Background and objective: Cardiovascular and mental stress in dental patients with phobias about dentistry may be reduced by propofol sedation. We tested the hypothesis that even low doses of propofol may have effects on body temperatures in male volunteers.

Methods: Six healthy male volunteers were given propofol over 28 min with the following infusion rates: 8 mg kg−1 h−1 for the first 3 min, 4 mg kg−1 h−1 for the next 10 min, and 2 mg kg−1 h−1 for the final 15 min. Body temperatures were measured at five locations: tympanic membrane, forehead, forearm, dorsum of the hand and fingertip. Thermoregulatory vasoconstriction was evaluated using the forearm minus fingertip temperature gradient.

Results: Tympanic membrane and forehead temperatures began to decrease at 10 and 20 min, respectively, after the start of the propofol infusion, and reached a minimum at 30 min (tympanic −0.5 ± 0.2°C) and 40 min (forehead −0.6 ± 0.2°C), respectively. Peripheral skin temperatures showed an increase between 10 and 30 min in the forearm and fingertip and between 20 and 30 min in the dorsum of the hand. After 30 min, a decrease in peripheral skin temperatures was observed. The forearm minus fingertip temperature gradient changed from negative to positive after 40 min, and increased continuously thereafter (baseline −0.3 ± 0.4°C, 90 min: 6.5 ± 1.6°C).

Conclusions: A low dose of propofol impairs tonic thermoregulatory vasoconstriction and induces heat redistribution from the core to the periphery.

The effectiveness of a Eutectic Mixture of Local Anaesthetics (EMLA cream) for pain control during renal extracorporeal shock wave lithotripsy (ESWL) was evaluated in a group of 20 patients who had not been able to tolerate a previous session without intravenous (i.v.) analgesia. EMLA cream (10 g) was applied on the skin over the area (64–100 cm2) where the shock waves were to be focussed. A second generation lithotriptor Siemens Lithostar was used. The following measurements were made: the shock wave (kV) maximum voltage, the number of successful stone fragmentations (SSF), the visual analogue scale score (0–10) for pain (VAS), and the tolerance scale score (1–4) for the tolerance for the procedure. Significantly higher voltage (17.9±0.6 kV vs. 16.2±0.8 kV), lower VAS scores (5.9±1.1 vs. 8.7±1.3), lower TS score (2.3±0.6 vs. 3.6±0.6) and a higher number of SSF (18 vs. 5) were found in those patients for whom EMLA cream was used. Intravenous analgesia was not needed in nine patients. Nine patients received fentanyl 0.05 mg, one 0.10 mg and another 0.15 mg. These favourable results were attributed both to the sequence of gradual voltage increments used and to the cutaneous analgesia produced by EMLA cream.

Summary

Background and objective: To determine the minimal oxygen delivery and pump flow that can maintain systemic oxygen uptake during normothermic (37°C) pulsatile and non-pulsatile cardiopulmonary bypass in dogs. Methods: Eighteen anaesthetized dogs were randomly assigned to receive either non-pulsatile (Group C; n = 9) or pulsatile bypass flow (Group P; n = 9). Oxygen delivery was reduced by a progressive decrease in pump flow, while arterial oxygen content was maintained constant. In each animal, critical oxygen delivery was determined from plots of oxygen uptake vs. oxygen delivery and from plots of blood lactate vs. oxygen delivery using a least sum of squares technique. Critical pump flow was determined from plots of lactate vs. pump flow. Results: At the critical point, oxygen delivery obtained from oxygen uptake was 7.7 ± 1.1 mL min−1 kg−1 in Group C and 6.8 ± 1.8 mL min−1 kg−1 in Group P (n.s.). These values were similar to those obtained from lactate measurements (Group C: 7.8 ± 1.6 mL min−1 kg−1; Group P: 7.6 ± 2.0 mL min−1 kg−1). Critical pump flows determined from lactate measurements were 55.6 ± 13.8 mL min−1 kg−1 in Group C and 60.8 ± 13.9 mL min−1 kg−1 in Group P (n.s.). Conclusions: Oxygen delivery values greater than 7–8 mL min−1 kg−1 were required to maintain oxygen uptake during normothermic cardiopulmonary bypass with either pulsatile or non-pulsatile blood flow. Elevation of blood lactate levels during bypass helps to identify inadequate tissue oxygen delivery related to insufficient pump flow.

Backgound and objective A postal survey was conducted in order to investigate current practice in airway management amongst Dutch anaesthetists and to investigate the role of recent training and the role of an ‘Access to the Airway’ airway management course.

Methods A questionnaire containing 27 questions was sent to all practising anaesthetists in The Netherlands. Questionnaires were returned anonymously and were analysed using the Pearson χ2-test (P < 0.05) with the SPSS® version 8.0 statistical software program.

Results The response rate was 42%. Of the respondents, 78% claim often or always to assess the expected degree of difficulty in tracheal intubation as part of routine preoperative assessment. The American Society of Anesthesiologist’s Difficult Airway Algorithm was used by 19% of respondents. A wide variety of airway management techniques is being used. In 36% of all general anaesthetics a laryngeal mask airway is used. In 1.1% of all general anaesthetics tracheal intubation is performed with the flexible fibrescope.

Conclusions Dutch anaesthetists, who commenced anaesthetic training after 1988, and those who attended the airway management course ‘Access to the Airway’ are significantly more likely to follow the American Society of Anesthesiologist’s Difficult Airway Algorithm and to use adjunctive techniques for airway management.

Background and objective: To compare the conditions for insertion of the laryngeal mask airway using sevoflurane or propofol plus fentanyl. We evaluated the haemodynamic changes and cost of induction of anaesthesia in both groups.

Methods: Sixty patients were equally and randomly divided into two groups. Both groups received fentanyl 1 μg kg−1. Patients in the sevoflurane group were induced with 8% sevoflurane and those in the propofol group with propofol 2.5 mg kg−1. Conditions for insertion were graded on a three-point scale using six variables. Overall, conditions were assessed as excellent, satisfactory or poor based on the total score in each group. Systolic and diastolic arterial pressure and heart rate were recorded for 6 min after mask insertion. The financial cost of induction in both groups was calculated.

Results: The mean (±SD) time taken from induction to successful laryngeal mask insertion was significantly shorter with propofol (68.70 ± 22.60 s) compared with sevoflurane (149.83 ± 55.25 s). Excellent or satisfactory conditions were observed in 30 (100%) patients in the propofol group and in 29 (96.66%) in the sevoflurane group. Systolic and diastolic arterial pressures were significantly lower in the propofol group. The cost of sevoflurane used was €3.95 ± 1.48 (Rs 216.23 ± 64.66) (P < 0.05) compared with that of propofol, which was €3.23 ± 0.65 (Rs 141.00 ± 28.20).

Conclusions: Although there was a faster induction with propofol-fentanyl, conditions for insertion of the laryngeal mask airway were similar in both groups. Haemodynamic stability was better with sevoflurane-fentanyl. The propofol-fentanyl combination was more cost-effective.

Summary

Background and objective: The aim was to train artificial neural nets to predict the recovery of a neuromuscular block during general anaesthesia. It was assumed that the initial/early neuromuscular recovery data with the simultaneously measured physical variables as inputs into a well-trained back-propagation neural net would enable the net to predict a rough estimate of the remaining recovery time.

Methods: Spontaneous recovery from neuromuscular block (electrically evoked electromyographic train-of-four responses) were recorded with the following variables known to affect the block: multiple minimum alveolar concentration, end-tidal CO2 concentration, and peripheral and central temperature.

Results: The mean prediction errors, mean absolute prediction errors, root-mean-squared prediction errors and correlation coefficients of all the nets were significantly better than those of average-based predictions used in the study. The root-mean-squared prediction error of the net – employing minimum alveolar concentrations from the whole recovery period (the recovery time from E2/E1 = 0.30 to E4/E1 = 0.75; E1 = first response of train-of-four, E2 = second response of train-of-four, etc.) – were significantly smaller than those of other nets, or the same net employing minimum alveolar concentrations only from the initial recovery period (from E2/E1 = 0.30 to E4/E1 = 0.25).

Conclusions: Neural nets could predict individual recovery times from the neuromuscular block significantly better than the average-based method used here, which was supposed to be more accurate than guesses by any clinician. The minimum alveolar concentration was the only monitored variable that influenced the recovery rate, but it did not aid neural net prediction.

The precise mechanisms underlying secondary brain damage after traumatic injury to the central nervous system (CNS) are not well understood, and delayed neuronal injury may result from pathological changes in neurotransmitter release, synthesis or generation of endogenous autodestructive neurochemicals and/or inflammatory mediators, or alterations in endogenous protective or trophic factors. Recent identification of such factors and the elucidation of the timing of the neurochemical cascade following CNS injury provides a window of opportunity for therapeutic intervention with pharmacological compounds which modify synthesis, release, receptor binding or physiological activity of neurotoxic factors. A number of recent experimental studies have reported that pharmacological modification of the post-traumatic neurochemical milieu can promote functional recovery in a variety of animal models of CNS trauma. This paper summarizes recent work suggesting that pharmacological manipulation of several key neurotransmitter and neurochemical systems can attenuate neuronal damage and improve functional outcome associated with traumatic brain injury.

Background and objective: Some halogenated agents, especially methoxyflurane, because of a higher level of fluoride production, induce a renal concentrating defect that could be related to an ascending limb impairment. We investigated the mechanisms of fluoride toxicity on an immortalized cell line.

Methods: Cells were cultured for 2, 6 or 24 h in the presence of fluoride. Toxicity evaluation was based on: cell numbers, protein content, leucine-incorporation, lactate dehydrogenase (LDH) and N-acetyl-βglucosaminidase (NAG) releases, Na-K-ATPase and Na-K-2Cl activities, electron microscope studies. Infrared analysis and fluoride microdetermination allowed crystal components.

Results: At 5 mmol after 24 h, fluoride decreased cell numbers (−14%, *P < 0.05), protein content (−16%*), leucine incorporation (−54%*), Na-K-2Cl activity (−84%*), increased LDH (+145%*) and NAG release (+190%*). Na-K-ATPase was more sensitive and impaired from 1 mmol for 24 h and after 2 h at 5 mmol. Crystal formation in mitochondria occurred after 6 h at 5 mmol. Infra-red analysis and fluoride microdetermination established that crystals contained sodium, phosphate and fluoride.

Conclusions: The results suggest that the Na-K-ATPase pump is a major target for fluoride toxicity in Henle's loop.

Summary

Background and objective: The aromatic alcohol most closely resembling the aromatic tail of lidocaine is 2,6-dimethylphenol. This agent is as potent as lidocaine in blocking voltage-operated sodium channels. The aim of this study was to show the effect of halogenation in the para-position on the potency of this compound to block voltage-operated sodium channels. Methods: Insertion of the halogen chloride into the para-position of the molecule 2,6-dimethylphenol yielded 2,6-dimethyl-4-chlorophenol. Block of sodium currents by this compound was studied using heterologously expressed voltage-operated rat neuronal (rat IIa) sodium channels. Results: 2,6-dimethyl-4-chlorophenol reversibly suppressed depolarization-induced whole-cell sodium inward currents. The ECR50 for block of resting channels at a hyperpolarized holding potential (−150 mV) was 127 μmol, the Hill coefficient nH 1.7. Membrane depolarization inducing either fast or slow-inactivation strongly increased the blocking potency. This is an important feature of a local-anaesthetic-like action. The estimated half-maximum effect concentration for the fast-inactivated channel state ECI50 was 28 μmol, the Hill coefficient nH 3.8. When 20–30% of channels were slow-inactivated using long (2.5 s) prepulses, followed by a 10 ms repolarization period to allow recovery from fast inactivation, the IC50 at −100 mV holding potential was reduced to 53 μmol. Conclusion: These results, which show that 2,6-dimethyl-4-chlorophenol blocks voltage-operated sodium channels in a lidocaine-like manner while having a several fold higher potency than the non-halogenated parent compound, highlight a potentially meaningful principle of increasing the sodium channel blocking potency of phenol derivatives.

Summary

Background and objective: A study was designed to utilise the resources of our computerised anaesthesia record keeping system to assess the attributable effects of increased preoperative creatinine (>1.3 mg dL−1) on outcome in patients undergoing non-cardiac surgery.

Methods: This retrospective study was based on data sets of 58 458 patients recorded with a computerised anaesthesia record keeping system over a period of 4 yr at a tertiary care university hospital. Cases were defined as patients with a preoperative creatinine >1.3 mg dL−1; controls (creatinine ≤1.3 mg dL−1) were selected and automatically matched according to several parameters (ASA physical status, high risk and urgency of surgery, age and gender) in a stepwise fashion. Main outcome measures were hospital mortality and the incidence of intraoperative cardiovascular events.

Results: Three-thousand-and-twenty-eight patients (5.2%) had preoperative creatinine values >1.3 mg dL−1. Matching was successful for 54.5% of the cases, leading to 1649 cases (mean creatinine 3.3 ± 2.2 mg dL−1) and 1649 controls (1.0 ± 0.2 mg dL−1). The crude mortality rates for the cases and matched controls were 2.2% (n = 36) and 0.9% (n = 15), respectively (P = 0.003). Intraoperative cardiovascular events were found in 30.1% of the patients (n = 496) and in 28.3% of the matched controls (n = 466; P = 0.25, power = 0.46). Using logistic regression analyses a significant association between preoperative increased creatinine and hospital mortality was found (odds ratio 2.62; 95% confidence interval [1.39; 4.93]).

Conclusions: An increased preoperative serum creatinine in patients undergoing non-cardiac surgery is associated with an increased perioperative risk, but not with a higher incidence of intraoperative cardiovascular events.

Summary

Background and objective: To evaluate the different potencies of several opioids in obtunding reflex mechanisms of laryngoscopy and intubation. Methods: Three groups of patients (each n = 25, ASA 1–2) undergoing elective plastic surgery were randomly given meptazinol (2.5 mg kg−1 ), nalbuphine (0.3 mg kg−1) or fentanyl (5 μg kg−1) in a blinded fashion prior to laryngoscopy and intubation. This was followed by a standardized bolus induction of a barbiturate and a muscle relaxant. The response to laryngoscopy and intubation was studied, using blood pressure, heart rate and bispectral index. Results: With fentanyl, there was an increase of heart rate by 17%, and systolic blood pressure by 7% when compared to control. Bispectral index dropped an additional 8% when compared to 1 min after barbiturate induction. In the nalbuphine group there was a 16% increase in systolic blood pressure, and a 16% increase in heart rate when compared to control. Also, bispectral index increased by 18% when compared to 1 min after barbiturate injection. The group receiving meptazinol demonstrated no cardiovascular changes although bispectral index dropped by an additional 19% when compared to 1 min after barbiturate injection. Conclusion: Meptazinol, appears to depress cardiovascular stimulatory effects and electroencephalogram arousal induced by laryngoscopy and intubation better than nalbuphine or fentanyl.

This study compares prospectively the cardiovascular and catecholamine responses to central venous and pulmonary artery catheterization before and after induction of general anaesthesia. Twenty patients for elective coronary artery surgery were randomized into two groups. One group had central venous and pulmonary artery catheterization performed awake using local anaesthesia. The other group had these catheters inserted following induction of general anesthaesia. In all patients heart rate, arterial blood pressure, ST segment analysis and epinephrine and norepinephrine levels were measured prior to central venous cannulation and at 2-min intervals until placement of the lines was achieved. There were no statistically significant changes in any cardiovascular or catecholamine variable with time compared with the base–line measurements. There were no statistically significant differences in plasma catecholamine levels between the awake and the anaesthetized groups.