Diagnostic threshold and performance of anion gap in screening for high anion gap metabolic acidosis.

INTRODUCTION: The anion gap (AG) is commonly used to screen for acid-base disorders. It was proposed that the cut-off for high anion gap metabolic acidosis (HAGMA) may be lower with current laboratory techniques, although modern laboratory equipment are still calibrated to familiar reference ranges established with earlier techniques. The appropriate cut-off for HAGMA is unclear. This study aimed to assess the performance of AG as a screening test for HAGMA and to determine the optimal diagnostic threshold of AG for HAGMA. METHODS: This was a retrospective analysis of a large, anonymised dataset extracted by computerised protocol from 2017 to 2019. All inpatients with blood samples taken for organic acids (lactate, ketone or salicylate) paired with a metabolic panel were included. The target condition was HAGMA secondary to elevated blood lactate, ketone and/or salicylate. Sensitivity for HAGMA was explored at various AG cut-off levels. RESULTS: Of 16,475 patients, 2,621 had organic acidosis. Median age was 65 years, and median estimated glomerular filtration rate was 70 mL/min/1.73 m2. With organic acidosis, the median AG was 23 (interquartile range [IQR] 20-29) mEq/L, while without organic acidosis, the median AG was 16 (IQR 14-19) mEq/L. The area under the curve-receiver operating characteristic of AG for HAGMA was 0.873. Desired sensitivity for HAGMA was set at ≥95%, and this was found with an AG threshold of ≥15 mEq/L (sensitivity 98.1%, specificity 34.0%). CONCLUSION: The recommended AG threshold value is ≥15 mEq/L with a high sensitivity for HAGMA. The AG should always be interpreted with the clinical context, and it should be repeated as the clinical picture evolves.

25-OH vitamin D threshold for optimal bone mineral density in elderly patients with chronic kidney disease.

Introduction: Vitamin D deficiency is common in chronic kidney disease (CKD) and is associated with lower bone mineral density (BMD), decreased muscle strength, and increased hip fracture risk. Guidelines have suggested targeting 25-OH vitamin D (25(OH)D) levels between 20 and 30 ng/ml. However, vitamin D metabolism is altered in CKD, and threshold levels for optimal BMD are unknown. Methods: We included 1097 patients with hip fractures. CKD was defined as estimated glomerular filtration rate <60 ml/min/1.73 m (Mucsi et al., Clin. Nephrol., 2005, 64(4), 288-294) and low BMD defined as T score ≤ -2.5 at femoral neck. We assessed the association of 25(OH)D with low BMD in patients with and without CKD: using the conventional threshold 25(OH)D < 30 ng/dl, as well as a new threshold. Results: CKD was present in 479 (44%) patients. Using a threshold of 25(OH)D < 30 ng/ml, there were no significant differences in patients with CKD and low BMD when compared to the other groups. We identified 27 ng/ml as a better threshold with the Youden index. Using 25(OH)D < 27 ng/ml as a threshold, 360 of 482 patients (74.7%) with low 25(OH)D had low BMD, compared to only 185/276 (67%) of patients with adequate vitamin D, p = 0.02, which was irrespective of the presence or absence of CKD. Furthermore, patients with CKD and 25(OH)D < 27 ng/ml had a higher odds ratio of mortality upon follow-up, 1.61, 95% CI: 1.08-2.39, compared to those with CKD and 25(OH)D ≥ 27 ng/ml. Conclusion: We find that 25(OH)D < 27 ng/ml is associated with low BMD in patients with and without CKD. Further prospective studies targeting vitamin D repletion to at least 27 ng/ml and the outcome of hip fractures will be useful to validate these findings.

Hip fractures in elderly patients with non-dialysis dependent chronic kidney disease: Outcomes in a Southeast Asian population.

ABSTRACT: Chronic kidney disease (CKD) causes bone and mineral disorders and alterations in vitamin D metabolism that contribute to greater skeletal fragility. Hip fracture in elderly is associated with significant morbidity and mortality. The aim of this study was to investigate the outcome of elderly patients with non-dialysis dependent CKD and hip fracture undergoing surgery.Retrospective study with IRB approval of patients above 65 years of age, with hip fractures admitted between June 2014 to June 2016 in a Southeast Asian cohort. Data collected included demographic variables and the haematological and biochemical parameters HBA1c, estimated glomerular filtration rate (eGFR), serum calcium, phosphorous, and 25(OH) Vitamin D. Co-morbidities investigated were ischemic heart disease, congestive heart failure, peripheral vascular disease, malignancy, chronic obstructive pulmonary disease, cerebro vascular accident, hypertension and hyperlipidaemia. All patients were followed up from index date to either death or June 1, 2018.Of the 883 patients, 725 underwent surgery and 334 had CKD. Death rates for CKD patients with hip fractures and those with normal renal function did not differ significantly [8.08% vs 6.54%, (HR= 1.33, 95% CI: 0.95, 1.86; P = .102)], whilst median hospital length of stay was significantly higher in CKD patients [10.5 vs 9.03 days (P = .003)]. Significant risk factors associated with higher risk of mortality in the elderly with hip fracture were male gender, age ≥80 years and serum albumin < 30 g/L (all, P < .0001).In summary, in elderly, non-dialysis dependent CKD patient with hip fracture we found that male gender, age ≥80 years, low serum albumin and eGFR < 30 mL/min/1.73 m2 were associated with higher risk of death. The hospital stay in the CKD group was also longer. Additional studies are needed to validate our findings.

Regional Citrate Anticoagulation for Continuous Renal Replacement Therapy - A Safe and Effective Low-Dose Protocol.

AIMS: Regional citrate anticoagulation (RCA) is the preferred mode of anticoagulation for continuous renal replacement therapy (CRRT). Conventional RCA-CRRT citrate dose ranges from 3 to 5 mmol/L of blood. This study explored the effectiveness of an RCA protocol with lower citrate dose and its impact on citrate-related complications. METHODS: This prospective observational study compared two RCA-CRRT protocols in the intensive care unit. RCA Protocol 1 used an initial citrate dose of 3.0 mmol/L while Protocol 2 started with 2.5 mmol/L. The citrate dose was titrated by sliding scale to target circuit-iCa 0.26-0.40 mmol/L. Calcium was re-infused post-dialyzer and titrated by protocol to target systemic-iCa 1.01-1.20 mmol/L. RESULTS: Two hundred RCA-CRRT sessions were performed (81 Protocol 1; 119 Protocol 2). The median age was 65.4 years and median APACHE-II score was 23. Citrate dose for Protocol 1 was significantly higher than Protocol 2 in the first 12 h. The circuit clotting rate was similar in both arms (Protocol 1: 9.9%; Protocol 2: 9.2%; P = 0.881). With Protocol 2, circuit-iCa levels were 2.42 times more likely to be on target (P = 0.003) while the odds of hypocalcaemia was 4.67 times higher with Protocol 1 (P < 0.001). There was a wider anion gap was noted with Protocol 1, which suggests a propensity for citrate accumulation with higher citrate exposure. CONCLUSION: The RCA protocol with a lower initial citrate dose of 2.5 mmol/L blood had less citrate-related complications with no loss of efficacy. A more precise RCA prescription at the start of treatment avoids unnecessary citrate exposure and improves safety.

Impact of simulation-based learning on immediate outcomes of temporary haemodialysis catheter placements by nephrology fellows.

AIM: Traditional apprenticeship model (AM) of teaching in invasive procedures such as temporary haemodialysis catheter (THDC) insertion can result in propagation of errors and complications. Simulation-based learning (SBL) offers standardization of skills and allows trainees to repeatedly practice invasive procedures prior to performing them on actual patient. METHODS: Retrospective cohort study of first-, second- and third-year Nephrology Fellows from a tertiary teaching hospital from September 2008 to September 2015. The intervention group (n = 9) received simulation training in ultrasound-guided THDC placement. The historical control group (n = 12) received training through traditional AM. The primary and secondary outcomes were the immediate complications and success rates of THDC insertion. RESULTS: A total of 2481 THDCs were placed in 1787 patients. Success rate of internal jugular THDC placement for AM vs. SBL Fellow was 99.8% versus 100% (P = 0.90), while the success rate for femoral THDC placement was 99.6% versus 99.2% (P = 0.53). SBL Fellows reported fewer overall peri-procedure complications (8.3% vs. 11.2%, P = 0.02) and mechanical complications (1% vs. 2.4%, P = 0.02) compared to AM Fellows. The rate of reported technical difficulty was similar (7.5% vs. 9.2%, P = 0.17). After adjusting for side and site of THDC placement, body mass index and laboratory indices, THDC inserted by AM Fellows were independently associated with increased overall peri-procedure complications (OR = 1.396, 95% CI: 1.052-1.854, P = 0.02) and mechanical complications (OR = 2.481, 95% CI: 1.178-4.810, P = 0.02). CONCLUSIONS: Simulation-based learning was associated with lower procedure related complications and should be an integral component in the teaching of procedural skills in Nephrology.