Electrolytes: the six that kill
Six mechanism strips in a three-by-two block, each with the ion symbol, an arrow showing the lethal direction, one organ glyph, and a single line naming the finding.
The six
- Potassium — high or low, it disturbs cardiac conduction. Either direction can arrest a heart, which is why it owns the monitor.
- Sodium — falling quickly, it swells the brain and seizes it. Corrected too quickly, the correction itself injures the brain.
- Calcium — low calcium produces tetany and laryngospasm. Positive Chvostek and Trousseau signs are the bedside evidence.
- Magnesium — low magnesium invites torsades de pointes. High magnesium erases deep tendon reflexes before it erases respiration.
- Phosphorus — moves opposite calcium, so it tells you where calcium went.
- Chloride — follows sodium and reports on acid-base state.
The one absolute rule
Concentrated potassium is never administered by intravenous push. It is always diluted, always infused, and the infusion runs with cardiac monitoring at a rate set by protocol.
The assessment that finds it first
For potassium and magnesium, the finding is on the cardiac monitor. For calcium, it is at the face and the hands. For sodium, it is in the level of consciousness. For magnesium excess, it is at the patellar reflex, checked before the monitor ever alarms.
The reflex check
A deep tendon reflex that is disappearing during a magnesium infusion stops the infusion first. You notify afterward. Nothing else happens in between.
Memory hookpotassium and magnesium live on the monitor, calcium lives on the face, sodium lives in the head.
Margin noteeach one kills through exactly one organ.
Watch outnever push potassium.
Takeawayknowing which organ an electrolyte kills through gives you both the assessment and the priority.
Ranges and replacement decisions → BOOK 07 · P8. Infusion rate math → BOOK 06 · P9.