Post-Operative Complications Following Emergency Laparotomy are Common and Associated with increased Late Mortality - A Retrospective Multi-Centre study

Post-Operative Complications Following Emergency Laparotomy are Common and Associated with Late Mortality - A Abstract Emergency abdominal surgery, often termed emergency laparotomy, is a common surgical procedure undertaken in the United Kingdom (U.K), with approximately 30000 procedures annually. Patients presenting for emergency abdominal surgery are heterogeneous and present with diverse pathology, resulting in challenges for the surgical, anaesthetic and critical care team that manage them. Emergency laparotomy, by its very nature is high-risk surgery, with an estimated 30-day mortality in the U.K of 11%, which is over 10 times greater than the mortality of patients undergoing major elective surgery (e.g. cardiac, vascular and oncological surgery) and a median hospital length of stay (LOS) of 12-days. Risk factors associated with poorer outcomes from emergency laparotomy have been identified by the National Emergency Laparotomy Audit (NELA) and include advancing age, with each decade above the age of 50 being associated with increasing risk. Additional risk complications (PPCs) is a composite definition for a variety of respiratory complications that occur following surgery. They range from clinically significant bronchospasm and atelectasis, through to the development of pneumonia and the acute respiratory distress syndrome (ARDS). The incidence following elective major abdominal surgery has been estimated at 11.9% and is associated poorer outcomes with increased length of hospital stay, increased readmissions and a higher mortality. Although emergency surgery is well established as a significant risk factor for the development of PPCs, the incidence is not well established. This study aimed to establish the incidence of PPCs in a cohort of patients undergoing emergency laparotomy and the consequences on patient outcomes.


Background
Emergency abdominal surgery, often termed emergency laparotomy, is a common surgical procedure undertaken in the United Kingdom (U.K), with approximately 30000 procedures annually [1].
Patients presenting for emergency abdominal surgery are heterogeneous and present with diverse pathology, resulting in challenges for the surgical, anaesthetic and critical care team that manage them.Emergency laparotomy, by its very nature is high-risk surgery, with an estimated 30-day mortality in the U.K of 11%, which is over 10 times greater than the mortality of patients undergoing major elective surgery (e.g.cardiac, vascular and oncological surgery) and a median hospital length of stay (LOS) of 12-days [2,3].

Design and Setting
A retrospective analysis was conducted of patient that underwent emergency laparotomy between December searched over the same timeframe to cross-reference patients and collect patients that had not been initially identified using the NELA database.

Data collected
Individual patient data was collected using the NELA database which collects information to include baseline demographics, date of operation, risk stratification using ASA score, P-POSSUM, serum lactate and serum creatinine, operative details, critical care service utilisation post-operatively and in-hospital outcomes.
This was supported by electronic EPR systems at each trust to collect data for PPCs, unplanned hospital readmissions and mortality at 90-days, 180-days and 365-days.

Definition of High-Risk and Low-Risk patients
As described previously patients presenting for emergency surgery are heterogeneous with different groups of patients having variable outcomes.Patients were therefore categorized as high or low-risk based 3 or a P-POSSUM predicted evidence from 30000 cases analysed by the NELA group, that suggested that adverse outcomes occur if a patient meets any one of these three variables(3).

Diagnosis of PPCs
PPCs were identified using the Melbourne Group Score.This is a validated daily screening tool for identifying patients with PPCs and has been used

Statistical Analysis
Continuous data was analysed for normality using a

Results
A total of 437 patients were identified as having undergone emergency laparotomy between the 1 st of December 2014 and 31 st November 2015.75 cases were excluded due to duplication or incorrect coding of the procedures.Of the 362 remaining patients, 136 were classified as low-risk patients and 226 as being high-risk (figure 2).

Demographics
The median age of the entire cohort was 62 years (IQR 45-74 years), with 47% (n=170) of patients being male.The majority of patients (64% n=230) had an ASA ³3 with a median P-POSSUM score of 6% (2.3-19.3%).48% (n=174) of patients were admitted directly to critical care units (CCU) following surgery.
The median length of hospital stay was 13 days (IQR 6-25), with a 30-day mortality of 12% (n=44).(see  patients were excluded as they were either duplicated or the procedure was incorrectly coded.

Incidence of PPCs
The incidence of PPCs within the entire cohort was 30% (n=108).The burden of PPCs were almost entirely in the high-risk patients with an incidence of 37% (n=84), with only 6% (n=8) of the low-risk patients developing a PPC.The demographics of patients who were diagnosed with and without a PPC are shown in table 2. There were no significant differences between these patients, although patients who did develop a PPCs showed a trend towards an increased pre-operative P-POSSUM predicted mortality scores and were more likely to be admitted directly to CCU (85% vs. 71%; p=0.02).Importantly, there were no differences between these two cohorts in baseline respiratory or cardiovascular disease as measured by the P-POSSUM risk score.The commonest post-operative day to develop a PPC was day 3(median; IQR 1-4days).

Outcomes in patients with PPCs
Patients that developed a PPC during the first 7 postoperative days had poorer outcomes compared to patients who did not develop a PPCs.This included a median increase in CCU length of stay by 1-day (p-0.002) and a median increase in hospital length of stay of 3days (p=0.01).There was no difference in 30-day mortality, however there was a significant increase in both 90, 180 and 365-day mortality (see figure 3).In addition, the number of re-admissions in patients who developed a PPC was increased at similar time-points.

Multivariate analysis
Cox's multiple regression was performed on factors that may have predicted the development of a PPC in the high-risk cohort.No individual factors predicted the likelihood of PPC development in the high-risk cohort.

Discussion
Emergency abdominal surgery by its very nature is associated with increased morbidity and mortality.[9,10].These studies suggest that elective patients who develop PPCs have increased length of stay and an increased 30-day mortality [11,12].Our study supports these findings; however it demonstrates that its incidence is much higher and that outcomes in the longer term (through to 1-year) are much worse.
Interestingly our study showed that PPCs were one of the major sources of morbidity, with surgical site Risk factors associated with poorer outcomes from emergency laparotomy have been identified by the National Emergency Laparotomy Audit (NELA) and include advancing age, with each decade above the age of 50 being associated with increasing risk.Additional risk factors include an American Society of Anaesthesia (ASA) status of 3 or more and Portsmouth-Physiological and Operative Severity Score for the enumeration of Mortality and morbidity (P-POSSUM) risk of death of greater than 5% [3].The development of post-operative pulmonary complications (PPCs) is a composite definition for a variety of respiratory complications that occur following surgery.They range from clinically significant bronchospasm and atelectasis, through to the development of pneumonia and the acute respiratory distress syndrome (ARDS) [4].The incidence following elective major abdominal surgery has been estimated at 11.9% and is associated poorer outcomes with increased length of hospital stay, increased re-admissions and a higher mortality [5].Although emergency surgery is well established as a significant risk factor for the development of PPCs, the incidence is not well established.This study aimed to establish the incidence of PPCs in a cohort of patients undergoing emergency laparotomy and the consequences on patient outcomes.
previously in patients undergoing major abdominal and thoracic surgery(7).The score consists of 8 dichotomous factors that include microbiological, clinical and physiological parameters, with a score of 4 or more indicating the development of a clinically significant PPCs that are likely to adversely affect the patient's clinical course (figure 1).Patients EPRs were screened daily from the day of operation till the seventh post-operative day for PPCs using the Melbourne Group Score.The daily score was recorded and where a patient met the diagnosis of a PPC the post-operative day of occurrence was recorded.

D
'Agostino and Pearson omnibus normality test.All data were non-parametric and therefore all continuous is represented as median and inter-quartile ranges (IQR), with comparative tests between groups analysed using a Mann-Whitney U test.Categorical data are represented as numbers and proportions with any comparative tests performed using a Fisher's exact or Chi-squared test.Kaplan-Meier analysis and odd's ratio were performed to quantify the consequences of PPC development on survival and re-admissions.These were calculated using a log-rank Mantel-Cox Chi-squared test.All data analysis was performed using GraphPad PRISM version 6 (La Jolla, USA).Additionally, to identify factors that may predict the development of PPCs Cox-logistical regression was carried out using SPSS.Significance was taken as a p-value of less than 0.05.

Figure 1 :
Figure 1: The Melbourne Group Score.A post-operative pulmonary complicsation can be diagnosed if 4 or more of these factors are present.

Figure 2 :
Figure 2: This image shows an overall summary of our starting cohort being broken down into separate groups.75 infections and acute myocardial ischaemia being infrequently reported.PPCs are a composite definition, with the validated Melbourne Group Score designed to select the clinically significant infection and atelectasis, which arguably are the most serious and often lead to acute lung injury (ALI) and ARDS.The development of nosocomial pneumonia and infections has been shown in several studies to increase length of stay in CCU and also in-hospital, however the precise reasons why longer-term outcomes are poorer is uncertain.It has been suggested that episodes of

Table 1 :
Demographics and risk stratification of our cohort are showing in this table.The table demonstrates high risk patients ended up having significantly worse outcomes than low risk patients.

Table 2 :
Table showing the differences in demographics between patients who developed a PPC after laparotomy vs patients who did not.