Comparison of the effects of ketamine-midazolam with those of fentanyl- midazolam on cortical somatosensory evoked potentials during major spine surgery

Cortical somatosensory evoked potentials (CSEP) allow monitoring of spinal cord function during surgery. Ketamine has been shown to enhance CSEP amplitude, but there is no previous study comparing its effects with those of other anaesthetic regimens. Therefore, we have compared the effects of ketamine with those of fentanyl, both combined with midazolam, on CSEP monitoring during major spine surgery. Twenty patients with normal preoperative CSEP were allocated randomly to a ketamine or fentanyl group. Anaesthesia was induced with ketamine 3 mg kg-1 or fentanyl 6 micrograms kg-1 i.v., and midazolam 0.3 mg kg-1 i.v in both groups, and maintained with continuous i.v infusion of ketamine 2 mg kg-1 h-1 or fentanyl 3 micrograms kg-1 h-1, combined in both groups with midazolam 0.15 mg kg-1 h-1 and 60% nitrous oxide in oxygen. CSEP were elicited by tibial posterior nerve stimulation and measured P1 and N1 latencies, and P1-N1 amplitude, CSEP were recorded before and after induction, at 15 min, 1 and 2 h after induction, during skin closure and after removal of nitrous oxide. Both groups were comparable in characteristics, duration of surgery, mean arterial pressure and temperature. CSEP latencies were not significantly affected in either group. CSEP amplitude decreased significantly over time in the fentanyl group (from mean 2.02 (SEM 0.41) to 0.95 (0.17) microV, P < 0.05), but not in the ketamine group (from 1.33 (0.36) to 1.05 (0.31) microV, ns). Nevertheless, we did not observe any significant differences in amplitudes or latencies between the two groups. The delay in obtaining the first voluntary postoperative motor response was significantly greater in the ketamine group (170 (54) vs 55 (17) min, P < 0.01). Both ketamine and fentanyl allowed us to obtain reliable CSEP during major spine surgery, and there were no significant difference between these two anaesthetic regimens for CSEP monitoring, but a longer delay for voluntary postoperative motor assessment was observed in the ketamine group.      

Small doses of remifentanil or sufentanil for blunting cardiovascular changes induced by tracheal intubation: a double-blind comparison

BACKGROUND AND OBJECTIVE: To compare the effects on cardiovascular changes induced by tracheal intubation when small doses of either remifentanil or sufentanil are used in the presence of midazolam. METHODS: Thirty normotensive, ASA physical status I-II patients, receiving general anaesthesia for major abdominal surgery, received an intravenous midazolam premedication (0.05 mg kg-1) 10 min before induction. They were randomly allocated to receive in a double-blind fashion an intravenous bolus of either (a) remifentanil given as a bolus dose 1 microgram kg-1 (n = 15), or else (b) sufentanil 0.1 microgram kg-1 infused over 60 s (n = 15). In each instance this loading dose was followed by a continuous intravenous infusion (0.1 microgram kg-1 min-1 or 0.01 microgram kg-1 min-1 of remifentanil or sufentanil, respectively). General anaesthesia was induced with propofol (2 mg kg-1), followed by atracurium besilate (0.5 mg kg-1) to facilitate tracheal intubation. Following intubation, the lungs were mechanically ventilated with a 60% nitrous oxide in oxygen mixture and a 1% inspired sevoflurane. RESULTS: Arterial pressure and heart rate were recorded before induction of anaesthesia (baseline), immediately before intubation, immediately after tracheal intubation and every minute for the first five minutes thereafter. No differences in systolic and diastolic arterial pressures were observed between the two groups. At the end of the study period, systolic and diastolic pressures slightly decreased from preinduction values in both groups. Four patients in the remifentanil group (26%) and five patients in sufentanil group (33%) showed at least one systolic pressure value < 90 mmHg during the study period (P = not significant); however, the observed decreases in systolic pressure were transient and did not require treatment. Heart rate values were not affected by tracheal intubation in either group. CONCLUSIONS: In healthy normotensive patients without cardiovascular disease the use of a relatively small dose of either remifentanil or sufentanil after standard midazolam premedication results in a similar and clinically acceptable effectiveness in blunting the cardiovascular changes induced by tracheal intubation.     

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 propofol and isoflurane on the neuromuscular block induced by atracurium]

Speed of onset, duration of action and recovery time for a bolus injection of atracurium were measured in two groups of patients. In group I anaesthesia considered of propofol, fentanyl, nitrous oxide and oxygen mixture. The induction dose of propofol was 2 mg/kg-1 followed by an infusion of 9.0 mg/kg-1/h-1 for first half hour and 4.5 mg/Kg-1/h-1 subsequently. In group II anaesthesia consisted of isoflurane, fentanyl, nitrous oxide and oxygen mixture. Isoflurane was given upon clinical needs. Speed of onset, duration of action, and recovery time for atracurium were measured in the two groups. No statistically significant differences between speed of onset and duration of action between the two groups were found. The recovery period from T1 = 10% to T1 = 70% twitch response was considerably longer with isoflurane (25 min +/- 6) than with propofol (18 min +/- 3) (p less than 0.01). Results obtained suggest that for adequate relaxation during tracheal intubation smaller doses of atracurium are not needed during isoflurane than propofol administration. Because of the longer recovery period of residual neuromuscular blockade during isoflurane anaesthesia decreasing doses of atracurium and careful monitoring of twitch depression tension are also suggested.     

Maintenance of anaesthesia with propofol--a comparative study of a stepdown infusion of propofol and a low dose infusion supplemented by incremental doses.

Forty-four patients, ASA Grade I or II, had anaesthesia induced with propofol at 100 mg min-1 followed by a maintenance rate of 6 mg kg-1 h-1 or a stepdown regimen of 10 mg kg-1 h-1 for 10 min, 8 mg kg-1 h-1 for the next 10 min and at 6 mg kg-1 h-1 thereafter. Anaesthesia was maintained with propofol infused using an Ohmeda 9000 pump supplemented by nitrous oxide and oxygen (2:1) in a Bain circuit with spontaneous ventilation. Incremental doses of 20 mg of propofol were given to both groups as clinically indicated to maintain anaesthesia. Both methods provided satisfactory maintenance of anaesthesia but significantly more incremental doses were required in the group receiving the steady rate infusion. However, a lower cumulative dose was required up to 30 min in this group but not by 40 min. A comparable fall in systolic and diastolic blood pressure and heart rate was seen in both groups. There was no difference in the recovery times between the groups and the total dose did not correlate with time to recovery.     

Effect of total intravenous anaesthesia with midazolam/alfentanil on the adrenocortical and hyperglycaemic response to abdominal surgery

The effect of anaesthesia on the hyperglycaemic and adrenocortical response induced by surgery was studied in patients undergoing abdominal hysterectomy. The study group was anaesthetized with midazolam and alfentanil using a totally intravenous anaesthetic technique. A reference group received anaesthesia with thiopentone, alfentanil and nitrous oxide. Midazolam 0.42 mg.kg-1 was given as a loading infusion followed by a maintenance infusion of 0.125 mg.kg-1.h-1. Alfentanil was given as a bolus dose of 0.075 mg.kg-1 in both groups, followed by a loading infusion of 0.3 mg.kg-1.h-1 for 15 min and a maintenance infusion of 0.065 mg.kg-1.h-1. Increments of alfentanil were given whenever heart rate or systolic blood pressure exceeded pre-induction values by more than 10%. During anaesthesia mean arterial pressure and heart rate were similar in both groups and there was no difference in alfentanil requirement. An immediate increase in blood glucose concentrations was seen following incision, but maximum concentrations were measured in the early postoperative period. Serum cortisol concentrations decreased after induction of anaesthesia. During surgery they returned to pre-induction values, and in the postoperative period they increased to about twice the pre-induction values. It is concluded that midazolam/alfentanil anaesthesia is as effective as anaesthesia induced by thiopentone, alfentanil and nitrous oxide in suppressing the stress-response to surgery until the postoperative period. No signs of prolonged adrenocortical depression were observed.     

Flumazenil and peroperative awakening in surgery of scoliosis

Motor and sensory function must be assessed during surgery of scoliosis so as to avoid possible damage to the spinal cord. The intraoperative awakening by a specific benzodiazepine antagonist, flumazenil, was studied prospectively in 20 patients (mean age 17 years) undergoing surgery for severe scoliosis. Premedication consisted in 0.02 mg.kg-1 atropine and 0.15 mg.kg-1 midazolam. Anaesthesia was induced with a mean dose of 0.42 +/- 0.1 mg.kg-1 midazolam, 1.6 +/- 0.6 micrograms.kg-1 fentanyl and 0.1 mg.kg-1 pancuronium. Maintenance was obtained with a continuous infusion of 0.22 +/- 0.1 mg.kg-1.h-1 midazolam, 66% nitrous oxide in oxygen, and fentanyl (1.6 +/- 0.5 micrograms.kg-1.h-1). Nitrous oxide and midazolam were respectively stopped 10 and 1 min before giving the antagonist (5 micrograms.kg-1 flumazenil) if required (17 out of the 20 patients). Eye opening occurred a mean 42 +/- 32 s after giving the antagonist. At this time, there was a significant increase in mean arterial blood pressure (+ 11 mmHg) and heart rate (+ 7 b.min-1). Thiopentone, 66% nitrous oxide in oxygen and 0.5% halothane were given to re-induce and maintain anaesthesia for completion of the procedure. The day following surgery, 19 patients were unable to remember the period of intraoperative awakening. One patient, although remembering the episode, did not experience any pain or any other disagreement in relation to it. Two patients were given a second dose of flumazenil at extubation so as to improve the quality of their recovery.(ABSTRACT TRUNCATED AT 250 WORDS)     

Propofol auto-co-induction as an alternative to midazolam co-induction for ambulatory surgery

We propose the use of an intravenous propofol/propofol auto-co-induction technique as an alternative to propofol/midazolam for induction of anaesthesia. We have studied 54 unpremedicated ASA 1 or 2 patients undergoing day-stay anaesthesia for minor orthopaedic surgery. All received 10 micrograms.kg-1 or alfentanil before induction, followed by either midazolam 0.05 mg.kg-1, propofol 0.4 mg.kg-1 or saline, and 2 min later, a propofol infusion at a rate of 50 mg.kg-1.h-1 until loss of eyelash reflex. We compared pre- and postinduction haemodynamic changes, complications at insertion of a laryngeal mask airway and recovery from anaesthesia in the three groups. Both co-induction techniques showed less postinduction hypotension and significant reduction of the total induction dose of propofol when compared to the control group. In the propofol/propofol group there was a decreased incidence of apnoea during induction of anaesthesia. These patients were discharged from hospital 2 h after the end of anaesthesia whereas patients in the midazolam/propofol group were discharged after 2 1/2 h (p < 0.001).     

Recovery and discharge of patients after long propofol infusion vs isoflurane anaesthesia for ambulatory surgery

Fifty unpremedicated patients scheduled for outpatient restorative dentistry and/or oral surgery lasting 2 to 4 h were anaesthetized with either propofol infusion or isoflurane inhalation. Before induction of anaesthesia with propofol (2.5 mg.kg-1), all patients were given 75 mg of diclofenac and 0.01 mg.kg-1 vecuronium intravenously. Intubation was facilitated with suxamethonium (1.5 mg.kg-1) and anaesthesia was maintained in random order either with propofol infusion (12 mg.kg-1.h-1 for the first 20 min, 9 mg.kg-1.h-1 for the next 20 min, and 6 mg.kg-1.h-1 for the rest of the anaesthesia) or with isoflurane (inspired concentration 1-2.5%), both with nitrous oxide and oxygen (30%). The patients breathed spontaneously using a non-rebreathing circuit. Patients given propofol infusion became re-orientated faster (11.0 +/- 5.5 min vs. 16.5 +/- 7.5 min; P less than 0.01) and at 30 min walked along a straight line better (P less than 0.01). At 60 min, none of the propofol patients displayed an unsteady gait, whereas 11 of the 25 isoflurane patients did (P less than 0.001). None of the patients receiving propofol had emesis at the clinic, compared with 10 of the 25 patients receiving isoflurane (P less than 0.001). The overall incidence of emesis was 2 of 25 and 14 of 25 in the propofol and isoflurane groups, respectively (P less than 0.01). Patients receiving propofol were discharged home earlier than patients receiving isoflurane (80 +/- 14 min and 102 +/- 32 min, respectively; P less than 0.01). It is concluded that propofol allows early discharge of patients, even after long anaesthesias.     

Structured sedation programme for magnetic resonance imaging examination in children

One thousand, eight hundred and fifty-seven patients underwent magnetic resonance imaging following the establishment of a structured sedation programme. Forty-eight of these patients came from the intensive care unit with a secure airway and were therefore excluded from any further analysis. Oral sedation was to be given to children aged 5 years and below. For children >/= 6 years old, oral sedation could be given only if their level of co-operation was judged to be inadequate by the referring physician. Oral sedation consisted of chloral hydrate 90 mg x kg-1 (maximum 2.0 g) orally with or without rectal paraldehyde 0.3 ml x kg-1. All magnetic resonance imaging requests for children who failed oral sedation as well as those referred for general anaesthesia from the outset were reviewed by a consultant anaesthetist who then allocated patients to undergo the procedure with either general anaesthesia or intravenous sedation. Scans requiring intravenous sedation or general anaesthesia were performed in the presence of a consultant anaesthetist. Intravenous sedation consisted of either a propofol 0.5 mg x kg-1 bolus followed by an infusion (maximum 3 mg x kg-1 x h-1) or midazolam 0.2-0.5 mg x kg-1 boluses. General anaesthesia was given using spontaneous ventilation with a mixture of 66% nitrous oxide in oxygen and isoflurane following either inhalation (sevoflurane) or intravenous (propofol) induction. One thousand and thirty-nine (57.4%) of the scans were done without sedation whereas 93 scans were performed during the consultant anaesthetist supervised sessions. Oral sedation failed in 50 out of 727 patients (6.9%). Eighty-seven per cent of children aged 5 years and below needed sedation compared with 4.5% of those aged over 10 years. Two patients who had only received chloral hydrate developed significant respiratory depression. This structured sedation programme has provided a safe, effective and efficient use of limited resources.     

Ambulatory anesthesia and induced abortion. Comparative study of propofol-alfentanyl and ketamine-midazolam combinations

The use of propofol alone or with alfentanil in the day-case anaesthesia for abortion was compared with that of ketamine with midazolam. Two hundred young women were assigned to two successive series of two groups each. The four groups were: group 1 (2 mg . kg-1 propofol only); group II (0.5 mg . kg-1 ketamine with 0.25 mg . kg-1 midazolam); group III (2 mg . kg-1 propofol with 4 micrograms . kg-1 alfentanil); group IV (1 mg . kg-1 ketamine with 0.1 mg . kg-1 midazolam). All the patients were premedicated one hour before anaesthesia with 0.25 mg . kg-1 midazolam orally. All the patients were asleep at the end of the propofol injection (60 s), and 10 to 15 s later for the ketamine-midazolam groups. The haemodynamic parameters did not vary much during induction with ketamine-midazolam. In the propofol groups, the heart rate remained steady, with an 8 to 12% fall in blood pressure. A fall of the mandible was seen in 40 and 84% of the patients in the propofol groups, with a short apnoea in 32 and 48% of these same patients. Clinical recovery was very quick, less than 12 min for all groups. The four psychomotor and sensory tests were carried out at the 30th min by 95% of the patients in the propofol groups, whereas only 50% of those in the ketamine-midazolam groups did so. Speed and quality were significantly better in the propofol groups. The most frequent adverse effect of propofol was pain during injection in 32 and 14% of patients.(ABSTRACT TRUNCATED AT 250 WORDS)     

胸腔镜胸交感神经切断术病人舒芬太尼复合异丙酚麻醉的效果

目的 评价胸腔镜胸交感神经切断术病人舒芬太尼复合异丙酚麻醉的效果.方法 择期行胸腔镜胸交感神经切断术的手汗症病人20例,ASA Ⅰ或Ⅱ级,静脉注射舒芬太尼0.5 μg/kg、异丙酚2.0～2.5 mg/kg和阿曲库铵0.6 mg/kg麻醉诱导,麻醉维持:静脉输注舒芬太尼0.2～0.3 μg·kg-1·h-1、异丙酚2～4 mg·kg-1·h-1,间断静脉注射阿曲库铵0.3 mg/kg.手术结束前30 min舒芬太尼输注速率减至0.1 μg·kg-1·h-1,异丙酚减至1～2 mg·kg-1·h-1.分别于麻醉诱导前(基础状态)、气管插管时、CO2充气时、CO2充气5 min、30min、放气后5min、拔管时记录SP、DP、HR,并于上述时点采集静脉血样,测定血浆皮质醇、醛固酮和血糖浓度,记录自主呼吸恢复时间、呼之睁眼时间和拔管时间.结果 术中SP、DP和HR波动在正常范围内;与基础值比较,血浆皮质醇、醛固酮和血糖浓度升高(P＜0.05),自主呼吸恢复时间、呼之睁眼时间和拔管时间分别为4.5±1.9、6.4±2.7、(12.6±1.5)min.结论 胸腔镜胸交感神经切断术病人舒芬太尼0.1～0.3 μg·kg-1·h-1复合异丙酚1～4mg·kg-1·h-1麻醉能维持血液动力学的稳定,可减轻应激反应.     

Comparison of propanidid with propofol for dental surgery of short or medium duration

The properties of propofol in emulsion given by continuous intravenous infusion to spontaneously breathing patients have been well studied. Thirty randomized voluntary premedicated patients undergoing dental extraction were anaesthetized with propofol (2.5 mg X kg-1 IVD, and 9 mg X kg-1 X h-1) or with propanidid (9 mg X kg-1 IVD, and 60 mg X kg-1 X h-1), supplemented with nitrous oxide in oxygen and fentanyl. Induction, maintenance and recovery times had the same characteristics. Highly significant differences occurred between the two groups regarding the increase in heart rate, apnoea and recovery time. This study showed that propofol was an eminently suitable agent for continuous intravenous anaesthesia in spontaneously breathing patients for dental surgery.     

Comparison of propofol and propanidid administered at a constant rate

So as to compare the anaesthesia obtained using propofol with that obtained using propanidid, 40 ASA I patients, aged between 18 and 50 years, who were to undergo elective orthopaedic or plastic surgery lasting more than 60 min, were randomly divided into two equal groups, one receiving propofol (PF) and the other propanidid (PD). All the patients received 0.5 mg atropine, 100 mg pethidine and 7.5 mg droperidol (10 mg if weight greater than 60 kg) intramuscularly 45 min before induction. Patients in group PF were then given 2 mg.kg-1 propofol over 1 min and 0.9 microgram.kg-1 fentanyl over 3 min, followed by a constant rate infusion of 5 mg.kg-1.h-1 propofol and 3 micrograms.kg-1.h-1 fentanyl. For PD patients, the doses of fentanyl were identical; they were given 10.6 mg.kg-1 propanidid over 3 min for induction, and 37 mg.kg-1.h-1 for maintenance. All the patients were intubated and ventilated mechanically. The usual anaesthetic parameters were monitored at induction, during surgery, and during recovery. Consciousness was lost more quickly with propofol (p less than 0.05), but the corneal reflex returned more rapidly in group PD (p less than 0.02). The time required for a full return to normal consciousness was identical in both groups. The fall, during induction, and the increase, during recovery, of Pasys were greater in group PD (p less than 0.05 and less than 0.001 respectively). Padia and heart rate were lower in group PF after the 30th min (p less than 0.05 and less than 0.01 respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of propofol and methohexital for dental and maxillofacial surgery

A prospective study has been undertaken to compare a new intravenous anaesthetic agent, propofol, to methohexitone in 40 ASA I or II patients aged between 18 and 50 years undergoing maxillo-facial surgery and divided into two groups. Intramuscular premedication was standardized for all patients. In group I, propofol 2 mg X kg-1 was injected over 1 min in a peripheral venous line with fentanyl 0.86 microgram X kg-1, followed by an infusion of propofol 5 mg X kg-1 X h-1 and fentanyl 3 micrograms X kg-1 X h-1. In group II, the fentanyl dosage was the same as in group I, whilst methohexitone 3 mg X kg-1 was given for induction and 4.5 mg X kg-1 X h-1 for maintenance of anaesthesia. The following were recorded during induction, maintenance and recovery; haemodynamic parameters using a non invasive method; respiratory parameters; quality of anaesthesia; side-effects. Statistical analysis was performed using the Student t test and qualitative analysis using the Schwartz comparison test at 2%. The following results were found: the quality of anaesthesia with propofol was superior to that of methohexitone during the three stages of anaesthesia. The duration of induction was similar in both groups, but the quality of induction (occurrence of more minor side-effects; p less than 0.05) and intubation was in favour of propofol (p less than 0.05). During maintenance, stability of anaesthesia and a lesser incidence of side-effects were again in favour of the propofol group, in which a slower rate was also found (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Antagonism of benzodiazepine-fentanyl anaesthesia with flumazenil

The specific benzodiazepine antagonist flumazenil (Ro 15-1788) (Ro) was given in a double-blind study to 40 adult orthopaedic patients in order to determine if it shortens the immediate recovery time after benzodiazepine-fentanyl anaesthesia. On the evening before operation the patients were premedicated orally with 1-2 mg of flunitrazepam and 30 min before the induction of anaesthesia with 7.5 mg midazolam. Induction of anaesthesia was carried out with flunitrazepam 0.03-0.04 mg.kg-1 and fentanyl 0.1 mg IV. Anaesthesia was maintained with fentanyl (5.9 microgram.kg-1.h-1) and nitrous oxide. After the reversal of muscle relaxation, 20 patients received a placebo and 20 patients Ro, as boluses up to 10 ml, until the effect of awakening was noticed. The dose of Ro (0.1 mg.ml-1) required was 6.8 +/- 2.9 micrograms.kg-1 and that of placebo 10 +/- 0 ml. Patients given Ro woke up faster than patients given placebo. Ro patients were more alert than patients given placebo until 120 min after the injection or the test drug. After this patients in both groups behaved similarly. Eight patients given Ro and one given placebo showed some mild adverse reaction for 5-60 min after the administration of Ro or placebo (e.g., nausea, shivering). This study indicates that flumazenil speeds up awakening after benzodiazepine-fentanyl anaesthesia.     

Midlatency auditory evoked potentials and motor signs of wakefulness during anaesthesia with midazolam

We have studied midlatency auditory evoked potentials (MLAEP) and motor signs of wakefulness during anaesthesia with midazolam in 10 patients undergoing elective laparotomy under continuous extradural analgesia. Anaesthesia was induced with midazolam 0.3 mg kg-1 and maintained with midazolam 0.3-0.9 mg kg-1 h-1. Motor signs of wakefulness were documented as spontaneous movements and movements after simple commands (open eyes or move arms). MLAEP were recorded continuously awake, and during anaesthesia until the end of anaesthesia. Latencies of the peaks V, Na, Pa, Nb and P1 (ms) and amplitudes of the peaks Na/Pa, Pa/Nb and Nb/P1 (microV) were measured. Twenty-five movements were observed during anaesthesia; 15 movements in six patients were in response to commands. In two patients supplementary isoflurane was given. Latencies of the MLAEP peaks Pa, Nb and P1 increased slightly during anaesthesia. Amplitudes for Na/Pa, Pa/Nb and Nb/P1 did not change significantly. The high incidence of motor signs of wakefulness associated with preserved MLAEP indicated a high level of cortical neural activity and none of the MLAEP variables predicted movement during anaesthesia with midazolam.      

Propofol or halothane anaesthesia for children with asthma: effects on respiratory mechanics

Propofol may cause histamine release and alter airway tone and reactivity. Although its use has been reported to be safe in asthmatics, there is a lack of information on its effect on lung function in children with asthma. We measured respiratory mechanics after i.v. or inhalation anaesthesia in 60 children, aged 2-12 yr, with or without asthma. Anaesthesia was induced with propofol 3 mg kg-1, fentanyl 1 microgram kg-1 and atracurium 0.5 mg kg-1 and maintained with an infusion of propofol 10 mg kg-1h-1 and 50% nitrous oxide in oxygen. Halothane was administered subsequently at a concentration of 1 MAC. Respiratory mechanics were measured by applying a single- compartment model using multi-linear regression analysis to calculate dynamic compliance (Crs,dyn) and respiratory system resistance (Rrs), based on: Pao = V/Crs,dyn + V Rrs + PA,EE, where Pao = airway opening pressure, PA,EE = alveolar pressure, V = volume and V = flow. The two groups were comparable in age, weight and ventilation variables (tidal volume and peak pressure). Respiratory mechanics during propofol anaesthesia were comparable in normal and asthmatic children (Rrs = 20.5 X 10(-4) (SD 5.2 X 10(-4)) vs 21.5 X 10(-4) (5.7 X 10(-4)) kPa ml- 1 S-1 (ns) and Crs,dyn = 247.5 (76.51 vs 235.1 (63.8) ml kPa-1 (ns)). Halothane produced a minimal decrease in Rrs and a minimal increase in tidal volume in both groups without changes in Crs,dyn. In conclusion, respiratory mechanics were comparable after propofol anaesthesia in both children with and without asthma. Changes in Rrs after halothane administration were not clinically relevant.      

Desflurane maintains intraocular pressure at an equivalent level to isoflurane and propofol during unstressed non-ophthalmic surgery

We have investigated the effects of desflurane compared with isoflurane and propofol on intraocular pressure (IOP) in 48 ASA I-II patients undergoing elective non-ophthalmic surgery. Anaesthesia was induced with thiopental 3-5 mg kg-1, fentanyl 2-4 micrograms kg-1 and vecuronium 0.1 mg kg-1. Patients were allocated randomly to receive propofol (n = 16) 4-8 mg kg-1 h-1, isoflurane (n = 16) or desflurane (n = 16) for maintenance of anaesthesia. Fentanyl was added if necessary. The lungs were ventilated with 70% nitrous oxide in oxygen. Arterial pressure, electrocardiography, heart rate and end-tidal carbon dioxide were measured throughout anaesthesia. IOP was measured before surgery, during maintenance and after emergence from anaesthesia with applanation tonometry by an ophthalmologist blinded to the anaesthetic technique. There was a significant decrease in IOP after induction of anaesthesia which did not differ between groups. Desflurane maintained IOP at an equivalent level to isoflurane and propofol.      

Differential effects of nitrous oxide and propofol on myogenic transcranial motor evoked responses during sufentanil anaesthesia

We have compared the effects of 50% nitrous oxide and propofol, each administered concurrently with sufentanil, on the amplitudes and latencies of the compound muscle action potential (CMAP) response to transcranial electrical stimulation. Using a crossover design, 12 patients undergoing spinal surgery were exposed to both 50% nitrous oxide and propofol, the latter in a bolus-infusion regimen. Six patients received nitrous oxide first and six received propofol first. CMAP were recorded from the tibialis anterior muscle in response to both single and paired transcranial electrical stimuli. With single pulse stimulation, median CMAP amplitude was significantly greater during administration of nitrous oxide than propofol (nitrous oxide 335 (10th-90th percentiles 35-849) microV; propofol 36 (0-251) microV) (P < 0.01). With paired stimulation, there was no significant difference in CMAP amplitude during the two regimens (nitrous oxide 1031 (296-1939) microV; propofol 655 (0-1867) microV). The results indicate that propofol caused more depression of transcranial electrical motor evoked responses than 50% nitrous oxide but that the difference was probably clinically unimportant when a paired stimulation paradigm was used.