Anesth Analg 2003;96:1526
© 2003 International Anesthesia Research Society
LETTERS TO THE EDITOR
Surgical Stress Response in Neonates and Premature Infants
Sam Golden, MD FAAP
Ronald McDonald Children’s Hospital, Loyola University Medical Center, Maywood, IL
To the Editor
I read the recent article by Gruber et al. (1) with interest. The authors concluded that large dose fentanyl did not eliminate a stress response to cardiac surgery using deep hypothermic cardiopulmonary bypass (DHCPB) in infants. These results have further caused doubt of the value of blunting the stress response during DHCPB.
The literature on surgical stress responses suggests the following:
- Although the stress response to DHCPB may not be eliminated by high-dose opiate, its magnitude is likely blunted (2–4).
- In neonates undergoing PDA ligation (2) and complex cardiac repairs (3) with DHCPB, an increase in clinical morbidity and the biochemical stress response was observed in the low-dose opiate "control" groups.
- Neonates dying after repair of complex cardiac lesions tended to have higher intra-operative stress responses that remained elevated for 24 h postoperatively compared with survivors (5).
- Whether this potential benefit in neonates is due to blunting the stress response intraoperatively or to maintenance of a 24-h postoperative opiate infusion, or both, is unclear.
- Improvement in outcome with blunting of the stress response has not been shown in older infants, children, and adults.
The stress response in neonates and premature infants is quantitatively and qualitatively different from that of older individuals. Neonatal stress hormone elevations to surgery exceed those of children and adults, but under most circumstances return to baseline at 24 h (6). It’s not unusual for a sick neonate to desaturate in response to a measure as benign as placing a stethoscope on the chest. This maladaptive response can be explained by recognizing that the neonate is still trying to adapt to an in uteroenvironment. The in utero stress response includes shunting blood away from the lungs and gut and towards the brain, heart, and placenta. The fetus does this by shunting blood right-to-left across the foramen ovale by pulmonary arterial vasoconstriction and away from the liver via dilation of the ductus venosus. Newborn conditions most sensitive to the detrimental effects of stress are those where pulmonary vascular resistance is high at birth such as persistent pulmonary hypertension of the neonate and meconium aspiration syndrome.
I would like to formulate the following hypotheses regarding this fetal-neonatal stress response:
- It is deleterious ex utero and should be blunted intraoperatively and for the first 24 h after major surgery in neonates.
- Studies beyond the neonatal period do not demonstrate clinical improvement with blunting the stress response because the infant has "outgrown" a fetal response. Exactly when the in utero response is outgrown is unknown but is probably after several weeks of life and may also be influenced by the degree and chronicity of in utero stress, gestational age, and current health status.
Dr. Hansen does not wish to respond.
References
- Gruber EM, Laussen PC, Casta A, et al. Stress response in infants undergoing cardiac surgery: a randomized study of fentanyl bolus, fentanyl infusion, and fentanyl-midazolam infusion. Anesth Analg 2001; 92: 882–90.[Abstract/Free Full Text]
- Anand KJS, Sippell WG, Aynsley-Green A. Randomized trial of fentanyl anaesthesia in preterm babies undergoing surgery: effects on the stress response. Lancet 1987; 1: 243–8.
- Anand KJS, Phil D, Hickey PR. Halothane-morphine compared with high-dose sufentanil for anesthesia and postoperative analgesia in neonatal cardiac surgery. N Engl J Med 1992; 326: 1–9.[Abstract]
- Duncan HP, Cloote A, Weir PM, et al. Reducing stress responses in the pre-bypass phase of open heart surgery in infants and young children: a comparison of different fentanyl doses. Br J Anaesth 2000; 84: 556–64.[Abstract/Free Full Text]
- Anand KJS, Hansen DD, Hickey PR. Hormonal-metabolic stress responses in neonates undergoing cardiac surgery. Anesthesiology 1990; 73: 661–70.[ISI][Medline]
- Anand KJS. Neonatal responses to anaesthesia and surgery. Clin Perinat 1990; 17: 207–14.[ISI][Medline]
