Oxygenation and plasma endothelin-1 concentrations in healthy horses recovering from isoflurane anaesthesia administered with or without pulse-delivered inhaled nitric oxide.

The research article investigates the effect of inhaled nitric oxide (iNO) in horses being recovered from isoflurane anaesthesia. The study found that horses given iNO maintained better oxygen levels in their blood and improved ventilation-perfusion (V/Q), alongside reduced concentrations of plasma endothelin-1 (ET-1).

Methods and Experimental Procedure

• The study was designed as a prospective experimental trial, involving healthy adult Standardbred horses.
• Twelve horses were divided into two groups for the experiment. The control group (C group) comprised six horses that were anaesthetised with isoflurane without iNO delivery. In contrast, the second group (NO group) involved six horses that received pulse-delivered iNO while being anaesthetised with isoflurane.
• After 2.5 hours of anaesthesia, isoflurane and iNO were abruptly discontinued, inhaled oxygen was decreased from 100% to approximately 30%, and the horses were moved to a recovery stall.
• Data pertaining to arterial and mixed venous blood gas values, shunt fraction (Qs/Qt), plasma ET-1 concentration, pulse rate, and respiratory rate were measured or calculated at intervals during a 30-minute period after discontinuation of anaesthesia.
• A repeated measures analysis of variance (ANOVA) and a post-hoc Bonferroni test were utilized for data analysis, setting statistical significance at p < 0.05.

Key Findings of the Study

• During recovery, the NO group maintained better arterial oxygenation, better V/Q matching, and higher mixed venous oxygenation for 25 minutes after discontinuation of anaesthesia than the C group.
• Arterial oxygenation in both groups remained relatively stable; however, venous oxygenation declined with time in the NO group, despite still being higher than venous oxygen in the C group.
• In most cases, the ET-1 concentrations were observed to be higher in the C group than in the NO group.
• Changes in parameters other than the ones mentioned were either minor or did not occur.

Conclusions

• The study concluded that the delivery of iNO to healthy horses during anaesthesia leads to improved arterial and venous oxygenation and V/Q matching, as indicated by lower Qs/Qt levels.
• Furthermore, it resulted in lower ET-1 concentrations over a 30-minute anaesthetic recovery period.