bluuebunny/crossref_metadata_2025 huggingface dataset:
Prolonged Intercostal Nerve Blockade in Sheep Using Controlled-release of Bupivacaine and Dexamethasone from Polymer Microspheres
Authors: Drager Christiane , Benziger David , Gao Feng , Berde Charles B.
Published: November 2003

Background

Previous work from the authors' group characterized a prolonged percutaneous blockade of the sciatic nerve in rats using bupivacaine-dexamethasone microspheres. The goals of the current study are to examine the (1) efficacy of bupivacaine microspheres with and without dexamethasone for intercostal blockade in sheep; (2) scaling of dose and duration with a 100-fold increase in body size from rats to sheep; (3) local toxicity and adverse systemic reactions to bupivacaine microspheres with and without dexamethasone.

Methods

Intercostal blocks were performed percutaneously in sedated sheep. Sensory blockade was measured at repeated time points by absent flinch response to skin pinch. Plasma bupivacaine concentrations were measured using high performance liquid chromatography. Chest wall specimens were examined by light microscopy.

Results

The duration of intercostal blockade increased with bupivacaine dose for animals receiving from 8 to 80 mg/kg of microspheres with and without dexamethasone. At each dose, microspheres containing dexamethasone had a longer duration of block than microspheres without dexamethasone. From 8 to 80 mg/kg, the mean duration of block with bupivacaine-dexamethasone microspheres increased from 4 to 13 days. Plasma concentrations of bupivacaine remained 10-fold below the convulsive EC50 concentration for sheep. Chest wall histology showed a significant granulomatous reaction around bupivacaine microspheres but not around bupivacaine-dexamethasone microspheres.

Conclusions

A single administration of bupivacaine-dexamethasone microspheres produces an effective chest wall analgesia of several days' duration. This may prove useful clinically for thoracic surgery or trauma.
Comparative Clinical Pharmacology of Rocuronium, Cisatracurium, and Their Combination
Authors: Naguib Mohamed , Samarkandi Abdulhamid H. , Ammar Adel , Elfaqih S. R. , Al-Zahrani Salem , Turkistani Ahmed
Published: November 2003

Background

The comparative clinical pharmacology of cisatracurium and rocuronium and their combinations has not been reported. In this study, the authors compared the relative potency and the clinical profile and characterized the interaction of both drugs.

Methods

Two hundred twenty adults classified as American Society of Anesthesiologists physical status I and anesthetized with propofol-fentanyl-nitrous oxide were studied. In part 1, the neuromuscular-blocking effects of cisatracurium and rocuronium were assessed after administration of bolus doses of 20-50 microg/kg and 100-300 microg/kg, respectively. In part 2, we compared the time course of 1xED50, 1, 1.5, and 2xED95 doses of both drugs (where ED50 and ED95 are, respectively, the doses producing 50% and 95% depression of the first twitch height [T1]). In part 3, equieffective combinations of both drugs were studied to characterize their interaction.

Results

The calculated ED50 values and their 95% confidence intervals were 111 (107-115) and 26.2 (25.8-26.5) microg/kg [corrected] for rocuronium and cisatracurium, respectively. Compared with equipotent doses of cisatracurium, rocuronium had a faster onset, and a faster spontaneous T1 and train-of-four recovery times that were significant except at maximum recovery with the 2xED95 dose. The interaction between rocuronium and cisatracurium was synergistic, and the time profile of the combination group was different from that of the single-dose groups.

Conclusions

Cisatracurium is four to five times more potent than rocuronium. Rocuronium had a faster onset of action, a shorter clinical duration, and a faster spontaneous recovery rate compared with equipotent doses of cisatracurium.
Cardiovascular Effects of Xenon in Isoflurane-anesthetized Dogs with Dilated Cardiomyopathy
Authors: Hettrick Douglas A. , Pagel Paul S. , Kersten Judy R. , Tessmer John P. , Bosnjak Zeljko J. , Georgieff Michael , Warltier David C.
Published: November 2003

Background

Clinical interest in xenon has been rekindled recently by new recycling systems that have decreased its relative cost. The cardiovascular effects of xenon were examined in isoflurane-anesthetized dogs before and after the development of rapid left ventricular (LV) pacing-induced cardiomyopathy.

Methods

Dogs (n = 10) were chronically instrumented to measure aortic and LV pressure, LV subendocardial segment length, and aortic blood flow. Hemodynamics were recorded, and indices of LV systolic and diastolic function and afterload were determined in the conscious state and during 1.5 minimum alveolar concentration isoflurane anesthesia alone and combined with 0.25, 0.42, and 0.55 minimum alveolar concentration xenon in dogs with and without cardiomyopathy.

Results

Administration of xenon to healthy dogs anesthetized with isoflurane decreased heart rate and increased the time constant (tau) of isovolumic relaxation but did not alter arterial and LV pressures, preload recruitable stroke work slope, and indices of LV afterload. Chronic rapid LV pacing increased the baseline heart rate and LV end-diastolic pressure, decreased arterial and LV systolic pressures, and produced LV systolic and diastolic dysfunction. Administration of xenon to isoflurane-anesthetized, cardiomyopathic dogs did not alter heart rate, arterial and LV pressures, myocardial contractility, and indices of early LV filling and regional chamber stiffness. More pronounced increases in tau were accompanied by increases in total arterial resistance during administration of xenon to isoflurane-anesthetized cardiomyopathic compared with healthy dogs.

Conclusions

The results indicate that xenon produces minimal cardiovascular actions in the presence of isoflurane in dogs with and without experimental dilated cardiomyopathy.
Circulating Blood Volume Measured by Pulse Dye-Densitometry
Authors: Iijima Takehiko , Iwao Yasuhide , Sankawa Hiroshi
Published: November 2003

Background

Pulse dye-densitometry (PDD) is a newly developed technique for monitoring the arterial concentration of indocyanine green. Using this method, circulating blood volume (CBV) can be calculated without using radioisotopes. In this study, the CBV value obtained by PDD was validated by comparison using the human serum albumin ((131)I-HSA) dilution method.

Methods

Eleven healthy volunteers underwent placement of cannulae into the radial artery and antecubital vein for withdrawal of blood samples and injection of indicator. Probes for PDD were attached to the right nostril and the right index finger. Indocyanine green (20 mg), dissolved in 4 ml water, and 25 microCi (131)I-HSA in 1 ml distilled water were injected simultaneously into the left antecubital vein. Blood samples were withdrawn 3, 6, 10, 20, 30, and 45 min after injection, then processed for spectrophotometric measurement of indocyanine green and scintillation counting.

Results

The blood dye concentration correlated well with the values obtained by PDD (r=0.986, imprecision 0.04+/-0.11 mg/l, 10.0+/-31%. The imprecision of the CBV value obtained by PDD (nose probe) and by the (131)I-HSA dilution method was 3.99+/-10.54%, 0.259+/-0.593 l. The imprecision of the CBV obtained by in vitro spectrophotometry compared with PDD was 2.47+/-9.00%, 0.100+/-0.446 l.

Conclusions

This newly developed, less invasive method can measure CBV with an imprecision of 3.99+/-10.54%, 0.259+/-0.593 l (nose probe), and thus is also as accurate as the conventional radioisotope method.
The Local Addition of Tenoxicam Reduces the Incidence of Low Back Pain after Lumbar Epidural Anesthesia
Authors: Wang Yung-Liang , Hsieh Jing-Ru , Chung Ham-See , Yu Chi-Lun , Ho Angie C. Y. , Lu Pao-Ping , Tan Peter P. C.
Published: November 2003

Background

Postepidural backache is a common postoperative complaint after lumbar epidural anesthesia. Useful interventions to decrease the incidence of postepidural backache would be helpful.

Methods

We performed a prospective, randomized, double-blind study to compare the effect of local addition of tenoxicam on the incidence of postepidural backache after nonobstetric surgery. One thousand unpremedicated ASA physical status I or II patients scheduled for hemorrhoidectomy were assigned randomly to tenoxicam or control groups. Patients in the control group received 25 ml lidocaine, 2%, with epinephrine 1:200,000 epidurally and 4 ml lidocaine, 1%, for local skin infiltration. Patients in the tenoxicam group received 25 ml lidocaine, 2%, with epinephrine 1:200,000 epidurally and 4 ml lidocaine, 1%, with tenoxicam (2 mg) 1:2,000 for local skin infiltration. Patients were interviewed at 24, 48, and 72 h postoperatively using a standard visual analog scale for evaluation of postepidural backache. A patient was considered to have postepidural backache when the postoperative visual analog scale score was higher than the preoperative score.

Results

The incidence of postepidural backache in patients in the control group for the 3 days were 22.8%, 17.4%, and 9.2%, all of which were significantly more frequent than observed in the patients in the tenoxicam group (6.8%, 4.0%, and 1.2%, P < 0.01). There was a significant association between backache and multiple attempts at epidural needle insertion.

Conclusion

In summary, the local addition of tenoxicam reduced the incidence and severity of postepidural backache.
Interaction of Intrathecally Infused Morphine and Lidocaine in Rats (Part II)
Authors: Saito Yoji , Kaneko Megumi , Kirihara Yumiko , Sakura Shinichi , Kosaka Yoshihiro
Published: November 2003

Background

There has been little information regarding the effects of local anesthetics on tolerance to opioids, although chronic use of combination of opioids and local anesthetics is popular for pain control. This study was designed to examine the effects of lidocaine on morphine tolerance to somatic and visceral antinociception.

Methods

Rats received a continuous intrathecal infusion of morphine (0.3-10 microg x kg(-1) x h(-1)), lidocaine (30-1000 microg x kg(-1). h(-1)), a combination of those, or saline. After 6- day infusion, intrathecal morphine challenge test (5 microg/10 microl) was performed, and time-response curve was constructed to assess the magnitude of tolerance. The tail flick (TF) test and colorectal distension (CD) test were used to measure somatic and visceral antinociceptive effects, respectively.

Results

Antinociceptive effects in the TF and CD tests caused by morphine challenge were reduced (P < 0.01) in the morphine infused groups. The magnitude of the tolerance was inversely associated with the amount of morphine infused. Lidocaine infusion induced no different change in the morphine challenge test from that seen in the saline infusion group. Development of tolerance was greater in morphine 3 microg x kg(-1) h(-1) than in morphine 0.75 microg x kg(-1) x h(-1) + lidocaine 150 microg x kg(-1) x h(-1) despite their similar antinociceptive effects during intrathecal infusion. The infusion of a low dose of morphine (0.3 microg kg(-1) x h(-1)) did not reduce the antinociceptive effects in the challenge test.

Conclusion

Lidocaine in combination with morphine does not reduce tolerance to morphine nor develop cross-tolerance. The intrathecal infusion of morphine induced tolerance to somatic and visceral antinociception in a dose-dependent fashion.
Local Cerebral Blood Flow, Local Cerebral Glucose Utilization, and Flow-Metabolism Coupling during Sevoflurane versus Isoflurane Anesthesia in Rats
Authors: Lenz Christian , Rebel Annette , van Ackern Klaus , Kuschinsky Wolfgang , Waschke Klaus F.
Published: November 2003

Background

Compared to isoflurane, knowledge of local cerebral glucose utilization (LCGU) and local cerebral blood flow (LCBF) during sevoflurane anesthesia is limited.

Methods

LCGU, LCBF, and their overall means were measured in Sprague-Dawley rats (8 groups, n=6 each) during sevoflurane and isoflurane anesthesia, 1 and 2 MAC, and in conscious control animals (2 groups, n=6 each) using the autoradiographic 2-[14C]deoxy-D-glucose and 4-iodo-N-methyl-[14C]antipyrine methods.

Results

During anesthesia, mean cerebral glucose utilization was decreased: control, 56+/-5 micronmol x 100 g(-1) x min(-1); 1 MAC isoflurane, 32+/-4 micromol x 100 g(-1) x min(-1) (-43%); 1 MAC sevoflurane, 37+/-5 micromol x 100 g(-1) x min(-1) (-34%); 2 MAC isoflurane, 23+/-3 micromol x 100 g(-1) x min(-1) (-58%); 2 MAC sevoflurane, 23+/-5 micromol x 100 g(-1) x min(-1) (-59%). Local analysis showed a reduction in LCGU in the majority of the 40 brain regions analyzed. Mean cerebral blood flow was increased as follows: control 93+/-8 ml x 100 g(-1) x min(-1); 1 MAC isofurane, 119+/-19 ml x 100 g(-1) x min(-1) (+28%); 1 MAC sevoflurane, 104+/-15 ml x 100 g(-1) x min(-1) (+12%); 2 MAC isoflurane, 149+/-17 ml x 100 g(-1) x min(-1) (+60%); 2 MAC sevoflurane, 118+/-21 ml x 100 g(-1) min(-1) (+27%). LCBF was increased in most brain structures investigated. Correlation coefficients obtained for the relationship between LCGU and LCBF were as follows: control 0.93; 1 MAC isoflurane, 0.89; 2 MAC isoflurane, 0.71; 1 MAC sevoflurane, 0.83; 2 MAC sevoflurane, 0.59).

Conclusion

Mean and local cerebral blood flows were lower during sevoflurane than during isoflurane anesthesia. This difference cannot be explained by differing changes in glucose utilization because glucose utilization was decreased to the same extent in both groups.
A Pharmacodynamic Explanation for the Rapid Onset/Offset of Rapacuronium Bromide
Authors: Wright Peter M. C. , Brown Ronald , Lau Marie , Fisher Dennis M.
Published: November 2003

Background

Nondepolarizing muscle relaxants differ in their time course at the laryngeal adductors and the adductor pollicis, a result of differences in equilibration delays between plasma and effect sites, the sensitivity of each muscle to the relaxant, and the steepness of the concentration-effect relation at each muscle (the Hill factor). To determine whether similar differences exist for rapacuronium, a muscle relaxant with rapid onset and offset, the authors determined its pharmacodynamic characteristics.

Methods

The twitch tensions of the adductor pollicis and the laryngeal adductors (via a tracheal tube cuff positioned at the vocal cords) were measured in 10 volunteers who were anesthetized with propofoL Rapacuronium, 1.5 mg/kg, was given and blood samples were collected. A semiparametric effect compartment pharmacodynamic model was fit to values for rapacuronium plasma concentrations and twitch tension of the adductor pollicis and laryngeal adductors.

Results

Equilibration between the rapacuronium plasma concentration and both effect sites was rapid (typical values for the rate constant for equilibration between plasma and the effect site are 0.405 per min for the adductor pollicis and 0.630 per min for the laryngeal adductors) and was more rapid at the laryngeal adductors than at the adductor pollicis (ratio, 1.59+/-0.16; mean +/- SD). The steady state rapacuronium plasma concentration that depressed twitch tension by 50% and the Hill factor were similar for the two muscles.

Conclusions

The rapid onset and offset of rapacuronium can be explained by the rapid equilibration between concentrations in plasma and at the effect site. Unlike the finding for other nondepolarizing muscle relaxants, the laryngeal muscles are not resistant to rapacuronium.
The Use of Propofol, Nitrous Oxide, or Isoflurane Does Not Affect the Reproductive Success Rate following Gamete Intrafallopian Transfer (GIFT)
Authors: Beilin Yaakov , Bodian Carol A. , Mukherjee Tamoy , Andres Lewis A. , Vincent Robert D. , Hock Doreen L. , Sparks Amy E. T. , Munson Alan K. , Minnich Marie E. , Steinkampf Michael P. , Christman Gregory M. , McKay Robert S. F. , Eisenkraft James B.
Published: November 2003

Background

Whether anesthetic agents administered during gamete intrafallopian transfer (GIFT) affect reproductive outcome is controversial. This multicenter pilot trial and survey had two purposes: to evaluate the effect of propofol, nitrous oxide, midazolam, and isoflurane on pregnancy outcome after GIFT, and to determine if a larger prospective, randomized study is warranted.

Methods

A written invitation was mailed to all 50 fertility programs in the United States that are members of the Society for Assisted Reproductive Technology and perform more than 30 GIFT procedures per year. They were invited to contribute information from the medical records of women who underwent GIFT during the calendar years 1993 and 1994. They were asked to document whether propofol, nitrous oxide, midazolam, a potent inhaled anesthetic agent was used during the GIFT procedure; if the woman became pregnant; and if she delivered at least one live neonate.

Results

Seven medical centers participated and contributed data from 455 women. The clinical pregnancy rate (number of pregnancies/total number of GIFT procedures) and the delivery rate (number of women who delivered at least one live baby/total number of GIFT procedures) were 35% and 32%, respectively. A statistically significant difference could not be found in the clinical pregnancy or delivery rates between those women who received propofol, nitrous oxide, midazolam, or isoflurane during GIFT and those who did not.

Conclusions

No agent-related differences in pregnancy rates were found when propofol, nitrous oxide, isoflurane, or midazolam was used as part of the anesthetic technique for GIFT. Therefore, a more extensive prospective trial does not appear to be warranted.
Perioperative Pulmonary Aspiration in Infants and Children
Authors: Warner Mark A. , Warner Mary E. , Warner David O. , Warner Louise O. , Warner Jackson E.
Published: November 2003

Background

Pulmonary aspiration of gastric contents during the perioperative period in infants and children may be associated with postoperative mortality or pulmonary morbidity. There has not been a recent determination of the frequency of this event and its outcomes in infants and children.

Methods

The authors prospectively identified all cases of pulmonary aspiration of gastric contents during the perioperative courses of 56,138 consecutive patients younger than 18 yr of age who underwent 63,180 general anesthetics for procedures performed in all surgical specialties from July 1985 through June 1997 at the Mayo Clinic.

Results

Pulmonary aspiration occurred in 24 patients (1: 2,632 anesthetics; 0.04%). Children undergoing emergency procedures had a greater frequency of pulmonary aspiration compared to those undergoing elective procedures (1:373 vs. 1:4,544, P < 0.001). Fifteen of the 24 children who aspirated gastric contents did not develop respiratory symptoms within 2 h of aspiration, and none of these 15 developed pulmonary sequelae. Five of these nine children who aspirated and in whom respiratory symptoms developed within 2 h subsequently had pulmonary complications treated with respiratory support (P < 0.003). Three children were treated with mechanical ventilation for more than 48 h, but no child died of sequelae of pulmonary aspiration.

Conclusions

In this study population, the frequency of perioperative pulmonary aspiration in children was quite low. Serious respiratory morbidity was rare, and there were no associated deaths. Infants and children with clinically apparent pulmonary aspiration in whom symptoms did not develop within 2 h did not have respiratory sequelae.
Rocuronium-induced Neuromuscular Block Is Affected by Chronic Carbamazepine Therapy
Authors: Spacek Anna , Neiger Franz X. , Krenn Claus G. , Hoerauf Klaus , Kress Hans G.
Published: November 2003

Background

Patients on chronic anticonvulsant drugs are relatively resistant to certain nondepolarizing neuromuscular blockers such as pancuronium, vecuronium, pipecuronium, doxacurium, or metocurine, but not resistant to mivacurium and atracurium. This study investigated the influence of chronic carbamazepine therapy on the neuromuscular block induced by the new muscle relaxant rocuronium.

Methods

Twenty-two otherwise healthy individuals scheduled for neurosurgical operations were studied: 11 of them were on chronic treatment with carbamazepine; the others served as control subjects. The median duration of carbamazepine therapy was 9 weeks (range, 4-312 weeks). After premedication with oral diazepam, anesthesia was induced with fentanyl and thiopental and maintained with nitrous oxide/oxygen and 0.5% inspired isoflurane. Rocuronium, 0.6 mg/kg (2 x ED95), was given for intubation. The ulnar nerve was stimulated, and the evoked electromyogram recorded using a Datex NMT monitor.

Results

Based on the response to the first of four stimuli, neither the lag time nor the onset-time differed between the two groups. However, the intervals of recovery to 10%, 25%, 50%, and 75% of the baseline response and the recovery index (RI, 25%-75%) were significantly shorter in patients on chronic carbamazepine therapy.

Conclusions

The authors conclude that the duration of the rocuronium-induced neuromuscular block is significantly shortened by preceding chronic carbamazepine therapy.
Dual Actions of Volatile Anesthetics on GABAAIPSCs
Authors: Banks Matthew I. , Pearce Robert A.
Published: November 2003

Background

Volatile agents alter inhibitory postsynaptic currents (IPSCs) at clinically relevant concentrations, an action that is thought to make an important contribution to their behavioral effects. The authors investigated the mechanisms underlying these effects by evaluating the concentration dependence of modulation by enflurane, isoflurane, and halothane of IPSCs in rat hippocampal slices.

Methods

Action potential-independent gamma-aminobutyric acid(A) IPSCs (miniature IPSCs [mIPSCs]) were recorded from CA1 pyramidal neurons. The effects on mIPSC amplitude were used to distinguish between presynaptic (altered release) and postsynaptic (altered receptor response) actions of volatile agents. The concentration dependence of blocking and prolonging actions was compared among the volatile agents to determine whether a single modulatory process could account for both effects.

Results

The application of volatile anesthetics prolonged the decay and reduced the amplitude of mIPSCs in a dose-dependent manner. The effects on decay time for isoflurane and enflurane could not be distinguished. However, the blocking effect of enflurane was significantly greater than that of isoflurane at all concentrations. Despite the blocking effect, the net action of these agents was enhanced inhibition, because charge transfer was always significantly greater than control. Isoflurane, and to a lesser extent enflurane and halothane, caused a picrotoxin-sensitive increase in baseline noise. Moderate increases in mIPSC frequency were also observed for all agents.

Conclusions

These results show that enflurane, isoflurane, and halothane reduce IPSC amplitude through a direct postsynaptic action. Furthermore, the concentration dependence of the actions of the agents reveals a dissociation between the effects on the amplitude and the time course of IPSCs, suggesting that distinct mechanisms underlie the two actions.
Effects of Sodium Nitroprusside and Phenylephrine on Blood Flow in Free Musculocutaneous Flaps during General Anesthesia
Authors: Banic Andrej , Krejci Vladimir , Erni Dominique , Wheatley Anthony M. , Sigurdsson Gisli H.
Published: November 2003

Background

Hypoperfusion and necrosis in free flaps used to correct tissue defects remain important clinical problems. The authors studied the effects of two vasoactive drugs, sodium nitroprusside and phenylephrine, which are used frequently in anesthetic practice, on total blood flow and microcirculatory flow in free musculocutaneous flaps during general anesthesia.

Methods

In a porcine model (n = 9) in which clinical conditions for anesthesia and microvascular surgery were simulated, latissimus dorsi free flaps were transferred to the lower extremity. Total blood flow in the flaps was measured using ultrasound flowmetry and microcirculatory flow was measured using laser Doppler flowmetry. The effects of sodium nitroprusside and phenylephrine were studied during local infusion through the feeding artery of the flap and during systemic administration.

Results

Systemic sodium nitroprusside caused a 30% decrease in mean arterial pressure, but cardiac output did not change. The total flow in the flap decreased by 40% (P < 0.01), and microcirculatory flow decreased by 23% in the skin (P < 0.01) and by 30% in the muscle (P < 0.01) of the flap. Sodium nitroprusside infused locally into the flap artery increased the total flap flow by 20% (P < 0.01). Systemic phenylephrine caused a 30% increase in mean arterial pressure, whereas heart rate, cardiac output, and flap blood flow did not change. Local phenylephrine caused a 30% decrease (P < 0.01) in the total flap flow.

Conclusions

Systemic phenylephrine in a dose increasing the systemic vascular resistance and arterial pressure by 30% appears to have no adverse effects on blood flow in free musculocutaneous flaps. Sodium nitroprusside, however, in a dose causing a 30% decrease in systemic vascular resistance and arterial pressure, causes a severe reduction in free flap blood flow despite maintaining cardiac output.
Spinal Action of Ketorolac, S(+)- and R(-)-ibuprofen on Non-noxious Activation of the Cathechol Oxidation in the Rat Locus Coeruleus
Authors: Hall Sean R. , Milne Brian , Loomis Christopher
Published: November 2003

Background

Blockade of spinal glycine receptors with intrathecal strychnine produces an allodynia-like state in the anesthetized rat. Innocuous hair deflection in the presence of intrathecal strychnine induces a nociceptive-like activation of catechol oxidation in the locus coeruleus and enhances cardiovascular responses. Because prostaglandins play a central role in augmenting pain, this study evaluated the effect of intrathecal nonsteroidal antiinflammatory drugs in strychnine-induced allodynia.

Methods

In urethane-anesthetized rats, changes in catechol oxidation in the locus coeruleus, measured using in vivo voltammetry, and cardiovascular parameters evoked by hair deflection of caudal dermatomes were determined after strychnine (40 microg) or saline were administered intrathecally. Subsequently, the effects of 30 microg ketorolac, 10 microg S(+)-ibuprofen, and 10 microg R(-)-ibuprofen administered intrathecally were evaluated.

Results

After strychnine was administered intrathecally, hair deflection evoked an increase in the locus coeruleus catechol oxidation (peak, 149.7+/-7.2% of baseline) and mean arterial blood pressure (peak, 127.5+/-3.8% of baseline). These responses were not observed after saline was administered intrathecally. All hair deflection-evoked, strychnine-dependent peak responses were attenuated significantly with intrathecally administered ketorolac and S(+)-ibuprofen but not with R(-)-ibuprofen.

Conclusions

Locus coeruleus catechol oxidation is a sensitive biochemical index of strychnine-induced allodynia and is correlated temporally with the cardiovascular responses evoked by hair deflection during spinal glycinergic inhibition. The ability of intrathecally administered ketorolac and S(+)-ibuprofen, but not R(-)-ibuprofen, to suppress the locus coeruleus catechol oxidation and cardiovascular peak responses evoked during strychnine-induced allodynia provide evidence that central prostaglandins play an important role in the abnormal sensory processing of strychnine-induced allodynia.
Increasing Isoflurane from 0.9 to 1.1 Minimum Alveolar Concentration Minimally Affects Dorsal Horn Cell Responses to Noxious Stimulation
Authors: Antognini Joseph F. , Carstens Earl
Published: November 2003

Background

The spinal cord appears to be the site at which isoflurane suppresses movement that occurs in response to a noxious stimulus. In an attempt to localize its site of suppressant action, the authors determined the effect of isoflurane on dorsal horn neuronal responses to supramaximal noxious stimulation at end-tidal concentrations that just permitted and just prevented movement.

Methods

Rats (n = 14) were anesthetized with isoflurane, and after lumbar laminectomy, the minimum alveolar concentration (MAC) for each rat was determined using a supramaximal mechanical stimulus. In these same rats, after extracellular microelectrode placement in the lumbar spinal cord, dorsal horn neuronal responses to the supramaximal stimulus were determined at the concentrations of isoflurane that bracketed each rat's MAC (0.1% higher and lower than MAC). The MAC of isoflurane was then re-determined.

Results

Dorsal horn neuronal response was 1,757+/-892 impulses/min at 0.9 MAC and 1,508+/-988 impulses/min at 1.1 MAC, a 14% decrease (P < 0.05). Cell responses varied, with some cells increasing their response at the higher concentration of isoflurane. The MAC of isoflurane was 1.38+/-0.2% before and 1.34+/-0.2% after determination of dorsal horn neuronal responses.

Conclusions

Isoflurane, at concentrations that bracket MAC, has a variable and minimal depressant effect on dorsal horn cell responses to noxious mechanical stimulation. These data suggest that the major action of isoflurane to suppress movement evoked by a noxious stimulus might occur primarily at a site other than the dorsal horn.
Effect of Propofol on Arachidonate Cascade by Vasopressin in Aortic Smooth Muscle Cells
Authors: Tanabe Kumiko , Kozawa Osamu , Matsuno Hiroyuki , Niwa Masayuki , Dohi Shuji , Uematsu Toshihiko
Published: November 2003

Background

The mechanisms underlying the vascular effects of propofol are not fully understood. Vasopressin, a potent vasoactive peptide, stimulates the arachidonate cascade and the synthesis of prostacyclin (PGI2; the main metabolite of the cascade in vascular smooth muscle cells). Arachidonic acid (AA) release by phospholipases is the rate-limiting step in the cascade. We investigated the mechanisms underlying vasopressin-induced AA release and the effect of propofol on PGI2 synthesis in a rat aortic smooth muscle cell line: A10 cells.

Methods

In cultured A10 cells pretreated with propofol, the stimulation by vasopressin of AA release and PGI2 synthesis was evaluated by measuring [3H]AA and 6-keto PGF1alpha, respectively, in the culture medium. The effects of propofol on vasopressin-induced activation of phosphoinositide-hydrolyzing phospholipase C and phosphatidylcholine-hydrolyzing phospholipase D were evaluated by measuring inositol phosphate formation and choline formation, respectively.

Results

A phospholipase C inhibitor and a phosphatidic acid phosphohydrolase inhibitor both attenuated vasopressin-induced AA release and PGI2 synthesis, as did a phospholipase A2 inhibitor. Propofol inhibited vasopressin-induced activation of phosphoinositide-hydrolyzing phospholipase C and phosphatidylcholine-hydrolyzing phospholipase D, but this effect of propofol was significant only at supraclinical concentration (0.1 mM). Propofol reduced vasopressin-induced PGI2 synthesis. The inhibitory effect was observed at concentrations (10 microM-0.1 mM) higher than those used clinically.

Conclusions

Propofol suppresses the arachidonate cascade caused by vasopressin at least partly by inhibiting phosphoinositide-hydrolyzing phospholipase C and phosphatidylcholine-hydrolyzing phospholipase D, resulting in the inhibition of PGI2 synthesis. Propofol-mediated inhibition of vasopressin-stimulated synthesis of PGI2 may reduce the vasorelaxation by propofol.
A Cost-construction Model to Assess the Total Cost of an Anesthesiology Residency Program
Authors: Franzini Luisa , Berry James M.
Published: November 2003

Background

Although the total costs of graduate medical education are difficult to quantify, this information may be of great importance for health policy and planning over the next decade. This study describes the total costs associated with the residency program at the University of Texas--Houston Department of Anesthesiology during the 1996-1997 academic year.

Methods

The authors used cost-construction methodology, which computes the cost of teaching from information on program description, resident enrollment, faculty and resident salaries and benefits, and overhead. Surveys of faculty and residents were conducted to determine the time spent in teaching activities; access to institutional and departmental financial records was obtained to quantify associated costs. The model was then developed and examined for a range of assumptions concerning resident productivity, replacement costs, and the cost allocation of activities jointly producing clinical care and education.

Results

The cost of resident training (cost of didactic teaching, direct clinical supervision, teaching-related preparation and administration, plus the support of the teaching program) was estimated at $75,070 per resident per year. This cost was less than the estimated replacement value of the teaching and clinical services provided by residents, $103,436 per resident per year. Sensitivity analysis, with different assumptions regarding resident replacement cost and reimbursement rates, varied the cost estimates but generally identified the anesthesiology residency program as a financial asset.

Conclusions

In most scenarios, the value of the teaching and clinical services provided by residents exceeded the cost of the resources used in the educational program.
Antiemetic Prophylaxis Does Not Improve Outcomes after Outpatient Surgery When Compared to Symptomatic Treatment
Authors: Scuderi Phillip E. , James Robert L. , Harris Lynne , Mims Grover R.
Published: November 2003

Background

Although prophylactic administration of antiemetics reduces the incidence of postoperative nausea, vomiting, or both (PONV), there is little evidence to suggest this improves patient outcomes. The authors hypothesized that early symptomatic treatment of PONV will result in outcomes, including time to discharge, unanticipated admission, patient satisfaction, and time to return to normal daily activities, that are similar to those achieved with routine prophylaxis.

Methods

Men and women (n = 575) scheduled for outpatient surgery during general anesthesia were randomized to receive either 4 mg intravenous ondansetron or placebo before operation and either 1 mg intravenous ondansetron or placebo if postoperative symptomatic treatment of PONV was necessary. Patients were stratified into subgroups by risk factors for PONV.

Results

No differences occurred in the time to discharge, rate of unanticipated admission, or time to return to normal activity between the prophylaxis and treatment groups. The reported level of satisfaction with control of PONV was 93% in the treatment arm and 97% in the prophylaxis arm, which fall within the limits defined a priori as clinically equivalent. Female patients with a history of motion sickness or PONV who were undergoing highly emetogenic procedures had a higher reported level of satisfaction with prophylaxis than with treatment (100% vs. 90%, P = 0.043); however, the level of satisfaction with the overall outpatient surgical experience was not different.

Conclusion

Although PONV is unpleasant, the data indicate little difference in outcomes when routine prophylactic medications are administered versus simply treating PONV should symptoms occur.
Airway Obstruction and Perioperative Complications in Smokers Undergoing Abdominal Surgery
Authors: Warner David O. , Warner Mark A. , Offord Kenneth P. , Schroeder Darrell R. , Maxson Pamela , Scanlon Paul D.
Published: November 2003

Background

The goal of this study was to determine whether airway obstruction determined by preoperative spirometry predicts perioperative complications in smokers undergoing abdominal surgery whose treatment is managed according to current clinical practice.

Methods

A pulmonary function database identified patients undergoing abdominal surgery who met the following criteria for airway obstruction (n = 135): a forced expiratory volume less than 40% of predicted normal value, a forced expiratory volume:forced vital capacity ratio less than the lower limit of predicted normal, a smoking history of more than 20 pack-years, and an age older than 35 yr. A group of patients without airway obstruction (n = 135) was matched for gender, surgical site (upper vs. lower abdominal), smoking history, and age. Medical records were reviewed by an abstractor to identify perioperative complications that occurred within 30 days after surgery.

Results

The forced expiratory volume values were 0.9+/-0.21 (mean +/- SD) and 2.9+/-0.61 in patients with and without airway obstruction, respectively. When analyzed by conditional logistic regression using the 1:1 matched-pairs feature, including age, pack-year smoking history, site of incision, and current smoking status as covariates, in patients with airway obstruction bronchospasm was more likely to develop (odds ratio, 6.9 [95% confidence interval, 1.2 to 38.4]) but the patients were not more likely to need prolonged endotracheal intubation (odds ratio, 1.1 [95% confidence interval, 0.4 to 3.2]). They were also no more likely to need prolonged intensive care admission or readmission. The frequency of other complications was less than 5%.

Conclusion

When other factors were considered, preoperative airway obstruction predicted the occurrence of bronchospasm, but not prolonged endotracheal intubation, in smokers undergoing abdominal surgery who are treated according to current clinical practices.
Effect of Oxygen Treatment on Heart Rate after Abdominal Surgery
Authors: Rosenberg-Adamsen Susan , Lie Claus , Bernhard Anne , Kehlet Henrik , Rosenberg Jacob
Published: November 2003

Background

Cardiac complications are common during the postoperative period and may be associated with hypoxemia and tachycardia. Preliminary studies in high-risk patients after operation have shown a possible beneficial effect of oxygen therapy on arterial oxygen saturation and heart rate.

Methods

The authors studied the effect of oxygen therapy on arterial oxygen saturation and heart rate in 100 consecutive unselected patients randomly and double blindly allocated to receive air or oxygen therapy between the first and fourth day after major abdominal surgery.

Results

The median arterial oxygen saturation rate increased significantly from 96% to 99% (P < 0.0001) and the heart rate decreased significantly from 85 beats/min to 81 beats/min (P < 0.0001) during oxygen supplementation compared with air administered by a binasal catheter. The greatest decrease in heart rate occurred in patients with the lowest oxygen saturation or the highest heart rate values before oxygen supplementation. Overall, 73% of this unselected group of patients responded with decreased heart rate during supplemental oxygen therapy. No significant differences in changes in heart rate after oxygen supplementation were found between patients with or without an epidural catheter or between the postoperative day studied.

Conclusion

Postoperative oxygen therapy increased arterial oxygen saturation and decreased heart rate after uncomplicated abdominal surgery in a consecutive unselected group of patients who received routine postoperative care.
Endotracheal Intubation, but Not Laryngeal Mask Airway Insertion, Produces Reversible Bronchoconstriction
Authors: Kim Eun S. , Bishop Michael J.
Published: November 2003

Background

Tracheal intubation frequently results in an increase in respiratory system resistance that can be reversed by inhaled bronchodilators. The authors hypothesized that insertion of a laryngeal mask airway would be less likely to result in reversible bronchoconstriction than would insertion of an endotracheal tube.

Methods

Fifty-two (45 men, 7 women) patients were randomized to receive a 7.5-mm (women) or 8-mm (men) endotracheal tube or a No. 4 (women) or No. 5 (men) laryngeal mask airway. Anesthesia was induced with 2 microg/kg fentanyl and 5 mg/kg thiopental, and airway placement was facilitated with 1 mg/kg succinylcholine. When a seal to more than 20 cm water was verified, respiratory system resistance was measured immediately after airway placement. Inhalation anesthesia was begun with isoflurane to achieve an end-tidal concentration of 1% for 10 min. Respiratory system resistance was measured again during identical conditions.

Results

Among patients receiving laryngeal mask airways, the initial respiratory system resistance was significantly less than among patients with endotracheal tubes (9.2+/-3.3 cm water x 1(-1) x s(-1) [mean +/- SD] compared with 13.4+/-9.6 cm water x 1(-1) x s(-1); P < 0.05). After 10 min of isoflurane, the resistance decreased to 8.6+/-3.6 cm water x 1(-1) x s(-1) in the endotracheal tube group but remained unchanged at 9.1+/-3.3 cm water x 1(-1) x s(-1) in the laryngeal mask airway group. The decrease in respiratory system resistance in the endotracheal tube group of 4.7+/-7 cm water x 1(-1) x s(-1) was highly significant compared with the lack of change in the laryngeal mask airway group (P < 0.01).

Conclusions

Resistance decreased rapidly only in patients with endotracheal tubes after they received isoflurane, a potent bronchodilator, suggesting that reversible bronchoconstriction was present in patients with endotracheal tubes but not in those with laryngeal mask airways. A laryngeal mask airway is a better choice of airway to minimize airway reaction.
The Effect of Fentanyl on Sevoflurane Requirements for Somatic and Sympathetic Responses to Surgical Incision
Authors: Katoh Takasumi , Kobayashi Syunji , Suzuki Akira , Iwamoto Tatsuaki , Bito Hiromichi , Ikeda Kazuyuki
Published: November 2003

Background

Fentanyl produces a reduction in the minimum alveolar concentration (MAC) of isoflurane and desflurane needed to blockade adrenergic response (BAR) to surgical incision in 50% of patients (MAC-BAR). MAC-BAR of sevoflurane and the reduction in MAC-BAR of sevoflurane by fentanyl have not been described previously. The purpose of this study was to determine the MAC and MAC-BAR reduction of sevoflurane by fentanyl with and without nitrous oxide (N2O).

Methods

Two hundred twenty-six patients were randomly assigned to one of two groups: a sevoflurane group and a sevoflurane/N2O group. Patients in each group were randomly assigned to one of five different fentanyl concentration subgroups. Patients were anesthetized with sevoflurane and fentanyl in the sevoflurane group and with sevoflurane, fentanyl, and N2O (66 vol%) in the sevoflurane/N2O group. Somatic and sympathetic responses to surgical incision were observed for MAC and MAC-BAR assessment at predetermined concentrations of sevoflurane.

Results

Fentanyl produced an initial steep reduction in the MAC and MAC-BAR of sevoflurane, with 3 ng/ml resulting in a 61% reduction in MAC and an 83% reduction in MAC-BAR. A ceiling effect was observed for MAC and MAC-BAR, with 6 ng/ml fentanyl providing only an additional 13% and 9% reduction in MAC and MAC-BAR, respectively. In the presence of 66 vol% N2O, MAC and MAC-BAR of sevoflurane were reduced with increasing concentrations of fentanyL A ceiling effect was not observed for reduction in MAC and MAC-BAR in the presence of N2O.

Conclusions

MAC and MAC-BAR decreased similarly with increasing concentrations of fentanyl in plasma, showing an initial steep reduction followed by a ceiling effect. In the presence of N2O, MAC and MAC-BAR decreased similarly but did not exhibit a ceiling effect.
Dexmedetomidine Failed to Block the Acute Hyperdynamic Response to Electroconvulsive Therapy
Authors: Fu Wen , White Paul F.
Published: November 2003

Background

Orally administered clonidine (0.2-0.3 mg) has been reported to decrease the acute hypertensive response to electroconvulsive therapy (ECT) without prolonging early recovery. This preliminary study was designed to evaluate the acute hemodynamic effects of the investigational alpha2-adrenergic agonist, dexmedetomidine, in patients undergoing a series of ECT treatments.

Methods

Six patients undergoing a series of three to six consecutive ECT treatments were studied according to a randomized, double-blind, placebo-controlled protocol All patients received either saline or dexmedetomidine, 0.5 or 1.0 microg/kg intravenously, 10-30 min before induction of anesthesia for ECT using a standardized anesthesia protocol. In addition to assessing the cardiovascular variables, the duration of seizure activity, degree of sedation, and time to discharge from the Phase I recovery unit were assessed.

Results

Although dexmedetomidine produced dose-related increases in the level of sedation before the ECT procedure, it failed to decrease the peak blood pressure and heart rate responses after the ECT treatment. The 0.5 and 1.0 microg/kg doses of dexmedetomidine prolonged the times to orientation and to discharge from the Phase I unit.

Conclusions

The results of this pilot study suggest that dexmedetomidine (0.5-1.0 microg/kg given intravenously) is not beneficial in controlling the acute hyperdynamic response after ECT.
Ondansetron Is Effective to Treat Spinal or Epidural Morphine-induced Pruritus
Authors: Borgeat Alain , Stirnemann Hans-Ruedi
Published: November 2003

Background

Spinally and epidurally administered morphine is frequently associated with pruritus. Isolated case reports indicate that ondansetron may be effective in this context. This study aims to investigate the effectiveness of ondansetron to treat this side effect.

Methods

In a prospective, randomized, double-blind, placebo-controlled study, 100 patients with pruritus (> 4 on a visual analog scale, on which 0 represents no pruritus and 10 represents worst pruritus imaginable) after spinal or epidural administration of morphine, received either 8 mg ondansetron intravenously (ondansetron group) in 100 ml NaCl 0.9% or vehicle (placebo group). A decrease of more than 4 points on the visual analog scale 60 min after treatment was considered a success. Changes in levels of pain and sedation, hemodynamic values, and other side effects were checked regularly. The presence or absence of pruritus was assessed for the last time 24 h later.

Results

The two groups were similar for demographic characteristics, the route of administration of morphine, and severity of pruritus at the beginning of the study. The ondansetron group showed a success rate of 70% versus 30% for the placebo group (P > 0.05). Among the successfully treated patients, three (9%) in the ondansetron group and six (40%) in the placebo group reported the recurrence of pruritus (P < 0.05). Among the successfully treated patients, none complained of residual pruritus 24 h later. No changes in pain or sedation levels were noted. Hemodynamic values remained stable, hemoglobin oxygen saturation did not decrease, and no other side effects were observed.

Conclusion

The administration of 8 mg ondansetron intravenously is an effective treatment for spinally or epidurally administered morphine-induced pruritus. In this clinical condition the treatment is safe and well tolerated.