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...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.展开更多
文摘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.
