The volume of discard for valid blood sampling from indwelling femoral (leader cath) and radial (Venflon) arterial cannulae (with internal volume of cannula plus connecting tubing of approximately 2 ml) was investigated by analysing sequential 2-ml aliquots of 10-ml samples. The aliquots were analysed for pH, carbon dioxide tension, oxygen tension, standard bicarbonate, haemoglobin concentration, haemoglobin oxygen saturation and potassium concentration. Analysis of variance showed that, for these variables and these catheters, a valid blood sample was obtained after discarding 4 ml, but not after only 2 ml. The haemoglobin concentration, as measured by a Corning oximeter, provided good warning of inadequate discard.

Twenty patients presenting for submucous resection of the nasal septum under general anaesthesia were randomly allocated to four groups to receive either 1.0 ml 25% cocaine HCI in paraffin paste, 1.0 m125% cocaine HCI combined with 0.1% adrenaline in paraffin paste, 4.0 ml aqueous 4% cocaine HCI combined with 0.050/0 adrenaline or 4.0 ml aqueous 4% cocaine HCI on ribbon gauze applied to the nasal mucosa. Mean intraoperative blood loss was significantly decreased when the 25% cocaine 0.1% adrenaline combination in paraffin paste was used (11 (SD 8) ml, 60 (SD 30) ml, P<0.05, for adrenaline and plain paste respectively). Combination of adrenaline with cocaine in the aqueous formulation was not associated with a significant decrease in blood loss compared with aqueous cocaine alone (75 (SD 51), 96 (SD 66) ml respectively). Cocaine adrenaline paste and plain cocaine paste were associated with higher mean maximum cocaine blood concentrations (1.6 (SD 1.4), 2.0 (SD 1.5) JAg/ml respectively) when compared with aqueous cocaine adrenaline and aqueous cocaine alone (0.03 (SD 0.003), 0.5 (SD 0.3) JAg/ml respectively). Heart rate and blood pressure changes were similar in all four groups and cardiovascular toxicity was not observed. One ml of topical intranasal 25 % cocaine HCI with 0.1 % adrenaline in paraffin paste provided the best haemostasis for nasal septal surgery.