Depth Of General Anesthesia Research Articles

The performance of Bispectral Index in children during equi-MAC halothane vs. sevoflurane anaesthesia

The reliability of the Bispectral Index for evaluating and monitoring the depth of general anaesthesia in children is not as great as for that in adults. Therefore we analysed Bispectral Index performance in children by comparing changes in Bispectral Index values during a standardized and equipotent anaesthetic regimen using either halothane or sevoflurane for the induction and maintenance of general anaesthesia. Special interest was focussed on excitation during induction, and whether it was associated with simultaneous changes in Bispectral Index scores. Twenty children (3-15 yr, ASA I-II) scheduled for general surgery were randomly allocated to either halothane (10 patients) or sevoflurane group (10 patients). Anaesthesia was induced by 3% halothane or 7% sevoflurane, either agent administered with 50% N2O in oxygen for 5 min, the period from the beginning of induction until intubation. Thereafter, anaesthesia was maintained by the respective volatile agent at 1 MAC (minimum alveolar concentration; in addition to 70% N2O in oxygen) and supplemented with remifentanil infusion adjusted to maintain the heart rate and mean arterial pressure to within 20% of the baseline values. Excitation at induction was defined as involuntary muscular movements. Sevoflurane induction produced a more rapid depression in Bispectral Index than halothane, the mean difference being greatest (47 Bispectral Index score) at 105 s. Excitation occurred in three patients during sevoflurane induction, which coincided with increases in Bispectral Index values in two of the three patients. During the maintenance phase at 1 MAC, the Bispectral Index (mean +/- SD) was 57+/-7 for halothane and 47+/-9 for sevoflurane (P < 0.05). The remifentanil doses did not differ between both groups. In children, halothane anaesthesia was associated with higher Bispectral Index values than sevoflurane when administered at 1 MAC. Large individual variation in Bispectral Index occurred within both groups. Due to these limitations, one should be cautious when interpreting paediatric Bispectral Index data.

Lighter General Anesthesia Causes Less Decrease in Arterial Pressure Induced by Epinephrine Scalp Infiltration During Neurosurgery

Scalp infiltration with epinephrine-containing lidocaine solution can elicit significant hypotension before craniotomy under general anesthesia. A prospective randomized controlled study was designed to observe whether a lighter depth of general anesthesia could prevent the unintentional hypotension induced by the epinephrine scalp infiltration during neurosurgery or not. Fifty patients undergoing scheduled neurosurgery involving craniotomy were randomly allocated into 2 groups. After anesthesia induction, anesthesia was maintained with propofol 2 mug/mL and rimifentanil 2 ng/mL by target-controlled infusion in group 1, and propofol 4 microg/mL and rimifentanil 4 ng/mL in group 2 (control group), respectively. All the patients received epinephrine scalp infiltration with 1% lidocaine 16 mL containing epinephrine 5 microg/mL. Mean arterial pressure (MAP) and heart rate were recorded at 30-second interval from the baseline to 5 minutes after the beginning of local infiltration. Bispectral index readings indicated group 1 had the lighter general anesthesia than group 2 (P<0.05). MAP was higher (P<0.05) and heart rate was lower (P<0.05) at 1.5 minutes time point in group 1 than group 2. The mean percentage of maximal decrease in MAP was group 1 (13%) <group 2 (24%) (P<0.05). The mean percentage of maximal increase in MAP was group 1 (10%)> group 2 (4%) without significant difference (P>0.05). The results implied that keeping a lighter general anesthesia caused less decrease in arterial blood pressure and was a relative effective method to prevent hypotension episode induced by epinephrine scalp infiltration.

Airway Protective Reflexes Evoked by Laryngeal Instillation of Distilled Water Under Sevoflurane General Anesthesia in Children

To investigate how sevoflurane modifies airway protective reflexes in anesthetized children, we recruited patients younger than 12-yr-old for our study. Anesthesia was induced with inhaled sevoflurane in oxygen. The airway was managed with a laryngeal mask airway and the patient breathing spontaneously. Depending on the depth of anesthesia, the subjects were divided into two groups: Group 1 and Group 2 (1% and 2% of end-tidal sevoflurane concentration, respectively). Behaviors of the larynx were assessed mainly by the fiberscopic images of the larynx as well as respiratory flow and esophageal pressure. A small dose, 0.02 mL/kg of distilled water (minimum 0.2 mL) was instilled to the larynx through a channel of the scope to evoke an airway protective reflex from the larynx. The responses were categorized into passive (laryngeal closure, laryngospasm, and apnea) and active (cough, expiration reflex, and swallowing reflex) responses. Ten subjects were included in each group. In both groups, the primary responses were passive; however, in Group 1, active reflexes were also observed in 8 of 10 subjects; no subjects in Group 2 had active reflexes (P < 0.01). We concluded that, in children, the depth of general anesthesia with sevoflurane modified airway protective reflexes.

The management of refractory generalised convulsive and complex partial status epilepticus in three European countries: a survey among epileptologists and critical care neurologists

Objective: To survey the current clinical treatment of refractory status epilepticus and to identify steps in its management which may need further investigation. Methods: Epileptologists and critical care neurologists were...

Care and Monitoring of the Anaesthetized Patient Including the Prevention of Injuries

Effective anaesthetic care aims to reduce the morbidity, mortality and complication rates from surgery. General anaesthesia renders the patient in a suitable state for surgery but, by interfering with control of vegetative functions, has many side effects. Sedation is often accomplished using lower doses of the same drugs used for general anaesthesia and forms part of a smooth continuum of increasing depth of general anaesthesia. The sedated patient should therefore be monitored just as diligently. Control of the airway is lost in general anaesthesia or ‘deep’ sedation by abolition of the protective reflexes which normally prevent aspiration. Control of breathing is impaired, leading to hypoventilation. Circulatory control is similarly blunted, with a tendency to vasodilatation whether general or regional anaesthesia is employed. Under general or regional anaesthesia, reflexes protecting the patient from noxious events are abolished (e.g. blinking, limb withdrawal, movement to relieve uncomfortable pressure points). Control of body temperature is impaired by both regional and general anaesthesia.

Care and Monitoring of the Anaesthetized Patient Including the Prevention of Injuries

Effective anaesthetic care aims to reduce the morbidity, mortality and complication rates from surgery. General anaesthesia renders the patient in a suitable state for surgery but, by interfering with control of vegetative functions, has many side effects. Sedation is often accomplished using lower doses of the same drugs used for general anaesthesia and forms part of a smooth continuum of increasing depth of general anaesthesia. The sedated patient should therefore be monitored just as diligently. Control of the airway is lost in general anaesthesia or ‘deep’ sedation by abolition of the protective reflexes which normally prevent aspiration. Control of breathing is impaired, leading to hypoventilation. Circulatory control is similarly blunted, with a tendency to vasodilatation whether general or regional anaesthesia is employed. Under general or regional anaesthesia, reflexes protecting the patient from noxious events are abolished (e.g. blinking, limb withdrawal, movement to relieve uncomfortable pressure points). Control of body temperature is impaired by both regional and general anaesthesia.

Clinical characteristics of perioperative coronary spasm: reviews of 115 case reports in Japan.

Factors affecting perioperative development of coronary spasm have not been elucidated. A number of case reports describing perioperative coronary spasm have appeared in Japanese anesthesia journals, mostly published in Japanese. The purpose of this study was to investigate the contributing factors affecting perioperative coronary artery spasm by reviewing the published articles. Reports were identified by using Medline database (1968-1998) or by manually searching nonindexed Japanese journals. The clinical characteristics of perioperative coronary spasm were analyzed in 115 patients who developed coronary artery spasm during the perioperative period. The mean age of the patients was 64 +/- 9 years (range, 36 to 87 years). There were 97 men (84%) and 18 women (16%). Preoperative risk factors included hypertension (27%), angina pectoris (27%), cigarette smoking (13%), and diabetes mellitus (11%). The attack was related to inadequate depth of general anesthesia (23%), use of vasopressors (22%), vagal reflex (19%), administration of drugs other than vasopressors (17%), and epidural block (15%). About 85% of patients showed no ischemic abnormality on the preoperative electrocardiogram, whereas 56% had significant coronary stenosis on postoperative coronary arteriography. Coronary spasm tended to occur in patients under inhalation anesthesia combined with epidural block. Nitrates alleviated the episode in the majority of cases, whereas defibrillation and cardiac massage were required in 19% of patients. No deaths were reported. Perioperative coronary spasm is prevalent in elderly male patients with coronary risk factors who undergo abdominal or thoracic surgery under inhalational anesthesia combined with epidural anesthesia. Instability of the autonomic nervous system and/or vascular hyperreactivity may be the underlying pathogenic mechanisms of perioperative coronary spasm.

Assessment of depth of general anesthesia

The daily use of muscle relaxants and the lack of correlation between the hemodynamic behavior and stages of general anesthesia represent the main obstacles in defining the level of cortical activity depression by the anesthetic drugs. Since classical EEG is cumbersome in the operating room, and demands special knowledge, computerized methods of EEG wave analysis have more or less replaced the 'raw' display of the electrical activity of CNS. The paper describes the place of spectral edge frequency (SEF), one of the parameters obtained by processing the EEG waves, in the list of variables which could be monitored during general anesthesia. Besides, our preliminary observations on a combination of mean blood pressure variations and SEF value are presented. In fact, we designed a hypothetical matrix of those two parameters, which seems to be a useful tool for guiding the general anesthesia. SEF kept in a pre-established range (usually 8-12 Hz) seems to be linked with a more evident hemo-dynamic stability. Some data also suggested that a stable SEF on that range contributed to a higher degree of immediate postoperative analgesia after Cesarean section. The limits of SEF oblige the scientists to go on looking for other monitored parameters, to be studied in correlation with processed EEG. Further studies are needed, in order to improve the anesthesiologist's capabilities to define correctly the stage of general anesthesia.

Influence of hypoxia on ventilatory responses to intralaryngeal CO 2 in cats

In decerebrate, vagotomized cats, induction of CO 2 into the isolated laryngeal airway while systemic P CO2 is held constant evokes dose-related reflex changes in ventilatory activity. Because systemic hypoxia is known to exaggerate ventilatory responses to other types of laryngeal chemo- stimulation in neonates, we have compared the responses of phrenic and hypoglossal nerve activities to ventilation of the larynx with 10% CO 2 during systemic hyperoxia (Fi o 2 = 1.00) to those during hypoxia (Fi o 2 = 0.12). Compared with hyperoxic baseline condition, hypoxia stimulated phrenic activity but attenuated the reduction in phrenic activity evoked by intralaryngeal CO 2. Hypoglossal activity was increased by intralaryngeal CO 2 and this response appeared to be reduced by hypoxia, but neither of these findings was statistically significant. The response of phrenic activity to intralaryngeal CO 2 during systemic hypercapnia was similar to that during hypoxia. The increase of phrenic activity in response to hypoxia was prevented by carotid body resection. Similarly, the hypoxic attenuation of the phrenic response to intralaryngeal CO 2 appeared to be absent after carotid body resection, although this finding was not established statistically. These results differ from previous reports of exaggerated laryngeal chemoreflex responses during hypoxia. The difference may reflect differences in the receptors and synaptic mechanisms of the reflexes, the severity and time course of hypoxia or the presence or depth of general anesthesia or sleep.

Changes in Systemic Blood Pressure and Cardiac Rhythm Induced by Therapeutic Compression of the Trigeminal Ganglion

PERCUTANEOUS COMPRESSION OF the trigeminal ganglion, which is currently being used for the control of trigeminal neuralgia, induces marked intraoperative elevations of the systemic blood pressure and heart rate changes, which may increase the risk of cardiovascular complications. We have analyzed the characteristics of the arterial hypertensive response and the cardiac rhythm changes induced by percutaneous compression of the trigeminal ganglion in 42 consecutive, unselected patients undergoing operations for essential trigeminal neuralgia under three different regimens of anesthesia. The first 22 patients (Group 1) underwent operations under brief general anesthesia without endotracheal intubation. The following 10 patients (Group 2) had general anesthesia with intubation and mechanical ventilation and received larger doses of hypnotic and analgesic agents. Finally, 10 more patients (Group 3), who also had general anesthesia with intubation, underwent local anesthetic blockade of Meckel's cave (injection of 1 ml of 1% lidocaine) before ganglion compression. Foramen ovale puncture elicited bradycardia in the majority of the patients of Groups 2 and 3, but only four patients (18%) of Group 1 showed bradycardia. Ganglion compression caused marked tachycardia in all patients of Groups 1 and 2; about one-third of the patients also had extrasystoles. By contrast, patients of Group 3, who had local anesthetic blockade of Meckel's cave before ganglion compression, did not develop tachycardia or extrasystoles. Foramen ovale puncture elicited marked elevations of the systemic blood pressure in all patients. Ganglion compression further increased blood pressure, except in patients of Group 3, who had local anesthetic blockade of Meckel's cave. Blood pressure increases elicited by both foramen ovale puncture and ganglion compression coincided with marked elevations of serum adrenaline and noradrenaline, which returned to basal (preoperative) levels within few minutes of the end of the stimulus. According to our findings, the sympathoadrenal response induced by the therapeutic compression of the trigeminal ganglion is not modified by the depth of general anesthesia. By contrast, the injection of lidocaine into Meckel's cave before ganglion compression seems to be an effective method for preventing the development of systemic arterial hypertension and tachycardia.

Changes in systemic blood pressure and cardiac rhythm induced by therapeutic compression of the trigeminal ganglion.

Percutaneous compression of the trigeminal ganglion, which is currently being used for the control of trigeminal neuralgia, induces marked intraoperative elevations of the systemic blood pressure and heart rate changes, which may increase the risk of cardiovascular complications. We have analyzed the characteristics of the arterial hypertensive response and the cardiac rhythm changes induced by percutaneous compression of the trigeminal ganglion in 42 consecutive, unselected patients undergoing operations for essential trigeminal neuralgia under three different regimens of anesthesia. The first 22 patients (Group 1) underwent operations under brief general anesthesia without endotracheal intubation. The following 10 patients (Group 2) had general anesthesia with intubation and mechanical ventilation and received larger doses of hypnotic and analgesic agents. Finally, 10 more patients (Group 3), who had general anesthesia with intubation, underwent local anesthetic blockade of Meckel's cave (injection of 1 ml of 1% lidocaine) before ganglion compression. Foramen ovale puncture elicited bradycardia in the majority of the patients of Groups 2 and 3, but only four patients (18%) of Group 1 showed bradycardia. Ganglion compression caused marked tachycardia in all patients of Groups 1 and 2; about one-third of the patients also had extrasystoles. By contrast, patients of Group 3, who had local anesthetic blockade of Meckel's cave before ganglion compression, did not develop tachycardia or extrasystoles. Foramen ovale puncture elicited marked elevations of the systemic blood pressure in all patients. Ganglion compression further increased blood pressure, except in patients of Group 3, who had local anesthetic blockade of Meckel's cave.(ABSTRACT TRUNCATED AT 250 WORDS)

O2-Aufnahme und CO2-Produktion bei total intravenöser Propofol-Alfentanil-Narkose unter Steady-State-Bedingungen

Depending on surgical and anaesthesiological procedures, anaesthesia leads to a reduction of O2 uptake (VO2), CO2 production (VCO2) and resting energy expenditure (REE). A controversial discussion on the degree of metabolic depression has continued in the literature fueled by a lack of studies in patients under standardised conditions. The goal of this study was to evaluate whether O2 consumption and/or CO2 production can be correlated to various depths of anaesthesia and whether VO2 could be a parameter to control narcosis. 12 patients (ASA I-II) scheduled for urological surgery of the lower abdomen, were given total intravenous anaesthesia with propofol and alfentanil. During a 60 minutes period the patients were first anaesthesized with an ED50 and then titrated to a dosage correlating with an ED95. The premedicated but awake patients each showed a REE which was about 10% below the calculated basal metabolism. Steady-state general anaesthesia led to an approximately 30% reduction of VO2, VCO2 an REE. Patients with adequate anaesthesia revealed no changes in oxidative metabolism with increased or decreased depth of anaesthesia. VO2 as a leading parameter proves to be problematic. It is useful as a measure for insufficient depth of general anaesthesia but fails to indicate overshooting anaesthesia depth.

The effect of metacaine (MS-222) on the activity of the efferent and afferent nerves in the teleost lateral-line system

1. Free-swimming fish (Tilapia leucosticta and Rutilus rutilus) were used to determine threshold concentrations required for general anesthesia with metacaine (MS-222). The criterion for anesthesia was reached at a concentration of 1:1500 (w/w) with both fish, although the symptoms were somewhat more pronounced in Rutilus. 2. Recordings of efferent spontaneous activity in the lateral-line nerve were used as a measure of the central effect of metacaine during administration in the respiratory stream, as compared with respiration of fresh water. The reduction of activity at the end of a 3-min exposure to the drug was 70%. 3. Maximum recovery (90% of the initial activity) was reached after 30 min application of fresh water. 4. The various efferent impulse types were differentially affected by the anesthetic. 5. Direct recordings from sound-sensitive neurons in the medulla confirm the strong central effect of metacaine. 6. Irrigation of the lateral-line system with anesthetic solution also produced a reduction in afferent spontaneous activity; there was a distinct peripheral effect even at the threshold concentration. 7. Reactions of trigeminal nerve fibers to mechanical stimulation of the skin were reduced after application of a metacaine solution to the skin. This finding confirms the local anesthetic effect of the drug. 8. The anesthetic solution at a given concentration had a greater effect on the CNS than on the peripheral receptors. 9. The implications of the results with respect to the risk of misjudging the depth of general anesthesia are discussed. 10. Because of the complexity of its anesthetic efficacy, it is recommended that metacaine not be used for neurophysiological investigations, but rather that the animals be immobilized by means of muscle relaxants.

Enflurane (Ēthrane*) and isoflurane (forane*): A comparison with nine general anaesthetics administered with passive hyperventilation

Studies were carried out on 22 large, male, mongrel dogs at two-week intervals, in a crossover design, to determine the metabolic, blood-gas and cardiovascular effects, and the rate of recovery to steady ambulation from a surgical depth of general anaesthesia administered with passive hyperventilation. To prepare the animal, induction of anaesthesia was accomplished with 20 mg/kg body weight of 2 per cent thiopentone, tracheal intubation and inhalation of 50 per cent nitrous oxide and oxygen. After attachment of recording equipment and drawing of control blood samples, a respirator was attached to the anaesthetic circuit to provide passive hyperventilation by providing pulmonary ventilation of 15 ml/kg body weight at the rate of approximately 25 cycles per minute for 90 minutes, adding an anaesthetic concentration of methoxyflurane, chloroform, trichlorethylene, halothane, halothane-ether, azeotrope, isoflurane, cnflurane, diethyl ether, or fluorexcne from an out-of-circuit calibrated vapourizer. Thiopentone and Innovar were also tested and were given by an intravenous drip infusion. Nitrous oxide 50 per cent was given with 50 per cent oxygen with all the maintenance agents. No muscle relaxants were used and no stimulants were administered at the end of the test period.

Propranolol and surgical anesthesia.

The potential danger of anesthetizing a patient on beta-adrenergic blockade therapy has long been recognized. The cases of 73 patients taking propranolol and anesthetized for non-cardiac operations were reviewed with regard to preoperative administration of propranolol and intraoperative and postoperative complications. Of these patients, 72 percent took propranolol to within 24 hours of operation and 85 percent took it to within 48 hours. The mean dose of propranolol was 77 mg/day (range, 10 to 320 mg/day). Anesthetic technics and agents included enflurane, halothane, N2O-narcotic-relaxant, and spinal anesthesia. There were only three episodes of hypotension, all of which responded to a decreased depth of general anesthesia, IV fluid administration, and, in one patient, a small dose of a vasopressor. There were no intraoperative or postoperative deaths. It is concluded that if propranolol is indicated for medical control of the patient's symptoms, it need not be discontinued before surgical anesthesia.

Experimental studies on the neurogenic bladder. XII. Changes of urethral resistance after section of various nerves

In our department, an experimental study on the vesical dysfunction after injury on the nervous system innervating the urinary bladder was already performed relating to the clinical aspect and available therapy of “Neurogenic Bladder”. However, there could scarcely be found an experimental observation of the urethral function after injury on the nerves innervating the urethra. Therefore, I had tried to examine on the relationship between the urethral function and the innervation on it, with the observation on the progressive change in urethral resistance following various sections of nerves of 68 adult male dogs. Next, I had investigated on the alteration of urethral resistance after the additional section of various nerves of animals in which sections of the nerves described above were previously performed. Furthermore, medical or surgical nerve blocks were performed on the clinical neurogenic bladder and its effect on the urethral resistance as well as on the micturition state were observed.With the experimental examination on the available condition for the estimation of urethral resistance, species of the animal, sex, body weight, depth of general anesthesia, and intravesical content are thought to be main factors affecting the results. So, I had determined the urethral resistance of male adult dogs, 10-20Kg in body weight, below 100 cc of intravesical content, light anesthesia just diminishing the palpebration reflex, with retrograde and descending watercolumn manometric technique, and obtained 55.04±4.68cmH2O as the normal value.First, bilateral section of the hypogastric or the pelvic nerve of male adult dog was performed. A spontaneous and very slight decrease of urethral resistance was observed in both cases just after the operation. However, with bilateral section of the pudendal nerve, a significant decrease of urethral resistance (57% of preoperative value) was remarkable, which was continued during about 1 month and then recovered slowly. It showed a value of only about 70% of preoperative state even 3 months after the operation. With unilateral section of the pudendal nerve, also there could be found a similar change of urethral resistance compared to that observed after bilateral section of the nerve. But it showed a value of about 70% of preoperative state just after the operation, while it was about 89% of that 3 months after the operation.Second, selective section of the 1st, 2nd, and 3rd sacral nerve roots, such as bilateral section of the ventral root, the dorsal root, the ventral-and-dorsal roots, the spinal ganglion, the ventral root-and-spinal ganglion, and these were spinal origin of the pudendal nerve, was performed. With the section of these nerve roots, urethral resistance had showed very similar change compared to that obtained after bilateral section of the pudendal nerve. The decrease of urethral resistance after the section of the ventral-and dorsal roots and/or that of the ventral root-and-spinal ganglion were rather dominant compared to that after the section of the individual sacral root, however, it could not be clarified the role of the sacral spinal ganglion on the urethral function.On the other hand, bilateral section of the pudendal nerve was performed in the animals in which bilateral section of the pelvic nerve was preceded before 1 month, but urethral resistance of these animals after the additional section of nerve showed a similar change which was found after the section of the pudendal nerve of normal animal. Next, bilateral section of the hypogastric nerve was performed 1 month after bilateral section of the pudendal nerve of the same animal. But there could not be found any effect of additional section of nerve on the urethral resistance which decreased after the section of the pudendal nerve. However, after various section of the sacral nerve root in animals in which bilateral section of the pudendal nerve was performed previously

Production of controllable apnea in anesthesia; combined use of narcotic analgesics and their antagonists.

The use of mechanical ventilators makes it necessary to render the patient apneic. The technique of using muscle relaxants to accomplish this aim has several disadvantages. One of the main disadvantages is the potential masking of inadequate planes of general anesthesia by the total neuromuscular blockade. The advent of narcotic antagonists made a new approach possible. Not only is the apnea produced by narcotic analgesics readily and predictably reversible but also the depth of general anesthesia is enhanced. Although this technique has been successfully employed in a large series of cases, it must still be considered in the experimental stage.

Pentobarbital Sodium Anesthesia in the Syrian Hamster

The Syrian hamster (Cricetus auratus) was studied to determine an effective dosage of pentobarbital sodium in relation to the length and depth of general anesthesia produced. In general, the hamster has an apparently greater tolerance to pentobarbital sodium both in anesthetic and lethal doses than the rat, guinea pig, or rabbit. No sex variation in reaction to the drug was observed in the hamsters studied.