Venous return in hemorrhagic shock after application of military anti-shock trousers.

UNLABELLED: The effect of Military Anti-Shock Trousers (MAST) on inferior vena cava blood flow was studied during graded hypovolemia using a pump reservoir system and an in-line electromagnetic flowprobe. During hemorrhagic shock MAST inflation increased cardiac output 25.4% ( CONTROL: 0.92 +/- 0.09 l/min) and arterial pressure 50% ( CONTROL: 60 +/- 2 mmHg). The so-called "autotransfusion" effect due to blood displacement from the lower part of the body into the central circulation was found to be only 4.3 +/- 0.6 ml/kg, a volume much less than previously estimated in the literature. We conclude that MAST inflation reliably improves cardiac output and systemic blood pressure above the diaphragm in dogs subjected to hemorrhagic shock. This effect is mainly due to a diversion of the cardiac output to the upper half of the body due to impedance of flow to the abdomen and lower extremities, rather than to a significant volume shift constituting an autotransfusion of blood from the lower part of the body.

Proteolytic enzyme levels during cardiopulmonary bypass.

Pulmonary damage resembling "shock lung" is frequently seen following cardiopulmonary bypass. In many of these cases a rise in the plasma level of proteolytic enzymes has been observed. In order to establish whether changes in plasma proteinase activity occur as a result of cardiopulmonary bypass per se, or whether hemodilution and surgical tissue destruction may be responsible, three groups of animals were studied. Control dogs were anesthetized, heparinized, and transfused rapidly with Ringer's lactate to a hematocrit of less than 30%. In the second group hemodilution was combined with a sham thoracotomy. The third group was perfused for 90 minutes on total cardiopulmonary bypass at flow rates between 60 and 95 ml/kg/min using a roller pump and an infant bubble oxygenator. Serum beta-glucuronidase and acid phosphatase activity was measured by spectrophotometry immediately after anesthesia and at fixed time intervals during the experimental procedure, as well as on the second and third postoperative days. It was found that beta-glucuronidase increased 78.2 +/- 6.6% during extracorporeal circulation, while acid phosphatase rose 46.3 +/- 4.2%. Increases in enzyme activity were significantly greater in the perfused group when compared with the sham-operated and the control groups. The results suggest that the postperfusion lung syndrome may be attributable in part to proteinase release caused by blood/material interaction within the extracorporeal circuit.

Fluid shifts in the cat lung during cardiogenic shock.

Transcapillary fluid shifts after experimental myocardial infarction were measured in cats by double-isotope technique. In the control animals, pulmonary extravascular volume increased 49.2% after infarction, and intravascular volume decreased 15.8%. There was evidence of hemoconcentration, with an increase in hematocrit and a fall in plasma volume. Administration of the proteolytic enzyme inhibitor aprotinin following infarction reduced the fluid shift into the extravascular space significantly. It is concluded that the increase in pulmonary extravascular volume frequently seen after myocardial infarction is not solely the result of low output failure but may in part reflect changes in capillary permeability secondary to enzymatic damage.