POSTPRANDIAL AND ORTHOSTATIC CARDIOVASCULAR CHANGES AFTER ACUTE STROKE

Background and Purpose Large falls in blood pressure after meals have been demonstrated in fit and frail elderly subjects; these changes may be associated with an increased incidence of stroke. Postprandial fal ls in BP may be particularly deleterious after acute stroke, when norm al baroreflex mechanisms and cerebral autoregulation are already impai red, resulting in stroke progression. Therefore, the postprandial hemo dynamic responses to orthostasis were examined in nine acute stroke su bjects and eight age-, sex-, and blood pressure-matched control subjec ts after an oral energy load. Methods All subjects were studied on two occasions in a randomized, double-blind, crossover trial after admini stration of either oral glucose (1 g/kg body wt) or equivalent isovolu mic, isosmotic xylose (0.83 g/kg). Measurements of blood pressure, pul se rate. and forearm blood flow were recorded for 30 minutes preprandi ally and 90 minutes postprandially. Hemodynamic responses to 60 degree s tilt, along with plasma glucose and insulin changes, were measured a t baseline and at 30-minute intervals postprandially. Results Supine m ean arterial and diastolic blood pressures fell significantly after gl ucose but not xylose ingestion in control subjects (P<.03) but not str oke subjects, whereas supine pulse rate increased in stroke subjects ( P<.04) only. No significant changes in forearm vascular resistance wer e recorded in either control or stroke subjects. After till, stroke su bjects showed a fall in mean arterial pressure compared with control s ubjects preprandially (P=.03) and at 30 (P<.005) and 90 (P<.03) minute s postprandially, although no differences were observed between the xy lose and glucose phases. Orthostatic tolerance was maintained in contr ol subjects throughout both phases of the study. Pulse rate increased significantly to tilt at all time intervals in both groups, although t here were no significant changes in forearm vascular resistance. Concl usions Acute stroke subjects are not at significantly greater risk of blood pressure falls in response to an oral energy load than age-, sex -, and blood pressure-matched control subjects. Unlike control subject s, the stroke group had an increased pulse rate postprandially, which could result in a compensatory rise in cardiac output as a result of i ncreased sympathetic nervous system activity in the poststroke period. Although orthostatic blood pressure control is impaired after acute s troke, these changes are unaffected by meals.