Protective effects of β blockade on pulmonary function when intracranial pressure is elevated

Intracranial pressure (ICP) was increased by hyperosmolar intracerebral infusion in dogs and the cardiopulmonary and catecholamine (CA) responses followed for 4 h. Increased ICP evoked persistent increases in endogenous CAs, pulmonary vascular pressures, pulmonary blood volume, and venous admixture. Other dogs similarly monitored were treated with a β-blocking dose of propranolol 25 min after the onset of increased ICP. Although catecholamines were increased, elevated pulmonary pressures and venous admixture returned to control levels. CO and heart rate (HR) were reduced after β blockade but systemic vascular resistance increased. It was concluded that increased ICP induces sustained increases in CAs which adversely affect pulmonary pressures and shunting. Selective β blockade reverses these effects and may be useful in patients with evidence of sympathetic overactivity and progressive hypoxemia after head injury.