Lab case 338 interpretation

Question 1:

PH = 7.457, that is mild alkalaemia.

PCO2 = 27 (<40), so we have respiratory alkalosis.

Next, we look for the compensation. For acute respiratory alkalosis. HCO3 is expected to drop by 2 for every 10 pCO2 less than 40. Accordingly, expected HCO3 for this patient should be:  24 – (13 x 0.2) = 21.4 mmol/L. HC)3 here is 19. That is very close, however we can argue that this patient can have additional metabolic acidosis as her HCO3 is lower than the expected.

Since we might have additional metabolic acidosis, then we should calculate the anion gap. Here, AG = 130 – (99 + 19) = 12, that is normal. Accordingly, even if we have additional metabolic acidosis it will be NAGMA.

Other abnormal findings in this case:

Na = 130 mmol/L. Although this is mild hyponatraemia, but hyponatraemia in association with sepsis is known to be associated with increased morbidity and mortality. The cause of this phenomenon is unknown.

Lactate = 2.7 mmol/L, mild hyperlactataemia. That is a sign of poor tissue perfusion in sepsis.

Creatinine = 142 umol/L. that is impaired kidney function.

Final conclusion is mild acute respiratory alkalosis (Possibly associated with NAGMA) + mild hyponatraemia and impaired kidney function.

Next we are going to look at the causes of acute respiratory alkalosis, for that we use the mnemonic CHAMPS.

  • C = CNS causes
  • H = Hypoxia (pulmonary causes).
  • A = Anxiety or Pain
  • M = Mechanical ventilation
  • P = Pregnancy/Progesterone
  • S = Salicylate or sepsis.

Sepsis was the cause for this patient.


 Question 2: 

There is only one study in the literature looking at patients with fever and rigor vs patients with fever without rigor ( Tal et al .1997). According to this study, there were significantly greater positive blood cultures in patients with rigors (15%) compared to those without rigors (6%).

Although the most common causes of rigors in the community are:

  • Pneumonia
  • Acute cholangitis/ biliary sepsis
  • Pyelonephritis
  • Influenza
  • Endocarditis
  • Tonsillitis
  • Visceral abscess
  • Jarisch – Herxheimer reaction (JHR)
  • Malaria (Returning travelers and third world countries)

There are other causes of rigor that are not associated with infection

  • Gentamycin, Vancomycin and Amphotericin-B
  • Anti-TNF alpha drugs, iterleukin 2
  • Cathetarisation
  • Haemodialysis
  • Post bone marrow transplant
  • Post radiotherapy
  • Transfusion reaction
  • Even normal vaginal delivary