Adenosine to facilitate the clipping of cerebral aneurysms: literature review.

Cerebral aneurysms have a high mortality rate when ruptured. Endovascular techniques have improved substantially in treating this pathology. However, surgical clip ligation remains the preferred option for some aneurysms. Various techniques are used intraoperatively to assist the surgeon in dissecting the aneurysmal dome free of surrounding tissue and placing a clip around the neck safely and effectively so that no nearby perforating vessels are affected and no residual remains. These techniques include temporary clip ligation, endovascular balloon occlusion and cardiac standstill. Adenosine use is one viable option for induced cardiac arrest leading to a short period of controlled hypotension. Its predictable course of action, rapid onset and offset and rare incidence of adverse side effects make it an attractive agent in this regard. Below, we provide an introduction to adenosine use, describing its pharmacokinetic properties, indications, contraindications, complications and future directions.

Pheochromocytoma crisis induced by glucocorticoids: a report of four cases and review of the literature.

CONTEXT: Pheochromocytoma crisis (PC) is a rare life-threatening endocrine emergency that may present spontaneously or can be unmasked by 'triggers', including certain medications that provoke the release of catecholamines by tumors. Several isolated cases of PC have been reported after administration of exogenous glucocorticoids; evidence that these drugs cause adverse events in patients with pheochromocytoma is mainly anecdotal. PATIENTS: We report four cases of PC most likely induced by glucocorticoids and review seven previous reports in the literature linking steroid administration to the development of PC. RESULTS: In four new cases reported here, glucocorticoid administration was associated with a fatal outcome in one case, a pheochromocytoma multisystem crisis in another, and serious hypertensive crises in two others. Two patients had incidental adrenal masses and were undergoing high-dose dexamethasone suppression tests (DST). CONCLUSIONS: Exogenous glucocorticoids may unpredictably trigger PC. Pheochromocytoma should be included in the differential diagnosis of any patient who develops a hypertensive crisis, cardiac failure, tachycardia, headache, and abdominal or chest pain after receiving exogenous glucocorticoids. Glucocorticoid induced PC is frequently associated with hemorrhagic pheochromocytoma. Although exogenous glucocorticoids cause serious complications unpredictably, they should be avoided or administered only if necessary and with caution in patients with known or suspected pheochromocytoma. During the investigation of incidental adrenal masses, pheochromocytoma should ideally be ruled out before administering glucocorticoids. However, no cases have been reported with 1 mg of dexamethasone when given as a DST in patients with pheochromocytoma; larger doses, as low as 2 mg of dexamethasone, may trigger a PC. A patient with pheochromocytoma presenting as an adrenal incidentaloma may also be at risk if exposed to glucocorticoids given as pre-treatment in case of allergy to contrast media.

Adverse drug reactions in patients with phaeochromocytoma: incidence, prevention and management.

The dangers of phaeochromocytomas are mainly due to the capability of these neuroendocrine tumours to secrete large quantities of vasoactive catecholamines, thereby increasing blood pressure and causing other related adverse events or complications. Phaeochromocytomas are often missed, sometimes only becoming apparent during therapeutic interventions that provoke release or interfere with the disposition of catecholamines produced by the tumours. Because phaeochromocytomas are rare, evidence contraindicating use of specific drugs is largely anecdotal or based on case reports. The heterogeneous nature of the tumours also makes adverse reactions highly variable among patients. Some drugs, such as dopamine D(2) receptor antagonists (e.g. metoclopramide, veralipride) and beta-adrenergic receptor antagonists (beta-blockers) clearly carry high potential for adverse reactions, while others such as tricyclic antidepressants seem more inconsistent in producing complications. Other drugs capable of causing adverse reactions include monoamine oxidase inhibitors, sympathomimetics (e.g. ephedrine) and certain peptide and corticosteroid hormones (e.g. corticotropin, glucagon and glucocorticoids). Risks associated with contraindicated medications are easily minimised by adoption of appropriate safeguards (e.g. adrenoceptor blockade). Without such precautions, the state of cardiovascular vulnerability makes some drugs and manipulations employed during surgical anaesthesia particularly dangerous. Problems arise most often when drugs or therapeutic procedures are employed in patients in whom the tumour is not suspected. In such cases, it is extremely important for the clinician to recognise the possibility of an underlying catecholamine-producing tumour and to take the most appropriate steps to manage and treat adverse events and clinical complications.