Testing arterial baroreflex function in acutely unwell patients.

Abstract

Cardiovascular function is deranged in acute illnesses but specific details of this pathophysiological phenomenon are poorly understood. With advances in intensive care it is now necessary to define these changes. Existing tests of cardiovascular reflex function are ill-suited to the study of acutely unwell patients. The arterial baroreflex is the principal cardiovascular homeostatic reflex. We have modified the neck suction test of baroreflex function such that it can be performed in 30 min using portable equipment. The protocol was validated on control subjects. Testing of injured patients showed that this test and protocol could be used sequentially, beginning within 2 h of injury, to demonstrate acute changes in baroreflex function and to follow these changes through the disease process. Patient tolerance of the test was excellent. Subsequently, further modification developed an even shorter protocol whereby similar information could be obtained within 15 min. The cardiac response to deep respiration can be measured with minimal patient upset or compliance and is ideal for repetitive testing in critically ill patients. This is not a specific test of baroreflex function but responses to it show interesting parallels with changes in baroreflex function which merit further study.