Effect of rapid and slow intravenous injection of sodium penicillin on arterial blood pressure in isoflurane-anesthetized horses during surgery.

The research explores the impacts of rapid and slow intravenous administration of sodium penicillin on the arterial blood pressure of horses while under isoflurane anesthesia during surgery. The study established that both methods resulted in a decrease in arterial blood pressure, albeit to a lesser extent in the case of the slower and more diluted injection.

Methodology

The research was conducted through a prospective randomized clinical trial. The subjects involved were 29 client-owned horses of various breeds, with ages ranging from 1 to 20 years old and body masses between 360 and 710 kg.

• The horses were anesthetized using various protocols, and the anesthesia was sustained with isoflurane facilitated by mechanical ventilation.
• Hourly doses of intravenous lidocaine and an infusion of dexmedetomidine were administered throughout.
• Every two hours following the preoperative dose, the horses received intraoperative penicillin, which was administered intravenously and reconstituted with 50 mL of saline (‘small dilution’ or SD group) given over 1 minute, or with 250 mL of saline (‘large dilution’ or LD group) administered over 10 minutes.
• Various parameters, including systolic, diastolic and mean arterial blood pressures, heart rate, end-tidal isoflurane and carbon dioxide, dobutamine rate and arterial electrolytes, were recorded before and 20 minutes after the administration of penicillin. Results were compared between and within the groups using the two-way ANOVA statistical technique.

Results

The dosage and time of penicillin delivery were similar across both groups. However, the blood pressure rates responded differently.

• In the SD group, the systolic arterial pressure (SAP) significantly decreased by 4.8-9.6%, the diastolic arterial pressure (DAP) by 12.7-25.4%, and the mean arterial pressure (MAP) by 6.6-18.4% from the injection and continued at this level for 15-20 minutes.
• In contrast, in the LD group, significant decreases in DAP (13.8-18.5%) and MAP (10.1-13.9%) occurred within 3-15 minutes.
• The study also observed that the DAP and MAP rates in the LD group were higher than those in the SD group at 1 and 3 minutes.
• No significant difference was observed in the dobutamine rate and other variables between the two groups.

Conclusion

The research concludes that arterial blood pressure decreases in anesthetized horses given both rapid and slow intravenous sodium penicillin injections. However, the decline is less severe with the slower, more diluted LD group method. This insight could be critical in deciding the rate and dilution of sodium penicillin administration in surgical procedures involving horses under anesthesia.