Preliminary results of fetal cardiac bypass in nonhuman primates.
OBJECTIVE
Fetal cardiac surgery has potential benefits for treatment of some congenital heart defects. However, placental dysfunction as a result of fetal bypass, fetal stress, and fetal exposure to external milieu needs to be overcome to optimize the outcomes of fetal cardiac bypass. In this study we evaluated the technical feasibility of cardiac bypass in the nonhuman primate fetus and the efficacy of different anesthetic approaches.


METHODS
Twelve baboon fetuses, average gestation 146 +/- 8 days and weight 696 +/- 184 g, were used. Three fetuses were excluded from the study because of nuchal cord presentations. The animals were separated into two anesthesia groups: isoflurane (n = 6) and fentanyl and midazolam (n = 3). A miniature roller pump circuit without oxygenator was used for fetal bypass for 30 minutes. No blood transfusion was performed. Fetal blood gas samples were collected before bypass, during bypass, and at 15 and 60 minutes after bypass.


RESULTS
All fetuses in the isoflurane group were successfully placed on the cardiac bypass circuit. However, 2 animals in the fentanyl and midazolam group were not placed on the bypass circuit because of sustained elevation in maternal uterine tone. All maternal baboons survived. Of the 6 fetuses in the isoflurane group, 5 survived for 60 minutes; however, placental function continued to deteriorate after bypass (Pa o 2 33 +/- 3 mm Hg before bypass, 23 +/- 6 mm Hg 15 minutes after, and 18 +/- 9 mm Hg 60 minutes after).


CONCLUSIONS
The technical feasibility of cardiac bypass in nonhuman primate fetuses weighing less than 1000 g was confirmed. Isoflurane anesthesia appears to be superior to fentanyl and midazolam anesthesia for fetal cardiac surgery because of adequate uterine relaxation.
Ikai
Akio
A
Department of Cardiothoracic Surgery, Division of Pediatric Cardiac Surgery, Stanford University School of Medicine, CA, USA.
Riemer
R Kirk
RK
Ramamoorthy
Chandra
C
Malhotra
Sunil
S
Malhatra
Sunil
S
Cassorla
Lydia
L
Amir
Gabriel
G
Hanley
Frank L
FL
Reddy
V Mohan
VM
D000768:Anesthesia, General / Q000379:methods; D018686:Anesthetics, Intravenous / Q000008:administration & dosage*; D000818:Animals; D001784:Blood Gas Analysis; D001795:Blood Pressure Determination; D002302:Cardiac Output; D002315:Cardiopulmonary Bypass / Q000379:methods*; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage; D005318:Fetal Heart / Q000002:abnormalities / Q000601:surgery*; D006439:Hemodynamics / Q000502:physiology; D007530:Isoflurane / Q000008:administration & dosage; D010215:Papio; D011247:Pregnancy; D011270:Pregnancy, Animal; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D016896:Treatment Outcome
D018686:Anesthetics, Intravenous; D007530:Isoflurane; D005283:Fentanyl