Pulmonary edema associated with increased intracranial pressure is a well known phenonemon. The mechanism is unknown. Experimental evidence suggests that a massive sympathetic discharge occurs which leads to peripheral vasoconstriction, central mobilization of blood volume and inadequate relaxation or response of the left ventricle. Subsequently, there is an increase in total peripheral resistence, left atrial and pulmonary wedge pressures, fall in cardiac output and pulmonary edema. Pretreatment with various agents (sympatholytic, anti-epinephrine or general anesthesia) will prevent or ameliorate the lung damage. If massive sympathetic discharge is responsible serum catecholamine levels should be elevated. Catecholamine levels have not been studied in pulmonary edema secondary to increased intracranial pressure. The objective of the research is to determine whether or not pulmonary edema associated with elevated intracranial pressure in unanesthetized dogs is secondary to a massive sympathetic discharge with elevated serum and/or cerebral spinal fluid catecholamine levels. An experimental model is developed. Three catheters (pulmonary artery thermal dilution, arterial and cisterna magna) will be inserted. Burr holes will be made in the head and capped. The dogs will be allowed to recover and divided into control and experimental groups. In the experimental group intracranial pressure will be elevated via saline infusion through an opening in the capped burr holes. The arterial, pulmonary artery and wedge, and cisterna magna pressures will be continuously monitored. Cardiac output will be determined by a thermal dilution technique and computer. Serum samples for catecholamine levels will be obtained. H3-tyrosine will be injected intravenously and cerebrospinal fluid catecholamine (dopamine, norepinephrine and their metabolites) samples collected. Intracranial pressure will not be elevated in the control group. Both groups will be sacrificed. Any animal that has an elevated lung weight body weight ratio and/or decreased lung dry weight:lung wet weight ratio past 2 standard deviations above the mean of the control animals will be considered to have developed pulmonary edema. In those experimental animals who developed pulmonary edema the derived values (cardiac output, catecholamine levels, etc.) obtained will be compared to the values obtained on the same animal after the imposition of elevated cerebral s (Text Truncated - Exceeds Capacity)