Use of cisatracurium during fast-track cardiac surgery.
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We prospectively studied spontaneous recovery from cisatracurium-induced neuromuscular block in 18 patients scheduled for cardiac surgery, and its suitability for fast-track cardiac surgery. Neuromuscular block was induced by an i.v. bolus (range 0.15-0.3 mg kg(-1)) and maintained by a continuous infusion (range 1.1-3.2 microg kg(-1) min(-1)) of cisatracurium until sternal closure. In the intensive care unit (ICU), spontaneous recovery was evaluated by the train-of-four (TOF) ratio measured at the adductor pollicis muscle. The ICU medical staff were unaware of the TOF ratios until sedation was stopped. At that time, if the TOF ratio was less than 0.9, sedation was recommenced. On arrival in ICU, all patients had residual paralysis. The mean time to reaching a TOF ratio of at least 0.9 was 102 min (range 74-144 min) after discontinuation of the cisatracurium infusion. Fifteen patients (83%) were successfully extubated during the first 8 h after stopping the cisatracurium infusion. Only one patient showed residual paralysis when sedation was discontinued. These results support the use of cisatracurium as a suitable neuromuscular blocking agent for fast-track cardiac surgery. (+info)
Pharmacokinetics and dynamics of atracurium infusions after paediatric orthotopic liver transplantation.
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We examined the pharmacokinetics and pharmacodynamics of atracurium besylate and its metabolites in children after orthotopic liver transplantation (OLT), as a suitable model for critically ill children. Ten children were studied after OLT on return to the intensive care unit (ICU). The mean (range) age was 36 (7-78) months, and weight 6-24.2 kg. Atracurium was started at induction of anaesthesia and adjusted in the ICU according to clinical need. Neuromuscular block was measured using accelerometry (TOFguard) and the train-of-four (TOF) ratio or count. Arterial plasma samples for atracurium and metabolites taken before, 12-hourly during, and at frequent intervals after the infusion were analysed by HPLC. The mean (range) maximum infusion rate during steady-state conditions was 1.44 (0.48-3.13) mg kg(-1) h(-1) and the duration of infusion 36.9 (22.5-98.4) h. Tachyphylaxis was not observed. The mean terminal half-life (t1/2) for atracurium was 18.8 (12-32.3) min. The steady-state plasma clearance (CLss) was 13.9 (7.9-20.3) ml min(-1) kg(-1) and the terminal volume of distribution (Vz) 390 (124-551) ml kg(-1); both were higher than in adults after successful OLT. The maximum concentration (Cmax) of laudanosine was 1190 (400-1890) ng ml(-1) and t1/2 was 3.9 (1.1-6.7) h. The renal clearance of laudanosine was 0.9 (0.1-2.5) ml min(-1) kg(-1) and increased with urine flow, but there was no significant relationship with serum creatinine. EEG spikes were confirmed in one child only; the corresponding laudanosine Cmax was 720 ng ml(-1). Monoquaternary alcohol Cmax was 986 (330-1770) ng ml(-1) and t1/2 42.9 (30-57.7) min. Mean recovery time on stopping the atracurium infusion to a TOF ratio >0.75 was 23.6 (12-27) min. Atracurium is an effective and safe neuromuscular blocking agent in this population. Laudanosine concentrations are not excessive if graft function is satisfactory. (+info)
The new neuromuscular blocking agents: do they offer any advantages?
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The pharmacodynamics and pharmacokinetics of the two most recent aminosteroid neuromuscular blocking drugs to become available, rapacuronium bromide (Org 9487) and rocuronium bromide are reviewed. Two new classes of drug with neuromuscular blocking properties, the bis-tetrahydroisoquinolinium chlorofumarates and the tropinyl diester derivatives are introduced. Comparisons between these drugs and mivacurium and cisatracurium are made. Rapacuronium 1.5 mg kg(-1) (ED95 1 mg kg(-1)), produces maximal neuromuscular block in 54 s. Time to recovery of the train-of-four ratio to 0.7 is achieved within 20 min after neostigmiine 0.05 mg kg(-1) given at 2 min. The plasma clearance of rapacuronium is 7-8 ml kg(-1) min(-1). Rapacuronium undergoes hepatic metabolism: no prolongation of effect has been reported after a single bolus or a short infusion in patients with hepatic or renal failure. Org 9488 is the 3-desacetyl metabolite of rapacuronium, which has neuromuscular blocking properties. Its much lower clearance (1.28 ml kg(-1) min(-1)) and plasma equilibration constant (0.105 min(-1)) may limit the prolonged use of rapacuronium. Rocuronium given at 2xED95 produces maximal neuromuscular block in 1 min. Spontaneous recovery of the train-of-four ratio to 0.7 takes over 40 min. Rocuronium has a plasma clearance of 4 ml kg(-1) min(-1). Its pharmacodynamics are altered in hepatic and renal disease. A number of anaphylactoid reactions to rocuronium have been reported recently. The bis-tetrahydroisoquinolinium chlorofumarate GW280430A has an ED95 of 0.19 mg kg(-1). Given at three times this dose, onset of neuromuscular block occurs within 100 s; the duration of block is 8-9 min. Following a 2 h infusion, the recovery index does not seem to be increased. Early studies suggest that this drug has no adverse cardiovascular or respiratory side-effects. The tropinyl diester derivative G-1-64 will produce 80-90% neuromuscular block in less than 2 min using 3xED80. Ninety per cent recovery of the first twitch of the train-of-four occurs after 5-7 min using one ED80. A recovery index of less than 2 min has been reported in rats. All the tropinyl diesters appear to produce vagal block. (+info)
The intent to exercise influences the cerebral O(2)/carbohydrate uptake ratio in humans.
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During and after maximal exercise there is a 15-30 % decrease in the metabolic uptake ratio (O(2)/[glucose + 1/2 lactate]) and a net lactate uptake by the human brain. This study evaluated if this cerebral metabolic uptake ratio is influenced by the intent to exercise, and whether a change could be explained by substrates other than glucose and lactate. The arterial-internal jugular venous differences (a-v difference) for O(2), glucose and lactate as well as for glutamate, glutamine, alanine, glycerol and free fatty acids were evaluated in 10 healthy human subjects in response to cycling. However, the a-v difference for the amino acids and glycerol did not change significantly, and there was only a minimal increase in the a-v difference for free fatty acids after maximal exercise. After maximal exercise the metabolic uptake ratio of the brain decreased from 6.1 +/- 0.5 (mean +/- S.E.M.) at rest to 3.7 +/- 0.2 in the first minutes of the recovery (P < 0.01). Submaximal exercise did not change the uptake ratio significantly. Yet, in a second experiment, when submaximal exercise required a maximal effort due to partial neuromuscular blockade, the ratio decreased and remained low (4.9 +/- 0.2) in the early recovery (n = 10; P < 0.05). The results indicate that glucose and lactate uptake by the brain are increased out of proportion to O(2) when the brain is activated by exhaustive exercise, and that such metabolic changes are influenced by the will to exercise. We speculate that the uptake ratio for the brain may serve as a metabolic indicator of 'central fatigue'. (+info)
Phonomyography of the corrugator supercilii muscle: signal characteristics, best recording site and comparison with acceleromyography.
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BACKGROUND: This study investigated the acoustic signal characteristics and best recording site of phonomyography at the corrugator supercilii muscle and compared phonomyography with acceleromyography. METHODS: In 12 patients (group I), after induction of anaesthesia and insertion of a laryngeal mask, a microphone (frequency range 2.5 Hz to 10 kHz) was placed on six different areas on the forehead and the peak-to-peak response after single-twitch stimulation of the facial nerve was measured. The microphone was placed where the response was largest and mivacurium 0.2 mg kg(-1) was administered. Fast Fourier transformation was applied to all signals to determine peak frequencies and the power-frequency relationship at different stages of neuromuscular block. In an additional 15 patients (group II), the same microphone and an acceleromyographic probe were placed above the middle portion of the left and right eyebrows respectively. Onset and offset of neuromuscular block were determined after mivacurium 0.2 mg kg(-1). RESULTS: In all seven women and all five men in group I, the best response was obtained just above the middle portion of the eyebrow. Peak frequency was 4.1 (SD 0.9) Hz without neuromuscular block and did not change significantly during onset and offset of neuromuscular block. Ninety per cent of the total signal power was below 40 Hz. In group II, mean onset time and maximum effect measured were 104 (20) s and 76 (10)% respectively using acceleromyography and 134 (30) s and 92 (4)% using phonomyography (P<0.04). Mean time to reach 25, 75 and 90% of control was 9.5 (2.8), 14 (5.1) and 15.1 (5.3) min respectively using acceleromyography and 6.9 (2.8), 12.5 (5.9) and 13.6 (4.9) min using phonomyography (P<0.04). Bland-Altman testing revealed significant bias (precision) for onset time, maximum effect and time to reach 25% of control (acceleromyography minus phonomyography) at -30 (38) s, -16 (11)% and 2.6 (2.8) min respectively. CONCLUSIONS: Phonomyography can be used to determine neuromuscular block at the corrugator supercilii muscle. In comparison with acceleromyography, phonomyography tends to measure a longer onset with more pronounced maximum effect and shorter recovery of neuromuscular block. (+info)
ProSeal laryngeal mask protects against aspiration of fluid in the pharynx.
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BACKGROUND: The ProSeal laryngeal mask airway (PLMA) is a new device designed to isolate the airway from the digestive tract. METHODS: We studied the ability of the PLMA to isolate the airway in 103 anaesthetized adults who were breathing spontaneously or given neuromuscular blocking agents, by filling the hypopharynx with methylene blue-dyed saline introduced down the drainage tube once the mask was in place. At the beginning and end of the procedure, a fibre-optic bronchoscope was passed down the airway tube to observe any dyed saline in the bowl of the mask. RESULTS: The PLMA was positioned correctly in all successful attempts (102 out of 103 attempts) and was able to isolate the glottis from fluid in the hypopharynx in all patients initially. Leakage of saline into the bowl of the mask occurred in two patients in whom displacement of the mask was caused by upper airway events during the procedure. In the remaining 100 patients, the glottis was isolated successfully for the duration of the procedure. CONCLUSIONS: The PLMA can be positioned reliably. It can isolate the airway from fluid in the hypopharynx. (+info)
Motion of the diaphragm in patients with chronic obstructive pulmonary disease while spontaneously breathing versus during positive pressure breathing after anesthesia and neuromuscular blockade.
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BACKGROUND: Diaphragmatic excursion during spontaneous ventilation (SV) in normal supine volunteers is greatest in the dependent regions (bottom). During positive pressure ventilation (PPV) after anesthesia and neuromuscular blockade and depending on tidal volume, the nondependent region (top) undergoes the greatest excursion, or the diaphragm moves uniformly. The purpose of this study was to compare diaphragmatic excursion (during SV and PPV) in patients with chronic obstructive pulmonary disease (COPD) with patients having normal pulmonary function. METHODS: Twelve COPD patients and 12 normal control subjects were compared. Cross-table diaphragmatic fluoroscopy was performed while patients breathed spontaneously. After anesthetic induction and pharmacologic paralysis and during PPV, diaphragmatic fluoroscopy was repeated. For analytic purposes, the diaphragm was divided into three segments: top, middle, and bottom. Percentage of excursion of each segment during SV and PPV in normal subjects was compared with the percentage of excursion of each segment in patients with COPD. RESULTS: There was no significant difference in the pattern of regional diaphragmatic excursion (as a percentage of total excursion)-top, middle, bottom-when comparing COPD patients with control subjects during SV and PPV. In the control subjects, regional diaphragmatic excursion was 16 +/- (5), 33 +/- (5), 51 +/- (4) during SV and 49 +/- (13), 32 +/- (6), 19 +/- (9) during PPV. In COPD patients, regional diaphragmatic excursion was 18 +/- (7), 34 +/- (5), 49 +/- (7) during SV and 47 +/- (10), 32 +/- (6), 21 +/- (9) during PPV. CONCLUSION: Regional diaphragmatic excursion in patients with COPD during SV and PPV is similar to that in persons with normal pulmonary function. (+info)
Intrathecal ropivacaine in rabbits: pharmacodynamic and neurotoxicologic study.
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BACKGROUND: Ropivacaine is available for spinal or intrathecal use in humans, although data on neurotoxicity after spinal injection are not yet available. The authors experimentally determined the relationship between doses of intrathecal ropivacaine and spinal effects and local neurotoxic effects. METHODS: Eighty rabbits equipped with an intrathecal lumbar catheter were studied. Sixty were randomly assigned to receive 0.2 ml of intrathecal solutions as a sole injection of: 0.2%, 0.75%, 1.0%, and 2.0% ropivacaine (doses from 0.4-4.0 mg; groups R0.2 to R2.0), 5.0% lidocaine (10 mg; group L), or 0.9% NaCl as control (group C). Twenty other rabbits received either repeated injections of 0.2 ml of 0.2% ropivacaine every 2 days during 2 weeks (total dose of 2.8 mg; group RINT); or a continuous intrathecal infusion of 0.2% ropivacaine at the rate of 1.8 ml/h over 45 min (2.7 mg; group RCONT). Injection rate was 30 s in all groups except Rcont. Time to onset, duration and extent of motor block, and variations of mean arterial blood pressure were recorded in all groups. Somatosensory evoked potentials were also recorded in group RCONT and RINT. Seven days after the last intrathecal injection spinal cord and nerves were sampled for histopathologic study. RESULTS: In groups R0.2 and RINT, the lowest dose of ropivacaine induced a clinically visible spinal block in only 50% of rabbits, but SEPs recorded in group RINT were decreased by 70% in the lumbar dermatome. Complete motor block was observed with doses greater than 1.5 mg of ropivacaine (group RCONT and R0.75 to R2.0). Onset time was shorter and duration of block increased as doses of ropivacaine increased. Significant hypotension was observed only with 4.0 mg of ropivacaine (concentration of 2.0%). Complete paralysis and hypotension were observed with 5.0% lidocaine. No neurologic clinical lesion was observed in rabbits receiving saline or ropivacaine within the 7 days after the last intrathecal injection, and histopathologic study revealed no sign of neurotoxicity in these groups. In contrast, intrathecal lidocaine induced clinical and histopathologic changes. CONCLUSION: Ropivacaine induced dose-dependent spinal anesthesia, and did not induce any neurotoxicologic lesion in this experimental animal model. (+info)