UMEM Educational Pearls

Non-dihydropyridine calcium channel blockers, verapamil and diltiazem, can induce hypotension when administered intravenously (IV) in approximately 4% of patients.  It has previously been taught that administering IV calcium before administering these medications may prevent the hypotension.  Previously, this theory was tested for verapamil and found success with reducing hypotension.  Only one study has been done exclusively with diltiazem and it found no benefit. 

In a new multicenter retrospective cohort study of adults in the ED, patients were randomized into two groups: those who received diltiazem alone and those who received calcium with diltiazem for atrial fibrillation/atrial flutter (AF/AFL) with a HR ≥ 120 bpm. Patients were excluded if they required electrocardioversion, had other agents prior to diltiazem, incomplete information, were pregnant or incarcerated. The primary outcome was change in SBP 60 minutes (+/-30 minutes) after diltiazem administration.

Baseline characteristics: 73 year old, equal male:female, predominantly white patients.  40% had new onset AF/AFL and the initial HR was 140 in both groups. There were 198 patients in the diltiazem group and 56 patients in the combination group.  Notably, patients in the combination group had a lower presenting SBP 109 (101-121) vs 123 (114-132) P<0.0001 which matches classical teaching for when to consider calcium use. Additionally, patients in the combination group received a lower diltiazem dose of 10mg vs 15mg in the monotherapy group p=0.004 with both group receiving doses lower than the standard 0.25 mg/kg dosing recommendation.

Outcomes:

• Median change in SBP was not different between the monotherapy and combination therapy groups: (-2 mmHg vs -1.5 mmHg, p= 0.642)
• There was no difference in:
  • Time to rate control (1.4 vs 1.8 hours, p= 0.141)
  • Time to sustained rate control (7.9 vs 7.7 hours, p=0.570)
  • Change in HR at 60 minutes: (-33 vs -34 bpm, p=0.428)
• A subgroup analysis looking at timing of calcium (i.e. before or with diltiazem administration) also found no difference.

Take Home Point:

Administration of IV calcium may not be as beneficial as previously thought to prevent hypotension induced by diltiazem administration.  This particular study is confounded by the relatively low doses of diltiazem overall, but utilizing a lower dosing strategy in patients with low SBP is a reasonable safety strategy.

 

References