Asian Cardiovasc Thorac Ann 2002;10:3-7
© 2002 Asia Publishing EXchange Pte Ltd
Cardiac Surgery Under Perfusionless Hypothermia: Siberian Experience
Alexander M Karaskov, MD,
C Saifuddin Kitchlu, FRCS,
Vladimir N Lomivorotov, MD
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Department of Cardiac Surgery, Research Institute of Circulation Pathology, 15 Rechkunovskaya str. 630055, Novosibirsk 55, Russia
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Vladimir N Lomivorotov, MD Tel: 7 3832 32 4550 Fax: 7 3832 32 4550 e-mail: vlomivorotov{at}hotmail.com Department of Cardiac Surgery, Research Institute of Circulation Pathology, 15 Rechkunovskaya str. 630055, Novosibirsk 55, Russia.
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ABSTRACT
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Between January 1995 and December 1999, 942 patients (452 males and 490 females) aged 1 to 51 years underwent definitive surgery under perfusionless hypothermia for correction of congenital heart defects, predominantly uncomplicated ventricular or atrial septal defects (80%). Hypothermia of 24°C to 28°C was achieved in 15 to 45 minutes (mean, 25.7 ± 1.2 minutes) by application of crushed ice over the body and head. Aortic crossclamp time ranged from 10 to 76 minutes (mean, 26.1 ± 0.25 minutes). Cardiac restoration time ranged from 1 to 10 minutes (mean, 2.1 ± 0.08 minutes). Eight patients (0.85%) died postoperatively: 4 from acute cardiac insufficiency, 2 as a consequence of technical faults, 1 from persistent pulmonary hypertension, and 1 had sudden cardiac arrest. None of the surviving patients showed any gross neurological deficit. Perfusionless hypothermic cardiac surgery, when applied appropriately, is safe and simple, and might still have a place in treating a selected group of patients with uncomplicated congenital heart defects.
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INTRODUCTION
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In 1950, Bigelow and colleagues1 with visionary outlook, first described the role of hypothermia in open-heart surgery. Two years later, on September 2, 1952, Lewis and Taufic2 performed an operation for closure of an atrial septal defect in a 5-year-old girl under perfusionless hypothermia. This was the first successful operation in the history of cardiac surgery, performed inside the heart under direct vision.3 Over the next two decades, cardiac surgery under simple perfusionless hypothermia or the modified form, Drew's technique, was practiced across the continents with variable success.4–11 With the technological improvement of cardiopulmonary bypass, most cardiac centers abandoned operating under perfusionless hypothermia. Our center, established over 40 years ago, continued using this method and developed it further as a safe technique for use in definitive surgery for congenital heart defects.12,13 This study reviews the outcome of operations during the 5-year period 1995 to 1999, in the light of previous experience.
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PATIENTS AND METHODS
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Between January 1995 and December 1999, 942 patients (452 males and 490 females) underwent definitive surgery for congenital cardiac malformations under perfusionless hypothermia. All patients had a definite diagnosis by physical examination, chest radiography, and echo-cardiography. Uncomplicated ventricular septal defect (VSD) and atrial septal defect (ASD) were the main cardiac malformations treated in this series (Table 1
). At the time of operation, the mean age of the patients was 8.7 ± 0.9 years (range, 1 to 51 years). Figure 1 shows the distribution of age. Most of the patients were aged 3 to 7 years (50.7%); only 8% were below 3 years. The mean weight was 23.7 ± 0.5 kg (range, 12 to 55 kg). All operations were performed electively.
All patients had a neurological assessment before and after their operation. Descriptive evaluation of patient's wakefulness level, i.e., situational orientation, voluntary behavior, verbal function, and emotional state were evaluated. Functions of 12 pairs of cranial nerves, voluntary movements of the limbs, state of muscle tone, handwriting, state of coordination and static function, and any abnormal movements (tic, hyperkinesia) were noted. All types of sensory function were assessed. Examinations of higher psychic function (neurocognitive examination) were carried out by Luria's method.14 Patients were subjected to a battery of specially adapted psychological tests to determine their psychomotor and intellectual status. The technique consisted of sequential evaluation of praxis of posture against a visual and tactile table, ability to transfer tactile information from the right hand to the left and vice versa, bimanual spatial tests, state of reciprocal coordination, examination of regulation of voluntary movements, actions with tests for dynamic praxis, and examination of oral praxis. One of the advantages of Luria's method is that it can relate a function to a particular brain area. These tests were repeated in the postoperative period while the patients were in hospital and in the follow-up clinic, and compared with the preoperative findings. Parents were questioned regarding any neurological events in the past or after the operation.
The general principles of anesthesia and operative technique were not significantly different from those described previously.12,13 Induction of anesthesia with atropine 0.01 mg•kg-1, diazepam 0.15 to 0.25 mg•kg-1, ketamine 5 mg•kg-1, and pipecuronium 0.08 to 0.1 µg•kg-1 was followed by endotracheal intubation. Anesthesia was maintained with ether and with total muscle relaxation (pipecuronium, 0.06 µg•kg-1). For general monitoring, central venous and arterial lines were inserted, and a wide-bore cannula was placed in the femoral vein. Controlled hyperventilation with a fraction of inspired O2 of 50% was maintained to achieve high pO2 and low pCO2 (arterial pCO2 was approximately 25 mm Hg). Heparin (0.6 mg•kg-1) and insulin (0.5 U•kg-1) were injected intravenously. Low-molecular-weight dextran was infused at a dosage of 0.5 g•kg-1.
There were 3 decision-making stages during the operating procedure, which related to the esophageal temperature. Cooling was initiated by covering the body with finely crushed ice and cooling the head with an ice pack placed in a fabric helmet. When the temperature dropped to 29°C to 30°C with this active cooling, ice was removed from the body (stage I), but the ice pack was kept around the head for further cooling. The chest was entered via a bilateral thoracosternotomy (clamshell incision) and slings were passed around the aorta, superior vena cava, and inferior vena cava. During these maneuvers, the temperature dropped further due to cooling of the head, and when it reached 24°C to 28°C (depending on the expected aortic crossclamp time), the intracardiac part of the operation was started (stage II). A repeat dose of heparin (2 mg•kg-1) was injected into the heart and a 4% solution of sodium bicarbonate (2 mg•kg-1) was administered to avoid respiratory and metabolic alkalosis during aortic occlusion. In quick succession, the snares on both venae cavae were tightened and an aortic crossclamp was applied. Cold cardioplegic solution (400 mL of 0.9% sodium chloride, 7 mL of 4% potassium chloride, 10 mL of 4% sodium bicarbonate, 30 mg of prednisolone, 0.5 mL of 2% papaverine, and 1 mL of 25% magnesium sulphate) was injected through the aortic root. Repeat doses of cardioplegic solution were infused at 25- to 30-minute intervals or when needed. To prevent cerebral hypertension, all intravenous fluids were administered through the femoral vein during the main intracardiac procedure, and if over 20 minutes, blood was vented from the superior vena cava at a rate of 0.5 to 1.0 mL•kg-1 through a cannula passed from the right atrium, and repeated every 10 minutes during aortic occlusion. All collected blood was autotransfused. Towards the end of stage II, the fabric ice helmet was removed. On completion, the caval snares were released, deairing was performed, the aortic crossclamp was removed, and direct cardiac massage was used to restore cardiac activity. Occasionally, electrical defibrillation was needed to revert to sinus rhythm. Intravenous injection of calcium chloride, epinephrine or norepinephrine, or sodium bicarbonate was sometimes needed at this stage. Rewarming was started by irrigating the pleural cavities with warm physiological solution (42°C to 43°C). To ensure adequate diuresis, intravenous injection of frusemide and infusions of dopamine (< 3 µg•kg-1•min-1) and mannitol (0.5 to 1.0 g•kg-1) were started. Once the temperature reached 33°C to 35°C (stage III), the chest was closed after thorough hemostasis. The patient was transferred to the intensive care unit and rewarming was continued (from 1998) with a Bair Hugger blanket (Augustin Medical, Inc., MN, USA).
All 942 patients underwent definitive corrective surgery by standard operative techniques. The ASD repairs were carried out by direct suture or use of a pericardial patch. A pericardial patch was used in most cases of VSD and in all cases of partial anomalous pulmonary venous connection (PAPVC). The active cooling time before aortic occlusion was 25.7 ± 1.2 minutes (range, 15 to 42 minutes). The duration of cardiac arrest and restoration of circulation following completion of the definitive part of the operation is shown in Table 2. The mean circulatory arrest time was 26.1 ± 0.25 minutes (range, 10 to 76 minutes). Time for rewarming was 96.1 ± 3.7 minutes (range, 45 to 125 minutes). The most complicated cardiac malformations in this series were treated in the initial two years (1995 to 1996) when 9 patients with complete atrioventricular canal and one with tetralogy of Fallot underwent surgery.
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RESULTS
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Perioperative complications occurred in 55 patients who developed transient ventricular fibrillation at the end of the cooling phase, mostly from cardiac manipulation; all were successfully defibrillated. A 51-year-old man undergoing ASD repair suffered cardiac arrest during cooling at a temperature of 28°C. An immediate thora-cotomy proceeded to aortic occlusion and repair of the ASD. At 2.5 hours after the operation, he had a further cardiac arrest and was resuscitated. He required ventilation for 17 days and was discharged on the 47th day, having made a full recovery. One patient needed 2 aortic occlusions due to faulty initial repair of PAPVC; this patient ultimately died. Four patients had aortic occlusion times of more than 60 minutes (up to 76 minutes in a case of PAPVC), but their cardiac function was restored without difficulty and they did not show any neurological deficit. Table 3 shows postoperative mortality and morbidity.
Eight patients (0.85%) died postoperatively, 6 of whom had undergone VSD repair. A 12-year-old girl who had multiple VSDs died on the 12th postoperative day. Autopsy showed a residual VSD with myocardial fibrosis and pulmonary edema. A 2-year-old girl underwent VSD repair and had persistent pulmonary hypertension in the postoperative period; she died following cardiac arrest on the 8th day. Four others died within 24 hours of operation due to acute cardiac insufficiency. A 12-year-old girl died after ASD repair due to cardiac arrest at 10 hours postoperatively. A 32-month-old boy needed circulatory arrest on two occasions due to faulty initial repair of PAPVC; he did not regain consciousness and died on the 6th day. The other 7 patients who died had regained consciousness after their operations and showed no signs of neurological deficit. Eight patients (0.85%) developed transient neurological abnormalities; they displayed irritability and hypertonia. All were discharged after recovering fully. Six were followed up for 1 to 4 years, and no residual defect was found. Two patients, including the 51-year-old man, were lost to follow-up.
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DISCUSSION
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Operation under moderate hypothermia is vital in open-heart surgery with the perfusionless method.15 The beneficial effects of low-molecular-weight dextran infusion and prevention of respiratory and metabolic alkalosis during aortic occlusion play major roles in this method.16,17 Thus at our institute, hypothermia in cardiac surgery has been further developed with continuing improvement, as shown in Table 4. This is due to progress in cardiac surgery in general as well as changes we have adopted over the years.12,13
Due to relatively higher mortality in the group with high-risk congenital heart defects in the past, we now operate on these patients under cardiopulmonary bypass.12,13 It is apparent that the number of operations has reduced in recent years and this is due to our policy of operating under hypothermia only on selected patients, such as those with uncomplicated acyanotic congenital heart lesions, a body weight between 10 and 65 kg, and anticipated circulatory arrest time < 60 minutes. In this series, 75 patients (8%) were below 3 years old and only 15 (1.6%) were above 15 years old. We find older age and increased body weight make resuscitation difficult, as noted in another study.9 Although earlier reports indicated encouraging results in very young patients operated under perfusionless hypothermia, we now feel it is safer to operate on babies of less than 10 kg under cardiopulmonary bypass.5,8
Surface cooling by direct application of ice chips is a quick and safe method, and although a local effect of ice (frostbite) has been reported, such a complication has never been encountered in our vast experience.18 Biochemical changes during the operation have been described in detail; no significant deleterious effect has been noted.6,9,13 The cerebral vasoconstrictive effect of alkalosis during the cooling period was counteracted by progressive cerebral cooling and ether anesthesia. The degree of metabolic acidosis that usually develops during the rewarming period was corrected within 2 to 3 hours of its completion. We used the lungs as the primary heat exchanger, and the bilateral thoracosternotomy (clamshell incision) facilitated rewarming during warm pleural irrigation. This approach, although cosmetically attractive, damages the internal thoracic arteries. Operations through a median sternotomy have been carried out, in which the patients were placed in water for cooling and rewarming.5,6
One of the major criticisms of perfusionless cardiac surgery is the risk of cerebral damage.11 In addition to maintenance of moderate hypothermia and the use of low-molecular-weight dextran during the operation, we have developed a number of neuroprotective methods including selective head cooling. In stage II, when the esophageal temperature reaches 24°C to 28°C, the actual tympanic temperature drops a further 6°C to 7°C, which provides anti-hypoxic protection of the brain for 60 minutes or more during the circulatory arrest period.12,13 To prevent cerebral venous congestion, all intravenous fluids were administered through the femoral vein during aortic occlusion. In 4 patients who had circulatory arrest of more than 60 minutes (76 minutes in one case), the cardiac restoration time was quick, and they did not show any neurological deficit postoperatively. In recent years, research has shown that a modest reduction of brain temperature is the most promising neuroprotective strategy.19 In this series, only one patient was encountered who did not regain consciousness and died later as a consequence of a technical fault during the operation, which necessitated repeated aortic occlusion. It is true that there is little room for error during the definitive intracardiac procedure. It should ideally be completed within 1 hour of aortic occlusion.
Long-term follow-up of a patient who underwent surgery under perfusionless hypothermia in early infancy showed no adverse effects on somatic, psychomotor, or intellectual development.20 Our ongoing neuropsychological study based on Luria's method has not shown any gross abnormality in these patients.14 In this series, 8 patients suffered transient neurologic symptoms that developed in the immediate postoperative period, but resolved after a short period. We have not noticed any negative effect on somatic development after the operation. The psychomotor and intellectual behavior of these patients was carefully evaluated in the follow-up period and found to be within the normal range or without deterioration of the pre-operative status. However, we were unable to study all patients in the postoperative period as many of them live in the forbidding climate of the vast Siberian region.
The spectrum of patients that can be operated under perfusionless hypothermia is obviously narrow, but even within this category there are many who need surgery for cardiac defects, particularly in developing countries. Our current aim for further development is to reduce the rewarming time and achieve surgical access via a median sternotomy. This study confirms that cardiac surgery under perfusionless hypothermia, when applied appropriately, is a safe and simple method for treating selected uncomplicated patients with congenital heart defects, and it might still have a place in current surgical practice.
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This article has been cited by other articles:
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T. Sakamoto, T. Asou, Y. Takeda, K. Date, and M. Nanaumi
Long-Term Outcome of Intracardiac Repair Under Simple Deep Hypothermia
Asian Cardiovasc Thorac Ann,
December 1, 2006;
14(6):
458 - 461.
[Abstract]
[Full Text]
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ABSTRACT
INTRODUCTION
