haldol and QTc

1 Dec
RAGING HYPOTHETICAL:
–You are working overnight and get called about an elderly lady who is agitated. Your patient has IV access and the nurse wants to know what to give. What do you order?

HALDOL (one option):
–can prolong QT interval; should be avoided if QTc is already prolonged
–Haldol is actually FDA approved for IM, not IV. (but we use it IV all the time)
–peaks in the serum in about 20min
OTHER OPTIONS:
–Seroquel is a good PO option (consider 12.5 mg or 25 mg)

–Ativan can worsen delerium (avoid if possible, especially in elderly)

QT  FACTOIDS:
–normal QTc is less than or equal to ~440ms (males borderline long at 431-450, females 451 to 470)
—  >450 is abnormal for males and >470 is abnormal for females.
–the QT interval can be prolonged with hypoKalemia, low Mg, or hypothyroidism (and many, many drugs)
–remember Bazett’s formula (or look it up)

QTc=QT√RR

–cheater’s way: QTc should be less than 1/2 of the R-R interval.

10-SECOND RECAP:

–agitation tx options: haldol, seroquel, ativan
–haldol can prolong QT, as with MANY other drugs
QTc=QT√RR   (or 1/2 the R-R interval)
–normal QTc is less than 440ms(ish)
Submitted by R. Morris.
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