Journal of neurosurgical anesthesiology
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J Neurosurg Anesthesiol · Jul 1994
Case ReportsDetection of site of air entry in venous air embolism: role of Valsalva maneuver.
Venous air embolism in posterior fossa surgery is a well-documented complication. Various highly sensitive devices help in early detection of air embolism. In management of air embolism, sealing the site of air entry is an important step in preventing further episodes. Here we discuss the importance of inspiratory hold after lung inflation (Valsalva maneuver) in helping to localize the site of air entry and its role in the management of venous air embolism observed in two cases of posterior fossa mass, operated in sitting position.
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J Neurosurg Anesthesiol · Jul 1994
Ketamine directly dilates bovine cerebral arteries by acting as a calcium entry blocker.
This in vitro study was performed to determine the role of calcium in ketamine-induced cerebral vasodilation. Isolated bovine middle cerebral arteries were cut into rings to measure isometric tension development or into strips to measure radioactive 45Calcium (45Ca) uptake. Ketamine produced direct relaxation of arterial rings; the relaxation was attenuated in Ca(2+)-deficient media. ⋯ In Ca(2+)-deficient media containing potassium or the stable thromboxane A2 analogue, ketamine produced competitive inhibition of subsequent Ca(2+)-induced constriction. Ketamine blocked potassium- and thromboxane A2-stimulated 45Ca uptake in a dose-dependent manner, but had no effect on basal 45Ca uptake, the externally bound 45Ca content, or the volume of the 3H-sorbitol space. These results indicate that ketamine can directly dilate cerebral arteries by acting as a calcium channel antagonist; ketamine inhibits 45Ca uptake through both potential-operated (potassium) and receptor-operated (thromboxane A2) channels in cerebrovascular smooth muscle.
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J Neurosurg Anesthesiol · Apr 1994
Soluble fibrin and D-dimer as detectors of hypercoagulability in patients with isolated brain trauma.
To test the hypothesis that hypercoagulability after brain trauma was related to the severity of injury and also to outcome, new coagulation markers were used in 20 patients with isolated brain trauma. In addition to routine coagulation tests, soluble fibrin (SF), D-dimer, and antithrombin (AT) levels were assessed. Thirteen of 20 patients had a Glasgow coma score (GCS) of < or = 7 on admission and severe disability (SD) or worse on the Glasgow outcome scale (GOS). ⋯ Six of 13 patients with a significant drop in AT levels had a bad outcome (D or V) whereas only two of seven patients without AT consumption did poorly. Routine coagulation studies were often pathologic, i.e., reduced platelet count, but there was no relation to outcome. Increased SF and D-dimer levels at admission followed by a secondary decrease in AT concentration and platelets seem to be good markers of the posttraumatic hypercoagulation often seen after brain injury.(ABSTRACT TRUNCATED AT 250 WORDS)
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Hydroxocobalamin is a powerful cyanide antidote that prevents sodium nitroprusside-induced cyanide toxicity. The pharmacokinetics of an i.v. bolus of hydroxocobalamin (70 and 140 mg/kg) were studied in conscious dogs (n = 6). Plasma hydroxocobalamin concentrations were measured using derivative spectrophotometry. ⋯ At 70 mg/kg, which is the recommended dose in acute cyanide poisoning, the elimination half-life was 7.36 +/- 0.79 h, the volume of distribution was 0.49 +/- 0.10 L/kg, and the total clearance 0.58 +/- 0.11 L/h. At high doses, hydroxocobalamin has a short elimination half-life and a limited volume of distribution that exceeds blood volume. These results could be useful in elaborating guidelines for the administration of hydroxocobalamin, when repetitive bolus and/or continuous infusion is required.