Disassociation of static and dynamic cerebral autoregulatory performance in healthy volunteers after lipopolysaccharide infusion and in patients with sepsis

Abstract

Berg RM, Plovsing RR, Ronit A, Bailey DM, Holstein-Rathlou NH, Møller K. Disassociation of static and dynamic cerebral autoregulatory performance in healthy volunteers after lipopolysaccharide infusion and in patients with sepsis.

Effects of short-term mechanical hyperventilation on cerebral blood flow and dynamic cerebral autoregulation in critically ill patients with sepsis

“…In the time domain, the cerebrovascular adjustments to a change in blood pressure is considered as a function of time, and may be quantitated by a moving correlation coefficient, which is continually calculated between a CBF estimate and MAP over specified time intervals [5][6][7][8]. In the frequency domain, the ability of the cerebrovasculature to respond to blood pressure fluctuations that occur at different frequencies is addressed by TFA [4], which is a classical and currently the most widely used approach for investigating dCA in humans [3,32]. Despite fundamentally different methodologies, these previous studies all report that higher PaCO 2 levels are associated with progressively prolonged response times of the cerebrovasculature [4,7,8].…”

“…The exclusion criteria were clinical and/or laboratory evidence of neurotrauma, neuroinfection, cerebrovascular disease, pregnancy, and a history of arterial hypertension. Sixteen patients were included in the study, and we have previously published data on cerebral haemodynamics and haemostasis from this cohort [4,[27][28][29][30].…”

“…Within recent years, several studies have reported that dynamic cerebral autoregulation (dCA) is impaired in septic patients admitted to the intensive care unit (ICU) [4][5][6][7][8]. Together, the studies indicate that dCA operates with a prolonged response time in these patients, which may expose the brain to intermittent hypo-and hyperperfusion during acute fluctuations in CPP.…”

“…PaCO 2 is known to affect cerebrovascular resistance through effects on perivascular pH [12,13], which may change cerebral autoregulatory function; hence an increase in PaCO 2 may weaken autoregulatory performance [3,[14][15][16][17][18][19][20][21] while a reduction may have the opposite effect [3,15,17,[20][21][22]. Accordingly, the dCA impairment in septic patients has been reported to be related to the PaCO 2 level, with progressively slower cerebrovascular responses at higher PaCO 2 [4,7,8], and a hyperventilation-induced reduction in PaCO 2 has been proposed as neuroprotective by improving dCA [23]. In the present study, we therefore investigated whether reducing PaCO 2 by short-term mechanical hyperventilation would cause cerebral vasoconstriction and enhance dCA in patients with severe sepsis or septic shock.…”

Measuring cerebrovascular autoregulation in preterm infants using near-infrared spectroscopy: an overview of the literature

“…This concept is largely adapted from insights from adult studies [8]; CBF is suggested to be stable (plateau) over a wide ABP range, reflecting 'intact' static cerebrovascular autoregulation (lower panel in Figure 1). Noteworthy, in adult studies, it has been suggested that this plateau might not be completely horizontal [9,10]. Absent autoregulation is often represented by a strong linear relationship between CBF and ABP (upper panel in Figure 1).…”