Evaluation of cardiopulmonary effects of total intravenous anesthesia using a drug combination of medetomidine,lidocaine,butorphanol and propofol (MLBP-TIVA) with or without controlled ventilation and effect of positioning in mechanically ventilated horses

The purpose of this study was to evaluate cardiopulmonary effects of MLBP-TIVA with or without controlled ventilation in horses and to determine effects of positioning on cardiovascular function in mechanically ventilated horses.Five healthy adult horses were anesthetized with MLBP-TIVA for 2-hours on 3-occasions at 4-week interval with (CMV-group) or without controlled mechanical ventilation (SB-group) and in lateral (LR-group) or dorsal (DRgroup) recumbency.Anesthesia was induced with lidocaine (1 mg/kg: IV) and propofol (3 mg/kg: IV) following premedications with medetomidine (0.005 mg/kg: IV) and butorphanol (0.02 mg/kg: IV),and then maintained by propofol infusion combined with constant rate infusions of medetomidine (0.0035 mg/kg/h),lidocaine (3 mg/kg/h)and butorphanol (0.024 mg/kg/h).Data were compared between groups using repeated-measures ANOVA.The level of significance was set at P 【 0.05.Cardiovascular parameters were maintained within acceptable ranges in SB-group.However,severe hypercapnia with insufficient oxygenation was observed (PaCO2: 83 ~103 mmHg,arterial O2pressure [PaO2]: 155 ~171 mmHg).In CMV-group,significant decreases in heart rate (29 ~ 31 beats/min,P = 0.020),cardiac output (17 ~ 21 L/min,P= 0.005) and PaCO2 (42 ~ 50 mmHg,P = 0.001) and a significant increase in PaO2 (395 ~ 419 mmHg,P =0.005) were observed compared to SB-group.Mean pulmonary arterial pressure and mean atrial blood pressure were significantly decreased in DR-group compared to LR-group (18 ~ 20 mmHg vs 27 ~ 31 mmHg,P = 0.001 and 8 ~ 9 mmHg vs 15 ~ 17 mmHg,P = 0.003,respectively).Arterial O2pressure was significantly lower in DR-group than in LR-group (171 ~301 mmHg vs 385 ~416 mmHg,P =0.043).Cardiovascular functions were maintained within acceptable range during MLBP-TIVA in horses.Controlled ventilation is useful for improving hypercapnia and oxygenation.Also,MLBP-TIVA provides a preservation of cardiovascular function leading to compensation for decreased preload in horses positioned in dorsal recumbency.

Sparing effect of robenacoxib on the minimum alveolar concentration for blunting adrenergic response( MAC-BAR) of sevoflurane in dogs.

Robenacoxib is a newer non-steroidal anti-inflammatory drug (NSAID) and effective for the management of perioperative pain and inflammation. A preoperative administration of robenacoxib is approved in many countries. The preoperative administration of NSAIDs (carprofen or meloxicam) reduces the minimum alveolar concentration (MAC) of sevoflurane during noxious stimulation in dogs (Yamashita et al. 2008). The purpose of this study was to evaluate the effect of robenacoxib on the MAC for blunting adrenergic response (MAC-BAR) of sevoflurane in dogs.Six adult healthy beagle dogs were anesthetized to determine the MAC-BAR of sevoflurane on 2-ocassions at least 1-week intervals. In each occasion,the dogs received a subcutaneous injection (SC) of saline (0. 1 ml/kg) or robenacoxib (2 mg/kg) before the MAC-BAR determination. MAC-BAR determination started at 60 minutes after the administration of saline or robenacoxib. MAC-BAR was determined in duplicate for each dog using electrical stimulus applied to the gingival (50 V,50 Hz,10 ms). During the MAC determination,all dogs were mechanically ventilated to maintain the end-tidal CO2within 35 to 40 mmHg and kept warm to maintain esophageal temperature within 37. 5 to 38. 5 ℃. Data were compared between groups using a paired t-test. The level of significance was set at P < 0. 05.The baseline MAC-BAR for sevoflurane was 3. 44 ± 0. 53%. Subcutaneous robenacoxib significantly decreased the sevoflurane MAC-BAR by 17% (2. 84 ± 0. 77%,P = 0. 039).Robenacoxib decreased the sevoflurane MAC-BAR when it was administered at the approved preoperative dose (2mg/kg: SC) to dogs. It is expected that the use of robenscoxib as premedication may provide a clinically relevant anesthetic sparing effect similar to carprofen and meloxicam in dogs (Yamashita et al. 2008).

Effects of controlled ventilation and positioning on cardiopulmonary function in horses anesthetized with total intravenous anesthesia using a drug combination of medetomidine,lidocaine,butorphanol and propofol (MLBP-TIVA)

The purpose of this study was to evaluate effects of controlled ventilation and positioning on cardiopulmonary function in horses anesthetized with total intravenous anesthesia using a drug combination of medetomidine,lidocaine,butorphanol and propofol (MLBP-TIVA).Five healthy adult horses were anesthetized with MLBP-TIVA for 2-hours on 3-occasions at 4-week interval. In each occasion,horses were anesthetized in lateral recumbency with (CV-LR-group) or without controlled ventilation (SB-LRgroup) or in dorsal recumbency with controlled ventilation (CV-DR-group). Anesthesia was induced with lidocaine (1mg/kg: IV) and propofol (3 mg/kg: IV) following premedications with medetomidine (0. 005 mg/kg: IV) and butorphanol (0. 02 mg/kg: IV),and then maintained by constant rate infusions of propofol (6 mg/kg/hr),medetomidine (0. 0035 mg/kg/h),lidocaine (3 mg/kg/h) and butorphanol (0. 024 mg/kg/h). All horses breathed 100% oxygen during anesthesia. In the CV-groups,horses were mechanically ventilated to maintain arterial CO2pressure (PaCO2)within 40 ~ 50 mmHg. Cardiopulmonary parameters were compared between groups using repeated-measures ANOVA.The level of significance was set at P 【 0. 05.In the SB-LR group,cardiovascular parameters were maintained within acceptable ranges (heart rate: 37 ~ 39beats/min,mean arterial blood pressure: 109 ~ 115 mmHg,mean pulmonary arterial pressure [MPAP]: 28 ~ 29 mmHg,mean right atrial pressure [MRAP]: 19 ~ 21 mmHg,cardiac output: 27 ~ 30 L/min) but severe hypercapnia with insufficient oxygenation (PaCO283 ~ 103 mmHg,arterial O2pressure [PaO2]155 ~171 mmHg) was observed. Cardiopulmonary parameters were maintained with acceptable ranges in the both CV groups. In the CV-LR group,significant decreases in heart rate (29 ~ 31 beats/min,P = 0. 020),cardiac output (17 ~ 21 L/min,P = 0. 005) and PaCO2 (42 ~50 mmHg,P =0. 001) and a significant increase in PaO2 (395 ~419 mmHg,P =0. 005) were observed compared to the SB-group. In the CV-DR group,MPAP (18 ~ 20 mmHg,P = 0. 001),MRAP (15 ~ 17 mmHg,P =0. 003) and PaO2 (171 ~301 mmHg,P =0. 043) were significantly decreased compared to the CV-LR-group.Cardiovascular functions were well maintained in horses during MLBP-TIVA. Controlled ventilation was useful for improving hypercapnia and oxygenation. It is thought that MLBP-TIVA preserves cardiovascular function and provides compensation for decreased preload in horses positioned in dorsal recumbency.

Sparing effect of an antiemetic dose of maropitant on the minimum alveolar concentration for blunting adrenergic response (MAC-BAR) of sevoflurane in dogs.

Maropitant a neurokinin-1 (NK-1) receptor antagonist used as an antiemetic drug in dogs by blockade of substance P/NK-1 receptor binding in the vomiting center and chemoreceptor trigger zone in the central nervous system. In addition,substance P and NK-1 receptors have been isolated in nociceptive pathways. Therefore,it is expected that maropitant provides analgesic effect and its sparing effect of minimum alveolar concentration (MAC) has been reported in dogs. The purpose of this study was to evaluate the sparing effect of an approved antiemetic dose of maropitant on the MAC for blunting adrenergic response (MAC-BAR) of sevoflurane in dogs.Six adult healthy beagle dogs were anesthetized to determine the MAC-BAR of sevoflurane on 2-ocassions at least 1-week intervals. In each occasion,the dogs received a subcutaneous injection (SC) of saline (0. 1 ml/kg) or maropitant (1 mg/kg) before the MAC-BAR determination. MAC-BAR determination started at 60 min after the administration of saline or maropitant. MAC-BAR was determined in duplicate for each dog using electrical stimulus applied to the gingival (50 V,50 Hz,10 ms). During the MAC determination,all dogs were mechanically ventilated to maintain the endtidal CO2within 35 to 40 mmHg and kept warm to maintain esophageal temperature within 37. 5 to 38. 5 ℃. Data were compared between groups using a paired t-test. The level of significance was set at P < 0. 05.The baseline MAC-BAR for sevoflurane was 3. 44 ± 0. 53%. Subcutaneous maropitant significantly decreased the sevoflurane MAC-BAR by 17% (2. 88 ± 0. 74%,P = 0. 037).Maropitant decreased the sevoflurane MAC-BAR when administered at the approved antiemetic dose (1 mg/kg:SC) to dogs. It is expected that a preoperative administration of maropitant may produce anesthetic sparing effect in addition to antiemetic effect in dogs.