Asian Cardiovasc Thorac Ann 2006;14:458-461
© 2006 Asia Publishing EXchange Ltd
Long-Term Outcome of Intracardiac Repair Under Simple Deep Hypothermia
Takahiko Sakamoto, MD,
Toshihide Asou, MD,
Yuko Takeda, MD,
Kouichiro Date, MD,
Miwa Nanaumi, MD
Division of Cardiovascular Surgery, Kanagawa Children’s Medical Center, Yokohama, Japan
For reprint information contact: Takahiko Sakamoto, MD Tel: 81 3 3353 8111 Fax: 81 3 3356 0441 Email: takasakamoto{at}yahoo.co.jp, Department of Cardiovascular Surgery, The Heart Institute of Japan, Tokyo Women’s Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan.
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ABSTRACT
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Development of cardiopulmonary bypass has contributed to pediatric cardiac surgery, but at the dawn of cardiac surgery, simple deep hypothermia was used to avoid the deleterious effect of cardiopulmonary bypass. Between 1981 and 1990, 45 patients with simple cardiac anomalies underwent definitive surgery under deep hypothermia. Age at operation was 35 days to 20 months, and body weight was 2.3 to 8.0 kg. Under morphine and ether anesthesia, a median sternotomy was performed when the esophageal temperature reached 26.3°C ± 1.3°C by the application of surface cooling. At a minimum esophageal temperature of 19.6°C ± 2.3°C, inflow occlusion and cold cardioplegia were applied to induce circulatory arrest for 32.4 ± 10.2 min. Direct cardiac massage was used to restore cardiac activity during rewarming. All but one patient was in New York Heart Association functional class I postoperatively. The latest cardiothoracic ratio was 49.8% ± 4.7%. All but 2 patients are free from medication. Five of 30 patients showed developmental delay in the long-term; 2 of these had a long circulatory arrest period, and 3 had prolonged heart failure postoperatively. The other 25 patients had excellent physiologic and mental development. The long-term outcome of perfusionless hypothermic cardiac surgery is satisfactory when applied appropriately.
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INTRODUCTION
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Deep hypothermic circulatory arrest contributed greatly to the progress in successful treatment of congenital cardiac defects during the initial years of pediatric cardiac surgery. Two methods have been applied to induce hypothermia: a simple immersion technique and cardiopulmonary bypass (CPB).1,2 Due to the well-documented high probability of neurological impairment, the former was gradually abandoned after successful CPB was reported by Gibbon3 in 1953. We applied a simple immersion technique in some cases of simple cardiac defects until the 1980s, to reduce the deleterious effects of CPB. The purpose of this study was to review and evaluate long-term neurologic morbidity and clinical outcomes in our patients.
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PATIENTS AND METHODS
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Between 1981 and 1990, 45 patients underwent definitive surgery using a simple deep hypothermic technique at Kanagawa Children’s Medical Center. Preoperative diagnoses were ventricular septal defect (VSD) in 38, atrial septal defect in 1, coarctation of the aorta with VSD in 5, and interrupted aorta with VSD in 1. Age at surgery ranged from 35 days to 20 months, and body weight ranged from 2.3 to 8.0 kg. All 6 patients with an aortic arch anomaly underwent intracardiac repair in a staged approach after the initial arch repair with pulmonary artery banding via a thoracotomy. We reviewed outpatient records and assessed chest radiographs, electrocardiograms, New York Heart Association functional class, use of medication, and neurodevelopmental tests. A couple of neurological assessments such as the Wechsler Preschool and Primary Scale of Intelligence were performed for long-term evaluation.4 The Wechsler Scale is a standardized test to measure intellectual functioning in children. It is composed of 5 verbal subtests and 5 performance subtests, which yield separate verbal intelligence quotient (IQ) and performance IQ scores. A full-scale score is derived from the combined performance on these two scales. The mean IQ score is 100 ± 15.
Under morphine and ether anesthesia, a median sternotomy was performed when the esophageal temperature reached 26.3°C ± 1.3°C. Surface cooling was achieved using an Iwate Medical University model of a cooling bed (Figure 1
). Inflow occlusion and cardioplegic arrest were applied when the esophageal temperature reached 19.6°C ± 2.3°C. The mean duration of circulatory arrest was 32.4 ± 10.2 min. Cardiac activity was restored by direct cardiac massage during rewarming. All patients tolerated these procedures well and were transferred to the intensive care unit in a stable hemodynamic state (Figure 2).
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RESULTS
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A 3-month-old boy died of sepsis on the 10th postoperative day following patch closure of his VSD (hospital mortality, 2.2%). There was one late death in a girl who died suddenly from an unknown cause 18 months after direct suture closure of her atrial septal defect at 6 months old. Five re-operations were performed in 4 patients during a median follow-up of 14 years, ranging from 3 months to 20 years: repair of recoarctation of the aorta (10 months later), right ventricular outflow tract reconstruction for progressive double-chambered right ventricle (10 years later), resection of subaortic stenosis (4 and 11 years later), and kidney transplantation (14 years later).
Postoperative chest radiography showed a mean cardiothoracic ratio of 49.8% ± 4.7%. Sinus rhythm on the electrocardiogram was achieved in 39 patients (87%). Clinical conditions were excellent with New York Heart Association functional class I in all but one patient. Only 2 patients still required medication (Table 1). Among 30 patients (excluding 1 with pre-existing convulsions, 12 with chromosomal anomalies, and 2 non-survivors), 5 (17%) showed developmental delay on long-term neurological assessment. Two of these patients had circulatory arrest for > 50 min, and 3 suffered prolonged heart failure postoperatively. Using the Wechsler scale, the verbal IQ was 50–70, performance IQ was 59–75, and the full-scale score was 50–67 in the 5 patients who had developmental delay. The other 25 patients (83%) showed excellent physiologic and mental development.
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DISCUSSION
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This study demonstrates that the long-term outcome of pediatric cardiac surgery using simple deep hypothermia is fairly good when the duration of circulatory arrest is within an acceptable range and stable hemodynamics are achieved. There have been a few reports consistent with these results.5–8 Although simple deep hypothermia has been abandoned in the modern practice of cardiac surgery, the long-term outcome provides some important insight into improving current practice. This study indicates that several factors may affect the long-term outcome in patients undergoing intracardiac repair: temperature, hematocrit, and duration of deep hypothermia.
The optimal temperature is controversial. Some prefer moderate hypothermia and others emphasize that deep hypothermia is mandatory for brain protection during circulatory arrest. Karaskov and colleagues6 favored moderate hypothermia because tympanic temperature drops further by 6°C to 7°C after the esophageal temperature reaches 24°C to 28°C. On the other hand, Tisherman and colleagues9 recommended that ‘too deep hypothermia’ (< 10°C) should be avoided because it produces edema of the lungs while protecting the brain from ischemia. We employed a minimum esophageal temperature of 19.6°C ± 2.3°C in this study. On the basis of the above reports, the temperature employed in our series should be acceptable. The time to cool down the body before inducing circulatory arrest is also believed to be an important factor in neurological outcomes. Cooling took more than 30 min in our patients, and Bellinger and colleagues10 employed a similar time when they used CPB for cooling and rewarming.
The optimum hematocrit is also controversial. From the very beginning of the development of CPB, hemodilution was believed necessary to prevent the increased viscosity and rigidity of red blood cells from disturbing the microcirculation during hypothermia.11,12 In many centers, moderate hemodilution (hematocrit of 20%) has been adopted during hypothermic CPB.13,14 However, recent advances, including the intravital microscope, revealed no rigidity during CPB even with a hematocrit of 30%.15–18 A clinically beneficial effect of a higher hematocrit on cerebral function has been reported in a randomized clinical trial. Hypothermia may disturb oxygen delivery by inducing a leftward shift of the oxyhemoglobin dissociation curve. Furthermore, hemodilution could limit oxygen delivery to neurons under hypothermia. The hematocrit in our series was kept > 30%; this was considered to be one of the reasons for good neurologic outcomes in this study, and may be important when using CPB.
The duration of hypothermic circulatory arrest has an important influence on neurologic function in the early and long-term outcome. Careful consideration of the indications for this technique is important to reduce the duration of circulatory arrest. In most of our cases, the time ranged within an acceptable duration because this technique was not used in complex cases. A safe duration of circulatory arrest should be 40 minutes at 15°C after cooling with a hematocrit of 30%.19
The relatively large cannulas used 30 years ago when CPB was still developing, distorted or limited the view of the surgical field, affecting the accuracy of repair in any skilled cardiac surgeon’s hands. Following recent advances in the heart-lung machine, simple deep hypothermia has not been used in modern practice. However, the possible mechanisms for the good long-term outcomes in this study suggest that they are useful in the practice of cardiac surgery even in the current era. These include a higher hematocrit and deep hypothermia during circulatory arrest. In addition, we believe that this perfusionless hypothermic technique can be successfully achieved with ether anesthesia administered by skilled anesthesiologists. If a real-time neuromonitoring system, such as near-infrared spectroscopy, was used in these patients, more accurate findings might be obtained.20 Although satisfactory clinical outcomes were achieved, careful follow-up of these patients is required.
Presented at the 13th Annual Meeting of the Asian Society for Cardiovascular Surgery, Chiang Mai, Thailand, February 5–8, 2005.
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ACKNOWLEDGMENTS
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The contribution of the following cardiac surgeons, perfusionists, and anesthesiologists is gratefully appreciated by the authors: Kenji Ito, MD, Yasunori Okawa, MD, Tadayoshi Akasaka, MD, Nobuhiro Nagata, MD, Ryouichi Fujishima, CCP, Masaya Miura, CCP, and Osamu Fukatsu, MD.
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ABSTRACT
INTRODUCTION
