EFFECTS OF TRIMETAPHAN AND NICARDIPINE ON EXPERIMENTAL PULMONARY AIR EMBOLISM IN DOGS

Abstract

Experimental study of air embolism was conducted to elucidate the effects of trimetaphan (TMP) and nicardipine (NCP) on the hemodynamics and the minimum air volume capable of penetrating from pulmonary artery to systemic circulation (the threshold air volume) in dogs. Existence of air bubbles in the left atrium or the aorta were visually confirmed using transesophageal echocardiography. The 14 dogs were classified into two groups, TMP group and NCP group. Air embolisms were produced by air infusion through an inserted pulmonary artery catheter. The threshold air volume under TMP administration was significantly attenuated compared with control (without TMP) ; these median ± quartile deviation (Q. D.) values were 0.50±0.19 ml/kg in control, 0.20±0.15 ml/kg in 15% mean artery pressure (MAP) reduction (p<0.01 vs. control) and 0.10±0.04 ml/kg in 30% MAP reduction (p<0.01 vs. control). There was no significant diffesence in the threshold air volume under NCP administration. Mean pulmonary arterial pressure (MPAP) was significantly decreased after TMP administration ; these mean ± standard deviation (S. D.) were 17.0±2.6 mmHg in control, 14.6±1.7 mmHg in 15% MAP reduction (p<0.05 vs. control) and 14.1±2.4 mmHg in 30% MAP reduction (p<0.05 vs. control). There was no significant MPAP change in NCP group. All MPAP values were significantly increased after air injection. The increasing rate in NCP group tended to be higher than in TMP group : 48.8% in NCP and 33.9% in TMP at 15% MAP reduction, and 44.5% in NCP and 32.5% in TMP at 30% MAP reduction. We concluded that NCP and TMP had different responsibility to the stimuli of air embolism, and NCP would be a more optimal vasodilator than TMP during neurosurgical procedures in the sitting position.