bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential Modulation of the Cardiac Adenosine Triphosphate-sensitive Potassium Channel by Isoflurane and Halothane
Authors: Kwok Wai-Meng , Martinelli Anne T. , Fujimoto Kazuhiro , Suzuki Akihiro , Stadnicka Anna , Bosnjak Zeljko J.
Published: November 2003

Background

The cardiac adenosine triphosphate-sensitive potassium (K(ATP)) channel is activated during pathophysiological episodes such as ischemia and hypoxia and may lead to beneficial effects on cardiac function. Studies of volatile anesthetic interactions with the cardiac K(ATP) channel have been limited. The goal of this study was to investigate the ability of volatile anesthetics halothane and isoflurane to modulate the cardiac sarcolemmal K(ATP) channel.

Methods

The K(ATP) channel current (I(KATP)) was monitored using the whole cell configuration of the patch clamp technique from single ventricular cardiac myocytes enzymatically isolated from guinea pig hearts. I(KATP) was elicited by extracellular application of the potassium channel openers 2,4-dinitrophenol or pinacidil.

Results

Volatile anesthetics modulated I(KATP) in an anesthetic-dependent manner. Isoflurane facilitated the opening of the K(ATP) channel. Following initial activation of I(KATP) by 2,4-dinitrophenol, isoflurane at 0.5 and 1.3 mm further increased current amplitude by 40.4 +/- 11.1% and 58.4 +/- 20.6%, respectively. Similar results of isoflurane were obtained when pinacidil was used to activate I(KATP). However, isoflurane alone was unable to elicit K(ATP) channel opening. In contrast, halothane inhibited I(KATP) elicited by 2,4-dinitrophenol by 50.6 +/- 5.8% and 72.1 +/- 11.6% at 0.4 and 1.0 mm, respectively. When I(KATP) was activated by pinacidil, halothane had no significant effect on the current.

Conclusions

The cardiac sarcolemmal K(ATP) channel is differentially modulated by volatile anesthetics. Isoflurane can facilitate the further opening of the K(ATP) channel following initial channel activation by 2,4-dinitrophenol or pinacidil. The effect of halothane was dependent on the method of channel activation, inhibiting I(KATP) activated by 2,4-dinitrophenol but not by pinacidil.
Anesthestic-related Cardiac Arrest and Its Mortality
Authors: Newland Myrna C. , Ellis Sheila J. , Lydiatt Carol A. , Peters K. Reed , Tinker John H. , Romberger Debra J. , Ullrich Fred A. , Anderson James R.
Published: November 2003

Background

A prospective and retrospective case analysis study of all perioperative cardiac arrests occurring during a 10-yr period from 1989 to 1999 was done to determine the incidence, cause, and outcome of cardiac arrests attributable to anesthesia.

Methods

One hundred forty-four cases of cardiac arrest within 24 h of surgery were identified over a 10-yr period from an anesthesia database of 72,959 anesthetics. Case abstracts were reviewed by a Study Commission composed of external and internal members in order to judge which cardiac arrests were anesthesia-attributable and which were anesthesia-contributory. The rates of anesthesia-attributable and anesthesia-contributory cardiac arrest were estimated.

Results

Fifteen cardiac arrests out of a total number of 144 were judged to be related to anesthesia. Five cardiac arrests were anesthesia-attributable, resulting in an anesthesia-attributable cardiac arrest rate of 0.69 per 10,000 anesthetics (95% confidence interval, 0.085-1.29). Ten cardiac arrests were found to be anesthesia-contributory, resulting in an anesthesia-contributory rate of 1.37 per 10,000 anesthetics (95% confidence interval, 0.52-2.22). Causes of the cardiac arrests included medication-related events (40%), complications associated with central venous access (20%), problems in airway management (20%), unknown or possible vagal reaction in (13%), and one perioperative myocardial infarction. The risk of death related to anesthesia-attributable perioperative cardiac arrest was 0.55 per 10,000 anesthetics (95% confidence interval, 0.011-1.09).

Conclusions

Most perioperative cardiac arrests were related to medication administration, airway management, and technical problems of central venous access. Improvements focused on these three areas may result in better outcomes.
Impact of Unplanned Extubation and Reintubation after Weaning on Nosocomial Pneumonia Risk in the Intensive Care Unit
Authors: de Lassence Arnaud , Alberti Corinne , Azoulay Élie , Le Miere Eric , Cheval Christine , Vincent François , Cohen Yves , Garrouste-Orgeas Maïté , Adrie Christophe , Troche Gilles , Timsit Jean-François
Published: November 2003

Background

The authors prospectively evaluated the occurrence and outcomes of unplanned extubations (self-extubation and accidental extubation) and reintubation after weaning, and examined the hypothesis that these events may differ regarding their influence on the risk of nosocomial pneumonia.

Methods

Data were taken from a prospective, 2-yr database including 750 mechanically ventilated patients from six intensive care units.

Results

One hundred five patients (14%) experienced at least one episode of these 3 events; 51 self-extubations occurred in 38 patients, 24 accidental extubations in 22 patients, and 56 reintubations after weaning in 45 patients. The incidence density of these 3 events was 16.4 per 1,000 mechanical ventilation days. Reintubation within 48 h was needed consistently after accidental extubation but was unnecessary in 37% of self-extubated patients. Unplanned extubation and reintubation after weaning were associated with longer total mechanical ventilation (17 vs. 6 days; P < 0.0001), intensive care unit stay (22 vs. 9 days; P < 0.0001), and hospital stay (34 vs. 18 days; P < 0.0001) than in control group, but did not influence intensive care unit or hospital mortality. The incidence of nosocomial pneumonia was significantly higher in patients with unplanned extubation or reintubation after weaning (27.6% vs. 13.8%; P = 0.002). In a Cox model adjusting on severity at admission, unplanned extubation and reintubation after weaning increased the risk of nosocomial pneumonia (relative risk, 1.80; 95% confidence interval, 1.15-2.80; P = 0.009). This risk increase was entirely ascribable to accidental extubation (relative risk, 5.3; 95% confidence interval, 2.8-9.9; P < 0.001).

Conclusion

Accidental extubation but not self-extubation or reintubation after weaning increased the risk of nosocomial pneumonia. These 3 events may deserve evaluation as an indicator for quality-of-care studies.
Esmolol Improves Left Ventricular Function via Enhanced β-Adrenergic Receptor Signaling in a Canine Model of Coronary Revascularization
Authors: Booth John V. , Spahn Donat R. , McRae Robert L. , Chesnut Lynn C. , El-Moalem Habib , Atwell Darryl M. , Leone Bruce J. , Schwinn Debra A.
Published: November 2003

Background

Recent American Heart Association guidelines highlight the paucity of data on effectiveness and/or mechanisms underlying use of beta-adrenergic receptor (beta AR) antagonists after acute coronary syndromes in patients subsequently undergoing revascularization. It is important to assess whether beta AR antagonists might protect the heart and improve ventricular function in this scenario. The authors therefore used esmolol (an ultra-short-acting beta AR antagonist) to determine whether beta AR antagonist treatment improves left ventricular function in a canine model of acute reversible coronary ischemia followed by coronary reperfusion during cardiopulmonary bypass (CPB). The authors also tested whether the mechanism includes preserved beta AR signaling.

Methods

Dogs were randomized to either esmolol or saline infusions administered during CPB (n = 29). Pre-CPB and end-CPB transmyocardial left ventricular biopsies were obtained; plasma catecholamine concentrations, myocardial beta AR density, and adenylyl cyclase activity were measured. In addition, left ventricular systolic shortening and postsystolic shortening were determined immediately prior to each biopsy.

Results

While beta AR density remained unchanged in each group, isoproterenol-stimulated adenylyl cyclase activity decreased 26 +/- 6% in the control group but increased 38 +/- 10% in the esmolol group (pre-CPB to end-CPB, mean +/- SD, P = 0.0001). Left ventricular systolic shortening improved in both groups after release of coronary (LAD) ligature; however, the esmolol group increased to 72 +/- 23% of pre-CPB values compared to 48 +/- 12% for the control group (P = 0.0008).

Conclusions

These data provide prospective evidence that esmolol administration results in improved myocardial function. Furthermore, the mechanism appears to involve enhanced myocardial beta AR signaling.
Effect of Intrathecal Non-NMDA EAA Receptor Antagonist LY293558 in Rats
Authors: Von Bergen Nicholas H. , Subieta Alberto , Brennan Timothy J.
Published: November 2003

Background

Excitatory amino acid receptors are important for both sensory and motor function in the spinal cord. We studied the effects of intrathecal LY293558, a competitive non-N-methyl-D-aspartate excitatory amino acid receptor antagonist, on motor and sensory function in rats to determine whether drugs blocking these receptors could potentially be used as alternative agents to local anesthetics for spinal anesthesia.

Methods

Rats were tested before and 15-240 min after intrathecal injection of 5 nmol (in 10 microl) LY293558. Sensory function was tested at the hind paw using withdrawal response to pin prick and withdrawal to pinch with sharp forceps. Motor performance (ambulation, placing reflex, and Rotorod time), blood pressure, and heart rate were also evaluated. Some tests were repeated the next day. Responses after LY293558 were compared to injection of 40 microl bupivacaine, 0.75%. Pin-prick responses at the forepaw, chest, abdomen, hind leg, and hind paw were also examined after intrathecal LY293558.

Results

Intrathecal LY293558 blocked both sensory and motor responses through 180 min; complete recovery was present the following day. No change in blood pressure or heart rate occurred. The effects of LY293558 were more pronounced and sustained than those of bupivacaine. Segmental blockade of the response to pin prick was present after LY293558.

Conclusion

Drugs like LY293558 that block alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA)/kainate receptors may be an alternative to local anesthetics for spinal anesthesia in humans.
Influence of Lung Aeration on Pulmonary Concentrations of Nebulized and Intravenous Amikacin in Ventilated Piglets with Severe Bronchopneumonia
Authors: Elman Marilia , Goldstein Ivan , Marquette Charles-Hugo , Wallet Fréderic , Lenaour Gilles , Rouby Jean-Jacques
Published: November 2003

Background

Pulmonary concentrations of aminoglycosides administered intravenously are usually low in the infected lung parenchyma. Nebulization represents an alternative to increase pulmonary concentrations, although the obstruction of bronchioles by purulent plugs may impair lung deposition by decreasing lung aeration.

Methods

An experimental bronchopneumonia was induced in anesthetized piglets by inoculating lower lobes with a suspension of 10(6) cfu/ml Escherichia coli. After 24 h of mechanical ventilation, 7 animals received two intravenous injections of 15 mg/kg amikacin, and 11 animals received two nebulizations of 40 mg/kg amikacin at 24-h intervals. One hour following the second administration, animals were killed, and multiple lung specimens were sampled for assessing amikacin pulmonary concentrations and quantifying lung aeration on histologic sections.

Results

Thirty-eight percent of the nebulized amikacin (15 mg/kg) reached the tracheobronchial tree. Amikacin pulmonary concentrations were always higher after nebulization than after intravenous administration, decreased with the extension of parenchymal infection, and were significantly influenced by lung aeration: 197 +/- 165 versus 6 +/- 5 microg/g in lung segments with focal bronchopneumonia (P = 0.03), 40 +/- 62 versus 5 +/- 3 microg/g in lung segments with confluent bronchopneumonia (P = 0.001), 18 +/- 7 versus 7 +/- 4 microg/g in lung segments with lung aeration of 30% or less, and 65 +/- 9 versus 2 +/- 3 microg/g in lung segments with lung aeration of 50% or more.

Conclusions

In a porcine model of severe bronchopneumonia, the nebulization of amikacin provided 3-30 times higher pulmonary concentrations than the intravenous administration of an equivalent dose. The greater the lung aeration, the higher were the amikacin pulmonary concentrations found in the infected lung segments.
Effect of N2O on Sevoflurane Vaporizer Settings during Minimal- and Low-flow Anesthesia
Authors: Hendrickx Jan F. A. , Coddens José , Callebaut Frederik , Artico Hermes , Deloof Thierry , Demeyer Ignace , De Wolf Andre M.
Published: November 2003

Background

Uptake of a second gas of a delivered gas mixture decreases the amount of carrier gas and potent inhaled anesthetic leaving the circle system through the pop-off valve. The authors hypothesized that the vaporizer settings required to maintain constant end-expired sevoflurane concentration (Etsevo) during minimal-flow anesthesia (MFA, fresh gas flow of 0.5 l/min) or low-flow anesthesia (LFA, fresh gas flow of 1 l/min) would be lower when sevoflurane is used in oxygen-nitrous oxide than in oxygen.

Methods

Fifty-six patients receiving general anesthesia were randomly assigned to one of four groups (n = 14 each), depending on the carrier gas and fresh gas flow used: group Ox.5 l (oxygen, MFA), group NOx.5 l (oxygen-nitrous oxide, MFA after 10 min high fresh gas flow), group Ox1 l (oxygen, LFA), and group NOx1 l (oxygen-nitrous oxide, LFA after 10 min high fresh gas flow). The vaporizer dial settings required to maintain Etsevo at 1.3% were compared between groups.

Results

Vaporizer settings were higher in group Ox.5 l than in groups NOx.5 l, Ox1 l, and NOx1 l; vaporizer settings were higher in group NOx.5 l than in group NOx1 l between 23 and 47 min, and vaporizer settings did not differ between groups Ox1 l and NOx1 l.

Conclusions

When using oxygen-nitrous oxide as the carrier gas, less gas and vapor are wasted through the pop-off valve than when 100% oxygen is used. During MFA with an oxygen-nitrous oxide mixture, when almost all of the delivered oxygen and nitrous oxide is taken up by the patient, the vaporizer dial setting required to maintain a constant Etsevo is lower than when 100% oxygen is used. With higher fresh gas flows (LFA), this effect of nitrous oxide becomes insignificant, presumably because the proportion of excess gas leaving the pop-off valve relative to the amount taken up by the patient increases. However, other unexplored factors affecting gas kinetics in a circle system may contribute to our observations.
Cardiac Troponin I Is an Independent Predictor of In-hospital Death after Adult Cardiac Surgery
Authors: Lasocki Sigismond , Provenchère Sophie , Bénessiano Joëlle , Vicaut Eric , Lecharny Jean-Baptiste , Desmonts Jean-Marie , Dehoux Monique , Philip Ivan
Published: November 2003

Background

Although myocardial injury during cardiac surgery is associated with impaired clinical outcome, little is known about the prognostic value of cardiac troponin I (cTnI), a cardiac-specific biologic marker. The purpose of this prospective study was to evaluate the prognostic value of cTnI concentrations measured 20 h after the end of surgery in adult patients undergoing coronary artery bypass grafting or conventional valve surgery.

Methods

Baseline and perioperative characteristics of 502 consecutive patients undergoing conventional heart surgery during a 1-yr period were collected. In-hospital death (n = 28) and major clinical outcomes, e.g., low cardiac output, ventricular arrhythmia, and renal failure, were recorded.

Results

Multivariate analysis, using a stepwise logistic regression, showed that cTnI concentration was an independent predictor of in-hospital mortality (for cTnI concentration > 13 ng/ml, odds ratio = 6.7 [95% confidence interval, 2.3-19.3]), as were diabetes, altered preoperative cardiac function, emergent surgery, cardiopulmonary bypass duration, postoperative Pao2 level and total chest drainage volume. Further, elevated cTnI concentrations were associated with a cardiac cause of death and with major clinical outcomes.

Conclusions

Our results demonstrated that cTnI concentration measured 20 h after the end of surgery is an independent predictor of in-hospital death after cardiac surgery. In addition, elevated concentrations of cTnI are associated with a cardiac cause of death and with major postoperative complications.
Using Amsorb to Detect Dehydration of CO2Absorbents Containing Strong Base
Authors: Knolle Erich , Linert Wolfgang , Gilly Hermann
Published: November 2003

Background

Because Amsorb changes color when it dries, the authors investigated whether Amsorb combined with different strong base-containing carbon dioxide absorbents signals dehydration of such absorbents.

Methods

Five different carbon dioxide absorbents (1,330 g) each topped with 70 g of Amsorb were dried in an anesthesia machine (Modulus CD, Datex-Ohmeda, Madison, WI) with oxygen (Amsorb layer at the fresh gas inflow site). As soon as a color change was detected in the Amsorb, the authors tested the samples for a change in weight and carbon monoxide formation from 7.5% desflurane or 4% isoflurane. In a different experiment with the five absorbents, Amsorb was layered at the drying gas outflow site. In further experiments, the authors tested for a color change in Amsorb from drying and rehydrating and from drying with nitrogen. Finally, they dried a mixture of Amsorb and 1% NaOH and examined it for color change.

Results

In the experiments with Amsorb layered at the inflow, the Amsorb changed color when the water content of the samples was only marginally reduced (to a mean 13.6%), and no carbon monoxide formed. With Amsorb layered at the outflow, it changed color when the mean water content of the samples was reduced to 8.8%, and carbon monoxide formation was detected to varying degrees. The color change was independent of the drying gas and could be reversed by rehydrating. Adding NaOH to Amsorb prevented a color change.

Conclusions

Dehydration in strong base-containing absorbents can reliably be indicated before carbon monoxide is formed when Amsorb is layered at the fresh gas inflow. The authors assume that the indicator dye in Amsorb changes color on drying because of the absence of strong base in this absorbent.
Hydroxyethyl Starch (130 kD), but Not Crystalloid Volume Support, Improves Microcirculation during Normotensive Endotoxemia
Authors: Hoffmann Johannes N. , Vollmar Brigitte , Laschke Matthias W. , Inthorn Dietrich , Schildberg Friedrich W. , Menger Michael D.
Published: November 2003

Background

Increased leukocyte-endothelial cell interaction (LE) and deterioration of capillary perfusion represent key mechanisms of septic organ dysfunction. The type of volume support, however, which may be used during septic disorders, remains controversial. Using intravital microscopy, the authors studied the effect of different regimens of clinically relevant volume support on endotoxin-induced microcirculatory disorders, including the synthetic colloid hydroxyethyl starch (HES, 130 kD) and a crystalloid regimen with isotonic saline solution (NaCl).

Methods

In Syrian Golden hamsters, normotensive endotoxemia was induced by intravenous application of Escherichia coli lipopolysaccharide (LPS, 2 mg/kg). The microcirculation was analyzed in striated muscle of skinfold preparations. HES 130 kD (Voluven(R), 16 ml/kg, n = 7) or isotonic saline (NaCl, 66 ml/kg, n = 6) were infused 3 h after LPS exposure over a 1-h period (posttreatment mode). Animals receiving LPS without volume therapy served as control subjects (n = 8, control). LE, functional capillary density (FCD), and macromolecular leakage were repeatedly analyzed in the awake animals during a 24-h period using intravital fluorescence microscopy.

Results

HES 130 kD significantly reduced LPS-induced arteriolar and venular leukocyte adherence (P < 0.05), whereas NaCl resuscitation had no effect when compared with nontreated control animals. The LPS-induced decrease in FCD and increase in macromolecular leakage were also significantly attenuated by HES 130 kD but not by NaCl. Improvement of LPS-induced microcirculatory disorders by HES was unlikely the result of macro- and microhemodynamic changes because arterial blood pressure, heart rate, and venular wall shear rate did not differ between HES- and NaCl-treated animals.

Conclusions

Thus, our study provides microhemodynamic and cellular mechanisms of HES 130 kD-mediated protection on microcirculation during endotoxemia, even when used in a clinically relevant posttreatment mode during normotensive conditions.
Variability in the Magnitude of the Cerebral Blood Flow Response and the Shape of the Cerebral Blood Flow: Pressure Autoregulation Curve during Hypotension in Normal Rats
Authors: Jones Stephen C. , Radinsky Carol R. , Furlan Anthony J. , Chyatte Douglas , Qu Yinsheng , Easley Kirk A. , Perez-Trepichio Alejandro D.
Published: November 2003

Background

The maintenance of constant cerebral blood flow (CBF) as mean cerebral perfusion pressure (CPP) varies is commonly referred to as CBF-pressure autoregulation. The lower limit of autoregulation is the CPP at which the vasodilatory capacity is exhausted and flow falls with pressure. We evaluated variability in the magnitude of percent change in CBF during the hypotensive portion of the autoregulatory curve. We hypothesize that this variability, in normal animals, obeys a Gaussian distribution and characterizes a vasodilatory mechanism that is inherently different from that described by the lower limit.

Methods

Sixty-five male Sprague-Dawley rats were anesthetized with 0.5-1% halothane and 70% nitrous oxide in oxygen. Body temperature was maintained at 37 degrees C. Using a closed, superfused cranial window, CBF (as % of control) was determined using laser Doppler flowmetry (LDF) through the window with the intracranial pressure set at 10 mmHg. Animals with low vascular reactivity to inhaled carbon dioxide and superfused adenosine diphosphate (ADP) or acetylcholine were excluded. MABP was sequentially lowered by exsanguination to 100, 85, 70, 55, and 40 mmHg. Using the %CBF versus CPP plots for each curve (1) the lower limit of autoregulation was identified; (2) the pattern of autoregulation was classified as "peak" (a rise in LDF flow of at least 15% as arterial pressure was dropped), "classic" (plateau with a fall), or "none" (a fall in LDF flow of greater than 15%); (3) the area under the autoregulatory curve between CPPs of 30 and 90 mmHg was calculated; and (4) the magnitude of the %CBF response to hypotension was assessed by determining the %CBF at a CPP of 60 mmHg (%CBFCPP60).

Results

Of the 65 curves, 21 had the peak pattern, 33 the classic pattern, and 11 the none pattern. The %CBFCPP60 and autoregulatory area displayed Gaussian distributions, consistent with normal variability. Although %CBFCPP60, autoregulatory area, and pattern were significantly correlated (r or rho > 0.84, P < 0.001), the lower limit correlated weakly with autoregulatory area (r = 0.34, P = 0.012), and not at all with autoregulatory pattern or %CBFCPP60.

Conclusions

The %CBFCPP60 measures an aspect of the autoregulatory curve that is distinct from the lower limit. The peak autoregulatory pattern indicates that vessels are dilating more than is necessary to maintain a plateau in response to the pressure decrease, whereas the none pattern existed in spite of acceptable vascular responses to inhaled carbon dioxide and superfused ADP or ACh and the lack of surgical trauma. These results provide a different view of autoregulation during hypotension, are most likely dependent on the highly regional CBF method used, and could have implications concerning potential cerebral ischemia and hypotension during anesthesia.
A Comparison of the 24-Gauge Sprotte®and Gertie Marx®Spinal Needles for Combined Spinal-Epidural Analgesia during Labor
Authors: Riley Edward T. , Hamilton Catherine L. , Ratner Emily F. , Cohen Sheila E.
Published: November 2003

Background

Prior experience with the combined spinal-epidural technique (CSE) for labor analgesia demonstrated a high (up to 14%) failure rate because of failure to obtain cerebrospinal fluid (CSF) or lack of response to appropriate doses of intrathecal sufentanil. The current study was designed to test whether a longer needle with a shorter side port (Gertie Marx needle; 127 mm long) would eliminate failures to obtain CSF compared with the needle we had used previously (Sprotte needle; 120 mm long).

Methods

Seventy-three parturients were randomly assigned to have a CSE performed with one of these two needles. After identifying the epidural space with an 18-gauge Touhy needle at the L2-L3 or L3-L4 interspace, the spinal needle was introduced through the Touhy needle until penetration of the dura was felt or until the needle was maximally inserted. If no CSF was obtained, the alternate needle was tried. After obtaining CSF, 10 microg sufentanil diluted in 1.8 ml saline was injected. Verbal pain scores (0-10) were obtained every 5 min for 30 min.

Results

Failure to obtain CSF occurred six times in the Sprotte group compared with none in the Gertie Marx group (P < 0.05). In all six failures in the Sprotte group, the Gertie Marx needle subsequently proved successful in obtaining CSF. There were no differences in pain scores between the groups.

Conclusions

The extra length of the 127-mm Gertie Marx needle resulted in a higher success rate for obtaining CSF when used in the CSE technique. Side port design was not a factor influencing success in this clinical setting.
Comparing Clinical Productivity of Anesthesiology Groups
Authors: Abouleish Amr E. , Prough Donald S. , Whitten Charles W. , Zornow Mark H. , Lockhart Asa , Conlay Lydia A. , Abate James J.
Published: November 2003

Background

Intergroup comparisons of clinical productivity are important for strategic planning and evaluation of clinical and business operations. However, in a preliminary study, comparisons of two anesthesiology groups using "per full-time equivalent" measurements were confounded by different concurrencies or staffing ratios, whereas measurements based on "per operating room (OR) site," "per case," and "billed American Society of Anesthesiologists (ASA) units per hour of care" permitted meaningful comparisons despite differing concurrencies. The purpose of this study was to determine whether these measurements would allow for meaningful comparisons when applied to multiple groups.

Methods

Annual totals of total ASA units (tASA), 15-min time units, and the number of cases billed, as well as the average number of daily anesthetizing sites (OR sites) staffed and the average number of anesthesiologists required to the staff sites, were collected from each group that participated. All anesthesia care billed with ASA units was included, except for obstetric care. Any clinical service not billed using ASA units was excluded. Productivity measurements (concurrency, tASA/OR site, hours billed per OR site per day, hours billed per case, tASA billed per hour of anesthesia care, and base units per case) were calculated. Median and range for all groups and for private-practice and academic groups were determined.

Results

Eleven private-practice and nine academic groups from 12 states participated in the study. Productivity measurements that are influenced by duration of surgery (hours billed per case, tASA billed per hour of anesthesia care) differed significantly between groups, with private-practice groups having shorter duration than academic groups (median hours billed per case, 1.5 2.6, respectively). Although tASA/OR site measurements were similar in private-practice and academic groups, academic groups worked significantly longer hours billed per OR site per day (median, 6.0 h 7.8, respectively) to achieve the same level of tASA/OR site. Hourly billing productivity (tASA billed per hour of anesthesia care) correlated highly with surgical duration (hours billed per case).

Conclusion

This study demonstrates a method of comparing departmental clinical productivity between anesthesiology groups. Private-practice groups provided care for cases of shorter duration than academic groups. This difference was evident in several productivity measurements.
Mivacurium Arteriovenous Gradient during Steady State Infusion in Anesthetized Patients
Authors: Ezzine Samia , Donati François , Varin France
Published: November 2003

Background

Mivacurium and isomers undergo rapid hydrolysis by plasma cholinesterase. As this enzyme is largely distributed, it cannot be excluded that these isomers might undergo peripheral elimination. This hypothesis was investigated in patients by measuring the difference between arterial and venous concentrations under a constant-rate continuous infusion of mivacurium.

Methods

During propofol-remifentanil anesthesia, eight adult consenting patients received an intravenous bolus dose of 0.2 mg/kg mivacurium, followed by a constant infusion (3, 5, or 7 microg. kg. min ) into the brachial vein. One hour after starting the infusion, arterial (radial artery) and venous (contralateral brachial vein) blood samples were drawn simultaneously at 15-min intervals for 45 min. Mivacurium isomers and metabolite plasma concentrations were determined by stereospecific high-performance liquid chromatography. Using the corresponding arterial and venous concentrations, the tissue extraction coefficient as well as total body clearance were calculated.

Results

During steady state conditions, the venous concentrations of the and isomers were 34 +/- 13% and 42 +/- 11% (mean +/- SD) lower than the corresponding arterial concentrations (P < 0.05), respectively. For the isomer, the difference between venous and arterial concentrations was 3 +/- 4% (P = 0.063). Total body clearances of the and isomers were greater when based on venous sampling (P < 0.05).

Conclusion

Pharmacokinetic parameters derived from a constant infusion of mivacurium depend heavily on the sampling site (arterial or venous) for the rapidly hydrolyzed isomers. These results strongly suggest a significant metabolism of mivacurium within muscle tissue that may account for the large interpatient variability in response to mivacurium.
Intestinal and Cerebral Oxygenation during Severe Isovolemic Hemodilution and Subsequent Hyperoxic Ventilation in a Pig Model
Authors: van Bommel Jasper , Trouwborst Adrianus , Schwarte Lothar , Siegemund Martin , Ince Can , Henny Ch. Pieter
Published: November 2003

Background

During severe isovolemic hemodilution, determination of critical hematocrit levels for the microvascular oxygenation of different organs might provide more insight into the effect of the redistribution of blood flow and oxygen delivery on the oxygenation of different organs. The effect of an increased amount of dissolved oxygen on tissue oxygenation during severely decreased hematocrit levels is not clear.

Methods

Fifteen anesthetized pigs were randomized between an experimental group (n = 10), in which severe isovolemic hemodilution was performed with 6% hydroxyethylstarch (1:1), and a time-matched control group (n = 5). Systemic, intestinal, and cerebral hemodynamic and oxygenation parameters were monitored. Microvascular oxygen partial pressure (muPo(2) ) was measured in the cerebral cortex and the intestinal serosa and mucosa, using the oxygen-dependent quenching of Pd-porphyrin phosphorescence. In the final phase of the experiment, fraction of inspired oxygen was increased to 1.0.

Results

Hemodilution decreased hematocrit from 25.3 +/- 3.0 to 7.6 +/- 1.2% (mean +/- SD). Systemic and intestinal oxygen delivery fell with the onset of hemodilution; intestinal oxygen consumption deceased at a hematocrit of 9.9%, whereas the systemic oxygen consumption decreased at a hematocrit of 7.6%. During hemodilution, the intestinal and cerebral oxygen extraction ratios increased from baseline with 130 and 52%, respectively. Based on the intersection of the two best-fit regression lines, determined by a least sum of squares technique, similar critical hematocrit levels were found for systemic oxygen consumption and the cerebral and intestinal mucosa muPo(2); the intestinal serosa muPo(2) decreased at an earlier stage (P < 0.05). Hyperoxic ventilation improved the muPo(2) values but not systemic or intestinal oxygen consumption.

Conclusions

During isovolemic hemodilution, the diminished oxygen supply was redistributed in favor of organs with a lower capacity to increase oxygen extraction. It is hypothesized that redirection of the oxygen supply within the intestines resulted in the preservation of oxygen consumption and mucosal muPo(2) compared with serosal muPo(2).
Set Positive End-expiratory Pressure during Protective Ventilation Affects Lung Injury
Authors: Takeuchi Muneyuki , Goddon Sven , Dolhnikoff Marisa , Shimaoka Motomu , Hess Dean , Amato Marcelo B. P. , Kacmarek Robert M.
Published: November 2003

Background

The most appropriate method of determining positive end-expiratory pressure (PEEP) level during a lung protective ventilatory strategy has not been established.

Methods

In a lavage-injured sheep acute respiratory distress syndrome model, the authors compared the effects of three approaches to determining PEEP level after a recruitment maneuver: (1) 2 cm H(2)O above the lower inflection point on the inflation pressure-volume curve, (2) at the point of maximum curvature on the deflation pressure-volume curve, and (3) at the PEEP level that maintained target arterial oxygen partial pressure at a fraction of inspired oxygen of 0.5.

Results

Positive end-expiratory pressure set 2 cm H(2)O above the lower inflection point resulted in the least injury over the course of the study. PEEP based on adequate arterial oxygen partial pressure/fraction of inspired oxygen ratios had to be increased over time and resulted in higher mRNA levels for interleukin-8 and interleukin-1beta and greater tissue inflammation when compared with the other approaches. PEEP at the point of maximum curvature could not maintain eucapneia even at an increased ventilatory rate.

Conclusion

Although generating higher plateau pressures, PEEP levels based on pressure-volume curve analysis were more effective in maintaining gas exchange and minimizing injury than PEEP based on adequate oxygenation. PEEP at 2 cm H(2)O above the lower inflection point was most effective.
Lateral Position Decreases Collapsibility of the Passive Pharynx in Patients with Obstructive Sleep Apnea
Authors: Isono Shiroh , Tanaka Atsuko , Nishino Takashi
Published: November 2003

Background

Reduction of nocturnal obstructive events during lateral position in patients with obstructive sleep apnea was previously reported. However, little information is available regarding mechanisms of the improvement and the precise pharyngeal site influenced by the lateral position. The authors tested the hypothesis that structural properties of the passive pharynx change by changing the body position from supine to lateral.

Method

Total muscle paralysis was induced with general anesthesia in eight patients with obstructive sleep apnea, eliminating neuromuscular factors contributing to pharyngeal patency. The cross-sectional area of the pharynx was measured endoscopically at different static airway pressures. Comparison of static pressure-area plot between the positions allowed assessment of the influence of the position change on the mechanical properties of the pharynx.

Results

The static pressure-area curves of the lateral position were above those of the supine position, with increasing maximum cross-sectional area and decreasing the closing pressure at both retropalatal and retroglossal airways.

Conclusions

Lateral position structurally improves maintenance of the passive pharyngeal airway in patients with obstructive sleep apnea.
Cortisol Response to Corticotropin Stimulation in Trauma Patients
Authors: Hoen Sophie , Asehnoune Karim , Brailly-Tabard Sylvie , Mazoit Jean-Xavier , Benhamou Dan , Moine Pierre , Edouard Alain R.
Published: November 2003

Background

An abnormal adrenocortical function and a vasopressor dependency have been demonstrated during septic shock. Because trauma and hemorrhage are the leading causes of noninfectious inflammatory syndromes, the goal of this study was to assess the adrenal reserve of trauma patients and its relation with clinical course.

Methods

Cortisol response to an intravenous corticotropin bolus was obtained in 34 young trauma patients (Injury Severity Score =29.1 +/- 7.3) at the end of the resuscitative period ("early phase") and at the end of the first posttraumatic week ("late period"). Cortisol response less than +9 g/dl defined an impaired adrenal function, and the corresponding patient was called a nonresponder. According to the early response, hemorrhagic shock, circulating interleukin-6, need for vasopressor therapy, subsequent organ dysfunction and infection, and outcomes were studied.

Results

Sixteen patients (47%) were nonresponders at the end of the early phase. Hemorrhagic shock was more frequent (69 vs. 28%; = 0.037) and interleukin-6 concentrations were higher (728 +/- 589 vs. 311 +/- 466 pg/ml; = 0.048) in these patients. The early cortisol responses were negatively correlated with the concomitant interleukin-6 serum concentrations (r(2) = 0.298; = 0.003). Four early nonresponders (and shock patients) remained nonresponders during the late phase (25%). Morbidity and mortality were similar in early nonresponders and responders. The duration of norepinephrine treatment and the total amount of infused drug were significantly higher in early nonresponders.

Conclusions

A sustained impairment of adrenal reserve is frequently observed in trauma patients. This abnormal cortisol response to corticotropin stimulation is related with the inflammatory consequences of hemorrhagic shock and is followed by a prolonged vasopressor dependency.
Goal-directed Intraoperative Fluid Administration Reduces Length of Hospital Stay after Major Surgery
Authors: Gan Tong J. , Soppitt Andrew , Maroof Mohamed , El-Moalem Habib , Robertson Kerri M. , Moretti Eugene , Dwane Peter , Glass Peter S. A.
Published: November 2003

Background

Intraoperative hypovolemia is common and is a potential cause of organ dysfunction, increased postoperative morbidity, length of hospital stay, and death. The objective of this prospective, randomized study was to assess the effect of goal-directed intraoperative fluid administration on length of postoperative hospital stay.

Methods

One hundred patients who were to undergo major elective surgery with an anticipated blood loss greater than 500 ml were randomly assigned to a control group (n = 50) that received standard intraoperative care or to a protocol group (n = 50) that, in addition, received intraoperative plasma volume expansion guided by the esophageal Doppler monitor to maintain maximal stroke volume. Length of postoperative hospital stay and postoperative surgical morbidity were assessed.

Results

Groups were similar with respect to demographics, surgical procedures, and baseline hemodynamic variables. The protocol group had a significantly higher stroke volume and cardiac output at the end of surgery compared with the control group. Patients in the protocol group had a shorter duration of hospital stay compared with the control group: 5 +/- 3 versus 7 +/- 3 days (mean +/- SD), with a median of 6 versus 7 days, respectively ( = 0.03). These patients also tolerated oral intake of solid food earlier than the control group: 3 +/- 0.5 versus 4.7 +/- 0.5 days (mean +/- SD), with a median of 3 versus 5 days, respectively ( = 0.01).

Conclusions

Goal-directed intraoperative fluid administration results in earlier return to bowel function, lower incidence of postoperative nausea and vomiting, and decrease in length of postoperative hospital stay.
Heteromeric Nicotinic Inhibition by Isoflurane Does Not Mediate MAC or Loss of Righting Reflex
Authors: Flood Pamela , Sonner James M. , Gong Diane , Coates Kristen M.
Published: November 2003

Background

Neuronal nicotinic acetylcholine receptors (nAChRs) have been implicated in the mechanism of action of isoflurane as they are inhibited at subanesthetic concentrations. Despite clear evidence for nicotinic inhibition at relevant isoflurane concentrations, it is unclear what behavioral result ensues, if any.

Methods

The authors have modeled two behaviors common to all general anesthetics, immobility and hypnosis, as minimum alveolar concentration that prevents movement in response to a supramaximal stimulus (MAC) and loss of righting reflex (LORR). They have tested the ability of nicotinic pharmacologic modulators and congenital absence of most heteromeric nAChRs to affect concentration of isoflurane required for these behaviors.

Results

Neither mecamylamine, 5 mg/kg, nor chlorisondamine, 10 mg/kg, affected isoflurane MAC. Nicotine caused a small decrease in MAC. None of the above agents had any effect on the concentration of isoflurane required for LORR. Mice genetically engineered to lack the beta 2 nicotinic gene product were not different in MAC or LORR from controls.

Conclusions

Nicotinic antagonists do not cause MAC or LORR. Inhibition of nicotinic acetylcholine receptors by isoflurane is not likely related to its ability to provide immobility and hypnosis in a surgical setting. This is perhaps not surprising as the inhibition of nAChRs in vitro is complete at an isoflurane concentration equal to one half of MAC. Nicotinic inhibition may, however, be involved in anesthetic behaviors such as amnesia and analgesia, which occur at lower anesthetic concentrations.
Sleep Deprivation Potentiates the Onset and Duration of Loss of Righting Reflex Induced by Propofol and Isoflurane
Authors: Tung Avery , Szafran Martin J. , Bluhm Bryan , Mendelson Wallace B.
Published: November 2003

Background

Sleep and anesthesia differ physiologically but produce a similar loss of responsiveness to environmental stimuli. Recent data suggest that neuronal networks active in naturally occurring sleep also play a role in the anesthetized state. Changes in the propensity to sleep may then modify the response to anesthetic agents. The authors tested the hypothesis that sleep-deprived rats would require less anesthetic than rested rats to achieve a similar loss of responsiveness.

Methods

Rats were subjected to a 24-h period of either sleep deprivation or ad libitum activity. Sleep deprivation was produced by placing rats on a disk that rotated when sleep was detected by electroencephalographic and electromyographic (EEG, EMG) monitoring. A fixed dose of anesthetic agent was then administered, and the time required to induce loss of righting reflex was measured. Anesthetic administration was then stopped, and the time to recovery measured. All rats received both treatments separated by 7 days.

Results

Sleep deprivation reduced the time to loss of righting reflex by 40% for propofol (P < 0.025) and 55% for isoflurane (P < 0.025) and prolonged the time to recovery. In a separate control experiment, exposure to the deprivation environment but with disk rotation modified to allow adequate sleep did not affect the response to anesthetic administration.

Conclusions

Sleep deprivation significantly potentiated the ability of inhaled and intravenous anesthetic agents to induce a loss of righting reflex. These results support the hypothesis that neuronal networks active in sleep are also involved in the anesthetized state and suggest that sleep deprivation may partly explain the variability in patient response to anesthesia.
Sevoflurane Preconditioning before Moderate Hypothermic Ischemia Protects against Cytosolic [Ca2+] Loading and Myocardial Damage in Part via Mitochondrial KATPChannels
Authors: Chen Qun , Camara Amadou K. S. , An Jianzhong , Novalija Enis , Riess Matthias L. , Stowe David F.
Published: November 2003

Background

Brief sevoflurane exposure and washout (sevoflurane preconditioning [SPC]) before 30-min global ischemia at 37 degrees C is known to improve cardiac function, decrease cytosolic [Ca(2+)] loading, and reduce infarct size on reperfusion. It is not known if anesthetic preconditioning (APC) applies as well to hypothermic ischemia and reperfusion and if K(ATP) channels are involved. The authors examined in guinea pig isolated hearts the effect of sevoflurane exposure before 4-h global ischemia at 17 degrees C on cardiac function, cytosolic [Ca(2+)] loading, and infarct size. In addition they tested the potential role of the mitochondrial K(ATP) channel in eliciting the cardioprotection by SPC.

Methods

Hearts were randomly assigned to (1) a nontreated hypothermic ischemia group (CON), (2) a group given 3.5 vol% sevoflurane for 15 min with a 15-min washout before hypothermic ischemia (SPC), and (3) an SPC group in which anesthetic exposure was bracketed with 200 microm 5-hydroxydecanoate (5-HD) from 5 min before until 5 min after sevoflurane (SPC + 5-HD). Cytosolic [Ca(2+)] was measured in the left ventricular (LV) free wall with the intracellularly loaded fluorescence probe indo-1.

Results

Initial reperfusion in CON hearts markedly increased systolic and diastolic [Ca(2+)] and reduced contractility (dLVP/dt(max)), relaxation (diastolic LVP, dLVP/dt(min)), myocardial oxygen consumption (MvO(2)), and cardiac efficiency. In SPC hearts, cytosolic [Ca(2+)] overloading (especially diastolic [Ca(2+)]) was decreased with increased myocardial [Ca(2+)] influx (d[Ca(2+)]/dt(max)) and efflux (d[Ca(2+)]/dt(min)), improved contractility, relaxation, coronary flow, MvO(2), cardiac efficiency, and decreased infarct size. In SPC + 5HD hearts, the reduction in infarct size was antagonized by 5-HD, but functional return was less affected by 5-HD.

Conclusions

Anesthetic preconditioning occurs after long-term hypothermic ischemia, and the infarct size reduction is the result, in part, of mitochondrial K(ATP) channel opening.
Postoperative Wound Oxygen Tension with Epidural or Intravenous Analgesia
Authors: Buggy Donal J. , Doherty Warren L. , Hart Elaine M. , Pallett Edward J.
Published: November 2003

Background

Adequate tissue oxygen tension is an essential requirement for surgical-wound healing. The authors tested the hypothesis that epidural anesthesia and analgesia increases wound tissue oxygen tension compared with intravenous morphine analgesia.

Methods

In a prospective, randomized, blind clinical study, the authors allocated patients having major abdominal surgery (n = 32) to receive combined general and epidural anesthesia with postoperative patient-controlled epidural analgesia (epidural group, n = 16), or general anesthesia alone with postoperative patient-controlled intravenous analgesia (intravenous group, n = 16). An oxygen sensor and a temperature sensor were placed subcutaneously in the wound before closure. Wound oxygen tension (P(w)O(2)) and temperature were measured continuously for 24 h. Other variables affecting wound tissue oxygenation and visual analogue scale (VAS) pain scores were also documented.

Results

Despite epidural patients having lower body temperatures at the end of surgery (35.7 +/- 0.3) versus 36.3 +/- 0.5 degrees C, = 0.004), they had significantly higher mean P(w)O(2) over the 24 h period, compared with the intravenous group (64.4 +/- 14 vs. 50.7 +/- 15) mmHg, mean (SD), 95% CI difference, -22 to -5, = 0.002). Area under the P(w)O(2) -24 h time curve was also significantly higher in the epidural group (930 +/- 278 vs. 749 +/- 257) mmHg x h, 95% CI difference -344 to -18, = 0.03). VAS pain scores at rest and moving were significantly lower in the epidural group at all times.

Conclusion

Epidural anesthesia and postoperative analgesia for major abdominal surgery increases wound tissue oxygen tension compared with general anesthesia and intravenous morphine analgesia.