Anesthetic Concerns in Patients Receiving Preoperative Opioids: a Review
Patients suffering from cancer or non cancer pain syndromes are frequently receiving opioids for pain management in the preoperative period. Anesthesiologist commonly encounters patients on chronic opioids medication for surgery and has to manage behavioral, psychological and pharmacological aspects. It is important for anesthesiologist to know about effects and management of chronic opioids therapy because opioids are an important component of postoperative pain therapy, an adequate opioids dose in the perioperative period should be maintained to prevent opioids withdrawal and it can be challenging to revert to preoperative opioids regimen after surgery .
Peri-operative Management
In patients on long-term opioids, it is essential to identify relevant problems and formulate an appropriate management plan. At present, no data or guidelines are available to predict individual postoperative opioid requirements based on preoperative opioid dose.
Key Factors in Pre-operative Assessment of patient on strong opioids
These patients may be anxious and need to be educated, counselled and reassured. • A detailed history must be taken to get the correct preoperative opioid usage. Some patients may be abusing the opioid drugs and it may be difficult to ascertain the correct opioid doses.
• Baseline pain assessment should be done to monitor the signs of withdrawal.
• Patients requiring >30mg intravenous morphine equivalent per day for over 1 month may develop tolerance.
• Regular doses of opioid and other adjuvant analgesics need to be continued on morning of surgery.
• Patients requirements may increase up to 4 times the baseline in the postoperative period and analgesia may be required for a longer period.
• A dosing less than required may precipitate withdrawal and may be difficult to diagnose in the perioperative period.
- In case oral route is not possible, an alternative drug/ route ( IV, transdermal or epidural) route may be utilised after calculating equivalent dosing
- No single anaesthetic technique can be prescribed to such patients. The anaesthetic technique need to be individualised depending on surgical and patient factors.
- Regional anaesthesia alone or with general anaesthesia improves tissue perfusion and reduces opioid requirement
- Even central opioid receptors are reduced in such patients and an increased dose of the opioids are required form central neuraxial route. Moreover, an additional oral/parenteral administration may be required for satisfactory pain relief [9, 10].
Other Strategies
Patient controlled analgesia
The use of patient controlled analgesia (PCA) can be a good alternative for customized dosing above background opioid therapy in such patients. Depending upon pre- existing patient’s requirement a large bolus on demand may be set and adjusted to effect on an individual basis [10, 11]. This will allow autonomy to the patient and requirement can be reassessed to titrate the effect further.
Regional blocks
Analgesia can be supplemented by local anaesthetics with adjuvant given through peripheral/ central neuraxial blocks [11, 12]. The common blocks that may be used in once surgeries are mentioned in the table.
| S .no | Surgery | Block | ||||||
|---|---|---|---|---|---|---|---|---|
| 1 | Head and Neck | Maxillary and mandibular nerve block | ||||||
| 2 | Thyroid surgery | Superficial and deep cervical nerve block | ||||||
| 3 | Thoracic, breast | Epidural, par vertebral | ||||||
| 4 | Abdominal | Epidural, TAP block |
Multimodal analgesia
In immediate postoperative period nociceptive pain has multiple mechanisms and addition of other analgesics may provide benefit [13]. a) Opioid rotation: patients exhibit inter individual variation in response to different opioids and instead of rapidly escalating the doses of opioids, switching to an alternative strong opioids in equianalgesic doses may be beneficial. This opioid rotation improves pain relief in up to 50% of patients.
b) Ketamine: is NMDA receptor antagonist and helps in reversing opioid tolerance. It may be given as a continuous infusion (5-15 mg/hr) in the immediate pre-operative period and continued for 24-48 hours post-operatively [14, 15]. Patients on Ketamine should be monitored for hallucinations (50% incidence) and other vital parameters on regular basis.
c) Clonidine is an agonist at the Alpha-2 adrenoceptor. It
augments the effects of opioid drugs, decreases opioid withdrawal reactions and reduces the neurohumeral stress response to surgery. It may be given by the intravenous or epidural route in the dose of 1-2 mcg/kg peri-operatively to enhance analgesia.
d) Paracetamol and NSAID’s are simple analgesics sand have significant opioid sparing effects. In absence of any contra-indications, all patients should receive them in the immediate postoperative period [13].
e) Gabapentin is an anticonvulsant that acts upon the α2δ subunit of calcium channels and at the GABAB receptor. Gabapentin in doses of either 600 or 900mg pre-operatively reduces morphine requirements and its side-effects such as nausea and vomiting in the post-operative period.
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Bacon DR, Peppriell J, et al. (1993) A comparison of postoperative epidural analgesia between patients with chronic cancer taking high doses of oral opioids versus opioid-naive patients. Anesth Analg 76(2): 302-307.
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Curatolo M (2003) Combinations of morphine with ketamine for patient-controlled analgesia. Anesthesiology 98(5): 1195-1205.
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17. Cheol Lee, Hyun-Wook Lee, and Ji-Na Kim (2013)
Effect of oral pregabalin on opioid-induced
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