Anesthesia and analgesia
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Anesthesia and analgesia · Aug 1999
Randomized Controlled Trial Comparative Study Clinical TrialPropofol versus propofol-ketamine sedation for retrobulbar nerve block: comparison of sedation quality, intraocular pressure changes, and recovery profiles.
We compared sedation quality, intraocular pressure (IOP) changes, and recovery profiles in patients who received propofol or propofol-ketamine sedation during placement of the retrobulbar nerve block (RBB). Seventy elderly patients undergoing cataract extraction according to a prospective, randomized, double-blinded protocol were preoperatively evaluated with a Mini-Mental State examination and baseline IOP. A hypnotic dose was provided with either propofol (Group P) or a propofol-ketamine (Group PK) combination. The IOP measurement was repeated, and the surgeon initiated the RBB. Supplemental study drug was given if needed. The level of sedation was considered acceptable if the patient exhibited minimal or no movement and grimacing with needle insertion. Patients were evaluated in terms of quality of sedation, cardiopulmonary stability, and recovery profile. Compared with patients in Group P, patients in Group PK had a significantly faster onset of acceptable sedation (Group P 235 +/- 137 s versus Group PK 164 +/- 67 s) and required significantly less supplemental sedation (Group P 1.1 +/- 1.9 mL versus Group PK 0.15 +/- 0.3 mL). Additionally, none of the Group PK patients required ventilatory assistance, but two patients in Group P required assisted mask ventilation. In conclusion, the addition of ketamine (13.2 +/- 3.3 mg) to propofol (44 +/- 11 mg) decreased the hypnotic requirement and improved the quality of sedation without prolonging recovery. ⋯ Anesthesiologists frequently perform retrobulbar blocks while simultaneously providing sedation. Using ketamine to supplement propofol sedation provided a faster onset and improved the quality of sedation during the retrobulbar block procedure.
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Anesthesia and analgesia · Aug 1999
Effects of one minimum alveolar anesthetic concentration sevoflurane on cerebral metabolism, blood flow, and CO2 reactivity in cardiac patients.
We investigated the cerebral hemodynamic effects of 1 minimum alveolar anesthetic concentration (MAC) sevoflurane anesthesia in nine male patients scheduled for elective coronary bypass grafting. For measurement of cerebral blood flow (CBF), a modified Kety-Schmidt saturation technique was used with argon as an inert tracer gas. Measurements of CBF were performed before the induction of anesthesia and 30 min after induction under normocapnic, hypocapnic, and hypercapnic conditions. Compared with the awake state under normocapnic conditions, sevoflurane reduced the mean cerebral metabolic rate of oxygen by 47% and the mean cerebral metabolic rate of glucose by 39%. Concomitantly, CBF was reduced by 38%, although mean arterial pressure was kept constant. Significant changes in jugular venous oxygen saturation were absent. Hypocapnia and hypercapnia caused a 51% decrease and a 58% increase in CBF, respectively. These changes in CBF caused by variation of Paco2 indicate that cerebrovascular CO2 reactivity persists during 1 MAC sevoflurane anesthesia. ⋯ We used a modified Kety-Schmidt saturation technique to investigate the effects of 1 minimum alveolar anesthetic concentration (MAC) sevoflurane on cerebral blood flow, metabolism, and CO2 reactivity in cardiac patients. We found that the global cerebral blood flow and global cerebral metabolic rate of oxygen remained coupled and that cerebrovascular CO2 reactivity is not impaired by the administration of 1 MAC sevoflurane.
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Anesthesia and analgesia · Aug 1999
The combined effects of sevoflurane and remifentanil on central respiratory activity and nociceptive cardiovascular responses in anesthetized rabbits.
We studied the effects of sevoflurane and remifentanil, alone and in combination, on phrenic nerve activity (PNA), resting heart rate (HR), arterial pressure (MAP), and changes in HR (delta HR) and MAP (delta MAP) evoked by electrical stimulation of tibial nerves in anesthetized rabbits. The 50% effective dose (95% confidence intervals) for the depressant effects of sevoflurane on delta HR, delta MAP, and PNA were 2.3 (1.8%-2.6%), 2.7 (2.3%-2.9%), and 3.4 (3.1%-3.7%), respectively, and for remifentanil were 0.100 (0.050-0.132), 0.850 (0.720-1.450), and 0.090 (0.080-0.145) microgram.kg-1.min-1, which were reduced to 0.046 (0.021-0.065), 0.110 (0.080-0.200), and 0.030 (0.020-0.040) microgram.kg-1.min-1, respectively, by 1% sevoflurane. Depression of evoked cardiovascular responses relative to PNA was greater for sevoflurane and less for remifentanil both alone and in combination with sevoflurane. Sevoflurane acted synergistically with remifentanil on PNA and delta MAP, but not delta HR, for which their combined effect was additive. Coadministration of 1% sevoflurane with the highest infusion rate of remifentanil (1.6 micrograms.kg-1.min-1) used during combined administration reduced resting HR and MAP by 25% (P < 0.05) and 41% (P < 0.05), respectively, which was greater than the predicted reductions of only 14% and 15% if their combined effects had been additive. We conclude that sevoflurane caused a relatively greater depression of nociceptive cardioaccelerator and pressor responses compared with PNA and vice versa for remifentanil. When coadministered, their combined effects on PNA, resting HR, MAP, and delta MAP were synergistic, whereas they were merely additive for delta HR. ⋯ Although sevoflurane caused relatively greater depression of nociceptive cardiovascular responses compared with phrenic nerve activity, remifentanil either alone or combined with sevoflurane caused a much greater depression of phrenic nerve activity than cardio-accelerator and pressor responses. This could imply that, during major surgery using anesthesia combining sevoflurane and remifentanil, spontaneous ventilation is not acceptable, and depression of the resting circulation may be much greater than anticipated.
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Anesthesia and analgesia · Aug 1999
Randomized Controlled Trial Multicenter Study Comparative Study Clinical TrialThe effects of rapacuronium on histamine release and hemodynamics in adult patients undergoing general anesthesia.
Neuromuscular blocking drugs may have variable effects on heart rate (HR) and blood pressure. Rapacuronium is a rapid-acting, steroidal-derived neuromuscular blocking drug whose hemodynamic effects have not been characterized. We studied the effects of 1, 2, and 3 mg/kg rapacuronium on histamine release, HR, and blood pressure in 47 ASA physical status II or III adult patients after the induction of anesthesia with etomidate/fentanyl/N2O. Plasma histamine concentrations were measured before induction and immediately before and 1, 3, and 5 min after the rapid administration of rapacuronium. Mean arterial pressure (MAP) decreased after rapacuronium administration, but there were no significant differences among the groups for changes in HR or MAP, and there was no correlation between changes in MAP or HR and increases in histamine levels. There were no changes in HR or MAP among five patients who had significant (> or = 1 ng/mL) increases in histamine from baselin. Seven patients had bronchospasm without increases in plasma histamine levels. Rapacuronium 2-3 mg/kg increased plasma histamine levels. However, clinically significant histamine-related sequelae did not occur in this population with 1- to 3-mg/kg doses of rapacuronium, and cardiovascular changes were not directly correlated with histamine release. Rapacuronium administration can produce hypotension via mechanisms that do not seem to be related to histamine release. ⋯ Rapacuronium, a new steroidal-derived muscle relaxant, may release histamine and produce slight changes in blood pressure and heart rate after administration.