Prevention of venous air embolism in paediatric neurosurgical procedures performed in the sitting position by combined use of MAST suit and PEEP

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Abstract
We studied 60 children undergoing neurosurgical procedures in the sitting position. Routine monitoring included ECG, pulse oximetry, invasive arterial pressure, in particular mean arterial pressure (MAP), and right atrial pressure (RAP). Children were allocated to two groups. In group B lower body positive pressure and positive end-expiratory pressure (PEEP) were used for preventing venous air embolism (VAE). In this group, antishock trousers (MAST suit) were adjusted in supine children. After induction of anaesthesia, different positions were studied: supine and sitting before MAST suit inflation, sitting with MAST suit inflated up to a pressure of 40 mm Hg in the lower compartments and 30 mm Hg in the abdominal compartment, and finally a combination of lower body positive pressure and PEEP of 8–10cm H2O. In group A no MAST suit or PEEP was used. Continuous monitoring of end-tidal carbon dioxide pressure throughout (PE′co2 was used to detect VAE. In order to evaluate the transmission of pressures from the right atrium to the veins at the base of the skull, jugular bulb venous pressure (JBVP) was measured in 20 patients by retrograde catheterization. The incidence of VAE was compared in the two groups. On placing children into the sitting position, a significant decrease in RAP and JBVP was noted without significant changes in MAP in the two groups. Inflation of the MAST suit induced a dramatic increase in RAP and JBVP, reinforced by addition of PEEP. There was a strong positive relationship between RAP and JBVP. There were no deleterious side effects or differences between the two groups in peroperative blood product requirements or surgical general conditions. VAE was not noted in group B, compared with a 26% incidence of peroperative VAE detected by a decrease in PE′co2, of at least 0.4 kPa resulting in significant cardiovascular changes in group A. The combination of PEEP and lower body positive pressure could be a satisfactory method of preventing VAE.

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