Convulsions on anaesthetic induction with sevoflurane in young children.

Increased worldwide use for paediatric anaesthesia of the volatile anaesthetic agent sevoflurane has mainly resulted from its low blood-gas partition coefficient and low airway irritability, providing smooth conditions for rapid induction of anaesthesia. Nevertheless, there are several clinical and experimental reports suggesting a correlation between exposure to sevoflurane and generalized clonic or tonic seizure activity. We report two clinical episodes of convulsions associated with the induction of sevoflurane anaesthesia in young children. Case 1: during induction of anaesthesia with sevoflurane by facemask in a 3-year-old healthy boy, there were symmetrical clonic seizure-like movements of the upper extremities for 60 s. Case 2: on re-induction of anaesthesia with sevoflurane because of profuse bleeding following nasal adenoidectomy in a 4-year-old healthy girl with a family history of epilepsy, there were symmetrical tonic and clonic seizure-like movements for 30-40 s in the upper and lower extremities. Both episodes ceased spontaneously. Although no EEG was recorded, it cannot be excluded that both episodes resulted from seizure activity within the CNS. Based on our observations and reports by others we suggest that, until further notice, sevoflurane should be avoided or at least used cautiously in patients where clinical epileptic activity has been verified or is strongly suspected

Racemic, S(+)- and R(-)-ketamine do not increase elevated intracranial pressure

Background: There is controversy regarding the influence of ketamine and its enantiomers on cerebral haemodynamics at increased intracranial pressure (ICP). This study was designed to compare cerebrovascular responses, with particular respect to ICP, to bolus injections of racemic, S(+)- and R(-)-ketamine in an experimental model of intracranial hypertension. Methods: Nine pigs were anaesthetised with fentanyl and vecuronium during mechanical normoventilation. The ICP was raised with extradural balloon catheters to 23 mmHg. The intra-arterial xenon clearance technique was used to determine cerebral blood flow (CBF). Three 60-s bolus injections of racemic ketamine (10 mg/kg), S-ketamine (5 mg/kg) and R-ketamine (20 mg/kg) were given in a randomised sequence. Cerebral and systemic haemodynamic responses were evaluated before and at 1, 5, 10, 15, 30 and 45 min after each injection. Results: Racemic ketamine decreased ICP (P = 0.026) by maximally 10.8%, whereas there was no effect on ICP of S- (P = 0.178) or R-ketamine (P = 0.15). All study drugs had similar biphasic effects on CBF, with maximal initial decreases by 25-29%, followed by transient increases by 7-15%, and a reduction of mean arterial pressure by maximally 22-37%. Conclusions: A decrease or a lack of an increase in ICP in response to intravenous bolus injections of racemic, S- or R-ketamine suggests that the administration of racemic or S-ketamine might be safe in patients with intracranial hypertension due to a space-occupying lesion. The ICP-lowering effect indicates that racemic ketamine might offer a therapeutic advantage over S-ketamine

Randomisierte Cross-Over-Bewertung vom Geschlecht des Untersuchers auf die Schmerzschwelle bei gesunden Freiwilligen

Background and aims: This randomized cross-over study in healthy volunteers was designed primarily to evaluate the potential impact of investigator gender on electrical pain threshold (EPT) and corresponding pain intensity levels, and secondly to evaluate potential differences in those interventions between female and male study participants.Methods: Forty adult volunteers (22 females) were included. An electrical stimulation device was used to determine EPT levels (in pain magnitude scores) in series of three in each study participant - once by a female, and once by a male investigator - according to a predefined cross-over design schedule. Corresponding levels of pain intensity were scored on a visual analog scale (VAS) slide ruler.Results: Study data was obtained and analysed in all participants. Significantly higher EPT levels were determined by the female investigator compared with the male investigator (median 22 (IQR 12-31) vs. 8 (6-10) pain magnitude scores; p 0.300). There were no differences in EPT levels between female and male subjects evaluated by female (p >0.300) and male (p =0.125) investigators, or between the first and second series of stimulation (p >0.300).Conclusions: Our finding of significantly higher EPT levels when study participants of both genders - despite no difference in reported pain intensity - were evaluated by a female than by a male investigator, indicates a potential impact of investigator gender on the individual perception of pain.Implications: By contributing to a better understanding of how individual pain threshold levels are potentially influenced by investigator gender, this study might facilitate future evaluation of pain conditions in both preclinical and clinical settings.Hintergrund und Ziele: Diese präklinische randomisierte Cross-Over-Studie wurde entwickelt, um 1) einen möglichen Einfluss des Geschlechts der Untersucher auf die Schwellenwerte für elektrische Schmerzen (EPT) und entsprechende Schmerzintensität bei gesunden Freiwilligen zu bewerten, und 2) mögliche Unterschiede bei diesen Interventionen zwischen weiblichen und männlichen Studienteilnehmern zu bewerten.Methoden: Vierzig gesunde erwachsene Freiwillige (22 Frauen) wurden eingeschlossen. Mit einem elektrischen Stimulationsgerät wurden die EPT-Spiegel in Dreierreihen bei jedem Studienteilnehmer - einmal von einem weiblichen und einmal von einem männlichen Untersucher - gemäß einem vordefinierten Cross-Over-Entwurfsplan bestimmt. Entsprechende Niveaus der Schmerzintensität wurden auf einem VAS-Lineal bewertet.Ergebnisse: Studiendaten wurden bei allen Teilnehmern erhoben und analysiert. Im Vergleich zum männlichen Untersucher wurden von der weiblichen Untersucherin signifikant höhere EPT-Spiegel bestimmt (Median 22 (IQR 12-31) vs. 8 (6-10) Schmerzstärkeneinheiten; p 0,300). Es gab keine Unterschiede in EPT zwischen weiblichen und männlichen Teilnehmern, die von weiblichen (p >0,300) und männlichen (p =0,125) Untersuchern bewertet wurden, oder zwischen der ersten und zweiten Stimulationsreihe (p >0,300).Schlussfolgerungen: Dass signifikant höhere EPT-Werte bei Studienteilnehmern beiden Geschlechts vorlagen, wenn sie von einer weiblichen statt einer männlichen Person untersucht wurden - trotz gleicher gemeldeter Schmerzintensität -, zeigt einen möglichen Einfluss des Geschlechts des Untersuchers auf die individuelle Wahrnehmung von Schmerz.Implikationen: Durch diesen Beitrag zu einem besseren Verständnis, wie die individuellen EPT-Werte möglicherweise vom Geschlecht des Untersuchers beeinflusst werden, könnte diese Studie die zukünftige Bewertung von Schmerzzuständen sowohl im präklinischen als auch im klinischen Umfeld erleichtern

Cerebral haemodynamic and electrocortical CO2 reactivity in pigs anaesthetized with fentanyl, nitrous oxide and pancuronium

Cerebral haemodynamic, metabolic and electrocortical reactivity to alterations in arterial CO2 tension (PaCO2) was assessed in seven mechanically ventilated juvenile pigs to test an experimental model designed for cerebral pharmacodynamic and pharmacokinetic studies. The animals were anaesthetized with fentanyl, nitrous oxide and pancuronium and sequentially normo- and hyperventilated over a 100-min period. Five measurements were made at 25-min intervals. The cerebral blood flow (CBF) was measured with the intra-arterial 133Xe technique and the cerebral metabolic rate for oxygen (CMRO2) determined from CBF and the cerebral arteriovenous oxygen content difference. A linear correlation (r = 0.845) was found between CBF and PaCO2. The cerebrovascular reactivity to hypocapnia (delta CBF/delta PaCO2) was maintained throughout the experimental period and amounted to (95% confidence interval) 9.1 (7.1-11.1) ml x 100 g-1 x min-1 x kPa-1 within the PaCO2 range 3.3-6.3 kPa. The CMRO2 was not influenced by hyperventilation. The baseline electroencephalographic (EEG) pattern was stable at normocapnia (mean PaCO2 5.6 kPa), whereas spectral values for delta and total average voltage increased significantly (P < 0.05) at extensive hypocapnia (3.5 kPa). Maintenance of cerebral CO2 reactivity and spectral EEG voltage at a stable plasma level of fentanyl is complementary to the cerebral haemodynamic and metabolic stability previously found at sustained normocapnia in this model

Contrast-enhanced MRI of the central nervous system: comparison between gadodiamide injection and gadolinium-DTPA

Gadodiamide injection, a new nonionic, MRI contrast medium, was compared with the ionic agent gadolinium (Gd)-DTPA at 0.1 mmol/kg body weight in a double-blind, randomised trial in 60 patients, 30 receiving each substance, with known or suspected lesions of the central nervous system. The patients were closely questioned about adverse events. In the Gadodiamide injection group, four patients reported six adverse advents, three of which were judged to be related to the contrast medium. In the Gd-DTPA group, two patients each reported one adverse event, both of which had an uncertain relation to the contrast medium. All events were mild and no medical treatment was needed. No significant change in neurological findings, blood pressure, pulse rate or blood parameters were noted in any patient. Both contrast media were effective; no difference in overall efficacy or safety was observed

Cerebral pharmacodynamics of anaesthetic and subanaesthetic doses of ketamine in the normoventilated pig

There are still divergent opinions regarding the pharmacodynamic effects of ketamine on the brain. In this study, the cerebral blood flow (CBF), cerebral metabolic rate for oxygen (CMRO2) and electroencephalographic (EEG) activity were sequentially assessed over 80 min in 17 normoventilated pigs following rapid i.v. infusions of anaesthetic (10.0 mg.kg-1; n = 7) or subanaesthetic (2.0 mg.kg-1; n = 7) doses of ketamine or of its major metabolite norketamine (10.0 mg.kg-1; n = 3). The animals were continuously anaesthetized with fentanyl, nitrous oxide and pancuronium. CBF was determined by the intra-arterial 133Xe technique. Ketamine (10.0 mg.kg-1) induced an instant, gradually reverting decrease in CBF, amounting to -26% (P < 0.01) at 1 min and -13% (P < 0.05) at 10 min, a delayed increase in CMRO2 by 42% (P < 0.01) at 10 min and a sustained rise in low- and intermediate-frequency EEG voltage by 87% at 1 and 97% at 10 min (P < 0.0001). It is concluded that metabolically formed norketamine does not contribute to these effects. Considering the dissociation of CBF from CMRO2 found 10-20 min after ketamine (10.0 mg.kg-1) administration, it is suggested that ketamine should be used with caution for anaesthesia in patients with suspected cerebral ischaemia in order not to increase the vulnerability of brain tissue to hypoxic injury. Ketamine (2.0 mg.kg-1) had no significant effects on CBF, CMRO2 or EEG. It therefore seems that up to one fifth of the minimal anaesthetic i.v. dose can be used safely for analgesia, provided that normocapnaemia is preserved

The incidence and risk of central venous catheter malpositioning: a prospective cohort study in 1619 patients.

Central venous catheters are used in various hospital wards. An anterior-posterior chest X-ray is usually obtained soon after cannulation to assess the location of the catheter tip. This prospective clinical study was designed to determine the radiographic catheter tip position after central venous cannulation by various routes, to identify clinical problems possibly associated with the use of malpositioned catheters and to make a cost-benefit analysis of routine chest X-ray with respect to catheter malposition. A total 1619 central venous cannulations were recorded during a three-year period with respect to patient data, information about the cannulation procedures, the radiographic catheter positions and complications during clinical use. The total incidence of radiographic catheter tip malposition, defined as extrathoracic or ventricular positioning, was 3.3% (confidence interval 25 to 4.3%). Cannulation by the right subclavian vein was associated with the highest risk of malposition, 9.1%, compared with 1.4% by the right internal jugular vein. Six of the 53 malpositioned catheters were removed or adjusted. No case of malposition was associated with vascular perforation, local venous thrombosis or cerebral symptoms. We conclude that the radiographic incidence of central venous catheter malpositioning is low and that clinical use of malpositioned catheters is associated with few complications. However, determination of the catheter position by chest X-ray should be considered when mechanical complications cannot be excluded, aspiration of venous blood is not possible, or the catheter is intended for central venous pressure monitoring, high flow use or infusion of local irritant drugs

Routine chest X-ray is not required after a low-risk central venous cannulation.

Background: Knowledge of the radiographic catheter tip position after central venous cannulation is normally not required for short-term catheter use. Detection of a possible iatrogenic pneumothorax may nevertheless justify routine post-procedure chest X-ray. Our aim was to design a clinical decision rule to select patients for radiographic evaluation after central venous cannulation. Methods: A total of 2230 catheterizations performed using external jugular, internal jugular or subclavian venous approaches during a 4-year period were included consecutively. Information on patient data and corresponding procedures was recorded prospectively. A post-procedure chest X-ray was obtained after each cannulation. Results: Thirteen cases (0.58%) of cannulation-associated pneumothorax were identified. The risk of pneumothorax after a technically difficult (1.8%) or subclavian (1.6%) cannulation was significantly higher than after cannulation not considered as difficult (0.37%) or performed using other routes (0.33%). Clinical signs of pneumothorax within 8 h of cannulation were found in all seven patients with pneumothorax requiring specific treatment. A new clinical decision rule for radiographic evaluation after central venous cannulation based on the results of the present study shows that 48% of the post-procedure chest X-rays performed in our patients were clinically redundant. Conclusion: Clinical symptoms were reported in all patients with pneumothorax requiring specific treatment. Approximately half of the post-procedure chest X-ray controls could be avoided using the proposed clinical decision rule to select patients for radiographic evaluation after central venous cannulation. A large prospective multi-centre study should be carried out to further evaluate this decision rule