Lab values master card II: chemistry and renal
A simplified silhouette with four organ zones — brain, heart, neuromuscular strip, kidneys — and eight value labels joined by leaders to the organ each one threatens first.
Ranges vary by institution. Every value here names the organ it threatens first, and that organ is your priority answer.
Strip 1 · Sodium 135 to 145 milliequivalents per liter. Threatens the brain. Both directions present as altered mental status, and rapid change in either direction brings seizure risk.
Strip 2 · Potassium 3.5 to 5 milliequivalents per liter. Threatens the heart, in both directions, so the critical flag sits at both ends of the gauge.
Strip 3 · Calcium Total 9 to 10.5 milligrams per deciliter; ionized 4.5 to 5.6. Low calcium threatens the airway through laryngospasm and produces tetany, tingling, and cramping.
Strip 4 · Magnesium 1.3 to 2.1 milliequivalents per liter. Low magnesium invites torsades de pointes. High magnesium takes the deep tendon reflexes first and respiration second, which is why the reflex is the monitor.
Strip 5 · Chloride and phosphorus Chloride 98 to 106 milliequivalents per liter. Phosphorus 3 to 4.5 milligrams per deciliter. Phosphorus and calcium move in opposite directions; when one is high, look for the other to be low.
Strip 6 · Glucose Fasting 70 to 100 milligrams per deciliter. What matters at the bedside is behavior: symptomatic hypoglycemia is treated before it is investigated, and a conscious patient who can swallow is treated by mouth.
Strip 7 · Renal function Blood urea nitrogen 10 to 20 milligrams per deciliter; creatinine 0.6 to 1.2. Creatinine is the more specific marker. Urea nitrogen also rises with dehydration, gastrointestinal bleeding, and high protein intake.
Strip 8 · Serum osmolality 275 to 295 milliosmoles per kilogram, read as the water-versus-solute summary of the entire panel.
Margin notepanel first, then the one that moved.
Watch outpotassium is the only value on this card that can stop a heart in either direction.
Takeawayevery chemistry value names an organ it threatens first, and that organ answers the priority question.
Chemistry drilled against cases → BOOK 07 · P6. Renal failure staging → BOOK 10 · P6.