| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Ann Thorac Surg 1996;61:779-780
© 1996 The Society of Thoracic Surgeons
Department of Cardiac Surgery, Children's Hospital, Boston, Massachusetts
In this edition of The Annals Eke and colleagues [1] have addressed the important issue of the possible deleterious neurologic effects of deep hypothermic circulatory arrest. This is a courageous study in that the patient population is predominantly patients with hypoplastic left heart syndrome who underwent cardiac transplantation in the first months of life. These patients frequently suffer profound metabolic insults before diagnosis and often must be maintained in the intensive care unit for long periods of time in a parlous state while waiting for an appropriate donor. Eke and colleagues have concluded from their study that neither the duration of circulatory arrest nor the rate of cooling to achieve deep hypothermia influences subsequent developmental outcome. These conclusions have very important implications for the conduct of surgical procedures for children with congenital heart disease and warrant careful examination.
Eke and colleagues used the Bayley scales of infant development to study retrospectively a small group of 38 infants who had undergone cardiac transplantation using a relatively uniform protocol of deep hypothermic circulatory arrest. They found a mean mental development score (a precursor measure of cognitive ability) of 88. Recent normative data suggest that the mean score for children without heart disease is 112. A score of 80 to 89 is considered ``low average.'' Nearly one third of Eke and colleagues' study patients achieved scores less than 80, which is considered borderline intellectually deficient. Although the explanation for this disappointing result may be developmental anomalies associated with congenital heart disease or the stress of the preoperative insult, Eke and colleagues have provided no evidence that such is the case. In fact, in a recent prospective, randomized study of developmental outcome in 171 infants with transposition of the great arteries who in many cases suffered hypoxic and acidotic stress preoperatively, the mean mental development index was 105 [2]. In that study patients randomized to circulatory arrest had a significantly worse neurologic outcome than patients randomized to continuous low-flow bypass. There was also an important association in that study between longer circulatory arrest time and lower score on the psychomotor development index of the Bayley scale at 1 year of age. Although Eke and colleagues state that ``some of the patients with the longest deep hypothermic circulatory arrest times in our study had the best Bayley scores,'' a cursory examination of Figure 3 reveals that children with the longest deep hypothermic circulatory arrest periods also achieved some of the lowest Bayley scores.
Eke and colleagues have not discussed the power of their study to detect differences given the small sample size and narrow range of both arrest times and cooling times. Figures 1 and 3 illustrate that the majority of patients underwent a cooling duration of between 10 and 17 minutes and an arrest time of between 45 and 65 minutes. In the prospective, randomized study reported by Newburger and associates [3] and Bellinger and co-workers [2] there was a wide range of arrest times between 10 and 60 minutes. That study described an association between arrest duration and many outcome variables including neurologic and developmental outcome as well as the incidence of perioperative seizures. No child who had an arrest duration of less than 35 minutes had a seizure. Perioperative seizures correlated with worse developmental outcome at 1 year of age and in preliminary analysis also correlated strongly with worse developmental outcome at 4 years of age. It would have been of interest for Eke and colleagues to report the incidence of clinically detected seizures in their study group. Newburger and associates [3] have demonstrated that clinical seizures represent a small proportion of seizures that are found if continuous electroencephalographic monitoring is undertaken for 48 hours postoperatively.
Eke and colleagues have emphasized that there are many procedural variables in the technique of deep hypothermic circulatory arrest that may influence subsequent neurologic and developmental outcome. Their own technique of hematocrit manipulation represents an extreme position in that they use a blood-free prime and severely hemodilute to a hematocrit of 5%. They argue that with profound hypothermia dissolved oxygen alone is adequate to supply the brain's metabolic needs. However, because they prefer not to allow any preliminary surface cooling including the simple cooling by convection and radiation that occurs in the operating room during anesthesia induction and line placement, the baby's metabolic needs will still be high when bypass is first commenced. In a recent (as yet unpublished) laboratory study using immature piglets my colleagues and I have indeed confirmed that such an extreme degree of hemodilution results in important loss of cerebral high-energy phosphates determined by magnetic spectroscopy as well as reduction of cytochrome aa3 determined by near-infrared spectroscopy. Interestingly a protocol of high hematocrit (>30%) employed clinically by Planche's group at Marie Lannelongue for deep hypothermic operations in infants was associated in our piglet model with improved preservation of brain energy state as well as improved neurologic and histologic outcome relative to a protocol of extreme hemodilution as used by the Loma Linda group and relative to a more standard hematocrit of 20% as employed at Boston Children's Hospital and Great Ormond Street, London, for example [4]. In fact, the evidence that hemodilution is beneficial during deep hypothermic circulatory arrest is not strong, leading Eke and colleagues to support their approach with statements such as ``one may imagine that if inflexible red cells are clumped in the microvasculature...'' rather than with firm data. Such statements have been repeated in the literature for many years and bear careful reexamination with new studies employing modern-day bypass circuits and methods.
In conclusion, Eke and colleagues have made an important contribution by demonstrating that there is considerable room for improvement in methods of brain protection in children undergoing heart operations. Although their small retrospective study did not demonstrate an association of cooling time or arrest time with developmental outcome, it is important to interpret this study in the light of the small study numbers, narrow range of cooling and arrest times, and the extreme degree of hemodilution employed. Until further data are forthcoming, congenital heart surgeons would be wise to limit circulatory arrest time to less than 30 to 45 minutes whenever possible, and where possible to avoid its use altogether.
Footnotes
Address reprint requests to Dr Jonas, Department of Cardiac Surgery, Children's Hospital, 300 Longwood Ave, Boston, MA 02115.
References
Related Article
This article has been cited by other articles:
|
|
 |
|
  S. Schubert, G. Stoltenburg-Didinger, A. Wehsack, D. Troitzsch, W. Boettcher, M. Huebler, M. Redlin, M. Kanaan, M. Meissler, P. E. Lange, et al. Large-Dose Pretreatment with Methylprednisolone Fails to Attenuate Neuronal Injury After Deep Hypothermic Circulatory Arrest in a Neonatal Piglet Model Anesth. Analg., November 1, 2005; 101(5): 1311 - 1318. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. H. Hovels-Gurich, M.-C. Seghaye, M. Sigler, F. Kotlarek, A. Bartl, J. Neuser, R. Minkenberg, B. J. Messmer, and G. von Bernuth Neurodevelopmental outcome related to cerebral risk factors in children after neonatal arterial switch operation Ann. Thorac. Surg., March 1, 2001; 71(3): 881 - 888. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Suominen, R. Palo, H. Sairanen, K.T. Olkkola, and J. Rasanen Perioperative determinants and outcome of cardiopulmonary arrest in children after heart surgery Eur. J. Cardiothorac. Surg., February 1, 2001; 19(2): 127 - 134. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. Hraska, M. Nosal, P. Sykora, V. Sojak, M. Sagat, and P. Kunovsky Results of modified Norwood's operation for hypoplastic left heart syndrome Eur. J. Cardiothorac. Surg., August 1, 2000; 18(2): 214 - 219. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. H. Hovels-Gurich, M.-C. Seghaye, S. Dabritz, B. J. Messmer, and G. von Bernuth COGNITIVE AND MOTOR DEVELOPMENT IN PRESCHOOL AND SCHOOL-AGED CHILDREN AFTER NEONATAL ARTERIAL SWITCH OPERATION J. Thorac. Cardiovasc. Surg., October 1, 1997; 114(4): 578 - 585. [Abstract] [Full Text]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
