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Hormonal response of the premature primate to operative stress
A F Taylor1, K P Lally, W J Chwals
1Department of Physiology, Southwest Foundation for Biomedical Research, San Antonio, TX.
Insights
Newly born premature primates show a significant endocrine stress response to surgery. The response, involving hormones like cortisol and catecholamines, is dependent on surgical severity, particularly concerning the patent ductus arteriosus (PDA).
Area of Science:
- Neonatal physiology
- Surgical endocrinology
- Primate research
Background:
- Limited data exists on the hormonal stress response in premature infants immediately after birth.
- Previous studies on newborn infants were conducted after initial postnatal adaptation.
Purpose of the Study:
- To evaluate the endocrine and hormonal response of the newly born premature primate to surgical stress.
- To investigate the impact of surgical intervention, specifically patent ductus arteriosus (PDA) management, on this response.
Main Methods:
- Premature baboons (75% gestation) underwent thoracotomy within 2 hours of life.
- Groups included PDA patency maintenance (formalin infiltration) and PDA ligation.
- Control group had no surgical intervention.
- Hormonal levels (epinephrine, norepinephrine, renin, cortisol) were measured over 96 hours.
- Echocardiograms monitored cardiac function and PDA status.
Main Results:
- Cortisol levels increased in all groups following surgery.
- Operative procedures significantly elevated catecholamine and renin levels in both surgical groups.
- PDA ligation resulted in a more pronounced increase in these hormones at 24 hours.
- The endocrine response was severity-dependent, reflecting hemodynamic demands.
Conclusions:
- The premature primate demonstrates a substantial and severity-dependent endocrine response to surgical stress.
- Early patent ductus arteriosus ligation imposes significant hemodynamic challenges, influencing the hormonal response.
- These findings provide crucial insights into neonatal surgical stress physiology.
Abstract:
There are few data on the hormonal response to operation in the premature infant. Studies examining the response of newborn human infants have been performed on patients beyond the first few days of life, where some adaptation to postnatal life has occurred. This study evaluated the response of the newly born premature primate to surgical stress. Premature baboons (75% gestation) were intubated, mechanically ventilated and underwent thoracotomy at 2 hours of life with exposure of the ductus arteriosus (PDA). In group 1, formalin was infiltrated to keep the ductus patent. In group 2, the PDA was ligated. Controls had no operation. Blood was drawn at 0, 6, 24, 48, 72, and 96 hours of age. Echocardiograms were performed to confirm patency or closure of the ductus and to monitor cardiac function. Epinephrine, norepinephrine, renin, and cortisol levels were measured. Cortisol levels rose in all groups. Operation stimulated a marked increase in catecholamine and renin levels in both operative groups, which was more marked in the group with PDA ligation at 24 hours. These data reflect expected pathophysiology since early PDA ligation exerts additional hemodynamic demand on the heart. In conclusion, the premature primate is able to mount a significant and severity-dependent endocrine response to stress.