Clinical factors associated with hyponatremia correction during treatment with oral Urea.

BACKGROUND AND HYPOTHESIS: Oral urea is being used more commonly to treat hyponatremia, but factors contributing to the correction rate are unknown. We hypothesized that clinically relevant factors can be identified to help guide hyponatremia correction with oral urea. METHODS: Retrospective study in two university hospitals including hospitalized patients with hyponatremia (plasma sodium < 135 mmol/L) treated with oral urea. Linear mixed-effects models were used to identify factors associated with hyponatremia correction. Rates of overcorrection, osmotic demyelination and treatment discontinuation were also assessed. RESULTS: We included 161 urea treatment episodes in 140 patients (median age 69 years, 46% females, 93% syndrome of inappropriate antidiuresis). Oral urea succeeded fluid restriction in 117 treatment episodes (73%), was combined with fluid restriction in 104 treatment episodes (65%) and was given as only treatment in 27 treatment episodes (17%). A median dose of 30 grams/day of urea for 4 days (interquartile range 2-7 days) increased plasma sodium from 127 to 134 mmol/L and normalized hyponatremia in 47% of treatment episodes. Older age (ß 0.09, 95%CI 0.02 to 0.16), lower baseline plasma sodium (ß -0.65, 95%CI -0.78 to -0.62), and higher cumulative urea dose (ß 0.03, 95%CI -0.02 to -0.03) were independently associated with a greater rise in plasma sodium. Concurrent fluid restriction was associated with a greater rise in plasma sodium only during the first 48 h of treatment (ß 1.81, 95%CI 0.40 to 3.08). Overcorrection occurred in 5 cases (3%), no cases of osmotic demyelination were identified, and oral urea was discontinued in 11 cases (11%) due to side-effects. CONCLUSION: During treatment with oral urea, older age, higher cumulative dose, lower baseline plasma sodium and initial fluid restriction are associated with a greater correction rate of hyponatremia. These factors may guide clinicians to achieve a gradual correction of hyponatremia with oral urea.

Role of knowledge and reasoning processes as predictors of resident physicians' susceptibility to anchoring bias in diagnostic reasoning: a randomised controlled experiment.

BACKGROUND: Diagnostic errors have been attributed to reasoning flaws caused by cognitive biases. While experiments have shown bias to cause errors, physicians of similar expertise differed in susceptibility to bias. Resisting bias is often said to depend on engaging analytical reasoning, disregarding the influence of knowledge. We examined the role of knowledge and reasoning mode, indicated by diagnosis time and confidence, as predictors of susceptibility to anchoring bias. Anchoring bias occurs when physicians stick to an incorrect diagnosis triggered by early salient distracting features (SDF) despite subsequent conflicting information. METHODS: Sixty-eight internal medicine residents from two Dutch university hospitals participated in a two-phase experiment. Phase 1: assessment of knowledge of discriminating features (ie, clinical findings that discriminate between lookalike diseases) for six diseases. Phase 2 (1 week later): diagnosis of six cases of these diseases. Each case had two versions differing exclusively in the presence/absence of SDF. Each participant diagnosed three cases with SDF (SDF+) and three without (SDF-). Participants were randomly allocated to case versions. Based on phase 1 assessment, participants were split into higher knowledge or lower knowledge groups. MAIN OUTCOME MEASUREMENTS: frequency of diagnoses associated with SDF; time to diagnose; and confidence in diagnosis. RESULTS: While both knowledge groups performed similarly on SDF- cases, higher knowledge physicians succumbed to anchoring bias less frequently than their lower knowledge counterparts on SDF+ cases (p=0.02). Overall, physicians spent more time (p<0.001) and had lower confidence (p=0.02) on SDF+ than SDF- cases (p<0.001). However, when diagnosing SDF+ cases, the groups did not differ in time (p=0.88) nor in confidence (p=0.96). CONCLUSIONS: Physicians apparently adopted a more analytical reasoning approach when presented with distracting features, indicated by increased time and lower confidence, trying to combat bias. Yet, extended deliberation alone did not explain the observed performance differences between knowledge groups. Success in mitigating anchoring bias was primarily predicted by knowledge of discriminating features of diagnoses.