Hyperventilation and the brain – helpful or hazardous ? (

Hyperventilation has been a common practice in neuroanesthesia since the 1960’s. However, a review of the literature suggests that hypocapnia was not initially deliberately introduced into practice to improve operating conditions but was perhaps an inadvertent by-product of muscle relaxation and thereby the need for intermittent positive pressure ventilation (IPPV). The first clinical report of its use in neurosurgery in the peer review literature came from Melbourne in 1957 and involved a review of “72 craniotomies and 28 spinal operations far too small a number for statistical purposes.” The authors went on to draw the following conclusions: “It is, nevertheless, a strong clinical impression that we are obtaining better operating conditions with controlled respiration technique. After preliminary tentative trials, gradually the neurosurgeons were completely convinced and prefer this technique.” “It is impossible to say that this method is better than spontaneous respiration and equally good operating conditions are produced with perfect open circuit anaesthesia.” As blood gas or end-tidal gas sampling were not available it is in fact impossible to know if hyperventilation was indeed achieved and it is likely that the authors were simply referring to the use of mechanical ventilation.