Cardiac Arrest and Other Methods

Conceptually, the most straightforward approach to global ischemia is cardiac arrest itself, and this is the requisite model if all issues that relate to resuscitation after systemic ischemia are to be investigated. With respect to the study of brain pathology per se, the one advantage of cardiac arrest is that complete and homogeneous ischemia is guaranteed. However, insult durations compatible with survival are short and will vary with the timing of successful resuscitation in individual animals. Nevertheless, it is possible to define the interval of effective ischemia quite precisely with appropriate monitoring approaches (see below). Injection of potassium chloride is a commonly used method to stop the heart, sometimes followed by infusion of donor blood at the time of resuscitation (17). Simultaneous mechanical obstruction of all major cardiac vessels with a hooked device inserted into the chest has been used to induce arrest in a few studies (20,94), with resuscitation accomplished by subsequent ventilation and external chest massage. A similar but less invasive method relies solely on external chest compression to both deflate the lungs and stop the heart (95).

A comprehensive overview of rodent models is included in an earlier review (96). Worth further mention in the present context are those approaches developed to improve occlusion efficacy and reliability. The 3-vessel (71) and 7-vessel occlusions (77) were noted above as conceptual extensions of the 4-VO model. More recently, a 9-VO model has been described (97) , which involves initial permanent occlusion of the basilar artery, as well as bilateral pterygopalatine, external carotid, and occipital arteries, with placement of balloon occluders to initiate ischemia by subsequent common carotid artery occlusion. Increased intracranial pressure has been combined with systemic hypotension to produce more complete ischemia during 2-VO (85). Such models can have applications in specific studies that require more profound reductions in CBF (41,98).

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