Systemic vascular responses to increased intracranial pressure: 2 The `Cushing' response in the presence of intracranial space-occupying lesions: systemic and cerebral haemodynamic studies in the dog and the baboon

Abstract

SUMMARY Continued expansion of an artificial space-occupying lesion produced further increases in mean supratentorial and infratentorial pressures associated with increases in mean arterial pressure, heart rate, and systemic vascular resistance-the 'Cushing' or systemic hypertensive response. These primary changes resulted in an increase in transtentorial pressure gradient and a decrease in arrhythmia index. Immediately before the onset of the systemic hypertensive response, supratentorial perfusion pressure was low, and the period of systemic hypertension did not appear to produce any worthwhile improvement in the perfusion pressure or in the blood flow in the supratentorial compartment. The studies demonstrated also that the systemic hypertensive response was a pre-terminal event and was followed rapidly by circulatory failure.Since the beginning of the nineteenth century, increased intracranial pressure and the mechanisms by which it acted have been the subjects of many investigations both in the experimental animal and in the clinical situation. As early as 1811, Ravina studied the effects of increased intracranial pressure after inserting glass windows in the skull. A few years later, Astley Cooper (1824) found that, in animals, mechanical pressure against the surface of the brain would produce a decrease in heart rate. In 1880, von Bergmann was able to induce a decrease in pulse rate and depression of respiration by increasing the intracranial pressure. In addition, he showed that when the intracranial pressure equalled the systolic arterial pressure in the carotid artery, death would follow. Since the observations of Kocher (1901) and Cushing (1901),

The Cushing Response: A case for a review of its role as a physiological reflex

“…These authors thus concluded that the CR is a very late phenomenon and represent the school of thought that the CR is indeed a 'pre-terminal event followed rapidly by circulatory failure'. 5 …”

“…This being the case, there is little doubt that CR is therefore associated with a grim prognosis. 3,4 Fitch et al 5 in his early study in 1977 identified the systemic hypertensive response as the last of six indices which evolve in a certain sequence from the start of a rise in ICP, together with bradycardia, arrhythmia, papillary constriction, unilateral pupillary dilatation and an increase in pulse pressure. He also noted that the 'period of systemic hypertension did not appear to produce any worthwhile improvement in the perfusion pressure or in the blood flow in the supratentorial compartment', although he found augmentation in infratentorial perfusion.…”

Intraoperative jugular bulb desaturation during acute aneurysmal rupture

“…[10][11][12][13] Some animal studies suggest Cushing's response is a late feature, when ICP approaches mean arterial pressure, signalling breakdown of cerebral autoregulation. [14][15][16][17] In this situation, hypertension leads to further increase of ICP, adversely influencing cerebral perfusion. [14][15][16][17] It is likely that both the level of maximal ICP, and the rate of ICP change influence the hemodynamic response.…”

“…[14][15][16][17] In this situation, hypertension leads to further increase of ICP, adversely influencing cerebral perfusion. [14][15][16][17] It is likely that both the level of maximal ICP, and the rate of ICP change influence the hemodynamic response. Animal studies showed "classic" Cushing's response to be apparent and beneficial to CPP only with gradual increases in ICP, with maximal ICP staying within the limits of cerebral autoregulation.…”

Dogs with macroadenomas have lower body temperature and heart rate than dogs with microadenomas

“…Healthy, smaller-sized or older animals are more likely to develop hypothermia (Lee 2017), therefore we tested and excluded age and bodyweight as potential confounding factors. One possible cause for the difference in heart rate between the two groups is a Cushing reflex secondary to increased intracranial pressure leading to heart rate reduction (Fitch et al, 1977). Another possible explanation would be a destruction of the hypothalamus by the macroadenoma.…”