Monday, May 19, 2014

Calcium, Oh Calcium. Why do you come in 2 forms?

( If you are in a hurry, skip to the red sentences.)

We had a recent caller from the north metro request a clarification about calcium, specifically for the magnesium toxicity prooblem you may see when transporting a patient with pre-term labor.

The background is that magnesium relaxes smooth muscle. This is great when the smooth muscles of the uterus are contracting, or, in theory, the smooth muscles of your lungs are tightening during an asthma attack.

It follows that too much magnesium can make other smooth muscles stop working. This would include your diaphragm ( a smooth or involuntary muscle) and the muscles that run your reflexes ( also smooth or involuntary muscles.) So too much magnesium makes your breathing slow down and you reflexes go away, that is how you measure toxicity.

If you decide your patient on a magnesium drip is getting toxic, you should first turn off the magnesium drip. Then you should give calcium as an anti-dote.

And that is where we run into trouble. The ALS trucks carry calcium chloride for the purposes of cardiac arrests and elevated potassium. This is a fine medication for use in magnesium toxicity. Just put the whole ampule (1 gram) in over 10 minutes.

If you happen to get a calcium gluconate from the hospital, use it the same way, the whole ampule in 10 minutes.

Yes, the two have different amounts of elemental calcium in them. If you ask a chemist, they will sat that 1 ampule of calcium chloride has 272 mgs of calcium in it, while 1 ampule of calcium gluconate has 90 mgs of elemental calcium in it.

For medical use, we are only concerned about the clinical effects and 1 ampule of either will have the same effect

The only reason I can figure why gluconate is preferred over chloride when a magnesium drip is the problem is this:

Calcium Chloride will combine with magnesium and form a solid when used in the same IV line.

If you use the Calcium chloride, you have to use another line.

It is not an issue with calcium gluconate.