British journal of anaesthesia
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Comparative Study
Midazolam versus propofol for reducing contractility of fatigued canine diaphragm.
The effects of midazolam and propofol on the contractility of fatigued canine diaphragm were examined. Diaphragmatic fatigue was induced by intermittent supramaximal bilateral electrophrenic stimulation at a frequency of 20 Hz applied for 30 min. After fatigue had been induced, group I (n=10) received no study drug, group II (n=10) was given a propofol infusion (0.1 mg kg(-1) loading dose plus 1.5 mg kg(-1) h(-1) maintenance dose) and group III (n=10) was given a midazolam infusion (0.1 mg kg(-1) loading dose plus 0.1 mg kg(-1) h(-1) maintenance dose). ⋯ Compared with group I, Pdi at 20 Hz stimulation was lower than fatigued values (P<0.05) during administration of the study drug in groups II and III. The decrease in Pdi was greater in group III than in group II (P<0.05). In conclusion, midazolam compared with propofol is associated with an inhibitory effect on contractility in the fatigued canine diaphragm.
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Comparative Study
Downward movement of syringe pumps reduces syringe output.
We studied how lowering a syringe pump and changing the outflow pressure could affect syringe pump output. We experimentally reduced the height of three different syringe pump systems by 80 cm (adult setting) or 130 cm (neonatal setting), as can happen clinically, using five flow rates. We measured the time of backward flow, no flow and the total time without flow. ⋯ The compliance of the different syringe pumps and their infusion systems was linearly correlated with the effective time without infusion (r2=0.863, P<0.05). We conclude that the height of the syringe pumps should not be changed during transportation. If vertical movement of the syringe pump is necessary, the drugs should be diluted so that the flow rate is at least 5 ml h(-1).
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Several risk scores have been developed to calculate the probability of postoperative nausea and vomiting (PONV). However, the power to discriminate which individual will suffer from PONV is still limited. Thus, we wondered how the number of predictors in a score affects the discriminating power and how the characteristics of a population--which is needed to measure the power of a score--may affect the results. ⋯ The currently available simplified risk scores (with four or five predictors) are useful both as a method to estimate individual risk of PONV and as a method for comparing groups of patients for antiemetic trials. They are also superior to single predictor models which are just using the patients' history of PONV or female gender alone. However, our analysis suggests that the power to discriminate which indvidual will suffer from PONV will remain imperfect, even when more predictors are considered.
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Propofol is used in the peri-operative setting and may affect some neutrophil functions. The effects of propofol on the function and intracellular signal transduction systems of neutrophils is controversial. Mitogen-activated protein kinase families (MAPKs) are members of the intracellular signal-transducing systems in eukaryotes. ⋯ The phosphorylation of p42 MAPK and chemotaxis stimulated by FMLP were both inhibited by propofol at clinically relevant concentrations (> or = 10 and > or = 20 microM respectively). PD98059 (50 microM) also inhibited chemotaxis stimulated by FMLP, suggesting the involvement of p42 MAPK in the response. Propofol might therefore inhibit human neutrophil chemotaxis, at least in part, by suppressing the p44/42 MAPK pathway.
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The level of sedation of 28 patients undergoing elective coronary artery bypass grafting with fentanyl-propofol anaesthesia was monitored with bispectral analysis (BIS), spectral edge frequency, and band power of the electroencephalogram. Fourteen patients underwent hypothermic cardiopulmonary bypass (CPB) (32 degrees C, group H), and 14 normothermic CPB (group N). The level of sedation was measured with Observer's Assessment of Alertness/Sedation Score and with Ramsay Sedation Score. ⋯ During the phases of anaesthesia and surgery without CPB, the progression of BIS levels was comparable with previously published data for non-cardiac surgery. During normothermic CPB, the highest BIS values were close to values representing insufficient depth of sedation. It remains to be elucidated whether the much lower BIS values in the hypothermic group were solely a result of brain cooling or if increased serum propofol concentrations, because of slowed pharmacodynamics during hypothermia, also contributed.