This study investigated the neuroprotective effect of acute normovolaemic haemodilution with a novel hydroxyethyl starch (130/0.4, HES) on focal cerebral ischaemia-reperfusion injury and determined optimum degree for haemodilution in the rat.

Male Sprague-Dawley rats were randomly divided into three groups (n = 10 each): hydroxyethyl starch, saline and controls. Animals in the hydroxyethyl starch and saline groups were haemodiluted until haematocrit decreased to 30% of baseline. In another experiment male Sprague-Dawley rats were randomly assigned to four groups (n = 10 each): HES30, HES25 and HES20 and controls. Rats in the HES30, HES25 and HES20 groups were haemodiluted with hydroxyethyl starch until the haematocrit decreased to 30%, 25% and 20%, respectively. At 15 min after haemodilution, all the rats were subjected to a right middle cerebral artery occlusion for 120 min. Neurologic deficit scores and infarct volumes were assessed 24 h after reperfusion.

Haemodilution with hydroxyethyl starch improved neurologic outcome (P < 0.01) and reduced infarct volume (P < 0.01) compared to saline and controls. Haemodilution with saline augmented infarct volume (P < 0.05 vs. controls). Neurologic deficit scores in HES30 and HES25 groups were significantly lower compared to controls (P < 0.05) while infarct volumes in controls and HES20 were significantly larger compared to HES30 and HES25 (P < 0.01).

This study demonstrates that acute normovolaemic haemodilution with a novel hydroxyethyl starch (130/0.4) reduces infarct volume and improves neurological outcome after focal cerebral ischaemia in a rat stroke model. Neuroprotection by haemodilution was highest at haematocrit dilution between 25% and 30%, while ischaemic injury was exacerbates when haematocrit was diluted to 20%.

The objective was to carry out a retrospective study of changes in regional cerebral oxygen saturation (rSO2) using the Somanetics Invos Cerebral Oximeter (SICO) in older patients undergoing prolonged major abdominal surgery. Since evidence is accumulating that detection and correction of falls in rSO2 may be associated with a reduced incidence of postoperative cognitive dysfunction, the study assessed the incidence and possible predisposing factors for significant falls in rSO2 and strategies for correction.

Data from 46 consecutive patients aged 55 yr or above undergoing major abdominal surgery were collected and studied. A SICO electrode was placed over the right forehead prior to commencement of anaesthesia and values of rSO2 were recorded automatically on a floppy disk at 20 s intervals throughout the procedure and until transfer of the patient to the postanaesthesia care unit. Anaesthesia and physiological data were routinely collected by the author on an anaesthetic record computer and transferred to an Excel spreadsheet for analysis.

Average duration of the surgery exceeded 7 h. Average blood loss was 1363 mL (interquartile range 500–2000). In 11 of the 46 patients the rSO2 drop exceeded 20%, and in six, there was a significant temporal association of rSO2 drop with ongoing major haemorrhage. In 23 of the 46 patients, a maximum drop in rSO2 occurred, which was about 15% or more. Fall in rSO2 in the 46 patients significantly correlated with blood loss (P < 0.05) and percentage fall in haemoglobin (Hb) (P = 0.01) but not with lowest Hb. Despite maintenance of conventional haemodynamic parameters such as systolic blood pressure (BP) in most patients, the fall in rSO2 seemed only reversible by blood transfusion. In five of the six patients who experienced the greatest decline in rSO2 during haemorrhage, there was no correlation between fall in rSO2 and systolic BP.

This retrospective study confirms that a significant reduction in rSO2 is a common accompaniment to prolonged major abdominal surgery in elderly patients, especially if associated with blood loss, and is correctable by blood transfusion. In most cases, these changes would have gone unnoticed with conventional monitoring.