Search

Prescription opioid use has risen steeply for over two decades, driven primarily by advocacy for better management of chronic non-cancer pain, but also by poor opioid stewardship in the management of acute pain. Inappropriate prescribing, among other things, contributed to the opioid 'epidemic' and striking increases in patient harm. It has also seen a greater proportion of opioid-tolerant patients presenting to acute care hospitals. Effective and safe management of acute pain in opioid-tolerant patients can be challenging, with higher risks of opioid-induced ventilatory impairment and persistent post-discharge opioid use compared with opioid-naive patients. There are also increased risks of some less well known adverse postoperative outcomes including infection, earlier revision rates after major joint arthroplasty and spinal fusion, longer hospital stays, higher re-admission rates and increased healthcare costs. Increasingly, opioid-free/opioid-sparing techniques have been advocated as ways to reduce patient harm. However, good evidence for these remains lacking and opioids will continue to play an important role in the management of acute pain in many patients.Better opioid stewardship with consideration of preoperative opioid weaning in some patients, assessment of patient function rather than relying on pain scores alone to assess adequacy of analgesia, prescription of immediate release opioids only and evidence-based use of analgesic adjuvants are important. Post-discharge opioid prescribing should be contingent on an assessment of patient risk, with short-term only use of opioids. In partnership with pharmacists, nursing staff, other medical specialists, general practitioners and patients, anaesthetists remain ideally positioned to be involved in opioid stewardship in the acute care setting.

Over recent years there has been a growing need for patients to be sent home from hospital with prescribed opioids for ongoing management of their acute pain. Increasingly complex surgery is being performed on a day-stay or 23-hour-stay basis and inpatients after major surgery and trauma are now discharged at a much earlier stage than in the past. However, prescription of opioids to be self-administered at home is not without risk. In addition to the potential for acute adverse effects, including opioid-induced ventilatory impairment and impairment of driving skills, a review of the literature shows that opioid use continues in some patients for some years after surgery. There are also indications that over-prescription of discharge opioids occur with a significant amount not consumed, resulting in a potentially large pool of unused opioid available for later use by either the patient or others in the community. Concerns about the potential for harm arising from prescription of opioids for ongoing acute pain management after discharge are relatively recent. However, at a time when serious problems resulting from the non-medical use of opioids have reached epidemic proportions in the community, all doctors must be aware of the potential risks and be able to identify and appropriately manage patients where there might be a risk of prolonged opioid use or misuse. Anaesthetists are ideally placed to exercise stewardship over the use of opioids, so that these drugs can maintain their rightful place in the post-discharge analgesic pharmacopoeia.

The number of patients in buprenorphine opioid substitution therapy (BOST) or methadone opioid substitution therapy (MOST) programs is increasing. If these patients require surgery, it is generally agreed that methadone should be continued perioperatively. While some also recommend that buprenorphine is continued, concerns that it may limit the analgesic effectiveness of full mu-opioid agonists have led others to suggest that it should cease before surgery. However, no good evidence exists for either course of action. Therefore, we undertook a retrospective cohort study comparing pain relief and opioid requirements in the first 24 hours after surgery in 22 BOST and 29 MOST patients prescribed patient-controlled analgesia. There were no significant differences in pain scores (rest and movement), incidence of nausea or vomiting requiring treatment, or sedation between the BOST and MOST patient groups overall, or between those patients within each of these groups who had and had not received their methadone or buprenorphine the day after surgery. There were also no significant differences in patient-controlled analgesia requirements between BOST and MOST patient groups overall, or between patients who did or did not receive MOST on the day after surgery. BOST patients who were not given their usual buprenorphine the day after surgery used significantly more patient-controlled analgesia opioid (P=0.02) compared with those who had received their dose. These results confirm that continuation of buprenorphine perioperatively is appropriate.

This study aimed to characterise and compare the absorption pharmacokinetics of a single subcutaneous dose of oxycodone in critically ill patients and healthy subjects. Blood samples taken at intervals from two minutes to eight hours after a subcutaneous dose of oxycodone in patients (5 mg) and healthy volunteers (10 mg) were assayed using high performance liquid chromatography. Data were analysed using a non-compartmental approach and presented as mean (SD). Parameters were corrected for dose differences between the groups assuming linear kinetics. Ten patients (eight male, two female) and seven healthy male subjects were included. Maximum venous concentration and area under the concentration curve were approximately two-fold lower in the patient group for an equivalent dose, suggesting either reduced bioavailability or increased clearance: maximum venous concentration 0.14 ± 0.06 vs 0.05 ± 0.02 µg/ml (P <0.0001); area under the concentration curve 19.50 ± 9.15 vs 9.72 ± 2.71 µg/ml/minute (P <0.001) respectively. However, time to maximum venous concentration and mean residence time were not different, suggesting similar absorption rates: time to maximum venous concentration 22.10 ± 18.0 vs 20.50 ± 16.10 minutes (P=0.81); mean residence time 353 ± 191 vs 291 ± 80 minutes (P=0.26). Kinetic parameters were less variable in patients than in volunteers. The patients therefore had reduced exposure to subcutaneous oxycodone. This warrants further model-based analysis and experimentation. Dose regimens for subcutaneous oxycodone developed in healthy volunteers cannot be directly translated to critically ill patients.

In Australia and New Zealand, in parallel with other developed countries, the number of patients prescribed opioids on a long-term basis has grown rapidly over the last decade. The burden of chronic pain is more widely recognised and there has been an increase in the use of opioids for both cancer and non-cancer indications. While the prevalence of illicit opioid use has remained relatively stable, the diversion and abuse of prescription opioids has escalated, as has the number of individuals receiving methadone or buprenorphine pharmacotherapy for opioid addiction. As a result, the proportion of opioid-tolerant patients requiring acute pain management has increased, often presenting clinicians with greater challenges than those faced when treating the opioid-naïve. Treatment aims include effective relief of acute pain, prevention of drug withdrawal, assistance with any related social, psychiatric and behavioural issues, and ensuring continuity of long-term care. Pharmacological approaches incorporate the continuation of usual medications (or equivalent), short-term use of sometimes much higher than average doses of additional opioid, and prescription of non-opioid and adjuvant drugs, aiming to improve pain relief and attenuate opioid tolerance and/or opioid-induced hyperalgesia. Discharge planning should commence at an early stage and may involve the use of a 'Reverse Pain Ladder' aiming to limit duration of additional opioid use. Legislative requirements may restrict which drugs can be prescribed at the time of hospital discharge. At all stages, there should be appropriate and regular consultation and liaison with the patient, other treating teams and specialist services.

Despite the increasing use of a variety of different analgesic strategies, opioids continue as the mainstay for management of moderate to severe acute pain. However concerns remain about their potential adverse effects on ventilation. The most commonly used term, respiratory depression, only describes part of that risk. Opioid-induced ventilatory impairment (OIVI) is a more complete term encompassing opioid-induced central respiratory depression (decreased respiratory drive), decreased level of consciousness (sedation) and upper airway obstruction, all of which, alone or in combination, may result in decreased alveolar ventilation and increased arterial carbon dioxide levels. Concerns about OIVI are warranted, as deaths related to opioid administration in the acute pain setting continue to be reported. Risks are often said to be higher in patients with obstructive sleep apnoea. However, the tendency to use the term 'obstructive sleep apnoea' to encompass the much broader spectrum of sleep- and obesity-related hypoventilation syndromes and the related misuse of terminology in papers relating to obstructive sleep apnoea and sleep-disordered breathing remain significant problems in discussions of opioid-related effects. Opioids given for management of acute pain must be titrated to effect for each patient. However strategies aiming for better pain scores alone, without highlighting the need for appropriate monitoring of OIVI, can and will lead to an increase in adverse events. Therefore, all patients must be monitored appropriately for OIVI (at the very least using sedation scores as a '6th vital sign') so that it can be detected at an early stage and appropriate interventions triggered.

We conducted a retrospective audit of adult non-obstetric patients who had received a single dose of intrathecal morphine for postoperative analgesia. These patients were predominantly admitted to a regular postsurgical ward with strict hourly nursing observations, treatment protocols in place and supervision by an Acute Pain Service for the first 24 hours after intrathecal morphine administration. A total of 409 cases were examined for sedation score, incidence of respiratory depression and other side-effects, admission to the high dependency or intensive care unit and opioid-tolerance. Respiratory depression was defined as requiring treatment with naloxone (implying a sedation score of 3 irrespective of respiratory rate), or a sedation score of 2 with a respiratory rate less than six breaths per minute. The patients were predominantly elderly (57.2% were over the age of 70 years) and 84.8% had undergone vascular surgery. Of the total of 409 cases, only one case of respiratory depression was observed. A total of 77 patients were admitted to high dependency or intensive care unit for various reasons including management of postsurgical complications and patient co-morbidities. Our findings suggest that elderly patients who receive intrathecal morphine analgesia can be safely managed in a regular postsurgical ward.