ISSN:0003-3022    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The effect of systemic (intravenous) medetomidine, an alpha-2 adrenoceptor agonist, on pain thresholds was studied in healthy human subjects (n = 6). Medetomidine produced a dose-dependent (cumulative doses: 25 and 50 μg) sedative effect evaluated by visual analog scale. Also, a dose-dependent decrease of blood pressure but not of heart rate was seen after administration of medetomidine. Pain threshold to electric stimulation of the tooth pulp and cutaneous heat pain threshold were uninfluenced by medetomidine. An index of cutaneous thermal sensitivity to innocuous stimuli, the width of the thermoneutral zone, also was uninfluenced by medetomidine. Medetomidine produced a significant attenuation of the affective-motivational component (unpleasantness) of tourniquet-induced ischemic pain, whereas the sensory-discriminative component (pain magnitude estimate) of the ischemic pain was not attenuated. The results suggest that systemic medetomidine alone at subanesthetic but sedative and hypotensive doses does not significantly influence the intensity and thresholds of experimental pain, whereas the affective-motivational component of pain can be attenuated.

ISSN:0003-3022    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

To determine whether transesophageal echocardiography could be used to estimate intraoperative cardiac output, the authors studied 35 consecutive patients undergoing cardiovascular surgery (coronary artery disease [n = 22], aortic valve disease [n = 5], mitral valve stenosis [n = 5], peripheral vascular disease [n = 3]). Two-dimensional echocardiographic and pulsed-wave Doppler signals of the pulmonary artery and mitral valve flow velocity were obtained simultaneously with therntodilution measurements of cardiac output. Cardiac output derived from pulsed Doppler imaging of pulmonary artery systolic flow velocity modestly correlated with the thermodilution-derived cardiac output (r = 0.65), but output determined from the mitral valve diastolic flow velocity did not (r = 0.24). Transesophageal echocardiography of pulmonary artery systolic flow satisfactorily detected intraoperative increases in cardiac output greater than 15% (sensitivity, 71%; specificity, 82%) but not decreases (sensitivity, 54%; specificity, 90%). Although this technique identifies increases in cardiac output greater than 15%, it does not detect decreases as accurately as those detected by thermodilution measurements. At this time, therefore, transesophageal Doppler echocardiography has significant limitations as an off-line monitor of cardiac output.

ISSN:0003-3022    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Ten patients with parenchymal acute, respiratory failure (ARF) underwent computed tomography (CT) scans while in the supine and prone positions. At equal levels of positive end-expiratory pressure, the authors measured the changes of CT density in dorsal and ventral basilar lung regions induced by the change of position as well as alterations of gas exchange. The level of venous admixture did not change with body position. The CT scan image of each lung was fractionated into ten levels from dorsal to ventral, each constituting 10% of the lung height. After measuring each lung fraction, the volume, the average CT number, its frequency distribution, and the expected normal value, we computed the lung tissue mass, the excess tissue mass, and the fraction of normally inflated tissue (excess tissue mass = amount of “tissue,‘’ which includes edema, cells, and blood in excess of the expected normal value). We also estimated the superimposed hydrostatic pressure on each lung region. We found that the excess lung tissue mass is independent of position. However, in patients in the supine position, lung CT density increased and regional inflation decreased from ventral to dorsal, suggesting progressive deflation of gas-containing alveoli along the gravity gradient A similar ventral–dorsal deflation pattern occurred within 10 min in patients in the prone position. We conclude that the lung in patients with ARF behaves like an elastic body with a diffusely increased mass; dependent lung regions are compressed by the pressure of overlying structures. Reversal of gravitational forces induced atelectasis of previously inflated lung regions and inflation of previously atelectatic regions but did not change the overall efficiency of oxygen exchange (right-to-left intrapulmonary shunt [Qsp/Qt].

ISSN:0003-3022    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Spontaneous movements during induction of anesthesia with propofol were studied in 21 children aged 6–12 yr. The children were randomly assigned to group A (propofol 3 mg · kg-1), B (propofol 5 mg · kg-1), or C (thiopental 5–7 mg · kg-1). A baseline electroencephalogram (EEG) was recorded during 10 min in children awake, supine with eyes closed and opened, and then from the beginning of induction until 5 min after tracheal intubation. Spontaneous movements were observed in all children in group A but only in 14% in groups B and C. The induction EEG sequences were similar for the three groups: after a mean latency of 12 s, the tracing showed an increase in frequency from 9 to 10 Hz (alpha waves) to more than 14 Hz (beta waves). This transition lasted approximately 2 s, followed by delta waves (2–3 Hz) that continued for 1–2 min. Finally, beta waves reappeared and progressively but incompletely replaced delta waves during the next 5 min. Neither spikes, spike-wave patterns, rhythmic theta waves, nor burst suppressions were observed. Spontaneous movements were recorded on videotape and analyzed after the completion of the study by a neurologist unaware of patient treatment. Videotape analysis of the periinduction period showed spontaneous movements to be dystonic and choreiform with flexion, twisting, or extension movements of all extremities. All movements occurred coincident with the appearance of delta waves on the EEG. Their dystonic nature and the absence of EEG abnormalities suggest a subcortical origin and argue against associated cortical epileptic activity.

ISSN:0003-3022    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The effectiveness of oral transmucosal fentanyl citrate (OTFC) as preanesthetic medication was compared with oral meperidine, diazepam, and atropine (MDA) in 40 pediatric patients scheduled to undergo repair of congenital heart defects. In a double-blinded manner, patients received a fentanyl lollipop (20–25 μg/kg) and a placebo oral solution (0.4 ml/kg) (n = 20) or a placebo lollipop and an oral solution (0.4 ml/kg) of meperidine (1.5 mg/kg), diazepam (0.2 mg/kg), and atropine (0.02 mg/kg) (n = 20). The patient's vital signs, systolic and diastolic blood pressures, heart rate, respiratory rate, and oxyhemoglobin saturation (Spo1), as well as activity and apprehension scores were evaluated and recorded at baseline and at 10-min intervals. The patient's emotional status at the time of parental separation and at induction of anesthesia were also assessed. Side effects and onset of action were observed. After OTFC, onset of sedation was significantly faster than with the oral solution of meperidine, diazepam, and atropine. In both groups there was no significant change in heart rate. Although systolic blood pressure, diastolic blood pressure, and respiratory rate showed statistically significant decreases, these changes were not clinically significant The child's emotional status at the time of separation from the parents and during induction was similar in both groups. Side effects with OTFC were more frequent: nose itching occurred in 65%, body itching in 10%, and vomiting in 30%. Two patients (10%) in the OTFC-treated group became hypoxemic (Spo1< 90) and required supplemental oxygen. In the group receiving oral meperidine, diazepam, and atropine, 10% had mild facial pruritus and 5% complained of a dry mouth. When compared with oral meperidine, diazepam, and atropine, OTFC in the dosage used is readily acceptable, provides more rapid sedation, but has considerably more preoperative side effects. Consequently, OTFC in the dose used in this study cannot be recommended as a preanesthetic medication for patients with congenital heart disease.

ISSN:0003-3022    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The authors compared the pharmacodynamics of sufentanil with those of fentanyl using the electroencephalogram (EEG) as a measure of opioid drug effect. Sixteen patients were given a rapid infusion of sufentanil (18.75 μg/min) during EEG recording. To quantitate the opioid-induced slowing of the EEG, the authors analyzed its power spectrum and calculated the spectral edge. An inhibitory sigmoid Emaxmodel of the maximal decrease in spectral edge produced by the opioid related spectral edge values to serum concentrations of sufentanil. The resulting data for the pharmacodynamic parameters of sufentanil were compared with fentanyl parameters that were obtained by reanalysis from an identically conducted, previously published study. The half-time of blood-brain equilibration (T1/2Keo) was not statistically different between sufentanil and fentanyl (6.2 ± 2.8vs.6.6 ± 1.7 min, mean ± SD, respectively). The intrinsic potency of sufentanil, as measured by the serum concentration needed to cause half the maximal EEG slowing (IC50), was 12-fold greater (0.68 ± 0.31 ng/ml) than that of fentanyl (8.1 ± 2.2 ng/ml). The second part of the study verified the hypothesis that administration of equipotent bolus doses would produce equal onset times. Bolus injections of either 125 μg of sufentanil or 1,250 μg of fentanyl were given during EEG recording. The time from injection to 50% maximal EEG slowing (T50) was calculated for each patient. The values for T50for the two groups did not differ. The authors conclude that fentanyl and sufentanil have similar pharmacodynamic profiles, the former being 12 times more potent than the latter.

ISSN:0003-3022    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Because only limited and controversial data exist concerning the respiratory effects of clonidine in humans, the authors evaluated the respiratory effects of clonidine alone and in combination with morphine, in 12 healthy adult males. Subjects received clonidine (0.3 −0.4 ing orally), morphine (0.21 mg/kg intramuscularly), or the same doses of the two drugs combined, at three separate sessions in a randomized fashion. The study was balanced for all possible sequences of drug administration. Blood pressure, heart rate, hemoglobin oxygen saturationviafinger pulse oximetry, and ventilatory and occlusion pressure responses to CO2were obtained before and 20, 40, 60, 90, 120, 180, 240, 300, and 360 min after administration of drug or drug combination. Systolic blood pressure decreased significantly only in the clonidine and clonidine plus morphine groups (P< 0.05). Hemoglobin oxygen saturation decreased by a statistically significant (P< 0.05), though clinically minor, degree only in the morphine or morphine plus clonidine groups. Clonidine alone did not depress the slope of either the ventilatory or the occlusion pressure response to CO2. In addition, clonidine did not significantly worsen morphine-induced depression of the slope of the ventilatory and occlusion pressure responses in the drug combination group. Both the ventilatory and occlusion pressure responses to CO2were shifted to the right in all three drug groups (P< 0.05) but were shifted to a significantly lesser degree by clonidine alone than by morphine and morphine plus clonidine. In healthy young adult males, clonidine alone produces little respiratory depression and does not significantly potentiate morphine-induced respiratory depression.

ISSN:0003-3022    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Hepatic venous oxygen saturation (Shvo2) was continuously monitored in 33 consecutive patients undergoing hepatic lobectomy. Fiberoptic pulmonary artery catheters were inserted into the hepatic vien (HV) and in the pulmonary artery through the right internal jugular vein before anesthetic induction. The success rate and mean time for HV catheterization were 100% and 14 min, respectively. The only complication of the procedure was nonsustained atrial or ventricular arrhythmias. Eighteen patients showed decreases in Shvo2to less than 30% at skin incision, at temporary cessation of hepatic inflow, and/or at surgical manipulation of the liver. Clinical HV catheterization was easy to accomplish and may be a valuable technique in studying the extent and siginificance of hepatic ischemia during liver surgery.

ISSN:0003-3022    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Fentanyl, alfentanil, and sufentanil have important pharmacokinetic and pharmacodynamic differences. Selecting one of these opioid analgesics as an adjunct to general anesthesia requires appreciation of the relationship between the pharmacokinetic and pharmacodynamic characteristics of these drugs and the onset of and recovery from drug effect. Using a pharmacokinetic-pharmacodynamic model, the authors simulated the decrease in plasma fentanyl, alfentanil, and sufentanil concentration after intravenous administration by either bolus injection, brief infusion, or prolonged infusion. The percentage change in concentration, rather than absolute concentration, was simulated to permit comparison of the relative opioid concentration independently of drug potency. These computer simulations quantified the relationship between infusion duration and the time required for recovery after termination of the infusion. The analysis suggests that alfentanil is best used for operations longer than 6–8 h when a rapid decrease in effect site (i.e., biophase) opioid concentration is desired after discontinuation of the if fusion. Alfentanil may also be the most appropriate drug to provide a transient peak effect after a single bolus. Although sufentanil has longer distribution and elimination half-lives than alfentanil, recovery from sufentanil infusions may be more rapid than recovery from alfentanil infusions for operations shorter than 6–8 h. These computer simulations demonstrate that simply comparing pharmacokinetic parameters (e.g., half-lives) of different drugs will not predict the relative rates of decrease in effect site concentrations after either an intravenous bolus or a continuous infusion.

ISSN:0003-3022    

出版商:OVID    

年代:1991

数据来源: OVID