Anesthesia and analgesia
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Anesthesia and analgesia · Jul 2001
The effects of vasopressin on systemic hemodynamics in catecholamine-resistant septic and postcardiotomy shock: a retrospective analysis.
We retrospectively investigated the effects of continuous arginine vasopressin (AVP) infusion on systemic hemodynamics, acid/base status, and laboratory variables in patients (mean age [mean +/- SD]= 66.3 +/- 10.1 yr) with catecholamine-resistant septic (n = 35) or postcardiotomy shock (n = 25). Hemodynamic and acid/base data were obtained before; 30 min after; and 1, 4, 12, 24, 48, and 72 h after the start of AVP infusion. Laboratory examinations were recorded before and 24, 48, and 72 h after the start of AVP infusion. For statistical analysis, a mixed-effects model was used. The overall intensive care unit mortality was 66.7%. AVP administration caused a significant increase in mean arterial pressure (+29%) and systemic vascular resistance (+56%), accompanied by a significant decrease in heart rate (-24%) and mean pulmonary arterial pressure (-11%) without any change in stroke volume index. Norepinephrine requirements could be reduced by 72% within 72 h. During AVP infusion, a significant increase in liver enzymes and total bilirubin concentration and a significant decrease in platelet count occurred. Arginine vasopressin was effective in reversing systemic hypotension. However, adverse effects on gastrointestinal perfusion and coagulation cannot be excluded. ⋯ In this retrospective analysis, the influence of a continuous infusion of an endogenous hormone (arginine vasopressin) on systemic hemodynamics and laboratory variables was assessed in patients with vasodilatory shock unresponsive to conventional therapy. Arginine vasopressin was effective in reversing systemic hypotension. However, adverse effects on gastrointestinal perfusion and coagulation cannot be excluded.
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Anesthesia and analgesia · Jul 2001
Comparative StudySodium nitroprusside compared with isoflurane-induced hypotension: the effects on brain oxygenation and arteriovenous shunting.
We compared sodium nitroprusside (SNP)-induced hypotension with 3% isoflurane-induced hypotension with regard to brain tissue oxygen pressure (PtO(2)), middle cerebral artery (MCA) blood flow, and cerebral arteriovenous shunting. Eight dogs were anesthetized with 1.5% isoflurane. After a craniotomy, a probe was inserted into the left frontoparietal brain cortex to mea-sure tissue gases and pH. Blood flow was measured in a secondary branch of the MCA by a flowprobe. Measurements were made during baseline 1.5% isoflurane, during 1.5% isoflurane and SNP-induced hypotension or 3% isoflurane-induced hypotension to a mean pressure of 60-65 mm Hg, and during continued treatment with SNP or 3% isoflurane with blood pressure support to baseline levels with phenylephrine. Shunting was calculated from arterial, sagittal sinus, and tissue (indicating capillary) oxygen content. During hypotension with SNP, PtO(2) decreased 50%, and shunting increased 50%. During hypotension with 3% isoflurane, PtO(2) and shunting did not change. Blood pressure support increased PtO(2) and MCA flow during both SNP and 3% isoflurane treatment. These results show that SNP is a cerebrovasodilator but that hypotension will decrease PtO(2), probably because of an increase in arteriovenous shunting and a decrease in capillary perfusion. ⋯ We measured brain arteriovenous shunting and tissue oxygen pressure(PtO(2))during a 40% decrease in blood pressure induced by sodium nitroprusside (SNP)or 3% isoflurane. Large-dose isoflurane maintainedPtO(2) with no change in shunting. SNP infusion decreasedPtO(2) 50%and increased shunting 50%. This suggests that SNP-induced hypotension decreases PtO(2) because of a decrease in capillary perfusion.
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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.
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Anesthesia and analgesia · Jul 2001
Randomized Controlled Trial Comparative Study Clinical TrialHyperbaric spinal ropivacaine for cesarean delivery: a comparison to hyperbaric bupivacaine.
We evaluated the clinical efficacy and safety of spinal anesthesia with 0.5% hyperbaric ropivacaine compared with 0.5% hyperbaric bupivacaine for elective cesarean delivery. Sixty healthy, full-term parturients were randomly assigned to receive either 12 mg of 0.5% hyperbaric bupivacaine or 18 mg of 0.5% hyperbaric ropivacaine intrathecally. There were no significant differences in demographic or surgical variables or neonatal outcomes between groups. Onset time of sensory block to T10 or to peak level was later in the Ropivacaine group (P < 0.05). The median (range) peak level of analgesia was T3 (T1-5) in the Bupivacaine group and T3 (T1-4) in the Ropivacaine group. Time for sensory block to recede to T10 did not differ between groups. Duration of sensory block was shorter in the Ropivacaine group (188.5 +/- 28.2 min vs 162.5 +/- 20.2 min; P < 0.05). Complete motor block of the lower extremities was obtained in all patients. Ropivacaine also produced a shorter duration of motor blockade than bupivacaine (113.7 +/- 18.6 min vs 158.7 +/- 31.2 min; P < 0.000). The intraoperative quality of anesthesia was excellent and similar in both groups. Side effects did not differ between groups. Eighteen milligrams of 0.5% hyperbaric ropivacaine provided effective spinal anesthesia with shorter duration of sensory and motor block, compared with 12 mg of 0.5% hyperbaric bupivacaine when administered for cesarean delivery ⋯ Eighteen milligrams of 0.5% hyperbaric ropivacaine provided effective spinal anesthesia with shorter duration of sensory and motor block, compared with 12mg of 0.5% hyperbaric bupivacaine when administered for cesarean delivery.