Effects of electroimmobilisation on blood gas and pH status in sheep

Arterial blood gases, pH and haemoglobin concentrations were monitored for 20 minutes before, during and for 120 minutes after 60 seconds of electroimmobilisation (E-IM) at current strengths of 0 mA (control), 40 mA and 60 mA in 17 Merino ewes (36.3 +/- 1.0 kg) previously prepared with unilateral carotid artery loops. E-IM elicited whole body rigidity. During E-IM, breathing was stopped for 50 +/- 3 seconds (40 mA) and 56 +/- 2 seconds (60 mA). Arterial PO2 decreased to 43.2 +/- 2.4 mmHg (5.68 +/- 0.32 kPa) (40 mA) and 36.4 +/- 1.8 mmHg (60 mA) while arterial PCO2 rose to 59.7 +/- 1.9 mmHg (40 mA) and 69.8 +/- 2.0 mmHg (60 mA). There was a significant fall in arterial pH to 7.272 +/- 0.014 (40 mA) and 7.233 +/- 0.011 (60 mA) during E-IM and arterial haemoglobin increased by 34 +/- 3 per cent and 35 +/- 3 per cent at 40 mA and 60 mA, respectively. All the arterial blood gas and pH changes were significantly greater (P less than 0.05) during E-IM at 60 mA than at 40 mA. Multiple regression analysis indicated that the decrease in arterial PO2 during E-IM was directly related to the latency to breathe while the changes in arterial PCO2 and pH during E-IM were not.2+off