955 resultados para constant rate infusion
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PURPOSE:To assess the hemodynamic changes and bispectral index (BIS) following administration of a continuous rate infusion (CRI) of butorphanol in isoflurane-anesthetized calves.METHODS: Eight calves weighing 110 ± 12 kg were included in the study. Anesthesia was induced with 5% isoflurane in O2 delivered via face mask and maintained with end-tidal concentration of 1.4%. IPPV was set to a peak inspiratory airway pressure of 15 cmH2O and respiratory rate of six breaths minute-1. Forty minutes after the start of anesthetic maintenance, 0.1 mg kg-1butorphanol was administered intravenously, followed by a CRI of 20 µg kg-1 minute-1. Hemodynamic variables and BIS were recorded before butorphanol administration (T0), and at 10, 20, 40 and 80 minutes following the CRI. Anesthesia was discontinued after the last recording and the calves were allowed to recover. The time to sternal recumbency (SRE) and standing (ST) were evaluated.RESULTS: There were no significant differences between the moments in all hemodynamic variables and BIS. The time to SRE and ST was 9 ± 5 and 14 ± 7 minutes, respectively.CONCLUSION: The continuous rate infusion did not produce clinically relevant changes in hemodynamic or bispectral index values compared to baseline in mechanically ventilated and unstimulated calves anesthetized at 1.4% isoflurane.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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OBJECTIVE: To evaluate the isoflurane-sparing effects of lidocaine administered by constant rate infusion (CRI) during umbilical surgery in calves. STUDY DESIGN: Randomized 'blinded' prospective clinical study. ANIMALS: Thirty calves (mean 4.7 +/- SD 2.5 weeks old) undergoing umbilical surgery. METHODS: After premedication with xylazine (0.1 mg kg(-1) , IM), anaesthesia was induced with ketamine (4 mg kg(-1) , IV) and maintained with isoflurane in O(2) administered through a circle breathing system. The calves were assigned randomly to receive a bolus of 2 mg kg(-1) lidocaine IV after induction of anaesthesia, followed by CRI of 50 mug kg(-1) minute(-1) (group L, n=15) or a bolus and CRI of 0.9% sodium chloride (NaCl, group S, n=15). End-tidal isoflurane was adjusted to achieve adequate depth of anaesthesia. Heart rate, direct arterial blood pressure and body temperature were measured intraoperatively. Groups were compared by t- tests, anova or Mann-Whitney rank sum test as appropriate. RESULTS: The end-tidal concentration of isoflurane (median, IQR) was significantly lower in group L [1.0% (0.94-1.1)] compared to group S [1.2% (1.1-1.5)], indicating a 16.7% reduction in anaesthetic requirement during lidocaine CRI. Cardiopulmonary parameters and recovery times did not differ significantly between groups. CONCLUSION AND CLINICAL RELEVANCE: Lidocaine CRI may be used as a supplement to inhalation anaesthesia during umbilical surgery in calves in countries where such a protocol would be within the legal requirements for veterinary use in food animals. This study did not show any measurable benefit to the calves other than a reduction in isoflurane requirement.
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OBJECTIVE: To investigate the effect of plasma concentrations obtained by a low dose constant rate infusion (CRI) of racemic ketamine or S-ketamine on the nociceptive withdrawal reflex (NWR) in standing ponies. STUDY DESIGN: Prospective, blinded, cross-over study. ANIMALS: Six healthy 5-year-old Shetland ponies. METHODS: Ponies received either 0.6 mg kg(-1) racemic ketamine (group RS) or 0.3 mg kg(-1) S-ketamine (group S) intravenously (IV), followed by a CRI of 20 microg kg(-1)minute(-1) racemic ketamine (group RS) or 10 microg kg(-1)minute(-1) S-ketamine (group S) for 59 minutes. The NWR was evoked by transcutaneous electrical stimulation of a peripheral nerve before drug administration, 15 and 45 minutes after the start of the bolus injection and 15 minutes after the end of the CRI. Electromyographic responses were recorded and analysed. Arterial blood was collected before stimulation and plasma concentrations of ketamine and norketamine were measured enantioselectively using capillary electrophoresis. Ponies were video recorded and monitored to assess drug effects on behaviour, heart rate (HR), mean arterial blood pressure (MAP) and respiratory rate. RESULTS: The NWR was significantly depressed in group RS at plasma concentrations between 20 and 25 ng mL(-1) of each enantiomer. In group S, no significant NWR depression could be observed; plasma concentrations of S-ketamine (9-15 ng mL(-1)) were lower, compared to S-ketamine concentrations in group RS, although this difference was not statistically significant. Minor changes in behaviour, HR and MAP only occurred within the first 5-10 minutes after bolus drug administration in both groups. CONCLUSION: Antinociceptive activity in standing ponies, demonstrated as a depression of the NWR, could only be detected after treatment with racemic ketamine. S-ketamine may have lacked this effect as a result of lower plasma concentrations, a more rapid metabolism or a lower potency of S-ketamine in Equidae so further investigation is necessary.
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Objective To examine the influence of a low dose dexmedetomidine infusion on the nociceptive withdrawal reflex and temporal summation in dogs during isoflurane anaesthesia. Study design Prospective experimental blinded cross-over study. Animals Eight healthy mixed breed dogs, body weight Mean +/- SD 26.5 +/- 8.4 kg and age 25 +/- 16 months. Methods Anaesthesia was induced with propofol and maintained with isoflurane (Fe'ISO 1.3%) delivered in oxygen and air. After stabilization, baseline recordings (time 0) were obtained, then a dexmedetomidine bolus (1 mug kg(-1) IV) followed by a continuous rate infusion (1 mug kg(-1) hour(-1) ) or saline placebo were administered. At times 10, 30 and 60 minutes after the initial bolus, electrical stimulations of increasing intensity were applied over the lateral plantar digital nerve, and administered both as single and as repeated stimuli. The resulting reflex responses were recorded using electromyography. Data were analysed using a multivariable linear regression model and a Kruskal Wallis test for single stimulation data, and repeated measures anova and paired t-test for repeated stimulation data. Results The AUC for the stimulus-response curves after single stimulation were similar for both treatments at time 0. At times 10, 30 and 60 the AUCs for the stimulus-response curves were significantly lower with dexmedetomidine treatment than with placebo. Temporal summation was evident in both treatments at times 0, 10, 30 and 60 starting from a stimulation intensity of 10 mA. The magnitude of temporal summation was smaller in dexmedetomidine than in placebo treated dogs at time 10, 30 and 60, but not at time 0. Conclusions During isoflurane anaesthesia, low dose dexmedetomidine suppresses the nociceptive reflex responses after single and repeated electrical stimulation. Clinical relevance This experimental study confirms previous reports on its peri-operative efficacy under clinical conditions, and further indicates that dexmedetomidine might reduce the risk of post-operative chronic pain development.
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Objective-To evaluate the cardiorespiratory and intestinal effects of the muscarinic type-2 (M-2) antagonist, methoctramine, in anesthetized horses.Animals-6 horses.Procedure-Horses were allocated to 2 treatments in a randomized complete block design. Anesthesia was maintained with halothane (1% end-tidal concentration) combined with a constant-rate infusion of xylazine hydrochloride (1 mg/kg/h, IV) and mechanical ventilation. Hemodynamic variables were monitored after induction of anesthesia and for 120 minutes after administration of methoctramine or saline (0.9% NaCl) solution (control treatment). Methoctramine was given at 10-minute intervals (10 mug/kg, IV) until heart rate (HR) increased at least 30% above baseline values or until a maximum cumulative dose of 30 mug/kg had been administered. Recovery characteristics, intestinal auscultation scores, and intestinal transit determined by use of chromium oxide were assessed during the postanesthetic period.Results-Methoctramine was given at a total cumulative dose of 30 mug/kg to 4 horses, whereas 2 horses received 10 mug/kg. Administration of methoctramine resulted in increases in HR, cardiac output, arterial blood pressure, and tissue oxygen delivery. Intestinal auscultation scores and intestinal transit time (interval to first and last detection of chromium oxide in the feces) did not differ between treatment groups.Conclusions and Clinical Relevance-Methoctramine improved hemodynamic function in horses anesthetized by use of halothane and xylazine without causing a clinically detectable delay in the return to normal intestinal motility during the postanesthetic period. Because of their selective positive chronotropic effects, M-2 antagonists may represent a safe alternative for treatment of horses with intraoperative bracycardia.
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Objective-To evaluate cardiopulmonary effects of glycopyrrolate in horses anesthetized with halothane and xylazine.Animals-6 horses.Procedure-Horses were allocated to 2 treatment groups in a randomized complete block design. Anesthesia was maintained in mechanically ventilated horses by administration of halothane (1% end-tidal concentration) combined with a constant-rate infusion of xylazine hydrochloride (1 mg/kg/h, IV). Hemodynamic variables were monitored after induction of anesthesia and for 120 minutes after administration of glycopyrrolate or saline (0.9% NaCl) solution. Glycopyrrolate (2.5 mug/kg, IV) was administered at 10-minute intervals until heart rate (HR) increased at least 30% above baseline or a maximum cumulative dose of 75 mug/kg had been injected. Recovery characteristics and intestinal auscultation scores were evaluated for 24 hours after the end of anesthesia.Results-Cumulative dose of glycopyrrolate administered to 5 horses was 5 mug/kg, whereas 1 horse received 75 mug/kg. The positive chronotropic effects of glycopyrrolate were accompanied by an increase in cardiac output, arterial blood pressure, and tissue oxygen delivery. Whereas HR increased by 53% above baseline values at 20 minutes after the last glycopyrrolate injection, cardiac output and mean arterial pressure increased by 38% and 31%, respectively. Glycopyrrolate administration was associated with impaction of the large colon in I horse and low intestinal auscultation scores lasting 24 hours in 3 horses.Conclusions and Clinical Relevance-The positive chronotropic effects of glycopyrrolate resulted in improvement of hemodynamic function in horses anesthetized with halothane and xylazine. However, prolonged intestinal stasis and colic may limit its use during anesthesia.
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Opioids may exert a protective effect against ventricular arrhythmias via a vagally mediated mechanism. This study evaluated the effects of the opioid remifentanil on arrhythmogenicity of epinephrine during halothane anesthesia. Eight dogs were assigned to 2 treatments in a randomized crossover design, with 1-week intervals between treatments. Anesthesia was maintained with 1.3% end-tidal halothane in oxygen and mechanical ventilation to maintain eucapnia. A constant rate infusion of remifentanil (0.72 mu g/kg/min) was administered throughout the study in the experimental treatment, while control animals received physiologic saline as placebo. The arrhythmogenic dose of epinephrine (ADE), defined as 4 premature ventricular complexes (PVCs) within 15 s, was determined by administering progressively increasing infusion rates of epinephrine (2.5, 5.0, and 10 mu g/kg/min), allowing 20 min intervals between each infusion rate. In both treatments, epinephrine infusions induced bradyarrhythmias and atrioventricular conduction disturbances, which were followed by escape beats and PVCs. In the remifentanil treatment, mean s ADE values (11.3 +/- 4.9 mu g/kg) did not differ from values observed in control animals (9.9 +/- 6.1 mu g/kg). on the basis of the ADE model for assessing the arrhythmogenity of drugs during halothane anesthesia, the present study did not demonstrate a protective effect of remifentanil (0.72 mu g/kg/min) against ventricular arrhythmias in dogs.
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Sixteen cats were used to compare the cardiovascular and anesthetic effects of remifentanil (REMT) or alfentanil (ALF) in propofol-anesthetized cats undergoing ovariohysterectomy. After premedication with acepromazine, anesthesia was induced and maintained with a constant rate infusion of propofol (0.3 mg/kg/min). REMT or ALF infusions were administered simultaneously with propofol. Heart rate (HR), systolic arterial pressure (SAP), pulse oximetry (SpO(2)), rectal temperature (RT), and response to surgical stimulation were recorded at predefined time points during anesthesia. Data [mean +/- standard deviation (SD)] were analyzed by analysis of variance (ANOVA) for repeated measures followed by a Dunnett's test and Student t-test (P < 0.05). SAP was significantly lower in ALF group than in REMI group. Extubation time was significantly shorter in REMI than in ALF group. Overall infusion rate of REMI and ALF was 0.24 +/- 0.05 mu g/kg/min and 0.97 +/- 0.22 mu g/kg/min, respectively. The combination of propofol and REM! or ALF provided satisfactory anesthesia in cats undergoing ovariohysterectomy. (C) 2011 ISFM and AAFP. Published by Elsevier Ltd. All rights reserved.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)