摘要:

The effect of trimethaphan (Arfonad) infusion on platelet function was prospectively evaluated in 38 (n = 38) patients (28 patients receiving trimethaphan, ten control patients) undergoing elective cardiac surgery. Any patient with a positive history for the ingestion of medication known to interfere with platelet function was excluded from the study. Following induction of anesthesia with fentanyl (and prior to cardiopulmonary bypass) 28 patients (n = 28) received trimethaphan as clinically indicated to maintain a mean blood pressure of 80 mmHg. The infusion rate and total dose of trimethaphan delivered was recorded for each patient. The evaluation of platelet function was performedviaadenosine diphosphate (ADP) and epinephrine-induced platelet aggregation tests. The administration of trimethaphan failed to result in any detrimental effect on platelet function as assessedviathese aggregation studies. Template bleeding times were also performed on all study patients. Bleeding time measurements performed in patients following trimethaphan administration were unchanged from baseline values. Platelet aggregation studies and bleeding time performed in control group following the administration of fentanyl (30 μg/kg) plus enflurane (inspired concentration 0.5–1 %) did not reveal any deviation from baseline values. These results are in contrast to a previous study that demonstrated a negative effect upon platelet function following sodium nitroprusside administration (at clinically acceptable doses). These data demonstrate that trimethaphan provides control of arterial pressure with preservation of platelet function.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Thirty-six former preterm infants undergoing inguinal hernia repair were studied. All were ≤51 weeks postconceptual age at the time of operation. Patients were randomly assigned to receive general or spinal anesthesia. Group 1 patients received general inhalational anesthesia with neuromuscular blockade. Group 2 patients received spinal anesthesia using 1 % tetracaine 0.4–0.6 mg/kg in conjunction with an equal volume of 10% dextrose and 0.02 ml epinephrine 1: 1000. In the first part of the study, infants randomized to receive spinal anesthesia also received sedation with im ketamine 1–2 mg/ kg prior to placement of the spinal anesthetic (group 2 A). The remainder of group 2 patients did not receive sedation (group 2 B). Respiratory pattern and heart rate were monitored using an impedance pneumograph for at least 12 h postoperatively. Tracings were analyzed for evidence of apnea, periodic breathing and/or bradycardia by a pulmonologist unaware of the anesthetic technique utilized. None of the patients who received spinal anesthesia without ketamine sedation developed postoperative bradycardia, prolonged apnea, or periodic breathing. Eight of nine infants (89%) who received spinal anesthesia and adjunct intraoperative sedation with ketamine developed prolonged apnea with bradycardia. Two of the eight infants had no prior history of apnea. Five of the 16 patients (31%) who received general anesthesia developed prolonged apnea with bradycardia. Two of these five infants had no prior history of apnea. When infants with no prior history of apnea were analyzed separately, there was no statistically significant increased incidence of apnea in children receiving generalversusspinal anesthesia with or without ketamine sedation. Because of the small numbers of patients studied, and the multiple factors that may influence the incidence of postoperative apnea (e.g., prior history of neonatal apnea), standard postoperative respiratory monitoring of these high-risk infants is still recommended following all anesthetic techniques.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

This study was designed to assess the relationship between MAC and hypertension. To this purpose, MAC of halothane was determined in fully inbred spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). Because MAC determination was performed in animals whose lungs were mechanically ventilated, the adequacy of the ventilation was initially established in 20 rats equally divided into SHR and WKY, and instrumented with catheters in the abdominal aorta. Subsequently, MAC of halothane was determined in 40 rats equally divided into SHR and WKY, including those instrumented. There were no differences in MAC of halothane between SHR (n = 20) and WKY (n = 20) (1.08 ± 0.02%vs. 1.11 ± 0.02%). Subgroup analysis indicated that MAC of halothane was not affected by the presence of an arterial catheter in the abdominal aorta (SHR 1.09 ± 0.06%vs. 1.08 ± 0.02%; WKY 1.15 ± 0.04%vs. 1.08 ± 0.02%). The authors' data provide experimental evidence that MAC is not affected by either chronic hypertension or limited instrumentation.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The interactions of the opioid and adrenergic systems were investigated in the guinea pig myenteric plexus longitudinal muscle preparation. Morphine and azepexole (a highly selective α2-adrenergic agonist) inhibit the electrically induced contractions with ED50 of 1.9 × 10−7M and 3.1 × 10−6M, respectively. The effect of morphine but not that of azepexole was competitively antagonized by naloxone. Stimulation of the preparation at 10 Hz was used to induce endogenous opioid release that was unaffected by azepexole. The authors' findings indicate that the effects of morphine and azepexole are additive, but that there is no direct interaction between the opioid and adrenergic receptors in the ileum. These observations provide some additional insight into the ability of α2-agonists to enhance the effects of opioids and inhalation anesthetics.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The effects of isoflurane on segmental spinal cord potentials and heterosegmental slow positive potentials in response to fore- and hindpaw stimulation were studied in the rat. The heterosegmental slow positive potential and late (second) component of the slow positive wave (P2) of segmental spinal cord potential, thought to be primary afferent depolarization, an agent of presynaptic inhibition activated by a feedback loopviasupraspinal structures, were greatly suppressed by the anesthetic. In contrast the negative wave (N1) of segmental spinal cord potential, believed to be synchronized activity of dorsal horn neurons, was only minimally affected. No differential effects of isoflurane on spinal cord potentials activated by fore- and hindpaws were found. Thus, the inhibitory activities of the spinal cord, particularly those produced by a feedback loopviasupraspinal structures, are suggested to be highly vulnerable to isoflurane.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Hypotension related to the intraoperative use of desmopressin acetate to improve platelet function following cardiopulmonary bypass has recently been reported. To investigate the direct vascular actions of this drug as a potential mechanism of its induced hypotension, cumulative, dose-dependent (3.7 × 10−10to 1.2 × 10−7M) effects of desmopressin were studied in isolated phenylephrine precontracted rings of rat and rabbit thoracic aorta and rabbit pulmonary artery. Desmopressin was a potent vasodilator of all vessel types studied with significant (P< 0.05) vasodilation beginning at 7.5 × 10−9M. Vascular relaxation of all vessels was greater when the vascular endothelium was intact (P< 0.05). Indomethacin potentiated (P< 0.05) vascular relaxation in rat and rabbit aortic rings and partially inhibited (P< 0.05) relaxation in rabbit pulmonary artery rings. Selective antagonists of vasopressin V1(d(CH2)5- Tyr(Me)AVP, 1 × 10−6M) and V2(d(CH2)5[D-Ile2,Ile4,Ala-NH29] AVP, 1 × 10−5M) receptors and of histamine H1(diphenhydramine, 1 × 10−5M) and H2(cimetidine 1 × 10−5M) receptors had no effect on desmopressin-induced relaxation of rat aortic rings. Chlorobutanol, the diluent in which desmopressin is supplied, was devoid of vascular effects. To study the effects of desmopressin on vascular cyclic GMP and cyclic AMP concentrations, a cultured bovine aortic smooth muscle—rat vascular smooth muscle coculture model was employed. Desmopressin (1 × 10−7and 1 × 10−8M) did not significantly alter control values of either cyclic nucleotide. The authors conclude that desmopressin is a potent vasodilator, primarilyviaa direct action on vascular smooth muscle that is modulated by the endothelium and by dilating and constricting prostaglandins and that this vasodilation could account for the hypotension observed with its clinical use.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The steady-state tissue/blood partition coefficients of fentanyl and alfentanil were determined in 13 organs and tissues in the rat. A 6-h infusion of both drugs was used in order to achieve steady-state. Blood and tissue concentrations of drugs were measured by gasliquid chromatography. The partition coefficients of fentanyl were two- to 30-fold higher than those of alfentanil. These data were then used in a physiologic pharmacokinetic model describing the disposition of the two opioids in humans. The model predicted the plasma pharmacokinetics of these drugs in humans reasonably well. However, simulation beyond 24 h after a bolus administration showed a terminal half-life of 20 h for fentanyl,i.e., an elimination phase that has not yet been described in actual pharmacokinetic studies. In keeping with this, the volume of distribution of fentanyl in the model was also larger than expected. The simulated tissue concentration curves of fentanyl and alfentanil in humans could be used to explain the propensity of fentanyl to give secondary peaks in plasma concentration curves and the difference in effect kinetics between the two opioids. Physiologic pharmacokinetic modeling, based on measured data in small animals, can generate information that is not obtainable by empirical methods in humans.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The influence of halothane and isoflurane on α-adrenergic-mediated vasoconstriction before and following calcium channel modulation was investigated in chronically instrumented dogs. After ganglionic, cholinergic, and β-adrenergic blockade, systemic hemodynamic responses following equieffective pressor doses of phenylephrine (0.6 µ g/kg iv), a selective α1agonist, and azepexole [B-HT 933] (20 µ/kg iv), a selective α2agonist, were obtained. The calcium channel stimulator Bay k 8644 (0.5 and 1 µg·kg−1· min−1) was infused intravenously for 10 min and phenylephrine and azepexole administered at the end of each infusion. On different days, each dog was subsequently anesthetized with equihypotensive concentrations of halothane (1.7%) or isoflurane (2%) in oxygen and the same pharmacologic interventions were repeated in the presence of halothane or isoflurane. Twenty-one experiments (three groups) using seven chronically instrumented dogs were completed. Halothane and isoflurane produced significant (P< 0.05) attenuation of the increase in arterial pressure after bolus administration of phenylephrine and azepexole. Bay k 8644 augmented the pressor responses mediated by both phenylephrine and azepexole in all three groups. Thus, halothane and isoflurane nonselectively reduced the pressor response to both α1- and α2-adrenergic receptor stimulation and this was probably not mediated by inhibition of transmembrane calcium flux through dihydropyridine sensitive channels.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The authors examined the cardiovascular and respiratory effects of the highly selective α2-adrenergic agonist dexmedetomidine, both alone and in combination with the synthetic opiate alfentanil. Spontaneously ventilating rats (n = 28) were pretreated with dexmedetomidine, 10 or 30 μg/kg; dexmedetomidine, 30 μg/kg in combination with the central-acting α2-antagonist idazoxan, 10 mg/kg; or vehicle. Fifteen minutes later all rats received alfentanil, 500 μg/kg. Pretreatment with dexmedetomidine reduced heart rate in a dose-related fashion. Administration of alfentanil also caused a significant reduction in heart rate. However, following alfentanil, the dexmedetomidine-treated animals did not have significantly greater bradycardia than control animals. An increase in blood pressure was observed in those animals receiving the larger dose of dexmedetomidine, but this difference disappeared following injection of alfentanil. The addition of idazoxan to the pretreatment regimen prevented the changes seen with dexmedetomidine. Pretreatment with dexmedetomidine produced no significant changes in arterialpH or Pco2. In all groups, administration of alfentanil resulted in a decrease in arterialpH that ultimately became a mixed respiratory and metabolic acidosis. The acidosis promptly resolved following injection of naloxone (1 mg/kg). It appears that dexmedetomidine, at the doses given, has little or no effect on respiration. Dexmedetomidine decreases heart rate but does not add to bradycardia following alfentanil. There is a hypertensive effect seen at the higher dose of dexmedetomidine, but this effect disappears when the drug is given in conjunction with alfentanil. These data show that addition of the α2-agonist dexmedetomidine will not worsen the cardiovascular and respiratory depression associated with high-dose opiates in the spontaneously ventilating rat.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Paroxysmal supraventricular tachycardia (PSVT) is likely due to reentry involving the atrioventricular (AV) node, AV node with AV bypass pathway, sinus node, or atria. Intravenous diltiazem (DIL) or verapamil (VER) might be used to treat PSVT in anesthetized patients, and either drug could be more or less effective or produce adverse circulatory effects in this circumstance because the available inhalation anesthetics are known to elevate plasma concentrations of acutely administered iv DIL or VER. Because human studies were precluded and there are no reliable animal models for most reentrant PSVT, the authors determined the effects of iv DIL or VER and potent inhalation anesthetics (enflurane, halothane, isoflurane) on supraventricular electrophysiologic (EP) properties affecting the likelihood of reentrant PSVT in chronically instrumented dogs. Measurements of supraventricular EP properties in awake dogs without drugs served as control. DIL and VER were then administered iv to achieve clinically relevant plasma concentrations in awake dogs and EP properties were again measured. Finally, anesthetic effects on EP properties in dogs with DIL or VER were tested at end-tidal concentrations equivalent to 1.2 or 1.6 MAC for enflurane, halothane, or isoflurane. In awake dogs, DIL or VER increased AV node conduction time, Wenckebach point and functional refractoriness, and also reduced the range of premature atrial intervals for and likelihood of producing sinus node interpolation or reentry with atrial extrastimulation (P< 0.05, ANOVA). AV node conduction time, Wenckebach point, and functional refractoriness were further increased in anesthetized dogs (all agents) with DIL or VER compared with control (P<0.05, ANOVA). All anesthetics with DIL or VER abolished sinus node interpolation and reentry. Atrial effective and functional refractory periods were not affected by DIL or VER in awake dogs and were increased by any of the anesthetics in dogs with DIL (P< 0.05, ANOVA). Atrial refractory periods were little affected by anesthetics with VER. Adverse circulatory effects, including systolic arterial pressure < 50 mmHg and second-degree (type 1) AV block or sinus arrest with escape rhythms, were most common with VER and any (especially enflurane) of the anesthetics. Finally, anesthetized animals with sinus arrest and escape rhythms (any test condition) could be paced from the atrium at physiologic rates (up to 120 beats/min). The authors conclude that with the potent inhalation anesthetics (iv DIL or VER should be effective against most reentrant PSVT), there is increased risk of adverse circulatory effects with VER compared with DIL, and sinus arrest or sino-atrial block (not complete AV block) is the mechanism for escape rhythms with either DIL or VER and anesthetics.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID