Effects of 7.2% hypertonic saline solution on cardiovascular parameters and endogenous arginine vasopressin secretion in euvolemic isoflurane-anesthetized horses.

The research article investigates the impact of 7.2% hypertonic saline solution on the cardiovascular parameters and plasma arginine vasopressin (AVP) concentration in healthy horses anesthetized with isoflurane. The study found that a bolus of hypertonic saline solution enhances blood pressure, likely due to an increase in systemic vascular resistance (SVR) and volume recruitment.

Research Methodology

• The researchers conducted a prospective, randomized, crossover study which involved eight healthy horses.
• Each horse was anesthetized with isoflurane twice, with a 14-day washout period in between anesthetic episodes.
• While the horses were being anesthetized, they were given a 4 mL/kg bolus of either 7.2% hypertonic saline solution (HS) or 0.9% isotonic saline solution (IS).
• Every 5 minutes, parameters such as heart rate, systolic, mean, and diastolic arterial blood pressures, and central venous and pulmonary artery pressures were measured. Cardiac output was gauged by thermodilution every quarter-hour.
• Systemic vascular resistance (SVR) was calculated and blood samples were taken before and during anesthesia to determine plasma AVP concentrations using a validated ELISA.
• The researchers then analyzed the collected data via repeated measures analysis of variance (ANOVA) and Pearson correlations.

Research Findings

• The application of HS induced an increase in systolic and mean arterial blood pressures, which persisted for half an hour.
• The SVR rose for 45 minutes with HS in comparison to SVR after IS administration.
• Fifteen minutes after HS administration, the mean plasma AVP concentration saw a notable increase, which sustained for 90 minutes.

Conclusions

• Upon a bolus of HS application, there was a significant rise in blood pressure in healthy, isoflurane-anesthetized horses.
• The study attributed this effect to volume recruitment and an increase in systemic vascular resistance.
• Therefore, hypothesizing that the administration of HS might be a potential method for improving arterial blood pressure in anesthetized horses.