Isoflurane Improves the Tolerance to Pacing-Induced Myocardial Ischemia

Tarnow, J.; Markschies-Hornung, Alexandra; Schulte-Sasse,

doi:10.1097/00132586-198702000-00027

Cited by 2 publications

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“…This issue has to be clarified before halothane is abandoned in favour of enflurane or isoflurane, even if isofluraneinduced coronary-steal should be dose-related. 72 It is not so important for most anaesthetists to know whether isoflurane can be employed in cardiac surgery as to know what the consequences may be, if isoflurane were to be used for routine clinical practice everywhere. Many patients with manifest heart disease or 'silent' myocardial ischaemia undergo many types of surgery and the anaesthetist needs to be sure that isoflurane will not cause myocardial ischaemia whose consequence will only become evident in the postoperative phase.…”

Section: Is Halothane Obsolete? Two Standards Of Judgementmentioning

confidence: 99%

Is halothane obsolete? Two standards of judgement

Weis¹,

Engelhardt²

1989

Anaesthesia

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Section: Is Halothane Obsolete? Two Standards Of Judgementmentioning

confidence: 99%

Is halothane obsolete? Two standards of judgement

Weis¹,

Engelhardt²

1989

Anaesthesia

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“…t paper stimulated other human studies, including those of Moffitt et al 2 and Tarnow et at. 3 In the Moffitt e~ al. studies, coronary sinus flow and oxygen contents were measured.…”

Section: Coronary Stealmentioning

confidence: 99%

Anaesthesia for the patient with cardiac disease

Tinker

1988

Can J Anaesth

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Before we can discuss the effects of anaesthesia on the coronary circulation, it seems pertinent to discuss the basic control mechanisms involved in the coronary circulation. The coronary circulation is one of if not the most "responsive" circulations in the body. The final determinant of flow to any given region of myocardium is the metabolic demand of that region. Unfortunately, although the metabolic demand of a given region might pose a certain requirement, numerous factors may prevent that metabolic demand from being satisfied. These factors include coronary artery disease, excessive heart rate, rapidly changing afterload, dysrhythmias, as well as various external "tonal" influences such as sympathetic activity and hormonal influences from the adrenal glands and elsewhere.It was commonly taught that coronary oxygen extraction was nearly complete on a given passage through the myoeardium, i.e., the maximal amount of available oxygen would be extracted. Coronary mixed-venous oxygen saturation was considered to he usually if not always as low as practically possible, namely less than 50 per cent, with a POe in the low 20"s. However, resting coronary venous oxygen saturation is not usually that low and therefore the "first line of defense" against a sudden increase in oxygen demand of the myocardium is simply for an increase in extraction of oxygen from the blood already passing through it.Next, coronary vasodilation occurs. The final determinant of coronary vasodilation in a particular cardiac region is local demand. This local demand produces adenosine, which is one of the agents important in regional dilatation, together with other factors such as "endothelial relaxant factor," etc. Also, external influences play an extremely important role. The carotid sinus reflex is a tachycardic stimulus in response to a lowered carotid arterial pressure and this reflex produces a large decrease in coronary vascular resistance when arterial pressure decreases. This is important in the interpretation of the studies mentioned below, because it is difficult to maintain constant arterial pressure. The question arises as to whether peripheral vascular effects, namely lowered arterial pressure, or intrinsic pharmacologic properties of the anaesthetic itself, contribute to the coronary vasodilation observed. Suffice it to say that these reflexes affecting the heart rate are the most important external determinants of overall coronary blood flow and exert second by second control over coronary vascular resistance, at least in a global fashion.Local factors, reflexes, and neural influences as well as endocrine influences all play roles in the regulation of the coronary circulation. Coronary steal"Coronary steal" is a catchy term with several shades of meaning. If there is a collateral-dependent zone of myocardium, blood must flow to that zone through another zone which is more directly connected to a coronary artery. It is conceivable that a direct pharmacologic vasodilator might decrease the normal tone of the "primary" area of m...

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Isoflurane Improves the Tolerance to Pacing-Induced Myocardial Ischemia

Cited by 2 publications

References 0 publications

Is halothane obsolete? Two standards of judgement

Is halothane obsolete? Two standards of judgement

Anaesthesia for the patient with cardiac disease

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