Cerebral blood flow during experimental endotoxemia in volunteers

Objective: To measure cerebral blood flow, cerebral metabolic rate for oxygen, cerebral oxygen delivery, and cerebral vascular resistance during experimental endotoxemia in volunteers. Design: Experimental, prospective study. Setting: University general clinical research center. Subjects: Healthy volunteers (six male, four female, 30.1 ± 1.9 yrs of age). Interventions: Volunteers had redial, pulmonary arterial, and jugular venous bulb catheters inserted. All VOlUnteers received a bolus of Escherichia coli endotoxin (4 ng/kg). Cerebral blood flow was measured, using the Kety- Schmidt technique. Measurements and Main Results: Cerebral and systemic hemodynamics end oxygenation variables were measured at baseline and hourly for 5 hrs after endotoxin administration. A systemic hyperdynamic response characterized by an increase in body temperature (97.9 ± 0.02, 100.2 ± 0.02, and 99.7 ± 0.02°F [36.8 ± 0.01, 37.9 ± 0.1, and 37.6 ± 0.1°C] at baseline, 3, and 5 hrs, respectively), cardiac index (3.7 ± 0.2, 6.2 ± 0.2, and 5.7 ± 0.2 L/min/m² at baseline, 3, and 5 hrs), and heart rate (70 ± 2.6, 96 ± 2.6, and 93 ± 2.9 beats/ rain at baseline, 3, and 5 hrs), and e decrease in mean arterial pressure (99.3 ± 2.2, 84.4 ± 2.8, and 84 ± 3.4 mm Hg at baseline, 3, and 5 hrs) and systemic vascular resistance (1498 ± 53, 786 ± 37, 849 ± 36 dyne·sec/cm⁵·m² at baseline, 3, and 5 hrs) followed the endotoxin bolus. Cerebral blood flow (65.4 ± 4.3, 57.7 ± 3.1, and 5866 ± 3.0 mL/100 g/min at baseline, 3, and 5 hrs), cerebral oxygen delivery (11.8 ± 0.7, 9.8 ± 0.6, and 9.5 ± 0.6 mL/100 g/min at baseline, 3, and 5 hrs), cerebral metabolic rate for oxygen (3.8 ± 0.4, 3.3 ± 0.3, and 3.0 ± 03 mL/100 g/min at baseline, 3, and 5 hrs), and cerebral vascular resistance (1.4 ± 0.2, 1.4 ± 0.2, and 1.3 ± 0.2 mm Hg/mL/100 g/min at baseline, 3, and 5 hrs) were unchanged throughout the 5-hr study period. Signs of cerebral dysfunction were not apparent, although the volunteers appeared drowsy during the latter part of the study. Conclusion: A dose of endotoxin sufficient to induce systemic vasodilation in healthy subjects does not influence cerebral blood flow or the cerebral metabolic rate for oxygen.