INTRODUCTION
Congenital diaphragmatic hernia (CDH) is one of the important causes of respiratory distress in a newborn with an estimated incidence of 1 in 2000–5000 births.[1] Multiple factors including the gestational age at diagnosis, level of prematurity, weight, laterality, degree of pulmonary hypoplasia and pulmonary hypertension influence the outcome.[1]
With a better understanding of the pathophysiology of the disease, numerous advances have been made in the diagnosis and treatment of this problem. Better medical management of pulmonary hypertension, in utero management, better ventilation strategies, use of extracorporeal membrane oxygenation (ECMO), minimally invasive surgical techniques and overall improvement in neonatal care have improved the overall survival in these patients.[2]
Despite all these advances, the mortality rates are high ranging from 30% to 60% for isolated CDHs and as high as 89% when they are associated with additional structural or chromosomal anomalies.[3,4] To further reduce mortality, it is essential to understand the factors responsible for increased mortality in neonates with CDH/eventration. Hence, a study was conducted to evaluate the factors contributing to the mortality of neonates treated for CDH or the eventration of diaphragm.
MATERIALS AND METHODS
A retrospective study was conducted in the department of paediatric surgery in a tertiary care referral centre from March 2013 to March 2021. Ethical approval was obtained by Institute Ethics Committee (No. PS/147/2021-22). The data were collected using electronic medical records. All the neonates admitted to the department with a diagnosis of CDH/eventration during the study were included. Neonates operated for CDH/eventration in other hospitals and were referred to our department for further care were excluded. Neonates with eventration who did not require surgical intervention in the neonatal period were also excluded from the study.
The deliveries happening in the maternity wing (adjacent building) were considered inborn. Referrals from other hospitals were considered outborn. Those neonates who were inborn and antenatally detected were electively intubated at birth. Neonates who were not antenatally detected and neonates who were referred from outside with respiratory distress were intubated after the diagnosis based on the clinical status. The majority of the inborn deliveries were attended by the paediatric surgical team in the earlier part of the study (2013–2016). In the latter half of the study period, neonates were initially managed by the neonatology team and were later transferred to our department for further surgical care.
Our institute is not equipped with ECMO. Furthermore, we did not have a portable echocardiography machine till recently (2 years). Due to this, the decision on starting drugs for pulmonary hypertension was decided clinically based on pre-ductal and post-ductal oxygen saturation levels. Sildenafil was started when the difference between the pre-ductal and post-ductal saturation was ≥8%.[5] In neonates who had a two-dimensional (2D)-Echo cardiography report, pulmonary hypertension was classified as mild if the pulmonary artery pressure (PAP) was <2/3rd systemic systolic pressure, moderate if PAP was ≥2/3rd systemic systolic pressure, and severe if PAP was more than the systemic systolic pressure.[5] Sildenafil was administered in neonates when the pulmonary hypertension was moderate to severe.[6] Sildenafil was not administered to neonates with severe hypotension (MAP <5 mm Hg below the 10th centile).
Medical records of all included neonates were analysed from the hospital registry. Various parameters such as demographic characteristics, gestational age, associated anomalies, time at presentation following birth, need for pre-operative ventilation, type of surgery performed, cardiac status, postoperative complications, sepsis and mortality were documented.
Statistical analysis
Statistical analysis was performed using IBM SPSS Statistics for Windows, Version 22.0. Armonk, NY, USA: IBM Corp. The continuous variables were expressed as mean ± standard deviation or median (range) while the categorical variables were expressed as number and percentage. Patient characteristics were compared using the independent sample t-test or Mann–Whitney U-test for continuous variables and the Chi-square or Fisher’s exact test for categorical variables. A P < 0.05 was considered statistically significant. Multinominal Logistic regression analysis was done for independent factor association.
RESULTS
A total of 129 neonates with CDH/eventration were considered for the study. Six neonates with diaphragmatic eventration were excluded as they did not require surgery in the neonatal period. The remaining 123 neonates were included in the study, out of which 107 (87%) had CDH and 16 (13%) had eventration. One hundred and nine (89%) neonates had a left-sided anomaly while 14 (11%) had a defect on the right side. Seventy-three (59%) neonates were male and 50 (41%) were female. Ninety-five (77%) neonates were delivered inborn and 28 (23%) were outborn. There were 10 (8%) preterm neonates (<37 weeks’ gestation).
The mean weight of the neonates was 2.51 ± 0.42 kg. The mean and median age at admission to our hospital was 3.2 ± 5.1 days and 1 day (range: 1–28 days), respectively. Eight (7%) neonates had associated anomalies. Of them, two had undescended testis and one child had bilateral renal pelviectasis. Another child had a small left kidney. One child had left hydronephrosis. One child had associated malrotation and needed corrective surgery. One child had cutis laxa. Another child who presented at 23 days of life had hypotonia of all 4 limbs with dorsiflexed bilateral feet.
Twenty-two (18%) neonates had central cyanosis at presentation. Seventy-one (58%) neonates had respiratory distress with chest retractions at presentation. Sixty-one (50%) neonates had an antenatal diagnosis of CDH. The majority of them were diagnosed in the 5th month of gestation. Since the portable 2D-echo machine was recently procured, we were able to perform the echocardiography only in 36 neonates and 16 (44%) of them had moderate-to-severe pulmonary hypertension. Among the remaining 87 neonates who did not undergo echocardiography, 67 had clinical evidence of moderate-to-severe pulmonary hypertension. Hence, a total of 83 (68%) had moderate to severe pulmonary hypertension. Forty-five (54%) out of these 83 neonates were given sildenafil while the remaining 38 had hypotension, hence, were not given Sildenafil. Sixty-three (76%) of these 83 succumbed while the remaining were successfully discharged home.
Out of 123 neonates, 79 (64%) neonates were taken up for surgery after pre-operative stabilisation (65 neonates with CDH and 14 neonates with eventration). The remaining 44 (36%) neonates died preoperatively. Of the 79 children, 70 (89%) children were operated by open laparotomy, two (3%) by open thoracotomy for eventration, and the remaining seven (9%) children by thoracoscopic repair. Small bowel and spleen were contents in all 65 neonates with CDH while large bowel was seen in 61 neonates, and liver in 13 neonates with CDH. The mean age at surgery was 5.9 ± 5.6 days (median: 4 days).
Intraoperatively, all CDH neonates had a posterolateral defect. Fourteen (22%) neonates with CDH had an associated sac. Two children had adhesive intestinal obstruction during follow-up requiring laparotomy and adhesiolysis. Of the seven neonates who underwent thoracoscopic repair, one neonate developed an eventration (asymptomatic) and another neonate had a recurrence which was later corrected by open laparotomy. One neonate operated for right eventration had a recurrence and was re-operated (laparotomy). The average hospital stay was 11.7 ± 6.8 days and the average postoperative stay was 9.6 ± 6.5 days.
The overall mortality rate in our series was 64% (79/123). Forty-four (56%) neonates died preoperatively and 35 (44%) neonates died postoperatively. The main causes of mortality in postoperative patients were persistent pulmonary hypertension (16 neonates; 46%) and sepsis (13 neonates; 37%). Other causes included persistent refractory shock (cardiac in origin; 4 neonates; 11%), and aspiration pneumonia (2 neonates; 6%). Pre-operative mortality was mainly due to severe pulmonary hypertension and/or severe pulmonary hypoplasia.
The variables, earlier median age at presentation (1 [1–23] vs. 3 [1–28]; P < 0.001; Mann–Whitney U test), preterm birth (10/79 vs. 0/44; P = 0.01; Fischer’s exact test), inborn (68/79 vs. 27/44; P = 0.002; Chi-square test), weight ≤2 kg (18/79 vs. 1/44; P = 0.003; Chi-square test), central cyanosis at presentation (21/79 vs. 1/44; P < 0.001; Chi-square test), antenatal detection (47/79 vs. 14/44; P = 0.003; Chi-square test) and earlier mean age at surgery (3.66 ± 1.47 vs. 7.66 ± 6.88; P < 0.001; independent sample t-test) were associated with increased mortality. The variables, laterality, sex, mean weight, time at surgery <24 h, time at surgery <48 h and presence of sac had no influence on mortality [Table 1]. Six (10%) neonates operated for left CDH in our series had liver herniation and was associated with 100% mortality but it was not statistically significant (6/6 vs. 63/94; P = 0.17; Fischer’s exact test).
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Table 1: Factors affecting the mortality in neonates with congenital diaphragmatic hernia/eventration
On multinominal logistic regression analysis, the factors, preterm (odd’s ratio [OR] =4.735; P = 0.03), weight ≤2 kg [OR = 5.081; P = 0.02], central cyanosis at presentation (OR = 6.969; P = 0.008) and antenatal detection (OR = 7.471; P = 0.006) were found to be independently associated with increased mortality in CDH/eventration. The mortality trend in the last 5 years is improving (62% between 2017 and 2021 and 71% between 2013 and 2016) compared to previous years.
DISCUSSION
CDH is one of the important causes of respiratory distress in newborns. Despite many advances in the detection and management of the problem, the mortality rates are still high ranging from 30% to 60%.[3] Severe pulmonary hypoplasia, associated chromosomal anomalies, earlier gestational age at diagnosis, prematurity, low APGAR score in the immediate postnatal period and early surgery without proper pre-operative stabilisation are some of the known factors associated with increased mortality in neonates with CDH.[3,4] In this article, we have analysed the factors contributing to the mortality of neonates being treated for CDH/eventration at our institute.
Although the majority of the eventrations are asymptomatic/mildly symptomatic at birth, neonates with severe respiratory distress or requiring ventilatory support need management similar to CDH.[7] Hence, we have included eventrations requiring surgery in the neonatal period in our study group.
The high rate of pre-operative deaths in our series was due to severe pulmonary hypoplasia and/or pulmonary hypertension. Furthermore, the non-availability of high-frequency oscillatory ventilation (HFOV) in the earlier part of the study period, portable echocardiography machine, and ECMO could have contributed to the same.
Mortality rates were almost equal in both the sex groups. Similar to other studies, we had a higher incidence of left-sided CDH/eventration than the right side.[8,9] In our series, the laterality of the disease had no influence on mortality. A large French national cohort study by Pinton et al.[10] also concluded that right CDH does not have a higher risk of mortality than the left side. Abramov et al.[11] compared the outcomes in children with right and left CDH and found no statistical difference in mortality, use of ECMO, or pulmonary complications. They found right CDH children had larger defects and more often needed a patch or muscle flap repair. In our series, we did not require any patch or muscle flap repair.
In our series, we found the mortality in term infants to be much lower than in preterm infants. Oh et al. observed in their series that neonates with gestational age <25 weeks had a poor prognosis.[12] Low birth weight and overall immaturity of the lungs and other organs predispose them to higher morbidity and mortality.
We found that the inborn neonates had a higher mortality rate when compared with outborn neonates. This probably reflects the better lung compliance in children who are stable enough to be shifted from other peripheral hospitals to our centre.
We also found that neonates who presented with central cyanosis had an increased rate of mortality when compared with neonates who did not. This probably reflects severe pulmonary hypoplasia in such children. The neonates with an antenatal diagnosis of CDH/eventration had increased mortality in comparison to the neonates who were not diagnosed antenatally. This may indicate a late-onset defect with better lung development. The results were in coherence with the series by Burgos et al.[13] who compared the outcomes between prenatally and postnatally diagnosed CDH. They observed that prenatally diagnosed CDH was associated with larger defects and consequently had higher morbidity and mortality.
The incidence of sac in neonates with CDH was 22% in our series. Aydin et al.[2] found in their series that the presence of the hernia sac was associated with better outcomes. Bouchghoul et al.[14] found that the presence of the hernia sac was associated with better outcomes, especially survival at 6 months. We found no difference in the mortality rate amongst the neonates with sac against the neonates without sac.
In our series, we had 8 children with associated anomalies. However, this did not have any influence on the mortality as 75% of the children were discharged even with significant anomalies (malrotation, chylous ascites and generalised hypotonia). Aydin et al.[2] had similar results in their series. Six (10%) neonates operated for left CDH in our series had liver herniation and was associated with 100% mortality but it was not statistically significant. A review article by Cordier et al.,[15] found that the observed/expected lung head ratio of <25% was associated with severe lung hypoplasia and had a survival rate of <5%.
With respect to the surgical technique, laparotomy with the open repair was the standard technique followed. Recently, we started doing a thoracoscopic repair in stable neonates with weight >2.5 kg. Seven neonates (6 CDH and 1 eventration) were operated thoracoscopically. In the learning curve, we had our share of complications. A child with CDH had a recurrence and was re-operated (laparotomy). One child developed a secondary eventration, but was asymptomatic, on follow-up. The remaining neonates are thriving well on follow-up. We did not have any mortality in neonates operated thoracoscopically. With better experience, more neonates can be operated thoracoscopically in the future.
Furthermore, the overall mortality trend in the last 5 years is improving (62%) compared to previous years (71%). This may be due to improvisation in overall care, better neonatal management, availability of HFOV, better cardiovascular assessment, minimally invasive surgical techniques and good teamwork with our neonatology team.
CONCLUSION
Prematurity, weight <2 kg, cyanosis at presentation and antenatally detected CDH/eventration were independently associated with increased mortality. The presence/absence of the sac and associated anomalies did not influence the overall mortality.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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