Assessment of Cerebral Vasoreactivity Using Near-infrared Spectroscopy (NIRS) in Infants (VARO) (VARO)

The purpose of this study is to show that a permissive hypercapnia during mechanical ventilation in children under general anaesthesia will improve cerebral perfusion.

Mechanical ventilation interferes with cerebral perfusion via the changes in intrathoracic pressure and/or as a consequence of hypocapnia. This latter occurs frequently following traditional ventilation strategies with relatively high tidal volume and respiratory rate. New trends in anesthesia intend to promote protective lung ventilation by keeping a normocapnic or even mildly hypercapnic state. However, cerebral vascular vasotonicity is carbon dioxide (CO2)-dependent with hypocapnia potentially leading to vasoconstriction and subsequent decrease in cerebral blood flow. Changes in cerebral vasoreactivity can be assessed by the near infrared spectroscopy (NIRS) device. This monitoring evaluates the changes in various parameters (deoxygenated hemoglobin, oxygenated hemoglobin, the tissue oxygenation index (TOI) and the tissue hemoglobin index (THI)) that act as surrogate for cerebral vasoconstriction. We, therefore designed this prospective observational comparative effectiveness study in order to characterize the potential beneficial effect of permissive hypercapnia on cerebral perfusion in infants.

The Child will be ventilated in order to achieve an end-tidal carbon dioxide (ETCO2) of 5.5 kiloPascal (kPa). Measurements will be performed after steady state condition. Then the ventilation will be reduced to allow ETCO2 to reach 6.5 kPa before repeating the measurements. Finally, the child will be again ventilated to obtain a normocapnia condition.

The Child will be ventilated in order to achieve a ETCO2 of 6.5 kPa. Measurements will be performed after steady state condition. Then the ventilation will be increased to allow ETCO2 to reach 5.5 kPa before repeating the measurements. Finally, the child will be again ventilated to obtain a mild hypercapnic condition

Assessment of the changes in TOI and THI as measured by NIRS under normocapnia and permissive hypercapnia

At steady state (2-3 minutes) after achieving each level of ETCO2 and every 2 minutes up to 6 minutes for each level

Assessment changes in oxygen partial pressure (PaO2), carbon dioxide partial pressure (PaCO2) and potential of hydrogen (pH) under one level of ETCO2

At steady state (2-3 minutes) after achieving each level of ETCO2 and every 2 minutes up to 6 minutes for each level

At steady state (2-3 minutes) after achieving each level of ETCO2 and every 2 minutes up to 6 minutes for each level

At steady state (2-3 minutes) after achieving each level of ETCO2 and every 2 minutes up to 6 minutes for each level

Inclusion Criteria: term neonates during their infancy for elective surgery requiring general anesthesia and endotracheal intubation Exclusion Criteria: all infants with cardiac anomalies, chronic pulmonary disease (bronchopulmonary dysplasia, cystic fibrosis, asthma), pulmonary hypertension or cranial hypertension will be excluded all infants where no access to the forehead is possible as a consequence of the operating field

Schopfer L, Habre W, Pichon I, Fodor GH. Effect of Permissive Mild Hypercapnia on Cerebral Vasoreactivity in Infants: A Randomized Controlled Crossover Trial. Anesth Analg. 2021 Oct 1;133(4):976-983. doi: 10.1213/ANE.0000000000005325.