Effect of naloxone on the pulmonary vascular responses to graded levels of intracranial hypertension in anesthetized sheep

Abstract

We increased intracranial pressure (ICP) in anesthetized sheep for 3 h by connecting the cisterna magna to an elevated reservoir of buffered saline. We monitored systemic and pulmonary vascular pressures, pulmonary blood flow, and the flow of lymph from the lungs. The volume and protein concentration of the lymph were used to assess changes in lung vascular permeability-surface area. Extravascular lung water was measured postmortem, and in vivo indicator dilution studies were used to measure permeability-surface area product (PS urea) of the lung circulation for a small hydrophillic molecule (14C-urea) and extravascular water volume (VH2O). These studies were done in 16 sheep with ICP raised to 0, 60, or 100 mmHg. Thirteen other sheep received naloxone before and during elevation of ICP to 0, 60, or 100 mmHg. Elevation of ICP increased pulmonary artery pressure (

Control: 16 +/- 3 cmH2O; ICP: 60 mmHg = 16 +/- 2 cmH2O; ICP: 100 mmHg = 23 +/- 2 cmH2O), cardiac output (

Control: 2.7 +/- 0.1 L/min; ICP: 60 mmHg = 3.3 +/- 0.05, p less than 0.05; ICP: 100 mmHg = 5.3 +/- 1.0, p less than 0.05), lung lymph flow (

Control: 94 +/- 8% baseline; ICP: 60 mmHg = 193 +/- 25% baseline, p less than 0.05; ICP: 100 mmHg = 285 +/- 38% baseline, p less than 0.05), PS urea (

Control: 7.0 +/- 0.5 ml/s; ICP: 60 mmHg = 11.0 +/- 3.7 ml/s; ICP: 100 mmHg = 12.4 +/- 1.3 ml/s, p less than 0.05), and VH2O (CONTROL: 93 +/- 8% baseline; ICP: 60 mmHg = 112 +/- 6% of baseline; ICP: 100 mmHg = 129 +/- 13% of baseline, p less than 0.05) proportional to the level of ICP. Sheep with ICP raised to 100 mmHg had modestly increased lung water (pulmonary edema).(ABSTRACT TRUNCATED AT 250 WORDS)