Background: Blood gas analyses are used to identify acid-base and respiratory disturbances. Blood gas abnormalities can be first signs of serious underlying disease.
Case description: An 82-year old women with chronic kidney disease (eGFR 35 ml/min/1.73m2) and rheumatoid arthritis was admitted to the geriatric ward due to a urinary tract infection and bloody diarrhea. She repeatedly had a low oxygen saturation, although without symptoms. Capillary blood gas analysis was evidently disturbed (pH 6.96, pCO2 9.3 kPa, lactate 8.4 mmol/l), and led to consultation of the intensivist. Careful physical examination demonstrated that the patients' hands had blue discoloration, typical for Raynaud's phenomenon. Arterial blood gas demonstrated normal results.
Conclusion: Capillary blood gas analysis is less reliable when peripheral circulation is disturbed. When the results are aberrant, it is important to distinguish between peripheral vascular disease and diminished systemic circulation. Arterial blood gas analysis can be used to support the diagnosis.