metformin overdose dr. ts au pyneh 16 feb 2005 toxicology case presentation m/56 unemployed and...
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Metformin overdose
Dr. TS Au
PYNEH
16 Feb 2005
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Toxicology case presentation
M/56 unemployed and divorcedHx of DM, HT, depression FU in GPAttempted suicide by taking >100 tablets of diabetmin 500 mg (metformin) before 3 pmSuicidal notes writtenDeveloped repeated vomiting and diarrhoea since thenSent to AED at 18:33
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Triage and Ix
BP 198/54
P 102 /min
SpO2 100% (RA) RR 22/min
Temp 36.4℃Hemostix = 13.0
ECG: sinus rhythm 95/min, normal QRS
P/E: dehydrated
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Progress in AED
Given activated charcoal 50 g orally
IV NS 500 ml Q8H
BP/P GCS all along stable
Last BP 160/84, P 78 /min
Medical contacted, suggested admitted to general ward
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Arterial blood gases
1st 2nd
pH 7.248 7.223
pCO2 4.70 4.44
pO2 14.15 16.11
HCO3 15.0 13.4
BE -11.2 -13.1
Metabolic acidosis with respiratory
compensation
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Blood tests
ABG: pH 7.248 pCO2 4.70 HCO3 15.0 BE -11.2
RFT: Na 144 K 4.6 Cl 108 Cr 160
Glucose 12.4
Anion gap:
144 – 108 – 15 = 21
Anion gap metabolic acidosis
Lactate = 9.07 mmol/L
(N : 0.3 – 1.3)
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Progress
Transferred to ICU after first blood tests
Developed ARF
RFT D1 D3 D9 D15 D17
Cr 160 360 904 152 119
Put on continuous venovenous haemofiltration (CVVH)
Improving trend for acidosis and RFT
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Outcome
Transfer out to general ward on D3
Continue renal support by HD in medical ward
Cr back to normal on D17
Psychiatric assessment
Refused psychiatric ward admission
Home on D20
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Metformin overdose
Metformin – common biguanide used as an OHA
Mechanism of action:
↓hepatic gluconeogenesis MAJOR +
↑peripheral glucose utilization
did not lower blood glucose unless other OHA coingested (sulfonylurea)
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Anion gap metabolic acidosisMUDPILESM – methanolU – uraemia D – DKA / AKA / SKAP – paraldehyde / phenformin/ metforminI – isoniazid / ironL – lactate E – ethylene glycolS – salicylate
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Toxicity of metformin
Lactic acidosis esp in patients with renal impairment
GI effects: anorexia, vomiting and diarrhoea, abdominal pain
Rarely hypoglycemia
Fulminant GI distress leading to ARF, which↑ lactic acidosis
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Management
GI decontamination: activated charcoal for early presentation
Antidote for metabolic acidosis: sodium bicarbonate
Supportive care for refractory acidosis and ARF: Hemodialysis
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Learning points
Activated charcoal may not be justified as there may be persistent vomiting
Patient should be admitted to ICU right away
? Aggressive use of NaHCO3
? initiated in AED after blood taken
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