Pheochromocytoma

 

 

 

Considerations

 

  • Preoperative optimization:

    • Alpha & beta blockade

    • Restore intravascular volume

  • Hemodynamic lability & potential for pheochromocytoma crises:

    • ​Hypertension, tachycardia, arrhythmia, myocardial ischemia

    • Need for invasive hemodynamic monitoring

    • Avoidance of sympathetic stimulation, histamine-releasing drugs and unopposed alpha stimulation

  • End organ dyfunction:

    • Relative hypovolemia

    • Left ventricular hypertrophy and cardiomyopathy, ischemic heart disease, MI, arrhythmia

    • Hypertensive encephalopathy & CVA

    • Renal failure

  • Associated conditions:

    • MEN 2A: hyperparathyroidism, medullary thyroid carcinoma, pheochromocytoma

    • MEN 2B: medullary thyroid carcinoma, pheochromocytoma, mucosal neuromas

    • Neurofibromatosis

    • Von Hippel Lindau syndrome (cerebellar hemangiomas, renal cell carcinoma) 

  • Postoperative complications:

    • Hypotension       

    • Hypertension

    • Hypoglycemia

    • Hypoadrenalism


 

Goals

 

  • Adequate pre-op optimization:

    • Start with alpha blockade: phenoxybenzamine used classically; alternatively: terazosin, prazosin, doxazosin

    • Once alpha blocked, may start beta blockade 

    • Fix hypovolemia 

  • Prevent and manage pheochromocytoma crises:

    • Invasive monitoring and tight hemodynamic control

    • Avoid SNS surges (anxiolysis, deep induction, epidural)

    • Avoid histamine releasing drugs (precipitates catecholamine release from tumour)

    • Anticipate and prepare for hypotension following tumour vein ligation (volume +/- pressors/inotropes)

  • Conflicts:

    • Deep anesthesia vs. hypovolemia

 

 

Pregnancy Considerations 

 

  • Caution with hemodynamic agents that cross placenta (esmolol, propanolol)

  • Same optimization with alpha blockade followed by beta blockade applies but some suggest having hemodynamic goals even lower than Roizen criteria (e.g. upper limit 150/80mmHg but avoid orthostatic hypotension to prevent uteroplacental malperfusion) 

  • Pregnancy specific management:

    • Controversial, based on case reports: 

      • If gestational age <24 weeks: may undergo open or laparascopic resection of pheochromocytoma  

      • If gestational age >24 weeks: medical management, & may wait until fetal maturity & do combined cesarean section & tumor resection (the problem is that gravid uterus >24 weeks obstructs access to tumor resection)

      • Cesarean section is preferred as abdominal squeeze during labour can precipitate a hypertensive crisis 

        • General anesthesia or epidural anesthesia > spinal anesthesia 

        • probably best NOT TO ALLOW LABOR 

  • Increased incidence of intrauterine fetal demise, growth restriction, abruption

  • Often misdiagnosed as pre-eclampsia

 

 

Background

 

  • Roizen criteria:

  1. No in-hospital blood pressure reading higher than 165/90 mmHg should be evident for 48 hours before surgery. We often measure arterial blood pressure every minute for 1 hour in a stressful environment (eg. postanesthesia care unit). If no reading is greater than 165/90mmHg, this criterion is considered satisfied. 

  2. Orthostatic hypotension should be present, but blood pressure on standing should not be lower than 80/45mmHg. 

  3. ECG should be free of ST-T changes that are not permanent

  4. No more than one PVC should occur every 5 minutes

 

  • Anti-hypertensive agents:

    • Use short acting agents only!

    • Sodium nitroprusside (50mg in 250mL NS = 200mcg/mL): run at 25-200mcg/min or 0.3-3mcg/kg/min

      • prepare syringe of 100mcg/mL for bolusing 

    • Esmolol (10mg/mL as per ampule): run at 50-250 mcg/kg/min

    • Phentolamine (10mg ampule): administer 1-2mg boluses; may increase to 5mg/dose; onset/offset immediate

    • MgSO4: 4-6g at induction over 30 minutes then 1-2g/hr 

 

  • Anti-hypotensive agents:

    • Norepinephrine (4mg in 250mL NS = 16 mcg/mL): run at 1-20mcg/min

      • bolus 20-30mcg/dose

    • Vasopressin: run at 0.01-0.04 U/min and boluses 4U/dose for hypotension refractory to norepinephrine 

    • Consider calcium if magnesium used intraoperatively