Predictive Factors for Mortality in Pre-Term Neonates with Necrotizing Enterocolitis: A Retrospective Cohort Study

Abstract

Background:

Necrotizing enterocolitis (NEC) is a serious neonatal condition. Over the last three decades, there has been progress in neonatal intensive care with an increase in the incidence of pre-term births. This has led to an increase in the incidence of NEC. However, research studies regarding NEC outcomes in low-income countries are scarce. Our study aimed to assess predictive factors for mortality in patients with NEC in a single center in Tunisia.

Patients and Methods:

We conducted a retrospective data collection through a review of the patients' medical records. All neonates with a medical or surgical management of NEC between January 1, 2010 and March 31, 2022 were included.

Results:

A total of 102 neonates were included with the overall survival of 47%. Outcomes of the univariable analysis showed that patients in the deceased group had lower gestational age, lower five-minute Apgar score, lower birth weight, and lower platelet count than those in the survivor group. Multivariable logistic analyses demonstrated that gestational age <32 weeks (p = 0.024; odds ratio [OR], 2.5), five-minute Apgar score <8 (p = 0.017; OR, 3.621), birth weight <1,500 g (p = 0.001; OR, 4.136), platelet count <50,000/mm³ (p = 0.029; OR, 2.5), Bell's stage 3 (p = 0.035; OR, 2.496), and sepsis during hospitalization (p < 0.001; OR, 5.971) were associated with mortality in neonates with NEC.

Conclusions:

Our study showed that gestational age <32 weeks, five-minute Apgar score <8, very low birth weight, severe thrombocytopenia, Bell's stage 3, and sepsis during hospitalization were predictive factors for mortality in neonates with NEC. These factors would be useful to refine treatment modalities for better disease outcomes.

Necrotizing enterocolitis (NEC) is a serious neonatal condition.¹ The true incidence of NEC is still unknown because of the lack of robust epidemiologic data. This incidence varies from 2% to 17% in pre-term infants.² The etiopathogenesis of NEC is complex and several factors have been implicated in the pathogenesis of this condition including genetic factors, highly immune-reactive intestinal mucosa, abnormal microbial colonization, and the immaturity of the intestine.^3,4 Over the last three decades, there has been progress in neonatal intensive care with an increase in the incidence of pre-term births. This has led to an increase in the incidence of NEC.² Many therapeutic strategies, including breastfeeding, pre-natal glucocorticoid administration, and probiotic supplementation, have been developed to prevent NEC. However, this condition is still common in neonatal intensive care units.^5–8

Many researchers have studied NEC outcomes in neonates. However, the identified prognostic factors did not find a widespread use because of conflicting results.^9–11 Moreover, most of research studies on NEC outcomes are led by researchers from high-income countries; low-income countries are underrepresented.^12,13 Our study aimed to assess predictive factors for mortality in patients with NEC in a Tunisian center.

Patients and Methods

Subjects and NEC staging

We conducted a retrospective data collection through a review of patients' medical records. All neonates with a medical or surgical management of NEC between January 1, 2010 and March 31, 2022 were included. The diagnosis and staging of NEC were defined using modified Bell's staging classification. This classification is based on several criteria including systemic, intestinal, and radiographic signs, and laboratory results.¹⁴ Incomplete medical records, gestational age ≥37 weeks, and Bell's stage 1 (suspected NEC) represented the exclusion criteria from this study. This study was approved by the ethical committee of the Hedi Chaker University Hospital, Sfax, Tunisia (HCH/022/0212).

Management of NEC at our institution

In our institution, all neonates with suspected or confirmed NEC receive the same medical management. Medical treatment includes withholding feeds, parenteral nutrition, nasogastric tube placement for gut decompression, intravenous fluid resuscitation, and intravenous antibiotic agents with activity against gram-negative, gram-positive, and anaerobic bacteria. In our practice, a combination of three antibiotic agents is given in accordance with the guidelines of the Infectious Diseases Society of America and the Surgical Infection Society.¹⁵ This combination includes gentamicin, ampicillin, and metronidazole or cefotaxime, ampicillin, and metronidazole. Vancomycin is prescribed instead of ampicillin if ampicillin-resistant infections or methicillin-resistant Staphylococcus aureus are suspected.

Inotropic support and intubation may be necessary in hemodynamically unstable neonates. Thereafter, close monitoring and possible correction of electrolyte and glucose levels are ensured. Serial complete blood counts are performed to detect thrombocytopenia and anemia. Serial abdominal examinations and radiographs are performed to assess for disease progression and to detect intestinal perforation early. In our practice, oral feeding is initiated when the following three criteria are met: gastric residue <1 mL/kg per day, absence of bilious gastric residue, and presence of intestinal sounds.

Surgery is indicated in patients with pneumoperitoneum on abdominal radiograph and those with signs of clinical deterioration including worsening abdominal findings, hemodynamic instability, requirement of inotropes, and worsening laboratory values. In our institution, laparotomy is performed as the gold standard approach in patients needing surgical management. However, in high-risk neonates with birth weight <1,000 g, we insert a peritoneal drain at the bedside through a percutaneous approach as a temporizing measure to delay laparotomy. The decision to place a peritoneal drain is made by the surgeon in consultation with the anesthesiologist and the neonatologist. There were no changes in NEC management protocols during the study period.

Predictive factors for mortality

The following predictive factors were evaluated: gender, age at diagnosis, birth weight, gestational age, five-minute Apgar score, mode of delivery, white blood cell (WBC) count, platelet count, hemoglobin level, C-reactive protein (CRP) level, Bell's stage, sepsis during hospitalization, and type of treatment.

Bias

We trained and coached local investigators to minimize selection bias. We tried to include all NEC patients by using the radiograph and ultrasound databases.

Statistical analysis

We performed statistical analyses using SPSS Statistics, version 20 (IBM Corp, Armonk, NY). We used χ² tests to assess statistical differences in categorical variables between patients in the survivor and deceased groups. We used Student t-tests for continuous variables. A p value of <0.05 defined statistical significance.

Results

Baseline characteristics

In total, 146 neonates were included during the study period. Three neonates with incomplete medical records, 13 neonates with gestational age ≥37 weeks, and 28 neonates with Bell's stage 1 were excluded, leaving 102 neonates for analysis. During the coronavirus disease 2019 (COVID-19) pandemic (March 2020 to March 2022), 15 patients with NEC were admitted. Among these infants, only one was born to a mother with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection.

Our patients were divided into two groups: the deceased group included 54 (53%) neonates and the survivor group included 48 (47%) neonates. The mortality rate was almost stable during the study period. The mortality rate was 54.2% (13/24) during 2010–2012, 53.8% (14/26) during 2013–2015, 52% (13/25) during 2016–2018, and 51.8% (14/27) during 2019 through March 2022. Most of our patients were male (64.7%), with low birth weight or less (100%), five-minute Apgar score ≥8 (79.4%), Bell's stage 2 (66.7%), no sepsis during hospitalization (57.8%), and conservative management (75.5%) (Table 1).

Table 1.

Baseline Characteristics of Neonates with NEC in Our Institution

Characteristics		n (%)
Gender	Male	66 (64.7)
Gender	Female	36 (35.3)
Five-minite Apgar score	<8	21 (20.6)
Five-minite Apgar score	≥8	81 (79.4)
Birth weight (g)	Normal birth weight (≥2,500)	0 (0)
	Low birth weight (<2,500)	38 (37.2)
	Very low birth weight (<1,500)	46 (45.1)
	Extremely low birth weight (<1,000)	18 (17.7)
Platelet count (/mm³)	Thrombocytosis (>350,000)	12 (11.8)
	Normal (≥150,000–350,000)	51 (50)
	Moderate thrombocytopenia (<150,000)	17 (16.7)
	Severe thrombocytopenia	22 (21.5)
NEC staging	2A	51 (50)
	2B	17 (16.7)
	3A	13 (12.7)
	3B	21 (20.6)
Type of treatment	Conservative	77 (75.5)
Type of treatment	Operative	25 (24.5)
Sepsis during hospitalization	Yes	43 (42.2)
Sepsis during hospitalization	No	59 (57.8)
Deceased	Yes	54 (53)
Deceased	No	48 (47)

NEC = necrotizing enterocolitis.

Univariable analysis of deceased versus survivor groups

Outcomes of the univariable analysis showed that patients in the deceased group had lower gestational age, lower five-minute Apgar score, lower birth weight, and lower platelet count than those in the survivor group. There was no association between mortality and age at diagnosis, white blood cell count, C-reactive protein level, and hemoglobin level (p = 0.973, 0.950, 0.288, and 0.861, respectively; Table 2).

Table 2.

Univariable Analysis of Deceased versus Survivor Groups

	Deceased group (n = 54; 53%)	Survivor group (n = 48; 47%)	p
Gestational age (wks, d), median [IQR]	31.2 [29–32.4]	32.5 [29.6–34.6]	0.011
Five-minute Apgar score, median [IQR]	7 [5.75–8]	8 [7.25–9]	<0.001
Birth weight (g), median [IQR]	1225 [950–1450]	1500 [1300–2000]	<0.001
Age at diagnosis (d), median [IQR]	5 [3–16]	5 [3–19.5]	0.973
Platelet count^a (g/L), median [IQR]	155 [37–225]	209.5 [123.5–350.5]	<0.001
WBC count^a (g/L), median [IQR]	6.9 [3.8–15.1]	8 [3.6–15.5]	0.950
CRP^a (mg/L) , median [IQR]	21.5 [2–96]	15 [5.2–62.5]	0.288
Hb^a (g/L), median [IQR]	12.1 [9.1–15.4]	12 [10.9–14.7]	0.861

IQR = interquartile range; WBC = white blood cell; CRP = C-reactive protein; Hb = hemoglobin.

At disease presentation.

Multivariable analysis of deceased versus survivor groups

Multivariable logistic analyses demonstrated that gestational age <32 weeks (p = 0.024; odds ratio [OR], 2.5), five-minute Apgar score <8 (p = 0.017; OR, 3.621), Birth weight <1,500 g (p = 0.001; OR, 4.136), platelet count <50,000/mm³ (p = 0.029; OR, 2.5), Bell's stage 3 (p = 0.035; OR, 2.496), and sepsis during hospitalization (p < 0.001; OR, 5.971), were associated with mortality in neonates with NEC (Table 3). There was no association between mortality and surgical or conservative management. Also, we found similar outcomes for operative and non-operative treatment groups (Table 4).

Table 3.

Multivariable Analysis of Deceased versus Survivor Groups

	Deceased group (n = 54; 53%)	Survivor group (n = 48; 47%)	p	Odds ratio
Male gender, n (%)	31 (57.4)	35 (72.9)	0.102	—
Gestational age <32 wks	30 (55.5)	16 (33.3)	0.024	2.5
Five-minute Apgar score <8, n (%)	16 (29.6)	5 (10.4)	0.017	3.621
Birth weight <1500 g, n (%)	42 (77.8)	22 (45.8)	0.001	4.136
Vaginal delivery, n (%)	15 (27.8)	21 (43.7)	0.092	—
Platelet count <50,000/mm³, n (%)	18 (33.3)	4 (8.3)	0.002	5.5
NEC stage 3, n (%)	23 (42.6)	11 (22.9)	0.035	2.496
Sepsis during hospitalization, n (%)	33 (61.1)	10 (20.8)	<0.001	5.971
Surgical treatment, n (%)	12 (22.2)	13 (27.1)	0.569	—

NEC = necrotizing enterocolitis.

p value and odds ratio are bold if p < 0.05.

Table 4.

Comparative Outcomes of Operative versus Non-Operative Treatment Groups

	Operative treatment (n = 25; 24.5%)	Non-operative treatment (n = 77; 75.5%)	p
Mortality, n (%)	15 (60)	39 (50.6)	0.416
Sepsis, n (%)	13 (52)	30 (39)	0.251
Thrombocytopenia, n (%)	11 (44)	28 (36.4)	0.495
Respiratory distress syndrome, n (%)	2 (8)	7 (9.1)	0.867
Length of stay^a (d), median [IQR]	89 [39–101]	95 [51–107]	0.542
Post-natal day death^b (d), median [IQR]	41 [32–59]	51 [39–60]	0.357

IQR = interquartile range.

Among survivors.

Among deceased.

Discussion

Necrotizing enterocolitis is the most common severe gastrointestinal condition in pre-term infants. It is associated with substantial risk of death and long-term morbidity in survivors.¹¹ In our study, we included only pre-term infants with NEC. Growing evidence indicates that NEC in full-term neonates is different from that in pre-term newborns.^16,17

Fifty-four (53%) of our patients died after medical or surgical management of NEC. Despite considerable recent advances in perinatal resuscitation and neonatal care, NEC remains an important cause of mortality with rates ranging from 11% to 58.9%.¹⁸ The main cause that could explain the high mortality rate in our study is the absence of neonatal intensive care and pediatric surgery units in most hospitals in southern Tunisia. Our institution, as an academic referral hospital, is the only institution in southern Tunisia that provides both neonatal intensive care and pediatric surgery services. It covers an area of 100,000 km², and a population of three million inhabitants.

In this study, birth weight and gestational age were higher in survivors. This is in agreement with the majority of published studies. Low birth weight and low gestational age have been identified to be associated with not only NEC incidence, severity, and mortality, but also with long-term neurodevelopmental impairment in survivors.^9,11,18-22

Our study showed that five-minute Apgar score <8 was associated with mortality in NEC patients. Although Siahaan et al.⁹ found no association between Apgar score and outcome in patients with NEC, most authors described a strong correlation between low Apgar score and NEC associated mortality.^10,11,23,24

Interestingly, patients with severe thrombocytopenia had a 5.5-fold higher risk of dying compared with those with a platelet count >50,000/mm³. In accordance with these results, many studies highlighted the role of severe thrombocytopenia as a predictive factor for advanced NEC, morbidity, and mortality.^25,26 Thrombocytopenia is a common feature in neonates with NEC, usually found 24 to 72 hours after developing Although severe thrombocytopenia reflects an excessive platelet consumption and is associated with a poor outcome, moderate thrombocytopenia seems to be protective.²⁵ Based on these findings, Namachivayam et al.²⁷ investigated the mechanisms of platelet depletion associated with NEC-related thrombocytopenia using a neonatal murine model. They concluded that platelet activation, as a consequence of targeted inhibition of thrombin by a nanomedicine-based approach, is a potential therapeutic target in NEC.

Our study revealed that Bell's stage 3 is predictive for mortality in neonates with NEC. This is in agreement with the current clinical, pathophysiologic, and epidemiologic evidence. Thus, most authors highlighted the role of staging as a reliable prognostic factor in patients with NEC.^9–11,23,28 The intestine of the pre-term neonate has a fragile surface area covered by a monolayer of epithelial cells that overlies a highly immunoreactive submucosa. Necrotizing enterocolitis is a multifactorial disease caused by microbial dysbiosis and intestinal immaturity. An underdeveloped immune defense, a compromised intestinal epithelial barrier, and an altered vascular development are the main consequences of this intestinal immaturity. Interactions in the lumen of this immature intestine among microbes, feedings, and intestinal mucosa, can lead to intestinal inflammation. As NEC progresses, it can lead to sepsis, intestinal perforation, peritonitis, and death.^3,29,30 In this growing field, research is still ongoing to understand with greater accuracy the role of bacterial signaling in the pathogenesis of this disease and to identify patients most likely to develop this disease. This certainly requires the identification of specific molecular and genetic biomarkers. With recent advances in this field, there is reason to be optimistic toward the ultimate goal of developing a specific cure for this severe disease.^31,32

In our series, 43 (42.2%) neonates developed sepsis during hospitalization. Not surprisingly, sepsis was the strongest predictive factor for mortality in our patients. Neonatal sepsis is the third most common cause of mortality in neonates and is a growing public health problem, especially in low-income countries.³⁴ Infants with NEC-associated sepsis usually receive more blood transfusions, more often need assisted ventilation support, and have a greater inflammatory response than those without sepsis.³⁴

Despite the lack of a consensual definition, the term neonatal sepsis is usually used to describe a generalized blood stream infection of bacterial, viral, or fungal origin. Blood stream infections represent the most common cause of morbidity and mortality in neonates. Most NEC-associated blood stream infections are caused by gram-negative bacilli.³⁵ Wu et al.³⁶ demonstrated that infants with NEC-associated blood stream infections have greater severity of illness, longer duration of endotracheal intubation, higher rates of infectious complications, and are more likely to develop respiratory failure under a high-frequency oscillatory ventilator. Thus, sepsis seems to be closely linked with poor outcome in infants with NEC.^36–38

Our study is one of the few studies conducted in low-income countries and focusing on risk factors for mortality in pre-term neonates with NEC. These predictive factors would be useful to develop and validate a mortality score, accurately dividing patients into four categories (low, intermediate, high, and very high risk of death). Such a score would be of great interest in the fields of clinical practice and research. However, the findings of this study should be considered in light of some limitations. First, it was a retrospective observational study. Therefore, bias and errors in data extraction were possible. Moreover, the retrospective design of our study made it difficult to assess the long-term complications of NEC, including gastrointestinal sequelae, poor growth, and neurodevelopmental impairment.³⁹ Second, the present study was monocentric, so we believe that further prospective multicenter cohort studies are needed to validate the identified predictive factors. Finally, there has been confusion in the literature as to the exact definition of NEC.⁴⁰ Therefore, we suggest that a consensus definition of NEC is critical to advance research and improve NEC outcomes. In agreement with this recommendation, Patel et al.⁴¹ pointed out that NEC definition has evolved over time. These authors highlighted the urgent need to develop an accurate, reliable, and reproducible definition of NEC.

Conclusions

Footnotes

Authors' Contributions

Mohamed Zouari was responsible for conceptualization, formal analysis, software, supervision, project administration, writing (original draft), and writing (review). Hana Ben Ameur, Wiem Rhaiem, and Nesrine Ben Saad contributed to data curation, formal analysis, resources, software, methodology, visualization, and writing (original draft). Oussama Ghariani and Amel Ben Hamad performed formal analysis and writing (review and editing). Riadh Mhiri performed methodology, supervision, and validation. Mohamed Zouari is the guarantor.

Funding Information

The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

Author Disclosure Statement

We, the authors, have no financial or personal relationships with other people or organizations that could potentially and inappropriately influence our work and conclusions.

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