Thoracic epidural anesthesia has been used to manage intraoperative and postoperative pain for thoracic surgical patients with general anesthesia recently. And this combined anesthesia has been associated with less sedation, earlier ambulation,
blunting
of the stress response and better pain control in the postoperative period. But the effects of thoracic epidural anesthesia on pulmonary shunt, pulmonary vasoactivity and oxygenation are still unknown.
The author has investigated the effects of thoracic epidural anesthesia on pulmonary hypertension induced by acute diffuse alveolar hypoxia and Nw-nitro-L-arginine(L-NNA) in 12 mongrel dogs. Acute diffuse alveolar hypoxia which is similar to the
early
stage of acute respiratory failure ma induce the pulmonary hypertension. And L-NNA, inhibitor of endothelium derived relaxing factor(EDRF), may also induce pulmonary hypertension under hypoxic state.
The measurements were made three times, the first was baseline at room air ventilation. Following baseline recordings, saline 4 ml(group A, n=6) or 2% lidocaine 4 ml (group b, n=6) was injected through the epidural catheter and ventilation was
started
with hypoxic gas mixture(10% O2, 90% N2). The second measurements was made 30 min after the hypoxic ventilation and third was 20 min after infusion of L-NNA(50 mg/kg mixed with distill water 50 ml, infusion rate is 50 ml/20min) under the
continuous
ventilation with hypoxia gas mixture.
@ES The results were as follows:
@EN 1) There were significant changes in mean pulmonary arterial pressure, pulmonary vascular resistance in group A(p<0.05) and in arterial and mixed venous oxygen tension, arterial and mixed venous oxygen content, intrapulmonary shunt in both
groups(p<0.05) 30 minutes after hypoxia but there were not significant differences between groups.
2) There were significant changes in mean pulmonary arterial pressure, in group B (p<0.05) and pulmonary vascular resistance, systemic vascular resistance and mixed venous oxygen tension and content in both groups (p<0.05) 20 miniutes after
infusion of
L-NNA under the continuous ventilation with hypoxic gas mixture but there were not significant differences between groups, But there were significant changes in central venous pressure in group B(p<0.05) and significant differences between
groups(p<0.05) at 20 miniutes after infusion of L-NNA.
These results indicate that thoracic epidural anesthesia does not influence the pulmonary hypertension directly and does not produce any unfavorable hemodynamic events during pulmonary hypertension induced by acute diffuse alveolar hypoxia and
N2-nitro-L-arginine. Therefore thoracic epidural anesthesia shoud be valuable assistant to the general anesthesia for pulmonary hypertensive patients. (Korean J Anesthesiol 1995; 29: 317~328)
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