Tag Archives: ob

magnesium sulfate: great NNT, ? mechanisms

6 Nov

from October’s EP Monthly article:


IV magnesium sulfate: to prevent hospital admission in severe asthmatics

  • NNT = 3


Mechanisms for…

  • concurrent hypokalemia
    • magnesium repletion is required to prevent renal excretion of potassium by inhibiting ROMK channels in the distal tubules
  • eclampsia
    • unclear but may be due to systemic or cerebral vasodilation
  • tocolytic
    • calcium antagonism
  • dysrhythmias
    • magnesium is required for functioning of the Na/K ATPase enzyme, and hypomagnesemia can lead to prolonged QT and PR.
  • severe asthma exacerbations,
    • bronchodilation, though the mechanism by which it produces this is not well established


References: epmonthly article, theNNT.com; picture


RhoGAM in women AND men (maybe)

13 Dec

got your attention? i thought so.

nice article from October’s EP monthly (click through to read the whole thing)



give RhIG (RhoGAM) injection to pregnant women with vaginal bleeding in ED



in case of feto-maternal transfusion (esp if this is a spontaneous abortion), which would sensitize mom if she’s Rh(-) and baby is Rh(+), which might cause problems with future Rh(+) prenancies



historical practice and teaching is to treat, but evidence is insufficient



type and screen in the ED (though keeps patient around longer, potentially, waiting for this to come back)

look up an old blood type on this patient (handy if you’ve got an EMR)

ask the patient (someone did the study–link below)

  • prospective study, 319 pregnant women enrolled
  • asked to select “no,” “maybe,” or “yes, definitely” if they knew their blood type
  • Among the 106 subjects that reported “yes, definitely” they knew their blood type:
    • 103 (97.2%; 95% confidence interval [CI] 94.0-100%]) identified their correct blood type
    • 105 (99.1%; 95% CI 97.2-100%) identified their correct Rh status.
    • None of these subjects selected a positive Rh when they were in fact a negative Rh.
    • All 14 (13.2%) subjects with a negative Rh status identified themselves as having a negative Rh.



Rh(+) blood often given to men in trauma centers, because O(-) blood is rare, & men probably won’t get pregnant

Some places giving RhoGAM with O(+) blood, to prevent transfusion/hemolytic reaction for the NEXT transfusion (i.e. the next time this patient comes in as a trauma).


There you go.


References: ep monthly; ask the blood type article; picture