Clinical Review
Perioperative management of patients taking treatment for chronic pain
Cite this as:
BMJ
2012;345:e4148
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In their otherwise comprehensive review, Farrell and McConaghy omit to specifically discuss the management of spinal or epidural anaesthesia in patients with implanted spinal cord stimulators (SCS) or intrathecal drug delivery systems (ITDDS). As we have noted elsewhere, great care should be taken if a neuraxial block is considered, as there is a risk of damaging the SCS electrode or ITDDS catheter. However, if necessary, then it is advisable to undertake the neuraxial block utilizing fluoroscopic or ultrasound guidance to minimise this risk.[1] Inserting an epidural catheter for post-operative analgesia in a patient with a SCS in-situ also runs the risk of dislodgement or infection of the SCS electrode, in our opinion. The authors state the risks of using diathermy in patients with implanted SCS electrodes, but omit to mention that unipolar diathermy should be avoided where possible. If its use is unavoidable, the reference plate should be positioned to ensure that the SCS components are outside the electrical field of the diathermy. [2]
References:
1. Raphael JH, Mutagi HS, Kapur S. Spinal Cord Stimulation and its anaesthetic implications. British Journal of Anaesthesia Continuing Education in Anaesthesia, Critical Care & Pain 2009; 9(3): 78-81
2. Spinal cord stimulation for the management of pain: recommendations for best clinical practice. British Pain Society,2009.www.britishpainsociety.org/pub_professional.htm
Competing interests: None declared
Dudley NHS Trust, Department of Anaesthesia, Russells Hall Hospital, Dudley, DY1 2HQ
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Farrell and McConaghy highlight the difficulties in the acute pain management of patients with chronic pain. Although they discuss many pain medications, the advice around opioid prescribing to these patients is misleading.
As they suggest, patients on long-term opioids are likely to require higher doses of opioids post-operatively with a tolerance to some side effects but, rather than display tolerance to sedation, these patients often experience a higher incidence of sedation despite greater pain scores compared to opioid-naïve patients. [1] Conversely, if the surgery is expected to reduce their pain, or if a local anaesthetic technique has been employed as a component of multi-modal analgesia, patients on long-term opioids may become acutely sensitive to their usual opioid dose. [2] The authors’ statement that “In such patients, a doubling or quadrupling of the morphine dose… may be needed” thus requires clarification. It is usually recommended that opioids are prescribed in divided doses to assess effect, or given via patient-controlled analgesia at lower than calculated doses initially to allow upward titration. Huxtable and MacIntyre provide a useful review of the management of opioid-tolerant patients. [3]
Fentanyl patches should not be continued in the peri-operative period unless the clinician is confident that there will be no significant fluid shifts leading to hypovolaemia and peripheral vasoconstriction; no sweating affecting the adhesion of the patch; and no pyrexia either through infection or due to a patient warming device; all of which will provide unreliable absorption of the fentanyl. [4]
In box 2, fentanyl tablets and lozenges are wrongly listed as oral preparations. Fentanyl lozenges are designed for sublingual absorption as the bioavailability across the oral mucosa is higher than that after gastrointestinal absorption [5]. Ketamine is listed as an opioid both in box 2 and in the drug conversion chart. It is not an opioid but an NMDA (N-methyl-D-aspartate) receptor antagonist.
The table detailing the impact of renal and hepatic compromise on analgesic metabolism is misleadingly incomplete and fails to mention morphine, which should be avoided in renal failure owing to the accumulation of active metabolites.[6] Oxycodone is often a better choice.
This is an important topic, but the review is let down by inaccuracies and misleading recommendations.
References:
1. Rapp SE, Ready LB, Nessly ML. Acute pain management in patients with prior opioid consumption: A case-controlled retrospective review. Pain. 1995; 61:195–201.
2. Mitra S, Sinatra RS. Perioperative management of acute pain in the opioid-dependent patient. Anesthesiology 2004; 101: 212–27.
3. Huxtable CA, Roberts LJ, Somogyi AA, MacIntyre PE. Acute pain management in opioid-tolerant patients: a growing challenge. Anaesth Intensive Care. 2011;39(5):804-23
4. Richebe P, Beaulieu P. Perioperative pain management in the patient treated with opioids: Continuing professional development. Can J Anaesth. 2009;56:969–81.
5. Streisand JB, Varvel JR, Stanski DR, Le Maire L, Ashburn MA, Hague BI, Tarver SD, Stanley TH. Absorption and bioavailability of oral transmucosal fentanyl citrate. Anesthesiology. 1991;75:223-229
6. Murtagh FE, Chai MO, Donohoe P, Edmonds PM, Higginson IJ. The use of opioid analgesia in end-stage renal disease patients managed without dialysis: recommendations for practice. J Pain Palliat Care PharmacoTher. 2007;21(2):5-16.
Competing interests: None declared
Oxford University Hospitals Trust, John Radcliffe Hospital, Headley Way, Oxford, OX3 9DU
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Farrell and McConaghy's otherwise comprehensive review implies that spinal cord stimulators and intrathecal drug delivery systems are the only neuroprostheses likely to be found in patients with chronic pain. Other important devices regularly implanted by neurosurgeons to treat chronic pain include the intracranial therapies of deep brain stimulation and motor cortex stimulation, and peripheral nerve stimulation. All should be implanted in centres with sufficient expertise willing to audit outcomes.(1)
The principles of perioperative care for patients with intracranial neurostimulation remain as the authors describe for spinal cord stimulation with the devices needing to be switched off during surgery. However, pulse generators are usually implanted in the subclavicular thorax rather than the abdomen and should be palpated there before surgery and not mistaken for a cardiac pacemaker or implanted defibrillator. Electrocardiogram electrodes should not be placed over thoracic pulse generators.
The authors should also clarify the use of diathermy in patients with implanted neurostimulators. Monopolar diathermy should never be used but bipolar diathermy used away from a stimulator site is safe. Finally, removal of a stimulator should not only be discussed with the patient but also with the neurosurgeon or anaesthetist who implanted it, as indeed should any surgery in patients with neurostimulators if unsure about or operating close to the devices implanted.
(1) Cruccu G, Aziz TZ, Garcia-Larrea L, Hansson P, Jensen TS, Lefaucheur JP, Simpson BA, Taylor RS. EFNS guidelines on neurostimulation therapy for neuropathic pain. Eur J Neurol. 2007 Sep;14(9):952-70.
Competing interests: None declared
Oxford University Hospitals, Department of Neurosurgery, The West Wing, Oxford, OX3 9DU.
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