Indications for surgery and influences on surgical decision-making in necrotising enterocolitis

Abstract

Necrotising enterocolitis (NEC) causes severe bowel inflammation and critical illness in, predominantly, preterm infants with over 400 cases yearly in the United Kingdom alone. Despite medical management in a neonatal intensive care unit, between 25-50% fail to respond and require surgery to remove necrotic bowel. Identification of which infants would benefit from surgery in a timely manner is challenging but important since delay in surgery may contribute to poor outcomes. About 20% of infants with NEC die without undergoing surgery. Mortality rate following surgery is 35% and, in survivors, 9% remain on parenteral nutrition at 1 year with 59% experiencing neurodevelopmental problems with lifelong impact.

Recent data suggest that delay to undertaking surgery in NEC is associated with poor outcome. Hence, there is a need for early and accurate identification of infants with NEC requiring surgery to allow earlier surgical intervention. To address this need, this thesis focuses on 3 research questions: 1) Which tools are available to identify surgical necrotising enterocolitis (NEC)? 2) Can surgical NEC be accurately identified using routinely available clinical, laboratory and radiological data? 3) What informs surgical decision-making in NEC currently, and what are facilitators and barriers to surgical decision-making?

To identify previously reported tools for the identification of surgical NEC I undertook a systematic review, and where possible meta-analyses. This identified 114 tools for identifying surgical NEC in 9,546 infants consisting of 44 scoring systems, 37 single biomarkers, 24 imaging tools and 9 invasive tools. Several tools were deemed to be worthy of further investigation based on reported effectiveness, repeatable methods and low risk of bias and applicability concerns on QUADAS-2 assessment.

To assess the effectiveness of these tools, and allow direct comparison of these, I undertook a diagnostic accuracy study which used readily available retrospectively collected data within a multicentre dataset from four neonatal surgical units. This included a total of 579 infants, comprising 336 who had surgical NEC or died of NEC and 243 had medical NEC. Surgical NEC was defined here as infants who had undergone surgery where NEC was confirmed. The tools with the highest sensitivity were a 4-feature score and the SNAPPE-II score with a threshold of >15.5. Both had a sensitivity of 1.00 however overall accuracy was 0.68 and 0.60 respectively.

Given the limitations of the existing tools, I wanted to understand how clinicians currently make decisions around surgery. I undertook three semi-structured focus groups with a total of 22 consultant participants, to determine the views and reported practice of paediatric surgeons and neonatologists towards surgical decision-making in NEC. Reflexive thematic analysis generated 10 themes which addressed what informs surgical decision-making in NEC, six themes addressed why this is challenging and five explained what is required to address the challenges. The focus groups also informed the design of a national survey of both consultant paediatric surgeons and neonatologists. Of the 168 respondents, 93% sometimes find surgical decision-making in NEC challenging. The survey explored which factors clinicians use to determine need for surgery. Clinicians reported that they find the trajectory of clinical, laboratory and radiological features over time, rather than single observations, most useful when deciding whether an infant with NEC should undergo surgery. A discrete choice experiment was undertaken to determine which features are considered most important in surgical decision-making by surgeons. The distributed experiment included 22 clinical scenarios with 7 features at up to 3 levels of severity and was analysed using conditional logistic regression. Progression of abdominal examination findings (OR 14.6 [95% CI 9.26 to 22.9]) and increasing inotrope requirement (OR 7.91 [95% CI 5.45 to 11.5]) were factors most strongly associated with a decision for surgery. Surgeons were also more likely to recommend surgery with severe metabolic acidosis (OR 5.20 [95% CI 2.90 to 9.33]) and increasing time from NEC diagnosis (OR 4.75 [95% CI 3.22 to 6.99]).

Whilst the survey and focus groups described intended practice, in order to determine what influences surgical decision-making in real clinical practice, I undertook a prospective qualitative observational study over 12 months in 10 high volume surgical neonatal centres. Here I undertook a qualitative telephone interview shortly after a consultant surgeon had reviewed an infant with NEC and made a decision for surgery, or to continue medical management. This included 89 interviews with 40 consultant surgeons regarding 78 infants. In 10 (13%) infants, more than one interview was completed as clinical reassessment took place during the infant’s care, sometimes with a different consultant. Codebook thematic analysis from the focus groups generated themes regarding influences and challenges of surgical decision-making while several new themes or sub- themes were also generated. These themes were then mapped to infant, clinician and system related facilitators and barriers to surgical decision-making with representative quotations from interview transcripts.

Work undertaken in this thesis has identified a large number of objective tools to identify need for surgery in NEC. Some of these could be used in clinical practice. For example, those with high sensitivity could be used as an early warning system, prompting need for surgical review. Unfortunately, the overall tool accuracy limits the use of these as originally designed. These is a clear need for increased objectivity in surgical decision-making based on focus group discussion and survey analysis. Findings from the discrete choice experiment provide insight into the acceptability of candidate factors for surgeons as further objective measures are developed. Qualitative work has identified many facilitators and barriers to surgical decision-making. Barriers could be addressed through either further research, policy change or quality improvement projects whilst facilitators could be used to standardise care between different centres and surgeons. Some of these will be easier to implement and evaluate than others but taken together there is now clear direction of how surgical decision-making for infants with NEC can be improved to ultimately progress care for infants with NEC.

More information

Identifiers

ORCID for Nigel Hall: orcid.org/0000-0001-8570-9374

Catalogue record

Export record