Case report

Acid-base balance disorders – case histories


Case 1

Ms M.M., 72 years old, treated for a long time for chronic obstructive lung disease, now admitted for dyspnoea. Reported to have been febrile and coughing for the last three days.

Admission Astrup

pH 7.325
pCO2 7.42 kPa
pO2 6.42 kPa
HCO3 30.1 mM
BE – 7.2 mM
  • What type of ABB disorder can be seen in this patient?
  • Recall the mechanisms of control of breathing.
  • What pH of urine would you expect in this patient?
  • Explain the mechanism of bicarbonate re-absorption in the kindneys.

Patient M.M. was administered oxygen (by mask, 4L/min) to alleviate nocturnal dyspnoea. After an hour dyspnoea disappeared, patient became, however, confused and sleepy. The result of arterial Astrup was as follows:

pH 7.210
pCO2 9.86 kPa
pO2 11.2 kPa
HCO3 31.0 mM
BE – 7.9 mM
  • How would you explain the extreme rise in pCO2?
  • Would you administer sodium bicarbonate in this case?

Upon standard antibiotic and bronchodilation treatment the patient’s state improved in 10 days. The final Astrup result was:

pH 7.45
pCO2 3.9 kPa
pO2 9.2 kPa
HCO3 27.0 mM
BE +3.0 mM

Case 2

34 year old woman was operated for acute thrombotic occlusion of mesenteric vein and most of the intestine was resected. Only 70 cm of proximal jejunum was left – jejunostomy was performed. The patient afterwards lost weight – from 55 kg to 43 kg within one month – produced less than 0.5 liters of urine per day, her wound became dehiscent. She was losing more than 4 liters of fluid through the jejunostomy. Basic examination suggested deep dehydration and malnutrition.

Lab results: Na=124 mM, K = 3.9 mM, Cl=69 mM… Astrup:

pH 7.550
pCO2 7.2 kPa
pO2 7.7 kPa
HCO3 42mM
BE +18 mM
  • What kind of ABB disorder is this? What is the probable cause?
  • What would be the appropriate treatment?

Case 3.

68 year old K.M., homeless, was admitted unconscious. As reported by the police he was found in a park. Physical examination shows no gross pathology, except deepened breathing, 20 breaths per minute.

Lab results: Na 141 mM, K = 5.8 mM, Cl = 103 mM, Glycaemia 7.4 mM, Urea 6.98 mM, Creatinin 114 mM, ALT 19.5 mkat/l, AST 25.3 mkat/l

Urine: pH 4.5, otherwise normal (negative for protein, glucose, ketone bodies)


pH 7.010
pCO2 2.1 kPa
pO2 12.2 kPa
HCO3 11.0 mM
BE – 16 mM
  • Look at the lab results, decide which of these are normal and which abnormal. What state are they pointing to?
  • What type of ABB disorder is this? Explain the hyperpnoea.
  • Calculate anion gap. Which substances can be responsible for the increased AG?
  • What then could be the cause for the patient’s state?

Toxicology was positive for ethyleneglycol.

Case 4.

26 year old man (65kg) was admitted with severe head injury after a car accident. Artificial ventilation was started with 40% oxygen, tidal volume 600 mL, breathing frequency of 18 per minute.

Astrup result after 30 minutes of this ventilation regime was as follows:

pH 7.490
pCO2 1.86 kPa
pO2 16.2 kPa
HCO3 24 mM
BE +6.8 mM
  • Explain the type of ABB disorder.
  • What would be the treatment?