Pulmonary Damage and Head Injury ∗

Summary

Experiments were carried out to investigate the effect of severe head injury on the lungs of 42 unanesthetized rats. Cerebral trauma was induced by means of a captive bolt mechanism producing sufficient force to cause immediate unconsciousness or death, apparently of respiratory origin, usually within a few minutes. Rats which showed any signs of regaining consciousness after trauma (36%) were immediately given a lethal dose of sodium pentobarbital. Gross pulmonary damage including edema and congestion and increased lung wt./body ratios were found in 92% of those rats dying from the impact and in 40% of the rats killed by the lethal dose of anesthetic given after impact. Pathology reports indicated the occurrence of moderate to severe brain and lung damage in traumatized rats. Control experiments in which animals succumbed during exposure to low oxygen have demonstrated that this pulmonary pathology cannot be attributed simply to low oxygen. Results indicate that hypoxia alone in rats does not induce the severe form of pulmonary damage resulting from cerebral trauma. It is tentatively concluded that these pulmonary changes are due in large part to nervous mechanisms of central origin. The data lend substantial support to the evidence previously reported that similar pathology which attends severe epileptiform convulsions induced by the toxic action of oxygen at high pressure and by chemical convulsants such as Metrazol and picrotoxin is in large part of CNS origin, and that this effect is mediated through the sympathetics and alterations in the cardiopulmonary hemodynamics and possibly also through changes in the pulmonary parenchyma itself.