Vasopressors Do Not Influence Cerebral Critical Closing Pressure During Systemic Inflammation Evoked by Experimental Endotoxemia and Sepsis in Humans.

Aim: The aim of this study was to investigate the effects of different vasopressors on the cerebral vasculature during experimental human endotoxemia and sepsis. We used the critical closing pressure (CrCP) as a measure of cerebral vascular tone. Methods: We performed a prospective pilot study, at the intensive care department (ICU) of a tertiary care university hospital in the Netherlands, in 40 healthy male subjects during experimental human endotoxemia (administration of bacterial lipopolysaccharide [LPS]) and in 10 patients with severe sepsis or septic shock. Subjects in the endotoxemia study were randomized to receive a 5 h infusion of either 0.05mg/kg/min noradrenaline (n = 10, "LPS-nor"), 0.5 mu g/kg/min phenylephrine (n = 10, "LPS-phenyl"), 0.04 IU/min vasopressin (n = 10, "LPS-AVP"), or saline (n = 10, "LPS-placebo") starting 1 h before intravenous administration of 2 ng/kg LPS. In patients with sepsis, fluid resuscitation and vasopressor use was at the discretion of the medical team, aiming at normovolemia and a mean arterial pressure (MAP)> 65 mm Hg, using noradrenaline. The mean flow velocity in the middle cerebral artery (MFVMCA) was measured by transcranial Doppler (TCD) with simultaneously recording of heart rate, arterial blood pressure, respiratory rate, and oxygen saturation. CrCP was estimated using the cerebrovascular impedance model. Results: The CrCP decreased in the LPS-placebo group from 52.6 [46.6-55.5] mm Hg at baseline to 44.1 [41.2-51.3] mm Hg at 270 min post-LPS (P = 0.03). Infusion of phenylephrine increased the CrCP in the period before LPS administration from 46.9 [38.8-53.4] to 53.8 [52.9-60.2] mmHg (P = 0.02), but after LPS administration, a similar decrease was observed compared with the LPS-placebo group. Noradrenaline or vasopressin prior to LPS did not affect the CrCP. The decrease in CrCP after LPS bolus was similar in all treatment groups. The CrCP in the sepsis patients equaled 35.7 [34.4-42.0] mm Hg, and was lower compared with that in the LPS-placebo subjects from baseline until 90 min after LPS (P<0.01). Conclusions: Experimental human endotoxemia results in a decreased CrCP due to a loss of vascular resistance of the arterial bed. Vasopressors did not prevent this decrease in CrCP. Findings in patients with sepsis are comparable to those found in subjects after LPS administration. Patients with sepsis, despite treatment with vasopressors, have a risk for low cerebral blood flow and ischemia.