A 73 years old female presents to ED at 0800 in morning with c/o multiple episodes of PR bleed with associated abdominal pain overnight. Last episode was about 2 hours ago. She has T2DM, HTN, and hypothyroidism and is on thyroxine, ramipril and metformin.
OE: looks pale, peripherally cold, HR 120, BP 90 systolic. Temp 33 C. Her VBG was as followed on arrival.
- PH 7.21 ( 7.35 – 7.45)
- PCO2 24 ( 35 – 45 )
- HCO3 12 (22 – 28)
- Cl 100 ( 95 – 110)
- Na 134 ( 135 – 145)
- K 3.4 ( 3.5 _ 4.5)
- lactate 13
- Hb 159
- Creat 140
Questions:
- What is the primary acid base disorder? Calculate compensation.
- What are 3 main abnormalities on this VBG.?
- What is the likley Cause of patients very high lactate in context of presentation and medical background?
Answers:
- Metabolic Acid. High Anion gap ( 134 – 100 +12) = 22. Adequately compensated . Expected CO2 : 1.5 X HCO3 + 8 = 24.
- HAGMA, Very high Lactate, increased Creatinine.
- The most likley cause in this case given above clinical picture is ” Ischaemic Bowel ” however very high lactate level is contributed by metformin in the presence of renal impairment and hypo-perfusion from ischaemic gut and volume loss overnight.
Metformin Associated lactic Acidosis ( MALA)
Metformin is associated with lactic acidosis. Some argue that it is because of underlying DM , renal failure and it does not cause acidosis by itself, But there have been proved cases of lactic acidosis from metformin overdose and in the absence of risk factors.
Risk factors:
- Advanced age
- High dose of metformin
- Renal Failure
- Hypoxia
- sepsis
- dehydration
- shock
- alcohol intake
Above patient was in shock from hypoperfuison, dehydration, ischaemic gut and being on metformin in the presence of renal failure tipped her over and led to significant acid base disorder.