The Ethics Committee of Erasme, Brussels, Belgium on February 10th, 2020, approved this single centre retrospective cohort analysis (Reference: P2020/031). Data collection was performed by Z.M in our institution between February 11th and April 1st 2020.
We included all consecutive adult patients (≥ 18 years old) who:
1) had undergone elective high-risk abdominal surgery (including hepatobiliary surgery, pancreatectomy, gastrectomy, oesophagectomy, cancer debulking, and cystectomy) under general anaesthesia between January 1st, 2014, and April 30th, 2019. Patients who had had major vascular surgery were also included if the surgery involved an abdominal incision (e.g., aorto bifemoral bypass and abdominal aortic aneurysm surgery);
2) had a plasma creatinine value measured before surgery, within 7 days after surgery, and at a later follow up visit (6 months to 2 years after surgery).
Patients who received dialysis in the preoperative period, those with chronic kidney disease (predefined as a baseline creatinine level > 1.5 mg/dl), those who had emergency surgery and patients who had another surgical procedure in the two years following their first surgery (unless it was a redo surgery in the same admission) were excluded. Patients who had suprarenal clamping during their vascular surgery were also excluded as this clamping phase can seriously impact renal function.
For each eligible patient, we recorded, from our hospital health records, the plasma creatinine concentration prior to surgery (the most recent result available in the three months before surgery), the highest creatinine concentration during the seven postoperative days, and the creatinine concentration at long-term follow up (between 6 months and 2 years; if multiple creatinine values were available, the measurement closest to one year following surgery was always selected). If no long-term creatinine measurement was available in the hospital database, attempts were made to contact the patients and/or their general practitioners to obtain any values that had been measured elsewhere.
The change in creatinine concentration between the preoperative and the postoperative period was used to classify patients according to a “modified” KDIGO classification in which the urine output criteria were not considered [17]. Mild AKI (KDIGO stage 1) was characterised by an increase in creatinine of ≥ 0.3 mg/dl within 48-hours or 1.5–1.9 times baseline; moderate AKI (KDIGO stage 2) by an increase in creatinine of 2-2.9 times baseline; and severe (KDIGO stage 3) was characterised by an increase in creatinine 3 times baseline or to ≥ 4.0 mg/dl). To simplify our statistical analysis because of the low occurrence rate, AKI stages 2 and 3 were combined into a single category (2–3), leaving us with three final groups (no AKI vs AKI stage 1 vs AKI stage 2–3).
Long-term renal injury was defined using the difference between the preoperative creatinine concentration and the long-term follow-up measurement. We used the same KDIGO classification system to stage long-term renal injury as we used for the immediate postoperative period.
2.1. Statistical Analysis
Distribution of continuous data was analysed using a Kolmogorov-Smirnov test. Normally distributed data are presented as means ± standard deviation and were compared between groups using a one-way analysis of variance. Non-normally distributed data are presented as medians (interquartiles ranges) and were compared using a Kruskall-Wallis test. Dichotomous variables are presented as crude numbers and percentages and were compared between groups using a Chi-square test. Modelling of the risk of long-term renal injury was performed using the same approach as Turan et al [20] including early AKI and all covariates listed in Tables 1 and 2 in a logistic (binomial) model. The risk of developing long-term renal injury is presented as an odds ratio with 95% confidence intervals. Statistical analyses were done using Minitab 16 (Paris, France and Medcalc Software LTD, Ostend, Belgium) and R (www.r-project.org)
Table 1
Patient Characteristics by acute kidney injury status
Variables | No AKI (N = 706) | AKI stage 1 (N = 81) | AKI stage 2–3 (N = 28) | P-value |
Age (years) | 65 [55–72] | 68 [63–74] | 65 [57–75] | 0.038 |
Male (%) | 424 (60) | 60 (74) | 25 (89) | 0.001 |
BMI (kg/m2) | 25 [23–29] | 26 [22–30] | 27 [25–35] | 0.076 |
ASA score (1–2 / 3–4) | 430 / 276 | 50 / 31 | 16 / 12 | 0.910 |
Preop Hb (g/dL) | 13.3 [12-14.5] | 13.4 [11.8–14.3] | 13.9 [12.5–14.7] | 0.702 |
Preop creatinine (mg/dL) | 0.8 [0.7-1.0] | 1.0 [0.8–1.1] | 1.0 [0.8 1.2] | < 0.001 |
Comorbidities; N (%) | | | | |
Myocardial infarction Coronary arterial bypass graft Hypertension Hyperlipidaemia Stroke Atrial fibrillation Diabetes mellitus type 2 COPD Cirrhosis | 60 (85%) 28 (4%) 319 (45%) 194 (27%) 28 (4%) 44 (6%) 151 (21%) 86 (12%) 53 (8%) | 3 (4%) 3 (4%) 52 (64%) 28 (35%) 2 (2%) 12 (15%) 17 (21%) 10 (12%) 4 (5%) | 9 (32%) 3 (11%) 20 (71%) 7 (25%) 3 (11%) 1 (4%) 7 (25%) 9 (32%) 2 (7%) | < 0.001 0.210 < 0.001 0.378 0.155 0.013 0.895 0.008 0.700 |
Medications; N (%) | | | | |
Aspirin Clopidogrel ẞ blocker ACEI ARB Calcium channel blocker Diuretics Statin Oral hypoglycaemic drugs Insulin Oral anticoagulation | 236 (33%) 32 (5%) 166 (24%) 135 (19%) 47 (7%) 113 (16%) 59 (8%) 211 (30%) 111 (16%) 56 (8%) 65 (9%) | 32 (40%) 1 (1%) 28 (35%) 23 (28%) 8 (10%) 19 (23%) 8 (10%) 18 (22%) 10 (12%) 7 (9%) 9 (11%) | 8 (29%) 3 (11%) 13 (46%) 11 (39%) 3 (11%) 7 (25%) 8 (29%) 12 (43%) 4 (14%) 2 (7%) 3 (11%) | 0.458 0.100 0.003 0.007 0.426 0.126 0.001 0.105 0.718 0.962 0.834 |
Type of Surgery (N) | | | | 0.022 |
Pancreatectomy Hepatobiliary Oesophagectomy Cystectomy Cancer debulking Major aortic vascular surgery Other surgical procedure * | 155 (22%) 189 (27%) 75 (11%) 63 (9%) 32 (5%) 144 (20%) 48 (7%) | 18 (22%) 14 (17%) 12 (15%) 15 (19%) 2 (2%) 15 (19%) 5 (6%) | 3 (11%) 3 (11%) 3 (11%) 7 (25%) 2 (7%) 9 (32%) 1 (4%) | |
Values are presented as medians [interquartiles ranges] or numbers (percentages %). |
Abbreviation: COPD: chronic obstructive pulmonary disease; AKI: acute kidney injury - BMI: body mass index - preop: preoperative - ACEI: Angiotensin-converting-enzyme inhibitor - ARB: Angiotensin II receptor blocker - Hb: haemoglobin - ASA: American Society of Anesthesiologists |
* included: gastrectomy, open colectomy nephrectomy, surrenalectomy, prostatectomy) |
Table 2
Intraoperative variables by acute kidney injury status
Variables | No AKI (N = 706) | AKI stage 1 (N = 81) | AKI stage 2–3 (N = 28) | P-value |
Anaesthesia duration ( min) | 346 [260–446] | 421 [339–502] | 451 [354–576] | < 0.001 |
Surgery duration (min) | 262 [184–352] | 337 [263–397] | 366 [282–445] | < 0.001 |
Total crystalloid (ml) | 2000 [1300–3000] | 3000 [2000–4000] | 4000 [2000–5875] | < 0.001 |
Total colloid £ (ml) | 500 [500–1000] | 1000 [500–1500] | 1000 [500–2000] | 0.008 |
Total blood product (ml) | 500 [263–764] | 550 [396–1683] | 525 [270–1858] | 0.157 |
Total IN (ml) | 2500 [1800–3500] | 3500 [2500–5374] | 4500 [2275–7313] | < 0.001 |
Estimated blood loss (ml) | 500 [200–1000] | 700 [300–1725] | 1000 [463–1575] | < 0.001 |
Diuresis (ml) | 300 [150–500] | 300 [175–500] | 310 [160–496] | 0.862 |
Gastric suction (ml) | 100 [50–100] | 50 [50–100] | 50 [50–163] | 0.668 |
TOTAL OUT (ml) | 913 [550–1600] | 1110 [750–2125] | 1375 [900–2188] | 0.002 |
Net fluid balance (ml) | 1510 [798–2353] | 2300 [1384–3275] | 3125 [1138–5186] | < 0.001 |
Use of vasopressors, N (%) | 554 (78) | 67 (83) | 23 (82) | 0.619 |
Values are presented as medians [interquartiles ranges] or numbers (percentages %). |
£ total colloid included 3% gelatin and 6% tetrastarch |