Serum anion gap revisited: a verified reference interval for contemporary use.

BACKGROUND: The anion gap (AG) is often used to evaluate acid-base disorders. The reference interval for normal AG is used to differentiate between raised (gap) or normal AG (non-gap) acidosis. Historically accepted AG values may not be valid with the evolution of modern analytical techniques and the reference interval requires revalidation. AIMS: To determine the reference interval for AG based on current laboratory techniques. METHODS: During a health-screening exercise, 284 participants with no major illnesses volunteered surplus blood for analysis. The samples were tested in an internationally accredited clinical laboratory. AG was calculated by [Na+ ] - [Cl- ] - [HCO3 - ] and AGK by [Na+ ] + [K+ ] - [Cl- ] - [HCO3 - ]. The reference interval was determined at 2.5th-97.5th percentiles. Analysis was further undertaken for a subcohort of 156 individuals with no suboptimal health indicators. RESULTS: Median age was 35 years, body mass index 23.4 kg/m2 and the glomerular filtration rate was 106 mL/min/1.73 m2 . Median AG was 13 mmol/L and the reference interval for normal AG is 10-18 mmol/L with a 99% level of confidence. Statistically significant differences in AG were detected for sex, race, obesity and serum albumin, but the difference was 1 mmol/L between subgroups. The reference interval was the same for the sub-cohort of 156 individuals. Median AGK was 17.7 mmol/L and reference interval was 14.6-22.5 mmol/L. CONCLUSIONS: The AG reference interval of 10-18 mmol/L is valid for laboratories with similar reference intervals for electrolytes. Lower values expected with current laboratory techniques were not observed. The median AG of 13 mmol/L may be used to differentiate gap acidosis, non-gap acidosis or mixed acid-base disorders.

Regional citrate anti-coagulation dose titration: impact on dose of continuous renal replacement therapy.

BACKGROUND: Regional citrate anti-coagulation (RCA) is the recommended anti-coagulation for continuous renal replacement therapy (CRRT). Citrated replacement fluids provide convenience but may compromise effluent delivery when adjusted to maintain circuit ionised calcium levels (circuit-iCa). This study aims to evaluate the effect of RCA titration on the delivered CRRT effluent dose. METHODS: This prospective observational study evaluated patients on RCA-CRRT in continuous veno-venous hemodiafiltration mode. Citrated replacement fluid was titrated to target circuit-iCa 0.26-0.40 mmol/L. Patients were then stratified into 'reduced-dose' who required citrate down-titration and 'stable-dose' who did not. RESULTS: Data from 200 RCA-CRRT sessions were collected. The reduced-dose RCA group (n = 114) had higher median initial citrate dose (3.00 vs 2.50; P < 0.001) but lower time-averaged dose (2.49 vs 2.60; P < 0.001). In addition, median prescribed effluent dose was 33.3 mL/kg/h (28.6-39.2) but median delivered effluent dose was significantly lower at 29.9 mL/kg/h (25.4-36.9; P < 0.001). Mortality was higher in the reduced-dose RCA group (39.5% vs 25.6%; P = 0.022) and in patients with delivered-to-prescribed effluent dose ratio of < 0.9 vs ≥ 0.9 (51.3% vs 29.2%; P = 0.014). CONCLUSION: RCA titration can significantly impact delivered CRRT effluent dose. Measures should be taken to address the CRRT dose deficit and prevent poor outcomes due to inadequate dialysis.

Evaluation of factors associated with bleeding following haemodialysis catheter-related procedures and the risk with anti-platelet agents.

BACKGROUND: Bleeding is a potential complication following haemodialysis catheter-related procedures. Besides uraemia, bleeding risk is perceived to be even higher in patients receiving antiplatelets. This study aims to evaluate the risk factors for bleeding following dialysis catheter-related procedures. METHODS: This is a secondary analysis of a single-centre, prospective cohort study between March 2019 and June 2020. Potential risk factors for bleeding were collected, including use of antiplatelets and anticoagulants, serum urea and haematological results. Patients were observed closely for external bleeding following haemodialysis catheter-related procedures. RESULTS: From 413 patients screened, 250 were recruited. Of these, 177 underwent dialysis catheter insertion (157 tunnelled and 20 non-tunnelled) while 73 had dialysis catheter removed (35 tunnelled and 38 non-tunnelled). One hundred and four patients (41.6%) were on a single anti-platelet agent, of whom 75 (30.0%) were on aspirin and 29 (11.6%) had clopidogrel alone. Twenty-nine patients (11.6%) were on both aspirin and clopidogrel.There were 36 episodes (14.4%) of bleeding. The risk of bleeding was not significantly higher with the use of aspirin alone (odds ratio = 0.85, 95% CI: 0.36-2.02, p = 0.709), clopidogrel alone (odds ratio = 1.04, 95% CI: 0.31-3.49, p = 0.953) and both aspirin and clopidogrel (odds ratio = 0.95, 95% CI: 0.28-3.25, p = 0.938). In a multivariate analysis, none of the known bleeding risk factors had a statistically significant association with bleeding. CONCLUSIONS: Overall, the use of antiplatelet agents was not associated with an increased risk of bleeding.

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.

Ipsilateral vocal fold paralysis: An unusual complication of internal jugular tunnelled dialysis catheter insertion.

BACKGROUND: Central venous catheters are extensively used in critical care units and in dialysis centres to gain access to the blood stream for the purpose of invasive monitoring, drug administration, parenteral nutrition and to perform renal replacement therapy. One of the common areas of central venous catheter insertion is right internal jugular vein due to its anatomical continuity with the superior vena cava. The complication rates of central venous catheter insertion can be more than 15%, including early and late complications. CASE REPORT: We present an unusual complication of recurrent laryngeal nerve palsy, leading to right vocal fold paralysis, following insertion of a right internal jugular tunnelled dialysis catheter. The vocal fold paralysis improved over next 8 months with conservative management alone. CONCLUSION: This case illustrates an unusual complication of central venous catheter insertion and the importance of recognizing the possibility of such complications, to prevent them from happening and also to manage them appropriately.