Controlled mechanical ventilation with constant positive end-expiratory pressure and alveolar recruitment manoeuvres during anaesthesia in laterally or dorsally recumbent horses.
OBJECTIVE
To compare the effects of controlled mechanical ventilation (CMV) and constant positive end-expiratory pressure (PEEP) and interposed recruitment manoeuvres (RMs) with those of CMV without PEEP on gas exchange during general anaesthesia and the early recovery period.


STUDY DESIGN
Prospective, randomized clinical trial.


ANIMALS
A total of 48 Warmblood horses undergoing elective surgery in lateral (Lat) (n = 24) or dorsal (Dors) (n = 24) recumbency.


METHODS
Premedication (romifidine), induction (diazepam and ketamine) and maintenance (isoflurane in oxygen) were identical in all horses. Groups Lat- CMV and Dors-CMV (each n = 12) were ventilated using CMV. Groups Lat-RM and Dors-RM (each n = 12) were ventilated using CMV with constant PEEP (10 cmH2O) and intermittent RMs (three consecutive breaths with peak inspiratory pressure of 60 cmH2O, 80 cmH2O and 60 cmH2O, respectively). RMs were applied as required to maintain PaO2 at > 400 mmHg (> 53.3 kPa). Dobutamine was given to maintain mean arterial blood pressure at > 60 mmHg. Physiological parameters were recorded every 10 minutes. Arterial blood gases were measured intra- and postoperatively. Statistical analyses were conducted using analyses of variance (anova),t tests and the Mann-Whitney U-test.


RESULTS
Horses in Dors-RM had higher PaO2 values [478 ± 35 mmHg (63.7 ± 4.6 kPa)] than horses in Dors-CMV [324 ± 45 mmHg (43.2 ± 6 kPa)] during anaesthesia and the early recovery period. There were no differences between horses in groups Lat-CMV and Lat-RM. Other measured parameters did not differ between groups.


CONCLUSIONS AND CLINICAL RELEVANCE
Ventilation with CMV, constant PEEP and interposed RM provided improved arterial oxygenation in horses in dorsal recumbency that lasted into the early recovery period, but had no benefit in horses in lateral recumbency. This mode of ventilation may provide a clinically practicable method of improving oxygenation in anaesthetized horses, especially in dorsal recumbency.
['Hopster|Klaus|K|', 'Rohn|Karl|K|', 'Ohnesorge|Bernhard|B|', 'Kästner|Sabine B R|SBR|']
D000768:Anesthesia, General D000818:Animals D001784:Blood Gas Analysis D045422:Continuous Positive Airway Pressure D003975:Diazepam D017558:Elective Surgical Procedures D006736:Horses D007093:Imidazoles D007530:Isoflurane D007649:Ketamine D010100:Oxygen D010313:Partial Pressure D056888:Patient Positioning D011175:Positive-Pressure Respiration D018467:Positive-Pressure Respiration, Intrinsic D011229:Preanesthetic Medication D011446:Prospective Studies D011650:Pulmonary Alveoli D012121:Respiration, Artificial
controlled mechanical ventilation ventilation positive end-expiratory pressure recruitment manoeuvres oxygenation equine anaesthesia