Perioperative Management of Opioid-Tolerant Patients
Highlights
- pain management plan for opioid tolerant patients requires careful consideration in the perioperative period in order to (i) prevent opioid withdrawal, (ii) provide effective analgesia, and (iii) to ensure continuity of care in the community after discharge from hospital. (View Highlight)
- Ketamine is recommended in the acute pain management of opioid-tolerant patients as it has been shown to reduce postoperative opioid use and pain scores (View Highlight)
- Activation of the N-methyl-d-aspartate (NMDA) receptor is believed to be one of the mechanisms for the development of opioid tolerance and opioid-induced hyperalgesia (OIH). Ketamine is a non-competitive antagonist of the NMDA receptor and can attenuate both of these phenomena (View Highlight)
- It is generally recommended that the patient's baseline opioid (usually a sustained-release form) is continued in the postoperative period and that acute post-surgical pain is managed with the addition of appropriate doses of IR opioids (View Highlight)
- Direct heat applied to the patch, for example, via perioperative warming devices may enhance drug administration, whereas the use of a patch over an area of poor-perfusion or reduced temperature can reduce drug delivery (View Highlight)
- The use of a buprenorphine patch (up to 70 μg h−1) is unlikely to interfere with the use of full opioid agonists for acute pain management and these should also be continued in the perioperative period (View Highlight)
- In the postoperative period, opioid-tolerant patients may require a greater amount of IR oral opioids than is usually expected. Traditionally, the ‘as required’ (p.r.n.) dose is calculated based on the cumulative oral opioid dose given in the preceding 24 h with one-sixth of the total dose prescribed 4 hourly (View Highlight)
- Rotation can lead to both a reduction in side-effects and an improvement in pain relief because an individual may respond differently to an alternative opioid due to the phenomenon of incomplete cross-tolerance. Cross-tolerance is the observation that exposure to a particular drug (e.g. opioid) results in tolerance to the effects of structurally similar drugs in the same class (e.g. other opioids). When cross-tolerance is incomplete, patients may not have tolerance to the alternative drug. (View Highlight)
- When performing an opioid rotation, it is recommended to reduce the calculated equianalgesic dose by 30–50% because of the possibility of incomplete cross-tolerance. Patients can use additional IR opioids if necessary. (View Highlight)
- A typical strategy for returning to oral medication is to identify the i.v. opioid consumption in the previous 24 h and convert this to an equivalent oral dose. Fifty per cent of this oral equivalent dose is then given in a sustained-release form, and one-sixth of the equivalent dose is prescribed as an IR preparation every 4 h (View Highlight)
- patients with OIH may report more diffuse and widespread pain and ‘sensitivity’ which does not respond to an increase in the dose of opioid. (View Highlight)
- Methadone is typically started (specialist only) at a dose of between 10 and 40 mg, and increased in 10 mg increments (max 30 mg week−1) to a typical maintenance dose of between 60 and 120 mg day−1 (View Highlight)
- Buprenorphine as a maintenance therapy is typically administered as an SL dose between 0.8 and 4 mg (max 32 mg) with typical maintenance doses of between 12 and 24 mg (View Highlight)
- Methadone is a μ**-**agonist as well as an NMDA-antagonist and monoamine reuptake inhibitor. It is metabolized in the liver to inactive metabolites by CYP3A4, which is saturated at low concentrations, and itself also weakly inhibited by methadone (View Highlight)
- OIH was first observed in patients taking methadone for opioid addiction. The underlying mechanism is complex but likely to involve a combination of glial cell activation, NMDA receptor activation, glutaminergic activation, and alterations in opioid intracellular signalling (View Highlight)
- Buprenorphine is a partial agonist at μ**-**receptors, and an antagonist at κ and δ receptors. It has a high affinity for opioid receptors, and dissociates slowly resulting in an extended duration of action. It is used in addiction medicine to suppress opioid withdrawal and craving for 24–48 h, and is less sedating and euphoric (View Highlight)
- It is recommended to stop naltrexone 72 h prior to surgery, and it is important to note that although patients may be resistant to opioids while taking naltrexone, they may then become extremely opioid sensitive once stopping it (View Highlight)