Histopathological changes and mRNA expression in lungs of horses after inhalation anaesthesia with different ventilation strategies.

This research study investigated the effects of different ventilation strategies during inhalation anesthesia on lung health in horses. The study focused on changes in the lungs and gene expression patterns, notably finding that different ventilation methods can cause various lung injuries and changes in inflammatory and enzyme markers.

Study Design and Methodology

• The research involved 23 horses segmented into four categories – those ventilated with Open Lung Concept (OLC), those ventilated with intermittent positive pressure ventilation (IPPV), non-ventilated horses, and a control group that wasn’t anaesthetized.
• Following sedation with xylazine and induction with diazepam and ketamine, iso-flurane anaesthesia was used for 5.5 hours on the horses.
• Following this, the horses were euthanized and lung tissue samples were collected from both dependent and non-dependent lung areas.

Data Analysis

• Histopathological examinations of the lung tissues were undertaken to observe any cellular changes.
• mRNA relative quantification was also carried out using polymerase chain reaction (PCR) for five genes – IL-1β, IL-6, iNOS, MMP1 and MMP9. These genes are involved in inflammation and cellular response to injury.
• Findings revealed that horses from the OLC group had significantly less alveolar congestion and atelectasis (lung tissue collapse) but more alveolar overdistension (overinflation of the alveoli – the tiny air sacs in the lungs where oxygen and carbon dioxide are exchanged) compared to the non-ventilated and IPPV groups.
• There was an increase in IL-1β/6 and MMP1/9 gene expressions in both the OLC and IPPV groups, as compared to the non-ventilated and control groups.

Conclusion

• The study concluded that horses ventilating spontaneously or under IPPV ventilation displayed higher degrees of atelectasis (lung tissue collapse), while those under OLC ventilation exhibited higher degrees of overdistension.
• The researchers also inferred that increased levels of IL and MMP could potentially serve as early indicators of Ventilator-Induced Lung Injury (VILI) in ventilated horses.

This research highlights the importance of considering the ventilation strategy employed during inhalation anesthesia in horses, as it can impact lung health significantly.