Anesthesia and analgesia
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Anesthesia and analgesia · Dec 1999
Randomized Controlled Trial Comparative Study Clinical TrialA comparative study of the postoperative allogeneic blood-sparing effect of tranexamic acid versus acute normovolemic hemodilution after total knee replacement.
Both acute normovolemic hemodilution (NVHD) and tranexamic acid (TA) are potentially useful allogeneic blood conservation strategies after total knee replacement. However, the relative efficacy of these blood-sparing techniques is unknown. Therefore, to compare the postoperative allogeneic blood sparing of NVHD and TA after total knee replacement, we investigated 40 patients in a prospective, single-blinded study protocol. In Group TA, 30 min before deflating the limb tourniquet, an IV infusion of TA, 15 mg/kg, was administered over a 30-min period. Thereafter, a constant IV infusion of 10 mg x kg(-1) x hr(-1) was administered until 12 h after deflation of the limb tourniquet. Before induction of anesthesia, NVHD patients were bled to a target hematocrit of approximately 28%. Intravascular blood volume was maintained with lactated Ringer's solution. All autologous blood was transfused at the end of the surgery. Postoperatively, hematocrit was measured daily. In all cases, a hematocrit <27% was the postoperative transfusion trigger. Before discharge, deep vein thrombosis was excluded by Echo Doppler. Three months after surgery, the incidence of delayed thromboembolic events was assessed. The two groups were demographically comparable. In Group NVHD, 843 mL+/-289 of autologous blood was removed. Despite autologous blood transfusion, during the early postoperative period and until the third postoperative day, the NVHD group had significantly (P < 0.01) lower mean hematocrits when compared with the TA group. Thereafter, because of a significantly (P < 0.0008) greater allogeneic blood requirement in the NVHD group, no statistically significant difference in mean hematocrit recordings was noted among the groups. Blood accumulation in the surgical drain 12 h postoperatively, was significantly (P < 0.0008) higher in the NVHD group (259 mL+/-156) when compared with the TA group (110 mL+/-62). Significantly (P < 0.0008) more allogeneic blood was transfused in the NVHD group (19 U/13 patients) when compared with the TA group (2 U/2 patients). No abnormal Echo Doppler studies were reported. During the 3-mo follow-up period, a deep vein thrombosis and pulmonary embolus were documented in one patient in the NVHD group. We conclude that perioperative hemodynamic stability and allogeneic blood sparing is superior after tranexamic acid administration when compared with normovolemic hemodilution. ⋯ For total knee replacement, when compared with normovolemic hemodilution, tranexamic acid administration is associated with superior perioperative hemodynamic stability and allogeneic blood sparing.
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Anesthesia and analgesia · Dec 1999
Randomized Controlled Trial Clinical TrialThe failure of negative pressure rewarming (Thermostat) to accelerate recovery from mild hypothermia in postoperative surgical patients.
The Thermostat device (Aquarius Medical Corp., Phoenix, AZ) is used in a new technique to accelerate recovery from hypothermia by mechanically distending blood vessels in the hand, thereby increasing transfer of exogenous heat to the body core. We evaluated the use of the Thermostat device in patients with mild postoperative hypothermia (< 36 degrees C). We studied adult patients undergoing elective surgery, general anesthesia, and neuromuscular blockade. Patients with an initial postoperative tympanic membrane temperature < 36 degrees C were randomized into two groups: 1) Thermostat, which consisted of a hypothermia warming mitt/seal and thermal exchange chamber for 60 min, and 2) conventional treatment, which consisted of warm blankets and/or radiant heat. Of the 191 patients enrolled, 60 (31%) developed hypothermia and were randomized to receive the Thermostat (n = 30) or conventional methods (n = 30). Fourteen patients in the Thermostat group and 17 patients in the conventional group rewarmed to 36 degrees C before discharge from the recovery room (P is not significant). There were no differences in vital signs, rewarming time, time to discharge from the recovery room, or postoperative temperature between groups. We conclude that patients with mild postoperative hypothermia rewarmed in a similar fashion, regardless of whether the Thermostat or conventional methods were used. ⋯ We found that a commercially available negative pressure rewarming device (Thermostat; Aquarius Medical Corp., Phoenix, AZ) was not effective in accelerating rewarming in postoperative hypothermic surgical patients after general anesthesia.
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Anesthesia and analgesia · Dec 1999
Attenuated additional hypocapnic constriction, but not hypercapnic dilation, of spinal pial arterioles during spinal ropivacaine.
Ropivacaine constricts spinal vessels. Because the CO2 response of spinal vessels is similar to that of cerebral vessels, we tested to see if hypocapnia would cause further spinal vasoconstriction during ropivacaine administration. In 12 pentobarbital-anesthetized dogs, spinal pial arteriolar diameter was measured using a closed spinal window preparation. Either ropivacaine solution (0.1%; n = 6) or artificial cerebrospinal fluid (n = 6) was infused continuously into the spinal window. After a period of hypocapnia (Paco2, 20-25 mm Hg) had been induced, inspired CO2 levels were adjusted to produce normocapnia (35-40 mm Hg) followed by hypercapnia (55-60 mm Hg). When the desired Paco2 was reached, measurements were made of the arteriolar diameter and physiological variables. During normocapnia, ropivacaine infusion produced a significant constriction of pial arterioles, whereas artificial cerebrospinal fluid caused no change. Hypocapnia induced a much smaller (almost nonexistent) additional vasoconstriction in the ropivacaine group than in the control group (P < 0.01). The final hypercapnic vasodilation was somewhat greater during ropivacaine (P < 0.05 versus control group). Topical ropivacaine induced no change in hemodynamic variables. We conclude that hypocapnia of the magnitude tested did not cause further constriction in spinal vessels during spinal ropivacaine. ⋯ During topical application of the local anesthetic ropivacaine in dogs, hypocapnia (Paco2, 20-25 mm Hg) induced almost no additional constriction of spinal arterioles, and the hypercapnic vasodilation was maintained. These data suggest that an additional constriction in spinal vessels is unlikely when hypocapnia occurs during spinal ropivacaine.
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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
Randomized Controlled Trial Multicenter Study Comparative Study Clinical TrialA comparison of the analgesic efficacy of 0.25% levobupivacaine combined with 0.005% morphine, 0.25% levobupivacaine alone, or 0.005% morphine alone for the management of postoperative pain in patients undergoing major abdominal surgery.
We compared the relative efficacy of the combination of the single-isomer local anesthetic levobupivacaine and the opioid analgesic morphine versus both drugs alone for postoperative epidural analgesia after major abdominal surgical procedures. Thoracic epidural anesthesia was produced and maintained with levobupivacaine 0.75% in combination with general inhaled anesthesia without opioids. Patients were randomized to one of three postoperative treatment groups: 1) a combination of levobupivacaine 0.25% and morphine 0.005%; 2) levobupivacaine 0.25%; or 3) morphine 0.005%. Postoperatively, all epidural infusions were commenced at a rate of 4 mL/h. Patients could receive a 4 mL-bolus dose and an increase in the epidural infusion rate by 2 mL/h on request for supplemental analgesia. Patients were also allowed ketorolac as a supplemental analgesic at any time after the first analgesic request. Patients in the combination group had longer times to request for supplemental analgesia as compared with the levobupivacaine only group (P < 0.05) and a trend toward longer time to request as compared with the morphine only group (P = 0.066). Patients in the combination group had lower visual analog scale pain scores at rest and activity at 4 and 8 h and fewer requests for supplemental ketorolac (P < 0.05). In conclusion, this study demonstrates a significant improvement in postoperative analgesic efficacy with the combination of levobupivacaine and morphine for continuous epidural analgesia after major abdominal surgical procedures. ⋯ A significant improvement in postoperative analgesic efficacy is demonstrated with the thoracic epidural administration of the combination of the single-isomer local anesthetic levobupivacaine 0.25% and morphine 0.005% in patients after major abdominal surgical procedures as compared with either drug used alone.