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PubMed1997

The lateral pressure profile in membranes: a physical mechanism of general anesthesia.

A mechanism of general anesthesia is suggested and investigated using lattice statistical thermodynamics. Bilayer membranes are characterized by large lateral stresses that vary with depth within the membrane. Incorporation of amphiphilic and other interfacially active solutes into the bilayer is predicted to increase the lateral pressure selectively near the aqueous interfaces, compensated by decreased lateral pressure toward the center of the bilayer. General anesthesia likely involves inhibition of the opening of the ion channel in a postsynaptic ligand-gated membrane protein. If channel opening increases the cross-sectional area of the protein more near the aqueous interface than in the middle of the bilayer, then the anesthetic-induced increase in lateral pressure near the interface will shift the protein conformational equilibrium to favor the closed state, since channel opening will require greater work against this higher pressure. This hypothesis provides a truly mechanistic and thermodynamic understanding of anesthesia, not just correlations of potency with structural or thermodynamic properties. Calculations yield qualitative agreement with anesthetic potency at clinical anesthetic membrane concentrations and predict the alkanol cutoff and anomalously low potencies of strongly hydrophobic molecules with little or no attraction for the aqueous interface, such as perfluorocarbons.

Anesthetics, General↗
PubMed1996

Hemodynamic responses to an epinephrine test dose in adults during epidural or combined epidural-general anesthesia.

The efficacy of an epinephrine test dose during epidural and combined epidural-general anesthesia is unknown. Thirty-two patients were randomized to receive 2% lidocaine at either a high (25 mL) or low (12 mL) thoracic level of epidural anesthesia followed by general anesthesia with 1 minimum alveolar anesthetic concentration nitrous oxide and isoflurane. A 15-micrograms epinephrine test dose was intravenously administered prior to placement of the lumbar epidural catheter, 20 min after initiation of epidural anesthesia, and after 10 min of stable end-tidal concentrations of general anesthesia. Only high thoracic levels (T-5) of epidural anesthesia reduced the peak systolic blood pressure response to epinephrine (34 +/- 17 vs 18 +/- 11 mm Hg, control versus epidural stage; P < 0.05) and reduced the peak heart rate response when combined with general anesthesia (31 +/- 11 vs 15 +/- 8 bpm; P < 0.05). Incidences of identification of intravascular injection from hemodynamic responses were similarly reduced for systolic blood pressure (100% vs 44%) and heart rate (100% vs 38%). The standard 15-micrograms epinephrine test dose is unaffected by low thoracic levels of epidural anesthesia, but may have decreased sensitivity for detection of intravascular injection during high thoracic levels of epidural anesthesia, especially during general anesthesia.

Adult↗
PubMed1999

Drug interactions during anesthesia. General principles.

Anesthesia for most procedures in small animal practice involves administration of more than one drug. In addition, many patients concurrently receive a number of other drugs related to their surgical condition or disease. The probability of a drug interaction increases exponentially with the number of drugs a patient receives; therefore, the potential for drug interactions may be greater in anesthesia than for any other area of medicine. This article describes potentially harmful drug interactions that may occur in the anesthetic setting.

Anesthesia↗
PubMed1987

A flight simulator for general anesthesia training.

A simulator of general anesthesia is described. It consists of an integrated set of physiologic computer models and a graphics display. The model predicts many of the physiologic and pharmacodynamic changes associated with general anesthesia. It is a multiple model consisting of circulatory, respiratory, pharmacokinetic, and pharmacodynamic models and their interactions. The model can account for many pathologic states of the cardiorespiratory system plus poor renal and hepatic function. Both intravenous and inhalation agents are included. Examples of its capabilities are presented, including pharmacokinetic changes associated with thiopental administration to a hypovolemic subject, administration of oxygen in several pulmonary pathologic conditions, and a simulation of an induction using fentanyl or thiopental. The model, combined with the graphics interface, becomes a real-time simulator useful for training students and residents.

Anesthesia, General↗
PubMed2004

[The use of conscious sedation versus general anesthesia in modern dentistry: rising ethical dilemmas].

Conscious sedation and general anesthesia have been in the use of the dental profession since the first half of the 19th century. Although seemingly appealing to use due to alleviation of pain and anxiety induced by the dental treatment, the alteration of consciousness level of dental patients is not without risk. Morbidity and mortality due to dental treatment performed under general anesthesia were investigated at the last decades of the 20th century. The mortality rates found in these investigations were surprisingly high comparing to researches of morbidity and mortality due to other medical procedures, performed under general anesthesia. Therefore, although general anesthesia is sometimes the only way to treat certain patients, maintaining strict indications for dental treatment under general anesthesia is necessary. Conscious sedation was found as a safer alternative for achieving a level of consciousness enabling dental treatment in those patients who are unable to receive treatment in normal dental clinic settings. We therefore believe that conscious sedation should be the golden standard for the treatment of those patients. The practicing of dentistry in patients who have need of dental treatment under special settings such as general anesthesia and sedation raises ethical dilemmas to the caregiver. The following review will summarize the available data on morbidity and mortality due to dental treatment given under general anesthesia and conscious sedation. The ethical questions arising from their practicing will be discussed and some answers shall be proposed.

Anesthesia, Dental↗
PubMed2004

Early but no long-term benefit of regional compared with general anesthesia for ambulatory hand surgery.

BACKGROUND: The purpose of this study was to determine whether either regional anesthesia (RA) or general anesthesia (GA) provided the best analgesia with the fewest adverse effects up to 2 weeks after ambulatory hand surgery. METHODS: Patients undergoing ambulatory hand surgery were randomly assigned to RA (axillary brachial plexus block; n = 50) or GA (n = 50). Before surgery, all patients rated their hand pain (visual analog scale) and pain-related disability (Pain-Disability Index). After surgery, eligibility for bypassing the postanesthesia care unit ("fast track") was determined, and pain, adverse effects, and home-readiness scores were measured. On postoperative days 1, 7, and 14, patients documented their pain, opioid consumption, adverse effects, Pain-Disability Index, and satisfaction. RESULTS: More RA patients were fast-track eligible (P < 0.001), whereas duration of stay in the postanesthesia care unit was shorter in the RA group (P < 0.001). Time to first analgesic request was longer in the RA group (P < 0.001), and opioid consumption was reduced before discharge (P < 0.001). In the RA group, the pain ratings measured at 30, 60, 90, and 120 min after surgery were lower (P < 0.001), and patients spent less time in the hospital after surgery (P < 0.001). More GA patients experienced nausea/vomiting during recovery in the hospital (P < 0.05). However, on postoperative days 1, 7, and 14, there were no differences in pain, opioid consumption, adverse effects, Pain-Disability Index, or satisfaction. CONCLUSIONS: Despite significant reduction in pain before discharge from the hospital after ambulatory hand surgery, single-shot axillary brachial plexus block does not reduce pain at home on postoperative day 1 or up to 14 days after surgery when compared with GA. However, RA does provide other significant early benefits, including reduction in nausea and faster discharge from the hospital.

Adult↗
PubMed1998

Anesthetic mechanisms in-vitro and in general anesthesia.

1. There is no generally accepted and quantifiable definition of general anesthesia. 2. Ion channels are discussed as examples of in-vitro systems used to investigate anesthetic mechanisms. Experimental evidence has accumulated demonstrating that voltage-gated ion channels and ligand-gated ion channels may be affected by clinically relevant concentrations of general anesthetics. 3. There are many factors modulating the anesthetic sensitivity of ion channels, including membrane lipid, electrolyte environment, ion channel subtype, and the functional state of the network. 4. Neuronal networks relevant to human general anesthesia have to be identified before criteria can be formulated as to which component of any particular ion channel function has to be altered to what extent in order to make a contribution to clinical anesthesia.

Anesthesia, General↗
PubMed1989

Regional versus general anesthesia in high-risk surgical patients: the need for a clinical trial.

Regional anesthesia is often preferred over general anesthesia for patients with cardiovascular disease because of presumed decreased risk of perioperative myocardial ischemia. However, few studies have addressed this issue directly. To determine whether the type of anesthesia is independently associated with myocardial ischemia, records of 134 patients undergoing peripheral vascular grafting under general or regional anesthesia were examined. There were no significant differences preoperatively between groups in ASA class, age, sex, or prevalence of angina, diabetes, or hypertension. Twelve patients developed myocardial ischemia or infarction within 7 days of operation; 11 of these 12 patients had received regional anesthesia (p less than 0.015). The association between anesthetic approach and perioperative myocardial ischemia or infarction remained after adjustment for preoperative factors associated with ischemia or with type of anesthesia. General anesthesia does not appear to be associated with increased risk of myocardial ischemia, and stringent recommendations to avoid it in this population may be unfounded. A clinical trial is needed to define more clearly the risks and benefits of different types of anesthesia in high-risk patients.

Anesthesia, Conduction↗
PubMed2002

[Additive retrobulbar anesthesia in surgery of retinal detachment with general anesthesia. Reduced postoperative pain and stress response].

BACKGROUND: It has recently been shown that the pain occurring after retinal detachment surgery can be reduced by combined general and retrobulbar anesthesia. This study investigated the effect of retrobulbar anesthesia on the intra- and postoperative stress response and on postoperative pain, vigilance, nausea and vomiting. PATIENTS AND METHODS: In this prospective randomized study, 45 patients were enrolled where scleral buckling surgery for retinal detachment had been performed under general anesthesia. Bupivacain 0.5% (4 ml) was injected retrobulbarly in group I (n = 15) before surgery (preoperative) and in group II (n = 15) after surgery (postoperative), group III did not receive retrobulbar anesthesia. At different times during and after surgery, blood pressure, cortisol and glucose levels, time in the recovery unit, vigilance score, nausea and vomiting were measured and the pain score was determined. The dosages of intraoperative opioid analgetics and of postoperative pain medication were documented. RESULTS: Retrobulbar anesthesia reduces postoperative pain. Intra- and postoperative endogenous stress responses in groups I and II were reduced and the plasma levels of cortisol and glucose in group I were lower than in group II. In group I, nausea, dosages of intraoperative opioid analgetics and postoperative pain medication were reduced, the vigilance was increased and time in the recovery unit was shortened. CONCLUSIONS: The data show that combined local and general anesthesia has several advantages over general anesthesia alone, especially when the retrobulbar injection is given before retinal detachment surgery.

Aged↗
PubMed1987

Modifications in membrane properties of trigeminal sensory neurons during general anesthesia.

1. The effects of general anesthesia on passive and active membrane properties of trigeminal root ganglion neurons of decerebrate guinea pigs have been determined using frequency-domain analyses of small-amplitude perturbations of membrane voltage. Quantification of the effects was accomplished by fitting the complex impedance locus diagrams computed from the neuronal responses with a membrane model based on linearized Hodgkin-Huxley-like equations. 2. Endotracheal administrations of isoflurane (2-3% for periods of 30-180 s), the most extensively studied of five general anesthetics, did not elicit large changes in membrane potential or in electrical properties in 26 of the 38 neurons. In this relatively unresponsive group, application of isoflurane in higher concentrations (3-4%) tended to evoke small but significant changes (less than 20%) in membrane properties without altering membrane potential by greater than 5 mV. These changes consisted of increases in the effective input capacitance and input conductance. 3. The impedance magnitude functions were reduced in amplitude consistently in 12 of the 38 neurons during induction of general anesthesia with isoflurane (2-4%) or, in several cases, with halothane (2%). Such applications evoked depolarizations of 8-32 mV, which also were observed in several instances of anesthesia with enflurane and cyclopropane. Quantification of these effects on electrical properties by curve fitting with the linearized Hodgkin-Huxley model revealed increases in the effective input capacitance, in the time-invariant resting conductance, Gr, and in the voltage- and time-dependent conductance, GL. Sometimes, an initial decrease preceded the increase of Gr, and the relaxation time constant associated with GL usually was reduced by the anesthetic agent in the 12 neurons. 4. In 10 neurons, membrane resonance behavior (which was apparent as a large hump at low frequencies of the impedance magnitude functions) was reduced in amplitude, as well as broadened in bandwidth, when peak changes in membrane properties were evident, i.e., during surgical or deep anesthesia. These actions of isoflurane or halothane were correlated to a reduction in spike electrogenesis and they may account for the reduced tendency of neurons to fire repetitive action potentials during anesthesia with isoflurane or halothane.(ABSTRACT TRUNCATED AT 400 WORDS)

Anesthesia, General↗
PubMed2006

[Effects of general anesthesia for cesarean section on infants].

OBJECTIVE: To determine the safety of general anesthesia during cesarean section for neonates. METHODS: Singleton pregnant women for whom elective cesarean sections were planned after 37 gestation weeks were allocated to general anesthesia or epidural anesthesia. After preoxygenation, general anesthesia was induced with fentanyl (2.0 microg/kg), propofol (1.5 mg/kg) and vencuronium (0.08 mg/kg) followed by tracheal intubation. Oxygen-nitrous oxides (50%) was inhaled before delivery. Epidural anesthesia was performed at L(1 - 2) or L(2 - 3) on the left lateral decubitus position with 1.73% lidocaine carbonate (including 1:200 000 adrenaline). We studied arterial samples withdrawn from the infants 30 min after birth for the pH, PaO(2), PaCO(2), SPO(2) and Hct. Neonatal behavioral neurological assessments (NBNA) 3 - 5 days after birth were recorded. RESULTS: (1) The pH, PaO(2), PaCO(2), SPO(2) and Hct in the general anesthesia group were 7.34 +/- 0.08, (40 +/- 11) mm Hg, (73 +/- 17) mm Hg, (96.8 +/- 1.0)%, and (53 +/- 5)%, while in the epidural anesthesia group were 7.35 +/- 0.05, (41 +/- 8) mm Hg, (71 +/- 17) mm Hg, (96.6 +/- 1.0)%, and (54 +/- 6)%. (2) NBNA scores: In the general anesthesia group, neonatal adaptive capacity, passive tone, active tone, primary reflexes and general status were 12.6 +/- 0.7, 7.2 +/- 0.7, 7.4 +/- 0.6, 5.6 +/- 0.8, and 5.9 +/- 0.3 respectively. While in the epidural anesthesia group they were 13.4 +/- 0.8, 7.3 +/- 0.5, 7.3 +/- 0.8, 5.6 +/- 0.6, and 5.9 +/- 0.3 respectively. No significant difference was seen (P > 0.05) between the general anesthesia group and the epidural anesthesia group in NBNA scores, mean pH, PaO(2), PaCO(2), SPO(2) and Hct of newborn infants. CONCLUSION: It study suggests that general anesthesia for the elective cesarean section does not influence significantly the outcome of the newborn infants.

Adult↗
PubMed1995

A retrospective comparison of spinal and general anesthesia for vaginal hysterectomy: a time analysis.

The authors sought to compare time efficiency of spinal versus general anesthesia. The charts of 106 consecutive patients who had undergone a vaginal hysterectomy were analyzed. This analysis divided the patients into three groups: Group 1, spinal anesthesia; Group 2, general anesthesia; Group 3, spinal anesthesia with subsequent general anesthesia. The perioperative time course was divided into six intervals from entry into the operating room to discharge from the postanesthesia care unit (PACU). Total time was calculated by adding the six intervals. There were 85 patients in Group 1, 17 patients in Group 2, and 4 patients in Group 3. The mean times for surgical readiness once the anesthesiologist was present for Group 1, Group 2, and Group 3 were 21.4 +/- 7.3, 21.4 +/- 6.0, and 25.0 +/- 5.8 min, respectively. The total time for the three groups was 278.3 +/- 72.0, 245.9 +/- 23.1, and 295.0 +/- 101.2 min, respectively (P < 0.01 Group 1 vs Group 2). The difference in total time between Groups 1 and 2 was accounted for mainly by the stay in the PACU. This study concludes that there is no difference in the efficiency of operating room time use between spinal and general anesthesia.

Aged↗
PubMed2004

The Leg Drop Pendulum Test performed under general anesthesia in spastic cerebral palsy.

The general aim of this study was to examine the stiffness and damping characteristics (rate at which oscillations diminish) of limbs of a small population of patients with spastic cerebral palsy (CP) during the Leg Drop Pendulum Test while under general anesthesia and to compare them with patients without CP, both awake and under similar anesthetized conditions. To facilitate a quantitative comparison the authors defined a set of parameters that reflect the stiffness and damping of limbs with spasticity under general anesthesia. To give these parameters more meaning a similar set was constructed for children without disabilities under conditions of normal wakefulness and under anesthesia. The test population of 10 patients with spasticity ranged in age from 4 to 19 years and had a mean age of 10 years 9 months (SD 5 years 10 months); there were four females and six males. The control population consisted of eight patients without disabilities who ranged in age from 7 to 19 years with mean age of 13 years 9 months (SD 3 years 3 months); there were six females and two males. To even out the populations, two limbs from the non-affected sides of two patients with hemiplegic spasticity (both female) were used in the control group. The Leg Drop Pendulum Test was administered to 10 limbs with spastic CP and 10 control limbs under general anesthesia. The two test populations were chosen from patients who were previously scheduled to undergo surgery. Two measures compared limbs of those under anesthetic with those under alert conditions: the damped natural frequency and the damping ratio. The natural frequency is the frequency at which a pendulum oscillates as it comes to rest; the damping ratio is a measure of how quickly the oscillations diminish. In spasticity, active muscle tone disappeared under anesthesia. In both groups the underlying biomechanics of the limb varied considerably. In controls the variation seemed to be growth related.

Adolescent↗
PubMed2006

Does gastroschisis reduction require general anesthesia? A comparative analysis.

BACKGROUND: Outcome after gastroschisis repair without general anesthesia is controversial, and published conclusions are variable with no comparative studies. AIM: The aim of this study was to present a comparative study evaluating outcome after gastroschisis repair with and without general anesthesia. METHODS: An ambispective nonrandomized study of a cohort of 51 neonates born with gastroschisis between July 1998 and December 2003 was performed. Twenty-four neonates (group 1) had conventional reduction under general anesthesia, and 27 (group 2) cotside minimal intervention reductions were without general anesthesia. RESULTS: Groups were comparable regarding gestational age, birth weight, and quality of eviscerated bowel. Statistical significance (P < .05) was seen between groups 1 and 2 with regard to age at reduction of gastroschisis (5.6 +/- 2.5 vs 3 +/- 1 hours) and time taken for completion of gastroschisis reduction (58.1 +/- 15 vs 49 +/- 14 minutes). No statistical significance (P > .05) was seen with respect to start of feeds (10.4 +/- 3.6 vs 10.9 +/- 4.1 days), duration of total parenteral nutrition (21.5 +/- 7.3 vs 22.4 +/- 6.8 days), and total hospital (stay 29 +/- 10 vs 30 +/- 13 days). Admission to the intensive care unit was required in 92% in group 1 for 1 to 6 days vs 7% in group 2 for 3 to 6 days. There was 1 death in group 1 (4%). Total hospital cost in group 1 was 12,283 pounds sterling +/- 2438 pounds sterling vs 6208 pounds sterling +/- 2120 pounds sterling in group 2 (P = .013). CONCLUSIONS: Neonates with gastroschisis, whose bowel was reduced without general anesthesia, have similar outcomes to those whose bowel was reduced under general anesthesia. Both approaches appear to be safe and effective, but reduction without general anesthesia was cost-effective.

Anesthesia, General↗
PubMed2003

[General anesthesia for disabled patients undergoing dental treatment in a general hospital].

BACKGROUND: General anesthesia for dental treatment in disabled patients may present particular problems, especially when it is done in a general hospital, compared with specialized dental hospitals. METHODS: We surveyed 24 patients who underwent dental treatment under general anesthesia in our institution during the last decade. RESULTS: Electrocardiography or chest x-ray photography was not obtained in 8 patients owing to lack of patients' cooperation. Slow induction with sevoflurane was selected in 5 patients, because intravenous cannulae could not be placed owing to their rejection. Nasotracheal intubation was performed in all patients, but no difficulty in intubation was documented. As postoperative complications, we observed convulsion in one patient and muscle rigidity in another, but no critical troubles related to circulatory or respiratory status. In patients who were treated for more than ten teeth, we observed differences in age, body weight, duration of anesthesia, maximum concentration of sevoflurane administered during anesthesia, and use of postoperative analgesics compared with the other patients. CONCLUSIONS: We found particular problems of anesthesia for disable patients undergoing dental treatment in a general hospital, and suggest that information on numbers of teeth to be treated is helpful.

Adolescent↗
PubMed1998

[General anesthesia in a patient with Cornelia de Lange syndrome with restricted opening of the mouth].

Patients with Cornelia de Lange syndrome have many anomalies including micrognathia with a small mouth, a high arched palate, and a short neck, which might make laryngoscopy for tracheal intubation difficult during induction of general anesthesia. General anesthesia was performed in a patient with Cornelia de Lange syndrome, and restricted opening of the mouth, which had not been reported previously, was found during laryngoscopy. The possible causes were thought to be temporo-mandibular joint disorders, contracture of the masseter muscle due to injury by self-destructive tendencies, or elogated coronoid process. The potential difficulty with laryngoscopy should be considered for tracheal intubation in a patient with Cornelia de Lange syndrome.

Adult↗
PubMed1982

[Advantages and disadvantages of regional anesthesia in comparison with general anesthesia].

The advantages and disadvantages of different anaesthetic techniques are based upon important premises, such as specific effects on the vital functions of the organism, the relationship of these effects to the general condition of the patient, the specific risk of complications due to a particular anaesthetic technique and the decision of the patient. Only with these points in mind can advantages and disadvantages of the different anaesthetic techniques be determined respective to the individual cases. The choice of a suitable anaesthetic technique should depend upon this determination.

Anesthesia, Conduction↗