Summary

Background and objective: To compare the inotropic and lusitropic effect of lidocaine and mepivacaine on rat papillary muscle. Methods: Effects of lidocaine and mepivacaine (10−8−10−3 M) were studied in rat left ventricular papillary muscles in vitro at a calcium concentration of 1 mmol, under low (isotony) and high (isometric) loads. Results: Lidocaine induced a significant negative inotropic effect in isotonic and isometric conditions whereas mepivacaine did not. Mepivacaine only induced a negative inotropic effect when added as a bolus for the highest concentration and this effect was significantly more pronounced with lidocaine than with mepivacaine (active force at 10−3 M: 63 ± 10 vs. 84 ± 10% of baseline, P < 0.05). Increasing calcium concentration resulted in a greater positive inotropic effect in the control (199 ± 11% of baseline) and mepivacaine groups (197 ± 22% of baseline) when compared to the lidocaine group (163 ± 19% of baseline, P < 0.05 vs. lidocaine and control groups), suggesting an impairment on intracellular Ca2+ handling by lidocaine. A negative lusitropic effect under low load was observed only for mepivacaine and suggested an impairment of sarcoplasmic reticulum function. Lidocaine and mepivacaine did not modify postrest potentiation but significantly depressed the force–frequency relationship. Conclusions: The negative inotropic and lusitropic effects induced by lidocaine were more important than that of mepivacaine and may involve an impairment of intracellular Ca2+ handling.

It has been estimated that more than 60% of all paediatric surgery is performed on a day case basis. The benefits of this type of surgery in children include reduced costs, avoidance of the stress of hospitalization and less disruption to family life. The growth of day surgery in children has been facilitated by the development of non-depolarizing neuromuscular blocking agents characterized by short and intermediate duration of action and fewer side-effects. The more rapid onset and shorter duration of action of non-depolarizing neuromuscular blocking agents in children should facilitate the use of these agents in place of succinylcholine for day case procedures.

Summary

Background and objective: Recent studies emphasize a positive correlation between (cardiac) surgical interventions and increased risk for developing Alzheimer's disease in the late postoperative period. Since amyloid precursor protein and its neurotoxic derivatives play key roles in the development of Alzheimer's dementia, the impact of several agents used in the intra- and perioperative period is examined. Method: Amyloid precursor protein concentrations were assessed by semi-quantitative Western-immunoblot in brains of rats following intraperitoneal treatment with diazepam and midazolam. Results: There were no significant changes in the amyloid precursor protein concentrations. Conclusion: Both diazepam and midazolam are considered to be relatively safe with respect to amyloid precursor protein metabolism.

An uncontrolled rise in intracranial pressure is probably the most common cause of death in traumatic brain-injured patients. The intracranial pressure rise is often due to cerebral oedema. Diffusion-weighted imaging has been extensively used to study cerebral oedema formation after trauma in experimental studies. Nevertheless, this technology is difficult to perform at the acute phase, especially in unstable head trauma patients. For these reasons, a safe examination allowing us to better understand the pathophysiology of cerebral oedema formation in such patients would be of great interest. Radiological attenuation is linearly correlated with estimated specific gravity in human tissue. This property gives the opportunity to measure in vivo the volume, weight and specific gravity of any tissue by computed tomography. We recently developed a software package (BrainView) for Windows workstations, providing semi-automatic tools for brain analysis from DICOM images obtained from cerebral computed tomography. In this review, we will discuss the results of the in vivo analysis of brain weight, volume and specific gravity and consider the use of this software as a new technology to improve our knowledge of cerebral oedema formation after trauma and to evaluate the severity of traumatic brain-injured patients.

Summary

Background and objective: Computerized dynamic posturography using an intentional postural-sway task can be used to assess body-leaning ability and postural-control ability to prevent falls. Falls are the leading cause of morbidity and mortality for the elderly. The purpose of the present study was to evaluate the recovery of intentional dynamic balance function after intravenous sedation with midazolam in elderly subjects in comparison with that in young subjects. Methods: Midazolam was administered in small, divided doses over 4–5 min until the Wilson sedation score reached three in 20 young and 18 elderly male volunteers. The dynamic limits of the stability test, in which subjects leaned their body intentionally as indicated by a cursor moving on a computer screen, was determined before (baseline) and 50, 70, 90, 110, and 130 min after administration of midazolam. Results: The changes from baseline values of path sway and movement time 50 min after the administration of midazolam in elderly subjects (106.8 ± 101.0%, 4.6 ± 3.0 s; mean ± SD) were significantly greater than those (32.9 ± 87.2%, 1.9 ± 2.8 s) in young subjects (P = 0.024, P = 0.008), respectively. Conclusions: The elderly show slower recovery of the intentional dynamic balance function than do young adults after intravenous sedation with midazolam.

We compared the performance of the size 5 laryngeal mask airway in 20 paralysed anaesthetized male patients and 20 male cadavers (6–24 h post-mortem). Groups were matched for height and weight. Airway sealing pressure, in vivo intracuff pressure and anatomical position (judged fibre-optically) were documented at zero volume and after each additional 10 mL up to 40 mL. All laryngeal mask airways were inserted at the first attempt and insertion times were similar. There were no differences in airway sealing pressure, in vivo intracuff pressure or fibre-optic position between the groups. We conclude that the performance of the laryngeal mask airway is similar for fresh cadavers and paralysed anaesthetized patients. This may have implications for laryngeal mask airway research and training.

Summary

Background and objective: The efficacy of the Trendelenburg position, a common first step to treat suspected hypovolaemia, remains controversial. We evaluated its haemodynamic effects on cardiac preload and performance in patients after cardiac surgery.

Methods: Twelve patients undergoing mechanical ventilation of the lungs who demonstrated left ventricular ‘kissing papillary muscles’ by transoesophageal echocardiography, thus suggesting hypovolaemia, were positioned 30° head down for 15 min immediately after cardiac surgery. Cardiac output by thermodilution, central venous pressure, pulmonary artery occlusion pressure, left ventricular end-diastolic area by transoesophageal echocardiography and intrathoracic blood volume by thermo- and dye dilution were determined before, during and after this Trendelenburg manoeuvre.

Results: Trendelenburg's manoeuvre was associated with increases in central venous pressure (9 ± 2 to 12 ± 3 mmHg) and pulmonary artery occlusion pressure (8 ± 2 to 11 ± 3 mmHg). The intrathoracic blood volume index increased slightly (dye dilution from 836 ± 129 to 872 ± 112 mL m−2; thermodilution from 823 ± 129 to 850 ± 131 mL m−2) as did the left ventricular end-diastolic area index (7.5 ± 2.1 to 8.1 ± 1.7 cm2 m−2), whereas mean arterial pressure and the cardiac index did not change significantly. After supine repositioning, the cardiac index decreased significantly below baseline (3.0 ± 0.6 versus 3.5 ± 0.8 L min−1 m−2) as did mean arterial pressure (76 ± 12 versus 85 ± 11 mmHg), central venous pressure (8 ± 2 mmHg) and pulmonary artery occlusion pressure (6 ± 4 mmHg). The intrathoracic blood volume index and left ventricular end-diastolic area index did not differ significantly from baseline.

Conclusions: Trendelenburg's manoeuvre caused only a slight increase of preload volume, despite marked increases in cardiac-filling pressures, without significantly improving cardiac performance.

We investigated the influence of intravenous clonidine 2, 4 and 6 μg kg−1 on the electroencephalogram and on the minimal alveolar concentration of isoflurane in 40 patients aged 20–60 years undergoing elective surgery. Minimal alveolar concentration was determined using the Dixon ‘up-and-down’ method. Thirty min after the clonidine infusion anaesthesia was induced with etomidate, 0.25 mg kg−1. Skin incision was made after stable end-tidal isoflurane concentrations had been maintained for at least 15 min. Clonidine caused significant decreases in the spectral edge (95%) and median power frequency of the electroencephalogram and in the bispectral index. The minimal alveolar concentration of isoflurane decreased in a dose-dependent manner from 1.32% (95% CI, 1.28%–1.36%) in the control group to 1.03% (0.9%–1.18%) in patients given clonidine 6 μg kg−1. Clonidine 4 and 6 μg kg−1 was associated with a moderate reduction in heart rate and arterial systolic blood pressure. We recommend the use of clonidine intravenously as an adjunct to general anaesthesia in a dose of 4 μg kg−1 given 15 min before induction of anaesthesia.

Summary

Background and objectives: A difficult issue in anaesthesia is its titration for an individual patient to avoid over- and underdosage. Common practice is to use an initial dose and increase it subsequently if the defined end-point is not reached. This assumes that the end-point is reached after a similar interval of time in all patients given a similar dose. In order to test this hypothesis we measured the time to reach end-points such as loss of consciousness (LOC), a bispectral index (BIS®) value of 60, the minimal BIS and the minimal mean arterial pressure (MAP) values. Methods: Thirty patients aged 18–60 yr scheduled for general surgery were included in this observational study. After preoxygenation, induction was performed with 6% inspired concentration of sevoflurane in 6 Lmin−1 oxygen using the SiBI® connector and the tidal volume technique. Remifentanil was administered when the BIS value was 60 and tracheal intubation was performed 4 min later. Results: Time (median, minimum–maximum) to LOC, a BIS value of 60, the minimal BIS and MAP values were, respectively, 75 (45–135), 120 (75–270), 300 (120–720) and 450 (120–1200) seconds. The time to the minimal BIS value was significantly (P < 0.05) shorter than the time to reach the minimal MAP value. Conclusions: These results demonstrate large inter-patient variability for the time necessary to reach defined end-points of depth of anaesthesia when a similar dose of anaesthetic is given. Measuring the time to reach a predefined BIS value would allow application of nociceptive stimuli only at adequate levels of hypnosis and would facilitate titration.