Clinical comparison of 'single agent' anaesthesia with sevoflurane versus target controlled infusion of propofol

Propofol-based total intravenous anesthesia decreases the incidence of postoperative nausea and vomiting without affecting flap survival in free flap breast reconstruction

Background

Postoperative nausea and vomiting (PONV) may cause undesirable effects after microsurgical breast reconstruction. Although total intravenous anesthesia (TIVA) with propofol has been demonstrated to be effective in reducing PONV, it has not been assessed in autologous free flap breast reconstruction. The purpose of this study was to investigate the antiemetic prophylaxis effect and safety of TIVA in microvascular breast reconstruction.

Methods

Eighty-three patients undergoing microsurgical breast reconstruction with propofol (31 patients) or sevoflurane (52 patients) were retrospectively reviewed. The incidence of PONV was assessed at 2, 6, and 24 hours after surgery. Mean arterial blood pressure (MAP) was compared at T₁ (after flap elevation but before transfer), T₂ (15 minutes after revascularization), and T₃ (at the end of surgery).

Results

The incidence of nausea was significantly reduced in the TIVA group over 0 to 2 hours period (P=0.017), and over 2 to 6 hours period (P=0.033). The incidence of vomiting was significantly reduced in the TIVA group over 0 to 2 hours period (P=0.006), and over 2 to 6 hours period (P=0.005). MAP was higher in the TIVA group at T₁ (P=0.018), T₂ (P=0.005), and T₃ (P=0.007). The incidence of flap failure was similar between the two groups (P=0.373).

Conclusions

Compared with sevoflurane maintaining anesthesia, propofol-based TIVA improves PONV with less fluctuation of MAP, and did not affect flap survival.

Comparative randomized study of propofol target-controlled infusion versus sevoflurane anesthesia for third molar extraction

Background

The objective of this study was to compare hemodynamic and recovery characteristics of total intravenous anesthesia using propofol target-controlled infusion (TCI) versus sevoflurane for extraction of four third molar teeth.

Methods

One hundred patients undergoing extraction of four third molar teeth under general anesthesia were randomized to one of two groups. Group 1 received propofol TCI-oxygen for induction and propofol TCI-oxygen-air for maintenance. Group II received a propofol bolus of 2 mg/kg for induction and sevoflurane-oxygen-air for maintenance. Heart rate, mean arterial pressure (MAP), operating time, time to emergence, nausea and vomiting, and sedation and pain scores were measured in each group.

Results

Demographic data, including age, gender, weight, and height, were not significantly different between the two groups. The MAP was significantly higher after intubation (P = 0.007) and injection of anesthesia (P = 0.004) in the propofol group than in the sevoflurane group, with significant reflex bradycardia (P = 0.028). The mean time to emergence from anesthesia using propofol was 25 s shorter than that of sevoflurane (P = 0.02). Postoperatively, the propofol group was less sedated than the sevoflurane group at 30 min (0.02 versus 0.12), but this difference was not significant (P = 0.065).

Conclusion

Both propofol TCI and sevoflurane are good alternatives for induction and maintenance of anesthesia for short day-case surgery. However, propofol TCI does not blunt the hemodynamic response to sudden, severe stimuli as strongly as sevoflurane, and this limitation may be a cause for concern in patients with cardiac comorbidities.

Elective cholecystectomy performed on patient with variegate porphyria-Propofol-based total intravenous anesthesia with target-controlled infusion

Porphyria is caused by disorders of enzymes that synthetize porphyrins. Both elective and emergency surgical procedures on patient suffering from porphyria may provoke acute symptoms. These patients require special anesthetic management since some of commonly used anesthetic agents may also induce acute manifestation of porphyria. We present the case of 53-year-old woman previously diagnosed with porphyria who underwent elective laparoscopic cholecystectomy. Propofol-based total intravenous anesthesia with target-controlled infusion was used. Such conduct proved to be safe regarding clinical symptoms, although biochemical markers were slightly elevated after procedure. Propofol seems to be the safest hypnotic drug to use in porphyria; however, special care should be taken is such cases.

The use of inhaled sevoflurane during operative hysteroscopy is associated with increased glycine absorption compared to intravenous propofol for maintenance of anesthesia

STUDY OBJECTIVE

To compare the effects of anesthesia maintenance drugs (inhaled sevoflurane versus intravenous propofol) used in general anesthesia on the absorption of glycine 1.5% solution during hysteroscopy.

DESIGN

Prospective comparative study.

SETTING

Tertiary care university hospital.

PATIENTS

One hundred fifteen women undergoing hysteroscopy.

INTERVENTIONS

Women were assigned to receive general anesthesia with inhaled sevoflurane (n = 77) or intravenous propofol (n = 38) to maintain anesthesia.

MEASUREMENTS

The primary endpoint was clinically relevant glycine 1.5% absorption (>1000 mL), while secondary endpoints were the median of glycine absorption, operative time, complications and the incidence of discontinuation of the hysteroscopic procedure due to excessive glycine 1.5% absorption.

MAIN RESULTS

Maintenance with sevoflurane produced significantly increased absorption of glycine 1.5% solution compared to intravenous anesthesia (264 vs 202 mL, P = .007). Clinically relevant absorption rates (>1000 mL) were observed in the sevoflurane group (P = .04) while none of the women receiving intravenous anesthesia reached this absorption level. No cases of severe post-operative hyponatremia (Na(1+)<125 mmol/L) or adverse events derived from glycine 1.5% absorption were reported. No major complications (such as perforations, severe hemorrhage or infection) were presented during the interventions.

CONCLUSIONS

The results of the present study show that the use of inhaled sevoflurane is associated with significantly increased glycine 1.5% absorption compared to intravenous propofol for the maintenance of anesthesia. However, further randomized controlled trials are needed to assess the possible mechanisms and risk factors involved in the higher absorption induced by sevoflurane.

Effects of adrenaline on circulatory dynamics and cardiac function in rats administered chlorpromazine

We aimed to elucidate changes in circulatory dynamics and cardiac function during concomitant use of chlorpromazine (CPZ) and adrenaline (AD). An arterial line and left intraventricular pressure-volume measurement catheter were inserted in rats. CPZ 10 mg/kg was administered to the left great adductor muscle, followed by normal saline (NS) or AD 50 μg/kg through the tongue 20 min later. End-diastolic volume (V _ed), end-systolic pressure (P _es), stroke volume (SV), stroke work (SW), end-systolic volume elastance (E _es), systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse rate (PR) were measured. Following AD administration, V _ed significantly decreased at 2-4 and 10 min than that in control rats; P _es significantly decreased at 1 min; E _es significantly increased from 2 to 10 min; SV did not change significantly, and SW significantly reduced at 1 and 2 min; SBP and DBP were lower at 1-3 min than in the control; and PR increased at 10 min. These findings suggest that when AD-containing local anesthetics are administered during dental treatment of patients taking CPZ, there is a risk of a temporary drop in blood pressure. However, the blood pressure is recovered a few minutes later by the increase in afterload and the myocardial contractile force.

Anaesthetic management of acute airway obstruction

The acutely obstructed airway is a medical emergency that can potentially result in serious morbidity and mortality. Apart from the latest advancements in anaesthetic techniques, equipment and drugs, publications relevant to our topic, including the United Kingdom's 4th National Audit Project on major airway complications in 2011 and the updated American Society of Anesthesiologists' difficult airway algorithm of 2013, have recently been published. The former contained many reports of adverse events associated with the management of acute airway obstruction. By analysing the data and concepts from these two publications, this review article provides an update on management techniques for the acutely obstructed airway. We discuss the principles and factors relevant to the decision-making process in formulating a logical management plan.

Isoflurane versus sevoflurane with interscalene block for shoulder arthroscopic procedures: Value of process capability indices as an additional tool for data analysis

BACKGROUND AND AIMS

Hypotensive anaesthesia reduces intra-articular bleed and promotes visualisation during arthroscopy. The haemodynamic effects of inhalational agents isoflurane and sevoflurane were studied extensively, and both were found to reduce mean arterial pressures (MBP) to an equivalent magnitude. We investigated the relative ability of isoflurane vis-a-vis sevoflurane to maintain the target systolic blood pressure (SBP) in patients undergoing shoulder arthroscopic procedures.

METHODS

In a prospective randomised study, 59 patients in two groups of 30 and 29 patients each received concomitant general anaesthesia (1.2-1.5 MAC of isoflurane and sevoflurane) and interscalene brachial plexus block. Nitrous oxide was used in both groups. Intraoperatively, serial blood pressure recordings of SBP, diastolic blood pressure (DBP), MBP and heart rates were done at every 3^rd min intervals. The manipulations needed to achieve target SBP (T = 90 mmHg) for optimal arthroscopic visualisation and treat unacceptable hypotensive episodes were noted. Conventional statistical tests and process capability index (PCI) evaluation were both deployed for data analysis.

RESULTS

Lower mean SBP and DBPs were recorded for isoflurane patients as compared to sevoflurane (P < 0.05, for mean, maximum and minimum recordings). Higher mean heart rates were recorded for isoflurane (P < 0.05). PCIs indicated that isoflurane was superior to sevoflurane in the ease of achieving target SBP of 90 mmHg as well as maintaining blood pressures in the range of 80-100 mmHg.

CONCLUSION

Isoflurane provides better intraoperative haemodynamic status vis-a-vis sevoflurane in patients undergoing shoulder arthroscopic surgery with preliminary interscalene blockade. The PCI can be a useful additional medical data analysis tool.

Closing the gap between the molecular and systemic actions of anesthetic agents

Genetic approaches have been successfully used to relate the diverse molecular actions of anesthetic agents to their amnestic, sedative, hypnotic, and immobilizing properties. The hypnotic effect of etomidate, quantified as the duration of the loss of righting reflex in mice, is equally mediated by GABAA receptors containing β2- and β3-protein subunits. However, only β3-containing receptors are involved in producing electroencephalogram (EEG)-patterns typical of general anesthesia. The sedative action of diazepam is produced by α1-subunit-containing receptors, but these receptors do not contribute to the drug's characteristic EEG-"fingerprint." Thus, GABAA receptors with α1- and β2-subunits take a central role in causing benzodiazepine-induced sedation and etomidate-induced hypnosis, but the corresponding EEG-signature is difficult to resolve. Contrastingly, actions of etomidate and benzodiazepines mediated via α2- and β3-subunits modify rhythmic brain activity in vitro and in vivo at least in part by enhancing neuronal synchrony. The immobilizing action of GABAergic anesthetics predominantly involves β3-subunit-containing GABAA receptors in the spinal cord. Interestingly, this action is self-limiting as GABA-release is attenuated via the same receptors. Anesthetic-induced amnesia is in part mediated by GABAA receptors harboring α5-subunits that are highly enriched in the hippocampus and, in addition, by α1-containing receptors in the forebrain. Because there is accumulating evidence that in patients the expression pattern of GABAA receptor subtypes varies with age, is altered by the long-term use of drugs, and is affected by pathological conditions like inflammation and sepsis, further research is recommended to adapt the use of anesthetic agents to the specific requirements of individual patients.

Cost analysis of three techniques of administering sevoflurane

Background. This study aimed to evaluate and compare total cost of sevoflurane and propofol for 1.0 MAC-hour of anaesthesia, employing three anaesthetic techniques. Methods. Adult patients scheduled for surgical procedures under general anaesthesia anticipated to last approximately an hour were randomized into three groups (n = 15 each), to receive anaesthesia using one of the following techniques: low flow technique involving induction with propofol, followed by sevoflurane delivered using initial fresh gas flows of 6 L/min till MAC reached 1.0 and then reduced to 0.5 L/min; alternate method of low flow entailing only a difference in fresh gas flow rates being maintained at 1 L/min throughout; the third technique involving use of sevoflurane for both induction and maintenance of anaesthesia. Results. Cost of sevoflurane to maintain 1 MAC-hour of anaesthesia was clinically least with low flow anaesthesia, though statistically similar amongst the three techniques. Once the cost of propofol used for induction in two of the three groups was added to that of sevoflurane, cost incurred was least with the technique using sevoflurane both for induction and maintenance of anaesthesia, as compared to low flow and alternative low flow techniques, a 26% and 32% cost saving, respectively (P < 0.05).

Clinical comparison of propofol-remifentanil TCI with sevoflurane induction/maintenance anesthesia in laparoscopic cholecystectomy

Objective : We aimed to compare the anesthetic characteristics between total intravenous anesthesia (TIVA) using propofol-remifentanil with target control infusion (TCI) and volatile induction and maintenance anesthesia (VIMA) using sevoflurane and sufentanyl for patients undergoing laparoscopic cholecystectomy.

METHODS

A total of 120 patients undergoing laparoscopic cholecystectomy were randomly assigned to two groups. Patients in group T received TCI of propofol-remifentanil for induction and maintenance. Patients in group S received sevoflurane-sufentanyl for induction and maintenance.

RESULTS

Patients in group S had a significantly faster induction time than patients in group T (109s vs.44s). The emergence time in terms of time to extubation was comparable between the two groups, while the time to eyes opening (419s vs.483s, p=0.006) and duration in PACU were longer in group S (44 min vs.53 min, p=0.017). Ten (17.2%) patients in group S were administered an antihypertensive drug when gallbladder issues were present, while only 1(1.7%) patient needed this drug in group T (p=0.004).More patients in group T than in group S received fentanyl for analgesia in PACU (88%vs.70%, p=0.013). The incidence of postoperative nausea and vomiting (PONV) in PACU was higher in group S than in group T (20% vs.38%, p=0.027).

CONCLUSION

Both techniques had advantages and disadvantages in laparoscopic cholecystectomy; none of the techniques studied was superior.

Propofol modulates phasic and tonic GABAergic currents in spinal ventral horn interneurones

BACKGROUND

Surgical interventions like skin incisions trigger withdrawal reflexes which require motor neurones and local circuit interneurones in the spinal ventral horn. This region plays a key role in mediating immobilizing properties of the GABAergic anaesthetic propofol. However, it is unclear how propofol modulates GABA(A) receptors in the spinal ventral horn and whether tonic or phasic inhibition is involved.

METHODS

Organotypic spinal cord tissue slices were prepared from mice. Whole-cell recordings were performed for quantifying effects of propofol on GABA(A) receptor-mediated phasic transmission and tonic conductance.

RESULTS

Propofol increased GABAergic phasic transmission by a prolongation of the decay time constant in a concentration-dependent manner. The amount of the charge transferred per inhibitory post-synaptic current, described by the area under the curve, was significantly augmented by 1 µM propofol (P<0.01). A GABA(A) receptor-mediated tonic current was not induced by 1 µM propofol but at a concentration of 5 µM (P<0.05).

CONCLUSIONS

Propofol depresses ventral horn interneurones predominantly by phasic rather than by tonic GABA(A) receptor-mediated inhibition. However, the present results suggest that the involvement of a tonic inhibition might contribute to the efficacy of propofol to depress nociceptive reflexes at high concentrations of the anaesthetic.

The impact of genetic factors on response to anaesthetics

In recent years, exceptional progress has been observed in pharmacogenetics, i.e. investigations of inherited conditioning of the organism's response to drugs or xenobiotics. On the other hand, modern molecular biology techniques have been implemented, making it possible to perform studies determining the involvement of genetic factors in differing responses to agents employed in general anaesthesia. Unexpected and incorrect response of the organism to the administration of specific anaesthetics is most commonly associated with a genetic defect of the metabolic pathway of a given agent or its receptor. The majority of agents used in anaesthesia are metabolised in the liver by the cytochrome P450 superfamily enzymes (CYPs) and phase II drug-metabolising enzymes: glutathione S-transferases (GSTs), sulphotransferases (SULTs), UDP-glucuronosyltransferases (UGTs) and NAD(P)H:quinone oxidoreductase (NQO1). Propofol is presently widely used for gastrointestinal (GI) and several other procedures. Among genes associated with metabolism of the most commonly applied anaesthetics such as propofol and sevoflurane, the following ones can be mentioned: CYP2E1, CYP2B6, CYP2C9, GSTP1, UGT1A9, SULT1A1 and NQO1. Moreover, the basic mechanism of propofol action involves its interaction with an ionotropic receptor GABAA inhibiting transfer of nerve impulses. Molecular studies have shown that polymorphic changes in GABRG2 receptor gene turn out to be important in the propofol anaesthesia. Planning of optimal anaesthesia can be considerably assisted by the determination of genetic factors of prognostic value taking advantage of genotyping and making it possible to select anaesthetics and reduce risk of side effects as well as undesirable actions.

Measurement of consumption of sevoflurane for short pediatric anesthetic procedures: Comparison between Dion's method and Dragger algorithm

Background:

The most common drugs used in an operating room are the Inhalation agents for maintenance of anesthesia yet their measurement methods during the procedure are not well-validated. Conventional methods of measuring the vaporizer weight after each use suffers from practical limitations of high error and time constraints.

Aims:

We compared two alternative methods available (Dion's method and Drager Inc. patent protocol) for their degree of concordance and correlation in real-time consumption of sevoflurane for pediatric procedures.

Results:

Both methods showed a very strong correlation (0.895 [P > 0.001]). Dion's method underestimated consumption by 2.59 ml with limits of agreement between 5.188 ml and −0.008 ml. Both test results showed a strong correlation, but poor concordance.

Conclusions:

Dion's method strongly correlates with Drager protocol although concordance between the two methods for measuring anesthetic gas consumption is poor. Dion's method underestimates the consumption and with slight modification addressing this underestimation, it can be electronically incorporated in other workstations to overcome limitations of real-time measurement of inhalation agent consumption.

Target-controlled infusion (Propofol) versus inhaled anaesthetic (Sevoflurane) in patients undergoing shoulder arthroscopic surgery

BACKGROUND

One of the challenges of anaesthesia for shoulder arthroscopic procedures is the need for controlled hypotension to lessen intra-articular haemorrhage and thereby provide adequate visualisation to the surgeon. Achievement of optimal conditions necessitates several interventions and manipulations by the anaesthesiologist and the surgeon, most of which directly or indirectly involve maintaining intra-operative blood pressure (BP) control.

AIM

This study aimed to compare the efficacy and convenience of target controlled infusion (TCI) of propofol and inhalational agent sevoflurane in patients undergoing shoulder arthroscopic surgery after preliminary inter-scalene blockade.

METHODS

Of thirty four patients studied, seventeen received TCI propofol (target plasma concentration of 3 μg/ml) and an equal number, sevoflurane (1.2-1.5 Minimum Alveolar Concentration). N2O was used in both groups. Systolic, diastolic, mean blood pressures and heart rate were recorded regularly throughout the procedure. All interventions to control BP by the anaesthesiologist and pump manipulation requested by the surgeon were recorded. The volume of saline irrigant used and the haemoglobin (Hb) content of the return fluid were measured.

RESULTS

TCI propofol could achieve lower systolic, mean BP levels and the number of interventions required was also lower as compared to the sevoflurane group. The number of patients with measurable Hb was lower in the TCI propofol group and this translated into better visualisation of the joint space. A higher volume of saline irrigant was required in the sevoflurane group. No immediate peri-operative anaesthetic complications were noted in either category.

CONCLUSION

TCI propofol appears to be superior to and more convenient than sevoflurane anaesthesia in inter-scalene blocked patients undergoing shoulder arthroscopy.

Effect of sevoflurane versus propofol-based anesthesia on the hemodynamic response and recovery characteristics in patients undergoing microlaryngeal surgery

Background:

This randomized study was conducted to compare the hemodynamic changes and emergence characteristics of sevoflurane versus propofol anesthesia for microlaryngeal surgery.

Methods:

Forty adult patients undergoing microlaryngoscopy were randomly allocated into two groups. In propofol group, anesthesia was induced with 2-3 mg/kg propofol and maintained with propofol infusion 50-200 μg/kg/h. In sevoflurane group induction was carried out with 5-8% sevoflurane and maintained with sevoflurane in nitrous oxide and oxygen. The propofol and sevoflurane concentrations were adjusted to maintain the bispectral index of 40-60. All patients received fentanyl 2 μg/kg before induction and succinylcholine 2 mg/kg to facilitate tracheal intubation. The hemodynamic changes during induction and suspension laryngoscopy were compared. In addition, the emergence time, time to extubation, and recovery were assessed.

Results:

The changes in heart rate were comparable. The mean arterial pressure was significantly lower after induction and higher at insertion of operating laryngoscope in propofol group as compared to sevoflurane group. More patients in propofol group had episodes of hypotension and hypertension than sevoflurane group. The emergence time, extubation times, and recovery time were similar in both groups.

Conclusion:

We found that sevoflurane showed advantage over propofol in respect of intraoperative cardiovascular stability without increasing recovery time.

Sevoflurane versus propofol anesthesia in patients undergoing lumbar spondylodesis: a randomized trial

BACKGROUND

Spondylodesis is a procedure aiming at providing stability in one or more spinal segments. The aim of our study was to compare sevoflurane and propofol as induction and maintenance agents, focusing on hemodynamic stability, recovery characteristics, postoperative nausea and vomiting, and pain intensity.

MATERIALS AND METHODS

Seventy patients, with a physical status according to American Society of Anesthesiologists (ASA) I-II, 50-72 y old, undergoing selective lumbar spondylodesis were enrolled.

RESULTS

There was no statistically significant difference between groups in overall mean hemodynamic parameters. No differences in fluid administration and vasoactive substances used were noted. Postoperatively, there was a significant difference in overall mean visual analog score at rest and at cough, with the sevoflurane group showing lower values. No differences in the incidence of nausea, vomiting, shivering, postoperative sedation scores, and orientation to place were revealed. Orientation to time exhibited a statistically significant difference at the time just after transfer to the post-anesthesia care unit, where more patients of the sevoflurane group seemed to be well oriented.

CONCLUSIONS

Sevoflurane and propofol anesthesia for lumbar spondylodesis surgery provide safe and comparable results.

Propofol reduces early post-operative pain after gynecological laparoscopy

BACKGROUND

There is some evidence that propofol may reduce post-operative pain. However, the results on the analgesic effects of propofol are inconsistent. Thus, we hypothesized that propofol reduces acute pain if confounding factors like opioids are avoided.

METHODS

In this prospective, randomized, subject- and assessor-blind, parallel-group, head-to-head comparative study, 90 American Society of Anesthesiologists I or II females underwent elective laparoscopies were randomized to receive either propofol-based (PR), or sevoflurane-based (SR), or sevoflurane-propofol-based anesthesia (SPR). Pain score at rest assessed by a numerical rating scale at 0.5 h after surgery was the primary outcome. The secondary outcomes included pain score at 1 and 24 h post-operatively, duration of post-anesthesia care units stay (PACU), incidence of post-operative nausea and vomiting, incidence of shivering, and post-operative quality of recovery score (QoR-40) within the first 24 h post-operatively.

RESULTS

No patients received rescue analgesia. The pain score at 0.5 h post-operatively was less in group PR when compared with group SR (0.7 ± 1.4 vs. 2.1 ± 1.8; P = 0.010) or group SPR (0.7 ± 1.4 vs. 2.1 ± 2.2; P = 0.008). Group PR was also associated with shorter PACU stay than group SR (21.8 ± 5.7 vs. 26.2 ± 6.9; P = 0.050) or group SPR (21.8 ± 5.7 vs. 27.8 ± 8.9; P = 0.005). Intraoperative bispectral index values, hemodynamic values and post-operative QoR-40 scores did not differ among the three groups.

CONCLUSIONS

Propofol anesthesia was associated with significantly less pain at 0.5 and 1 h after surgery in patients undergoing gynecological laparoscopies with planned opioid-free post-operative analgesia.

A Multi-Centre Multi-National Survey of Anaesthetists Regarding the Range of Anaesthetic and Surgical Practices for Paediatric Scoliosis Surgery

Institutional responses to a detailed multi-national survey were used to characterise the range of current anaesthetic and surgical practices for paediatric scoliosis surgery. Questions addressed surgical practice, anaesthetic agents, blood-sparing techniques, neurophysiological monitoring used and recalled major complications. Twenty-seven (87%) institutions responded. The median number of cases of these institutions was 40 per year (range 5 to 700). Common practices included inhaled volatile anaesthetic maintenance (80%), omission of nitrous oxide (81%), intravenous remifentanil (88% [range 0.05 to 2.00 μg.kg-1.min-1]), and double intravenous antiemetic agent prophylaxis (59%); multimodal analgesia with paracetamol and parenteral opioids, non-steroidal anti-inflammartory drugs and epidural local anaesthetic or opioid infusion (UK) and intrathecal opioids and sub-anaesthetic doses of intravenous ketamine by infusion (Australia); use of cell-saver (81%), controlled hypotension (77%) and antifibrinolytic agents (74%) (intravenous aprotinin [59%] or tranexamic acid [44%]); and epidural somatosensory (92%), neurogenic motor-evoked (32%), compound motor action (31%) and transcranial motor-evoked potential monitoring (54%), with routine wake-up test used infrequently (19%). Fifty-four neurological or cardiac adverse events or deaths were recalled. While institutional practices varied, common themes were identified. The information obtained may suggest new strategies to various centres and could be useful for planning multi-centre audits and trials.

[Comparison of rapid anesthetic induction with sevoflurane vs target-controlled infusion of propofol]

OBJECTIVE

To determine whether inhalation induction is faster than target-controlled infusion (TCI).

MATERIAL AND METHODS

Patients in ASA physical status 1 or 2 who were scheduled for elective surgery were randomized to a propofol TCI group or a sevoflurane group. Both groups received a TCI of 5 ng L(-1) of remifentanil. Rapid induction was performed using an effect-site TCI of 2.8 microg mL(-1) of propofol in the propofol group and 8% sevoflurane in the sevoflurane group. We recorded time until loss of the palpebral reflex, hemodynamic variables, respiratory variables, hypnotic depth of anesthesia using the auditory evoked potentials index (AAI), and the moment the anesthesiologist decided to intubate. Also recorded was the time taken to reach an AAI of less than 40, which was established as the threshold of hypnotic depth sufficient for tracheal intubation.

RESULTS

Forty-four patients were enrolled in the trial. The palpebral reflex loss time was 60 (44-90) seconds in the TCI-propofol group and 72 (38-265) seconds in the sevoflurane group (P<.05). An AAI of less than 40 was reached in 105 (90-195) seconds in the TCI-propofol group and in 230 (125-355) seconds in the sevoflurane group. The variation in the calculated effect-site concentration (Ce) was consistent with the direction of change in the AAI value, which decreased as Ce increased; the variation in the expired fraction of sevoflurane did not show the same relationship. The anesthesiologist was not authorized to intubate 2 patients in the sevoflurane group as the AAI threshold was not reached. The decrease in blood pressure was significantly greater in patients in the sevoflurane group than in those in the propofol group.

CONCLUSION

Anesthetic induction is faster with a TCI of propofol based on Ce than with sevoflurane. The propofol Ce was consistent with the direction of change in the AAI.

An investigation of potential genetic determinants of propofol requirements and recovery from anaesthesia

BACKGROUND AND OBJECTIVE

The objectives of this study were, firstly, to characterize the inter-patient variability in the dose of propofol required to achieve a bispectral index <70 and 'time to eye opening' following propofol infusion and, secondly, to determine if the pharmacodynamic parameter 'time to achieve bispectral index <70' was influenced by genotype of the sex-linked drug receptor gene GABRE or if pharmacokinetic parameters such as clearance and 'time to eye opening' were influenced by the genotype of the metabolizing enzyme CYP2B6.

METHODS

One hundred and fifty patients received a standardized anaesthetic. Apparent systemic clearance values were estimated. Correlation was sought between carriers of different CYP2B6 and GABRE genotypes and apparent systemic clearance, 'time to achieve bispectral index <70' and 'time to eye opening'.

RESULTS

Propofol induction/emergence characteristics varied, with slow recovery times in a subset of males. Time to loss of verbal contact and time to bispectral index <70 varied 6.6- and 4.3-fold, respectively. At emergence, there was a 15.5- to 111-fold variability in the measured time intervals. Clearance varied from 9.1 to 55.8 mL min-1 kg-1. The CYP2B6 C1459T (R487C) genotype frequencies were TT 1%, TC 22% and CC 67%. The three major haplotypes of CYP2B6 (R487C, K262R and Q172H variants) were not significantly associated with time to eye opening or clearance. Clearance was similar in 487C carriers and 487RR genotypes. There was no statistically significant correlation between the four major haplotypes of GABRE variants investigated ([mRNA358]G/T, 20118C/T, 20326C/T and 20502 A/T) and the observed anaesthesia induction time.

CONCLUSIONS

Great inter-patient variability exists in the dose of propofol required to achieve bispectral index <70, apparent systemic propofol clearance and time to eye opening. Common haplotypic differences at the CYP2B6 and GABRE genes do not appear to account for the majority of the observed inter-patient variability.

Modulation of presynaptic beta3-containing GABAA receptors limits the immobilizing actions of GABAergic anesthetics

Intravenous GABAergic anesthetics are potent hypnotics but are rather ineffective in depressing movements. Immobility is mediated, in part, by the ventral horn of the spinal cord. We hypothesized that the efficacy of these anesthetics in producing immobility is compromised by the activation of GABA(A) receptors located presynaptically, which modulate GABA release onto neurons in the ventral horn. Because anesthetics acting by modulation of GABA(A) receptor function require GABA to be present at its binding site, a decrease in GABA release would abate their efficacy in reducing neuronal excitability. Here we report that in organotypic spinal cord slices, the efficacy of the intravenous anesthetic etomidate to depress network activity of ventral horn neurons is limited to approximately 60% at concentrations greater than 1 microM that produce immobility. Depression of spinal network activity was almost abolished in spinal slices from beta3(N265M) knock-in mice. In the wild type, etomidate prolonged decay times of GABA(A) receptor-mediated inhibitory postsynaptic currents (IPSCs) and concomitantly reduced the frequency of action potential-dependent IPSCs. Etomidate prolonged the decay time of GABA(A) receptors at all tested concentrations. At concentrations greater than 1.0 microM, anesthetic-induced decrease of GABA release via modulation of presynaptic GABA(A) receptors and enhancement of postsynaptic GABA(A) receptor-function compensated for each other. The results suggest that the limited immobilizing efficacy of these agents is probably due to a presynaptic mechanism and that GABAergic agents with a specificity for post-versus presynaptic receptors would probably have much stronger immobilizing actions, pointing out novel avenues for drug development.

Different effects on circulatory control during volatile induction and maintenance of anesthesia and total intravenous anesthesia: autonomic nervous activity and arterial cardiac baroreflex function evaluated by blood pressure and heart rate variability analysis

STUDY OBJECTIVE

To evaluate the different effects on autonomic circulatory control during volatile induction/maintenance of anesthesia (VIMA) vs total intravenous anesthesia (TIVA).

DESIGN

Prospective study.

SETTING

Operating theater of a university hospital.

PATIENTS

Twenty patients, with American Society of Anesthesiologists physical status of I or II, were randomly allocated into the VIMA group (n = 10) or the TIVA group (n = 10).

INTERVENTIONS

In the VIMA group, anesthesia was induced with 5% sevoflurane and 60% N2O in oxygen and maintained with 2% sevoflurane and 60% N2O in oxygen. In the TIVA group, anesthesia was induced with propofol 2.0 mg/kg intravenously by bolus injection and fentanyl 2 microg/kg, and maintained with an intravenous infusion of propofol 5 mg/kg.per hour and air-oxygen mixture.

MEASUREMENTS

Monitoring included recordings of electrocardiographic and arterial blood pressure waveforms. Autonomic nervous activity and arterial cardiac baroreflex function were evaluated by analysis of blood pressure variability, heart rate variability, and transfer function analysis between these 2 variables.

MAIN RESULTS

In the VIMA group, the low-frequency component of blood pressure variability (LF(SBP)) and low- and high-frequency components of the R-R interval variability (LF(RR) and HF(RR)) decreased significantly during anesthesia. In the TIVA group, LF(SBP) and LF(RR) decreased significantly. The degree of reduction in LF(SBP) was greater in the VIMA group than in the TIVA group. However, changes in R-R interval variability and cardiac baroreflex indices were not significantly different between the 2 groups.

CONCLUSIONS

Our results demonstrated that although reductions in autonomic nervous modulation to the heart might not be so different between the 2 groups, reduction in sympathetic nervous modulation to peripheral vasculature is greater in the VIMA group than in the TIVA group.

Clonidine premedication effects on inhaled induction with sevoflurane in adults: a prospective, double-blind, randomized study

BACKGROUND

The purpose of this study was to evaluate whether oral clonidine premedication becomes an alternative to N2O in terms of shortening the induction time and attenuation of the adrenergic response to tracheal intubation during inhalation induction with sevoflurane, and to evaluate the quality of anesthetic induction according to the patient's satisfaction.

METHODS

We studied 84 female patients who were randomly allocated into four study groups: Groups I and II received a placebo orally, and Groups III and IV received clonidine at 150 and 300 microg, respectively, 90 min before induction of anaesthesia. Patients were anesthetized using a triple-deep-breath technique with 5% sevoflurane in Groups I, III and IV, and with 60% N2O-5% sevoflurane in group II.

RESULTS

Induction time was significantly longer (P < 0.05) in Group I. Increases in mean blood pressure and heart rate after tracheal intubation were significantly suppressed in Groups III and IV but not in Group II compared with Group I. Comfort and impression of anesthesia was better in Groups III and IV than in Groups I and II.

CONCLUSION

In volatile anesthetic induction, pre-anesthetic clonidine may become an alternative to N2O and may provide more comfort than with N2O.

Sevoflurane for interventional neuroradiology procedures is associated with more rapid early recovery than propofol

PURPOSE

Sevoflurane and propofol are both suitable for neuroanesthesia but have not previously been compared as maintenance agents for long duration (one to five hours) procedures.

METHODS

Using a multicentre international study protocol, 103 patients were randomized to receive either sevoflurane or propofol for maintenance of anesthesia during interventional neuroradiology procedures. After a standardized induction of anesthesia with propofol, 53 patients received sevoflurane 1 to 3% with 60% nitrous oxide (N(2)O) in oxygen (O(2)), and 50 patients received propofol 4 to 10 mg x kg(-1) x hr(-1) with 60% N(2)O in O(2). Maintenance agents were titrated against systemic arterial blood pressure (baseline mean arterial pressure +/- 20%). Recovery times, changes in sedation, pain, nausea and vomiting and psychomotor function during recovery and use of rescue medication were recorded.

RESULTS

The group receiving sevoflurane had a more rapid recovery to spontaneous ventilation, extubation, eye opening and orientation compared to the group receiving propofol (3 vs 4 min, P = 0.01; 5 vs 6 min, P = 0.015; 7 vs 10 min, P < 0.001; 13 vs 17 min, P = 0.028; respectively). Sedation, pain, nausea and vomiting, and psychomotor function scores were similar in the two groups. Use of opioid boluses and vasopressors were similar.

CONCLUSION

The use of sevoflurane for maintenance of anesthesia for prolonged neuroradiological procedures is associated with more rapid early recovery than propofol and is associated with similar side effects. Sevoflurane and propofol can both be recommended for these procedures. The clinical benefit of the more rapid recovery with sevoflurane is unknown.

A comparison of 8% and 12% sevoflurane for inhalation induction in adults

Sevoflurane is a non-pungent volatile anaesthetic agent with a low blood-gas solubility coefficient. It has been studied in concentrations of up to 8% for induction of anaesthesia. Previous work has suggested that there may be a ceiling effect with increasing concentration of sevoflurane above 6%, but there are no published studies using 12% sevoflurane. This study compared 8 and 12% sevoflurane to induce anaesthesia in adults. Sevoflurane was administered using two adapted datum vaporisers with the interlock removed. Induction with 12% sevoflurane compared to 8% sevoflurane produced a significant decrease in the time to achieve central pupils, corresponding to surgical anaesthesia and the third part of Guedel's stage 3 of anaesthesia (mean time (SD) 201 s (81) and 247 s (39), respectively, p < 0.05). Twelve-percent sevoflurane produced a similar stable cardiovascular profile to 8% sevoflurane, and there was no increase in respiratory complications.

Total intravenous anaesthesia: is it worth the cost?

Total intravenous anaesthesia (TIVA) has many advocates and offers potential benefits, yet the direct costs of this technique are commonly greater than those of inhalation-based alternatives. Although many advantages are claimed for TIVA, in reality all modern anaesthetics are effective and have good safety and tolerability profiles, rendering these differences of less importance now than was perhaps once the case. The majority of direct comparisons between inhaled and intravenous anaesthetics have failed to demonstrate significant differences in recovery times, yet they have consistently shown greater direct costs associated with intravenous propofol anaesthesia. It is commonly believed that indirect costs may be offset by indirect savings achieved through more rapid recovery, reduction in adverse effects and decreased staff workloads. In some cases, these differences in outcome have not been observed, while in many where they have, indirect savings are only theoretical. Reductions in recovery time and nursing workload will only result in savings if fewer nurses are required or if the existing ones can be paid for fewer hours. Salary arrangements, peak demand for patient care, performance of multiple tasks in parallel and limitations in time accounting methodology all limit the ability to achieve such savings in reality. Drug wastage also contributes to the cost of anaesthesia and is common to both intravenous and inhaled techniques. With inhaled anaesthesia, wastage can be reduced by the use of lower fresh gas flows, which has no adverse consequences and may provide potential benefits. With intravenous anaesthesia, reducing drug wastage is difficult and potentially harmful through cross-contamination of drugs between patients. Recently, the cost of propofol has been reduced with the availability of generics, making TIVA a more attractive proposition. The costs of several inhaled anaesthetics have also decreased, however, reducing any relative benefit. Nevertheless, the net result of lowered costs is that all types of anaesthetic drugs, which typically comprise <5% of a hospital pharmacy budget, represent excellent value for money. With few new products in the immediate pipeline and most established drugs already generic or about to lose their patent protection, the expense of anaesthesia is likely to decline even further. Perhaps then we will be able to stop arguing over relatively small differences in cost and choose a technique that, in our own experienced hands, provides the best and safest patient outcomes.

Patient well-being after general anaesthesia: a prospective, randomized, controlled multi-centre trial comparing intravenous and inhalation anaesthesia

BACKGROUND

The aim of this study was to assess postoperative patient well-being after total i.v. anaesthesia compared with inhalation anaesthesia by means of validated psychometric tests.

METHODS

With ethics committee approval, 305 patients undergoing minor elective gynaecologic or orthopaedic interventions were assigned randomly to total i.v. anaesthesia using propofol or inhalation anaesthesia using sevoflurane. The primary outcome measurement was the actual mental state 90 min and 24 h after anaesthesia assessed by a blinded observer using the Adjective Mood Scale (AMS) and the State-Trait-Anxiety Inventory (STAI). Incidence of postoperative nausea and vomiting (PONV) and postoperative pain level were determined by Visual Analogue Scale (VAS) 90 min and 24 h after anaesthesia (secondary outcome measurements). Patient satisfaction was evaluated using a VAS 24 h after anaesthesia.

RESULTS

The AMS and STAI scores were significantly better 90 min after total i.v. anaesthesia compared with inhalation anaesthesia (P=0.02, P=0.05, respectively), but equal 24 h after both anaesthetic techniques (P=0.90, P=0.78, respectively); patient satisfaction was comparable (P=0.26). Postoperative pain was comparable in both groups 90 min and 24 h after anaesthesia (P=0.11, P=0.12, respectively). The incidence of postoperative nausea was reduced after total i.v. compared with inhalation anaesthesia at 90 min (7 vs 35%, P<0.001), and 24 h (33 vs 52%, P=0.001).

CONCLUSION

Total i.v. anaesthesia improves early postoperative patient well-being and reduces the incidence of PONV.

Randomized comparison between sevoflurane anaesthesia and unilateral spinal anaesthesia in elderly patients undergoing orthopaedic surgery

BACKGROUND AND OBJECTIVE

This prospective, randomized study was conducted to compare unilateral spinal block using small doses of hyperbaric bupivacaine and single-agent anaesthesia with sevoflurane in elderly patients undergoing hip surgery.

METHODS

Thirty patients (> 65 yr) undergoing hip fracture repair were randomly allocated to receive unilateral spinal anaesthesia with hyperbaric bupivacaine 7.5 mg 0.5% (Group Spinal, n = 15) or volatile induction and maintenance anaesthesia with sevoflurane (Group SEVO, n = 15). General anaesthesia was induced by increasing the inspired concentration to 5%. A laryngeal mask airway was placed without muscle relaxants, and the end-tidal concentrations of sevoflurane were adjusted to maintain cardiovascular stability. Hypotension (decrease in systolic arterial pressure > 20% from baseline), hypertension or bradycardia (heart rate < 50 beats min(-1)) requiring treatment, and the length of stay in the postanaesthesia care unit was recorded. Cognitive functions were evaluated the previous day, and 1 and 7 days after surgery with the Mini Mental State Examination test.

RESULTS

Hypotension occurred in seven patients of Group Spinal (46%) and in 12 patients of Group SEVO (80%) (P = 0.05). Phenylephrine was required to control hypotension in three spinal patients (21%) and four SEVO patients (26%) (n.s.). SEVO patients had lower heart rates than spinal patients from 15 to 60 min after anaesthesia induction (P = 0.01). Bradycardia was observed in three SEVO patients (22%). Discharge from the postanaesthesia care unit required 15 (range 5-30) min in Group Spinal and 55 (15-80) min in Group SEVO (P = 0.0005). Eight patients in Group Spinal (53%) and nine patients in Group SEVO (60%) showed cognitive decline (Mini Mental State Examination test decreased > or = 2 points from baseline) 24 h after surgery (n.s.). Seven days after surgery, confusion was still present in one patient of Group Spinal (6%) and in three patients of Group SEVO (20%) (n.s.).

CONCLUSIONS

In elderly patients undergoing hemiarthroplasty of the hip, induction and maintenance with sevoflurane provide a rapid emergence from anaesthesia without more depression of postoperative cognitive function compared with unilateral spinal anaesthesia. This technique represents an attractive option when patient refusal, lack of adequate co-operation or concomitant anticoagulant therapy contraindicate the use of spinal anaesthesia.

Inhalational techniques in ambulatory anesthesia

In the current health care environment, anesthesia practitioners are frequently required to reevaluate their practice to be more efficient and cost-effective. Although IV induction with propofol and inhalational induction with sevoflurane are both suitable techniques for outpatients, patients prefer IV induction. Maintenance of anesthesia with the newer inhaled anesthetics (ie, desflurane and sevoflurane) provide for a rapid early recovery as compared with infusion of propofol (ie, TIVA), while allowing easy titratability of anesthetic depth. Titration of hypnotic sedatives using BIS monitoring may reduce the time to awakening and thereby may facilitate fast tracking (ie, bypassing the PACU) and reduce hospital stay. Inhalational anesthesia is associated with a higher incidence of PONV, but no differences have been demonstrated with respect to late recovery (eg, PACU stay and home readiness). Although clinical differences between desflurane and sevoflurane appear to be small, desflurane may be associated with faster emergence, particularly in elderly and morbidly obese patients. Balanced anesthesia with IV propofol induction and inhalation anesthesia with N2O for maintenance, and an LMA for airway management, may be an optimal technique for ambulatory surgery. Inhalational anesthesia may have an economic advantage over a TIVA technique.

Stress hormones during the wake-up test in scoliosis surgery

STUDY OBJECTIVE

To compare hemodynamic and endocrine stress responses of two anesthetic regimes during intraoperative wake-up tests in scoliosis surgery.

DESIGN

Randomized, controlled clinical study.

SETTING

University hospital.

PATIENTS

40 ASA physical status I and II teenage patients scheduled for scoliosis surgery.

INTERVENTION

Patients were randomly divided into two groups: the propofol group (Group P) and the sevoflurane group (Group S). In Group P, anesthesia was induced with propofol and remifentanil and was maintained with infusions. Sevoflurane and remifentanil were used in Group S. After surgical instrumentation, patients were awakened, and the wake-up times were recorded. To determine the stress responses, blood samples were taken before induction, 10 minutes after surgical incision, before the wake-up test, during the wake-up test, and 10 minutes after the wake-up test. Cortisol, epinephrine, and norepinephrine concentrations, and hemodynamics all were recorded at the same time.

MEASUREMENTS AND MAIN RESULTS

The times from discontinuation of anesthetics to eye opening and movement were similar in both groups. Epinephrine and norepinephrine concentrations during the wake-up test were significantly higher than pretest results in both groups (p < 0.001). There were no statistically significant differences between groups in heart rate or blood pressure.

CONCLUSIONS

Propofol-remifentanil anesthesia is equivalent to sevoflurane-remifentanil anesthesia for a wake-up test. Both the propofol- and sevoflurane-based anesthetic regimens abolish hemodynamic and endocrine stress responses to incision for scoliosis surgery in teenagers. Intraoperative wake-up testing is associated with substantial catecholamine stress despite virtually unchanged mean arterial pressure and heart rate.

Inhalational anaesthesia

Sevoflurane and desflurane have important advantages over isoflurane and halothane. Disadvantages, which the clinician should keep in mind, include the degradation of both agents by soda lime under certain circumstances during closed circuit anaesthesia. As a result compound A and carbon monoxide (CO) may be generated in soda lime canisters and may be inhaled by patients. The extent to which this constitutes a significant problem during routine anaesthesia in humans is not clear. Recent developments in absorbent technology have the potential to reduce any hazard to negligible proportions. Other undesirable properties of the newer inhalation agents include agitation with sevoflurane in children and cardiovascular and airway effects with desflurane.