Acid-base balance disorders – case histories
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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)
Astrup:
| 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?