Plasma catecholamines in the conscious rat during endotoxicosis.

Blood pressure, heart rate, and plasma catecholamines were determined in conscious unanesthetized rats given intravenous saline or endotoxin (LPS from S. enteritidis). Rats were monitored for 6 hr and survival determined at 24 hr. Blood pressure and heart rate measurements were determined using implanted arterial cannulae. The first of two protocols involved surgical implantation of cannulae 24 hr prior to the administration of endotoxin (2.0 mg/kg) or saline. Significant hypotension during the first hour following endotoxin was observed but significant increases in heart rate were not observed until 3 hr. Plasma norepinephrine (NE) and epinephrine (E) were significantly elevated at 30 min. Norepinephrine remained elevated (6 times control) during 6 hr, whereas E was elevated (60 times control) at 30 min but was less elevated at 6 hr. The second protocol involved endotoxin or saline administration immediately following implantation of cannulae. In this group, 16.7 mg/kg of endotoxin or saline was given. All animals died and plasma catecholamines were elevated at higher levels than those of the first group. Results suggest marked elevations in plasma catecholamines during endotoxicosis. Additional data analysis suggests that plasma NE and E may provide an early index of impending circulatory shock.