Cardiopulmonary effects of reverse Trendelenburg position at 5° and 10° in sevoflurane-anesthetized steers

Abstract

RTP 5° and 10° did not improve ventilatory and oxygenation variables in sevoflurane-anesthetized steers when compared with no tilt, however the cardiovascular variables were adversely affected in RTP10.

Effect of 15° Reverse Trendelenburg Position on Arterial Oxygen Tension during Isoflurane Anesthesia in Horses

“…In the current study, the 15° RTP was associated with an apparent greater negative cardiovascular effect compared to HP. With the caveat that the study was not designed to test the cardiovascular effects of 15° RTP and these data were not compared statistically, our findings appear to be in contrast with reports using smaller RTP angles in horses [13,14] and steers [30] as well greater angles in humans [27,28,40]. While positive pressure ventilation and the constant-dose isoflurane likely had some contribution to the hypotension observed in the current study, the difference between RTP and HP can be attributed to the 15° RTP given the study design with each horse receiving both treatments and thus serving as their own control.…”

“…The 15° RTP better preserved the V/Q relationship compared to HP by decreasing venous admixture, as indicated by a significantly lower F-shunt. These findings are in agreement with reports in mechanically ventilated morbidly obese humans at 30° RTP [27][28][29] but are in contrast to those obtained in mechanically ventilated horses at 5° RTP [13] or 7° RTP [14] and in spontaneously breathing steers at 5° and 10° RTP [30]. It is important to note that our results were obtained in a homogeneous group of round-bellied horses, a group of horses known to have lower PaO2, and a higher alveolar-to-arterial oxygen tension difference than flat-bellied horses in both dorsal and lateral recumbency [11].…”

“…A 30° RTP was subsequently shown to be efficacious in improving pulmonary gas exchange and total respiratory system compliance [27][28][29]. In isoflurane-anesthetized horses [13,14] and sevoflurane-anesthetized steers [30] positioned in dorsal recumbency, RTP at angles between 5° and 10° did not improve arterial oxygenation compared to the horizontal position (HP). Another study comparing 7° RTP with a 7° head-down (i.e., Trendelenburg) position for 90 min in dorsally recumbent isoflurane-anesthetized horses breathing 0.85 FiO2 found that the RTP did not improve arterial oxygenation compared to baseline.…”

Fatal cardiac arrest in a calf with uroperitoneum

“…In the present case, despite the hypoxaemia, FiO 2 was maintained around 0.8 and an increase to 1 was not considered due to the fact that FiO 2 has very little effect on PaO 2 in the presence of significant shunt, while high FiO 2 values can exacerbate alveolar collapse (absorption atelectasis) 43. Reverse Trendelenburg position in human patients has been suggested to reduce the IAP transmitted to the thorax and to improve ventilation in cases of abdominal distension,44 but it may be not as effective in cattle45 and might reduce venous return. Mild improvement after decompression was recorded in the present case, with a PaO 2 of 86 mmHg and an SaO 2 of 92 per cent.…”

Anaesthesia management of a pug (in late‐stage pregnancy) with lung lobe torsion

“…However, respiratory acidosis and marked venous admixture were still present with little improvement in PaO 2 . This type of positioning may increase systemic vascular resistance index and decrease cardiac index,9 and any potential benefit should always be balanced against potential risks.…”