A comparison of physiological responses to percussive brain trauma in dogs and sheep

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Abstract
✓ Physiological variables were monitored in dogs and sheep after exposure of the brain to a pressure wave produced by a fluid-percussion device. Mean systemic arterial pressure (SAP), mean pulmonary arterial pressure (PAP), and pulmonary wedge pressure (PWP) were recorded prior to and following trauma. Lung lymph flows (QLYM) were measured prior to and for 2 hours after trauma. Plasma catecholamine levels were quantitated prior to and at 30 seconds following trauma. In 16 dogs, SAP increased from 123 ± 14.6 to 254 ± 60.8 mm Hg (p < 0.0001), PAP increased from 17 ± 4.4 to 27 ± 10.8 mm Hg (p < 0.05), and PWP increased from 4 ± 2.4 to 15 ± 8.8 mm Hg (p < 0.0001), all at 30 seconds posttrauma. All pressures returned to near baseline values within 6 minutes. The QLYM from the right lymph duct in 12 dogs increased from 0.82 ± 0.77 to 2.7 ± 2.1 and 1.88 ± 1.82 ml/30 min, respectively, at 30 and 120 minutes. In five dogs the plasma concentrations of dopamine, epinephrine, and norepinephrine increased from 234 ± 98 to 1906 ± 1384, 609 ± 641 to 19,813 ± 10,234, and 388 ± 194 to 3223 ± 992 pg/ml, respectively (all p < 0.01). In sheep there were no changes in SAP, PAP, PWP, QLYM, or catecholamine levels in response to percussive wave trauma up to 10 atm. Ratios of lung tissue water to dry weight were not significantly different from control animals in either species. The authors conclude that in dogs there is a profound sympathetic discharge resulting in dramatic elevations in plasma catecholamines, systemic and pulmonary artery hypertension, and an increase in pulmonary lymph flow. Sheep fail to demonstrate changes in any of these variables after severe percussive wave brain trauma.