Cardiovascular Journal of Africa: Vol 32 No 6 (NOVEMBER/DECEMBER 2021)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 32, No 6, November/December 2021 310 AFRICA (IABP) were associated with the development of CSA-AKI ( p < 0.05) (Table 3). History of hypertension was predictive of development of CSA-AKI ( p < 0.05) in an adjusted model (Table 3). Ninety-six (71%) patients were classified as KDIGO 1, 23 (17%) KDIGO 2, and 16 (12%) KDIGO 3 (Table 4). The mortality rate was 9.6% (46 out of 476 patients). Mortality rates were significantly higher in those with AKI compared to those without [28 (21%) vs 18(5%), respectively] ( p = 0.001) (Table 5). The incidence was significantly worse in those with more severe kidney injury, as evidenced by mortality rates of 44 versus 5% between KDIGO 3 and KDIGO 1 ( p < 0.001) (Table 4). Causes of mortality for 21 patients were unclear and unspecific in the reports, while four were reported to be from septic shock with multi-organ failure, one from renal failure, one from left ventricular rupture, and one death on the table following relook surgery. The pre-operative eGFR status of the 28 patients who had developed AKI and died are as follows: five had normal renal function, 13 mild renal dysfunction, eight moderate-to- severe renal dysfunction and two had renal failure. The Kaplan–Meier survival analysis (Fig. 2) showed the cumulative probability of dying on the first day to be higher for patients without AKI (15.8%, 95% CI: 5–41%) compared to patients with AKI (3.7%; 95% CI: 1–23.5%). The median (IQR) failure time (time to mortality) was 13 (1–40) days for patients without CSA-AKI and only 6 (3–16) days for patients with CSA-AKI. The difference was not statistically significant. Although mortality for patients with CSA-AKI seemed higher (Fig. 2) after the first week, with a shorter median (IQR) time to mortality, the overall in-hospital mortality rate was not statistically different (UHR = 1.51, 95% CI: 0.76–2.99, p = 0.240) between groups. A univariable Cox regression analysis (Table 6) showed a significant relationship between in-hospital mortality and a history of smoking, coronary artery bypass graft (CABG) surgery, aortic surgery, pre-operative eGFR and CSA-AKI requiring RRT ( p < 0.05). Inclusion of those factors from the univariable Cox regression with p ≤ 0.1 in a multivariable Cox regression model showed pre-operative eGFR to be the sole predictor of in-hospital mortality (HR 0.99, 95% CI: 0.97–0.99, p = 0.019). Table 2. Demographic and pre-operative data of patients who presented for cardiac surgery on CPB Pre-operative variables All patients ( n = 476) [median (IQR)/ n (%)/mean (SD)] Age (years) 53 (39–62) Male gender 255 (53) Weight (kg) 70 (59.5– 83) Height (m) 1.66 (1.6–1.73) BMI (kg/m 2 ) 2 4 (21.5–29.8) African race 245 (52) Diabetes mellitus 67 (14) Hypertension 126 (26) Hypercholesterolaemia 77 (16) Smoking 84 (18) Pre-operative SCr (mg/dl) 1.03 (0.89–1.24) Type of cardiac surgery CABG 172 (36) Valve surgery 253 (36) Aortic surgery 18 (4) Other 43 (9) eGFR (ml/min/1.73 m 2 ) < 15 4 (1) 15–60 97 (20) 60–90 (48) > 90 148 (31) KDIGO class 0 342 (72) 1 96 (20) 2 23 (5) 3 16 (3) BMI, body mass index; SCr, serum creatinine; CABG, coronary artery bypass graft; eGFR, estimated glomerular filtration rate; KDIGO, Kidney Disease Improving Global Outcomes. Table 3. Comparison of peri-operative/baseline parameters Parameter CSA-AKI ( n = 135) No CSA-AKI ( n = 342) p -value [ mean (SD)/median (IQR)/ n (%)] [mean (SD)/median (IQR)/ n (%)] Age (years) 56 (42–63) 52 (37.5–61) 0.024 Male gender 51 (37) 171 (50) 0.015 Weight (kg) 73 (60–85) 70 (59–83) 0.146 Height (m) 1.69 (1.64–1.74) 1.65 (1.59–1.72) 0.996 BMI (kg/m 2 ) 26 (21.6–30.3) 2 2 (21.5–29.8) 0.603 African race 76 (56) 157 (45) 0.441 Diabetes mellitus 24 (18) 42 (12) 0.120 Hypertension 34 (25) 91 (27) 0.724 Smoking 25 (19) 58 (17) 0.696 Cholesterol 20 (15) 56 (74) 0.666 Pre-operative eGFR (ml/min/1.73 m 2 ) 76.5 (58.3–89.9) 80.4 (61–98.35) 0.024 eGFR < 15 2 (2) 2 (0.5) 0.099 15–60 34 (25) 63 (18.5) 60–90 66 (49) 160 (47) > 90 32 (24) 115 (34) Baseline SCr (mg/dl) 1.09 (0.92–1.3) 1.01 (0.87–1.21) 0.005 Type of cardiac surgery 0.319 CABG 56 (41) 111 (33) 0.319 Valves 56 (41) 186 (55) Aorta 5 (4) 12 (3) Other 11 (8) 32 (9) CPB time (min) 157 (121–203) 144 (113.5–179) 0.040 IABP 13 (10) 6 (2) < 0.001 Cross-clamp time (min) 100 (81–133) 95 (71–120) 0.053 Lowest temperature on pump 30 (30–32) 32 (30–32) 0.200 ECMO 13 (10) 8 (2) 0.001 VAD 0 2 (0.6) 0.372 SCr difference from baseline (mg/dl) Day 1 0.10 (–0.05–0.27) –0.09 (–0.19–0.01) < 0.001 Day 2 0.35 (0.18–0.61) –0.06 (–0.19– –0.19) < 0.001 Day 3 0.38 (0.08–0.74) –0.14 (–0.27– –0.02) < 0.001 Day 4 0.25 (–0.02–0.67) –0.18 (–0.36– –0.06) < 0.001 Day 5 0.08 (–0.11–0.62) –0.21 (–0.42– –0.09) < 0.001 Day 6 0.09 (–0.20–0.57) –0.25 (–0.61– –0.10) < 0.001 Day 7 0.05 (–0.24–1.26) –0.20 (–0.50– –0.05) < 0.001 Mortality 28 (21) 18 (5) < 0.001 BMI, body mass index; eGFR, estimated glomerular function; SCr, serum creati- nine; CABG, coronary artery bypass graft; IABP, intra-aortic balloon pump; ECMO, extracorporeal membrane oxygenator; VAD, ventricular assist device.