Anesthesiology
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Comparative Study
Flow velocity measurements as an index of cerebral blood flow. Validity of transcranial Doppler sonographic monitoring during cardiac surgery.
Transcranial Doppler sonography is increasingly used to monitor changes in cerebral perfusion intraoperatively. However, little information is available about the validity of velocity measurements as an index of cerebral blood flow (CBF). The purpose of this study was to compare invasive and Doppler-derived measurements of cerebral hemodynamic variables during coronary artery bypass graft surgery. ⋯ Hypothermic CPB seems to alter the relation between global CBF and flow velocity in basal cerebral arteries. Inconsistency in directional changes in CBF and VMCA at this stage of surgery might be attributable to changes in middle cerebral artery diameter, red blood cell velocity spectra, and regional flow distribution. Although changes in mean VMCA before and after CPB appear to parallel changes in mean CBF, individual responses of VMCA cannot reliably predict percentage changes in CBF. Furthermore, Doppler sonographic PI and RI cannot provide an approximation of changes in CVR during cardiac surgery.
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Comparative Study
Preoperative myocardial cell damage in patients with unstable angina undergoing coronary artery bypass graft surgery.
Troponin-T is one of the contractile proteins of the myocardium. Its release into the circulation indicates various degrees of myocardial cell damage. Troponin-T may be measured in serum with a recently developed enzyme immunoassay. This immunoassay was used to evaluate the preoperative myocardial cell damage in patients with stable and unstable angina undergoing elective coronary artery bypass graft surgery, and it was compared with conventional assays of creatine kinase (CK) MB isoenzyme activity and mass. ⋯ The study data suggest that many patients with unstable angina undergoing elective coronary artery bypass graft surgery have already increased troponin-T levels preoperatively, although conventional biochemical markers such as CK-MB activity and mass are at a normal range. Increased troponin-T and normal CK-MB concentrations may reflect some degree of ischemic myocardial cell damage. Because of the small number of patients in the study, the influence of preoperative myocardial injury on perioperative outcome could not be clarified.
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Comparative Study
Postdural puncture headache and spinal needle design. Metaanalyses.
Attempts have been made to reduce the incidence of postdural puncture headache (PDPH) after spinal anesthesia by changing the size and design of the needle. We wished to determine whether these strategies are effective in reducing PDPH and whether they affect the incidence of back pain and the failure rate of spinal anesthesia. ⋯ We conclude that a noncutting needle should be used for patients at high risk for PDPH, and the smallest gauge needle available should be used for all patients.
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Ulnar neuropathy is well-recognized as a potential complication of procedures performed on anesthetized patients. However, reported outcomes and risk factors for this problem are based on small series and anecdotes. ⋯ These data suggest that perioperative ulnar neuropathies are associated with factors other than general anesthesia and intraoperative positioning. Men at the extremes of body habitus who have prolonged hospitalizations are particularly susceptible to development of ulnar neuropathies.
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Hyperventilation has been recommended to increase blood pH during metabolic acidosis. However, hypocapnia may adversely affect arterial blood oxygenation, especially in the presence of lung disease. We therefore studied the effects of metabolic acidosis, with and without normalization of pH by hyperventilation, on pulmonary gas exchange in dogs with permeability pulmonary edema. ⋯ Hyperventilation to normalize blood pH during hydrochloric acid-induced metabolic acidosis did not adversely affect pulmonary gas exchange in dogs with permeability pulmonary edema.