Anesthesia and analgesia
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Anesthesia and analgesia · Jul 2001
Clinical TrialThe relationship between hirudin and activated clotting time: implications for patients with heparin-induced thrombocytopenia undergoing cardiac surgery.
Anticoagulation with recombinant hirudin (r-hirudin) (Refludan) has been suggested as an alternative to heparin for patients with heparin-induced thrombocytopenia requiring cardiac surgery. We sought to develop a modified activated coagulation time (ACT) that would allow quantification of the levels of r-hirudin required during cardiopulmonary bypass (CPB). Twenty-one patients scheduled for elective cardiac surgical procedures requiring CPB were enrolled in this IRB-approved study. R-hirudin was added to blood specimens obtained before heparin administration (before CPB) and 30 min after heparin neutralization with protamine (after CPB) to result in concentrations of 0, 2, 4, 6, 7, or 8 microg/mL. Kaolin/ACT and complete blood count measurements were assayed in native specimens (first 10 patients, Phase I) or in specimens mixed with equal volumes of commercial normal plasma (second 11 patients, Phase II). In Phase I, good (r(2) = 0.83) linear relationships between ACT values and r-hirudin concentrations (< or =4 microg/mL) were observed in specimens obtained before CPB. However, ACT values were markedly prolonged (P < 0.0001) by r-hirudin in specimens obtained after CPB, with ACT values generally exceeding the ACT's detection limit (>999 s) at hirudin concentrations >2 microg/mL. In patient specimens mixed with normal plasma (Phase II), ACT/hirudin relationships (i.e., hirudin/ACT slope values obtained with hirudin concentration < or =4 microg/mL) in the post-CPB period (0.022 +/- 0.004 microg. mL(-1). s(-1)) were similar (P = 0.47) to those (0.019 +/- 0.004 microg. mL(-1). s(-1)) obtained in the pre-CPB period. Accordingly, a significant relationship between normal plasma-supplemented ACT values and predilution hirudin concentration was obtained in the post-CPB (hirudin = 0.039ACT - 4.34, r(2) = 0.91) period. Although our data demonstrate that the ACT test cannot be used to monitor hirudin during CPB, the addition of 50% normal plasma to post-CPB hemodiluted blood specimens yields a consistent linear relationship between hirudin concentration and ACT values up to a predilution concentration of 8 microg/mL. Plasma-modified ACT may be useful in monitoring hirudin anticoagulation during CPB. ⋯ A modified activated clotting time test system that may be helpful in monitoring hirudin anticoagulation in patients with heparin-induced thrombocytopenia during cardiac surgery with cardiopulmonary bypass is described.
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Anesthesia and analgesia · Jul 2001
The accuracy of coagulation tests during spinal fusion and instrumentation.
Patients undergoing major spine surgery may acquire a perioperative coagulopathy from dilution of coagulation factors and/or platelets or fibrinolysis. The mechanisms of the coagulopathy and role of coagulation testing during these procedures are poorly defined. Theoretically, coagulation tests could be used perioperatively to determine which patients are at risk for significant bleeding and guide transfusion therapy. We retrospectively evaluated the sensitivity, specificity, and accuracy of coagulation tests in predicting excessive surgical bleeding in 244 consecutive patients undergoing thoracic, lumbar, or sacral spinal fusion with or without instrumentation. Excessive bleeding was reported by the surgeon in 39 of the patients and was defined as recurrent microvascular bleeding despite adequate use of electrocautery and suture or decreased clot formation of blood pooled within the surgical field. Patients with excessive clinical bleeding sustained larger estimated blood losses than those with normal hemostasis. The total number of allogeneic red blood cells, platelets, and fresh frozen plasma units were also larger in patients with excessive bleeding noted during surgery. The intraoperative coagulation tests with the most sensitivity and specificity were the international normalized ratio (INR), prothrombin time (PT), and activated partial thromboplastin time (aPTT). The INR had a sensitivity of 94%, a specificity of 88%, and an accuracy of 0.9 at a value of 1.4 (normal, 0.8-1.2). The PT had a sensitivity of 90%, a specificity of 64%, and an accuracy of 0.73 at a value of 13.5 s (normal, 8.4-12.0 s). The aPTT had a sensitivity of 85%, a specificity of 64%, and an accuracy of 0.71 at a value of 30.9 s (normal, 23-37 s). The thromboelastogram values were of marginal use. We conclude that the INR, PT, and aPTT may be helpful in guiding transfusion therapy in patients undergoing major spine surgery. ⋯ Patients undergoing major surgery to the spine often acquire a perioperative coagulopathy. The prothrombin time and activated partial thromboplastin time had the greatest sensitivity and specificity for predicting bleeding in major surgery of the spine. The test values that differentiated normal from excessively bleeding patients could be used to guide transfusion therapy during surgery.
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Anesthesia and analgesia · Jul 2001
Case ReportsTerlipressin for treating intraoperative hypotension: can it unmask myocardial ischemia?
After administration of terlipressin to treat hypotension related to induction of general anesthesia, profound hypertension occurred in association with myocardial ischemia and occlusion of the left anterior descending coronary artery. The authors emphasize cautious use of this drug because of such adverse events.
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Anesthesia and analgesia · Jul 2001
Randomized Controlled Trial Comparative Study Clinical TrialThe effects of single or multiple injections on the volume of 0.5% ropivacaine required for femoral nerve blockade.
We compared the effects of using a single- or multiple-injection technique on the volume of 0.5% ropivacaine required to block the femoral nerve, in a prospective, randomized, blinded fashion in which 50 premedicated patients received a femoral nerve block with 0.5% ropivacaine by use of a nerve stimulator and either a single- (n = 25) or multiple- (n = 25) injection technique. Muscular twitches were elicited at < or =0.5 mA before anesthetic injection. The designated volume of local anesthetic was equally divided among contraction of the vastus medialis, vastus intermedius, and vastus lateralis for the multiple injections, or it was injected at the contraction of the vastus intermedius with motion of the patella for the single injection. The local anesthetic volumes were varied for consecutive patients by using an up-and-down staircase method; a blinded observer determined the adequacy of nerve blockade (loss of pinprick sensation in the medial, patellar, and lateral portions of the knee, with concomitant block of the quadriceps muscle) 20 min after injection. The mean (95% confidence interval) volume required for blocking the femoral nerve with the multiple-injection technique (14 [12-16] mL) was significantly smaller than that observed with the single injection (23 [20-26] mL) (P = 0.001). According to logistic regression analyses, the 95% effective volumes of ropivacaine required to block the femoral nerve within 20 min after injection were 29 and 21 mL with a single or multiple injection, respectively. We conclude that searching for multiple muscular twitches reduces the volume of 0.5% ropivacaine required to produce blockade of the femoral nerve. ⋯ We evaluated the effects of using a single- or multiple-injection technique on the volume of 0.5% ropivacaine required to block the femoral nerve. The 95%effective concentration values for producing the same degree of sensory and motor blockade of the femoral nerve within 20 min after injection were 29 mL after elicitation of a patella twitch and 21 mL when the three main branches of the femoral nerve were identified, potentially leading to an important benefit for patients receiving peripheral nerve blocks.