Lab Case 2

50 year old man with Motor Neuron Disease presents with acute onset of thoracic back pain.

Vitals :

BP 230/130

PR 120/min

Profuse sweating

GCS 11

Describe and Interpret the following blood gas:

pH 7.122                                                   Na 145

pCO2 108                                                 K 3.7

pO2 171                                                    Cl 101

HCO3 38                                                   Glu 9.5

BE 3.2                                                        Lactate 0.8

Hb 183



One thought on “Lab Case 2

  1. Issues from stem:
    MND – need to consider severity, stage of disease, advanced directives, previous established ceilings of care.
    Marked hypertension with back pain and altered concious level
    ? central pathology – SOL, SAH, bleed
    ? vascular event esp. dissection
    ? hypertensive crisis
    ? Myocardial ischaemia +/- pulm odema

    pH 7.122 Severe acidaemia – raised pCO2 & raised HCO –> primary resp acidosis
    pCO2 108 – significant hypercarbia likely contributing to altered GCS
    pO2 171 – hypoxaemia not cause of decreased GCS likely on supplemental oxygen, unable to calculate A-a gradient without FiO2
    HCO 38 – alkalosis – expected HCO for pCO2 if acute pCO2 raised expected HCO is ~31 (10:1 rule) if chronic expected HCO ~51 – actual HCO between the two so likely acute on chronic especially given MND and acute deterioration
    Hb 183 – elevated – ?haemoconcentration ? polycythaemia
    Na 145 – normal with normal glucose (nil further correction required)
    K 3.7 – low normal – adjusting for pH actual K is ~2.3 anticipate correction to be required as acidosis resolves
    Cl 101 – normal
    Glu – normal – not cause of decreased GCS
    Normal lactate
    Anion gap = 6

    Critical unwell patient with likely acute on chronic resp failure and hypertensive emergency, DDx as above.
    Treat reversible causes of resp depression e.g opiates / benzos.
    Ventilatory support may be not be appropriate pending disease severity, advance directives.
    If IPPV considered apppropraite avoid depolarising muscle relaxants for RSI.

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