Epidural block does not worsen oxygenation during one-lung ventilation for lung resections under isoflurane/nitrous oxide anaesthesia

BACKGROUND AND OBJECTIVES: The aim of this prospective, randomized, controlled clinical study was to evaluate the effects of thoracic epidural anaesthesia combined with isoflurane/nitrous oxide anaesthesia on intraoperative oxygenation during one-lung ventilation for lung resections. METHODS: Forty patients were randomly allocated to receive general anaesthesia maintained with isoflurane/nitrous oxide (group General, n = 20) or the same anaesthetic combined with thoracic epidural anaesthesia (group Integrated, n = 20). All patients were mechanically ventilated with the same settings (FiO2 = 0.5; VT = 9 mL kg(-1); inspiratory: expiratory time = 1:1; inspiratory pause = 10%). Effects on oxygenation were evaluated by determining the changes in PaO2/FiO2 ratio at 10, 30, 45 and 60 min of one-lung ventilation as compared to values obtained after induction of anaesthesia (supine, two-lung ventilation). RESULTS: The PaO2/FiO2 ratio was decreased in both groups during one-lung ventilation until the end of surgery. No differences were found at any observation time between the groups. Ventilation with 100% oxygen because of SpO2 decrease <92% was required in nine patients of group General (45%) and in eight patients of group Integrated (40%) (P = 0.64). Manual re-inflation of the operated lung was required in one patient of group General only (P = 0.99). Heart rate was lower in group Integrated than in group General throughout the study. No differences between the two groups in mean arterial pressure were observed. CONCLUSIONS: Adding a thoracic epidural block to isoflurane/nitrous oxide anaesthesia during one-lung ventilation for lung resections does not result in clinically relevant detrimental effects on intraoperative oxygenation.     

A comparison of thiopentone/isoflurane anaesthesia vs propofol infusion in children having repeat minor haematological procedures

We have performed a randomized, cross over study in 22 children suffering from acute leukaemia, who underwent repeated anaesthesia for bone marrow aspiration and lumbar puncture. For their first anaesthetic, the children (aged 3–10 years old) received, either a thiopentone/isoflurane anaesthetic or intravenous propofol, both supplemented with nitrous oxide. On a second occasion they received the alternative technique. Of those children receiving thiopentone/isoflurane, 32% had significant coughing during anaesthesia, two progressing to laryngospasm requiring 100% oxygen. None of the patients receiving propofol had a respiratory disturbance ( P =0.016). 68% of the children preferred the propofol anaesthetic. Only one child in the thiopentone/isoflurane group preferred this technique. Twenty-seven per cent had no preference. There was no significant difference in length of anaesthetic time ( P =0.07) or the time taken for recovery ( P =0.17) between the two groups. There was a large individual variation in propofol requirements and movement was common during stimulation of patients in this group, though this did not adversely affect the surgical procedure.     

Closed loop control of anaesthesia: an assessment of the bispectral index as the target of control

We investigated the performance of a closed-loop system for administration of general anaesthesia, using the bispectral index as a target for control. One hundred patients undergoing gynaecological or general surgery were studied. In 60 patients, anaesthesia was maintained by intravenous infusion of a propofol/alfentanil mixture. In 40, an isoflurane/nitrous oxide based technique was used. For each technique, patients were randomly allocated to receive either closed-loop or manually controlled administration of the relevant agents (propofol/alfentanil or isoflurane), with an intra-operative target bispectral index of 50 in all cases. Closed-loop and manually controlled administration of anaesthesia resulted in similar intra-operative conditions and initial recovery characteristics. During maintenance of anaesthesia, cardiovascular and electro-encephalographic variables did not differ between closed-loop and manual control groups and deviation of bispectral index from the target value was similar. Intra-operative concentrations of propofol, alfentanil and isoflurane were within normal clinical ranges. Episodes of light anaesthesia were more common in the closed-loop group for patients receiving propofol/alfentanil anaesthesia and in the manual group for patients receiving isoflurane/nitrous oxide anaesthesia. Convenience aside, the closed-loop system showed no clinical advantage over conventional, manually adjusted techniques of anaesthetic administration.     

A comparison between isoflurane and alfentanil supplemented anaesthesia for short procedures

Sixty unpremedicated patients undergoing short urological and gynaecological procedures were randomly allocated to three groups to receive either methohexitone, alfentanil, nitrous oxide and oxygen, methohexitone, isoflurane and oxygen or methohexitone, isoflurane, nitrous oxide and oxygen. The group receiving methohexitone, isoflurane and oxygen was abandoned after 11 patients had been studied, due to poor conditions during induction of anaesthesia. Therefore, data from only 51 patients are presented. Early recovery was assessed by time to opening eyes, giving correct name and date of birth; later, recovery was assessed by using the postbox test and deletion of 'p's. During anaesthesia and surgery, there was a high incidence of coughing and laryngospasm in the isoflurane groups. The patients in the alfentanil group opened their eyes and gave their names and dates of birth significantly faster postoperatively (p less than 0.01) than those in the isoflurane groups. However, there were no significant differences between the three groups regarding the later tests of recovery. The late recovery after isoflurane was equal to that obtained using an intravenous technique with alfentanil, although the peroperative complication rate was higher.     

Recovery from propofol infusion as the main agent for outpatient arthroscopy

Propofol by continuous intravenous infusion has been compared with isoflurane as the main anaesthetic agent for outpatient arthroscopy of the knee. In 40 unpremedicated patients, anaesthesia was induced with propofol 2 mg/kg and vecuronium bromide 0.1 mg/kg and maintained after tracheal intubation with nitrous oxide 66% in oxygen. One group received 3% isoflurane prior to intubation and 0.9% during maintenance, while the other received a continuous intravenous infusion of propofol at a rate of 10 mg/kg/hour. Recovery was assessed by the time to opening eyes, to be able to answer five questions correctly, to recovery of ocular balance (Maddox Wing test) and by comparing pre- and postoperative performance in a paper and pencil test (the p-deletion test). After 3 hours all the patients were fit for discharge. Recovery tests showed no differences between the groups. All patients were satisfied with the anaesthesia. Full recovery took on average 1.5 days (range between 1 hour and 14 days) in both groups. Patients' opinion 1 month after the procedure should be included in every study concerning recovery. Anaesthesia by continuous propofol infusion results in quick recovery comparable with that following isoflurane anaesthesia.     

A comparison of remifentanil and fentanyl in patients undergoing carotid endarterectomy

BACKGROUND AND AIM: We investigated the haemodynamic stability and emergence characteristics of isoflurane/nitrous oxide anaesthesia supplemented with remifentanil or fentanyl in patients undergoing carotid endarterectomy. METHODS: Anaesthesia was induced with propofol (1-2 mg kg-1) and either remifentanil (0.5 microgram kg-1) or fentanyl (1 microgram kg-1), followed by an infusion of remifentanil (0.2 microgram kg-1 min-1) or fentanyl (2 micrograms kg-1 h-1). RESULTS: There were no significant differences between the groups in haemodynamic variables, postoperative pain, nausea or vomiting. After induction there was a significant decrease in mean arterial pressure for both groups (P < 0.001) and a decrease in heart rate (P = 0.001) in the remifentanil group. In both groups these haemodynamic changes continued during maintenance of anaesthesia (P < 0.05). The time to eye opening after surgery was significantly shorter with remifentanil compared with fentanyl (6.62 +/- 3.89 vs. 18.0 +/- 15.18 min, P = 0.015). CONCLUSION: Remifentanil appears to be a comparable opioid to fentanyl when supplementing isoflurane/nitrous oxide anaesthesia for carotid endarterectomy.     

Effects of a single pre-operative dexmedetomidine dose on isoflurane requirements and peri-operative haemodynamic stability

In a double-blind, placebo-controlled study we investigated the effect of a single pre-induction intravenous dose of dexmedetomidine 2 μg.kg⁻¹ on anaesthetic requirements and peri-operative haemodynamic stability in 50 patients undergoing minor orthopaedic and general surgery. Patients were anaesthetised with nitrous oxide/oxygen/fentanyl, supplemented if necessary with isoflurane. The mean (SD) intra-operative isoflurane concentration was lower in the dexmedetomidine-treated patients than controls (0.01 (0.03)% compared to 0.1 (0.1)%; p = 0.001) although six of the 25 treated patients required isoflurane at some stage. The haemodynamic response to tracheal intubation and extubation was reduced in the dexmedetomidine group as was intra-operative heart rate variability; postoperative analgesic and anti-emetic requirements and peri-operative serum catecholamine concentrations were lower in the dexmedetomidine group. Hypotension and bradycardia occurred more frequently after dexmedetomidine.     

Nitrous oxide anaesthesia and vomiting

Eighty-seven patients undergoing routine laparoscopy were divided randomly into two groups to study the effect of nitrous oxide anaesthesia on the incidence of postoperative vomiting. Patients in group A received nitrous oxide as part of their anaesthetic, while in group B nitrous oxide was omitted. Significantly fewer patients in group B vomited when compared with group A (17 percent and 49 percent respectively; p less than 0.005). We suggest that an anaesthetic technique which avoids nitrous oxide may be especially indicated in patients undergoing laparoscopy.     

A prospective study of liver function in infants and children exposed to daily isoflurane for several weeks

Eleven infants and children presenting for daily radiotherapy for a period of at least 2 weeks were anaesthetised with isoflurane in 33% oxygen and nitrous oxide. They were unpremedicated and given no other agents to supplement anaesthesia. The average number of exposures was 24 (SD 11; range 10-39) and the total anaesthetic time per exposure varied between 15 and 30 minutes. Liver function was assessed by determining serum total bilirubin, aspartate amino transferase, gamma glutamyl transferase and alkaline phosphatase before the start of treatment and at 5-daily intervals thereafter. There was no measurable change in any of these determinants of liver function. All children accepted daily induction of anaesthesia with isoflurane. Induction, maintenance and recovery from anaesthesia were uncomplicated.     

The effects of nitrous oxide on the auditory evoked potential index during sevoflurane anaesthesia

We have studied the effects of nitrous oxide on the auditory evoked response index (AAI-index) derived from the A-line monitoring device during sevoflurane anaesthesia in 21 patients undergoing minor ambulatory surgery. During sevoflurane anaesthesia with an AAI-index < 30, the addition or withdrawal of nitrous oxide in a concentration of 66% end tidal did not show any linear dose dependent change in AAI-index . However, comparing nitrous oxide > 40% to nitrous oxide < 10% end tidal concentration the AAI-index did decrease, p < 0.05. The AAI-index is either non-linear at deeper anaesthetic levels or is insensitive to the anaesthetic effects of nitrous oxide in terms of MAC-multiples.     

A randomised controlled trial of paediatric conscious sedation for dental treatment using intravenous midazolam combined with inhaled nitrous oxide or nitrous oxide/sevoflurane

Failure of dental treatment due to anxiety is a common problem in children. The aim of this study was to establish whether the use of a combination of intravenous midazolam with inhalation agents (nitrous oxide alone or in combination with sevoflurane) was any more likely to result in successful completion of treatment than midazolam alone. A further aim was to evaluate the clinical viability of these techniques as an alternative to general anaesthesia. In total, 697 children too anxious for management with relative analgesia and requiring invasive dental procedure for which a general anaesthetic would usually be required, were recruited and randomly assigned to one of three groups given the following interventions: group 1 - a combination of inhaled medical air and titrated intravenous midazolam, group 2 - a combination of inhaled 40% nitrous oxide in oxygen and titrated intravenous midazolam, and group 3 - a combination of an inhaled mixture of sevoflurane 0.3% and nitrous oxide 40% in oxygen with titrated intravenous midazolam. The primary outcome measure was successful completion of the intended dental treatment with a co-operative child responsive to verbal commands. In group 1, 54% (94/174 children) successfully completed treatment. In group 2, 80% (204/256 children) and in group 3, 93% (249/267 children) completed treatment. This difference was significant at the 1% level. Intravenous midazolam, especially in combination with inhaled nitrous oxide or sevoflurane and nitrous oxide, are effective techniques, with the combination of midazolam and sevoflurane the one most likely to result in successful treatment.     

Comparison of sevoflurane and nitrous oxide mixture with nitrous oxide alone for inhalation conscious sedation in children having dental treatment: a randomised controlled trial

We studied 411 children aged 3-10 years who were referred for dental treatment. They were randomly allocated to have inhalation conscious sedation with either sevoflurane/nitrous oxide mixture or nitrous oxide alone. Dental treatment was satisfactorily completed in 215/241 children who were given sevoflurane/nitrous oxide mixture (89%) compared with 89/170 who were given nitrous oxide alone (52%) (Chi square 70.3, p < 0.0001). All children remained conscious and responsive to verbal contact throughout the treatment and in the recovery room. No adverse side-effects were recorded in either group and there were no significant differences in oxygen saturation, heart rate, recovery profile, or time to discharge home between the groups. The study concluded that, for every 100 children treated with sevoflurane/nitrous oxide mixture, 37 children would be saved a general anaesthetic if given combined sevoflurane and nitrous oxide mixture rather than nitrous oxide alone. The use of sevoflurane in low concentrations 0.1-0.3% to supplement nitrous oxide and oxygen for inhalation conscious sedation is safe, practical, and significantly more effective than nitrous oxide alone in children having dental treatment.     

Effect of isoflurane and sevoflurane on the magnitude and time course of neuromuscular block produced by vecuronium, pancuronium and atracurium

We have compared the ability of equipotent concentrations of isoflurane and sevoflurane to enhance the effect of non-depolarizing neuromuscular blocking drugs. Ninety ASA I and II patients of both sexes, aged 18-50 yr, were stratified into three blocker groups (Vec, Pan and Atr), to undergo neuromuscular block with vecuronium (n = 30), pancuronium (n = 30) or atracurium (n = 30), respectively. Within each group, patients were allocated randomly to one of three anaesthetic subgroups to undergo maintenance of anaesthesia with: (1) alfentanil-nitrous oxide- oxygen (n = 10); (2) alfentanil-nitrous oxide-oxygen-isoflurane (n = 10); or (3) alfentanil-nitrous oxide-oxygen-sevoflurane (n = 10) anaesthesia. During maintenance of anaesthesia, end-tidal concentrations of isoflurane, sevoflurane and nitrous oxide were 0.95, 1.70 and 70%, respectively. Both the evoked integrated electromyogram and mechanomyogram of the adductor pollicis brevis muscle were measured simultaneously. In the Vec and Pan groups, a total dose of 40 micrograms kg-1 of vecuronium or pancuronium, respectively, was given, and in the Atr group a total dose of atracurium 100 micrograms kg-1. Each blocker was given in four equal doses and administered cumulatively. We showed that 0.95% isoflurane and 1.70% sevoflurane (corresponding to 0.8 MAC of each inhalation anaesthetic, omitting the MAC contribution of nitrous oxide) augmented and prolonged the neuromuscular block produced by vecuronium, pancuronium and atracurium to a similar degree.      

Anaesthesia and the QT intervalEffects of isoflurane and halothane in unpremedicated children

The effects of isoflurane and halothane on the QT interval were investigated during induction of anaesthesia. Fifty-one unpremedicated, ASA grade 1 children were studied. Anaesthesia was induced with either isoflurane ( n  = 25) or halothane ( n  = 26) and was maintained to the end of the study with end-tidal concentrations of between 2.5% and 3%. Recordings of the electrocardiograph, heart rate and systolic arterial pressure were obtained at the following times: before induction of anaesthesia; 1 min and 3 min after stable end-tidal concentrations of anaesthetic agent had been reached; 1 min and 3 min following vecuronium administration; at the time of tracheal intubation and 1 min and 3 min later. Isoflurane significantly prolonged the QT interval (p < 0.001), in contrast to halothane which shortened it (p < 0.01). Heart rate remained largely unchanged during isoflurane anaesthesia but it decreased in the presence of halothane (p < 0.001). In both groups, systolic arterial pressure decreased significantly after induction of anaesthesia (p < 0.001) and remained so to the end of the study. In the isoflurane group, 12 children developed ECG repolarisation abnormalities and in one child an arrhythmia was noticed. In the halothane group, one child developed repolarisation changes while arrhythmias were observed in 10 children. There were no adverse sequelae. It is concluded that halothane may be a better anaesthetic agent than isoflurane for use in children with a prolonged QT interval.     

Alfentanil v. isoflurane for outpatient arthroscopy

Alfentanil by continuous intravenous infusion and isoflurane have been compared as anaesthetic agents for outpatient arthroscopy. In 42 patients, divided at random into two groups, anaesthesia was induced with methohexitone and vecuronium bromide, and, after intubation, maintained with nitrous oxide 66% in oxygen combined with alfentanil or isoflurane. Alfentanil was given before intubation (1 mg), as a loading dose before starting surgery (50 micrograms kg-1) and by a continuous infusion at a rate of 1 microgram kg-1 min-1. Isoflurane was given in a concentration of 0.9% as a maintenance dose. Awakening from anaesthesia was more rapid with alfentanil than with isoflurane. Recovery tests were applied in the recovery room. Both anaesthetic techniques provided satisfactory anaesthesia and rapid recovery. All patients but one were content with the anaesthesia. The patients who received isoflurane scored better in the recovery tests in the first 3 h, but after 3 h there was no difference between the groups. The alfentanil group showed a higher incidence of nausea and/or vomiting: 45% compared to 14% in the isoflurane group.     

The effect of nitrous oxide on cerebral blood flow velocity in children anaesthetised with sevoflurane

To determine the effects of nitrous oxide on middle cerebral artery blood flow velocity (CBFV) during sevoflurane anaesthesia in children, CBFV was measured using transcranial Doppler sonography in 16 ASA I or II children. Anaesthesia consisted of 1.0 MAC sevoflurane in 30% oxygen with intermittent positive pressure ventilation maintaining FEco2 at 38 mmHg (5.0 kPa) and a caudal epidural block using 0.25% bupivacaine 1.0 ml.kg-1. The remainder of the inspired gas was varied in one of two sequences either air/nitrous oxide/air or nitrous oxide/air/nitrous oxide. The results showed that CBFV decreased when nitrous oxide was replaced by air (p = 0.03) and returned to its initial value when nitrous oxide was reintroduced. CBFV increased when air was replaced by nitrous oxide (p = 0.04) and returned to its initial value when air was reintroduced. Mean heart rate and blood pressure remained constant. We conclude that nitrous oxide increases cerebral blood flow velocity in healthy children anaesthetised with 1.0 MAC sevoflurane.     

Recovery from sufentanil anaesthesia for outpatient arthroscopy: a comparison with isoflurane

This study compares the recovery from sufentanil and isoflurane anaesthesia in patients undergoing outpatient arthroscopy of the knee under general anaesthesia. In 40 unpremedicated patients, divided at random into two groups, anaesthesia was induced with methohexitone and vecuronium bromide and, after intubation, maintained with nitrous oxide 66% in oxygen supplemented with sufentanil or isoflurane. Patients in Group A received sufentanil (1 microgram/kg) at induction and if necessary an incremental dose of 10 micrograms. Patients in Group B received 3% isoflurane prior to intubation and 0.9% during maintenance. Awakening from anaesthesia was more rapid with sufentanil than isoflurane. Recovery was assessed from the time patients took to open their eyes, to give correct answers to five questions and to recover from ocular imbalance. (Maddox wing test), and by comparing pre- and postoperative performance of a paper and pencil test (the p-deletion test). After 2 h, there was no difference between the two groups. Both anaesthetic techniques provided satisfactory operating conditions, but the sufentanil group showed a higher incidence of nausea and vomiting (45%) than the isoflurane group (15%).     

The use of nitrous oxide in anaesthetic practice: a questionnaire survey

Where practicable, exposure to a hazardous substance should be eliminated or adequately controlled. A postal questionnaire survey was sent to 10% of consultants from the Association of Anaesthetists of Great Britain and Ireland, to identify the level of use of nitrous oxide in current anaesthetic practice and identify any change of practice over the last 5 years. Details of anaesthetic practice were requested in three areas: nitrous oxide usage, availability of medical air on anaesthetic machines and the use of total intravenous anaesthesia. Replies were received from 320 consultants (75%). Of these, 49% felt that, over the last 5 years, their use of nitrous oxide had decreased. Twenty per cent of anaesthetists felt that there should be some restriction in availability of nitrous oxide. Where medical air was available, 32% felt that they would use it frequently. A total of 263 (83%) stated that they use total intravenous anaesthesia to some extent. The results showed that, although 49% of consultant anaesthetists had reduced their use of nitrous oxide, this was due to medical considerations rather than concerns over health and pollution issues arising from the use of nitrous oxide.     

Pediatric surgery. A comparison of spinal anesthesia and general anesthesia]

Forty patients aged 2 to 5 years who were admitted for paediatric operations were randomly assigned to have either spinal or general anaesthesia. Spinal anaesthesia was achieved with isobaric bupivacaine 0.5% at a dose of 0.5 mg/kg. General anaesthesia was induced with thiopentone 2-5 mg/kg and continued with low-dose fentanyl (1-2 micrograms/kg, oxygen/nitrous oxide/isoflurane (30/70/0.1-0.5%), vecuronium normoventilating the patients. The time spent in the operation room was shorter in the spinal anaesthesia group because the children were awake and could immediately be transferred. The haemodynamic pattern and respiratory function were stable during spinal anaesthesia. After general anaesthesia, respiratory function deteriorated as indicated by arterial desaturation (< 90%), which was detected in 11 of the 20 patients after general anaesthesia. Vomiting (2), sore throat (4) and micturition difficulties (2) were the adverse events associated with general anaesthesia. Three patients were restless after spinal anaesthesia. It can be concluded that spinal anaesthesia is a suitable anaesthetic technique for paediatric surgery.     

Nitrous oxide does not increase nausea and vomiting following gynaecological laparoscopy

The effect of three different anaesthetic techniques on the incidence and severity of postoperative emesis (nausea, retching and vomiting) was studied in 150 patients undergoing gynaecological laparoscopy. Patients were anaesthetized with isoflurane in nitrous oxide and oxygen (Group A), enflurane in nitrous oxide and oxygen (Group B) or with isoflurane in air and oxygen (Group C). Groups had been predetermined by date of birth. During the first 24 hours after the operation no difference was found at any time in the incidence or severity of emesis among the groups. The overall incidence of emesis during the first 24 hours postoperatively was 54, 48 and 52 per cent, in groups A, B and C, respectively. It is concluded that nitrous oxide does not increase the incidence of emesis after isoflurane anaesthesia and that isoflurane and enflurane anaesthesia are associated with similar incidences of nausea and vomiting after gynaecological laparoscopy.