Effects of air injection on hemodynamics and sympathetic nerve activity in urethane-anesthetized rabbits
Ogura, S.; Aibiki, M.; Honda, K.; Umegaki, O.; Shirakawa, Y.; Seki, K.; Nishiyama, T.; Ogli, K.
Masui. Japanese Journal of Anesthesiology 42(8): 1162-1170
1993
ISSN/ISBN: 0021-4892 PMID: 8366556 Document Number: 413231
We designed this experiment to evaluate effects of intravenous bolus injection of air (0.5 ml cntdot kg-1) on systemic blood pressure (SBP), central venous pressure (CVP), and renal nerve activity (RNA) in urethane-anesthetized rabbits. Animals were divided into the following three groups: animals with neuraxis intact (I group, N=5), cervical vagotomized animals (V group, N=5) and sinoaortic denervated animals (SAD group, N = 4). All animals were placed on the right-side down position to avoid effects of the posture throughout the experiments of air embolism. In the I group, air caused profound hypotension (from 95+-10 to 54+-15 mmHg) associated with a significant increase in CVP (from 2+-2 to 7+-3 mmHg) twenty seconds after the injection of air. In spite of the significant hypotension, RNA response did not show any increase for twenty seconds. This response was followed by an augmentation in RNA thirty seconds after air injection. In contrast, vagotomized animals exhibited a significant RNA increase (147 +- 11% of the control) in response to a decrease in SBP (from 93 +- 6 to 78 +- 5 mmHg) and an increase in CVP ten seconds after the administration of air. In SAD group, a rapid and remarkable decline in SBP (from 85 +- 13 to 47 +- 12 mmHg) occurred ten seconds after the injection of air. Despite this hypotension, RNA decreased nearly to a noise level after administration of air. Since blood pressure in this group fell to approximate 30 mmHg, this initial reduction in RNA changed to an increase to a higher level than that in the other groups. Five minutes after the injection of air, animals in the group I sustained a significant fall in SBP while animals in the group V did not show a marked hypotension. Further, in the group SAD, all animals expired within five minutes after the administration. These results indicate that vagal afferents from cardiopulmonary region may modulate baroreceptor reflex responses to the hypotension induced by a bolus injection of air and may be involved in the development of the hypotension during air embolism.