Propofol attenuates responses of the auditory cortex to acoustic stimulation in a dose-dependent manner: a FMRI study.

BACKGROUND: Functional magnetic resonance imaging (fMRI) using blood-oxygen-level-dependent (BOLD) contrasts is a common method for studying sensory or cognitive brain functions. The aim of the present study was to assess the effect of the intravenous anaesthetic propofol on auditory-induced brain activation using BOLD contrast fMRI. METHODS: In eight neurosurgical patients, musical stimuli were presented binaurally in a block design. Imaging was performed under five conditions: no propofol (or wakefulness) and propofol plasma target concentrations of 0.5, 1.0, 1.5, and 2.0 microg ml(-1). RESULTS: During wakefulness we found activations in the superior temporal gyrus (STG) corresponding to the primary and secondary auditory cortex as well as in regions of higher functions of auditory information processing. The BOLD response decreased with increasing concentrations of propofol but remained partially preserved in areas of basic auditory processing in the STG during propofol 2.0 microg ml(-1). CONCLUSIONS: Our results suggest a dose-dependent impairment of central processing of auditory information after propofol administration. These results are consistent with electrophysiological findings measuring neuronal activity directly, thus suggesting a dose-dependent impairment of central processing of auditory information after propofol administration. However, propofol did not totally blunt primary cortical responses to acoustic stimulation, indicating that patients may process auditory information under general anaesthesia.

[Why does blood have a pH-value of 7.4? The theory of acid-base management]. / Warum liegt der pH-Wert des Blutes bei 7.40? Zur Theorie des Säure-Basen-Haushalts.

Aim of the present paper is to discuss the physiologic principles of the acid-base status, in particular those of the pH value. The alpha-stat theory of acid-base management interprets the normal value of arterial pH, usually thought of as being 7.40, as a value derived from the intracellular pH, which is close to neutrality. This appears to have offered an evolutionary advantage, since most of the intermediates in biosynthetic pathways are ionized at neutrality resulting in a decreased rate of penetration across biological membranes of these compounds thus producing a benefit for the economy of a cell. Finally, we present the clinical implications of both the alpha-stat and the pH-stat strategy of acid-base management.

[Detection of air embolism by a re-usable Doppler probe integrated in a central venous line--application in-vivo]. / Wiederverwendbare, in einen Zentralvenenkatheter integrierbare Dopplersonde zur Detektion von Luftembolien Anwendung in-vivo.

PROBLEM: Air embolism frequently occurs under neurosurgical operations performed in the sitting position. Recently we reported the idea of inserting a re-usable doppler probe into a blind-ending lumen of a central venous catheter (Schregel-Volk-Catheter, SVC). In vitro testing in a circulation model showed a high sensitivity: air bubbles as small as 0.5 microliter were reliably detected at a distance up to 4 cm from the tip of the SVC. METHOD: After approval by the local ethics committee pigs were anaesthetised and a cardiopulmonary bypass was connected. During the bypass period a 12 F SVC (Medex Medical, Germany) with one blind-ending lumen was positioned into the proximal vena cava cranialis or vena cava caudalis. An 8 MHz doppler probe (MTB Basler, Suisse) was introduced into the SVC and connected with the doppler device Multi-Dop T (DWL, Germany). Well defined air bubbles (3-6 microliter) were generated by a bubble generator and injected into the right femoral vein or the left vena jugularis interna. RESULTS: All bubbles were reliably detected by the re-usable doppler probe. Embolic events can be documented, counted and quantified by the Multi-Dop T. CONCLUSION: Using SVC's with a blind-ending lumen could improve and simplify the detection of air embolism. We see several advantages (e.g. sensitivity, costs) compared with established methods (precordial doppler, TEE) for detection of air embolism.

Influence of dextran on the absorption of adrenaline-containing lignocaine solutions: a protective mechanism in local anaesthesia.

The effect of adding 6% dextran to a lignocaine solution containing adrenaline was studied in 27 neurosurgical patients during modified neuroleptanaesthesia. Before trepanation they received infiltration anaesthesia of the scalp at the site of the proposed operation. For a period of 1 h following injection plasma concentrations of adrenaline were measured by high pressure liquid chromatography and serum concentrations of lignocaine by gas chromatography. The addition of dextran caused a significant reduction in the absorption of both adrenaline and lignocaine from the injection site. It is concluded that the dextran adjuvant constitutes a protective mechanism against toxic systemic side effects in local anaesthesia using adrenaline-containing anaesthetic solutions. This effect is particularly significant in patients with pre-existing cardiovascular disease and when local anaesthetic solutions are used in combination with volatile anaesthetics.

Diagnosis and treatment of Amanita phalloides-type mushroom poisoning: use of thioctic acid.

The number of cases of mushroom poisoning is increasing as a result of the increasing popularity of "wild" mushroom consumption. Amanitin and phalloidin cytotoxins found in some Amanita and Galerina species produce the most severe and frequent life-threatening symptoms of Amanita phalloidestype poisoning. Delay in onset of symptoms, individual susceptibility variation and lack of rapid and reliable identification have contributed to the significant morbidity and mortality of this type of poisoning.A rapid chromatographic assay for identifying the potent cytotoxins and apparently successful management using thioctic acid of two cases of A. phalloides-type mushroom poisoning are reported. All known cases of A. phalloides-type mushroom poisoning treated with thioctic acid in the United States are summarized.

Phencyclidine poisoning.

Phencyclidine hydrochloride abuse has become increasingly common and should be considered in patients with unexplained acute psychosis, dystonic reactions, status epilepticus, or coma. Two phencyclidine-intoxicated patients had bizarre combinations or disorientation, hallucination, agitation, and dyskinetic motor activity. Supportive care and reduction of sensory stimulation are the basis for management of the symptoms.

Coma, hyperthermia, and bleeding associated with massive LSD overdose, a report of eight cases.

Eight patients were seen within 15 min of intranasal self-administration of large amounts of pure D-lysergic acid diethylamide (LSD) tartrate powder. Emesis and collapse occurred along with sign of sympathetic overactivity, hyperthermia, coma, and respiratory arrest. Mild generalized bleeding occurred in several patients and evidence of platelet dysfunction was present in all. Serum and gastric concentrations of LSD tartrate ranged from 2.1 to 26 ng/ml and 1000 to 7000 mug/100 ml, respectively. With supportive care, all patients recovered. Massive LSD overdose in humans is life-threatening and produces striking and distinctive manifestations.

Coma, hyperthermia and bleeding associated with massive LSD overdose. A report of eight cases.

Eight patients were seen within 15 minutes of intranasal self-administration of large amounts of pure D-lysergic acid diethylamide (LSD) tartrate powder. Emesis and collapse occurred along with signs of sympathetic overactivity, hyperthermia, coma and respiratory arrest. Mild generalized bleeding occurred in several patients and evidence of platelet dysfunction was present in all. Serum and gastric concentrations of LSD tartrate ranged from 2.1 to 26 nanograms per ml and 1,000 to 7,000 mug per 100 ml, respectively. With supportive care, all patients recovered. Massive LSD overdose in man is life-threatening and produces striking and distinctive manifestations.