6 курс / Нефрология / Острое_повреждение_почек_после_паратиреоидэктомии_по_поводу_первичного

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3.2.2. Initial kidney status related factors

One of the most significant AKI risk factors in the general population is preexisting CKD, thus to assess the disease prevalence in the study sample was of particular interest. It should be noted CKD stage 1 and 2 is rarely diagnosed in general therapeutic practice but rather is in the scope of specialized nephrology centers, and is mainly applied to the patients with a morphologically confirmed chronic glomerulonephritis without renal function impairment, as an isolated form or as a systemic pathology. Patients with PHPT are routinely managed by an endocrinologist and, if necessary, a physician, and CKD diagnosis is most often established in them based on persistent GFR decrease of less than 60 mL/min/1.73 m2 - i.e., CKD stage C3 and above. In the study population, 19 of 106 patients with AKI (17.9%) and in 22 of 184 patients without AKI (12%) was aggravated with pre-existent CKD.

The risk of AKI did not differ in patients with and without baseline CKD: RR=1.33 [95%CI 0.88; 1.86], OR=1.6 [95%CI 0.82; 3.04], p=0.1601. There was also no statistically significant association of AKI risk and pre-existing CKD (p=0.451).

The median eGFR in patient groups with and without AKI was 84.45 mL/min/1.73 m2 [Q1-Q3: 65,5; 96.6] and 76.6 mL/min/1.73 m2 [Q1-Q3: 64.9; 90.6] respectively, p = 0.118. The ROC curve was obtained to assess eGFR impact on AKI probability (Figure 3.19). The area under the obtained eGFR ROC curve was 0.555 [95%CI 0.48; 0.63], p=0.1179.

For a more detailed analysis of baseline eGFR and AKI association, the patients were divided into subgroups depending on the eGFR: of more than 60 mL/min/1.73 m2 group and of less than 60 mL/min/1.73 m2 group. No statistically significant difference was shown for AKI incidence in patient groups of different baseline eGFR (p =0.4656) - Figure 3.7. Thus, patients with both preserved and reduced eGFR are at equal risk of postoperative AKI.

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Figure 3.7. AKI incidence in patient groups of different baseline eGFR.

Proteinuria is a reliable marker of pre-existing renal injury and its extent. Preoperative urinalysis results were available in 239 of 290 patients in the study population. Proteinuria was observed significantly more often in patients with AKI compared to patients without AKI: 17% (15/88) vs 5.3% (8/151) respectively – Figure 3.8. The risk of AKI was significantly higher in patients with protein in the urine: RR = 1.9 [95% CI 1.19; 3.54], OR=3.67 [95%CI 1.5; 8.73], p=0.0061. Only 5 of 23 (21.7%) patients with proteinuria had eGFR of less than 60 mL/min/1.73m2.

n of observations

yes no Proteinuria

Figure 3.8. AKI incidence depending on concomitant proteinuria.

One of the important AKI risk factors for is intraoperative hypotension. Since hemodynamics is most variable during the patient’s mechanical ventilation,

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intraoperative blood pressure dynamics analysis was reasonably limited by this time period. The median ventilation duration was 45 minutes [Q1-Q3: 35; 60]. The incidence of IOH, defined as the average blood pressure of less than 65 mm Hg, was small, which is due to the minimally invasive surgery performed and the relatively short intervention duration. In the AKI patient group IOH was observed in 5.7% (6/106) of cases, in patients without AKI - in 4.9% (9/184) of cases; observed IOH did not affect AKI risk (RR = 1.1 [95%CI 0.5; 1.8], OR = 1.17 [95%CI 0.4; 3.2], p =0.79). The duration of hypotension was also small - the median time was 10 minutes [Q1-Q3: 10; 15]. No statistically significant difference was observed for the minimal MBP in the AKI patient group compared to those without AKI: 72 mm Hg [Q1-Q3: 68; 78] vs 73 mm Hg [Q1-Q3: 70; 78], p = 0.33. The intervention duration was comparable in AKI patient group and no AKI patient group (30 min [Q1-Q3: 20; 45] vs 25 min [Q1-Q3: 20; 35], p = 0.409).

3.2.3. PHPT related factors

From the analysis of AKI risk and pre-operative PTH level association the median PTH concentration in AKI patients was found to be significantly higher compared to that of the patients without AKI: 17.75 pmol/L [Q1-Q3: 12; 24.2] vs 13.8 pmol/L [Q1-Q3: 10.2; 19.6] respectively, p = 0.0004 (Figure 3.9). The ROC curve was obtained to assess preoperative PTH level impact on AKI probabilityFigure 3.20. The area under the obtained PTH level ROC curve was 0.625 [95%CI 0.56; 0.69], p = 0.0004. The PTH level cut-off point was 16.95 pmol/L. With the selected cut-off point, the Se was 0.679 [95% CI 0.61; 0.74], the Sp - 0.557 [95%CI 0.46; 0.65], SBA was 0.618, p<0.0001. Patients with baseline PTH levels greater than 16.95 pmol/L have a higher risk of AKI: RR=1.45 [95%CI 1.2; 1.8], OR=2.66 [95%CI 1.62; 4.3].

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Figure 3.10. Parathyroid adenoma size, weight and volume correlations with Spearman's test. Linear correlation estimation is given, the points indicate 95%CI.

Adenoma maximum size is of the greatest interest for the routine practice, since it cannot be easily detected by ultrasonography or CT. In AKI patients, the median parathyroid adenoma maximum size was greater than that of the patients without AKI: 20 mm [Q1-Q3: 10; 25] vs 15 mm [Q1-Q3: 10; 20] respectively, p= 0.0184 (Figure 3.11). The ROC curve was obtained to assess the parathyroid adenoma maximum size impact on the AKI probability - Figure 3.20. The area under the obtained parathyroid size ROC curve was 0.582 [95%CI 0.51; 0.65], p = 0.02. The adenoma maximum size cut-off point was 16.5 mm. With the selected cut-off the Se was 0.628 [95% CI 0.56; 0.7], the Sp – 0.547 [95%CI 0.45; 0.64], SBA – 0.588, p=0.0037. With an initial adenoma size of greater than 16.5 mm, the risk of AKI increased: RR=1.31 [95%CI 1.09; 1.59], OR=2.04 [95%CI 1.26; 2.6].

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PTH, pmol/l

Before After surgery surgery

Figure 3.12. Post-PTx PTH level dynamics with the Wilcoxon test. The medians, the first and third quartiles are given, the shape of the figures reflects the variable distribution.

Patients with high PTH levels had higher preoperative levels of both total (ρ=0.509 [95%CI 0.36; 0.63], p<0.0001) and ionized calcium (ρ=0.432 [95%CI 0.33; 0.52], p<0.0001) - Figure 3.13. With this, the total calcium level was closely correlated with pre-PTx PTH level compared to ionized calcium level, – р=0.0134.

Figure 3.13. Preoperative total and ionized calcium level correlations with PTH level with Spearman's test. The linear relationship estimation is provided, the points indicate 95% CI.

The mean total serum calcium level pre-operatively was slightly higher in AKI patient group: 2.83±0.29 mmol/L vs 2.71±0.22 mmol/L in the group of patients without

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AKI: 25% (13/52) vs 7.25% (7/69), respectively. Moderate/severe hypercalcemia had a statistically significant impact on the AKI risk: RR=1.91 [95%CI 1.22; 2.69], OR=4.28 [95%CI 1.39; 11.38], p=0.0092 - Figure 3.15.

n of observations

mild moderate+severe

Hypercalcemia

Figure 3.15. AKI incidence in patient groups with different preoperative total serum calcium levels.

No statistically significant difference was demonstrated in the median ionized calcium levels of AKI patients compared to those without AKI (1.47 mmol/L [Q1-Q3: 1.35; 1.54] vs 1.45 mmol/L [Q1-Q3: 1.36; 1.55] respectively, p=0.496) - Figure 3.14.

PTx led to ionized blood calcium level decrease on day 1 from 1.45 mmol/L [Q1- Q3: 1.35; 1.55, from 1.15 to 2.23] to 1.23 mmol/L [Q1-Q3: 1.16; 1.31, from 0.88 to 1.86], p<0.0001. However, no statistically significant association was demonstrated for ionized calcium decrease extent impact on the AKI probability (p = 0.3706). – Figure 3.16

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