Lab Case 174 – Interpretation

A 64 year old man presents with fever and SOB.

He has a partially compensated respiratory alkalosis with 


high lactate

Risk stratification systems are useful for determining hospital discharge policies and antimicrobial therapy in patients with pneumonia, and identifying patients at risk of adverse outcomes.

Many scoring systems exist:


  •  confusion, urea >7, RR >30 , BP <90/60, age>65
  • scoring:  0-1 low risk, 2 mod risk,  >3 high risk (30% 30 day mortality)


  • confusion, O2 <90%, RR>30, BP<90/60
  • scoring: severe pneumonia is 2 or more



Causes of Respiratory Alkalosis
1. Central Causes (direct action via respiratory centre)
  • Head Injury
  • Stroke
  • Anxiety-hyperventilation syndrome (psychogenic)
  • Other ‘supra-tentorial’ causes (pain, fear, stress, voluntary)
  • Various drugs (eg analeptics, propanidid, salicylate intoxication)
  • Various endogenous compounds (eg progesterone during pregnancy, cytokines during sepsis, toxins in patients with chronic liver disease)
2. Hypoxaemia (act via peripheral chemoreceptors)
  • Respiratory stimulation via peripheral chemoreceptors
3. Pulmonary Causes (act via intrapulmonary receptors)
  • Pulmonary Embolism
  • Pneumonia
  • Asthma
  • Pulmonary oedema (all types)
4. Iatrogenic (act directly on ventilation)
  • Excessive controlled ventilation