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PubMed1984

Effects of halothane or enflurane with controlled ventilation on auditory evoked potentials.

The effects of increasing concentrations of halothane and enflurane on selected components of the auditory evoked response were studied in 12 patients; six received halothane and six enflurane. After the induction of anaesthesia with thiopentone, anaesthesia was maintained with 70% nitrous oxide in oxygen. Ventilation was controlled. The inspired concentration of the inhalation agent was increased incrementally, halothane in steps of 0.5% up to 2.5%, and enflurane in steps of 1% up to 5%. With both agents, linear dose-related increases were seen in the latencies of waves III, V, Pa and Nb and the interpeak intervals I-V and III-V, with decreases in the amplitudes of Pa and Nb. In five of the patients the inhalation agent was discontinued at the end of the test period, resulting in reversal of the changes in some or all of these waves. End-tidal carbon dioxide tension was controlled and variations of temperature and arterial pressure were insufficient to produce the observed changes. The results show that halothane and enflurane delay neural transmission along the brainstem and cortical sections of the auditory pathway and that the effects of these agents are approximately related to their known anaesthetic potencies.

Adolescent↗
PubMed1984

Displacement of some basic drugs from human serum proteins by enflurane, halothane and their major metabolites. An in vitro study.

The influence of volatile anaesthetics (halothane, enflurane) on the serum protein binding of three highly bound basic drugs has been studied in vitro by equilibrium dialysis. Radioactive labelled isotopes were used for the determination of drug concentrations. Enflurane, halothane and the halothane metabolite trifluoroacetic acid (TFA) inhibited the binding of diazepam to serum and to its main binding protein, albumin. The binding of diazepam to albumin was inhibited in a competitive manner and was not related to the anaesthetic potency of the vapours. Thus the observed displacement of diazepam should be regarded as a side-effect of the volatile anaesthetics. The binding of propranolol and prazosin in serum was not significantly influenced by the investigated anaesthetics. At clinically relevant concentrations of the anaesthetics, diazepam was displaced significantly only by enflurane with an increase in free fraction of 60% in serum. TFA in concentrations seen after operation significantly increased the free fraction of diazepam up to 90%. We conclude that enflurane anaesthesia may temporarily potentiate the pharmacological effect of diazepam and that, in the postoperative period following halothane anaesthesia, a more rapid elimination of diazepam could be expected.

Adult↗
PubMed1985

Outpatient termination of pregnancy: halothane or alfentanil-supplemented anaesthesia.

Inhalation anaesthesia with halothane was compared with i.v. alfentanil in 66 unpremedicated patients undergoing suction termination of pregnancy as outpatients. Blood loss was significantly greater in the halothane group with a mean loss of 213 ml, compared with a mean loss of 89.8 ml in the alfentanil group. There was a greater frequency of nausea and vomiting in the alfentanil group, but no reduction in abdominal pain or need for analgesia after operation. Positive relationships were found between blood loss and duration of anaesthesia and between blood loss and gestational age in the halothane group, but not in the alfentanil group. We conclude that alfentanil-supplemented anaesthesia is satisfactory for suction termination of pregnancy when rapid recovery is required or the duration of the procedure is likely to be long, but that halothane anaesthesia cannot be recommended, especially if the procedure is long.

Abortion, Induced↗
PubMed1986

Effects of combined extradural blockade and general anaesthesia on indocyanine green clearance and halothane metabolism.

Cardiovascular effects, indocyanine green clearance and the reductive metabolism of halothane were compared in 10 patients having peripheral surgery who received either general anaesthesia or general anaesthesia plus extradural blockade. Bupivacaine or saline was given extradurally 1 h before anaesthesia with nitrous oxide:oxygen (70:30) and halothane (end-tidal concentration 0.35%). Indocyanine green clearance was measured before (stage I) and after (stage II) bupivacaine or saline, during anaesthesia before surgery (stage III), and during surgery (stage IV). Reductive metabolism of halothane was assessed by measurement of exhaled 2-chloro-1,1,1-trifluoroethane. In the general anaesthesia plus extradural blockade group, arterial pressure was decreased to 58% (SD = 6) of stage I values over stages II-IV, whereas no changes were observed in the general anaesthesia group. There was no significant difference in indocyanine green clearance or the reductive metabolism of halothane, despite the occurrence of significant decreases in arterial pressure.

Adult↗
PubMed1986

Comparison of the incidence and nature of cardiac arrhythmias occurring during isoflurane or halothane anaesthesia. Studies during dental surgery.

Seventy-six Chinese patients aged between 15 and 30 yr, undergoing 3rd molar extraction, were randomly allocated to two groups. One group received halothane and the other isoflurane. The incidence of arrhythmia during surgery under anaesthesia with isoflurane was significantly less than with halothane. Sinus tachycardia was a significant feature under anaesthesia with isoflurane. Under anaesthesia with halothane, the arrhythmias occurring most frequently during surgery were ventricular ectopics, the commonest being ventricular bigeminy. The frequency and nature of arrhythmias during surgery on right and left sides were similar. In three patients a slight decrease in arterial pressure was recorded in association with the arrhythmia, but on stopping the stimulus, both rhythm and arterial pressure returned to normal. The incidence of arrhythmia with halothane in the Chinese population in this study was significantly higher than that reported previously in non-Chinese patients.

Adolescent↗
PubMed1986

Control of end-tidal halothane concentration. Part A: Anaesthesia breathing system and feedback control of gas delivery.

Conventional anaesthetic breathing systems are not designed to control end-tidal gas concentrations, nor can they be used to measure accurately the uptake of oxygen or of anaesthetic agent. We built and tested a leak-tight closed-loop anaesthetic breathing system with low solubility to volatile anaesthetic agents and with efficient gas mixing. The system included a water-sealed spirometer, a small carbon dioxide absorber, a coaxial tube to the patient, a circulating pump and feedback controllers for system volume and anaesthetic concentration. Feedback control was implemented to adjust and control automatically the end-tidal anaesthetic concentration and the volume of the system with oxygen supplied through a mass flow controller and with halothane supplied by a titrating syringe. Controller gains, as a function of body weight, were found using a nine-compartment tissue uptake model. Stability was maintained with +/- 50% changes in alveolar ventilation and cardiac output. During subsequent investigations in an animal model, arterial, mixed venous and cerebral venous blood halothane concentrations were measured to show that the feedback-controlled halothane induction was optimized. We conclude that feedback control appears to be clinically applicable for adjusting the end-tidal halothane concentration and system volume to provide a rapid and optimized induction of anaesthesia.

Anesthesia, Inhalation↗
PubMed1987

Relationship between lower oesophageal contractility, clinical signs and halothane concentration during general anaesthesia and surgery in man.

The effects of a range of concentrations of halothane upon lower oesophageal contractility (LOC) and on defined clinical signs has been studied in patients undergoing surgery. Changes in clinical signs were assigned a numerical value by means of a scoring system. One hundred and eighty-one sets of measurements were made in 46 patients exposed to concentrations of halothane between 2.0 and 0.5 minimum alveolar concentration (MAC). The results were examined to identify relationships between (i) the clinical signs and alveolar halothane concentration, (ii) the clinical signs and LOC and (iii) the changes in LOC and alveolar concentration; significant correlations were found between these variables. Decreasing alveolar halothane concentration was associated with an increase in LOC and these increases in LOC were also associated with increases in the clinical score.

Adult↗
PubMed1987

Effects of halothane, isoflurane and enflurane on ventilation in children.

The ventilatory effects of halothane in eight children were compared with those of isoflurane in eight children and enflurane in six children. All studies were completed before surgery commenced, and the children received no preoperative medication. The depression of ventilation produced by the three agents increased in a dose-related fashion as the alveolar concentrations were increased, and the depression of ventilation that they produced in oxygen was greater than that produced by equipotent concentrations in nitrous oxide. While the increase in ventilatory frequency and the decrease in TE associated with increasing concentrations of halothane were statistically significant (P less than 0.05), the increase in frequency associated with isoflurane was not, although it was sufficient to maintain the end-tidal and arterialized venous PCO2 in the isoflurane group at a value which did not differ significantly from that in the halothane group. Profound depression of ventilation was produced in the children by enflurane, clearly because no increase in ventilatory frequency was associated with its use. It was evident that the ventilatory effects of the three volatile agents in unstimulated children are very similar to those described elsewhere in the adult. There was no difference of any clinical significance between the degree of depression of ventilation produced by halothane and isoflurane in children.

Anesthesia, Inhalation↗
PubMed1990

End-tidal concentrations of halothane and isoflurane during induction of anaesthesia in young and elderly patients.

Twenty-two young (18-32 yr) and 22 healthy elderly (60-80 yr) patients received either halothane or isoflurane for maintenance of anaesthesia during controlled ventilation. End-tidal fractional concentrations (FE) of the agents were measured for 20 min after their introduction into inspired gas and the increase in end-tidal concentrations of the two agents was compared during induction of anaesthesia using the ratios of FE to the inspired fraction (FI). FE:FI ratios for isoflurane were higher than those for halothane in both young and elderly patients, confirming that equilibration of end-tidal with inspired concentration occurs more rapidly with isoflurane than with halothane in both age groups. FE:FI ratios for isoflurane became significantly lower in the elderly than in the young after 15 min administration of isoflurane. This suggests slower induction of anaesthesia in the elderly if equipotent concentrations of isoflurane are used; the clinical significance of this difference is probably small. Mean FE:FI ratios for halothane in elderly patients were similar to those in the young throughout induction of anaesthesia.

Adolescent↗
PubMed1990

Neuromuscular and cardiovascular effects of mivacurium chloride (BW B1090U) during nitrous oxide-fentanyl-thiopentone and nitrous oxide-halothane anaesthesia.

Seventy-two adult surgical patients were studied to compare neuromuscular and cardiovascular effects of mivacurium chloride during nitrous oxide-fentanyl-thiopentone (BAL group) or nitrous oxide-halothane (HAL group) anaesthesia. Eighteen patients in the BAL group received an initial bolus of mivacurium, either the ED25 (n = 9) or the ED50 (n = 9) (0.03 and 0.05 mg kg-1). These doses were based on the assumption that the slope of the dose-response curve during nitrous oxide-opioid anaesthesia would be approximately the same as the slope of the neuromuscular response from the first human studies with mivacurium. Twenty-seven additional patients were allocated to subgroups of nine patients to receive mivacurium 0.04, 0.08 or 0.15 mg kg-1. Twenty-seven patients in the HAL group were allocated also to subgroups of nine patients to receive mivacurium 0.03, 0.04 or 0.15 mg kg-1. During stable anaesthesia, mean endtidal halothane concentrations were maintained at 0.49 +/- 0.01%. The estimated ED50, ED75 and ED95 for BAL and HAL groups were 0.039, 0.05 and 0.073 mg kg-1 and 0.040, 0.053 and 0.081 mg kg-1, respectively. Halothane did not potentiate maximum block or time to maximum block. Halothane did affect spontaneous recovery. With the 0.15-mg kg-1 dose, time to 95% recovery was prolonged significantly in the HAL group (30.0 (SEM 1.4) min) compared with the BAL group (24.1 (1.5) min). Recovery index from 25% to 75% recovery was also prolonged significantly in the HAL group (7.0 (0.4) min) compared with the BAL group (5.4 (0.4) min). There were no significant haemodynamic changes in groups given mivacurium doses up to and including 2 x ED95 by bolus i.v. administration.

Adolescent↗
PubMed1990

Influence of halothane on the train-of-four fade after atracurium in children.

The influence of halothane was studied on train-of-four fade during spontaneous recovery from neuromuscular block produced by atracurium in 42 children undergoing routine surgical procedures under general anaesthesia. The ulnar nerve was stimulated at the wrist, and compound electromyographic responses were recorded from the adductor pollicis brevis, using a Relaxo-graph. One group of children was anaesthetized with nitrous oxide and 1% halothane (end-tidal concentration) in oxygen; in the other group nitrous oxide and fentanyl in oxygen was used (control group). Halothane was found to increase the train-of-four fade during the recovery phase compared with control. It is possible that presynaptic and postsynaptic cholinoceptors differ in their sensitivity to the depressant action of halothane.

Anesthesia, General↗
PubMed1991

Halothane hepatitis.

The historical background, clinical features, morphology, epidemiology and aetiology of halothane hepatitis have been presented. Animal models of halothane hepatotoxicity have been described, although their application to humans is of doubtful significance. Two, probably distinct, forms of liver damage associated with halothane have been identified. The much more common mild form may result from reductive biotransformation of halothane, possibly influenced by genetic factors, or reduced liver oxygenation, whereas the rare fulminant form is most likely to be immune-mediated. The role of altered calcium homeostasis has not yet been established. In addition, a common mechanism for liver dysfunction associated with halogenated volatile anaesthetic agents has been proposed. The hepatotoxicity of enflurane cannot be excluded; while hepatic dysfunction after isoflurane or nitrous oxide is considered unlikely, further attention is necessary. It is too soon to comment on the hepatotoxic potential of sevoflurane or desflurane.

Anesthesia, General↗
PubMed1991

Comparison between sevoflurane and halothane for paediatric ambulatory anaesthesia.

We have compared the rapidity and quality of recovery after sevoflurane anaesthesia with those after halothane anaesthesia. Thirty unpremedicated paediatric outpatients undergoing pulsed-dye laser therapy for port-wine stains were allocated randomly to receive either halothane or sevoflurane anaesthesia. Each group received 60% nitrous oxide and 1.0-1.5 MAC of volatile agent in oxygen for approximately 40 min. Patients receiving sevoflurane exhibited more rapid emergence and a significantly shorter postoperative recovery time compared with those receiving halothane. No major adverse effects were encountered in each group. These results suggest that sevoflurane anaesthesia is preferable to halothane anaesthesia for paediatric ambulatory patients.

Ambulatory Surgical Procedures↗
PubMed1991

Effect of PaCO2 on cerebral blood flow distribution during halothane compared with isoflurane anaesthesia in the rat.

In order to examine anaesthetic effects on the distribution of cerebral blood flow (CBF) during normo- and hypocapnia, male adult Sprague-Dawley rats were allocated randomly to four groups in a 2 x 2 factorial design, using PaCO2 value and anaesthetic agent as between-group factors. Animals were anesthetized with either 1.38% isoflurane (inspired) or 1.05% halothane (inspired) and the lungs ventilated mechanically at either normocapnia (PaCO2 5.1-5.6 kPa) or hypocapnia (PaCO2 3.1-3.3 kPa) for 1 h. CBF was measured using 14C-iodoantipyrine autoradiography. Local CBF in selected cortical and subcortical regions of interest and area-weighted mean global CBF were calculated. Data were compared by analysis of variance. Normocapnic (mean (SE] CBF for halothane (n = 6) and isoflurane (n = 7) was 120 (8) ml/100 g min-1 (PaCO2 5.6 (0.49) kPa) and 117 (9) ml/100 g min-1 (PaCO2 5.4 (0.5) kPa), respectively. Hypocapnic CBF for halothane (n = 6) and isoflurane (n = 6) was 82 (7) ml/100 g min-1 (PaCO2 3.3 (0.12) kPa) and 82 (6) ml/100 g min-1 (PaCO2 3.2 (0.12) kPa), respectively. Hypocapnia reduced global CBF for both groups by 30% (P less than 0.001), but there was no difference between anaesthetic agents (P greater than 0.8). Hypocapnia decreased CBF in all local structures examined. Although subcortical structures had similar CBF at both normocapnia and hypocapnia, CBF in three cortical samples was greater (P less than 0.05) in both the normocapnic and hypocapnic halothane groups than the corresponding isoflurane groups. The CBF reactivity to changes in PaCO2 was similar for both agents (approximately 2 ml/100 g min-1 mm Hg). (ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMed1991

Effects of low concentrations of cyclopropane and halothane on peak velocity of saccadic eye movements.

We have investigated the effect of 4.7 and 8.8% MAC of cyclopropane, and 5.3 and 9.3% MAC of halothane on the peak velocity of saccadic eye movements (PSV) in six healthy volunteers. Both concentrations of cyclopropane and halothane significantly depressed PSV (P less than 0.01) compared with air, in a dose-related fashion. Halothane depressed PSV significantly more than cyclopropane (P less than 0.05). PSV returned to baseline within 5 min after discontinuation of the agents. There was no significant difference between cyclopropane, halothane and air in subjective assessment of sedation.

Adult↗
PubMed1992

Transcranial Doppler sonography: effects of halothane, enflurane and isoflurane on blood flow velocity in the middle cerebral artery.

Systolic, diastolic, and mean blood flow velocity in the middle cerebral artery (Vs,mca; Vd,mca; Vm,mca) and pulsatility (Vs-Vd)/Vm of the waveform obtained were recorded in 51 patients before, during and after general anaesthesia. Transcranial Doppler (TCD) sonographic variables were measured in the awake patient and after induction of anaesthesia with thiopentone 5-6 mg kg-1. After tracheal intubation, 17 patients received 0.8% halothane and 66% nitrous oxide in oxygen for 30 min (15 min normoventilation; 15 min hyperventilation). The inspired halothane concentration was then increased to 1.6% for 45 min (15 min normoventilation; 15 min hyperventilation; 15 min normoventilation with nitrous oxide replaced by oxygen). Enflurane (1.7% for 30 min and 3.4% for 45 min) was given to another 17 patients; 17 other patients received isoflurane (1.2% and 2.4%). Mean arterial pressure (MAP), nasopharyngeal temperature, end-tidal carbon dioxide concentration, inspired and end-tidal anaesthetic agent concentrations, haemoglobin concentration, PVC and TCD variables were measured at the end of each 15 min period. After recovery from anaesthesia, TCD variables were measured again. There were no intergroup differences in changes in MAP, nasopharyngeal temperature, haemoglobin concentration and PCV. Halothane, enflurane and isoflurane at low doses and normoventilation had little influence on TCD variables compared with awake values. In large concentrations with nitrous oxide in oxygen and normoventilation, there were differences between the volatile agents. Halothane increased blood flow velocities, but enflurane and isoflurane caused little change. Hyperventilation always decreased blood flow velocities and increased pulsatility.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Isoflurane does not increase the incidence of intraoperative myocardial ischaemia compared with halothane during vascular surgery.

We have studied the incidence of new intraoperative myocardial ischaemia (IMI), myocardial infarction (MI) and cardiac death (CD) in 500 consecutive patients undergoing elective major non-cardiac vascular surgery. Patients were allocated randomly to receive either halothane (n = 226) or isoflurane (n = 274) as principal anaesthetic agent. Using real-time ST segment trend analysis (leads V5 and II) IMI (halothane 39%, isoflurane 38%), MI (halothane 1.3%, isoflurane 1.5%) and CD (halothane 0.4%, isoflurane 0.7%) did not differ significantly between the two groups. Twenty-three per cent of IMI episodes were related to haemodynamic disturbances, but unrelated to the type of surgery: 148 supra-aortic (IMI = 39%), 244 abdominal aortic (IMI = 41%) and 108 lower extremity revascularizations (IMI = 33%). We conclude that the choice of volatile anaesthetic agent does not influence cardiac morbidity or mortality in this type of patient.

Adult↗
PubMed1993

Cardiovascular effects of isoflurane and halothane in young and elderly adult patients.

We have studied the cardiovascular effects of 1 MAC end-tidal concentrations of halothane and isoflurane in young (n = 40) and elderly (n = 40) adult patients using non-invasive techniques. Cardiac output was measured by Doppler ultrasonography. Halothane reduced heart rate, systolic, mean and diastolic arterial pressures and cardiac index in both age groups (P < 0.05). Isoflurane reduced systolic, mean and diastolic arterial pressures also, but reduced cardiac index and heart rate only in the older patients (P < 0.05). Halothane depressed cardiovascular state significantly more than isoflurane in the younger adults (P < 0.05), but cardiovascular depression was similar for the two agents in the older age group. The decreases in systolic and diastolic pressures in the older patients were significantly greater with isoflurane compared with halothane (P < 0.05).

Adult↗