics (also alcohol & cannabis). Respiratory rate less than 8 breaths/min (usual rate ranges from 12-20) is a cause for concern, as is sedation score greater than 2.
- Nursing staff are advised to monitor sedation scores both before and after administration of opioids, however, there is variability in sedation score classification used by different institutions. An example of a commonly used scale is provided below.
Sedation score example:
- 0 awake, alert
- 1 mild sedation – easy to rouse
- 2 moderate sedation; easy to rouse but unable to remain awake
- 3 difficult to rouse
An order for naloxone should be available for immediate administration, but does not need to be given in the absence of respiratory depression; precipitation of opioid withdrawal and/or pain crisis is potentially an issue. Note also that the duration of action is 90 minutes for naloxone and that the duration of effect of many opioids may be greater than this, meaning that continued vigilance is needed even after the administration of an opioid antagonist.
Please consider these issues when preparing or interpreting RMMR reports or education sessions. Contributions of content or suggested topics are welcome and should be sent directly to email@example.com.