Perioperative use of dihydropyridine calcium channel blockers

Bradyarrhythmia in an anaesthetised, elderly, hypertensive cat

A 14-year-old neutered male domestic shorthaired cat was presented to the University Veterinary Centre Sydney for evaluation and treatment of dental disease. This cat developed an unusual bradyarrhythmia under anaesthesia. The possible causes and treatment of the dysrythmia are discussed.

Calcium channels--basic aspects of their structure, function and gene encoding; anesthetic action on the channels--a review

PURPOSE

To review recent findings concerning Ca(2+) channel subtype/structure/function from electrophysiological and molecular biological studies and to explain Ca(2+) channel diseases and the actions of anesthetics on Ca(2+) channels.

SOURCE

The information was obtained from articles published recently and from our published work.

PRINCIPAL FINDINGS

Voltage-dependent Ca(2+) channels serve as one of the important mechanisms for Ca(2+) influx into the cells, enabling the regulation of intracellular concentration of free Ca(2+). Recent advances both in electrophysiology and in molecular biology have made it possible to observe channel activity directly and to investigate channel functions at molecular levels. The Ca(2+) channel can be divided into subtypes according to electrophysiological characteristics, and each subtype has its own gene. The L-type Ca(2+) channel is the target of a large number of clinically important drugs, especially dihydropyridines, and binding sites of Ca(2+) antagonists have been clarified. The effects of various kinds of anesthetics in a variety of cell types have been demonstrated, and some clinical effects of anesthetics can be explained by the effects on Ca(2+) channels. It has recently become apparent that some hereditary diseases such as hypokalemic periodic paralysis result from calcium channelopathies.

CONCLUSION

Recent advances both in electrophysiology and in molecular biology have made it possible to clarify the Ca(2+) channel structures, functions, genes, and the anesthetic actions on the channels in detail. The effects of anesthetics on the Ca(2+) channels either of patients with hereditary channelopathies or using gene mutation techniques are left to be discovered.

Interactions between cardiovascular treatments and anaesthesia

Circulatory stability is one of the main objectives of the perioperative management of high-risk patients. Most of these patients are chronically treated with cardiovascular treatments, which interfere with the functioning of several physiological systems aimed at maintaining the circulatory status when the loading conditions of the heart deteriorate, or limit the compensatory mechanisms used when metabolic needs increase. Taking into account the pharmacology of these medications, their repercussions on perioperative haemodynamics and their potential beneficial effects on regional circulations, it has become possible to determine whether or not they must be given or withdrawn perioperatively.