Endocrine changes in cerebrospinal fluid, pituitary effluent, and peripheral plasma of anesthetized ponies.

The research investigates how different forms of anesthesia affect pituitary-adrenal activity in ponies. The results suggest that intravenous anesthesia suppresses pituitary secretion more than inhaled anesthesia and produces lesser cardiorespiratory depression.

Methodology

• Nine healthy ponies – 5 geldings and 4 mares – were involved in the study.
• Catheters were placed in two separate areas: the cavernous sinus below the pituitary gland and in the subarachnoid space via the lumbosacral space.
• After 72 hours, two types of anaesthesia protocols were followed.
• For inhaled anesthesia, acepromazine was followed by induction of anesthesia with thiopentone and then maintenance with halothane. This is referred to as the halothane protocol.
• For the IV protocol, anesthesia was induced with detomidine and ketamine, followed by maintenance with an IV infusion of a detomidine-ketamine-guaifenesin combination.
• Several health parameters like arterial blood pressure and gas tensions were measured throughout the anesthesia process. Peptide and catecholamine concentrations in different sources, such as pituitary effluent, peripheral plasma, and CSF, along with peripheral plasma cortisol, glucose, and lactate concentrations, were also measured.

Results

• It was observed that intravenous anesthesia caused less cardiorespiratory depression than halothane.
• ACTH, metenkephalin, arginine vasopressin, and norepinephrine concentrations in pituitary effluent and peripheral plasma were higher during halothane anesthesia, and did not change much during intravenous anesthesia.
• Dynorphin concentrations did not change in either type of anesthesia.
• Only halothane anesthesia led to increased pituitary effluent plasma beta-endorphin and peripheral plasma cortisol concentrations.
• Hyperglycemia developed only during intravenous anesthesia, and minimal changes were observed in CSF hormonal concentrations during anesthesia.

Conclusion

• The research concluded that the pituitary gland plays a major role in maintaining circulating peptides during anesthesia.
• Compared to halothane, intravenous anesthesia appears to suppress pituitary secretion more effectively, offering potential benefits in managing endocrine changes during anesthesia.