Pre-term Infants in Major Abdominal Surgery and Postoperative Outcome

Background: A monocentric observational study was undertaken in pediatric surgical patients in neurosurgery, abdominal and orthopedic surgery to determine predictors of postoperative outcome. In this cohort of 594 patients with a mean age of 90.86±71.80 months there were 25 pre-terms aged less than 37 weeks. A description of postoperative outcome was undertaken in these pre-term infants. Objective: The objective of this study was to describe the characteristics in pre-term patients in this initial cohort. Methods: Secondary analysis of pre-term patients included in the initial retrospective observational study. The Ethics Committee approved the study. Results: 25 pre-terms aged <37 weeks were included with a mean weight of 2.43±0.75 kg in major neonatal abdominal surgery. 9 patient presented postoperative complications among which 1 had an intra-operative cardiac arrest, 4 had postoperative respiratory failure, 2 had pulmonary sepsis, 1 had surgical wound sepsis, 1 had septicemia and 1 had multi-organ sepsis. Conclusion: In this cohort of 25 critically ill pre-terms in major neonatal abdominal surgery, the most common postoperative complications concerned the respiratory system which included respiratory failure and pulmonary sepsis. There was no in-hospital mortality.


Introduction
In 2017, a monocentric observational retrospective study was undertaken in pediatric surgical patients in neurosurgery, abdominal and orthopedic surgery to determine predictors of postoperative outcome (1). In this cohort of 594 patients with a mean age of 90.86±71.80 months, there were 25 pre-term infants aged less than 37 weeks. These were all admitted in the neonatal intensive care unit (NICU) and were scheduled for emergency and elective surgery. These pre-term patients were described in detail in this manuscript. The objective of this study was to describe the characteristics and postoperative outcome in these pre-term infants in this cohort.

Methods
Secondary analysis and description of pre-term patients included in the initial retrospective observational study from 1 January 2014 to 17  Inclusion criteria were patients aged less than 37 weeks included in the initial study.
Exclusion criteria were patients aged more than 37 weeks included in the initial study.
Statistics were analyzed with XLSTAT 2020.4.1 software.
Continuous variables were described in means with standard deviation or in medians with interquartile range. Categoric variables were described in proportions. Categoric variables were compared with Fischer's exact test.

Results:
General characteristics are illustrated in Table 1.  19 patients underwent emergency surgery and 6 underwent elective surgery.
1 patient had a congenital heart disease and 1 had a right atrium thrombus.
4 patients had re-operations.
There was no in-hospital mortality.
All were admitted in the NICU, 22 patients were under mechanical ventilation postoperatively and 3 did not require postoperative mechanical ventilation.

Discussion
The rate of patients with postoperative complications in this cohort is comparable to what has been reported in neonatal infants in abdominal major surgery (2,3,4,5). There was no signi cant difference in complication rates among different types of surgery. One patient presented intraoperative cardiac arrest with favorable outcome which represented 4% of the complications. The incidence of intra-operative cardiac arrest was 0.12% according to a recent study in a cohort of 5609 infants aged up to 60 weeks among which 35.7% were pre-terms (6). According to this same study, the rate of patients with intra-operative critical events was 35.5% among which the majority were commonly due to cardiovascular instability followed by hypoxemia; 16.3% of the patients had one or several postoperative critical events (6). In our study, intra-operative critical events concerned one patient who presented intra-operative cardiac arrest representing 4% of the patients. The rate of patients with postoperative complications until discharge from hospital was 36% in our cohort.
Our study of 25 pre-terms in major abdominal surgery revealed that the most common postoperative complications concerned the respiratory system which included respiratory failure and pulmonary sepsis with an overall rate of 24%. According to previous studies in 198 infants with esophageal atresia and 44 pre-terms with gastroschisis, the rate of postoperative respiratory dysfunction varied between 11% and 52.8% (2,3). The second common postoperative complication in our cohort was re-operation (16%) followed by surgical wound sepsis (4%), septicemia (4%) and multi-organ sepsis (4%). Re-surgery rates varied from 5 to 11.7 % according to one study in 3479 infants with esophageal atresia (4). Sepsis after major surgery such as esophageal atresia has been reported to vary between 3.1-19.4% (2). In this cohort, the overall sepsis rate was 20% with pulmonary sepsis being the most common with a rate of 8%. The incidence of early onset sepsis (appearing after less than 3 days of life) in pre-terms varied from 0.5 to 2.5% according to one study (7) and the rate of late onset sepsis (appearing after 3 days of life) in pre-terms varied from 11-32% (8,9). Neonatal sepsis is a major etiology of morbi-mortality in pre-terms (7,8). Mortality rates due to sepsis in pre-terms can reach 20-30% (10). In our cohort, there was no mortality. Mortality rates reported in the literature in pre-terms scheduled for major neonatal abdominal surgery such as necrotizing enterocolitis, esophageal atresia, gastroschisis and omphalocele varied between 3.4 and 34 % (2,3,5,11,12,13,14). According to a study in 75 neonates with abdominal wall defects, mortality was higher in patients with associated congenital heart diseases and chromosomic disorders (14). In another study of 1554 premature infants in emergency abdominal operations, female gender, inotropic support, mechanical ventilation and ASA score III were predictors of 30 days mortality (15).
In a study of 566 neonates with gastroschisis, the presence of a complex laparoschisis, pre-term age of < 37 weeks, very low birth weight of < 1500 grams were factors predicting morbi-mortality (16).
According to the multicentric Nectarine study, overall mortality rate was 3.2%, with a 30-day mortality rate in neonates of 4.1% with sepsis and multi-organ failure being major causes of mortality in this subgroup (6). The Nectarine study which included patients aged up to 60 weeks admitted for different surgical interventions revealed that age, critical events including hypotension, hypoxemia and anemia were predictive of adverse outcome illustrated by morbi-mortality (6). In our pre-term cohort, none of the patients were anemic and none received transfusion. Our initial monocentric retrospective study of 594 patients admitted for neurosurgery, abdominal and orthopedic surgery with a mean age of 90.86±71.80 months from which this pre-term cohort sample was extracted evidenced that the general patient's status, precisely the ASA (American Society of Anesthesiologists) scores III, IV and V were predictive of mortality (1). All pre-term infants in this cohort were ASA III or IV. This retrospective study revealed also that ASA score III or more, transfusion, emergency situations, age and the type of surgery were predictive of postoperative what has been reported in the literature (13). In a study of 442 neonates with gastroschisis of more than 34 weeks of age (17), median LOS was higher in patients with staged closure than in primary closure, implying that LOS is a variable which depends on other factors. In our retrospective study, LOS was predicted by ASA score, transfusion, emergency and the type of surgery (1).
The results of our initial pediatric retrospective study (1), the results of the Nectarine study (6) and the results of previous studies in similar neonatal population (14,15,16,17) con rm that outcome in the surgical pediatric population is multifactorial. Identifying these multiple predictors of adverse evolution and applying preventive and improvement measures on each of them can optimize postoperative outcome in children. A meta-analysis in 3290 children aged less than 18 years old evidenced that mortality, organ dysfunction and LOS were lower in children who had optimal intraoperative or postoperative values of regional oxygen saturation, mixed central venous oxygen saturation and lactate levels (18). Regional oxygen saturation, mixed central venous oxygen saturation and lactate levels re ect tissular perfusion and alterations of these parameters can indicate tissular perfusion impairment which can cause organ dysfunction.
The results of this study con rm that the rate of postoperative complications in critically ill pre-term infants in major abdominal surgery remains high as reported by previous studies. This emphasizes optimizing intra-operative uid and hemodynamic status to improve postoperative evolution in highrisk patients. However other factors which predict postoperative adverse outcome should be taken into account to improve outcome and intra-operative optimization is one among these predictors.
The limit of our study was the sample size.
The strength of our study was the homogeneity of the sample which included critically ill pre-term infants in major abdominal surgery thus a high-risk population.

Conclusion
In this study of 25 critically ill pre-term infants admitted in NICU after abdominal major surgery, the most common postoperative complications concerned the respiratory system which included respiratory failure and pulmonary sepsis; followed by re-surgery, wound sepsis, septicemia and multi-organ sepsis. There was no in-hospital mortality. Maintaining adequate tissular perfusion is necessary for optimal outcome in surgical pediatric patients. This aim can be achieved by intra-operative uid and hemodynamic optimization by using means to monitor adequate tissular perfusion. These means should be adapted according to the context which includes patient status, age and surgery.