Intracranial baroreflex yielding an early cushing response in human.

The Cushing response is a pre-terminal sympatho-adrenal systemic response to very high ICP. Animal studies have demonstrated that a moderate rise of ICP yields a reversible pressure-mediated systemic response. Infusion studies are routine procedures to investigate, by infusing CSF space with saline, the cerebrospinal fluid (CSF) biophysics in patients suspected of hydrocephalus. Our study aims at assessing systemic and cerebral haemodynamic changes during moderate rise of ICP in human. Infusion studies were performed in 34 patients. This is a routine test perform in patients presenting with symptoms of NPH during their pre-shunting assessment. Arterial blood pressure (ABP) and cerebral blood flow velocity (FV) were non-invasively monitored with photoplethysmography and transcranial Doppler. The rise in ICP (8.2 +/- 5.1 mmHg to 25 +/- 8.3 mmHg) was followed by a significant rise in ABP (106.6 +/- 29.7 mmHg to 115.2 +/- 30.1 mmHg), drop in CPP (98.3 +/- 29 mmHg to 90.2 +/- 30.7 mmHg) and decrease in FV (55.6 +/- 17 cm/s to 51.1 +/- 16.3 cm/s). Increasing ICP did not alter heart rate (70.4 +/- 10.4/min to 70.3 +/- 9.1/min) but augmented the heart rate variance (0.046 +/- 0.058 to 0.067 +/- 0.075/min). In a population suspected of hydrocephalus, our study demonstrated that a moderate rise of ICP yields a reversible pressure-mediated systemic response, demonstrating an early Cushing response in human and a putative intracranial baroreflex.