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The complications of repeat median sternotomy in paediatrics: six-months follow-up of consecutive cases
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     Department of Cardiothoracic Surgery, Glenfield Hospital, Groby Road, Leicester LE3 9QP, UK

    Presented at the Scientific Exhibition from 11–14th October 2004 at the 90th Clinical Congress of the American College of Surgeons in New Orleans, Louisiana, USA.

    Abstract

    Repeat median sternotomy in paediatrics though associated with increased perioperative risks, yet the incidence of injury to the underlying structures during sternal re-entry is poorly quantified. We reviewed 108 patients undergoing repeat sternotomies (group-I) and a control group of 516 patients undergoing first time sternotomy (group-II) over six years with six-months follow-up. Overall mean age was 17 months (range 1 day–16 years). Uncontrollable bleeding was encountered in 4 patients (3.7%), non-fatal cardiac laceration in 10 (9.2%), minor injuries to aorta in 7 (6.4%) and right atrium in 8 (7.4%) in Group-I. Forty-one times (38%) pericardial sac was closed and 55 times (51%) artificial materials (Dacron/Gortex) were used in initial procedures. The incidence of injuries during sternal re-entry was significantly lower in those patients where pericardial sac was closed initially (P<0.001). Hospital mortality was 3.7% in Group-1 and 2.7% in Group-II, however, overall survival was 95% (group-I) and 97% (group-II) at 6 months' follow-up. Complete heart block, neurological problems and persistence of shunts being the most common reported morbidities in both groups. In conclusion, low incidence of morbidity and mortality in repeat median sternotomy is possible with careful surgical approach. The closure of pericardial sac in initial procedure provides many potential and practical advantages with regard to lesser trauma to underlying structures.

    Key Words: Coronary artery bypass surgery; Sternotomy; Femoro-femoral bypass; Valve procedure

    1. Introduction

    With advances in paediatric cardiac surgery, staged procedures and bioprosthetic conduits to repair complex forms of congenital heart disease are not only used more frequently, but also at a younger age. The survival has markedly improved in the last 15 years [1], therefore an increasing number of patients will require repeat median sternotomy during childhood. Although the approach has facilitated access to the heart and great vessels, repeat median sternotomy represents 8–25% of cardiac surgical procedures and are attended by specific technical problems with increased perioperative mortality and morbidity [1,2]. Moreover, the information about the incidence of injury to the heart and mediastinal structures during sternal re-entry is scarce and has been poorly quantified in paediatric population.

    This study reviews our experience with a paediatric cardiac population undergoing repeat sternotomy for residual defects or staged repairs, assessing perioperative mortality and morbidity in comparison to a control group with six-months follow-up.

    2. Material and methods

    2.1. Patients

    We reviewed 108 patients undergoing repeat sternotomies (Group-I) and a control group of 516 patients undergoing first time sternotomy (Group-II) between January 1997 and January 2003 with six-months follow-up. There were 68 (63%) and 237 (46%) males in Groups-I and II, respectively. Reoperations included valve procedure in 34, Fontan procedure in 35, ventricular septal defect closure in 31 (25 residual and 6 previously unrepaired), and miscellaneous in 8. The median age and weight at second operation were 56.5 months (range, 3–228 months) and 16.3 kg (range, 4.1–94.5 kg), respectively. The surgical procedures entailed in Group-II were bidirectional Glenn in 75 patients, atrioventricular septal defect closure in 134, tetralogy of Fallot repair in 121, valve procedure in 115, repair of transposition of the great arteries in 60 and miscellaneous in 11. The median age and weight at initial operation were 17 months (range, 1 day–16 years) and 8.3 kg (range, 2.2–61.4 kg), respectively. Primary Diagnoses are summarised in Table 1.

    2.2. Surgical procedures

    Patients in Group-I and all patients in Group-II underwent operations with moderate hypothermia and cardioplegic arrest. Only repair of atrial septal defects was done under normothermia. Deep hypothermia and circulatory arrest was used only in repair of total anomalous pulmonary venous return and for complex re-entry to pericardial cavity. All operations were done through a sternotomy approach with cannulation of both venae cavae and the ascending aorta. Femorofemoral bypass before repeat sternotomy was used in 25 patients of Group-I. Our criteria for femorofemoral bypass were conduits located directly underneath the sternum, lack of retrosternal space, low body weight, difficult access to the femoral vessels and surgeon's decision.

    2.3. Statistical analysis

    Data were expressed as median and range for all descriptive variables. The Wilcoxon rank-sum test was used to test for equality of the median values and Fisher's exact test was used for the comparison of percentages. Actuarial data for survival were analysed using Kaplan–Meier estimates. A value of P<0.05 was taken as significant.

    3. Results

    3.1. Hospital mortality

    The hospital mortality was 3.7% in Group-1 and 2.7% in Group-II. The most common cause of death was low output syndrome secondary to ventricular dysfunction.

    3.2. Early morbidity

    Cardiac lacerations at repeat sternotomy occurred in 10 of 108 operations (9.2%). None of these patients sustained severe hypotension or cardiac arrest. Among 4 patients, bleeding was controlled without the institution of any emergent femorofemoral bypass. Minor injuries were encountered to aorta in 7 (6.4%), right atrium in 8 (7.4%), laceration to the bioprosthetic conduit in 5 (4.6%) and right ventricle in 2 (1.8%). Severe air embolism was suspected in 2 patients with univentricular hearts because of laceration of the right atrium allowing air entry to the common atrial chamber. Neither of these patients sustained cerebral damage as confirmed by clinical examination and a head computed tomographic scan. They had successful surgical repair. The median age of patients where femorofemoral bypass was used prior to repeat sternotomy procedures was 139 months (range, 5–219 months), whereas the median age of the 10 patients who sustained cardiac lacerations was 63 months (range, 42–228 months).

    We compared Group-I (repeat sternotomy) with its own initial operation and then Group-I (repeat sternotomy) with Group II (control), analysing multiple parameters (Tables 2–3).

    3.3. Group I

    The perioperative variables of Group-I at initial operation and reoperation, including bypass and cross-clamp time, total blood loss in 24 h, blood requirement, intensive care unit length of stay (LOS) and hospital LOS, were compared (data not shown). There was no statistical difference except for blood requirement (P<0.05). It was observed that 41 (38%) times pericardial sac was closed and 55 (51%) times artificial material (Dacron/Gortex) were used in initial procedures in these patients. The incidence of injuries during sternal re-entry was significantly lower in those patients where pericardial sac was closed initially (P<0.001).

    3.4. Group II

    The median total blood loss was 21 ml/kg (range,1.3–102.8 ml/kg). The median blood requirement was 0.3 units/kg (range, 0–8.2 units/kg). The most common complications were postpericardiotomy syndrome in 11.1%, low output syndrome in 8.2%, dysrhythmia in 5.6%, sepsis in 5.3%, bleeding in 2.7%, and renal failure in 0.3%.

    3.5. Groups I and II

    When Group I was compared with Group II, the median bypass time and cross-clamp time were 102 min (range, 30–270) and 56 min (range, 11–187) in Group I, and 66 min (range, 33–111) and 25 min (range, 14–47) in Group II (P<0.05 in both cases). The median blood loss and blood requirement in groups I and II were not statistically different. The median length of stay in the intensive care unit and in the hospital was 10.2 days (range, 1–77) and 21 days (range, 1–120) in Group-1, and 4.5 days (range, 1–51) and 7 days (range, 1–67) in Group-II (P<0.05 in both cases).

    3.6. Follow-up

    Overall rate of complications was not significantly different between two groups in 6 weeks. Group I survivors were followed up for a median of 84 months (range, 4–280 months) and Group II survivors for a median of 50.5 months (range, 0.1–131 months). In Group-I there was three late sudden deaths at 6, 14, and 18 months, all caused by presumed arrhythmia. In Group-II there were two late deaths at 1.5 months caused by pericardial tamponade and at 11 months caused by superior vena cava thrombosis. Overall survival by Kaplan–Meier analysis was 95% (group-I) and 97% (group-II) at 6 months' follow-up (P>0.05) and complete heart block, neurological problems and persistence of shunts being the most common reported morbidities in both groups (P>0.05).

    4. Discussion

    The main question about reoperations is whether they have an incremental effect on operative mortality compared with primary procedures. The reported data are controversial and relate mainly to redo valve replacement [1,3], and aortocoronary bypass grafting [4] in the adult population. With advanced techniques in surgical procedures in infants and the staged repair of complex congenital heart defects, repeat sternotomies in paediatric cardiac operations are increasingly more common.

    Although some literature has shown a trend towards a higher risk at reoperation [4–6], our mortality in the paediatric repeat sternotomy group compared with the control group shows no statistical difference (3.7% vs. 2.7%). The higher risk of re-operation in the adult population has been associated with advanced New York Heart Association class. The same parallel cannot be established with our group. Most of our patients were not reoperated on the basis of deteriorating cardiac function, but rather because of conduit or valve obstruction from somatic outgrowth and planned staging in the complex heart defect group.

    Perioperative morbidity can be detrimental and recovery from reoperation may be prolonged. The incidence of postoperative complications in Group I and Group II was similar and does not support the notion of increased perioperative morbidity after repeat sternotomy. Nevertheless the LOS in the intensive care unit and in the hospital was significantly longer in Group I than in Group II (P<0.05). We would argue that this increased LOS is related to the type of operation as 45 patients underwent a second-stage Fontan procedure with a median LOS of 22 days (range, 9–125 days).

    Cardiac structures were entered 10 times at repeat sternotomy requiring emergent institution of femorofemoral bypass in 6 patients. Elective femorofemoral bypass was used in 25 patients. All lacerations were controlled and were not detrimental to the patient's outcome. We established that a calcified conduit behind the sternum and lack of retrosternal space were the main risk factors. The median age of the patients who did and did not undergo femorofemoral bypass was 139 months and 48 months, respectively. It is obvious that the majority of our patients are young children and they fall in a different group. We make every effort to defer cannulating the femoral vessels as it is difficult to obtain proper cardiopulmonary bypass flow and the vessels can be severed more easily.

    Blood product strategies have changed over the years. It is interesting to note that blood loss and blood requirements between the repeat sternotomy and the control group were not statistically different. Tranexamic acid is given to all repeat sternotomy patients before operation and is added to the prime. We are unable to explain the statistical difference in blood loss in the subgroups of Group I. However, the initial operation was done at a younger age and was undeniably more complex in many patients, increasing the risk of postoperative coagulopathy.

    Some groups maintain that repeat median sternotomy may be facilitated by certain manoeuvres at the time of the initial cardiac procedure. Cliff and associates [7] showed that both serosal injury and blood are necessary to produce cardiac adhesions. Careful handling of the heart and complete evacuation of pericardial blood may reduce postoperative adhesions. Where appropriate, approximation of the pericardium or placement of synthetic biomaterials may also facilitate re-operation. In our series, 41 times pericardial sac was closed and 55 times artificial materials (Dacron/Gortex) were used in initial procedures. The incidence of injuries during sternal re-entry was significantly lower in those patients where pericardial sac was closed initially (P<0.001).

    The survival by Kaplan–Meier analysis is similar in both groups at 120 months. A longer follow-up is required to determine long-term outcome as the combined parameters of repeat sternotomy, myocardial protection, and ventricular dysfunction may express themselves as definite risk factors.

    A significant limitation of our study relates to the fact that repeat sternotomy is only one parameter of outcome. Clinical results are more likely to depend on the complexity of the primary diagnosis and the procedure as well as the quality of the surgical repair. The longer intensive care unit and hospital LOS in Group-I exemplifies this fundamental problem.

    The main question surgeons confront is whether re-operations have an incremental effect on operative mortality compared with primary procedures. Although the literature [8,9], has shown a varied trend towards complications in the repeat sternotomy group, in our series low incidence of morbidity and mortality in repeat median sternotomy is possible with careful surgical approach. The closure of pericardial sac in initial procedure provides many potential and practical advantages with regard to lesser trauma to underlying structures. In addition, as suggested in previous studies [10,11], a lateral chest X-ray or CT scan may be useful in determining the likelihood and extent of adhesions between the heart, great vessels and the sternum.

    Acknowledgments

    The authors gratefully acknowledge the assistance of Mrs Karen Jack, Audit Planning and Performance Manager and Mrs Jo Harding, Manager Medical Records in Cardiac Surgery at the Glenfield Hospital, Leicester, United Kingdom.

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