01 Dec 08

Metformin-associated lactic acidosis in intensive care unit

Posted in Acid-Base disorders at 0:59 by Laci

By N Peters, N Jay, A Cravoisy, D Barraud, L Nace, P-E Bollaert and S Gibot

Critical Care 2008,12:R14

Metformin-associated lactic acidosis (MALA) is a classical side effect of metformin and is known to be a severe disease with a high mortality rate. MALA’s treatment by dialysis is controversial and is subject to many case reports. We aimed to assess the prevalence of MALA in a 16-bed, university-affiliated, intensive care unit (ICU), and the effect of dialysis on patients’ outcome.

Over a 5-year period, we retrospectively identified all patients who either were admitted into the ICU with metformin as a usual medication, or who attempted suicide by metformin ingestion. Within this population, we selected patients presenting with a lactic acidosis, thus defining MALA, and described their clinical and biological features.

Metformin-associated lactic acidosis accounted for 0.84% of all admissions during the studied period (30 MALA admissions over 5 years) and was associated with a 30% mortality rate. The only factors associated with a fatal outcome were the reason for admission in the ICU and the initial prothrombin time. Although patients who went on to hemodialysis had higher illness severity scores, as compared to those who were not dialyzed, the mortality rates were similar between the two groups (31.3% versus 28.6%).

Metformin-associated lactic acidosis can be encountered in the ICU several times a year and still remains a life-threatening condition. Treatment is mostly restricted to supportive measures, although hemodialysis may possess a protective effect.

05 Oct 08

Peri-operative iv fluids in diabetic patients – don’t forget the salt

Posted in Acid-Base disorders, Glycemic control at 13:45 by Laci

By A K Simpson, N Levy and G M Hall

Anaesthesia 2008;63:1043-1045

It is estimated by the International Diabetes Federation that 246 million adults worldwide have diabetes mellitus and the figure is expected to reach 380 million by 2025. Anaesthetists will be involved in the care of more diabetic patients as they present in increasing numbers for surgery as a result of the complications of diabetes. The cornerstone of metabolic control in the peri-operative period, except for Type II diabetics undergoing minor surgery, is the administration of intravenous (iv) glucose with potassium chloride and a variable insulin infusion. Standard anaesthetic and surgical texts recommend the use of 5% or 10% glucose at a rate of 125–83 ml.h−1. This corresponds to practice in nine out of 11 acute hospitals in the East Anglia region as shown by the authors’ recent audit (unpublished results). It is likely, therefore, that this regimen is common nationally.

21 Sep 08

Physiological effects of hyperchloraemia and acidosis

Posted in Acid-Base disorders, Fluid management at 21:36 by Laci

By J M Handy and N Soni

Br. J. Anaesth. 2008;101:141-150

The advent of balanced solutions for i.v. fluid resuscitation and replacement is imminent and will affect any specialty involved in fluid management. Part of the background to their introduction has focused on the non-physiological nature of ‘normal’ saline solution and the developing science about the potential problems of hyperchloraemic acidosis. This review assesses the physiological significance of hyperchloraemic acidosis and of acidosis in general. It aims to differentiate the effects of the causes of acidosis from the physiological consequences of acidosis. It is intended to provide an assessment of the importance of hyperchloraemic acidosis and thereby the likely benefits of balanced solutions.

21 Jul 08

(Ab)normal saline and physiological Hartmann’s solution: a randomized double-blind crossover study

Posted in Acid-Base disorders, Fluid management at 14:17 by Laci

By F Reid, D N Lobo, R N Williams, B J Rowlands and S P Allison

Clin Sci 2003;104:17-24

In this double-blind crossover study, the effects of bolus infusions of 0.9% saline (NaCl) and Hartmann’s solution on serum albumin, haematocrit and serum and urinary biochemistry were compared in healthy subjects. Nine young adult male volunteers received 2-litre intravenous infusions of 0.9% saline and Hartmann’s solution on separate occasions, in random order, each over 1h. Body weight, haematocrit and serum biochemistry were measured pre-infusion and at 1h intervals for 6h. Biochemical analysis was performed on pooled post-infusion urine. Blood and plasma volume expansion, estimated by dilutional effects on haematocrit and serum albumin, were greater and more sustained after saline than after Hartmann’s solution (P<0.01). At 6h, body weight measurements suggested that 56% of the infused saline was retained, in contrast with only 30% of the Hartmann’s solution. Subjects voided more urine (median: 1000 compared with 450ml) of higher sodium content (median: 122 compared with 73mmol) after Hartmann’s than after saline (both P = 0.049), despite the greater sodium content of the latter. The time to first micturition was less after Hartmann’s than after saline (median: 70 compared with 185min; P = 0.008). There were no significant differences between the effects of the two solutions on serum sodium, potassium, urea or osmolality. After saline, all subjects developed hyperchloraemia (>105mmol/l), which was sustained for >6h, while serum chloride concentrations remained normal after Hartmann’s (P<0.001 for difference between infusions). Serum bicarbonate concentration was significantly lower after saline than after Hartmann’s (P = 0.008). Thus excretion of both water and sodium is slower after a 2-litre intravenous bolus of 0.9% saline than after Hartmann’s solution, due possibly to the more physiological [Na+]/[Cl-] ratio in Hartmann’s solution (1.18:1) than in saline (1:1) and to the hyperchloraemia caused by saline.

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