(Originally presented by Dr Dave Saunders)
Definition
Phaeochromocytoma: Catecholamine secreting tumour of the Adrenal Medulla
Paragangliomas: Extra-Adrenal paraganglia which may produce catecholamines
Incidence 0.2 per 100 000 people.
Rule of Ten’s (no longer totally accurate)
- 10% of phaeochromocytoma’s are extra-adrenal (i.e. paraganglioma) (actually its 24%)
- 10% are malignant (actually 29%)
- 10% are bilateral
- 10% are found in normotensive patients
- 10% are familial (actually 32%)
Pre-operative – Optimisation
Arterial pressure control and volume expansion
- Phenoxybenzamine
- Non-selective long acting alpha blockade
- Should be ceased 24-48hrs prior to OT due to long half life
- Can lead to post operative refractory hypotension
- Doxazocin
- Alpha-1 selective alpha blocker
- PRESCRIPT trial suggested less haemodynamic instability with Doxazocin compared to Phenoxybenzamine but no statistically significant clinical outcomes
- Calcium Channel blockers
- Used in conjunction with alpha blockade
- Useful for patients with severe orthostatic hypotension (with alpha blockade)
- High sodium diet and high fluid intake to maintain blood volume
Heart rate and arrhythmia control
- Tachycardia can occur due to catecholamine secreting tumour or alpha blockade
- Selective B1 agents can be used (i.e. Metoprolol, Esmolol, Atenolol)
- However it must be commenced after complete alpha blockade to avoid hypertensive crisis
Assessment and optimisation of myocardial function
- TTE / TOE is considered mandatory
- Some level of diastolic dysfunction occurs in the majority of patients
- LV systolic dysfunction occurs in around 10%
- Hypertrophic cardiomyopathy (secondary to chronic hypertension) is most frequent
- Some case reports of Atypical Takotsubo cardiomyopathy
Reversal of glucose and electrolyte disturbances
- Glucose homeostasis mediated through alpha and beta
- Increased glycogenolysis (alpha-1)
- Impaired insulin release (alpha-2)
- Lipolosys (beta-1)
- Increased glucagon release with peripheral insulin resistance (beta-2)
- Monitor and treat hyperglycaemia
Assessment of Adequate Optimisation
- α-Blockade is commenced at least 7–14 days before surgery (may need longer for cardiomyopathy or refractory hypertension)
- The Roizen criteria have historically been utilised however are now slightly dated.
- BP <160/90 consistently
- Presence of orthostatic hypotension with drop in Systolic BP at least 15% (not <80mmHg)
- ECG with no ST or T wave changes for 2 weeks
- The Roizen criteria are slightly dated. Contemporar
- BP targets should be tighter (<130/80 mmHg seated)
- Orthostatic hypotension is not a necessity
- ST or T wave changes may reflect inverted Takotsubo cardiomyopathy rather than ischaemia.
Perioperative
Positioning
- Lateral
- Kneeling prone
Hypertensive Episode During Procedure – Avoid Catecholamine release
- Surgically handling of tumour can induce catecholamine release
- Minimise Anaesthetic-induced catecholamine release stimulation
- Laryngoscope
- Coughing
- Pain
- Increased intra-abdominal pressures
- Drugs to avoid
- Desflurane
- Ketamine
- Morphine
- Pethidine
- Atracurium
- Pancuronium
- Ephedrine
- Droperidol
- Metoclopramide
- Cocaine
- (Suxamethonium: theoretical risk of provoking tumour catecholamine release however has been used without complications)
- Adjuncts to treat Hypertension
- MgSO4
- Remifentanil
- Dexmedetomidine
- Phentolamine
- SNP
- GTN
- Nicardipine
- Esmolol
Hypotensive Episodes – important after tumour devascularisation
- Treatment
- Reduce hypotensive agents
- Fluid optimisation
- Utilise Noradrenaline, metaraminol, ephedrine etc. usual vasopressors and ionotropes
- However consider Vasopressin for catecholamine resistant hypotension (bolus of 0.4 to 20 units followed by infusion of 1-3 micro units/Kg/min)
- Catecholamine Resistant Hypotension
- Residual alpha blockade (especially if phenoxybenzamine used)
- Abrupt catecholamine deficiency
- Catecholamine receptor down-regulation after chronically elevated catecholamine levels
Key Take Home Messages
- Ensure adequate preoperative optimisation
- Ensure careful planning for managing BP
- Hypertension – first stage
- Hypotension – second stage
Further reading