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F/55 Unexpected acidosis after operation (1)

Submitted on 5 December 2008
Dr CHAN King Chung Kenny
Department of Intensive Care, Pamela Youde Nethersole Eastern Hospital, Hong Kong
 
 
History of Present Illness 
F/55
Hx of Ca Breast -> mastectomy
HT, CHF (EF~30%), AV block with pacing
ADL independent
Presented with worsening vision due to glaucoma of left eye
 
Panretinal photocoagulation + posterior vitrectomy + lens excision
Early appointment in GA list (2/12)
Uneventful operation
Slow recovery from anaesthetic
To ICU for ventilation
Working Diagnoses:
  • Inadequate reversal
  • Slow recovery due to poor cardiac function
  • ?? Stroke -> no focal sign
  • ?? Hypoglycaemia -> H’stix 7.2
But unexpected Acidosis !!!
 
Na 137                             pH 6.856
K 5.2                                 pCO2 5.76
Ur 11                                 pO2 31.08
Cr 137                              HCO3 7.5
BE -26.2
 
What is the diagnosis? 
  
 

 

 
  
Diagnosis

Acetazolamide induced acidosis

Approach
Differential Diagnosis
  • Normochloraemic
    • Lactic acidosis
    • Ketoacidosis
    • Renal failure
    • Other organic acids
  • Hyperchloraemic
    • Urine loss of bicarbonate
    • Extra-renal loss
Drug History
  • Acetazolamide 250mg QID
  • Frusemide 20mg daily prn
  • Slow K 600mg BD
  • Perindopril 6mg daily
  • Aldactone 25mg daily
 
Cr 137 <- 91 (2/12 ago)
 
Progress
  • Acetazolamide stopped
  • Bicarbonate infusion started
  • BE reduced to -5.2 the next day
  • Extubated
  • Discharge in post-op day 2
  • BE -6.2 on discharge

 
Discussion 

 
Acetazolamide
  • Carbonic anhydrase inhibitor
  • Promote urinary bicarbonate loss and diuresis
Indications
  1. Glaucoma
  2. Fluid overload
  3. Epilepsy
  4. Metabolic alkalaemia.
  5. Periodic paralysis
  6. ? Mountain sickness
Dosage: up to 1g per day
Side effects
  • Hyperchloraemic acidosis
  • Caution in patient with renal impairment (eliminiated by kidney)
  • Renal stone
  • Slightly soluble in water
  • Aplastic anaemia
Prevalence of Acidosis
  • 27 Elderly on Acetazolamide
  • Mild acidosis (pH 7.29-7.31) – 4 (14.8%)
  • Moderate acidosis (pH 7.20-7.29) – 10 (37%)
  • Severe acidosis (pH < 7.15) – 1 (3.7%)
Comment from Ophthamologist: “We rarely need ICU bed for our patients.  This condition is the commonest reason for an unplanned post-op ICU bed”

  
Reference

Heller I, Halevy J, Cohen S, Theodor E. Significant metabolic acidosis induced by acetazolamide. Not a rare complication. Arch Intern Med. 1985 Oct;145(10):1815-7.