Summary

Background and objective: Propofol may cause undesirable hypotension due to vasodilation. The underlying mechanisms are not completely understood. We investigated the mechanisms by which propofol relaxes vascular segments.

Methods: We studied the effect of propofol on isolated porcine coronary artery rings precontracted with potassium chloride or prostaglandin F2α.

Results: Propofol, in a concentration-dependent manner, relaxed all segments at concentrations of 5 μg mL−1 and above. This relaxation was unaltered in the presence of Nω-nitro-L-arginine, indomethacin, diltiazem and glibenclamide. Tetraethylammonium chloride, an inhibitor of the BKCa K+ channel (a high conductance Ca2+-sensitive K+ channel), dose-dependently attenuated the vasodilating effect of propofol (P < 0.001).

Conclusions: Our results suggests that the activation of the BKCa channel may contribute to the vasodilating effect of propofol, hereby causing hyperpolarization of the smooth muscle membrane and reduction of smooth muscle tone.

Summary

Background and objective: The aim of this study was to investigate the quality of intra- and postoperative analgesia obtained by alfentanil compared to that produced by peripheral blockade in children.

Methods: During sevoflurane-nitrous oxide atracurium anaesthesia for minor abdominal or genito-urinary surgery, three groups of children aged 0–8 yr received 25 μg kg−1 alfentanil intravenously (n = 28), or peripheral nerve blockade using 1 mL−1 ropivacaine 0.475% (n = 24), or 12.5 μg kg−1 alfentanil intravenously with peripheral nerve blockade using 1 mL kg−1 ropivacaine 0.475% (n = 30). Changes in blood pressure and heart rate were measured during the procedures. Postoperative pain was assessed using the face, legs, activity, cry, consolability (FLACC) observational tool for quantifying pain behaviour and a numerical scale scored by nurses, doctors, parents and children.

Results: There was no significant difference in intra- or postoperative analgesic efficacy among the three groups. Patients who received alfentanil had significantly lower heart rates than those who received nerve blockade only (96.0 ± 15.6 vs. 115.9 ± 23.2 beats min−1, P < 0.001). FLACC and numerical scale scores did not differ among the groups. There were no significant differences in incidence of vomiting or use of pain medications.

Conclusions: It was concluded that a low-dose, intravenous bolus of alfentanil may be an efficient alternative to peripheral nerve blockade in controlling pain during and after minor abdominal and genito-urinary surgery.

Summary

Background and objective: To analyse the use of standardized application of ryanodine for in vitro muscle contracture testing to define cut-off values separating malignant hyperthermia susceptible from malignant hyperthermia negative subjects. Furthermore, we compared the results of in vitro muscle-contracture tests following the halothane, caffeine and ryanodine challenges.

Methods: In 113 subjects, halothane, caffeine and ryanodine muscle-contracture tests were performed according to the protocol of the European Malignant Hyperthermia Group.

Results: Malignant hyperthermia susceptible subjects (n = 77) had significantly shorter onset times in the ryanodine in vitro muscle-contracture test (1 μmol ryanodine) compared with malignant hyperthermia negative subjects (n = 36), median 4.8 vs. 20.1 min, respectively, without any influence of age or gender. The best cut-off value was 10 min (sensitivity 0.78 and specificity 0.94, respectively). Shorter cut-off values had greater specificity, but lower sensitivity. Groups could not be separated without an overlap. In susceptible subjects, we found a correlation between onset time and threshold concentrations for halothane and caffeine (ρ = 0.47 and 0.52, respectively). In addition, muscle bundles with high susceptibility to halothane and caffeine also showed high susceptibility to ryanodine.

Conclusions: The ryanodine in vitro muscle-contracture test confirmed the malignant hyperthermia status that was determined using the halothane and caffeine in vitro muscle-contracture tests. Due to an overlap between the two groups, discrimination ability was not always perfect and short cut-off values with higher specificity had reduced sensitivity and vice versa. The correlation of contractures following the halothane, caffeine and ryanodine challenges points towards a similar individual pharmacogenetic effect rather than a specific, different pharmacological action between the three agents.

Summary

Background and objective: To investigate the effects of moderate hyponatraemia, induced by intravenous application of an electrolyte-free irrigation fluid, as a model of the human transurethral prostate resection syndrome and of its rapid correction by hypertonic saline infusion in rats.

Methods: Experimental animals received irrigation fluid (Purisole SM®) 20 mL kg−1 body weight, intravenously. In one group, hyponatraemia was subsequently rapidly corrected by infusion of hypertonic saline (NaCl 5.85%), while rats of group two were ‘sham-corrected’ by infusion of a balanced salt crystalloid solution. Plasma sodium concentrations were analysed during and at the end of the experiments. After 10 days, experimental and untreated control animals were killed humanely, fixed by perfusion and the brains were prepared for electron microscopic investigation of myelin sheets and glial cell numbers in the striatum and pons.

Results: The myelin appearance was unaltered in experimental groups compared to controls, but glial cell numbers were distinctly altered in the pons but not in the striatum. In the pons, oligodendrocytes were significantly reduced in number upon rapid correction of hyponatraemia, while astrocyte numbers were increased in rats with uncorrected hyponatraemia.

Conclusions: Our electron microscopic data demonstrate that the effects of hyponatraemia and of its rapid correction are multifarious in animals. This may also apply for human patients during transurethral prostate resection.

Summary

Background and objective: Cervical spine movement may be limited for morphological reasons or through injury. The major goal of the present study was to evaluate the three-dimensional cervical spine movement during intubation with a Macintosh or Bullard laryngoscope, a Bonfils fibrescope or an intubating laryngeal mask using an ultrasound-based motion system.

Methods: Forty-eight patients without any history of cervical spine problems who had to undergo elective surgery in general anaesthesia were intubated using a Macintosh or Bullard laryngoscope, a Bonfils fibrescope or an intubating laryngeal mask airway. During intubation, cervical motion as well as overall time to intubation, number of attempts, and postoperative complaints were noted.

Results: The range of cervical spine motion during intubation, especially concerning extension, using the Macintosh laryngoscope was much greater (22.5° ± 9.9°) than using Bullard (3.4° ± 1.4°), Bonfils (5.5° ± 5.0°) or intubating laryngeal mask (4.9° ± 2.1°). Time to intubate the trachea using Bonfils (52.1 ± 22.0 s) and intubating laryngeal mask (49.8 ± 18.7 s) were much longer than with Macintosh (18.9 ± 7.1 s) and Bullard laryngoscope (16.1 ± 6.2 s) (significance level: 0.05).

Conclusions: Our findings suggest that the Bullard laryngoscope may be a useful adjunct to intubate patients with cervical spine injuries. In elective situations when time to intubation is not critical Bonfils as well as intubating laryngeal mask airway should also be considered as serious alternatives to direct laryngoscopy.