Effects of intermittent positive pressure ventilation (IPPV) on cardiopulmonary function were evaluated in horses anesthetized with total intravenous anesthesia using constant rate infusions of medetomidine (3.5
µg/kg/hr), lidocaine (3 mg/kg/hr), butorphanol (24
µg/kg/hr) and propofol (0.1 mg/kg/min) (MLBP-TIVA). Five horses were anesthetized twice using MLBP-TIVA with or without IPPV at 4-week interval (crossover study). In each occasion, the horses breathed 100% oxygen with spontaneous ventilation (SB-group, n=5) or with IPPV (CV-group, n=5), and changes in cardiopulmonary parameters were observed for 120 min. In the SB-group, cardiovascular parameters were maintained within acceptable ranges (heart rate: 33–35 beats/min, cardiac output: 27–30
l/min, mean arterial blood pressure [MABP]: 114–123 mmHg, mean pulmonary arterial pressure [MPAP]: 28–29 mmHg and mean right atrial pressure [MRAP]: 19–21 mmHg), but severe hypercapnea and insufficient oxygenation were observed (arterial CO
2 pressure [PaCO
2]: 84–103 mmHg and arterial O
2 pressure [PaO
2]: 155–172 mmHg). In the CV-group, normocapnea (PaCO
2: 42–50 mmHg) and good oxygenation (PaO
2: 395–419 mmHg) were achieved by the IPPV without apparent cardiovascular depression (heart rate: 29–31 beats/min, cardiac output: 17–21
l /min, MABP: 111–123 mmHg, MPAP: 27–30 mmHg and MRAP: 15–16 mmHg). MLBP-TIVA preserved cardiovascular function even in horses artificially ventilated.
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