Showing papers in "Anesthesiology in 1996"
TL;DR: The principal conclusions of the task force are that red blood cell transfusions should not be dictated by a single hemoglobin "trigger" but instead should be based on the patient's risks of developing complications of inadequate oxygenation.
Abstract: In 1994, the American Society of Anesthesiologists established the Task Force on Blood Component Therapy to develop evidence‐based indications for transfusing red blood cells, platelets, fresh‐frozen plasma, and cryoprecipitate in perioperative and peripartum settings. The guidelines were developed according to an explicit methodology. The principal conclusions of the task force are that red blood cell transfusions should not be dictated by a single hemoglobin \"trigger\" but instead should be based on the patient's risks of developing complications of inadequate oxygenation. Red blood cell transfusion is rarely indicated when the hemoglobin concentration is greater than 10 g/dL and is almost always indicated when it is less than 6 g/dL. The indications for autologous transfusion may be more liberal than for allogeneic (homologous) transfusion. The risks of bleeding in surgical and obstetric patients are determined by the extent and type of surgery, the ability to control bleeding, the actual and anticipated rate of bleeding, and the consequences of uncontrolled bleeding. Prophylactic platelet transfusion is ineffective when thrombocytopenia is due to increased platelet destruction. Surgical and obstetric patients with microvascular bleeding usually require platelet transfusion if the platelet count is less than 50 x 109 /l and rarely require therapy if it is greater than 100 x 10 sup 9 /l. Fresh‐frozen plasma is indicated for urgent reversal of warfarin therapy, correction of known coagulation factor deficiencies for which specific concentrates are unavailable, and correction of microvascular bleeding when prothrombin and partial thromboplastin times are > 1.5 times normal. It is contraindicated for augmentation of plasma volume or albumin concentration. Cryoprecipitate should be considered for patients with von Willebrand's disease unresponsive to desmopressin, bleeding patients with von Willebrand's disease, and bleeding patients with fibrinogen levels below 80–100 mg/dL. The task force recommends careful adherence to proper indications for blood component therapy to reduce the risks of transfusion.
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TL;DR: In this paper, an appropriate measure of performance is needed to identify anesthetic depth indicators that are promising for use in clinical monitoring, and the measure must take into account both desired indicator performance and the nature of available performance data.
Abstract: BackgroundAn appropriate measure of performance is needed to identify anesthetic depth indicators that are promising for use in clinical monitoring. To avoid misleading results, the measure must take into account both desired indicator performance and the nature of available performance data. Ideall
447 citations
TL;DR: Early Extubation reduces CVICU and hospital length of stay but does not increase the rate or costs of complications when compared with patients in the late extubation group, and shifts the highCVICU costs to the lower ward costs.
Abstract: BackgroundEconomics has caused the trend of early tracheal extubation after cardiac surgery, yet no prospective randomized study has directly validated that early tracheal extubation anesthetic management decreases costs when compared with late extubation after cardiac surgery.MethodsThis prospectiv
410 citations
TL;DR: Compared to alfentanil, the high clearance of remifentanin, combined with its small steady-state distribution volume, results in a rapid decline in blood concentration after termination of an infusion, and the drugs are pharmacodynamically similar.
Abstract: BackgroundRemifentanil is an esterase-metabolized opioid with a rapid clearance. The aim of this study was to contrast the pharmacokinetics and pharmacodynamics of remifentanil and alfentanil in healthy, adult male volunteers.MethodsTen volunteers received infusions of remifentanil and alfentanil on
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349 citations
TL;DR: Part of the mechanism by which dexmedetomidine produces an antinociceptive effect is by an action directly on the LC, demonstrated by these studies in which ant inociception produced by injection of this drug into the LC can be blocked by specific alpha2 antagonists injected into theLC.
Abstract: Background Alpha(2)-Adrenergic agonists such as clonidine and dexmedetomidine are known to produce sedation and analgesia in humans. The sedative effect of these agents is thought to occur through supraspinal pathways, involving the locus ceruleus (LC) and its projections in rats. While the antinociceptive response to alpha(2) agonists, given intrathecally, is mediated predominantly in the spinal cord, other sites of action have not been systematically studied. The authors examined whether alpha(2)-adrenergic receptors in the LC mediate an antinociceptive effect. Methods For administration of different drugs into the LC, guide cannulas were placed with their tips in the LC in male Sprague-Dawley rats. Dexmedetomidine (3.5 micrograms/0.2 microliter) was microinjected into the LC through the cannula, or given systemically by intraperitoneal injecton (50 micrograms/kg). The antinociceptive effect of dexmedetomidine was measured using the tail-flick latency response. To determine the sites through which dexmedetomidine injection into the LC produces antinociception, the authors examined whether this response could be perturbed by the specific alpha(2)-adrenergic antagonists atipamezole and L659,066 and pertussis toxin administered either into the LC or intrathecally before injection of dexmedetomidine systemically or directly into the LC. To eliminate the possibility that drug administered in one site (LC or intrathecal) could reach the other site, the dispositional characteristics of radiolabeled dexmedetomidine (LC) or atipamezole (intrathecal) were studied. Results Dexmedetomidine placed into the LC produces a dose-dependent increase in the tail-flick latency. This antinociceptive effect was blocked by pertussis toxin and by the alpha(2) antagonists atipamezole and L659,066 placed in the LC. Intrathecal administration of atipamezole and pertussis toxin also blocked the antinociceptive effect of dexmedetomidine placed in the LC. (3)H-dexmedetomidine introduced into the LC did not reach the spinal cord in pharmacologically active concentrations; also, intrathecally administered (3)H-atipamezole did not reach the LC in appreciable amounts. The systemic administration of dexmedetomidine produced an increase in tail-flick latency, and this effect was attenuated by the injection of atipamezole and L659,066 into the LC. Conclusions Part of the mechanism by which dexmedetomidine produces an antinociceptive effect is by an action directly on the LC, demonstrated by these studies in which antinociception produced by injection of this drug into the LC can be blocked by specific alpha(2) antagonists injected into the LC. Furthermore, the action of dexmedetomidine in the LC in turn may result in an increase in activation of alpha(2) adrenoceptors in the spinal cord, because the antinociceptive effect of LC dexmedetomidine injection also can be blocked by intrathecal injection of antipamezole and pertussis toxin.
320 citations
TL;DR: The choice of anesthesia, when delivered as described, does not significantly influence cardiac morbidity and overall mortality in patients undergoing peripheral vascular surgery.
Abstract: Background : Despite evidence that regional anesthesia may be associated with fewer perioperative complications than general anesthesia, most studies that have compared cardiac outcome after general or regional anesthesia alone have not shown major differences. This study examines the impact of anesthetic choice on cardiac outcome in patients undergoing peripheral vascular surgery who have a high likelihood of associated coronary artery disease. Methods : Four hundred twenty-three patients, between 1988 and 1991, were randomly assigned to receive general (n = 138), epidural (n = 149), or spinal anesthesia (n = 136) for femoral to distal artery bypass surgery. All patients were monitored with radial artery and pulmonary artery catheters. Postoperatively, patients were in a monitored setting for 48-72 h and had daily electrocardiograms for 4-5 days and creatine phosphokinase/isoenzymes every 8 h X 3, then daily for 4 days. Cardiac outcomes recorded were myocardial infarction, angina, and congestive heart failure. Results : Baseline clinical characteristics were not different between anesthetic groups. Overall, the patient population included 86% who were diabetic, 69% with hypertension, 36% with a history of a prior myocardial infarction, and 41% with a history of smoking. Cardiovascular morbidity and overall mortality were not significantly different between groups when analyzed by either intention to treat or type of anesthesia received. In the intention to treat analysis, incidences of cardiac event or death for general, spinal, and epidural groups were 16.7%, 21.3%, and 15.4%, respectively. The absolute risk difference observed between general and all regional anesthesia groups for cardiac event or death was -1.6% (95% confidence interval -9.2%, 6.1%) This reflected a nonsignificant trend for lower risk of postoperative events with general anesthesia. Conclusions : The choice of anesthesia, when delivered as described, does not significantly influence cardiac morbidity and overall mortality in patients undergoing peripheral vascular surgery.
299 citations
TL;DR: A prospective study was designed to evaluate the accuracy of various EEG parameters for assessing midazolam-induced sedation during regional anesthesia.
Abstract: BackgroundThe electroencephalogram (EEG) has been used to study the effects of anesthetic and analgesic drugs on central nervous system function. A prospective study was designed to evaluate the accuracy of various EEG parameters for assessing midazolam-induced sedation during regional anesthesia.Me
283 citations
TL;DR: An assessment was made of the effect of the physiologic N-methyl-D-aspartate antagonist magnesium on analgesic requirements, pain, comfort, and quality of sleep in the postoperative period.
Abstract: BackgroundN-methyl-D-aspartate antagonists may play a role in the prevention of pain. An assessment was made of the effect of the physiologic N-methyl-D-aspartate antagonist magnesium on analgesic requirements, pain, comfort, and quality of sleep in the postoperative period.MethodsIn a randomized, d
TL;DR: Clinically, the induction, recovery, and safety characteristics of sevoflurane and halothane are similar and are a suitable alternative to Halothane for use in children undergoing minor ambulatory surgery.
Abstract: BackgroundSevoflurane is an inhalational anesthetic with characteristics suited for use in children. To determine whether the induction, recovery, and safety characteristics of sevoflurane differ from those of halothane, the following open-labeled, multicenter, randomized, controlled, phase III stud
TL;DR: The incidence of TRI is greater with lidocaine than bupivacaine, decreasing the lidocane concentration to 2% does not prevent TRI, and surgical position may be an important contributing factor.
Abstract: Background : There is considerable controversy regarding the role of subarachnoid 5% hyperbaric lidocaine in the syndrome transient radicular irritation (TRI). This randomized, double-blinded, prospective study was designed to determine the incidence of TRI and identify factors possibly contributing to its development. Methods : One hundred fifty-nine ASA physical status 1 or 2 patients undergoing outpatient knee arthroscopy or unilateral inguinal hernia repair were prospectively randomized to receive spinal anesthesia with 5% hyperbaric lidocaine with epinephrine (60 mg with 0.2 mg epinephrine for arthroscopy or 75 mg with 0.2 mg epinephrine for hernia repair), 2% isobaric lidocaine without epinephrine (60 mg for arthroscopy or 75 mg for hernia repair), or 0.75% hyperbaric bupivacaine without epinephrine (7.5 mg for arthroscopy or 9.0 mg for hernia repair) in a double-blinded fashion. On the 3rd postoperative day, patients were contacted by a blinded investigator and questioned regarding the incidence of postoperative complications including TRI, defined as back pain with radiation down one or both buttocks or legs occurring within 24 h after surgery. Postoperatively, time from injection to block resolution, ambulation, voiding, and ready for discharge were recorded by a postanesthesia care unit nurse blinded to the group assignment. Results : The incidence of TRI was greater in patients receiving lidocaine than in those receiving bupivacaine (16% vs. 0% ; P = 0.003). There was no difference in the incidence of TRI between the patients receiving 5% hyperbaric lidocaine with epinephrine and those receiving 2% isobaric lidocaine without epinephrine (16% vs. 16% ; P = 0.98). The incidence of TRI was greater in patients undergoing arthroscopy than in those undergoing hernia repair (13% vs. 5% ; P = 0.04). There was no difference in discharge times in patients receiving bupivacaine versus those receiving hyperbaric lidocaine with epinephrine (292 vs. 322 min ; P = 0.61). Conclusions : The incidence of TRI is greater with lidocaine than bupivacaine, decreasing the lidocaine concentration to 2% does not prevent TRI, and surgical position may be an important contributing factor. Discharge times at our institution are not different when equipotent doses of 0.75% hyperbaric bupivacaine or 5% hyperbaric lidocaine with 0.2 mg epinephrine are used in ambulatory patients undergoing spinal anesthesia.
TL;DR: It is suggested that hemofiltration exerts some beneficial clinical effects that are not due to water removal and the role of the early removal of factors triggering the inflammatory response, rather than a direct removal of cytokines, deserves further investigation.
Abstract: BackgroundIn previous studies, researchers suggested a beneficial role of hemofiltration performed during cardiopulmonary bypass in children. This study was performed to assess both clinical effects and inflammatory mediator removal by high-volume, zero-fluid balance ultrafiltration during rewarming
TL;DR: Children who were older than 4 yr or those with a parent with a low trait anxiety or who had a low baseline level of activity/temperament benefited from parental presence during induction of anesthesia.
Abstract: BackgroundTo determine whether parental presence during induction of anesthesia is an effective preoperative behavioral intervention, a randomized controlled trial with children undergoing outpatient surgery was conducted.MethodsEighty-four children were randomly assigned to a parent-present or pare
TL;DR: Eye injuries are more common in patients who are older or who undergo lengthier procedures, and until the mechanisms producing perioperative eye injuries are better understood, it is difficult to identify strategies to prevent this type of injury.
Abstract: BackgroundEye injuries after anesthesia, although infrequent, may result in visual impairment. Previous studies have not defined the risk factors associated with these injuries. To study the cause of these injuries and to determine incidence data, the authors reviewed the records from a 4.5-y period
TL;DR: The decreased CSF volume that results from increased abdominal pressure, such as with obesity or pregnancy, may produce more extensive neuraxial blockade through diminished dilution of anesthetic.
Abstract: Background Although the cerebrospinal fluid (CSF) is the pathway of anesthetic delivery and the diluent for neuraxially administered drugs, little is known about its volume, including variability among individuals, longitudinal distribution, or influence of body habitus. Models made to investigate subarachnoid anesthetic distribution lack valid dimensions. CSF volume was measured in volunteers, and the effect of obesity and abdominal compression on CSF volume was evaluated using magnetic resonance imaging. Methods Low thoracic and lumbosacral axial magnetic resonance images of 25 healthy volunteers were obtained at 8-mm intervals by fast spin-echo sequence, which highlights CSF. A repeat image series was performed in 15 subjects during external abdominal compression. In two subjects, images were obtained without compression for the entire vertebral column. Dural sac and spinal cord areas were determined in a blinded fashion for each image using video/digital analysis. Area of the sac minus area of the cord constituted area of CSF and roots ("CSF/root"); this area multiplied by 8 mm resulted in CSF/root volume per section. Results There is great interindividual variability in CSF/root volume. From the T11-T12 disc to the sacral terminus of the dural sac, the mean volume for all subjects is 49.9 +/- 12.1 ml (mean +/- SD; range 28.0-81.1 ml). This volume was significantly less in relatively obese subjects (42.9 +/- 9.5 ml) than in nonobese subjects (53.5 +/- 12.9 ml). Abdominal compression decreased CSF/root volume by 3.6 +/- 3.2 ml. Sections through intervertebral foramina showed the biggest decrease with abdominal compression, with a lesser change in sections with veins and no change in the absence of these anatomic features. Total vertebral CSF/root volume in two subjects was 94.84 and 120.01 ml, respectively. Conclusions CSF volume is widely variable between individuals. The decreased CSF volume that results from increased abdominal pressure, such as with obesity or pregnancy, may produce more extensive neuraxial blockade through diminished dilution of anesthetic. The mechanism by which increased abdominal pressure decreases CSF volume is probably inward movement of soft tissue in the intervertebral foramen, which displaces CSF.
TL;DR: Although remifentanil was given at extremely high concentrations in the absence of isoflurane, it did not provide adequate anesthesia and its MAC reduction is similar to that produced by other opioids.
Abstract: Background Remifentanil is a new micro-specific opioid receptor agonist currently under investigation. The interaction between opioids and volatile anesthetics is complex. Defining this interaction provides a basis for more rational dosing schemes when such combinations are used for anesthesia and allows the anesthetic potency of remifentanil relative to other opioids to be determined. Methods Two centers enrolled a total of 220 patients. Patients were randomized to receive a target concentration of remifentanil via a computer-assisted continuous infusion device of either 0.0, 0.5, 1.0, 1.5, 2.0, 4.0, 8.0, 16.0, and 32.0 ng/ml initiated before the administration of isoflurane. Patients were also stratified by age groups 18–30, 31–55, and 56–65 yr. After induction of anesthesia with isoflurane the initial patient in each dose group was assigned an age-adjusted isoflurane concentration. The isoflurane concentration for each subsequent patient was adjusted according to the up/down technique until a minimum of 12 patients were enrolled in each group. Arterial blood samples for remifentanil whole blood concentrations were obtained. The patient was observed for purposeful movement for up to 1 min after skin incision. The minimum alveolar concentration (MAC) of isoflurane (0 ng/ml remifentanil group) and MAC reduction of isoflurane by remifentanil were determined. Results The MAC of isoflurane alone was 1.3%. Remifentanil caused an exponential reduction in the MAC of isoflurane with 1.37 ng/ml remifentanil resulting in a 50% MAC reduction, 4 ng/ml remifentanil a 77% reduction and 32 ng/ml a 91% reduction of isoflurane MAC. Conclusion The MAC reduction of isoflurane by remifentanil is similar to that produced by other opioids. Although remifentanil was given at extremely high concentrations in the absence of isoflurane, it did not provide adequate anesthesia. A 50% isoflurane MAC reduction is produced by 1.37 ng/ml remifentanil whole blood concentration compared to previously published plasma concentrations of fentanyl of 1.67 ng/ml or sufentanil of 0.14 ng/ml.
TL;DR: This is the first study demonstrating a concentration-dependent negative inotropic effect of intravenous anesthetics in isolated human atrial muscle and no inhibition of myocardial contractility was found in the clinical concentration ranges of propofol, midazolam, and etomidate.
Abstract: Background: Cardiovascular instability after intravenous induction of anesthesia may be explained partly by direct negative inotropic effects. The direct inotropic influence of etomidate, ketamine, midazolam, propofol, and thiopental on the contractility of isolated human atrial tissue was determined. Effective concentrations were compared with those reported clinically. Methods: Atrial tissue was obtained from 16 patients undergoing coronary bypass surgery. Each fragment was divided into three strips, and one anesthetic was tested per strip in increasing concentrations (10(-6) to 10(-2) M). Strips were stimulated at 0.5 Hz, and maximum isometric force was measured. Induction agents were studied in two groups, group 1 (n = 7) containing thiopental midazolam, and propofol, and group 2 (n = 9) consisting of etomidate, ketamine, and propofol. Results: The tested anesthetics caused a concentration-dependent depression of contractility resulting in complete cessation of contractions at the highest concentrations. The IC(50)s (mean +/- SEMI mu M) for inhibition of the contractility were: thiopental 43 +/- 7.6, propofol 235 +/- 48 (group 1), and 246 +/- 42 (group 2), midazolam 145 +/- 54, etomidate 133 +/- 13, and ketamine 303 +/- 54. Conclusions: This is the first study demonstrating a concentration-dependent negative inotropic effect of intravenous anesthetics in isolated human atrial muscle. No inhibition of myocardial contractility was found in the clinical concentration ranges of propofol, midazolam, and etomidate. In contrast, thiopental showed strong and ketamine showed slight negative inotropic properties. Thus, negative inotropic effects may explain in part the cardiovascular depression on induction of anesthesia with thiopental but not with propofol midazolam, and etomidate. Improvement of hemodynamics after induction of anesthesia with ketamine cannot be explained by intrinsic cardiac stimulation.
TL;DR: The results indicate that intraperitoneal local anesthetic blockade administered before or after surgery preempts postoperative pain relative to an untreated placebo-control condition.
Abstract: BackgroundA controversy exists over the effectiveness and clinical value of preemptive analgesia. Additional studies are needed to define the optimum intensity, duration, and timing of analgesia relative to incision and surgery.MethodsOne hundred twenty patients undergoing laparoscopic cholecystecto
TL;DR: Omission of nitrous oxide reduced the odds of postoperative nausea and vomiting by 37%, a reduction in risk of 28%, in patients undergoing abdominal surgery and general surgical procedures.
Abstract: Background: Postoperative nausea and vomiting are important causes of morbidity after general anesthesia. Nitrous oxide has been implicated as an emetogenic agent in many studies. However, several other trials have failed to sustain this claim. The authors tried to resolve this issue through a meta-analysis of randomized controlled trials comparing the incidence of postoperative nausea and vomiting after anesthesia with or without nitrous oxide.Methods: Of 37 published studies retrieved by a search of articles indexed on the MEDLINE database from 1966 to 1994, 24 studies (26 trials) with distinct nitrous-oxide and non-nitrous oxide groups were eligible for the meta-analysis. The pooled odds ratio and relative risk were calculated. Post hoc subgroup analysis was also performed to qualify the result.Results: The pooled odds ratio was 0.63 (0.53 to 0.75). Omission of nitrous oxide reduced the risk for postoperative nausea and vomiting by 28% (18% to 37%). In the subgroup analysis, the maximal effect of omission of nitrous oxide was seen in female patients. In patients undergoing abdominal surgery and general surgical procedures, the effect of omission of nitrous oxide, although in the same direction, was not significant.Conclusion: Omission of nitrous oxide reduced the odds of postoperative nausea and vomiting by 37%, a reduction in risk of 28%.
TL;DR: High-dose tranexamic acid significantly reduces intraoperative blood loss and perioperative donor exposure in patients with end-stage parenchymal liver disease who are undergoing orthotopic liver transplantation, with marked reductions in platelet and cryoprecipitate requirements.
Abstract: Background : Patients with end-stage liver disease frequently incur large-volume blood loss during liver transplantation associated with mechanical factors, preexisting coagulopathy, and intraoperative fibrinolysis. Methods : Between April 1992 and May 1994, the authors of this double-blind, randomized, placebo-controlled study examined the effect of high-dose tranexamic acid (maximum of 20 g) on blood loss and blood product requirements in patients undergoing primary isolated orthotopic liver transplantation. Primary outcome measures were volume of blood loss (intraoperative blood loss and postoperative drainage) and erythrocyte, plasma, platelet, and cryoprecipitate use during surgery and the first 24 h of intensive care unit stay. Results : Patients receiving transexamic acid (n = 25) had less intraoperative blood loss (median, 4.3 1 ; interquartile range, 2.5 to 7.9 ; P = 0.006) compared with the placebo group (n = 20 ; median, 81 ; interquartile range, 5 to 15.8), and reduced intraoperative plasma, platelet, and cryoprecipitate requirements. Median perioperative erythrocyte use was 9 units (interquantile range, 4 to 14 units) in patients receiving transexamic acid and 13 units (interquantile range, 7.5 to 31 units) in controls (P = 0.03). Total perioperative donor exposure was 20.5 units (interquantile range, 16 to 41 units) in patients receiving transexamic acid and 43.5 units (interquantile range, 29.5 to 79 units) in controls (P = 0.003). Results for postoperative wound drainage were similar. Hospital stay and need for retransplantation were comparable in both groups. No patient in either group showed clinical evidence of hepatic artery or portal venous thrombosis within 1 month of transplantation. Conclusions : High-dose tranexamic acid significantly reduces intraoperative blood loss and perioperative donor exposure in patients with end-stage parenchymal liver disease who are undergoing orthotopic liver transplantation, with marked reductions in platelet and cryoprecipitate requirements.
TL;DR: The authors' purpose in this study was to examine, using ultrasound, the anatomic relation of the IJV and CA as viewed from the perspective of a cannulating needle, and found that patients older than 60 yr were more likely to have this anatomy than patients younger than60 yr.
Abstract: BackgroundCannulation of the internal jugular vein (IJV) is associated with a 95% success rate when external landmarks are used. Anatomic variability has been implicated as the cause for difficulty in cannulation without ultrasound. In contrast to an IJV located lateral to the carotid artery (CA), a
TL;DR: The results confirm earlier findings that clinically relevant concentrations of volatile anesthetics depress glutamate‐mediated synaptic transmission and support recent findings from biochemical and electrophysiologic studies indicating presynaptic sites of action contribute to anesthetic‐induced depression of excitatory transmission.
Abstract: Background Recent evidence for a presynaptic depression of glutamate release produced by volatile anesthetics prompted the current study of isoflurane and halothane effects on glutamate-mediated transmission in the mammalian central nervous system. Methods Electrophysiologic recordings from CA1 neurons in rat hippocampal brain slices were used to measure anesthetic effects on glutamate-mediated excitatory postsynaptic potential (EPSP) amplitudes and paired pulse facilitation. Paired pulse facilitation is known to be altered when the calcium-dependent release of glutamate is depressed, but not when EPSP amplitudes are depressed by postsynaptic mechanisms. Results Isoflurane depressed EPSP amplitudes over a concentration range of 0.35-2.8 vol %, with a 50% depression (EC50) occurring at 1.0 vol % (0.71 rat minimum alveolar concentration). This depression was accompanied by an increase in paired-pulse facilitation of approximately 30% at 1.7 vol %, using interpulse intervals of 120 ms. Halothane depressed EPSP amplitudes in a concentration-dependent manner (0.3-2.4 vol %, EC50 = 1.1 minimum alveolar concentration; 1.3 vol %) and also increased facilitation by approximately 20% at 1.2 vol %. These effects persisted in the presence of 10 microM bicuculline, indicating that enhanced gamma-aminobutyric acid-mediated inhibition was not involved. The anesthetic-induced increase in facilitation and EPSP depression was mimicked by lowering extracellular calcium, which is known to depress glutamate release at these synapses. The postsynaptic glutamate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione depressed EPSP amplitudes with no change in facilitation. Conclusions Our results confirm earlier findings that clinically relevant concentrations of volatile anesthetics depress glutamate-mediated synaptic transmission. The observed increases in synaptic facilitation support recent findings from biochemical and electrophysiologic studies indicating presynaptic sites of action contribute to anesthetic-induced depression of excitatory transmission. This anesthetic-induced reduction in glutamate release would contribute to the central nervous system depression associated with anesthesia by adding to postsynaptic depressant actions on glutamate receptors.
TL;DR: The aqueous‐phase (but not the gas‐phase) minimum alveolar concentration calculated at normal body temperature is, to a first approximation, the appropriate choice for a clinically relevant anesthetic concentration.
Abstract: BackgroundWhen performing experiments at room temperature with volatile general anesthetics and in vitro mammalian preparations (such as isolated neurons), the question arises as to which concentrations of anesthetics are "clinically relevant." Different choices can lead to different interpretations
TL;DR: The frequency of perioperative bronchospasm and laryngospasm was surprisingly low in this cohort of persons with asthma, and these complications did not lead to severe respiratory outcomes in most patients.
Abstract: BackgroundPatients with asthma are thought to be at high risk for pulmonary complications to develop during the perioperative period, and these complications may lead to serious morbidity. Existing medical records were reviewed to determine the frequency of and risk factors for perioperative pulmona
TL;DR: Prolonged percutaneous blockade of peripheral nerves is feasible, the recovery from blockade is complete, and plasma bupivacaine levels are far below the range associated with systemic toxicity.
Abstract: BackgroundBiodegradable microspheres are a useful method of drug delivery because they are both injectable and biodegradable, eliminating the need for surgical implantation or removal. Previous work has characterized implantable preparations of local anesthetics in polymer pellets for prolonged regi
TL;DR: The results indicate that isoflurane prevents decreased systolic shortening caused by multiple episodes of ischemia and reperfusion and result in improved recovery of contractile function of postischemic, reperfused myocardium and are mediated by isofLurane‐induced activation of KATP channels.
Abstract: Background The mechanism of the protective actions of volatile anesthetics in ischemic myocardium has not been clearly elucidated. The role of myocardial adenosine triphosphate-regulated potassium (KATP) channels in isoflurane-induced enhancement of recovery of regional contractile function after multiple brief occlusions and reperfusion of the left anterior descending coronary artery (LAD) was studied in dogs anesthetized with barbiturates. Methods Dogs (n = 32) were instrumented to measure left ventricular and aortic blood pressure, cardiac output, LAD coronary blood flow velocity, and subendocardial segment length. Regional myocardial perfusion was measured using radioactive microspheres. Hemodynamics and percentage segment shortening (%SS) in the LAD perfusion territory were evaluated after instrumentation was complete; after pretreatment with the KATP channel antagonist, glyburide (0.05 mg/kg sup -1) or drug vehicle (polyethylene glycol in ethyl alcohol; control experiments); and in the presence or absence of 1 MAC isoflurane administered for 30 min before and during five 5-min occlusions and reperfusion of the LAD in four experimental groups. Isoflurane was discontinued at the onset of the final reperfusion period. Measurements of hemodynamics, %SS, and myocardial perfusion were repeated at several intervals during 180 min after reperfusion of the LAD. Results Left anterior descending coronary artery occlusion caused regional dyskinesia during each 5-min occlusion in each dog. Control and glyburide-pretreated dogs demonstrated poor recovery of %SS by 180 min after reperfusion (2 +/- 10 and 7 +/- 6% of baseline, respectively). In contrast, dogs anesthetized with isoflurane exhibited complete recovery of function (%SS) by 180 min after reperfusion (82 +/- 8% of baseline). Enhanced recovery of regional contractile function by isoflurane was abolished by pretreatment with glyburide 180 min after reperfusion (16 +/- 10% of baseline). Improvement of functional recovery of stunned myocardium by isoflurane, and the blockade of this action by glyburide, was not associated with changes in hemodynamics or regional myocardial perfusion. Conclusions The results indicate that isoflurane prevents decreased systolic shortening caused by multiple episodes of ischemia and reperfusion. These actions result in improved recovery of contractile function of postischemic, reperfused myocardium and are mediated by isoflurane-induced activation of KATP channels.