Lab Case 255 Interpretation

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55 years old male is brought to emergency department by SJA with complaint of generally feeling unwell for last 24 hours or so. His past medical history includes T2DM, HTN, CRF and currently on peritoneal dialysis. He has been compliant with his dialysis and has not noticed any cloudy bags. He denies any infective symptoms, but seems to complain about spasms in his arms, hands and twitching of face  for last 12 hours. He also feels lightheaded and has following observations.

HR 95, BP 92 systolic, afebrile, RR 20, sats 95 RA. His VBG results are as followed.

PH        7.30

PCO2    42

HCO3    22

Na         140

K           5.3

Lactate   2.3

Creatinine   380 ( baseline 350).

Cl            95

 

Answers:

  1. Mild acidemia PH 7.32. likley metabolic as HCO3 is 22. , AG = 141-117 = 24 . Expected Co2 41.

Interpretation: High anion gap metabolic acidosis in the setting          of renal failure and mildly raised lactate.

  1. “Serum Calcium” should be checked as clinical information is             concerning for hypocalcemic tetany and spasms in CRF                   patients.
  • Total serum Ca2+ range = 2.2 – 2.5 mmol/L (55% bound, 45% ionised)
  • ionized Ca2+ range (50%) = 1.1-1.3mmol/L
  • protein bound Ca2+ range (40%) = 0.95-1.2mmol/L
  • complex Ca2+ (10% – calcium phosphate, salts) = 0.05mmol/L

Patients Calcium results came back as “serum calcium” 1.5 mmol per lit.

  • Hypoalbuminemia (Ca2+ bound to albumin)
  • Hypoparathyroidism
  • Chronic renal failure
  • Electrolyte disorders: Hypomagnesemia, Hyperphosphatemia
  • Abnormal cell destruction: tumor lysis syndrome, rhabdomyolysis
  • Severe pancreatitis
  • Drugs: Calcitonin, phosphate, bisphosphonates
  • Tox: HFl acid burn
  • Massive blood transfusion (due to citrate in blood products)
  • Hyperventilation : Ionised calcium is inversely proportional to PH

3.     ECG features of hypocalcemic include prolonged QT interval,            and risk of torsade depointes. Can lead to circulatory collapse          and CCF ( severe hypocalcemic).

Other features of Hypocalcemia include:

Neuromuscular Effects

  • Muscle cramping
  • Paraesthesias
  • Tetany
  • Chvostek’s sign: facial muscle twitching with tapping over facial nerve (commonly seen in patients without hypocalcemia)
  • Trousseau’s sign: carpal spasms induced by inflation of a blood pressure cuff 20 mm Hg above systolic BP X 3 minutes
  1. Treatment of this patient involves small fluid bolus to avoid further hypotension, IV calcium ( Ca gluconate or Calcium chloride 10mmol 10 percent over 30 min to 1 hour , and can be repeated. Treatment of underlying cause which in this case is ongoing dialysis. Replacement of Mg, and optimisation of K is also needed to avoid risk off ventricular arrhythmia.