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Effects of intravenous anesthetics on phosphatidylinositol turnover in rat cerebral cortical prisms.

Noradrenergic pathways in the brain have been thought to be related to the site of anesthetic action. Norepinephrine (NE) in the central nervous system stimulates phosphatidylinositol (PI) turnover through alpha 1-adrenergic receptors. The present study was designed to examine the effects of intravenous anesthetics on NE-induced PI turnover in rat cerebral cortical prisms. NE-induced inositol monophosphate (IP1) formation was inhibited by droperidol (dose for 50% inhibition [ID50], 0.0258 +/- 0.00023 microM [mean +/- SE]), fentanyl (2.36 +/- 0.0017), diazepam (201 +/- 2.12), and thiamylal (231 +/- 1.94) in a dose-dependent manner, but was not affected by ketamine. Naloxone or flumazenil did not attenuate the inhibitory effect of fentanyl or diazepam on NE-induced IP1 formation. The results suggest that these effects on the PI turnover in the cortex may be related to their pharmacologic properties including the anesthetic action.

Anesthetics, Intravenous↗

Medullary inspiratory neurons with stable respiratory rhythm and little correlation to phrenic high-frequency oscillation.

Respiratory neurons with a highly stable rhythm have been proposed to be involved in the central neural mechanism responsible for the respiratory rhythmogenesis. In the present study it was examined whether the stably discharging inspiratory neurons are related to the high-frequency oscillation (HFO) in the phrenic nerve activity. Experiments were performed on 27 vagotomized rabbits anesthetized with diethyl ether, immobilized with gallamine triethiodide, and ventilated artificially. Spike-triggered averaging was used to evaluate the degree of the correlation between inspiratory unit spikes and the phrenic HFO. Twenty out of the 35 inspiratory units examined were related to HFO and were located in the medullary reticular formation (n = 19; n, number of units) and in the vicinity of the nucleus tractus solitarius (n = 1). The correlation to HFO decreased after the intravenous injection of thiamylal. The inspiratory units with little correlation to HFO were located in the reticular formation of the pons (n = 3) and medulla (n = 12). The inspiratory neurons with a stable respiratory rhythm (n = 4) had little correlation to HFO and located in the lateral region of the medullary reticular formation. These results suggest that the central neural mechanisms responsible for phrenic HFO are not directly related to the respiratory rhythmogenesis.

Action Potentials↗

[Generalized tonic-clonic seizure induced by propofol in a patient with epilepsy].

A 47-year-old female was scheduled for ulnar osteotomy under general anesthesia combined with brachial plexus block. She had a history of symptomatic epilepsy due to subarachnoid hemorrhage. Immediately after giving 100 mg bolus of propofol to the patient, she developed generalized convulsion similar to a grand mal. The seizure was suppressed by the administration of thiamylal. After that no further convulsive attack occurred. Although it has been known that propofol has anticonvulsive properties, there have been several reported cases of seizure following the administration of propofol. Further studies are needed to clarify the mechanism of seizure induced by propofol in the patients with epilepsy.

Anesthesia, General↗

[A case of pulmonary edema after electroconvulsive therapy under propofol anesthesia].

Electroconvulsive therapy (ECT) was scheduled for a 61-yr-old woman with major depression who had been taking a beta-blocker for hypertension. She underwent the first ECT under thiamylal anesthesia uneventfully. The second ECT was performed under propofol anesthesia on the next day. Immediately after ECT, the heart rate dropped from 56 to 19 beats.min-1, which was remedied by intravenous atropine. Then, the blood pressure increased to 204/108 mmHg but it was controlled by nicardipine. However, the SpO2 decreased to 84-88% under oxygen administration by mask at a rate of 3 l.min-1. The patient complained of chest discomfort and had a bloody secretion from the trachea. A chest X-ray showed a butterfly shadow. The patient was diagnosed as having neurogenic pulmonary edema and was treated in the ICU by artificial ventilation and administration of diuretics and catecholamines. These treatments proved to be successful, and the patient was discharged from the ICU 4 days later uneventfully. This case indicates that hemodynamics should be carefully monitored following ECT and that care should be taken to prevent the occurrence of complications after ECT.

Anesthesia, Intravenous↗

[Whole body heat production as a quantitative marker of anesthetic management under general anesthesia].

In order to evaluate the effects of the rapid induction and the slow induction of general anesthesia on the management of anesthesia and the circadian rhythm, the time-dependent whole body heat production in mice (ICR, male, 6 to 10 weeks after birth) was measured by calorimeter. In the single administration of either an i.v. anesthetic (thiamylal) or a volatile anesthetic (isoflurane), the minimum heat production and its duration time were similar. In the co-administration of i.v. and volatile anesthetics, the minimum heat production was significantly lower (P < 0.01) and the duration of this minimum production was significantly more sustained (P < 0.01) compared to those seen in the single administration of each anesthetic. Moreover, by measurement of the whole body heat production, the slow induction of general anesthesia markedly affected the circadian rhythm on the next postoperative day. These results indicate that the measurement of the whole body heat production will be a marker for the recovery from general anesthesia and the return to the usual life style (such as the QOL).

Anesthesia, General↗

Actions of isoflurane and halothane in pregnant mares.

Eighteen healthy, pregnant mares scheduled for laparotomy and uterine manipulation were randomly allotted to 2 equal groups. After IV administration of xylazine hydrochloride and thiamylal sodium, general anesthesia was maintained with halothane (HALO) or isoflurane (ISO) in oxygen. Results of cardiovascular measurements were similar with both inhalant anesthetics; mean arterial blood pressure was 79 and 82 mm of Hg with HALO and ISO, respectively. Respiratory rate decreased most with ISO (mean frequency was 4 and 9 breaths/min with ISO and HALO, respectively). Partial pressure of arterial CO2 was increased similarly with HALO and ISO. Partial pressure of arterial O2 varied greatly among mares and decreased with duration of use of both anesthetics. Recovery time from anesthesia was significantly (P < 0.05) shorter after use of ISO vs HALO. Minor superficial injuries were associated with recovery from both anesthetics (in 5 mares with ISO and in 1 mare with HALO). Physical signs of postanesthetic myopathy or vital-organ dysfunction were not associated with either agent.

Anesthesia, Inhalation↗

Effect of xylazine on the arrhythmogenic dose of epinephrine in thiamylal/halothane-anesthetized horses.

The effect of xylazine on the arrhythmogenic dose of epinephrine (ADE) was studied in 9 horses. Anesthesia was induced by administration of guaifenesin (50 mg/kg of body weight, IV) followed by thiamylal (4 to 6 mg/kg, IV) and was maintained at 1 minimal alveolar concentration (MAC) of halothane (0.89%). Base apex ECG and facial artery pressure were recorded. Epinephrine was infused in a sequence of arithmetically spaced increasing rates (initial rate 0.25 micrograms/kg/min) for a maximum of 10 minutes. The ADE was defined as the lowest epinephrine infusion rate to the nearest 0.25 micrograms/kg/min at which at least 4 premature ventricular depolarizations occurred in a 15-second period. Xylazine (1.1 mg/kg, IV) was administered after the control ADE was determined. Xylazine did not significantly alter the ADE (control, 1.12 +/- 0.38 micrograms/kg/min; xylazine, 1.21 +/- 0.46 micrograms/kg/min). Blood pressure increased transiently for 8 minutes after xylazine administration. Baseline systolic and diastolic arterial pressures and heart rate were not significantly different from control baseline pressures and heart rate 15 minutes after xylazine administration. Blood pressure and heart rate increased significantly during control and xylazine ADE determinations. Significant differences in pH, PaO2, PaCO2, or base excess were not observed between baseline and ADE in the control or xylazine groups. One horse developed atrial fibrillation, and 2 horses developed ventricular fibrillation during ADE determinations.

Anesthesia, General↗

[Reduction of the concentration of isoflurane prevents tachycardia and hypertension associated with tracheal intubation].

BACKGROUND: High concentration of isoflurane often induces not only tachycardia but also hypertension during induction of anesthesia and causes further hyperdynamic changes after tracheal intubation. METHODS: Forty patients, ASA physical status I, were randomly assigned to receive 4% or 2.5% isoflurane. Anesthesia was induced with thiamylal and vecuronium followed by mask ventilation with 0.5% isoflurane in oxygen. Isoflurane concentration was gradually increased to 4% or 2.5% in 2 min and the trachea was intubated after 3 min. Systolic blood pressure (SBP) and heart rate (HR) were recorded every minute from induction of anesthesia. RESULTS: Mask ventilation with isoflurane induced a significant increase in HR in both groups, but the HR just before intubation was significantly lower in the 2.5% group than in the 4% group. SBP was significantly decreased in the 2.5% group, but a transient increase was seen in the 4% group. Tracheal intubation induced a marked increase in HR in both groups, but the HR was significantly lower in the 2.5% group than in the 4% group (115 +/- 14 and 130 +/- 18 beats x min(-1), respectively; P < 0.01). SBPs just after intubation were 166 +/- 24 and 154 +/- 20 mmHg in the 4% and 2.5% groups, respectively. The difference between the groups was not significant, but the patients in whom the SBP increased more than 180 mmHg were significantly fewer in the 2.5% group than in the 4% group (P < 0.05). CONCLUSIONS: Reduction of the isoflurane concentration from 4% to 2.5% during induction of anesthesia made the circulation stable, and decreased the incidence of excessive tachycardia and hypertension after tracheal intubation.

Adult↗

Emergence airway complications in children: a comparison of tracheal extubation in awake and deeply anesthetized patients.

We compared the differences in oxygen saturation and airway-related complications after tracheal extubation in pediatric patients undergoing elective strabismus surgery or adenoidectomy and/or tonsillectomy who were awake versus anesthetized. Seventy otherwise healthy patients between 2 and 8 yr of age were studied. Anesthesia was induced with halothane or thiamylal and maintained with nitrous oxide and halothane. After induction of anesthesia, the patients were randomly assigned to group 1 (awake extubation) or group 2 (anesthetized extubation). Oxygen saturation was measured continuously and recorded 10 min before extubation and at 1, 2, 3, 5, 7, 10, 15, 20, 25, and 30 min after tracheal extubation. Supplemental oxygen was administered when oxygen saturation values were less than 90% while breathing room air. Oxygen saturation levels were higher in group 2 than in group 1 at 1, 2, 3, and 5 min after extubation. There were no differences between the two groups in the number of patients requiring supplemental oxygen. The incidence of airway-related complications such as laryngospasm, croup, sore throat, excessive coughing, and arrhythmias was not different between the two groups. We conclude that the anesthesiologist's preference or surgical requirements may dictate the choice of extubation technique in otherwise healthy children undergoing elective surgery.

Adenoidectomy↗

Comparison of arrhythmogenic doses of epinephrine in heartworm-infected and noninfected dogs.

The arrhythmogenic dose of epinephrine (ADE) was determined in heartworm-infected and noninfected (control) dogs during thiamylal-induced and halothane-maintained anesthesia to assess the myocardial sensitization. The ADE in heartworm-infected dogs (2.42 +/- 0.26 micrograms/kg of body weight) was significantly lower than that for the controls (3.36 +/- 0.29 micrograms/kg). After 2 weeks, ADE was determined again in these dogs after atropine treatment. Atropine treatment lowered the ADE to 1.76 +/- 0.33 micrograms/kg and 1.77 +/- 0.19 micrograms/kg in heartworm-positive and -negative dogs, respectively. After 2 weeks more, the ADE was determined after administration of prazosin, an alpha 1-antagonist. Only 2 of 6 controls and 3 of 6 heartworm-positive dogs had arrhythmias after a threefold increase of ADE. The mean ADE in the dogs that responded to treatment were 7.4 micrograms/kg and 7.2 micrograms/kg for heartworm-positive and -negative dogs, respectively. The finding of this study indicated that ADE in heartworm-infected dogs were lower than those in the control dogs, which makes the heartworm-infected dogs more vulnerable to arrhythmia during anesthesia. Atropine did not protect the dogs of either group. However, prazosin protected the dogs of both groups by significantly increasing the threshold of the ADE. On the basis of our findings, to reduce the risk of arrhythmia, we suggest that routine screening of dogs for heartworm infection be done before anesthetics are used.

Anesthesia, Inhalation↗

[Barbiturate therapy in traumatic cerebral vascular disease: report of two cases].

We report two cases of traumatic cerebral vascular disease which were treated successfully with barbiturate. The first case sustained blunt trauma to the bilateral vertebral arteries, resulting in complete occlusion of both arteries. After ligation of the injured vertebral arteries, multiple cerebral infarction appeared. Cerebral angiography revealed dissection and stenosis of the bilateral internal carotid arteries. We treated this case with barbiturate (Thiamylal) in combination with administration of heparin. The second case sustained cerebral contusion and traumatic subarachnoidal hemorrhage as a result of a motor cycle accident. This patient deteriorated and cerebral angiography showed diffuse cerebral arterial vasospasms. When this was treated with induced hypertension, he developed recurrent subarachnoid hemorrhage. In order to protect the brain from ischemia without elevating blood pressure, we employed barbiturate therapy and the patient recovered without major neurological deficit. The condition of severe head injury with cerebral ischemia is complicated. Therefore it has been hard for neurosurgeons to cure the patient with this condition. But we treated it with barbiturate successfully. Barbiturate therapy in severe head injury with cerebral ischemia may decrease the mortality in that group of patients considered difficult to treat with the usual therapeutic modalities.

Adolescent↗

Hemodynamic effects of high-frequency oscillatory ventilation in halothane-anesthetized dogs.

Hemodynamic effects of spontaneous ventilation, intermittent positive-pressure ventilation (IPPV), and high-frequency oscillatory ventilation (HFOV) were compared in 6 dogs during halothane anesthesia. Anesthesia was induced with IV thiamylal Na and was maintained with halothane (end-tidal concentration, 1.09%). During placement of catheters, dogs breathed spontaneously through a conventional semiclosed anesthesia circuit. Data were collected, and dogs were mechanically ventilated, using IPPV or HFOV in random order. Ventilation was adjusted to maintain PaCO2 between 38 and 43 mm of Hg during IPPV and HFOV. Cardiac index, aortic blood pressure, and maximum rate of increase of left ventricular pressure were significantly (P less than 0.05) less during HFOV than during spontaneous ventilation, whereas right atrial and pulmonary artery pressure were significantly greater during HFOV than during spontaneous ventilation. During IPPV, only the maximum rate of increase of left ventricular pressure was significantly less than that during spontaneous ventilation.

Anesthesia↗

Inhibition of canine platelet aggregation by barbiturates.

The ability of barbiturates to affect in vitro platelet aggregation of canine platelets was examined. Platelet-rich plasma was incubated with thiamylal, pentobarbital, and barbital for 10 minutes before the addition of the aggregating stimulus. All three barbiturates produced a concentration-related inhibition of platelet aggregation induced by adenosine diphosphate (ADP) and collagen. The inhibitory effect of the barbiturates could not be overcome by increasing the concentration of extracellular calcium. In contrast to ADP- and collagen-induced aggregation, no inhibitory effect was observed on aggregation initiated by A23187, 12-O-tetradecanoylphorbol-13-acetate, or phospholipase C. In further studies, the ADP-induced rise in free cytosolic calcium was blocked by the barbiturates. These findings suggest that barbiturates may interfere with the rise in internal calcium associated with agonist-receptor stimulation of platelets.

Adenosine Diphosphate↗

Decreased tear production associated with general anesthesia in the dog.

Schirmer I tear tests were done on 20 dogs before and during general anesthesia. Atropine sulfate reduced tear production from a mean base-line value of 20.35 +/- 3.33 mm/minute to 14.10 +/- 6.13 mm/minute, 10 minutes after its subcutaneous administration. The combination of subcutaneous atropine, intravenous thiamylal sodium, and inhalation anesthesia reduced tear production to a mean value of 0.53 +/- 1.12 mm/minute at 60 minutes after induction.

Anesthesia, General↗

Acquisition and aggregation of canine blood platelets: basic mechanisms of function and differences because of breed origin.

A method for obtaining reliable blood platelet yields in canine platelet-rich plasma, using increased sodium citrate concentration, is presented. Maintaining a quiet environment or anesthetizing the animals with thiamylal sodium aids in collection of platelets. Aggregation of platelets from 60 dogs of various breeds in response to arachidonic acid, collagen, adenosine diphosphate, epinephrine, and serotonin was monitored. Canine platelets reversibly or irreversibly aggregated to arachidonic acid. The percentage of arachidonate-irreversible platelets varied from 0% to 100% depending upon the breed of dogs examined. Arachidonate-irreversible platelets also aggregated irreversibly at lower concentrations of collagen and exhibited biphasic irreversible aggregation to adenosine diphosphate and serotonin. Serotonin-induced irreversible aggregation was dependent upon receptor activation and upon arachidonic acid metabolism. Irreversible aggregation to serotonin was associated with release of 3H-serotonin and thromboxane B2 formation, indicating that a couple between the serotonergic receptor and arachidonic acid metabolism may exist.

Adenosine Diphosphate↗

Effects of atropine on cardiac rate and rhythm in dogs.

Changes in cardiac rate and rhythm were determined in atropinized dogs prior to, during, and after anesthetic induction with thiamylal sodium and maintenance with 1% halothane in 50% nitrous oxide and 50% oxygen. The incidence of cardiac dysrhythmias and sinus tachycardia was significantly higher prior to and after anesthetic induction in dogs given atropine, compared with dogs not atropinized. Second-degree atrioventricular block was the most frequent dysrhythmia prior to anesthetic induction in atropinized dogs. Most cardiac dysrhythmias were detected during the anesthetic induction and early maintenance periods. The most common dysrhythmias during these periods were unifocal ventricular premature depolarizations and ventricular bigeminy.

Anesthesia, Inhalation↗

[The effects of low dose clonidine on perioperative hemodynamics and anesthetic requirements in elderly patients].

The effects of clonidine, alpha 2-adrenergic receptor agonist, on perioperative hemodynamics and anesthetic requirements were studied in randomized 20 elderly patients without hypertension (ASA I-II) scheduled for elective abdominal surgery under general anesthesia. The control group (n = 10) was premedicated with oral diazepam 0.1 mg.kg-1 90 min prior to arrival in the operating room. The clonidine group (n = 10), in addition, received clonidine approximately 2.5 micrograms.kg-1 orally at the same time. Anesthesia was induced with fentanyl 2 micrograms.kg-1 and thiamylal 4 mg.kg-1. Vecuronium 0.15 mg.kg-1 following 0.01 mg.kg-1 priming dose was used to facilitate endotracheal intubation. Anesthesia was maintained with isoflurane in 50% nitrous oxide-oxygen and supplementary fentanyl. Clonidine effectively attenuated the cardiovascular response associated with laryngoscopy and tracheal intubation. Intraoperative variability of heart rate was significantly lower in patients receiving clonidine compared with controls. No significant differences in the requirements of either isoflurane or narcotic supplementation were observed between the two groups. We conclude that a low dose clonidine is a useful adjunct in the management of elderly patients without producing side effects.

Abdomen↗

[Anesthetic management for AICD (automatic implantable cardioverter defibrillator) implant surgery].

We studied anesthetic management and monitoring during AICD (automatic implantable cardioverter defibrillator) implantation. For anesthetic management, complete sedation and amnesia are needed during implantation procedures with rapid awakening and extubation after the surgery. We chose inhalation anesthesia supplemented with small doses of fentanyl or thiamylal. Monitoring for AICD implantation should be less invasive, continuous and rapid in responsiveness. For brain and cardiac monitoring, a combination of near infrared spectroscopy and transesophageal echocardiography was quite useful.

Anesthesia, General↗