Anesthesia and analgesia
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Anesthesia and analgesia · Dec 1999
Randomized Controlled Trial Comparative Study Clinical TrialThe effect of nitric oxide on platelets when delivered to the cardiopulmonary bypass circuit.
Nitric oxide (NO) decreases platelet adhesion to foreign surfaces in the in vitro models of cardiopulmonary bypass (CPB). We hypothesized that NO, delivered into the membrane oxygenator (MO), would exert a platelet-sparing effect after CPB. Forty-seven patients scheduled for coronary artery surgery were randomized to either a NO group, in which NO (100 ppm) was delivered into the MO, or a control group, in which CPB was conducted without NO. Platelet numbers, platelet aggregation response to 2.5-20 microM adenosine diphosphate, and beta-thromboglobulin levels were measured after induction of anesthesia, after 1 h on CPB and 2 h after the end of CPB. Met-hemoglobin levels were measured during CPB. The amount of blood products administered and chest tube drainage were measured in the first postoperative 18 h. NO delivered into the MO for up to 180 min did not increase met-hemoglobin levels above 4%. NO inhibited the platelet aggregation response to 2.5 microM ADP during CPB, otherwise NO had no other detectable effect on the aggregation responses or the levels of beta-thromboglobulin. Platelet numbers were not significantly altered by NO. NO did not alter the use of blood products or chest tube drainage. In conclusion, this study suggests that NO delivered into the MO of the CPB circuit does not significantly alter platelet aggregation and numbers, and does not affect bleeding. ⋯ Nitric oxide affects platelet function. We demonstrated that nitric oxide delivered into the gas inflow of the cardiopulmonary bypass circuit membrane oxygenator does not significantly alter platelet numbers or function.
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Anesthesia and analgesia · Dec 1999
Comparative Study Clinical TrialPreoperative anxiety and intraoperative anesthetic requirements.
The purpose of this study was to determine whether larger doses of anesthetics are required in the anxious patient to establish and maintain a clinically sufficient hypnotic component of the anesthetic state. Fifty-seven women undergoing bilateral laparoscopic tubal ligation with a propofol-based anesthetic regimen were enrolled in this cross-sectional study. Trait (baseline) and state (situational) anxiety were assessed in all patients immediately before surgery, and the propofol doses required for the induction and maintenance of anesthesia were recorded. A bispectral index monitor was used to assure that the hypnotic component of the anesthetic state was the same in all patients. We found that patients with high trait anxiety required more propofol for both the induction (2.1+/-0.4 vs 1.8+/-0.3 mg/kg; P = 0.01) and maintenance of anesthesia (170+/-70 vs 110+/-20 microg x kg(-1) x min(-1); P = 0.02), compared with patients with low trait anxiety. State anxiety, however, was not found to affect the propofol doses required for the induction or maintenance of anesthesia. Multiple regression models confirmed that Trait anxiety is an independent predictor for intraoperative propofol requirements (P = 0.02). We conclude that increased baseline (i.e., trait) anxiety is associated with increased intraoperative anesthetic requirements. Thus, we suggest that the initial dose of anesthetic administered by an anesthesiologist should be modified based on the anxiety level exhibited by the patient. ⋯ The goal of this study was to assess the relationship between preoperative anxiety and intraoperative anesthetic requirements. We found that high baseline anxiety predicts increased intraoperative anesthetic requirements. We suggest that anesthesiologists should modify the initial induction dose based on the anxiety level exhibited by the patient.
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Anesthesia and analgesia · Dec 1999
Randomized Controlled Trial Multicenter Study Comparative Study Clinical TrialA comparison of levobupivacaine 0.125%, fentanyl 4 microg/mL, or their combination for patient-controlled epidural analgesia after major orthopedic surgery.
Levobupivacaine, the isolated S(-) isomer of bupivacaine, is less cardiotoxic than racemic bupivacaine in animal studies. We studied the effectiveness of patient-controlled epidural analgesia (PCEA) with either levobupivacaine 0.125% or fentanyl 4 microg/mL alone, or a combination of levobupivacaine and fentanyl in 65 patients after total joint arthroplasty in a prospective, random, double-blinded fashion. Intraoperatively, all patients received 20 mL of 0.75% levobupivacaine. Study medication was infused at an initial rate of 4 mL/h, with additional medication available on patient demand (2 mL/10 min). The combination of levobupivacaine and fentanyl produced better analgesia (longer time to first PCEA request; P = 0.007 combination versus fentanyl and P = 0.006 combination versus levobupivacaine) than either drug alone. Patients in the levobupivacaine groups had appreciable sensory blockade to pinprick with minimal motor impairment. Resting and dynamic visual analog scale pain scores were lower in the combination group than in the plain fentanyl group at 6 (P = 0.022 and 0.036) and 12 h (P = 0.002 and 0.001). The 24-h overall patient- and investigator-rated visual analog scale pain scores were also lower in the combination group (resting P = 0.007, dynamic P = 0.005). There was no significant difference among the groups in the incidence of postoperative nausea (26.2%), pruritus (9.2%), hypotension (23.1%), or sedation (0%). We conclude that the analgesic effects of levobupivacaine 0.125% and fentanyl (4 microg/mL) are additive and beneficial for the management of orthopedic surgical pain by the PCEA method. Patients in this study began demand-dosing later, reported lower pain scores, and had no greater risk of adverse events than those who were given either levobupivacaine or fentanyl alone. ⋯ We demonstrated a significant additive effect of the combination of levobupivacaine (0.125%) and fentanyl (4 microg/mL), compared with either drug alone, when using patient-controlled epidural analgesia in patients after total joint arthroplasty.
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Anesthesia and analgesia · Dec 1999
Comparative Study Clinical TrialThe hemodynamic effects of anesthetic induction in vascular surgical patients chronically treated with angiotensin II receptor antagonists.
The use of angiotensin II receptor subtype-1 antagonists (ARA), recently introduced as antihypertensive drugs, is becoming more prevalent. We studied the prevalence and severity of hypotension after the induction of general anesthesia in 12 patients treated with ARA until the morning of surgery. The hemodynamic response to induction was compared with that of patients treated with beta-adrenergic blockers (BB) and/or calcium channel blockers (CB) (BB/CB group, n = 45) and angiotensin-converting enzyme inhibitors (ACEI) (ACEI group, n = 27). A standardized anesthesia induction protocol was followed for all patients. Hypotension occurred significantly (p < or = 0.05) more often in ARA-treated patients (12 of 12) compared with BB/CB-treated patients (27 of 45) or with ACEI-treated patients (18 of 27). There was a significantly (P < or = 0.001) increased ephedrine requirement in the ARA group (21+/-3 mg) compared with the BB/CB group (10+/-6 mg) or the ACEI group (7+/-4 mg). Hypotension refractory to repeated ephedrine or phenylephrine administration occurred significantly (P < or = 0.05) more in the ARA group (4 of 12) compared with the BB/CB group (0 of 45) or the ACEI group (1 of 27), but it was treated successfully by using a vasopressin system agonist. Treatment with angiotensin II antagonism until the day of surgery is associated with severe hypotension after the induction of anesthesia, which, in some cases, can only be treated with an agonist of the vasopressin system. ⋯ Hypotensive episodes occur more frequently after anesthetic induction in patients receiving Angiotensin II receptor subtype-1 antagonists under anesthesia than with other hypotensive drugs. They are less responsive to the vasopressors ephedrine and phenylephrine. The use of a vasopressin system agonist was effective in restoring blood pressure when hypotension was refractory to conventional therapy.