Anesthesia and analgesia
-
Anesthesia and analgesia · Sep 1999
Nitrous oxide increases normocapnic cerebral blood flow velocity but does not affect the dynamic cerebrovascular response to step changes in end-tidal P(CO2) in humans.
We sought to clarify the effect of nitrous oxide (N2O) on the immediate responses of cerebral vasculature to sudden changes in arterial carbon dioxide tension in healthy humans. By use of a transcranial Doppler ultrasonography, blood flow velocity in the middle cerebral artery (V(MCA)) was measured during a step increase followed by a step decrease in end-tidal CO2 tension (PET(CO2)) between normo- and hypercapnia while subjects inspired gas mixtures containing 70%O2 + 30% N2 (control) and 70% O2 + 30% N2O (N2O) separately. During the control condition, both step increase and decrease in PET(CO2) produced rapid exponential changes in V(MCA). An increase in V(MCA) produced by the step increase in PET(CO2) was smaller (P < 0.001) and slower (P < 0.001) than a decrease in V(MCA) induced by the step decrease in PET(CO2). These general features of the dynamic cerebrovascular response were not affected by substitution of N2O for N2 in the inspired gases although N2O increased baseline V(MCA) by 15% (P < 0.001) compared with the control condition. We conclude that N2(O) in itself does not affect the dynamic cerebrovascular response to arterial CO2 changes, although it produces static mild cerebral vasodilation. ⋯ This study suggests that nitrous oxide does not affect the dynamic cerebrovascular reactivity to acute arterial carbon dioxide (CO2) changes, i.e., exponential changes in cerebral blood flow in response to step changes in alveolar CO2 tension, although it does produce a mild increase in normocapnic cerebral blood flow velocity.
-
Anesthesia and analgesia · Aug 1999
Randomized Controlled Trial Clinical TrialPostoperative analgesia with no motor block by continuous epidural infusion of ropivacaine 0.1% and sufentanil after total hip replacement.
We assessed the analgesic efficacy of postoperative epidural ropivacaine 0.1% with and without sufentanil 1 microgram/mL in this prospective, randomized, single-blinded study of 30 ASA physical status I-III patients undergoing elective total hip replacement. Lumbar epidural block using 0.75% ropivacaine was combined with either propofol sedation or general anesthesia for surgery. After surgery, the epidural infusion was commenced. Fifteen patients in each group received either an epidural infusion of 0.1% ropivacaine with 1 microgram/mL sufentanil (R + S) or 0.1% ropivacaine without sufentanil (R) at a rate of 5-9 mL/h. All patients had access to i.v. piritramide via a patient-controlled analgesia device. The R + S group consumed six times less piritramide over a 48-h infusion period than the R group (median 12.7 vs 73.0 mg; P < 0.001). Motor block was negligible for the study duration in both groups. Patient satisfaction was excellent. The incidence of adverse events, such as nausea, was similar. We conclude that a continuous epidural infusion of 0.1% ropivacaine with 1 microgram/mL sufentanil is more effective than ropivacaine alone in treating pain after elective hip replacement without motor block. ⋯ This is the first randomized study comparing the efficacy of the epidural combination of ropivacaine 0.1% and sufentanil 1 microgram/mL versus plain ropivacaine 0.1% in treating pain after hip replacement. We found that ropivacaine 0.1% and sufentanil 1 microgram/mL led to a sixfold reduction in opioid requirements after total hip replacement by producing a negligible motor block.