Anesthesiology
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Jugular venous hemoglobin desaturation during the rewarming phase of cardiopulmonary bypass is associated with adverse neuropsychologic outcome and may indicate a pathologic mismatch between cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2). In some studies, rapid rewarming from hypothermic cardiopulmonary bypass results in greater jugular venous hemoglobin desaturation. The authors wished to determine if rewarming rate influences the temperature dependence of CBF and CMRO2. ⋯ Cerebral venous hemoglobin desaturation with rapid rewarming is caused by an increase in CMRO2 that is temporarily greater than the increase in CBF. This mismatch may indicate a transient abnormality in flow-metabolism coupling, or the effect of temperature gradients on oxygen transfer from hemoglobin to brain.
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In upper abdominal or chest surgery, the segmental approach to thoracic epidural space has the advantage of reducing the total dose of local anesthetic needed. This approach, however, is associated with greater risk of neurologic damage or dural puncture. The aim of this study was to assess the success and the degree of difficulty in advancing a 19-G catheter from the lumbar epidural space to the thoracic level in patients aged 0-96 months. ⋯ The 19-G catheter is inappropriate for use in reaching the thoracic epidural space by the lumbar approach. Easy entrance of a catheter is not a reliable sign of having reached the desired level.
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The chemical breakdown of isoflurane, enflurane, or desflurane in dried carbon dioxide absorbents may produce carbon monoxide. Some mass spectrometers can give false indications of enflurane during anesthetic breakdown. ⋯ Trifluoromethane causes the inappropriate indication of enflurane by mass spectrometry, and indicates isoflurane and desflurane breakdown. Because the ratio of carbon monoxide to trifluoromethane varies with conditions, this technique cannot be used to quantitatively determine the amount of carbon monoxide to which a patient is exposed. If any warning of anesthetic breakdown results from this technique then remedial steps should be taken immediately to stop patient exposure to carbon monoxide. No warning can be provided for the breakdown of enflurane by this technique.
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Administration of serotonin2 (5-HT2) receptor agonists in pigs triggers malignant hyperthermia (MH) and psychotic-like behavior. Both can be reduced by 5-HT2 receptor antagonists. Furthermore, an increase in the plasma concentration of 5-HT has been found during onset of halothane-induced MH in pigs. Therefore, in this study, the in vitro effects of the 5-HT2 receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) were investigated in muscle specimens from MH-susceptible (MHS) and -negative (MHN) patients. ⋯ A functional or structural altered serotonin system might be involved in the development of MH in humans.
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Clinically, differential block is manifested by the loss of small fiber mediated sensation (e.g., temperature) two or more dermatomes beyond the sensory limit for large fiber mediated sensations. These observations support the belief that sensitivity to local anesthetics is inversely proportional to axon diameter. This study reports the first measurements of differential sensitivity to lidocaine in individual myelinated and unmyelinated mammalian dorsal root axons. ⋯ Although no difference in sensitivity to the conduction blocking effects of lidocaine could be demonstrated among dorsal root axons, myelinated axons were more sensitive to the conduction velocity slowing effects of lidocaine. This differential effect cannot explain clinical observations of differential nerve block. Differential sensory block with lidocaine may depend on factors (e.g., physiologic function) related only indirectly to individual axon conduction velocity (diameter).