ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The optimal dose of thiopental depends both on its initial distribution kinetics, which determine its concentrations at sites of action after iv administration, and on its pharmacodynamics. The disposition of concomitantly administered thiopental and indocyanine green (ICG), a marker of intravascular space, was determined in 21 patients, aged 20–80 yr, to determine the pharmacokinetic basis of increased reactivity of the elderly to thiopental. Data obtained from frequent early arterial blood samples and the simultaneous modelling of thiopental disposition with that of ICG allow a rigorous description of early drug distribution. Their disposition is described by a two-compartment ICG model and a four-compartment thiopental model that have a common central volume, V1, the central blood pool. ICG distributes, by intravascular mixing, from V1to a peripheral blood volume that is a subset of a rapidly equilibrating (fast) peripheral thiopental compartment; elimination clearance of both drugs is modelled from these peripheral compartments. In contrast to the results of others, the results of this study demonstrate that V1does not decrease with increasing age. The only pharmacokinetic variable that changed with age is the intercompartmental clearance (Cl21) from V1to the rapidly equilibrating peripheral volume, V2, which decreased 35% between the ages of 20–80 yr. The authors suggest that V1and the intercompartmental clearances may be used together to explain smaller dose requirements in individuals with increased reactivity to thiopental; such an analysis does not predict that dose adjustments should be made on the basis of age alone.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The authors have previously attributed the mechanism for the 50–67% decrease in the required dose of thiopental for induction of anesthesia in aged human patients to a decrease in the initial distribution volume for thiopental. Using a larger group of patients and volunteers studied in the laboratory, the authors have re-examined thiopental pharmacokinetics and EEG pharmacodynamics relative to age. A population data analysis approach (NONMEM), using a three-compartment model, was used to analyze bolus and rapid iv infusion thiopental serum concentrationversustime data from 64 subjects. A one-compartment model was also used on the first 10 min of serum concentration data to focus only on the initial distribution phase. The population pharmacokinetic analysis demonstrated that when thiopental is administeredviaan iv bolus injection, traditional pharmacokinetic models limit the accurate characterization of thiopental distribution phenomena. Using the rapid iv infusion data, the pharmacokinetic mechanism for the decreased thiopental dose requirement in the elderly was a decreased rapid intercompartment clearance. Thiopental distribution from the central compartment of the three-compartment model to the rapidly equilibrating compartment (rapid intercompartment clearance) decreased 27% between the ages of 35–80 yr and decreased 34% in the one-compartment analysis. EEG spectral edgeversustime data from 37 subjects was analyzed with a semiparametric modelling approach to remove the disequilibrium between thiopental serum concentration and the spectral edge. A population data analysis (NONMEM) was performed with several pharmacodynamic models. There was no age-related change in brain responsiveness or pharmacodynamics when the spectral edge is used as a measure of drug effect.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

To compare the analgesic efficacy and plasma concentration of intramuscular (IM)versusepidural (EP) clonidine, 20 patients recovering from orthopedic or perineal surgery were randomly divided into two groups of ten. Clonidine (2 μg/kg) was administered epidurally in group 1 and intramuscularly in group 2. Analgesia was assessed using a visual analog scale (VAS) over a period of 6 h following clonidine administration. Venous blood samples were obtained at specific intervals for radioimmunoassay determination of plasma clonidine concentrations. The maximum reduction in VAS pain score was 78.5 ± 20.6% in the EP group and 68.1 ± 31.5% in the IM group (NS). Onset of analgesia was similar (within 15 min of injection), but duration tended to be longer after epidural than intramuscular administration (208 ± 87 minvs.168 ± 95 min, mean ± SD,P> 0.05). The peak plasma clonidine concentration after EP injection was 0.82 ± 0.22 ng/ml and 1.02 ± 0.76 ng/ml after IM injection. Hypotension, bradycardia, and drowsiness occurred with both methods of administration. None of these effects required treatment. Thus, in postoperative patients clonidine produces similar analgesia and side effects after parenteral or EP administration.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Protein binding of thiopental was studied in 21 samples of neonatal serum (from placental blood) and compared with protein binding in ten healthy adult volunteers. These infants ranged between 32 and 43 weeks of gestational age (mean, 37.7 weeks) and the adult age range was from 27 to 54 years (mean, 35.4 years). Because the unbound fraction of the drug is responsible for its pharmacologic effect, a marked difference in the protein binding between neonates and adults may be relevant to the clinician. Blood obtained from freshly delivered placentas or from adult volunteers was allowed to clot and the serum separated from the sample. A portion of the serum was sent for protein and bilirubin analysis and the remainder retained for study. This latter serum was combined with four concentrations of thiopental. These specimens were then ultrafiltered and the amount of thiopental in the ultrafiltrate (unbound) compared with the prefiltered amount (total), as measured by reversephase high-performance liquid chromatography. The binding studies were repeated atpH 7.2, 7.4, and 7.6 in both the adult and neonatal serum. Total protein and albumin are significantly less in neonatal serum, whereas bilirubin (total and direct) is significantly higher in neonatal serum than in adult serum (P< 0.01). Neonatal serum was associated with significantly more unbound thiopental than adult serum at all levels ofpH studied (P< 0.005). Increasing thepH resulted in less free drug in both groups, but this reached statistical significance only in the adult group (P< 0.025). Drug concentration had no effect on binding in the range examined. This increased unbound thiopental (almost twice as much as in adults) may result in increased sensitivity to thiopental in the neonatal age group.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

To determine in infants and children the neuromuscular effect of pipecuronium during alfentanil-N2O/O2anesthesia, the authors studied 32 ASA Physical Status 1 and 2 pediatric patients undergoing minor elective surgery, divided into three groups according to their age: group 1 included 12 infants, 1.9 ± 0.2 months old (mean ± SE; range, 20 days to 3 months), weighing 5.2 ± 0.3 kg; group 2, 10 infants, 6.1 ± 0.9 months old (range, 3–11 months), 6.9 ± 0.4 kg; and group 3, 10 children 5.6 ± 0.9 yr old (range, 2–9 yr), 19.6 ± 2.2 kg. Neuromuscular blockade at the ulnar nerve-adductor pollicis muscle was measured by electromyography. Incremental iv doses of pipecuronium were given (one 20 μg/kg first dose, followed by 10 μg/kg increments) to reach a 95 ± 2% twitch depression (ED95). In children ED50and ED95of pipecuronium were 45.0 ± 5.8 μg/kg (mean ± SE) and 70.5 ± 9.3 μg/kg, respectively. In 3− to 12-monthold infants ED50and ED95were 25.8 ± 1.5 μg/kg and 48.7 ± 3.5 μg/kg, respectively, and both significantly (P< 0.05) less than those in children. In 0− to 3-month-old infants ED50and ED95were 23.7 ± 1.7 μg/kg and 46.5 ± 2.9 μg/kg, respectively, and also significantly (P< 0.05) less than those measured in children. Time from maximal initial neuromuscular blockade to 75% recovery was 64.5 ± 8.8 min in children and significantly shorter (P< 0.05) in the two infant groups (0− to 3-month-old: 38.7 ± 5.7 min, 3− to 12-month-old: 43.8 ± 5.3 min, respectively). In conclusion, this study demonstrates that the neuromuscular potency of pipecuronium is increased in both groups of infants compared with that in children older than 2 yr. Furthermore, whereas pipecuronium is a long-acting neuromuscular blocking agent in children (similar to what has been reported in adults), it has only an intermediate duration of action in infants.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

In patients undergoing neurosurgical procedures at high risk for venous air embolism (VAE), the presence of a right-to-left shunt adds an additional risk for paradoxical air embolism (PAE). Although this is a rare complication, it can have devastating results. The most common form of right-to-left shunt is a patent foramen ovale (PFO), which can be detected by contrast echocardiography. This study evaluates the efficacy of preoperative precordial and intraoperative transesophageal echocardiography (TEE) to detect right-to-left shunting in patients undergoing neurosurgical procedures while in the sitting position. In 101 patients precordial contrast echocardiography was performed prior to surgery. The Valsalva maneuver was utilized as a provocative maneuver to facilitate demonstration of right-to-left shunting. Fifty-one of these patients also had intraoperative TEE monitoring. Right-to-left shunting was demonstrated in only six of the 101 patients examined. Of these, four were detected by TEE. This is less than the expected incidence based on the known incidence of PFO in the general population. The usefulness of preoperative ECHO as a screening test for PFO in patients undergoing neurosurgical procedures is limited, but when a PFO is found, valuable information is acquired to help manage these patients.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Based on a chance observation in two patients in whom the larynges could be visualized during direct laryngoscopy using topical anesthesia but not after general anesthesia and muscle paralysis, the authors postulated that there will be a shift in the position of the larynx with the onset of general anesthesia and muscle paralysis. To verify this the authors measured the position of larynx in lateral radiographs of necks taken in human volunteers when they were awake, and after induction of general anesthesia and muscle paralysis. The authors found that the hyoid bone and epiglottis were shifted anteriorly and the supraglottic region or the vestibule of the larynx was enlarged with the onset of general anesthesia and muscle paralysis. In addition, the larynx was also stretched longitudinally with wide separation of the vestibular and vocal folds. The authors conclude that consciousness is associated with tonic muscular activity that folds the larynx and partially closes it and that onset of general anesthesia and muscle paralysis opens the larynx wider and shifts it anteriorly, which might make visualization of the larynx during direct laryngoscopy difficult in some patients.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Mesenteric traction during aortic surgery produces facial flushing, reduced mean arterial pressure (MAP), and systemic vascular resistance (SVR) with increased heart rate (HR) and cardiac index (CI). Elevated 6-keto-prostaglandin-F1α(6-keto-PGF1α) suggests prostacyclin is the mediator. To test this hypothesis, the cyclooxygenase inhibitor, ibuprofen (n = 14), or placebo (n = 13) was administered to patients electively scheduled for aortic reconstruction. The hemodynamic measurements and plasma concentrations of prostanoids between groups were compared immediately before (0), and 5, 10, 15, 30, and 45 min following mesenteric traction. Following mesenteric traction significant differences (P< 0.05) were observed between the ibuprofen pretreatment and placebo group over time in SVR, MAP, HR, CI, 6-keto-PGF1α, and thromboxane B2(TXB2). Significant differences between groups at individual times were found in SVR, HR, CI, 6-keto-PGF1α, and TXB2. In the placebo group flushing was accompanied by reduced SVR and MAP and increased HR and CI. The greatest effect was seen at 10 min and resolved over 30 min. Plasma concentration of 6-keto-PGF1αincreased from 159 ± 103 (mean ± SEM) pg/ml to a peak value of 3,765 ± 803 at 10 min. A late increase in TXB2occurred with a peak value of 1,970 ± 891 (mean ± SEM) pg/ml at 30 min. In the ibuprofen pretreated group no significant changes occurred in hemodynamic measurements or concentrations of prostanoids. The inhibition of 6-keto-PGF1αand its associated hemodynamic changes in the treatment group, but not in the placebo group, confirms the hypothesis that prostacyclin is the mediator of the mesenteric traction response in abdominal aortic surgery.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

A total of 2,511 patients who received spinal anesthesia for cesarean delivery were observed for the development of postdural puncture headache (PDPH); 804 patients received a mixture of tetracaine and procaine, 942 received bupivacaine-glucose, and 765 received lidocaine-glucose. They were observed for the development of PDPH for a minimum of 72 h. PDPH occurred in 9.54% of patients who received lidocaine-glucose during the first 36 h compared with 7.64% of patients who received bupivacaine-glucose and 5.85% of patients who received tetracaine-procaine. The differences between all groups was statistically significant. No differences were found in the percentage of patients who ultimately required epidural blood patch for relief of symptoms after 36 h.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID