Surgery
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A disturbance of cerebral neurotransmitters and an accumulation of octopamine, a putative false neurotransmitter, have been found in patients with uremic encephalopathy who manifest disorientation, somnolence, asterixis, and coma--symptoms also seen in portal systemic encephalopathy (PSE). Altered plasma concentrations of the neutral amino acids (NAAs) and increased blood-brain NAA transport may play a role in PSE, and in the present study plasma amino acid concentrations and blood-brain barrier NAA transport were investigated in rats with acute and chronic uremia. Acute uremia was produced by unilateral nephrectomy and occlusion of the renal artery of the remaining kidney for 70 minutes; the animals were studied 24 hours later. ⋯ The blood urea nitrogen (BUN) level in rats with acute uremia increased to 108 mg/dl, in rats with chronic uremic 54 mg/dl, and in sham-operated rats 22 mg/dl. In both uremic groups there was a decrease in plasma branched-chain AAs. In the brain these AA levels were normal, while levels of phenylalanine, tyrosine, and histidine were increased in uremic rats.
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Analysis of the case histories of 17 patients who developed subglottic obstruction following cricothyroidotomy shows that all 10 patients with chronic stenosis had acute laryngeal pathology at the time of initial operation. Seven patients were identified as having acute subglottic obstruction with granulation tissue. Although these patients were effectively managed by local means, ineffective management of intratracheal granulation tissue may convert a minor, temporary problem into a serious chronic obstruction. Cricothyroidotomy is appropriately used for prolonged airway access only in patients free of acute laryngeal pathology.
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Comparative Study
Activated clotting time monitoring of intraoperative heparinization: our experience and comparison of two techniques.
The activated clotting time (ACT) has been used clinically for 41/2 years to monitor the adequacy of intraoperative heparinization in both cardiopulmonary bypass (CPBP) and peripheral vascular surgery (PVS) patients. Since January, 1976, we have operated on 440 PVS patients in our institutions, of whom 255 had intraoperative monitoring of heparinization by means of the ACT test; an additional 185 patients received heparin according to an empiric protocol. An automated machine for determining the ACT (Hemochron) had been used on the last 28 patients in the ACT group. We conclude that: (1) the ACT is an acurate method of monitoring anticoagulation during PVS, (2) the Hemochron is a simple and effective machine to perform the ACT, (3) values obtained by the Hemochron generally exceed those of the ACT done by hand by approximately 20 seconds at lower levels of heparin and are equal at higher levels of heparin, (4) supplemental heparin was required in 22% of our patients to maintain their ACT values at twice control values, (5) the response to heparin is twofold: an initial sensitivity or resistance followed by an independent and variable rate of consumption, and (6) the ACT is a useful method for predicting inadequate heparin reversal or heparin rebound at the conclusion of the operation.