Post operative acute kidney injury after HPB surgeries – A single centre retrospective analysis

Aim: Aim of our study was to evaluate incidence and causative factors for acute kidney injury in hepatopancreaticobiliary (HPB) surgeries. Material and Methods: All the HPB surgeries performed between April 2018 to March 2020, in our institution have been analysed for acute kidney injury. Acute kidney injury defined according to acute kidney injury network classification. Categorical variables were evaluated by chi square test and fisher t test wherever approptiate and continuous variables by Mann Whitney U test. Statistical analysis was done using SPSS version 23. P< 0.05 was considered significant. Results: We performed 195 HPB surgeries between April 2018 to March 2020, Which included 114 biliary surgeries, 57 liver surgeries and 23 pancreas surgeries. 10 patients developed Acute Kidney Injuries. (AKI) On Univariate analysis AKI was associated with open surgeries, intra operative hypotension and liver surgeries, higher ASA grade, increase operative time, more blood products used, higher CDC grade of surgery and more hospital stay before diagnosis of AKI. However on multivariate analysis only higher ASA score independently predicted Acute Kidney Injury. (p=0.003, odds ratio 15.659, 95% confidence interval 2.54-93.36). AKI was also significantly associated with mortality. (p <0.0001). Conclusion: Pre operative higher ASA grade independently predicted post operative acute kidney injury. Post operative AKI is significantly associated with mortality.

Very few studies has evaluated risk of acute kidney injury in cohort of HPB surgeries.

Aim of the study:
Aim of this study was to evaluate incidence and risk factors of acute kidney injury retrospectively from our data of hepatopancreaticobiliary (HPB) surgery.

Material and Methods:
Inclusion crteria: All patient who underwent gastrointestinal and hepatobiliary surgeries.

Exclusion crteria:
• Patients who had acute kidney injury pre operatively • Patients who were on dialysis before surgery • Patients who died on post operative day 1, before Acute Kidney Injury criteria is fulfilled.
All the gastrointestinal surgeries performed from April 2018 to March 2020 in our institution have been analysed for acute kidney injury.

Acute kidney injury definition:
Acute kidney injury defined according to acute kidney injury network classification. [6,7]. Any grade of acute kidney injury was considered significant.
Pre operative and Intra operative factors were analysed for development of acute kidney injury.

Statistical analysis:
Analysis of means or medians were selected according to skewness and standard error of skeuness and kurtosis and standard error of kurtosis analysis.Catagorical variants were analysed using chi square test with or without yates correction or fisher t test where ever appropriate. Continuous variable were analysed using Mann whitney u test. P value less than 0.05 was considered significant. Multivariate analysis was done using logistic regression method. SPSS (IBM) version 23 was used for statistical analysis.
We also prepared Kaplan Meier survival curve with log rank analysis to compare 90 days survival rates in patients with or without AKI.

Results:
We performed 195 gastrointestinal and hepatobiliary surgery from April 2018 to March 2020. Which included 114 biliary surgeries, 57 liver surgeries and 23 pancreas surgeries . Liver surgeries included 12 liver transplants.
1 patient had pre operative acute kidney injury, 1 patients were on dialysis and two patient died on post operative day 0 and hence excluded from the study. 191 patients were included in the study. 10 patients (5.2%) was defined as having acute kidney injury according to acute kidney injury network classifications. [6,7].

DISCUSSION:
Acute kidney injury (AKI) is a common complication in patients undergoing major Gastrointestinal and hepatobiliary surgery. Various studies stated, incidence of AKI after major abdominal surgery may go up to 35%. Several patient-related, procedurerelated factors for AKI. were associated with increase incidence of morbidity and mortality in various studies. [8,9] Aim of our study was to evaluate incidence and various factors associated with Acute kidney injury. Two criteria for diagnosing acute kidney injury is widely used one is RIFLE criteria and other is Acute Kidney Injury Network criteria. [6,10]. We used Acute Kidney Injury Network criteria to diagnose acute kidney injury network and we included all the grades of acute kidney injury network classification in our analysis.
Overall incidence of acute kidney injury in our cohort was 5.2%. Cho et al. reported 7.6 percent acute kidney injury after HPB surgeries. [9] Meersch et al. [11] reported high incidence of acute kidney injury.
Acute kidney injury in our study was significantly associated with mortality.
On univariate analysis in our study open surgeries, intraoperative hypotension, higher ASA (American society of anaesthesiology) grade, higher CDC wound grade, increase blood product requirement, increased operative time and liver surgeries were associated with development of acute kidney injury. Hobson et al. studied various risk factors associated with peri operative risk factors, and shoed previous history of chronic kidney disease and haemoglobin level was associated with post operative acute kidney injury. [14] In our study increase blood product required was associated with acute kidney injury. Lim et al. suggested that hepatectomy was associated with high incidence of acute kidney injury, they suggested major hepatectomy, increase meld score, advanced age and prolonged operative duration were associated with acute kidney injury. In our study hepatectomy or liver surgeries was associated with aki in univariate analysis but not on multivariate analysis. In our study age were not associated with acute kidney injury however prolonged operative duration was associated with acute kidney injury in our study also. [15] Various studies showed that intra operative hypotension was associated with post operative acute kidney injury. [16,17,18] In our study also intraoperative hypotension was associated with acute kidney injury in univariate analysis however it did not independently predicted acute kidney injury on multivariate analysis.
In multivariate analysis in our study higher American society of anaesthesiology score (p +0.003 were associated with acute kidney injury Literature also supports these findings. [19,20] In our study acute kidney injury was associated with increased hospital stay, which is also supported by literature. [21,22] Being a retrospective analysis our study has inherent limitations associated with retrospective studies. Number of patients who developed acute kidney injury were low in our studies. More studies with higher number of patients is required to confirm our findings.
In conclusion, post-operative acute kidney injury was associated with significant mortality in hepatobiliary surgery. Open surgery, higher CDC grade surgery, more blood products, higher ASA grades, increase operative time and liver surgeries predicted acute kidney injury in post operative periods. Higher ASA grades independently predicted acute kidney injury.