Tauzin-Fin and colleagues1 used urapidil, an 1 adrenergic blocker, intermittently, to control the intraoperative surges in blood pressure attributable to either tumour manipulation or the pneumoperitonium. In the USA, urapidil is an investigational drug and can not be used in clinical practice.
The authors' paper reminds us of the one we had published in the British Journal of Anaesthesia in 1994.5 This paper recommends the use of metyrosine, an agent that reduces biosynthesis of catecholamines (often to normal levels) and also phenoxybenzamine, a non-competitive long-acting mixed -antagonist. Both are continued to the morning of surgery. In the Lippmann paper,5 desflurane was used, then a new inhalational agent released by the Federal Drug Administration for general use. This inhalational agent has a powerful and fast vasodilating effect and can be easily titrated to control hypertensive surges. Tauzin-Fin and colleagues,1 used isoflurane or sevoflurane, which also have a vasodilating effect, although slower in onset.
Lippmann's5 paper stresses that whatever inhalational agent or other drugs are used, the main aspect that the anesthetist should be concerned with is that the patient should be well prepared before surgery by either the surgeon or endocrinologist. It is the unprepared (lack of adequate -blockade) patient who is most at risk. Volume expansion,
-blockade and the use of metyrosine are, we think, the keys to success in the phaeochromocytoma patient going for surgery.
Los Angeles, CA, USA
We agree with Dr Lippmann's view that the key to success is pre- and intra-operative -blockade, probably using short-acting agents. Unfortunately, the ideal short-acting
blocker has not yet been determined. Metyrosine reduces the biosynthesis of catecholamines without establishing haemodynamic stability, thereby causing possible cardiovascular collapse after tumour gland removal.11 Phenoxybenzamine, a non-selective
adrenoreceptor antagonist, has a long duration of action and a pharmacological half-life of about 24 h. Its chronotropic and inotropic effects can be controlled with ß-blockers.11 Prazosin is a selective, competitive
1 adrenoreceptor blocker that, given orally, improves the management of phaeochromocytoma only in the preoperative phase.11 All these drugs may exert delayed effects that can increase the incidence of severe hypotension after tumour removal. An alternative treatment is urapidil, a competitive and selective short-acting
1 blocker, administered by continuous i.v. infusion preoperatively and throughout anaesthesia, to block
1 adrenergic receptors before any acute catecholamine release during surgery.1 Its pharmacological profile renders it effective in this situation. If severe rises in blood pressure occur, nicardipine at low doses is an effective adjuvant treatment, whose action is potentiated by sevoflurane.12 13 Desflurane should be avoided as it is associated with catecholamine release if given rapidly in high concentrations.14
We totally share Dr Lippmann's conclusions that the unprepared patient is most at risk, and we believe that the use of urapidil represents a modern, pathophysiological approach to the perioperative management of phaeochromocytoma.
Bordeaux, France
References
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