Metformin-induced lactic acidosis: a case series

<p>Abstract</p> <p>Introduction</p> <p>Unlike other agents used in the treatment of type 2 diabetes mellitus, metformin has been shown to reduce mortality in obese patients. It is therefore being increasingly used in higher doses. The major concern of many physicians is a possible risk of lactic acidosis. The reported frequency of metformin related lactic acidosis is 0.05 per 1000 patient-years; some authors advocate that this rate is equal in those patients not taking metformin.</p> <p>Case presentation</p> <p>We present two case reports of metformin-associated lactic acidosis. The first case is a 77 year old female with a past medical history of hypertension and type 2 diabetes mellitus who had recently been prescribed metformin (3 g/day), perindopril and acetylsalicylic acid. She was admitted to the emergency department two weeks later with abdominal pain and psychomotor agitation. Physical examination revealed only signs of poor perfusion. Laboratory evaluation revealed hyperkalemia, elevated creatinine and blood urea nitrogen and mild leukocytosis. Arterial blood gases showed severe lactic acidemia. She was admitted to the intensive care unit. Vasopressor and ventilatory support was initiated and continuous venovenous hemodiafiltration was instituted. Twenty-four hours later, full clinical recovery was observed, with return to a normal serum lactate level. The patient was discharged from the intensive care unit on the sixth day. The second patient is a 69 year old male with a past medical history of hypertension, type 2 diabetes mellitus and ischemic heart disease who was on metformin (4 g/day), glycazide, acetylsalicylic acid and isosorbide dinitrate. He was admitted to the emergency department in shock with extreme bradycardia. Initial evaluation revealed severe lactic acidosis and elevated creatinine and urea. The patient was admitted to the Intensive Care Unit and commenced on continuous venovenous hemodiafiltration in addition to other supportive measures. A progressive recovery was observed and he was discharged from the intensive care unit on the seventh day.</p> <p>Conclusion</p> <p>We present two case reports of severe lactic acidosis most probably associated with high doses of metformin in patients with no known contraindications for metformin prescription. In both patients no other condition was identified to cause such severe lactic acidosis. Although controversial, lactic acidosis should be considered in patients taking metformin.</p

A comparative assessment of two conservative methods for the diagnosis of catheter-related infection in critically ill patients

Purpose: To assess the utility of two in situ techniques, differential time to positivity (DTP) and semiquantitative superficial cultures (SQSC) for diagnosing catheter-related bloodstream infection (CR-BSI) in critically ill adults. Methods: This was a prospective cohort study in patients with suspected CR-BSI arising from a short-term arterial catheter (AC) or a central venous catheter (CVC). On suspicion of CR-BSI, devices were removed. Blood, skin, catheter tip and hub cultures were taken. Infection rates were compared against the diagnosis of CR-BSI using matched tip and blood cultures. Results: Of 120 episodes of clinically suspected CR-BSI in 101 patients examined, 9 (7.5 %) were confirmed as CR-BSI. Validity values (95 % CI) for the diagnosis of CR-BSI arising from both AC and CVC for DTP were: sensitivity 44 % (15-77 %), specificity 98 % (93-100 %), positive predictive value (PPV) 67 % (24-94 %), negative predictive value (NPV) 96 % (90-98 %), positive likelihood ratio (LR+) 25 (5-117), negative likelihood ratio (LR-) 0.6 (0.3-1.0), diagnostic odds ratio (DOR) 44 (7-258), and accuracy 94 % (92-98 %). Validity values (95 % CI) for SQSC were: sensitivity 78 % (41-96 %), specificity 60 % (50-69 %), PPV 14 % (6-26 %), NPV 97 % (89-99 %), LR+ 1.9 (1.0-2.3), LR- 0.4 (0.1-1.3), DOR 5.1 (1.1-19), and accuracy 61 % (51-69 %). DTP combined with SQSC improved sensitivity and NPV to 100 % whilst the DOR increased to 25.8 (95 % CI 3-454). Conclusions: CR-BSI can be ruled out by undertaking DTP and SQSC concurrently for both ACs and CVCs with 100 % sensitivity and NPV

Metformin and lactic acidosis: cause or coincidence? A review of case reports

Objective. Metformin has been associated with the serious side-effect lactic acidosis. However, it remains unclear whether the use of metformin was a cause or a coincidence in lactic acidosis. Design. A literature search of the Index Medicus (1959-66) and of the databases Embase, Medline, Medline Express (1966-99) was performed using the keywords metformin, biguanides and lactic acidosis. All articles of cases with metformin-induced lactic acidosis (MILA) were cross-referenced. Subjects. Cases were included for analysis if they met the following criteria: serum pH less than or equal to7.35, lactate concentration greater than or equal to5 mmol L-1. Intervention. A forum of six experts in intensive care medicine independently categorized the cases in MILA unlikely (score 0), possible MILA (score 1) or probable MILA (score 2). Main outcome measures. Statistical analysis included the paired interobserver agreement (kappa) and multivariate regression analysis. Results. Of 80 reported cases, 33 were excluded because of insufficient quality. The forum scores of the remaining 47 cases were distributed normally with a mean score of 7 (range 2-10). The kappa-value was 0.041 (SD = 0.24, range -0.514, 0.427). Neither lactate concentration nor mortality correlated with serum metformin concentrations. Conclusions. Given the low interobserver agreement and the lack of any relationship between metformin levels and outcome parameters, the concept that there is a simple, causal relationship between metformin use and lactic acidosis in diabetic patients has to be reconsidered