To the Editor:
An intriguing case occurred recently at our hospital. This case involves resistant hypotension refractory to treatment in a patient under general anesthesia with an implantable intrathecal device. This polypharmacy intrathecal pump was in place for pain control. The patient was scheduled for a revascularization of the lower extremities (aorto-bifemoral artery revascularization). The patient was an obese female with COPD, HTN, chronic pain, and peripheral vascular disease. The pain pump contained fentanyl, meperidine, bupivicaine and clonidine.
Intra-operatively, the patient appeared to have a high output, low SVR/PVR clinical state that was unresponsive to Neosynephrine, dopamine, epinephrine and norepinephrine. This patient reacted as if she was adrenergically nonresponsive or catecholamine depleted. Over the next sixteen days, the patient continued with this high cardiac output, low SVR/PVR state despite having a continual Levophed infusion. Ultimately the patient succumbed to multiorgan failure and respiratory complications. The differential diagnosis list was logically worked out with consults and labs. Briefly, cardiomyopathy and heart related problems ruled out, sepsis early on (she had catheter tip positive cultures 9 days post-op) ruled out, neuromuscular/spinal related catastrophes ruled out, endocrine problems ruled out, limb ischemia /lactic acidosis ruled out. Submucosal intestinal ischemia was never ruled out, but for it to have been a problem intra-operatively and continue for 3 weeks without becoming obvious on blood gases is unlikely.
This letter is to warn others of the potential problems with intrathecal pumps, specifically ones with alpha 2 agonist medication.
Studies have shown the hypotensive side effect of clonidine in whatever route given.1-14 The clonidine dose used on this patient was on the low end, 55 micrograms a day. Some studies discuss high doses of 500 micrograms a day.15 No studies have investigated the neuromuscular, vascular or cardiovascular physiologic changes that can occur over long period of administration.
What’s the price of pain control? At what point do we say, turn it offÑbecause it’s all investigational. This mode of pain control is becoming more popular, and we all will encounter more such patients needing general and/or regional anesthesia. All I can say is it may be prudent to learn more about intrathecal drugs, their side effects, how to avoid side effects, how to turn the pumps off safely without withdrawal phenomenon and what the physiology behind long- and short-term effects of intrathecal clonidine.
Kyle Jones, MD
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13. Benhamour D, Thorin D, Brichant IF et al: Intrathecal clonidine and fentanyl with hyperbaric bupivicaine improves analgesia during cesarean section. Anesthesia & Analgesia Vol 87:609-613.
14. Mercier F, Donnas M, Bouaziz H et al: The effect of adding a minidose of clonidine to intrathecal sufentanil for labor analgesia. Anesthesiology. 89:594-601, 1998.
15. Current Practices in intraspinal therapy, evidence based review of the literature on intrathecal delivery of pain medication, clinical guidelines for intraspinal infusion: report of an expert panel, future directions in the management of pain by intraspinal drug delivery: Special Section Polyanalgesic Consensus Conference 2000, Journal of Pain and Symptom Management 2000:20(2):sl-s50.