Phaeochromocytoma

Catecholamine-secreting tumour of chromaffin tissue. Divided into:

Epidemiology and Risk Factors

Incidence is ~0.2/100,000.

Risk factors include:

  • MEN II
  • Neurofibromatosis
  • Tuberous sclerosis
  • Sturge-Weber Syndrome
  • von Hippel-Lindau disease
  • Succinate dehydrogenase enzyme mutations

Pathophysiology

Tumour of chromaffin cells:

  • 30% malignant
  • 30%

Produce a variety of:

  • Adrenaline
  • Noradrenaline
    Most common: ~60%.
  • Dopamine
    Rarer.

Aetiology

Majority are incidental, though ~30% are associated with autosomal dominant inheritance.

Clinical Manifestations

Presentation:

  • Classical triad of:
    Most patients do not have all 3.
    • Headache
    • Sweating
    • Palpitations
  • Hypertension
    Present in 90%, paroxysmal in 50%.
    • Associated cardiomyoapthy
  • Visual disturbance
    Hypertension-related papilloedema.
  • Abdominal pain
    Secondary to ischaemia.
  • Constitutional symptoms
    • Lethargy
    • Anxiety
    • Nausea
    • Weight loss
    • Hyperglycaemia
    • Tremor

Intraoperative Diagnosis

Phaeochromocytomas may present during another surgery:

  • Hypertension
    Major sign.
  • Tachyarrhythmias
  • Cardiac failure

Investigations

Diagnosis:

  • Metanephrines
    • Breakdown products of catecholamines
      • Metanephrine
      • Normetanephrine
      • Homovanillic acid for dopamine
    • Can be measured in urine and plasma
      Unsure which is superior.
      • Urinary more specific
      • Plasma more sensitive
    • Many causes of false-positives:
      • Exercise
      • Venous sampling whilst sitting
      • Diet
      • Renal impairment
      • Medications
  • Imaging
    • Half of cases are diagnosed incidentally on CT or MRI
    • CT
    • MRI
      Better sensitivity for paraganglionomas.

Evaluation of haemodynamic effects:

  • Echocardiography
    Mandatory.
  • ECG
  • Cardiac enzymes
  • UEC/

Management

Surgery is curative, but never emergent.

Medical management:

  • Required to optimise haemodynamic state pre-operatively
    This is critical to avoid excess morbidity and mortality; up to 45% without adequate control. Consequences:
    • ICH/
    • Arrhythmias
    • Ischaemia
    • LVF
  • Titration of agents usually over ~ 2 weeks
  • Goals of treatment:
    • Control arterial pressure
      Primarily α-blockade.
      • Must occur prior to β-blockade to prevent unopposed α effect
        CHF, ischaemia, shock from a low-CO high-SVR state.
      • Phenoxybenzamine 40-400mg/day
        Non-competitive, non-selective, long acting α-antagonist.
        • Commence at 10mg BD, ↑ every 2-3 days
        • Reduces catecholamine surges
        • ↑ postural hypotension
        • Implicated in post-operative hypotension
        • Should be stopped 24-48 hours prior to surgery
      • Doxazosin
        Competitive, selective α1-antagonist.
        • Reduced postural hypotension compared to phenoxybenzamine
      • Calcium channel blockers
        Good second agent to further improved BP control in patients with good α-blockade.
        • Not recommended as monotherapy
        • Consider nicardipine 30mg SR BD
    • Replete circulating volume
      Reduced due to low circulatory compliance.
      • High sodium diet, high fluid intake
      • 2L/day minimum
      • Monitor haematocrit to ensure it is reducing
    • Control heart rate and arrhythmias
      • β-blockade
        May be required to control tachyarrhythmias occurring after α-blockade achieved.
        • Selective β1 antagonists preferred
          Metoprolol, atenolol.
        • Aim HR ⩽90
      • Correct electrolyte deficiencies
    • Optimise myocardial function
      • Diastolic dysfunction in majority
      • Systolic dysfunction in ~10%
    • Control BSL
    • Correct electrolyte deficiencies

Adequacy of preoperative control:

  • Traditionally given by the Roizen criteria
    Exact use is questioned, but principle remains. Criteria require 2 weeks of:
    • BP consistently <160/90
      Tighter targets now used; aim seated SBP <130/80.
    • Postural drop of SBP >15% but not <80 mm Hg
      No longer required.
    • ECG without ischaemia
      Ischaemia is still to be avoided, but changes may represent Takotsubo rather than ischaemia.
    • Control of episodic symptoms
  • Preoperative optimisation performed over days-weeks

Anaesthetic Considerations

  • B
    • Pulmonary oedema
  • C
    • Arterial line
    • Consider CO monitoring
    • Haemodynamic control Preoperative optimisation required.
      • May be performed as an inpatient in some systems
    • Cardiomyopathy
      Bulk of patients have EF ~55% however.
    • Impaired catecholamine sensitivity
    • Avoidance of drugs with catecholamine effects
      • Desflurane
      • Ketamine
      • Morphine/pethidine
      • Atracurium/pancuronium
      • Droperidol/metoclopramide
  • D
    • Impaired insulin sensitivity
      Hypoglycaemia may occur following resection - monitor postoperatively.
    • Anxiolysis

Complications

Due to excessive catecholamine effects:

  • Pulmonary oedema
  • Cardiomyopathy
  • Arrhythmia
  • ICH/

References

  1. Connor D, Boumphrey S. Perioperative care of phaeochromocytoma. BJA Educ. 2016 May 1;16(5):153–8.