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Phenylephrine Infusion Test After Alpha Blockade in Pheochromocytoma During Cesarean Section
Abstract Number: T 49
Abstract Type: Case Report/Case Series
Pheochromocytomas are rare tumors that secrete catecholamines. We describe the management of a pregnant woman with bilateral pheochromocytomas. A unique aspect of our management was the use of a pre-operative phenylephrine infusion challenge to assess the efficacy of α-adrenergic blockade.
A 35 year old woman with known bilateral pheochromocytomas (who refused adrenalectomy prior to pregnancy) presented for scheduled C-section. She denied hypertension but did report paroxysmal palpitations. Phenoxybenzamine was started 14 days prior to scheduled delivery.
On the day of surgery, orthostatic testing was negative. Since the patient was preoperatively on α-blocking medication, her responsiveness to the α1-agonist phenylephrine was assessed. An IV infusion was started pre-operatively at a rate of 40mcg/min, and increased in increments of 20mcg/min every two minutes to 180mcg/min with no increase in BP or change in pulse.
Following a combined spinal-epidural, vasopressin was infused at 2U/hr to prevent and/or treat hypotension from sympathetic blockade(1). The C-section proceeded uneventfully with hemodynamic stability. The patient was maintained on a patient-controlled epidural analgesia infusion for 24 hours post-op in order to avoid an increase in sympathetic discharge due to pain. Phenoxybenzamine was re-initiated two hours post-operatively and the patient was discharged home on postoperative day 3.
The main goal of management of pheochromocytoma is to prevent a hypertensive crisis. Medical treatment with α-blockade should be started as soon as the diagnosis is established and should be given for ≥ 10 to 14 days(2).
Prophylactic continuous infusion of phenylephrine is usually initiated in our institution to prevent hypotension, nausea and vomiting that can be associated with spinal anesthesia. However, because of prior α-blockade, we believed that phenylephrine might not have much effect on this patient’s hemodynamics. It is also possible that the preoperative absence of α-adrenergic tone would mean that the spinal anesthetic might not cause much further change in vascular resistance. The classic “test” of blockade in the presence of a pheochromocytoma is orthostatic hypotension (not present here), but the lack of response to phenylephrine suggests that she was adequately blocked(3). Only a few cases describing the anesthetic management of the parturient with pheochromocytoma have been reported, and the use of a phenylephrine test infusion is this setting is even more unique.
1. Augoustides JG, et al. Vasopressin for hemodynamic rescue for catecholamine-resistant vasoplegic shock after resection of massive pheochromocytoma. Anesthesiology. 2004 Oct;101(4):1022-4.
2. Witteles RM, et al. Safe and cost-effective preoperative preparation of patients with pheochromocytoma. Anesth Analg. 2000;91:302–304.
3. Reisch N, et al. Pheochromocytoma: presentation, diagnosis and treatment. J Hypertens. 2006;24:2331–2339.