Anesthesiology
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The radioactive-microsphere technique was used to determine distribution of cardiac output and regional blood flow in rhesus monkeys before and 10, 20, 40, and 80 minutes after induction of epidural anesthesia with lidocaine (1 per cent) without epinephrine. Four monkeys were studied during low epidural anesthesia (sensory level T10) and five other monkeys were studied during high epidural anesthesia (sensory level T1). During T10 epidural anesthesia. ⋯ During T1 epidural anesthesia, blood flow to the heart was significantly reduced at 10 minutes, blood flow to the liver was significantly reduced at 10 and 40 minutes, blood flows to kidneys and miscellaneous organs (lymph nodes, salivary glands, etc.) were significantly reduced at 10, 20, and 40 minutes, and blood flow to the brain was significantly reduced throughout anesthesia. Vascular resistance in the lower extremity was reduced in each monkey following epidural anesthesia, indicating arteriolar dilatation. Also, during both levels of anesthesia, the lungs received an increased proportion of the microspheres, suggesting an increased periopheral arteriovenous shunting of microspheres due to the arteriolar dilatation.
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Elevated intrathoracic pressure due to positive end-expiratory pressure (PEEP) has the potential for increasing intracranial pressure (ICP) and reducing arterial blood pressure (BP). Such changes could critically reduce cerebral perfusion pressure (CPP = BP - ICP), This possibility was investigated in 15 cats with artificially-produced expanding intracranial masses (intracranial balloon). The interrelationships among ICP and central venous and arterial pressures were observed during application and removal of graded levels of PEEP (5, 10, 15 cm H2O). ⋯ Sudden removal of or reduction in PEEP was accompanied by increases in arterial and intracranial pressures in both groups, although this response was attenuated in the cats given oleic acid. The results indicate a potential for PEEP to evoke neurolgic complications in patients who have intracranial disease and that the presence of pulmonary disease may attenuate these deleterious side effects. Monitoring of neurologic function as well as blood-gas and cardiovascular effects of PEEP in patients who have intracranial disease is suggested.