bluuebunny/crossref_metadata_2025 huggingface dataset:
Perioperative Myocardial Ischemia and Infarction
Authors: Landesberg Giora , Mosseri Morris , Wolf Yehuda , Vesselov Yellena , Weissman Charles
Published: November 2003

Background

Perioperative myocardial ischemia is conventionally monitored using five electrocardiographic leads, with only one precordial lead placed at V5. This is based on studies from more than a decade ago. The authors reassessed this convention by analyzing data obtained from continuous on-line 12-lead electrocardiographic monitoring.

Methods

One hundred eighty-five consecutive patients undergoing vascular surgery were monitored by continuous 12-lead ST-trend analysis during and for 48-72 h after surgery. Cardiac troponin I was measured in the first 3 postoperative days, and cardiac outcome was prospectively recorded. Ischemia was defined as ST deviation, relative to the reference preanesthesia electrocardiogram, of 0.2 mV or more in one lead or 0.1 mV or more in two contiguous leads, lasting more than 10 min.

Results

During 11,132 patient-hours of monitoring, 38 patients (20.5%) had 66 transient ischemic events, with all but one denoted by ST-segment depression. Twelve patients (6.5%) sustained postoperative infarction (cardiac troponin I > 3.1 ng/ml). Among the 38 patients with ischemia, lead V3 most frequently (86.8%) demonstrated ischemia, followed by V4 (78.9%) and V5 (65.8%). Among the 12 patients with infarction, V4 was most sensitive to ischemia (83.3%), followed by V3 and V5 (75% each). Combining two precordial leads increased the sensitivity for detecting ischemia (97.4% for V3 + V5 and 92.1% for either V4 + V5 or V3 + V4) and infarction (100% for V4 + V5 or V3 + V5 and 83.3% for V3 + V4). On average, baseline preanesthesia ST was above isoelectric in V1 through V3 and below isoelectric in V5 through V6. Lead V4 was closest to the isoelectric level on the baseline electrocardiogram, rendering it most suitable for ischemia monitoring.

Conclusions

As a single lead, V4 is more sensitive and appropriate than V5 for detecting prolonged postoperative ischemia and infarction. Two precordial leads or more are necessary so as to approach a sensitivity of greater than 95% for detection of perioperative ischemia and infarction.
Involvement of Renin–Angiotensin System in Pressure–Flow Relationship
Authors: Lasocki Sigismond , Iglarz Marc , Seince Pierre-François , Vuillaumier-Barrot Sandrine , Vicaut Eric , Henrion Daniel , Levy Bernard , Desmonts Jean-Marie , Philip Ivan , Bénessiano Joelle
Published: November 2003

Background

The renin-angiotensin system is involved in blood pressure regulation. The insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene is known to be associated with variation of plasma and cellular ACE concentrations. Furthermore, changes in arterial function have been suggested to be associated to the DD genotype. The aim of the study was to investigate the arterial vascular response to a physiologic stimulus (i.e., flow) according to the I/D ACE gene polymorphism.

Methods

Sixty patients scheduled for coronary artery bypass grafting (n = 24) or valve surgery (n = 36) under normothermic cardiopulmonary bypass were genotyped in a blind manner by polymerase chain reaction. Mean arterial pressure was measured at pump flows ranging from 1 to 3 l x min(-1) x m (-2) by 0.25 l x min(-1) x m(-2) step each 15 s, to obtain a pressure-flow relation. Independent factors associated with the variation of the slope of the pressure-flow relation curve were assessed by multivariate analysis.

Results

We found a D allelic frequency of 0.54. Patients were separated in two groups (DD, n = 16; ID/II, n = 44). There were no significant difference with regard to preoperative and intraoperative data between the two groups. DD patients had their pressure-flow relation curves shifted upward (with higher pressures as flow increased), indicating a lesser decrease in vascular resistance. Furthermore, DD genotype was the only independent predictor of the slope of the curves (21.5 +/- 4.2 vs. 18.1 +/- 5 mmHg/[l x min(-1) x m(-2)] for DD and ID/II, respectively; P = 0.02; values are mean +/-SD).

Conclusion

These results show that vasomotor properties are influenced by the I/D polymorphism of the ACE gene.
Flexible Lightwand–guided Tracheal Intubation with the Intubating Laryngeal Mask Fastrach TMin Adults after Unpredicted Failed Laryngoscope-guided Tracheal Intubation
Authors: Dimitriou Vasilios , Voyagis Gregory S. , Brimacombe Joseph R.
Published: November 2003

Background

The authors determined the efficacy of using the intubating laryngeal mask airway Fastrach (ILM) as a ventilatory device and aid to flexible lightwand-guided tracheal intubation in patients with unpredicted failed laryngoscope-guided tracheal intubation when managed by experienced anesthetists.

Methods

During a 27-month period, 16 experienced anesthetists agreed to use the ILM as an airway device and airway intubator in patients (aged > 18 yr) with predicted normal airways who were subsequently found to be difficult to intubate (three failed attempts at laryngoscopy). Intubation via the ILM was performed with a flexible lightwand. The number of attempts at ILM placement, the number of adjusting maneuvers, the number of attempts at tracheal intubation via the ILM,and any episodes of hypoxia (oxygen saturation < 90%) were recorded.

Results

Forty-four of 11,621 patients (0.4%) met the inclusion criteria. ILM insertion and ventilation was successful at the first attempt in 40 of 44 patients (91%) and at the second attempt in 4 of 44 (9%). Flexible lightwand-guided tracheal intubation via the ILM was successful in 38 of 44 patients (86%) at the first attempt, 3 of 44 (7%) at the second attempt, 2 of 44 (5%) at the third to fifth attempts, and failed in 1 of 44 (2%). The median number of adjusting maneuvers before successful intubation was 1 (range, 0-4). Hypoxia occurred in 5 patients before ILM insertion (range, 52-82%), but none after ILM insertion. No patient developed hypoxia during or after intubation via the ILM.

Conclusion

The ILM is an effective ventilatory device and aid to flexible lightwand-guided tracheal intubation in adult patients with predicted normal airways in whom laryngoscope-guided tracheal intubation subsequently fails when managed by experienced anesthetists.
Transcutaneous Electrical Stimulation of an Auricular Acupuncture Point Decreases Anesthetic Requirement
Authors: Greif Robert , Laciny Sonja , Mokhtarani Masoud , Doufas Anthony G. , Bakhshandeh Maryam , Dorfer Leopold , Sessler Daniel I.
Published: November 2003

Background

German anesthesiologists have long used transcutaneous electrical stimulation of an acupuncture point near the tragus to reduce anesthetic requirement in unblinded and uncontrolled trials. This is known as auricular electrically stimulated analgesia. The authors therefore tested the hypothesis that auricular electrically stimulated analgesia reduces anesthetic requirement.

Methods

In a randomized, double-blind, crossover trial, volunteers were anesthetized twice with desflurane. Electrical stimulation of an auricular acupuncture point in the vicinity of the tragus was used on 1 randomly assigned day, and no electrical stimulation of the same point was used on the other study day. Treatment consisted of bilateral electrical stimulation of the lateralization control point, 3 cm anterior to the tragus. The 10-mA current was set to 299 Hz on the dominant side of the face and to 149 Hz on the contralateral side. Anesthetic requirement was determined by the Dixon up-and-down method and was defined by the average desflurane concentration required to prevent purposeful movement of the extremities in response to noxious electrical stimulation.

Results

Ten men and 10 women completed the protocol. Electrical stimulation of the lateralization control point reduced anesthetic requirement by 11 +/- 7% (P < 0.001), with the reduction being similar in women and men. Women required more desflurane to prevent movement on the control day than the men (5.5 +/- 1.0 vs. 4.6 +/- 0.6 vol%; P = 0.028).

Conclusion

This double-blinded trial with an objective outcome demonstrates that electrical stimulation of the lateralization control point significantly reduces anesthetic requirement.
Neuromuscular Junctions in Cerebral Palsy
Authors: Theroux Mary C. , Akins Robert E. , Barone Carol , Boyce Bobbie , Miller Freeman , Dabney Kirk W.
Published: November 2003

Background

Cerebral palsy (CP) is the most prevalent neurologic disease in children. A primary deficit in CP is neuromuscular dysfunction; however, neuromuscular junctions in children with CP have not been studied. Evidence exists that up-regulation of acetylcholine receptors (AChRs) may be present in children with CP, and the current study was undertaken to examine this possibility.

Methods

Thirty-nine children with spastic CP and 25 neurologically normal children were enrolled in the study. Paraspinal muscles underwent biopsy during scheduled spinal fusion surgery. Two sets of assessments were performed on the biopsy specimens: (1) reverse-transcription polymerase chain reaction and Western blotting to evaluate the expression of the gamma subunit of the AChR; and (2) histologic evaluation using a double-stain technique for AChR and acetylcholinesterase, wherein acetylcholinesterase staining defined the limits of the neuromuscular junction, and AChR staining that appeared outside of these limits indicated an abnormal distribution of AChRs.

Results

Reverse-transcription polymerase chain reaction and Western blot analyses showed that neither the CP nor non-CP samples had detectable gamma-AChR subunit. Histologic analysis indicated that 11 of 39 children with CP and none of 20 children with idiopathic scoliosis scored positive for the presence of AChR outside of the neuromuscular junction (P = 0.0085).

Conclusion

A subset of children with CP have an abnormal distribution of AChR relative to the acetylcholinesterase found at the neuromuscular junction. The altered distribution of AChR in CP was not associated with a detectable presence of the gamma-AChR subunit, suggesting that the nonjunctional AChRs in CP does not contain the gamma subunit.
Role of Endogenous Histamine in Altered Lung Mechanics in Rabbits
Authors: Habre Walid , Babik Barna , Chalier Michel , Peták Ferenc
Published: November 2003

Background

Unlike the effects of exogenous histamine, those of endogenous histamine on the lung mechanics have not yet been characterized. The site of endogenous histamine liberation by mivacurium was determined, as were the effects of this histamine on the airway and parenchymal mechanics in control rabbits (group C) and rabbits pretreated with H1 and H2 receptor blockers (group AH). The effectiveness of the receptor blockade was ensured by challenges with exogenous histamine.

Methods

Pulmonary input impedance at low frequencies (ZL) was measured in anesthetized mechanically ventilated open-chest rabbits under control conditions and every minute after administration of an intravenous bolus of mivacurium (2 mg/kg) and exogenous histamine (10 microg/kg). Histamine levels were determined in serum samples taken from the carotid artery and jugular vein before and 1, 3, and 6 min after mivacurium injection. Parameters of airway resistance (Raw) and inertance and parenchymal damping (G) and elastance (H) were extracted from ZL spectra.

Results

Mivacurium induced significant increases in plasma histamine levels, with the venous concentrations being significantly higher than those in the artery. The mivacurium-induced increase in Raw (28.7 +/- 2.3%; mean +/- SD) in group C was significantly higher than that in group AH (6.6 +/- 3.4%), whereas the responses in G were not inhibited significantly (23.9 +/- 6.9% vs. 15.5 +/- 3.0%). The significant increases in Raw (70.6 +/- 12.6%) and G (21.0 +/- 4.9%) after exogenous histamine administration were virtually completely abolished by antihistamine pretreatment (3.6 +/- 3.7% and 0.3 +/- 2.6%).

Conclusions

After mivacurium administration, endogenous histamine is liberated at least partly in the systemic circulation, and it induces primarily a heterogeneous airway constriction with minor changes in the parenchymal properties. This response was considerably reduced but not abolished by antihistamine pretreatment, a circumstance suggesting that mivacurium may liberate other constrictor mediators that might also contribute to the airway and parenchymal constriction.
Isoflurane Depresses Baroreflex Control of Heart Rate in Decerebrate Rats
Authors: Lee Jong S. , Morrow Don , Andresen Michael C. , Chang Kyoung S. K.
Published: November 2003

Background

Isoflurane inhibits baroreflex control of heart rate (HR) by poorly understood mechanisms. The authors examined whether suprapontine central nervous system cardiovascular regulatory sites are required for anesthetic depression.

Methods

The effects of isoflurane (1 and 2 rat minimum alveolar concentration [MAC]) on the baroreflex control of HR were determined in sham intact and midcollicular-transected decerebrate rats. Intravenous phenylephrine (0.2-12 microg/kg) and nitroprusside (1-60 microg/kg) were used to measure HR responses to peak changes in mean arterial pressure (MAP). Sigmoidal logistic curve fits to HR-MAP data assessed baroreflex sensitivity (HR/MAP), HR range, lower and upper HR plateau, and MAP at half the HR range (BP50). Four groups (two brain intact and two decerebrate) were studied before, during, and after isoflurane. To assess sympathetic and vagal contributions to HR baroreflex, beta-adrenoceptor (1 mg/kg atenolol) or muscarinic (0.5 mg/kg methyl atropine) antagonists were administered systemically.

Results

Decerebration did not alter resting MAP and HR or baroreflex parameters. Isoflurane depressed baroreflex slope and HR range in brain-intact and decerebrate rats. In both groups, 1 MAC reduced HR range by depressing peak reflex tachycardia. Maximal reflex bradycardia during increases in blood pressure was relatively preserved. Atenolol during 1 MAC did not alter maximum reflex tachycardia. In contrast, atropine during 1 MAC fully blocked reflex bradycardia. Therefore, 1 MAC predominantly depresses sympathetic components of HR baroreflex. Isoflurane at 2 MAC depressed both HR plateaus and decreased BP50 in both groups.

Conclusions

Isoflurane depresses HR baroreflex control by actions that do not require suprapontine central nervous system sites. Isoflurane actions seem to inhibit HR baroreflex primarily by the sympathetic nervous system.
Patient-controlled Regional Analgesia (PCRA) at Home
Authors: Rawal Narinder , Allvin Renée , Axelsson Kjell , Hallén Jan , Ekbäck Gustav , Ohlsson Torbjörn , Amilon Anders
Published: November 2003

Background

The aim of this randomized, double-blinded study was to compare the analgesic efficacy of bupivacaine versus ropivacaine brachial plexus analgesia after ambulatory hand surgery. An additional aim was to study the feasibility and safety of patient-controlled regional analgesia (PCRA) outside the hospital.

Methods

Sixty patients scheduled for ambulatory hand surgery underwent surgery with axillary plexus blockade. After surgery, the plexus catheter was connected to an elastomeric, disposable "homepump," containing 100 ml of either 0.125% bupivacaine or 0.125% ropivacaine. When patients experienced pain, they self-administered 10 ml of the study drug. Analgesic efficacy of PCRA was evaluated by self-assessment of pain intensity by visual analog scale (VAS) and verbal scale. Patients recorded adverse effects, technical problems, use of rescue analgesic tablets, and overall satisfaction. A follow-up telephone call was made the day after surgery.

Results

Visual analog scale scores decreased after each treatment in both groups, but there were no significant differences between the two drugs. One patient in each group took rescue dextropropoxyphene tablets. In both groups, 87% patients expressed their desire to have the same treatment again. On the day of surgery, significantly more patients were satisfied with ropivacaine PCRA. None of the patients had any signs or symptoms of local anesthetic toxicity or catheter infection.

Conclusions

This double-blinded study has demonstrated the feasibility of self-administration of local anesthetic to manage postoperative pain outside the hospital. Ropivacaine and bupivacaine provided effective analgesia, and patient satisfaction with PCRA was high. Patient selection, follow-up telephone call, and 24-h access to anesthesiology services are prerequisites for PCRA at home.
Dexamethasone Prolongs Local Analgesia after Subcutaneous Infiltration of Bupivacaine Microcapsules in Human Volunteers
Authors: Holte Kathrine , Werner Mads U. , Lacouture Peter G. , Kehlet Henrik
Published: November 2003

Background

The addition of small amounts of dexamethasone to extended-release formulations of bupivacaine in microcapsules has been found to prolong local analgesia in experimental studies, but no clinical data are available.

Methods

In a double-blinded study, 12 healthy male volunteers were randomized to receive simultaneous subcutaneous injections of bupivacaine microcapsules with dexamethasone and bupivacaine microcapsules without dexamethasone in each calf. Local analgesia was assessed with a validated human pain model; main parameters evaluated were thermal, mechanical, and pain detection thresholds and suprathreshold responses to heat and mechanical stimulation. Measurements were performed every 2 h for the first 8 h and daily for the week after injection. Primary endpoints were evaluation of maximal analgesic effect, time of onset, and duration of analgesia. Summary measures (area under curve [AUC]) were considered best estimate of analgesia. Safety evaluations were performed daily for the first week and at 2 weeks, 6 weeks, and 6 months after injection.

Results

The addition of dexamethasone significantly prolonged local analgesia of bupivacaine microcapsules without influence on maximal analgesic effect. AUC in all thermal measurements and the sensory mechanical threshold were significantly increased between 1-7 days after drug injection in the group given dexamethasone compared with the group not given dexamethasone. No serious side effects were observed.

Conclusions

Addition of small amounts of dexamethasone to bupivacaine incorporated in microcapsules prolonged local analgesia compared with microcapsules with plain bupivacaine after subcutaneous administration in humans.
Dexamethasone in Combination with Dolasetron for Prophylaxis in the Ambulatory Setting
Authors: Coloma Margarita , White Paul F. , Markowitz Scott D. , Whitten Charles W. , Macaluso Amy R. , Berrisford Sally B. , Thornton Kevin C.
Published: November 2003

Background

Postoperative nausea and vomiting after laparoscopic cholecystectomy remains a common problem despite routine antiemetic prophylaxis. Therefore, the authors investigated the effect of administering 4 mg intravenous dexamethasone as an adjunct to a 5-HT3 antagonist (12.5 mg intravenous dolasetron) with respect to patient outcome.

Methods

Outpatients (N = 140) were enrolled in this prospective, randomized, placebo-controlled, double-blind, institutional review board-approved protocol involving two antiemetic treatment groups. After induction of anesthesia, the control group received 1 ml intravenous saline, whereas the dexamethasone group received 4 mg intravenous dexamethasone. Both groups received 12.5 mg intravenous dolasetron at the time of gallbladder removal. A blinded observer recorded the recovery times, emetic episodes, rescue antiemetics, maximum nausea score, and time to achieve discharge criteria. Postdischarge side effects, as well as patient satisfaction and quality of recovery scores were assessed at 24 h after surgery.

Results

Although there was no difference in the incidence of postoperative nausea and vomiting in the early recovery period, the dexamethasone group had a shorter stay in the day-surgery unit (136 +/- 57 vs. 179 +/- 62 min) and more rapidly achieved discharge criteria (161 +/- 32 vs. 209 +/- 39 min). In addition, fewer patients in the dexamethasone group experienced nausea at home within 24 h after discharge (13 vs. 28%, P < 0.05). Finally, the dexamethasone group reported higher quality of recovery and patient satisfaction scores (P < 0.05).

Conclusions

The authors conclude that the adjunctive use of 4 mg intravenous dexamethasone shortened the time to achieve discharge criteria and improved the quality of recovery and patient satisfaction scores after laparoscopic cholecystectomy procedures in outpatients receiving prophylaxis with 12.5 mg intravenous dolasetron.
Effects of Surgical Levels of Propofol and Sevoflurane Anesthesia on Cerebral Blood Flow in Healthy Subjects Studied with Positron Emission Tomography
Authors: Kaisti Kaike K. , Metsähonkala Liisa , Teräs Mika , Oikonen Vesa , Aalto Sargo , Jääskeläinen Satu , Hinkka Susanna , Scheinin Harry
Published: November 2003

Background

The authors report a positron emission tomography (PET) study on humans with parallel exploration of the dose-dependent effects of an intravenous (propofol) and a volatile (sevoflurane) anesthetic agent on regional cerebral blood flow (rCBF) using quantitative and relative (Statistical Parametric Mapping [SPM]) analysis.

Methods

Using H(2)(15)O, rCBF was assessed in 16 healthy (American Society of Anesthesiologists [ASA] physical status I) volunteers awake and at three escalating drug concentrations: 1, 1.5, and 2 MAC/EC(50), or specifically, at either 2, 3, and 4% end-tidal sevoflurane (n = 8), or 6, 9, and 12 microg/ml plasma concentration of propofol (n = 8). Rocuronium was used for muscle relaxation.

Results

Both drugs decreased the bispectral index and blood pressure dose-dependently. Comparison between adjacent levels showed that sevoflurane initially (0 vs. 1 MAC) reduced absolute rCBF by 36-53% in all areas, then (1 vs. 1.5 MAC) increased rCBF in the frontal cortex, thalamus, and cerebellum (7-16%), and finally (1.5 vs. 2 MAC) caused a dual effect with a 23% frontal reduction and a 38% cerebellar increase. In the propofol group, flow was also initially reduced by 62-70%, with minor further effects. In the SPM analysis of the "awake to 1 MAC/EC(50)" step, both anesthetic agents reduced relative rCBF in the cuneus, precuneus, posterior limbic system, and the thalamus or midbrain; additionally, propofol reduced relative rCBF in the parietal and frontal cortices.

Conclusions

Both anesthetic agents caused a global reduction of rCBF (propofol > sevoflurane) at the 1 MAC/EC(50) level. The effect was maintained at higher propofol concentrations, whereas 2 MAC sevoflurane caused noticeable flow redistribution. Despite the marked global changes, SPM analysis enabled detailed localization of regions with the greatest relative decreases.
Gastric Emptying of Water in Term Pregnancy
Authors: Wong Cynthia A. , Loffredi Mariann , Ganchiff Jeanne N. , Zhao Jia , Wang Zhao , Avram Michael J.
Published: November 2003

Background

Healthy nonpregnant patients may ingest clear liquids until 2 h before induction of anesthesia without adversely affecting gastric volume. The purpose of this study was to compare gastric emptying in term, nonlaboring pregnant women after ingestion of 50 ml water (control) with that after ingestion of 300 ml water.

Methods

Gastric emptying was assessed in healthy, nonobese, term pregnant volunteers using both serial gastric ultrasound examinations (n = 9) and acetaminophen absorption (n = 11) in a crossover study design. After an overnight fast, volunteers ingested 1.5 g acetaminophen and 50 or 300 ml water (assigned in random order) on two occasions separated by at least 2 days. Serial gastric antrum cross-sectional areas were determined using gastric ultrasound imaging, and the half-time to gastric emptying was calculated. Serial plasma acetaminophen concentrations were measured. Areas under the plasma acetaminophen concentration versus time curve, peak concentrations, and time to peak concentration for 50- and 300-ml ingestions were compared.

Results

Gastric emptying half-time was significantly shorter after ingestion of 300 ml water than after ingestion of 50 ml (24 +/- 6 vs. 33 +/- 8 min). There were no differences in acetaminophen areas under the curve at 60, 90, or 120 min, or in acetaminophen peak concentration. Time to peak concentration of acetaminophen was significantly shorter after ingestion of 300 ml water than after ingestion of 50 ml (25 +/- 12 vs. 41 +/- 19 min).

Conclusions

Gastric emptying in healthy, term, nonobese, nonlaboring pregnant women is not delayed after ingestion of 300 ml water compared with that after an overnight fast.
N -Phenylethyl Amitriptyline in Rat Sciatic Nerve Blockade
Authors: Gerner Peter , Mujtaba Mustafa , Khan Mohammed , Sudoh Yukari , Vlassakov Kamen , Anthony Douglas C. , Wang Ging Kuo
Published: November 2003

Background

The antidepressant amitriptyline is commonly used orally for the treatment of chronic pain, particularly neuropathic pain, which is thought to be caused by high-frequency ectopic discharge. Among its many properties, amitriptyline is a potent Na(+) channel blocker in vitro, has local anesthetic properties in vivo, and confers additional blockade at high stimulus-discharge rates (use-dependent blockade). As with other drug modifications, adding a phenylethyl group to obtain a permanently charged quaternary ammonium derivative may improve these advantageous properties.

Methods

The electrophysiologic properties of N-phenylethyl amitriptyline were assessed in cultured neuronal GH(3) cells with the whole cell mode of the patch clamp technique, and the therapeutic range and toxicity were evaluated in the rat sciatic nerve model.

Results

In vitro, N-phenylethyl amitriptyline at 10 microm elicits a greater block of Na(+) channels than amitriptyline (resting block of approximately 90% vs. approximately 15%). This derivative also retains the attribute of amitriptyline in evoking high-degree use-dependent blockade during repetitive pulses. In vivo, duration to full recovery of nociception in the sciatic nerve model was 1,932 +/- 72 min for N-phenylethyl amitriptyline at 2.5 mm (n = 7) versus 72 +/- 3 min for lidocaine at 37 mm (n = 4; mean +/- SEM). However, there was evidence of neurotoxicity at 5 mm.

Conclusion

N-phenylethyl amitriptyline appears to have a narrow therapeutic range but is much more potent than lidocaine, providing a block duration several times longer than any clinically used local anesthetic. Further work in animal models of neuropathic pain will assess the potential use of this drug.
Acute Normovolemic Hemodilution Improves Oxygenation in Ischemic Flap Tissue
Authors: Schramm Sören , Wettstein Reto , Wessendorf Robert , Jakob Stephan M. , Banic Andrej , Erni Dominique
Published: November 2003

Background

The flaps used in reconstructive surgery are prone to ischemia and hypoxia, which imply a considerable risk of wound-healing complications. During normovolemic hemodilution, the oxygenation may further deteriorate because of the lack of erythrocytes or improve because of increased microcirculatory blood flow. The aim of this study was to investigate the net effect of normovolemic hemodilution of various degrees on the microcirculation and oxygenation in ischemic flap tissue in adult minipigs.

Methods

A rectangular flap was raised in the middle of the epigastrium, consisting of an adequately perfused portion and a partly ischemic portion. The animals were randomly assigned to either the control group (n = 10) or the experimental group (n = 10) receiving graded normovolemic hemodilution with 6% hydroxyethyl starch 200-0.5.

Results

Normovolemic hemodilution caused a significant linear increase in total blood flow to the flap (measured by transit time flowmetry). In the ischemic flap tissue, both oxygen tension (measured by polarographic cells) and venous base excess were transiently improved during hemodilution (F = 4.79 and P = 0.019 for the regression of tissue oxygen tension on hemoglobin and hemoglobin squared, and F = 4.18 and P = 0.029 for base excess). The expected values reached a peak at hemoglobin concentrations of 9.1 and 8.5 g/dl, respectively. The measured values at this level of hemodilution were 17 +/- 10.7 mmHg (mean +/- SD) versus 7.6 +/- 1.9 mmHg (baseline) for oxygen tension and -1.7 +/- 3.4 versus -5.6 +/- 4.1 mM for venous base excess.

Conclusions

Our results suggest that the oxygenation in ischemic and hypoxic flap tissue may be improved by normovolemic hemodilution. The maximal benefit may be expected at a hemoglobin concentration at or slightly less than 9 g/dl.
Sevoflurane but Not Propofol Preserves Myocardial Function in Coronary Surgery Patients
Authors: De Hert Stefan G. , ten Broecke Pieter W. , Mertens Els , Van Sommeren Esther W. , De Blier Ivo G. , Stockman Bernard A. , Rodrigus Inez E.
Published: November 2003

Background

Sevoflurane has been shown to protect against myocardial ischemia and reperfusion injury in animals. The present study investigated whether these effects were clinically relevant and would protect left ventricular (LV) function during coronary surgery.

Methods

Twenty coronary surgery patients were randomly assigned to receive either target-controlled infusion of propofol or inhalational anesthesia with sevoflurane. Except for this, anesthetic and surgical management was the same in all patients. A high-fidelity pressure catheter was positioned in the left ventricle and the left atrium. LV response to increased cardiac load, obtained by leg elevation, was assessed before and after cardiopulmonary bypass (CPB). Effects on contraction were evaluated by analysis of changes in dP/dt(max). Effects on relaxation were assessed by analysis of the load dependence of myocardial relaxation (R = slope of the relation between time constant tau of isovolumic relaxation and end-systolic pressure). Postoperative concentrations of cardiac troponin I were followed during 36 h.

Results

Before CPB, leg elevation slightly increased dP/dt(max) in the sevoflurane group (5 +/- 3%), whereas it remained unchanged in the propofol group (1 +/- 6%). After CPB, leg elevation resulted in a decrease in dP/dt(max) in the propofol group (-5 +/- 4%), whereas the response in the sevoflurane group was comparable to the response before CPB (5 +/- 4%). Load dependence of LV pressure fall (R) was similar in both groups before CPB. After CPB, R was increased in the propofol group but not in the sevoflurane group. Troponin I concentrations were significantly lower in the sevoflurane than in the propofol group.

Conclusions

Sevoflurane preserved LV function after CPB with less evidence of myocardial damage in the first 36 h postoperatively. These data suggest a cardioprotective effect of sevoflurane during coronary artery surgery.
Isoflurane-induced Facilitation of the Cardiac Sarcolemmal KATPChannel
Authors: Fujimoto Kazuhiro , Bosnjak Zeljko J. , Kwok Wai-Meng
Published: November 2003

Background

Volatile anesthetics have cardioprotective effects that mimic ischemic preconditioning, including the involvement of adenosine triphosphate-sensitive potassium (K(ATP)) channels. However, evidence for a direct effect of volatile anesthetic on the K(ATP) channel is limited. In this study, the effects of isoflurane on the cardiac sarcolemmal K(ATP) channel were investigated.

Methods

Single ventricular myocytes were enzymatically isolated from guinea pig hearts. Whole cell and single-channel configurations, specifically the cell-attached and inside-out patch mode, of the patch clamp technique were used to monitor sarcolemmal K(ATP) channel current.

Results

In the cell-attached patch configuration, 2,4-dinitrophenol (150 microm) opened the sarcolemmal K(ATP) channel. Isoflurane (0.5 mm) further increased channel open probability and the number of active channels in the patch. In contrast, in the inside-out patch experiments, isoflurane had no significant effect on the K(ATP) channel activated by low ATP (0.2-0.5 mm). In addition, isoflurane had no effect on the K(ATP) channel when activated by adenosine diphosphate, adenosine + guanosine triphosphate, bimakalim, and 2,4-dinitrophenol under inside-out patch configurations. When K(ATP) current was monitored in the whole cell mode, isoflurane alone was unable to elicit channel opening. However, during sustained protein kinase C activation by 12,13-dibutyrate, isoflurane activated the K(ATP) current that was sensitive to glibenclamide. In contrast, isoflurane had no effect on the K(ATP) channel activated by 12,13-dibutyrate in a cell-free environment.

Conclusions

Isoflurane facilitated the opening of the sarcolemmal K(ATP) channel in the intact cell, but not in an excised, inside-out patch. The isoflurane effect was not due to a direct interaction with the K(ATP) channel protein, but required an intracellular component, likely including the translocation of specific protein kinase C isoforms. This suggests that the sarcolemmal K(ATP) channel may have a significant role in anesthetic-induced preconditioning.
The Influence of Mild Hypothermia on the Pharmacokinetics and Time Course of Action of Neostigmine in Anesthetized Volunteers
Authors: Heier Tom , Clough David , Wright Peter M. C. , Sharma Manohar L. , Sessler Daniel I. , Caldwell James E.
Published: November 2003

Background

The pharmacokinetics, maximum effect, and time course of action of neostigmine were studied in seven human volunteers.

Methods

Each volunteer was studied twice, during both normothermia and hypothermia. Anesthesia was induced with 30 microg/kg alfentanil and 3 mg/kg propofol, and was maintained with 60-70% nitrous oxide and 0.7-0.9% isoflurane. The mechanical response of the adductor pollicis to train-of-four stimulation of the ulnar nerve was recorded, and central body temperature maintained stable at either less than 34.5 degrees C or greater than 36.5 degrees C by surface cooling or warming. Before neostigmine administration, a stable 5% twitch height was obtained by an infusion of vecuronium, and the infusion rate remained unchanged thereafter. Neostigmine, 70 microg/kg, was then infused over 2 min, and blood samples for estimation of neostigmine concentrations were collected at intervals for 240 min.

Results

With hypothermia, the central volume of distribution of neostigmine decreased by 38%, and onset time of maximum effect increased (4.6 vs. 5.6 min). Hypothermia did not change the clearance (696 ml/min), maximum effect, or duration of action of neostigmine.

Conclusions

The efficacy of neostigmine as an antagonist of vecuronium-induced neuromuscular block is not altered by mild hypothermia.
The Unexpected Difficult Airway and Lingual Tonsil Hyperplasia
Authors: Ovassapian Andranik , Glassenberg Raymond , Randel Gail I. , Klock Allan , Mesnick Paul S. , Klafta Jerome M.
Published: November 2003

Background

An unexpected difficult intubation occurs because physical examination of the airway is imperfect in predicting it. Lingual tonsil hyperplasia (LTH) is one risk factor for an unanticipated failed intubation that is not detectable during a routine oropharyngeal examination. The authors attempted to determine the incidence of LTH in unanticipated failed intubation in patients subjected to general anesthesia.

Methods

Thirty-three patients with unanticipated failed intubation via direct laryngoscopy were subjected to airway examinations and fiberoptic pharyngoscopy to determine the cause(s) of failure. Mouth opening, mandibular subluxation, head extension, thyromental distance, and Mallampati airway class were recorded. Fiberoptic pharyngoscopy was then performed to evaluate the base of the tongue and valleculae.

Results

Of these 33 patients, none had an airway examination that suggested a difficult intubation. The lungs of 12 patients were difficult to ventilate by mask. In 15 patients, airway measurements were within normal limits with Mallampati class of I or II. Ten patients had a Mallampati class III airway, 6 associated with obesity and 5 with mildly limited head extension. Among the 5 morbidly obese patients, most of the weight was distributed on the lower trunk and body. The 3 remaining patients had a thyromental distance of 6 cm or less but otherwise had a normal airway examination. The only finding common to all 33 patients was LTH observed on fiberoptic pharyngoscopy.

Conclusion

Lingual tonsil hyperplasia can interfere with rigid laryngoscopic intubation and face mask ventilation. Routine physical examination of the airway will not identify its presence. The prevalence of LTH in adults and the extent of its contribution to failed intubation is unknown.
Reengineering Intravenous Drug and Fluid Administration Processes in the Operating Room
Authors: Fraind Deborah B. , Slagle Jason M. , Tubbesing Victor A. , Hughes Samuel A. , Weinger Matthew B.
Published: November 2003

Background

A reengineering approach to intravenous drug and fluid administration processes could improve anesthesia care. In this initial study, current intravenous administration tasks were examined to identify opportunities for improved design.

Methods

After institutional review board approval was obtained, an observer sat in the operating room and categorized, in real time, anesthesia providers' activities during 35 cases ( approximately 90 h) into 66 task categories focused on drug/fluid tasks. Both initial room set-up at the beginning of a typical workday and cardiac and noncardiac general anesthesia cases were studied. User errors and inefficiencies were noted. The time required to prepare de novo a syringe containing a mock emergency drug was measured using a standard protocol.

Results

Drug/fluid tasks consumed almost 50 and 75%, respectively, of the set-up time for noncardiac and cardiac cases. In 8 cardiac anesthetics, drug/fluid tasks comprised 27 +/- 6% (mean +/- SD) of all prebypass clinical activities. During 20 noncardiac cases, drug/fluid tasks comprised 20 +/- 8% of induction and 15 +/- 7% of maintenance. Drug preparation far outweighed drug administration tasks. Inefficient or error prone tasks were observed during drug/fluid preparation (e.g., supply acquisition, waste disposal, syringe labeling), administration (infusion device failure, leaking stopcock), and organization (workspace organization and navigation, untangling of intravenous lines). Anesthesia providers (n = 21) required 35 +/- 5 s to prepare a mock emergency drug.

Conclusions

Intravenous drug and fluid administration tasks account for a significant proportion of anesthesia care, especially in complex cases. Current processes are inefficient and may predispose to medical error. There appears to be substantial opportunity to improve quality and cost of care through the reengineering of anesthesia intravenous drug and fluid administration processes. General design requirements are proposed.
Motion of the Diaphragm in Patients with Chronic Obstructive Pulmonary Disease while Spontaneously Breathing versus during Positive Pressure Breathing after Anesthesia and Neuromuscular Blockade
Authors: Kleinman Bruce S. , Frey Kerry , VanDrunen Mark , Sheikh Taqdees , DiPinto Donald , Mason Robert , Smith Theodore
Published: November 2003

Background

Diaphragmatic excursion during spontaneous ventilation (SV) in normal supine volunteers is greatest in the dependent regions (bottom). During positive pressure ventilation (PPV) after anesthesia and neuromuscular blockade and depending on tidal volume, the nondependent region (top) undergoes the greatest excursion, or the diaphragm moves uniformly. The purpose of this study was to compare diaphragmatic excursion (during SV and PPV) in patients with chronic obstructive pulmonary disease (COPD) with patients having normal pulmonary function.

Methods

Twelve COPD patients and 12 normal control subjects were compared. Cross-table diaphragmatic fluoroscopy was performed while patients breathed spontaneously. After anesthetic induction and pharmacologic paralysis and during PPV, diaphragmatic fluoroscopy was repeated. For analytic purposes, the diaphragm was divided into three segments: top, middle, and bottom. Percentage of excursion of each segment during SV and PPV in normal subjects was compared with the percentage of excursion of each segment in patients with COPD.

Results

There was no significant difference in the pattern of regional diaphragmatic excursion (as a percentage of total excursion)-top, middle, bottom-when comparing COPD patients with control subjects during SV and PPV. In the control subjects, regional diaphragmatic excursion was 16 +/- (5), 33 +/- (5), 51 +/- (4) during SV and 49 +/- (13), 32 +/- (6), 19 +/- (9) during PPV. In COPD patients, regional diaphragmatic excursion was 18 +/- (7), 34 +/- (5), 49 +/- (7) during SV and 47 +/- (10), 32 +/- (6), 21 +/- (9) during PPV.

Conclusion

Regional diaphragmatic excursion in patients with COPD during SV and PPV is similar to that in persons with normal pulmonary function.
Results of Contracture Tests with Halothane, Caffeine, and Ryanodine Depend on Different Malignant Hyperthermia-associated Ryanodine Receptor Gene Mutations
Authors: Fiege Marko , Wappler Frank , Weisshorn Ralf , Ulrich Gerbershagen Mark , Steinfath Markus , Schulte am Esch Jochen
Published: November 2003

Background

More than 20 mutations in the gene encoding for the ryanodine receptor (RYR1), a Ca2+ release channel of the skeletal muscle sarcoplasmic reticulum, have been found to be associated with malignant hyperthermia (MH). This study was designed to investigate the effects of different mutations in the RYR1 gene on contracture development in in vitro contracture tests (IVCT) with halothane, caffeine, and ryanodine.

Methods

Ninety-three MH-susceptible (MHS) patients, diagnosed by the standard IVCT with halothane and caffeine, were included in this prospective study. Surplus muscle specimens were used for an IVCT with 1 microm ryanodine. The contracture course during the ryanodine IVCT was described by the attainment of different time points: onset time of contracture and times when contracture reached 2 mN or 10 mN. In addition, all patients were screened for mutations of the RYR1 gene.

Results

In 36 patients, four different mutations of the RYR1 gene (C487-T, G1021-A, C1840-T, G7300-A) were found. The IVCT threshold concentrations of halothane and caffeine were lower in patients with the C487-T mutation compared with patients without a detected mutation in the RYR1 gene. In the IVCT with ryanodine, contracture levels of 2 mN and 10 mN were reached earlier in muscle specimens from patients with C487-T, C1840-T, and G7300-A mutations compared with specimens from patients with the G1021-A mutation and patients without detected mutation in the RYR1 gene.

Conclusions

The differences between the groups in the halothane and caffeine IVCT threshold concentrations and in the time course of contracture development in the ryanodine IVCT underline the hypothesis that certain mutations in the RYR1 gene could make the ryanodine receptor more sensitive to specific ligands. This may be an explanation for varying clinical symptoms of MH crisis in humans.
Memory Function during Propofol and Alfentanil Anesthesia
Authors: Kerssens Chantal , Lubke Gitta H. , Klein Jan , van der Woerd Andries , Bonke Benno
Published: November 2003

Background

Conscious recall and implicit memory have been shown to depend on hypnotic state as measured by electroencephalographic (EEG) bispectral index (BIS). A third expression of memory (unconscious-controlled memory) was recently observed after moderate to light sedation (BIS, 70-80). The present study investigated memory function during deep sedation (BIS, 60-70). As memory effects are small, the authors studied potential predictors of individual differences in memory performance.

Methods

Memory function and speed of information processing were assessed in 56 outpatients before surgery. During propofol anesthesia supplemented with alfentanil, patients heard a series of words while anesthesia was titrated to BIS, 60-70. In between words, response to command was assessed using the Isolated Forearm Technique. The authors tested memory with a word stem completion task and process dissociation procedure to distinguish explicit from implicit effects.

Results

Mean (+/- SD) BIS during word presentation was 64.0 +/- 3. Patients with conscious recall of verbal commands (n = 9) did not recall or recognize presented words. Even so, the process dissociation procedure revealed evidence of memory by a significantly higher hit rate in the inclusion condition (0.26) than in the exclusion condition (0.12). Patients without conscious recall showed no evidence of memory for presented words. Hit scores correlated significantly with scores in the preoperative memory test (r = 0.35).

Conclusions

The authors found evidence of weak explicit memory function during anesthesia titrated to BIS, 60-70. The observations strongly suggest that postoperative memory relates to awareness during anesthesia, but the nature of this relation remains unclear. Memory seems more likely in patients with good preoperative memory performance.
Method of Preload Reduction during LVPVR Analysis of Systolic Function
Authors: Haney Michael F. , Johansson Göran , Häggmark Sören , Biber Björn
Published: November 2003

Background

A graded preload reduction during analysis of the left ventricular pressure-volume relationship (LVPVR) is required for derivation of end-systolic elastance (Ees) and preload recruitable stroke work (PRSW). The authors aimed to measure serial changes in these systolic function parameters before and during planned circulatory interventions using two different methods of preload alteration: a positive airway pressure plateau (APP) and inferior vena cava occlusion (IVCO).

Methods

In eight animals, measurements were made at 38 degrees, 30 degrees, 32 degrees, 34 degrees, and posthypothermia 38 degrees C. In an additional eight animals, isoflurane, adrenaline, and aorta occlusion (balloon catheter occluder) were administered in series, each with a preintervention control measurement. Left ventricular volume was measured by conductance. Paired measurements of the systolic function parameters Ees and PRSW, each derived with two preload methods, were analyzed for bias.

Results

Circulatory alterations were achieved with the temperature, isoflurane, adrenaline, and aorta occlusion interventions. Measured changes in Ees and PRSW from control to intervention showed a strong correlation and no significant bias for APP in relation to IVCO. The APP-derived absolute values for Ees and PRSW demonstrated a consistent positive bias compared with IVCO.

Conclusion

The APP method for preload reduction during LVPVR analysis detected changes in Ees and PRSW during the circulatory interventions in this model that were not different than those detected using another preload reduction method, IVCO. APP and IVCO are not interchangeable methods for preload reductions during LVPVR absolute quantitation of systolic function, and each needs to be used serially.