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Ann Thorac Surg 2001;71:1553-1555
© 2001 The Society of Thoracic Surgeons
a Department of Cardiothoracic Surgery, Freeman Hospital, Newcastle upon Tyne, United Kingdom
Accepted for publication December 14, 2000.
* Address reprint requests to Dr Hamilton, Department of Cardiothoracic Surgery, Freeman Hospital, High Heaton, Newcastle upon Tyne, NE7 7DN, United Kingdom (Email: leslie.hamilton{at}tfh.nuth.northy.nhs.uk).
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Abstract |
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Methods. A retrospective statistical analysis was performed on 52 neonates operated on from 1991 to 1998. Until 1994, chest closure was routinely attempted in all patients after arterial switch; the policy was then changed to delayed sternal closure in all cases in the latter half of the study period.
Results. Delayed sternal closure did not significantly alter the mean duration of ventilation (2.7 ± 2.37 versus 2.7 ± 1.3 days) nor intensive care stay (4.1 ± 2.8 versus 5.7 ± 10.0 days; p = 0.46). There was no increase in the incidence of wound sepsis (7.7% versus 3.8%; p = 0.55), and mortality was unchanged (7.7% in both groups). There was an increase in the incidence of urgent reexploration (7.7% versus 19.2%; p = 0.22), which did not reach significance.
Conclusions. This study does not support the hypothesis that elective delayed sternal closure reduces the morbidity after arterial switch in neonates but does, however, confirm the safety and efficacy of the procedure.
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Introduction |
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In the setting of the literature demonstrating the usefulness of DSC with an associated low morbidity, we retrospectively analyzed all neonatal arterial switch procedures, to assess whether the introduction of a policy of elective DSC reduces morbidity and mortality associated with this procedure, as well as the need for urgent reexploration.
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Material and methods |
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Statistical analysis
Group demographics were compared using an unpaired Student’s t test, with assumption of equality of variance based on Levene’s test. Means and medians of the outcome measurements were compared with the Student’s t test and Mann-Whitney U test, respectively. The 
2 test and Fisher’s exact test were applied for the comparison of morbidity and mortality between the two groups. A p value of less than 0.05 was used to define significance.
Operative technique
After establishment of cardiopulmonary bypass with bicaval cannulation, the patients were cooled to 20°C. The ductus arteriosus was ligated and oversewn, and the pulmonary arteries were dissected out to the hilum on either side. After aortic cross-clamping, myocardial protection was achieved with intermittent antegrade cold-blood cardioplegia and ice slush. The aorta was divided as high as possible, and left and right coronary arteries were reimplanted using a medially based flap technique. The le Compte maneuver was then performed, and the aortic anastomosis was completed. The septostomy defect was closed during a short period of circulatory arrest. The defects in the original aortic root were then closed using a patch of autologous pericardium (not treated with glutaraldehyde). In the earlier part of the series, a peritoneal dialysis cannula was placed in the abdominal cavity; more recently, modified ultrafiltration has been performed routinely to raise the hematocrit at the end of the procedure.
Delayed sternal closure technique
In all cases in which the sternum was not closed, the edges were splinted apart with an appropriately shaped piece of polyvinyl chloride tubing. In a small number of the earlier cases, the skin edges were approximated and sutured, but subsequently, and in the great majority of cases, the wound was sealed with a sheet of transparent silicon membrane. Routine mediastinal drains were placed and exteriorized through separate skin incisions, as were pacing wires and monitoring catheters. Drains were kept on low-pressure suction.
All patients were assessed for closure the following day. To be considered suitable for closure, they had to demonstrate hemodynamic stability, low inotropic agent requirement, satisfactory ventilatory variables, good urine output, and minimal mediastinal drainage. Closure was routinely performed by the surgical team, in the intensive care unit. If a patient was not thought to be suitable for closure, or attempted closure was unsuccessful, they were subsequently reevaluated on a 24-hourly basis. The final decision to definitively close the chest depended on the tolerance of the neonate to having the sternal edges approximated. Standard antibiotic policy was to maintain patients on flucloxacillin for antistaphylococcal cover, this was changed to a different antistaphylococcal antibiotic after closure, usually clindamycin. Lavage of the chest cavity was not routinely performed before closure.
Patient characteristics
The mean (± standard deviation) age of patients in group 1 was 15.9 ± 6.2 days and 11.6 ± 5.4 days in group 2; this reached statistical significance (Student’s t test; p < 0.05), reflecting an increasing tendency to perform the procedure earlier in life. The incidence of an associated ventricular septal defect was 19.2% (5 of 26) and 15.4% (4 of 26), respectively, with one Taussig Bing anomaly in group 1 and one case of associated dextrocardia in group 2. Comparison of intraoperative variables between the groups showed no significant differences, with mean cardiopulmonary bypass times of 167.9 ± 55.6 versus 179.9 ± 79.6 minutes (p = 0.54) and mean cross-clamp times of 85.9 ± 20.0 versus 82.4 ± 27.1 minutes (p = 0.60).
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Results |
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Of the 24 survivors, 18 cases had the chest closed in the operating room, whereas six cases had DSC (23.1%), one for ventilatory difficulties and the remainder because of cardiovascular instability. A trend for longer intubation times and intensive therapy unit (ITU) stays for the patients that underwent DSC is reflected in the mean and median intubation times and ITU stays (Table 1).
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The day of sternal closure was significantly different, because of the application of the policy itself (mean, 0.6 ± 1.2 versus 1.2 ± 0.5 days; p = 0.02; median, 0 versus 1 day; range, 0 to 4 days; p = 0.00). When other effects of the policy of elective DSC were evaluated, no significant differences appeared between the groups. The mean duration of ventilation was 2.7 days and the median, 2 days in both groups; similarly the ITU stay was essentially unchanged (mean 4.1 ± 2.8 versus 5.7 ± 10.0 days; p = 0.46; median, 3 days in both). Of note, there was no increase in the incidence of wound sepsis, with two cases in group 1 (7.7%) and only one in group 2, despite all having DSC with definitive closure routinely performed in the intensive care unit. The one wound infection in group 2 did, however, exhibit wound dehiscence and subsequent mediastinitis, to which he succumbed 51 days postoperatively. This case had a resistant metabolic acidosis at the end of the procedure, but was able to undergo chest closure on the first postoperative day.
Two patients (7.7%) in group 1 required urgent reexploration postoperatively, as opposed to five cases (19.2%) in group 2, but the difference did not reach statistical significance (p = 0.22).
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Comment |
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It has been suggested that DSC can prevent the development of low cardiac output [4], and some have suggested its use when low cardiac output states may be anticipated [3]. To our knowledge, this is the first trial of the procedure when applied to all patients in a particular group, irrespective of the findings at the end of the procedure. Using the relatively crude measures of morbidity, such as need for reexploration or duration of intubation or ITU stay, we were unable to demonstrate any benefit from such a policy in this group of neonates. Although more sensitive measures of the clinical course, such as inotropic agent requirements or regular cardiac output measurements, may have given greater insight into any potential physiologic benefits, we believe that these would be insufficient to warrant the continued application of this as a routine policy. However, we have demonstrated that it can be used in this setting without any increase in ITU stay or ventilatory requirements, with no increase in wound sepsis and no cases of late sternal instability. The low incidence of wound sepsis is not entirely surprising—a review of the literature reveals that the incidence of wound infection after DSC is generally less than 10% [5, 6]. Furthermore, this is when the procedure is applied to the sickest group of patients, and rates when the procedure is used electively should be theoretically lower. It should be borne in mind that most studies of DSC have evaluated children of all age groups, and younger infants may well be at a higher risk of septic complications. One study has described a higher incidence of wound infections in younger patients that have undergone DSC [6].
The slightly higher incidence of urgent reexploration in the DSC group was surprising, although it did not reach statistical significance. When the indications for reexploration were further evaluated, the two cases in group 1 were both typical tamponade; ischemic thymus was excised in one case and clots evacuated in the other. In the second group, one case was reopened to control excessive hemorrhage and another in response to a high left atrial pressure with subsequent evacuation of clots from the mediastinal cavity. The indication for reexploration in the remaining three cases was a prolonged period of hypotension after endotracheal suction, and no further action was required in these cases. This may suggest a lowering of the threshold for reexploration, perhaps because of the increased accessibility of the mediastinal structures, and could be regarded as further justification for the preemptive use of DSC in high-risk cases, in which there is a significant risk of the development of low cardiac output.
An inherent limitation of this study is that it was not applied in a randomized manner and, as such, is essentially retrospective. However, as an audit of a policy change and in the absence of significant other changes in the care of these neonates, it has a significant value. Another potential criticism is the introduction of the routine use of modified ultrafiltration during the study period instead of the previously used peritoneal dialysis cannula. As well as raising the hematocrit, this is also thought to reduce myocardial edema. This would, however, have skewed the results in favor of the newer policy and thus is unlikely to have influenced our final interpretation or conclusions.
In conclusion, this study failed to demonstrate that a policy of routine, elective DSC conferred any quantifiable benefits after neonatal arterial switch. However, it was associated with no increase in morbidity—notably from wound sepsis—and did not have an adverse effect on the duration of intubation or stay in intensive care. Thus it further adds to the growing body of evidence that DSC is a safe procedure in this group, and can justify a low threshold for its application.
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