Risk factors for thiazide-induced hyponatraemia.

BACKGROUND: Thiazide-induced hyponatraemia is common and potentially life threatening. In the absence of well-defined risk factors for this complication, guidelines for prescribing cannot be established. AIM: To examine whether a subgroup of patients is particularly susceptible to this complication. DESIGN: Retrospective case-control study. METHODS: We defined and recruited cases of symptomatic hyponatraemia that necessitated hospitalization from January 1996 to April 2002. Controls were selected from 8420 patients being prescribed thiazides and seen at the same institution during that period of time. RESULTS: There were 223 cases and 216 controls, with a median 115 days thiazide use. Cases were older than controls (76 +/- 9 vs. 66 +/- 13 years, p < 0.001) and lighter (52.3 +/- 10.3 vs. 63.4 +/- 3 kg, p < 0.001). By univariate analysis, serum potassium level, use of indapamide, elderly home institutionalization and physical immobility were risk factors for thiazide-induced hyponatraemia, but gender, duration of thiazide use, concomitant therapy with loop diuretics, angiotensin-converting enzyme inhibitors or non-steroidal anti-inflammatory drugs, and renal function were not. By stepwise logistic regression analysis, patient age, body weight and serum potassium were the only independent predictive factors. Each 10-year increment of age was associated with a two-fold increase in risk (hazards ratio 2.14, 95%CI 1.59-2.88). For a 5 kg increment in mass, there was a 27% decrease in odds ratio (odds ratio 0.77, 95%CI 0.68-0.87). One SD increase in serum potassium (0.84 mmol/l) was associated with a 63% decrease in risk (odds ratio 0.37, 95%CI 0.27-0.50; p < 0.0001). DISCUSSION: Hyponatraemia is a common problem after thiazide therapy. Extra caution and close monitoring are warranted when prescribing thiazides for elderly patients with low body mass.

Extrapolation of reciprocal creatinine plot is not reliable in predicting the onset of dialysis in patients with progressive renal insufficiency.

BACKGROUND: Reciprocal creatinine plot is often used to monitor patients with progressive renal insufficiency and to predict the onset of dialysis, although the latter practice has not been validated. OBJECTIVE: We examined whether extrapolating the reciprocal creatinine plot can predict the onset of dialysis. SETTING: Single centre study in the dialysis unit of a University teaching hospital. DESIGN: We studied 170 consecutive patients with progressive renal insufficiency referred to a single nephrology unit and subsequently dialysed. Reciprocal creatinine plot was constructed by all available serum creatinine values before dialysis (the 'definitive plot'). Four 'interim plots' were constructed for each patient by using serum creatinine below 400, 500, 600 and 700 micromol L(-1). Interim plots with at least five points and Pearson's r > 0.9 were analysed. The date of dialysis was predicted from the least squares linear regression formula and a target serum creatinine level cor- responding to estimated creatinine clearance of 7 mL min-1, at which dialysis was recommended. RESULTS: The median duration of observation was 25 months. After serum creatinine 500 micromol L(-1), the slope of the interim plot remained stable and extrapolation was possible in 117 patients (68.8%). However, the limits of agreement for predicting the onset of dialysis were wide (from -11.7 to +9.5 months). At this creatinine level, the onset of dialysis fell within 1 month of the predicted onset in only 41 patients (24.1%). The limits of agreement for prediction narrowed when time points of higher serum creatinine were included into the plot. However, nine patients (5.3%) required dialysis within 1 month at creatinine 600 micromol L(-1) and the dialysis was not predicted by the reciprocal creatinine plot. Target serum creatinine did not correlate with acute serum creatinine at which dialysis was started (r = 0.051, P = 0.51). A slower decline in renal function was associated with a higher prediction error (r = 0.212, P = 0.014). CONCLUSIONS: The onset of dialysis cannot be predicted by extrapolation of the reciprocal creatinine plot because of individual variation in the renal function that require dialysis. Dialysis would be almost imminent in some patients by the time serum creatinine reaches a level that allows accurate construction and extrapolation of a plot.

Unusual muscle pain in two patients with diabetic renal failure.

We report on two patients with diabetic muscle infarct, a painful musculoskeletal disorder complicating longstanding diabetes with established microangiopathy. Both patients had renal failure that was treated by dialysis. The underlying pathophysiological process was considered to be an arterial vascular event mediated through ischaemia-reperfusion injury. Clinicians should be alert to this condition. T2-weighted magnetic resonance imaging was valuable in establishing the diagnosis.