Perioperative care of phaeochromocytoma

Phaeochromocytomas are catecholamine-secreting tumours of the adrenal medulla.

The “Rule of tens”

  • 10% of phaeochromocytomas are ‘extra-adrenal’ (actually ~25%)
  • 10% are malignant (actually nearer 30%)
  • 10% are bilateral
  • 10% are found in normotensive patients
  • 10% are familial (actually around 30%)

Phaeochromocytomas may present with the classic triad of:

  1. Headache
  2. Palpitations
  3. Sweating

The objectives of preoperative care include:

  • Arterial pressure control
  • Reversal of chronic circulating volume depletion
  • Heart rate and arrhythmia control
  • Assessment and optimization of myocardial function
  • Reversal of glucose and electrolyte disturbances

Arterial pressure control

Preoperative α-blockade is standard practice and aims to provide preoperative arterial pressure control with subsequent restoration of blood volume.

Commonly used α-blockers include phenoxybenzamine and doxazosin.

Doxazosin is a competitive, selective α1-blocker. It does not cause tachycardia or sedation, making it a good alternative to phenoxybenzamine.

A randomised trial comparing phenoxybenzamine and doxazosin for preoperative treatment of patients with a pheochromocytoma (PRESCRIPT) revealed an equal efficacy of doxazocin and phenoxybenzamine pre-treatment in intra-operative haemodynamic control during resection.

Patients pretreated with PXB required more β-blockers pre-operatively, presumably via enhanced reflex tachycardia, but fewer vasodilating agents during surgery.

Heart rate and arrhythmia control

Tachyarrhythmias may result from epinephrine/dopamine-secreting tumours or be secondary to α-blockade.

Selective β1 antagonists (such as atenolol or metoprolol) are preferred to manage these and must be started after complete α-blockade.

This avoids the unopposed α-mediated vasoconstriction that could occur after antagonism of β2-mediated vasodilatation, which may precipitate a hypertensive crisis (while the negative inotropic effect of β-blockade further compromises myocardial function).

Reversal of glucose and electrolyte disturbances

Hyperglycaemia can occur due to:

  1. Increased glycogenolysis (α1 receptors)
  2. Impaired insulin release (α2 receptors)
  3. Lipolysis (β1 receptors)
  4. Increased glucagon release coupled with peripheral insulin resistance (β2 receptors) and is treated with standard therapies.

Electrolyte measurements will identify catecholamine-induced renal impairment.

Hypercalcaemia occurs when a neuroendocrine tumour is associated with a parathyroid adenoma (e.g. as occurs in MEN 2A)

Assessment of adequate optimization

α-Blockade is commenced at least 7–14 days before surgery

The team may be looking for the following criteria:

  1. Arterial pressure readings consistently <160/90
  2. The presence of orthostatic hypotension with a decrease in systolic arterial pressure of at least 15% but not <80 mm Hg
  3. an ECG which is free of ST or T wave changes for 2 weeks

Contemporary arterial pressure targets are tighter (seated arterial pressure of <130/80 mm Hg)

Orthostatic hypotension is often not a necessity

Postoperative care

All patients should receive invasive arterial pressure monitoring in a high dependency environment for at least 24h after the procedure

Hypertension

Hypertension is most commonly the result of pain, co-existing essential hypertension, urinary retention, or fluid overload. Inadvertent ligation of the renal artery precipitates hyper-reninism, which may lead to delayed hypertension

Hypotension

Hypotension after devascularisation of the tumour is relatively common and can be both profound and catecholamine-resistant.

Residual α-blockade may play a role, particularly after the preoperative use of phenoxybenzamine

Abrupt catecholamine deficiency after tumour resection in combination with catecholamine receptor down-regulation caused by chronic elevation of catecholamine levels may also be implicated

In the first instance, hypotensive agents should be stopped and fluid balance optimised. Consider postoperative haemorrhage or myocardial dysfunction

Noradrenaline can initially be used to increase peripheral vascular resistance and vasopressin should be considered if hypotension is refractory

Steroids

Lifelong steroid replacement is indicated if a bilateral adrenalectomy has been performed

Sugar

Hypoglycaemia due to rebound hyper-insulinism can occur when the inhibitory effect of norepinephrine on insulin producing cells is eliminated and its presentation may be masked by concurrent β-receptor blockade. Regular blood glucose monitoring and appropriate titration of dextrose infusions is therefore recommended