A comprehensive simple anesthesia record.

BACKGROUND AND OBJECTIVE: Anaesthesiologists need parameters that measure the depth of anaesthesia. In the context of this need, the present study investigated in rats how two variables from the electroencephalogram, the burst suppression ratio and effective correlation dimension correlated with a measure of anaesthetic depth as measured in the strength of a noxious withdrawal reflex. METHODS: Eight rats were exposed to different inspiratory concentrations of sevoflurane, each rat in two separate experiments. In the first experiment, spontaneously breathing animals could move freely and no painful stimuli were applied. In the second experiment, in mechanically ventilated restrained anaesthetized rats, the withdrawal reflex was measured every 80 s. In both experiments the electroencephalogram was continuously recorded. The concentration in the effector compartment was estimated using a first order two compartment model. Correlation dimension was computed following the Grassberger/Procaccia/Takens approach with optimized parameter settings to achieve maximum sensitivity to anaesthetic drug effects and enable real-time computation. The Hill, equation was fitted to the data, describing the effect as a function of sevoflurane concentration. RESULTS: Good correlations of Depth of Anaesthesia with correlation dimension as well as burst suppression ratio were established in both types of experiments. Arousal by noxious stimuli decreased burst suppression ratio and increased correlation dimension. The effective sevoflurane concentration associated with 50% of the maximum effect (C50) was higher in experiment II (stimulation) than in experiment I (no stimulation): i.e. for correlation dimension 2.18% vs. 0.60% and for burst suppression ratio 3.07% vs. 1.73%. The slope factors were: gammaCD = 4.15 vs. gammaCD = 1.73 and gammaBSR = 5.2 vs. gammaBSR = 5.4. Correlation dimension and burst suppression ratio both correlated with the strength of the withdrawal reflex with correlation coefficients of 0.46 and 0.66 respectively (P < 0.001). CONCLUSIONS: Both correlation dimension and burst suppression ratio are related to anaesthetic depth and are affected by noxious stimuli. The relationship between anaesthetic depth and burst suppression ratio is confirmed and the potential of correlation dimension is demonstrated.

Anesthesia↗

PubMed2006

Exendin-4, but not glucagon-like peptide-1, is cleared exclusively by glomerular filtration in anaesthetised pigs.

AIMS/HYPOTHESIS: The insulinotropic hormone, glucagon-like peptide-1 (GLP-1), is rapidly degraded in vivo as a result of the combination of extensive enzymatic degradation and renal extraction. The GLP-1 receptor agonist, exendin-4, has a longer duration of action, and has recently been approved as a new agent for the treatment of type 2 diabetes mellitus. Exendin-4 is less prone to enzymatic degradation, but it is still unclear what other factors contribute to the increased metabolic stability. MATERIALS AND METHODS: The overall metabolism of GLP-1 and exendin-4 was directly compared in anaesthetised pigs (n=9). RESULTS: Metabolism of GLP-1 (C-terminal RIA; t (1/2) 2.0+/-0.2 min, metabolic clearance rate [MCR] 23.2+/-2.8 ml min(-1) kg(-1); N-terminal RIA; t (1/2) 1.5+/-0.2 min, MCR 88.1+/-10.6 ml min(-1) kg(-1)) was significantly faster than the metabolism of exendin-4 (t (1/2) 22.0+/-2.1 min, p<0.0001; MCR 1.7+/-0.3 ml min(-1) kg(-1), p<0.01). Differences in arteriovenous concentrations revealed organ extraction of GLP-1 by the kidneys (C-terminal 56.6+/-2.6%; N-terminal 48.3+/-5.9%), liver (N-terminal 41.4+/-3.8%), and peripheral tissues (C-terminal 42.3+/-6.0%; N-terminal 33.0+/-7.8%), whereas organ extraction of exendin-4 was limited to the kidneys (21.3+/-4.9%). While the renal extraction of exendin-4 (6.9+/-2.5 pmol/min) did not differ significantly from the amount undergoing glomerular filtration (8.4+/-2.0 pmol/min), the renal extraction of C-terminal GLP-1 (9.0+/-1.1 pmol/min), exceeded the amount which could be accounted for by glomerular filtration (4.2+/-0.5 pmol/min, p<0.0005). CONCLUSIONS/INTERPRETATION: In addition to an increased resistance to enzymatic degradation, the increased stability of exendin-4 is the result of reduced differential organ extraction compared to GLP-1. The data suggest that in the anaesthetised pig, extraction occurs only in the kidney and can be fully accounted for by glomerular filtration.

Anesthesia↗