Lung innervation and the hemodynamic response to 7% sodium chloride in hypovolemic dogs

A pulmonary vagal reflex triggered by passage of hypertonic saline through the pulmonary circulation has been proposed as one of the mechanisms by which hypertonic saline resuscitates dogs in hemorrhagic shock. Thirteen anesthetized dogs with denervated left lung lobes were subjected to a standard hemorrhage model to evaluate this purported reflex. We then infused 7% NaCl (4 ml/kg) into either the innervated (six dogs) or the denervated (seven dogs) pulmonary circulation. There were no differences in cardiac output, mean arterial pressure, right atrial pressure, heart rate, or peripheral vascular resistance between groups during a 1 hr period after 7% NaCl infusion. Changes in hematocrit, total plasma protein, and osmolality after 7% NaCl administration suggested that plasma volume expansion had occurred and was similar between groups. We conclude that a pulmonary reflex elicited by hypertonic saline does not contribute to the beneficial hemodynamic effects associated with administration of 7% NaCl during hemorrhagic shock.