Pheochromocytoma / Paraganglioma
Anesthesia Implications
Anesthesia Implications
Perioperative events – patients undergoing tumor resections may exhibit labile blood pressure, arrhythmias, and tachycardia during and after surgery.
Higher risk patients – Risks are higher when a patient has an unrecognized catecholamine-releasing tumor. Patients may have already experienced end-organ damage due to increased catecholamine secretions. The risk of adverse perioperative events are attributed to larger tumor sizes (over 6cm), increased levels of preoperative catecholamine, and longer surgery duration.
Preoperative priorities – Recognition of the condition is a high priority. Preoperative symptoms often manifest as hypertension, headache, and sweating. Less common symptoms include orthostatic hypotension, blurred vision, papilledema, loss, polyuria, polydipsia, and constipation. People with hereditary diagnoses such as von Hippel Lindau, multiple endocrine neoplasia type 2, and neurofibromatosis type 1 should be evaluated for pheochromocytoma. When the patient is known to have this condition, assessment should be conducted within 7-14 days before surgery to ensure patient treatment is optimized (control of hypertension and intravascular volume). The endocrinologist will titrate medications (utilizing a combination of alpha-adrenergic blockers, beta-adrenergic blockers, calcium channel blockers, and metyrosine) and treatment to minimize the psychological catecholamine release experienced during removal of the tumor. Preoperative evaluations should include a cardiac evaluation including ECG and echocardiogram, and a type and screen. Anxiolysis with midazolam 1-2 mg is especially recommended (where not contraindicated) to facilitate a smooth induction.
Induction – The goal here is to make sure the patient is adequately ‘deep’ enough to prevent a hypertensive response during intubation and surgical stimulation.
Intraoperative management – See ‘Intraoperative Drug Management’ below. Establish an arterial line and large bore IV access. Those with known depressed cardiac function also need a CVC and PA catheter. General anesthesia is recommended for these patients. Sevoflurane is usually the drug of choice due to its reduced arrhythmogenic potential. Alternatively, TIVA has also been used as a safe technique. Epidural anesthesia may be utilized, but be aware that sympathectomy and vasodilation may exaggerate hypotension after the effluent vein is clamped on the tumor.
Intraoperative concerns – See ‘Intraoperative Drug Management’ below. Excess catecholamines result in volume depletion, postural hypotension, organ and/or limb ischemia, aortic dissection, angina myocardial infarction, acute and chronic cardiomyopathy, congestive heart failure, and arrhythmias.
Postop – Most patients remain intubated after the procedure. ICU deposition may be required if the patient requires vasoactive medication. Concerns include recovering normal adrenergic function with stable BP, hypocalcemia, and possible adrenal insufficiency.
Drugs to Avoid
Dopamine-blocking Drugs – Metoclopramide (can induce hypertensive crisis), Droperidol (small bolus doses of up to 0.625 mg are safe, but large doses can cause hypertensive crisis in patients without alpha blockade), Haloperidol, Chlorpromazine, Prochlorperazine, Glucagon (causes tumors to release catecholamines from tumors)
Sympathomimetic Drugs – Ketamine, Cocaine, Ephedrine (should be avoided until the tumor is excised to prevent an exaggerated response)
Histamine releasing medication – Morphine, Atracurium
Gases to avoid – Desflurane is avoided because of its propensity to induced hypertension and tachycardia. Halothane should not be used because of its potential to cause arrhythmias.
Intraoperative Drug Management
Patients who have catecholamine releasing tumors have labile hemodynamics when the tumor is manipulated – even if they are optimized. The surgery can be divided into two stages:
Phase I – before ligation of effluent vein. This stage is characterized by hypertension, tachycardia, and arrhythmias. The goal for systolic blood pressure during this phase will be 100-160 mmHg.
Phase II – after ligation of the effluent vein. This stage is characterized by hypotension.
Below are the drugs of choice:
-Hypertension/Arrhythmias-
Nitroprusside – drug of choice for intraoperative hypertensive crisis. Infusion of 0.5 – 4 mcg/kg/min. Prolonged infusion should not exceed 3 mcg/kg/min to prevent thiocyanate toxicity.
Phentolamines – (Nonselective alpha-blocker) – a test bolus dose of 1 mg is given followed by 1-5 mg bolus, or continuous infusion of 0.5 to 1 mg/min.
Clevidipine – (short-acting calcium channel blocker) start dose at 1-2 to mg/hr and titrate 1-2 mg/hr every 90 seconds until the targeted BP is reached. Max dose of 21 mg/hr.
Labetalol – (combined Alpha-beta blocker) – administered 5-20 mg IV
Esmolol – (B1-adrenergic blocker) administered 10-50 mg IV bolus. Alternatively, 25-250mcg/kg/min infusion.
Magnesium – (inhibits catecholamine release and antiarrhythmic with cardiac membrane stabilizing effects) – Dosage included 1-3 g administered via an IV for 20 min after intubation and a continuous infusion of 1-2 g/hr until the venous drainage from the tumor is ligated or removed. This is not routinely used but reserved for difficult-to-control patients. Research varies as to its benefit.
Antiarrhythmics – SVT is common, so the patient may require lidocaine, esmolol, or amiodarone to control the rhythm.
– Hypotension –
Phenylephrine – drug of choice because of its short half-life and pure alpha agonist. IV Bolus of 40-160 mcg or infusion of 10-200 mcg/min, titrated to effect.
Ephedrine – should be avoided until tumor removal.
Norepinephrine – 2-20 mcg/min IV infusion, titrated to effect.
Vasopressin – used for refractory hypotension after tumor removal. Initial dose is 0.01 to 0.03 units /min with maintenance does of 0.03 to 0.04 units/min
– Other –
Insulin – Insulin infusion may be required. 36% of patients that have this condition also have diabetes. A common goal is to keep the blood glucose below 160.
Pathophysiology
Both pheochromocytomas and paragangliomas are neoplasms that secrete catecholamines.
Pheochromocytomas are neoplasms of the chromaffin tissue. Paragangliomas are tumors that arise from the extra-adrenal autonomic ganglia. However, paragangliomas are indistinguishable at the histological level and have the same anesthetic management.
Twenty-five to 50% of hospital deaths have been attributed to pheochromocytoms undiagnosed or treated before anesthesia induction.
