The newly developed supralaryngeal airway Streamlined Liner of the Pharynx Airway (SLIPA™) has been compared successfully to the LMA™, but the haemodynamic response to its insertion has not been evaluated in a randomised study. We compared haemodynamic and Bispectral index (BIS) responses to insertion of the SLIPA™ with classic LMA™ after standardising the anaesthetic technique using BIS to monitor and control the anaesthetic depth. One hundred patients were randomised to receive either a classic LMA™ or SLIPA™ following induction with fentanyl and propofol titrated to a target BIS of 40 and compared heart rate, mean arterial pressure and BIS responses to insertion. There was a significant rise in mean arterial pressure from the pre-stimulus value (73.8 [10.6] mmHg, mean ± SD) at two and three minutes (P <0.05) following insertion of the LMA™ with maximum rise (80.8 [11.5] mmHg) seen at two minutes. There was a significant rise in mean arterial pressure from the pre-stimulus value (73.2 [12.6] mmHg) at one, two, three, four and five minutes (P <0.05) following insertion of the SLIPA™ with maximum rise (86.9 [15.1] mmHg) observed at three minutes. Mean arterial pressure was significantly higher (P <0.05) with SLIPA™ at two, three, four and five minutes. BIS increased significantly (P <0.05) at one, two, three, four and five minutes following insertion of both the devices, but there was no significant difference between the groups. There was a significantly higher (P=0.001) incidence of blood on the device with the SLIPA™ (20/50 vs. 6/50 with LMA™). Thus, insertion of SLIPA™ causes significantly higher blood-pressure response but similar BIS response compared to the LMA™.

Respiratory physiological deadspace (VDphys) during normocapnic ventilation under anaesthesia was studied in 253 patients scheduled for elective non-thoracic surgery. Subjects were ventilated with SERVO 900B ventilator using CO 2 analyser 930 (Siemens-Elema Sweden) to adjust minute volume sufficient to maintain end-tidal carbon dioxide fraction (F É CO 2) around 5.5kPa with normocapnic confirmation using arterial blood gas analysis. VDphys was calculated using Enghoff's modification of Bohr's equation. VDphys and deadspace to tidal volume ratios (VD/VT) in male patients were 142.6±28.4 ml and 0.37±0.068 respectively and were significantly higher than that in females (119.4±35.6 ml and 0.36±0.067). Males had significantly higher VDphys/mass (2.5±0.68 ml.kg) compared with females (2.2±0.54 ml/kg, P<0.001) but significantly lower body mass index (BMI) (20.67±3.2 in males and 22.47±4.1 in females, P<0.001). VDphys showed positive correlation with weight, height and body surface area (BSA) but VDphys/kg showed negative correlation with BMI. Multiple regression analysis produced a best fit equation for V Dphys=9.7+64.3 2BSA+13.51S where S=1 for females and 2 for males.

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