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Eur J Cardiothorac Surg 2008;33:619-625. doi:10.1016/j.ejcts.2007.12.031
Copyright © 2008, European Association for Cardio-thoracic Surgery. Published by Elsevier. All rights reserved.
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Moderate versus deep hypothermia for the arterial switch operation — experience with 100 consecutive patients

Ardawan J. Rastana,*, Thomas Walthera, Nidal Al Alama, Ingo Daehnertb, Michael A. Borgera, Friedrich W. Mohra, Jan Janousekb, Martin Kostelkaa

a Department of Cardiac Surgery, Heart Center, University of Leipzig, Struempellstr. 39, 04289 Leipzig, Germany
b Department of Pediatric Cardiology, Heart Center, University of Leipzig, Struempellstr. 39, 04289 Leipzig, Germany

Received 10 September 2007; received in revised form 3 December 2007; accepted 20 December 2007.

* Corresponding author. Tel.: +49 341 865 1319; fax: +49 341 865 1452. (Email: rastan{at}rz.uni-leipzig.de).


   Abstract
Top
 Abstract
1. Introduction
 2. Material and methods
 3. Results
 4. Discussion
 5. Conclusion
 References
 
Objectives: To evaluate the impact of moderate versus deep perioperative hypothermia on postoperative morbidity in patients receiving the arterial switch operation (ASO). Methods: One hundred consecutive patients received the ASO from 9/98 to 4/06 using temperature-corrected full-flow moderate (M > 24 °C, n = 51) or deep hypothermic cardiopulmonary bypass (CPB) (D <20 °C, n = 49). Complex TGA morphology was present in 33 patients (M: 27.4%, D: 38.8%, n.s.). Median age was 9 days (M) versus 10 days (D) and body weight was 3.5 ± 0.7 kg (M) versus 3.6 ± 0.9 kg (D) (both p = n.s.). Follow-up was 3.7 ± 2.1 years. Results: Lowest perioperative rectal temperature was 25.3 ± 1.1 °C (M) versus 19.0 ± 0.8 °C (D), p < 0.001. Intraoperative blood transfusion (M: 231 ± 47 ml, D: 252 ± 112 ml, p = 0.04) and postoperative lactate level (M: 3.2 ± 1.3 mmol/l, D: 3.8 ± 2.4 mmol/l, p = 0.02) were lower under moderate hypothermia. One patient (D) suffered myocardial ischemia, required ECMO support and died. All other patients were safely weaned from CPB using dopamine (M: 3.0 µg/kg min, D: 3.4 µg/kg min, n.s.) and dobutamine (M: 5.6 µg/kg min, D: 6.7 µg/kg min, p = 0.048). Secondary chest closure was performed in 41% (M) versus 59% (D) (p = 0.04). Patients were extubated after 89 h (M) versus 126 h (D) (p = 0.03). Under moderate hypothermia ICU stay (M: 8.4 ± 4.7 days, D: 12.0 ± 13.8 days, p = 0.03) and hospital stay (M: 12.8 ± 6.8 days, D: 20.7 ± 15.5 days, p = 0.001) were shorter. Five-year freedom from reoperation was 97.0% for simple and 85.2% for complex TGA with RVOT reconstruction in 4/6 patients. Conclusions: The ASO under full-flow moderate compared to deep hypothermia was advantageous regarding length of procedure and primary chest closure rate. Moderate hypothermia seemed to be beneficial for pulmonary recovery, length of chest tube drainage treatment and inotropic support. No worse early or long-term effects of moderate hypothermia were found.

Key Words: Arterial switch operation • Moderate hypothermia • Deep hypothermia • Circulatory arrest • Transposition of the great arteries


   1. Introduction
Top
 Abstract
 1. Introduction
2. Material and methods
 3. Results
 4. Discussion
 5. Conclusion
 References
 
The arterial switch operation (ASO) is a standard procedure for correction of transposition of the great arteries (TGA) with good early and long-term results. Since its introduction by Adib Jatene and Magdi Yacoub in the middle of the 1970s, the ASO has become a reproducible surgical technique with perioperative mortality rate reported in the current era between 2.0% and 7.5% depending on the anatomical complexity, preoperative patients’ status and coronary anatomy [1–3]. At first the standard perioperative strategy consisted of deep hypothermic circulatory arrest (DHCA). With more experience, however, this strategy was modified to use deep hypothermic low-flow bypass with DHCA reserved for concomitant aortic arch pathology only. Avoiding DHCA may be beneficial regarding mid- and long-term neurodevelopmental status as it has been documented in randomized and non-randomized trials [4–9]. Supported by refinements in cardiopulmonary bypass (CPB) techniques and routine neonatal surgical management in recent years there are, although more or less unproved, growing opinions for using CPB with full-flow moderate hypothermia and even normothermia during ASO [10,11]. However, only few data on early and late results comparing CPB under different temperature protocols are available thus far [10]. As the optimal temperature strategy for ASO correction has not yet been identified, we herein report our experience with 100 consecutive ASO operations performed under temperature-corrected full-flow moderate (M) or deep (D) hypothermic CPB.


   2. Material and methods
Top
 Abstract
 1. Introduction
 2. Material and methods
3. Results
 4. Discussion
 5. Conclusion
 References
 
2.1 Patients and study design
Between August 1998 and April 2006 one hundred consecutive patients with TGA underwent ASO at our institution. Fifty-one patients were operated under moderate hypothermia defined as rectal temperature equal to or higher than 24 °C and 49 patients were operated under deep hypothermia with a rectal temperature of lower than 20 °C. However there was an element of time bias because in the early study period more patients were operated under deep and at the end of the study more patients were operated under moderate hypothermia. All procedures were carried out under temperature-corrected full-flow CPB (see below) by the same specialized operative team, including two scrub nurses, two anesthetists, two perfusionists and three surgical assistants. Ninety-five operations were performed by one surgeon (MK), in the others he was the senior assistant surgeon. The perioperative protocol was constant during the entire study period and other than the target temperature, identical for both groups. All clinical data were prospectively recorded. The study had been approved by our local ethics committee and the study design, anonymous data acquisition as well as data publication were performed in accordance with the Declaration of Helsinki.

Preoperatively the diagnosis of TGA was confirmed by clinical assessment and echocardiography, but no invasive hemodynamic studies were performed. Prostaglandin E1 was administered if systemic oxygenation saturation was <80%. Echo-guided balloon atrial septostomy (BAS) was routinely performed in all patients presenting with TGA and intact or restrictive interventricular septum. All patients received pre- and postoperative transcranial Doppler ultrasonography.

2.2 Cardiopulmonary bypass and surgical technique
Nasopharyngeal and rectal temperatures were continuously monitored. CPB was established by bicaval cannulation using 10 or 12 F metal-tipped angled USCI Pacifico cannulae (Bard, Inc., Billerica, MA, USA) and 2.0 mm pediatric aortic arch cannulae (Stöckert, Sorin Group Inc., Munich, Germany). Patients had full-flow CPB of approximately 3.0 L min–1 m–2 during cooling and rewarming. Bypass flow was reduced to 50–80% at 24 °C and 30–50% at 18 °C during cross-clamping period and was adjusted to keep the systemic venous oxygen saturation >70% and arterial pressure >30 mmHg. FiO2 was regulated to achieve an arterial pO2 of 150–250 mmHg. All procedures were performed using an S5 roller pump (Stöckert, Sorin Group Inc., Munich, Germany) and a Lilliput I oxygenator (Dideco D901, Sorin Group, Mirandola Modena, Italy). The tubing system (arterial 3/16, venous 1/4 in.) was miniaturized to a priming volume of 220–240 ml including 4 ml/kg body weight mannitol 15%, 5 ml sodium bicarbonate, 100 ml red cells, 100 ml 6%-hydroxyethyl starch (VitafusalTM HAES RAc 130/0.42, Serumwerk Bernburg, Germany), but no crystalloid solutions. We also used a single dose of 25 mg/kg methylprednisolone (UrbasonTM, Sanofi-Aventis Inc., Frankfurt, Germany) and 30.000 IE/kg aprotinin (TrasylolTM, Bayer AG, Leverkusen, Germany) in the priming solution. Aprotinin was also administered intravenously at CPB start and after decannulation.

We used St. Thomas cardioplegia solution with an initial dose of 30 ml/kg with repetitive application (10 ml/kg selectively in each coronary artery) for prolonged ischemic times of more than 90 min. The patients were cooled to a target temperature of either 18 °C (D) or 24 °C (M) using {alpha}-stat strategy throughout the whole procedure. During cooling pulmonary arteries were snared and the persistent ductus arteriosus was transected. No routine circulatory arrest was applied and limited to 1–4 min if required. Aortic arch repair was performed under selective cerebral and coronary perfusion and 30% flow rate before the arterial switch procedure.

Arterial switch procedures were performed in a standard manner using 7-0 polypropylene running sutures and included Lecompte maneuver in all patients. Glutaraldehyde treated autologous pericardium was used for reconstruction of the neopulmonary artery and VSD closure if necessary.

Conventional hemofiltration was performed during reperfusion. Hematocrit was 25–30% during CPB time. For weaning from CPB, inotropic medication was adjusted and hematocrit was raised to 35% after decannulation as described previously [12]. Chest closure was the aim in all patients with liberal indication for delayed sternal closure (DSC) in the presence of increased atrial pressures, decrease of arterial pressure or saturation shift during temporary sternal adaption.

2.3 Data analysis
Data are 100% complete. Continuous variables are expressed as mean ± SD and categorical data as proportions throughout the manuscript. Categorical variables were compared using the chi-square test or Fisher's exact and independent continuous variables were compared by two-tailed Student's test or Mann–Whitney U-test as appropriate. Comparison of related variables was performed by Wilcoxon test and paired samples t-test. Propensity to operate patients under deep versus moderate hypothermia was evaluated by odds ratio assessment of nine preoperative variables (age >10 days, body weight <3000 g, female gender, complex TGA, aortic arch pathology, coronary anomaly, preoperative ventilation, two-stage procedure, and previous balloon atrial septostomy). Complex TGA was defined as TGA with concomitant non-restrictive ventricular septal defect. Coronary anomalies were considered for all but type A pattern according to Yacoub's classification [13].

Nineteen dichotomous adverse peri- or postoperative outcome events were analyzed using a univariate and multivariate logistic regression model for both temperature strategies and expressed as odds ratio (OR) and 95% confidence intervals (95%CI).

Event-free survival was calculated by Kaplan–Meier methods with 95% confidence limits and log-rank test. p-values less than 0.05 were considered statistically significant. SPSS 13.0 and Microsoft Excel software package were used for statistical calculation.


   3. Results
Top
 Abstract
 1. Introduction
 2. Material and methods
 3. Results
4. Discussion
 5. Conclusion
 References
 
Patient baseline characteristics are shown in Table 1 . They were comparable for both study groups. In total 64% of patients demonstrated coronary anatomy type A, 7% type B, 2% type C, 18% type D, 4% type E and 5% hybrid forms according to Yacoub's classification. Thirty-three patients had ventricular septal defect with Taussig–Bing malformation in three patients. Three patients with TGA and intact ventricular septum had rapid two-stage procedure with pulmonary artery banding and modified Blalock–Taussig shunt 7–15 days before ASO procedure. Three patients with aortic arch pathology received aortic arch repair and pulmonary artery banding 3–6 months before definitive correction.


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  		Table 1 Characteristics of 100 consecutive patients undergoing the arterial switch operation using moderate or deep hypothermia
 
Comparing nine preoperative risk factors as listed above we found no variable as a significant predictor to perform the ASO procedure under moderate or deep hypothermia. However, there was a slight trend to operate on patients >10 days of age (OR 1.49, p = 0.328), with complex TGA (OR 1.67, p = 0.230) or with aortic arch pathology (OR 3.26, p = 0.313) under deep hypothermia.

The lowest rectal temperature recorded intraoperatively was 25.3 °C (moderate hypothermia = M) and 19.0 °C (deep hypothermia = D). Short periods of circulatory arrest of 1–4 min were performed in 8% (M) and 18% (D) of the patients. The total procedure duration was 223 ± 53 min (M) versus 289 ± 76 min (D) (p < 0.001). When patients were subdivided by simple or complex TGA correction, we uniformly found a shorter cross-clamp and reperfusion time under moderate hypothermia leading to a significantly shorter cardiopulmonary bypass and total procedure time (Fig. 1 ). It was an unexpected result that cross-clamping time was shorter in moderate compared to deep hypothermia. However, this was evident for both simple and complex ASO and was a consistent finding over the entire study period.


Figure 1
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  		Fig. 1. Procedural times for the arterial switch operation in simple and complex TGA using temperature-corrected full-flow moderate versus deep hypothermic cardiopulmonary bypass strategy.

 
As shown in Table 2 the respiratory minute volume and respiratory rate at the end of the operation was comparable under volume controlled ventilation between the groups. This could be achieved by significantly lower maximal ventilation pressures indicating better lung compliance at the end of the operation after moderate hypothermia.


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  		Table 2 Intraoperative data
 
Despite shorter reperfusion time in moderate hypothermia mean hemofiltration rate was significantly higher probably because of better venous return as a consequence of reduced capillary leakage and tissue volume shift. The higher hemofiltration rate led to higher fresh frozen plasma substitution while red cell transfusion rate was reduced (Table 2).

The two groups received a similar amount of milrinone, nitroglycerine (data not shown) and dopamine for hemodynamic support during weaning from CPB. The mean dobutamine dose was slightly, but significantly, higher in the deep hypothermia patients (Table 2). Another major finding was that delayed sternal closure was significantly more frequent in deep hypothermia compared to moderate hypothermia patients.

Perioperative mortality occurred in one patient (1.0%). This patient with simple TGA and complex coronary anatomy (intramural course) and deep hypothermic strategy developed right heart failure. The patient subsequently required ECMO support despite right coronary artery revision and died intraoperatively of uncontrollable bleeding.

Postoperative data of all survivors are presented in Table 3 . Mean postoperative drain loss was comparable during the first 24 postoperative h between both study groups. However, there was a significantly higher rate of reopening for bleeding and prolonged drainage treatment in deep hypothermia patients. Time to extubation and period of inotropic drug support was shorter under moderate hypothermia. As a consequence, ICU treatment time and length of hospital stay was markedly reduced in these patients.


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  		Table 3 Postoperative data
 
Regarding 19 adverse peri- or postoperative events by univariate analysis we found that relative risks for suffering adverse events were higher under deep hypothermia and none were higher under the moderate hypothermic strategy (see Fig. 2 ). These risks included prolonged CPB time >180 min (OR 19.0, CI 6.3–57.0, p < 0.001), cross-clamp time >100 min (OR 4.3, CI 1.8–10.4, p = 0.001), reperfusion period >60 min (RR 8.1, CI 2.8–24.0, p < 0.001), total procedure time >240 min (OR 19.4, CI 6.9–54.3, p < 0.001), delayed sternal closure (OR 2.2, CI 1.1–4.9, p = 0.047), drainage loss >150 ml/POD1 (OR 3.1, CI 1.2–7.7, p = 0.018), drainage treatment >4 days (RR 3.5, CI1.4–9.1, p = 0.009), inotropic support >6 days (OR 4.5, CI 1.8–11.7, p = 0.002) and hospital stay >15 days (OR 3.7, CI 1.6–8.6, p = 0.002). In multivariate analysis of CPB time >180 min (OR 10.3, CI 1.5–78.3, p = 0.045) and total procedure time >240 min (OR 11.2, CI 1.8–73.2, p = 0.025) were significantly more often associated with deep hypothermia strategy.


Figure 2
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  		Fig. 2. Odds ratios (OR) for the incidence of intra- and postoperative adverse events when operating under deep or moderate hypothermia in univariate analysis. OR >1 (right-hand side of the longitudinal bar) demonstrates higher risk under deep hypothermia. ORs are depicted with 95% confidence intervals, indicating significance when not crossing the midline bar.

 
The serum urea levels as well as white cell count data were not significantly different between groups (data not shown). There was a trend towards more adverse neurological events for patients operated under deep hypothermia. One (M) versus two (D) patients demonstrated early postoperative convulsive seizures and one (M) versus four patients (D) had evidence of intracerebral bleeding III° during postoperative transcranial Doppler ultrasonography.

Follow-up was performed at a mean of 3.7 ± 2.1 years postoperatively and was 100% complete. All except one deep hypothermic patient demonstrated no obvious signs of neurological or motoric backwardness as assessed during clinical follow-up examination by experienced pediatric cardiologists. This included all patients that suffered neurological events during the early postoperative course. Nine reoperations were required in six patients (Fig. 3 ). Two patients underwent reoperation for a significant residual VSD, one in Taussig–Bing malformation, and seven reoperations were performed on four patients because of supravalvular pulmonary stenosis. Freedom from reoperation was 89.6% (95%CI 85.2–94.0%) at 1 year and 87.0% (95%CI 82.0–97.0%) at 5-year follow-up for deep hypothermia and 100% at 1- and 5-year follow-up for moderate hypothermia (p = 0.015). Freedom from reoperation was 97.0% (95%CI 94.9–99.1%) at 1- and 5-year follow-up for simple TGA compared to 90.9% (95%CI 85.9–95.9%) at 1-year and 85.2% (95%CI 78.0–92.4%) at 5-year follow-up for complex TGA correction (p = 0.071).


Figure 3
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  		Fig. 3. Kaplan–Meier curve indicating freedom from reoperation after arterial switch operation for patients operated under moderate and deep hypothermia. p-values calculated by log rank test.

 

   4. Discussion
Top
 Abstract
 1. Introduction
 2. Material and methods
 3. Results
 4. Discussion
5. Conclusion
 References
 
Improvements in neonatal cardiac surgery during the past decades are well demonstrated by the operative correction of infants with TGA by the arterial switch operation. Thus, the ASO is an ideal example of the ‘Tour de France’, as Marc de Leval has described the success story of congenital heart surgery during the past decades [14]. The optimal temperature to use during the arterial switch procedure remains unclear. There are proponents of full-flow deep hypothermic, full-flow moderate hypothermic and even full-flow normothermic CPB. Taking into account the published benefits of low-flow CPB over DHCA, it might be logical to suggest that full-flow CPB is better than either strategy. Thus, although unproven, many centers have recently switched their ASO strategy to temperature-corrected full-flow CPB by using different minimum temperature targets ranging from 22 °C to normothermia [10,11,15,16]. Normothermic CPB and normothermic blood cardioplegia was recommended for the ASO by the Paris group, who found that most of the operative outcomes were comparable to hypothermia of 23–25 °C and none were worse [10]. However, in this context it had to be considered that complete absence of cooling is associated with a lower safety margin and increased potential risks if low-flow cardiopulmonary bypass or circulatory arrest periods are required because of unforeseen intraoperative technical difficulties.

One of the major limitations of temperature management is that the safe lower limit for different temperature strategies and reduced CPB flow remained poorly defined. Until more sophisticated monitoring methods are developed, it is likely that cardiac surgeons and perfusion teams will need to select bypass strategies that carry a significant safety margin providing acceptable flow rates and temperature. Thus, weighing evidence, logic and experience, most surgeons would accept an additional safety margin afforded by some degree of hypothermia [17]. Keeping this in mind, the aim of our study was to compare two temperature strategies of deep versus moderate hypothermia for ASO under otherwise constant conditions, with a particular focus on intraoperative events and postoperative outcome.

The definition of deep and moderate hypothermia during CPB varies in the literature. Based on the definition given by Williams, there are four grades of hypothermia, i.e. mild (32–35 °C), moderate (26–31 °C), deep (20–25 °C) and profound (<20 °C) hypothermia [18]. Because it is generally accepted in the pediatric cardiac surgery community that deep hypothermia involves cooling to 15–20 °C, while temperatures of 24–28 °C were considered as moderate hypothermia, we have used the latter definitions in the current study.

Our bypass circuit was miniaturized to a priming volume of 220–240 ml. It was recently shown that low-priming CPB circuits in neonatal cardiac surgery improve water balance during surgery and preserve postoperative organ function [19]. The small priming volume allowed us to adjust hemodilution to a hematocrit of approximately 25% during CPB without additional blood transfusion. In a randomized trial Jonas and co-workers were able to show a reduction in adverse perioperative and developmental outcome by using hematocrit levels of approximately 30% when compared to 20% [12]. We further used {alpha}-stat strategy during cooling and rewarming as reported by others [10,11], although based on data suggesting an improved late neurological outcome other centers have changed their hypothermia protocol to pH-stat strategy [12,15].

It is well known that a longer duration of CPB will result in a greater aggregation of its deleterious effects, almost all of which are time related in their degree and severity. For both simple and complex TGA patients, we found a 30% decrease of CPB time using the moderate hypothermia strategy. As a consequence this was associated with better oxygenation and lung compliance at the end of the operation and shorter time to extubation. Despite shorter rewarming and reperfusion times, the total ultrafiltration rate was significantly higher in moderate hypothermia indicating better volume state and less fluid accumulation. Such a finding may be secondary to a decreased systemic inflammatory response and decreased capillary permeability. This might be potentially beneficial as it is well known that intraoperative ultrafiltration is an effective measure to reduce a variety of inflammatory mediators and the amount of hemofiltration might correlate with the extent of its elimination. Furthermore, in an experimental study moderate hypothermia of 28 °C was superior to normothermia and deep hypothermia in suppressing TNF-{alpha} levels and stimulating interleukin-10 synthesis [20].

Surprisingly we found a significantly shorter cross-clamp time for patients operated under moderate hypothermia as a consistent finding throughout the study. One possible explanation is that surgery performed under the less proven concept of moderate hypothermia induced more pressure on the surgical team to keep ischemia time as short as possible.

Advocates of deep hypothermic bypass emphasize that deep hypothermia probably contributes importantly to myocardial protection in the neonate. However comparative measurements of cardiac enzymes or cardiac troponin under different temperature strategies were rarely performed [10,16]. Pouard and co-workers found significantly higher cardiac troponin I levels during the postoperative time course during moderate hypothermic ASO of 23–25 °C when compared to normothermic CPB with warm blood cardioplegia administration [10]. Taking inotropic support as a surrogate parameter for perioperative ischemia, we found that postoperative dobutamine support was slightly higher for patients operated under deep hypothermia which might also be explained by the longer cross-clamp time in the deep hypothermic group. However, we were unable to demonstrate any disadvantages concerning perioperative myocardial protection during moderate hypothermia.

Delayed sternal closure rate was high in our series (50%) when compared to those reported in the literature (between 10% and 25%) [10,21,22] because of our liberal application of this technique. Sternum closure was possible on postoperative day 1 in the vast majority of those patients. However, it is important to note that the same operative team operated on both groups of patients and applied the same liberal criteria for delayed sternal closure (see above). Therefore we feel our observation of an increased rate of delayed sternal closure in the deep hypothermic group is valid and may also be one reason for prolonged inotropic support, time to extubation and drainage treatment time.

Excellent hemodynamic long-term results of the ASO have shifted attention from survival to morbidity and neurodevelopmental outcome. Comparing moderate versus deep hypothermia, we found no significant difference in postoperative clinical seizure rate and only a trend towards a higher incidence of intracerebral bleeding in deep hypothermic patients. By routine clinical long-term assessment we found no neurological sequelae in all but one patient, indicating that both temperature strategies were comparably safe in the long term.

The univariate analysis of 19 perioperative adverse events revealed that perioperative morbidity was reduced in patients operated on under moderate hypothermia. As a direct consequence, ICU and hospital stays equivalent to resource utilization were shorter in these patients. This can be related to findings from the Boston group who could show that length of hospital stay after ASO was related to cognitive outcome at 8 years of age due to several reasons [23]. However, length of ICU and hospital stay varies markedly between hospitals and between medical systems in different countries. Beside less resource utilization in our study shorter hospital stay was not associated with advanced patient long-term outcome.

In a multi-institutional analysis, right ventricular outflow tract obstruction (RVOTO) was the main reason for reintervention after ASO, occurring in 12% of patients after 5 years and 1% per year after 2 years [24]. In our study overall freedom from RVOTO reoperation was 96.7% after 1 and 94.9% after 5 and 8 years. However, patients operated under moderate hypothermia had no reoperations for RVOTO thus far.

There are some limitations of the present study. First, it is non-randomized and therefore subject to all of the inherent limitations of retrospective studies. However, the strength of the present study is that surgical strategies (and surgeons) as well as perioperative protocols, e.g. indication for delayed sternal closure, respiratory weaning, and inotropic regime, were constant throughout the study period allowing us to focus on the two different temperature strategies. Although we found no statistically significant selection bias for using deep or moderate hypothermia by propensity analysis, we cannot totally exclude selection bias. Another limitation is that early and late neurological status was assessed by routine clinical means only. An accurate evaluation of late intellectual, cognitive and psychomotoric development using specific test instruments was not part of the current analysis.


   5. Conclusion
Top
 Abstract
 1. Introduction
 2. Material and methods
 3. Results
 4. Discussion
 5. Conclusion
References
 
The arterial switch operation using temperature-corrected full-flow moderate compared to deep hypothermia was advantageous regarding length of procedure time and primary chest closure rate. In addition, moderate hypothermia seemed to be beneficial for pulmonary recovery, length of chest tube drainage treatment and inotropic support and was consequently associated with lower length of ICU and hospital stay and decreased resource utilization. We found no worse early or long-term effects of moderate hypothermia. The decision regarding the specific temperature to be used for a particular patient as well as the chosen flow rate must include multiple patient and repair factors. In our opinion, however, the ASO under moderate hypothermia is a safe and cost-effective alternative to deep hypothermia even in complex TGA anatomy.


   References
Top
 Abstract
 1. Introduction
 2. Material and methods
 3. Results
 4. Discussion
 5. Conclusion
 References
 

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