Calcium before Diltiazem may reduce hypotension in rapid atrial dysrhythmias

The Case
A 56 y/o man presents to the ED via ambulance. He was sent from clinic for 'new onset afib.' His pulse ranges between 130 and 175 bpm, while his blood pressure is holding steady at 106/58 mm Hg. He has a past medical history significant for hypertension and hypercholesterolemia. His only medications are hydrochlorothiazide and atorvastatin. The decision is made to administer an IV medication to 'rate control' the patient with a goal heart rate < 100 bpm.

The Clinical Question 
Calcium channel blockers, such as diltiazem and verapamil, can both cause hypotension. In the case above, the patient has borderline hypotension. 

What is the evidence behind giving IV calcium as a pre-treatment to prevent hypotension from calcium channel blockers?

The Data

The following table only includes studies where patients received calcium before the calcium channel blocker:

Citation	Study Design	N	Drug	Calcium Form/Dose	Results
Weiss AT, et al. Int J Cardiol 1983; 4:275-84.	Prospective	13	Verapamil	Calcium gluconate 1 gm	SBP ↑ 5 mm Hg
Roguin N, et al. Clin  Cardiol 1984; 7:613-6.	Case series	2	Verapamil	Calcium gluconate (pediatric pts)	No hypotentsion
Haft JI, et al. Arch Intern Med  1986; 146:1085-9.	Sequential study of 2 treatment protocols	50	Verapamil	CaCl 1 gm	SBP ↑ 2 mm Hg
Salerno DM, et al. Ann Intern Med  1987; 107:623-8.	Sequential study of 2 treatment protocols	5	Verapamil	Calcium gluconate 1gm	SBP ↓ 12 mm Hg
Stringer KA, et al. Drug Intell ClinPharm 1988; 22:575-6.	Case Report	1	Verapamil	CaCl 1gm	No hypotension
Barnett JC, et al. Chest 1990; 97:1106-9.	Prospective report of protocol	19	Verapamil	Calcium gluconate 1gm or CaCl 1gm	SBP ↑ 4 mm Hg
Kuhn M, et al. Am Heart J 1992; 124:231-2.	Retrospective chart review	18	Verapamil	Calcium gluconate 3gm or CaCl 1gm	No hypotension
Miyagawa K, et al. J Cardiovasc Pharmacol  1993; 22:273-9.	Sequential study of 2 treatment protocols	7	Verapamil	Calcium gluconate 3.75 mg/kg	SBP: no change
Kolkebeck T, et al. J Emerg Med 2004;  26(4):395-400.	Prospective, randomized, double-blind, placebo-controlled	34	Diltiazem	CaCl 0.333 gm	SBP ↓ 8 mm Hg (placebo had SBP ↓14 mm Hg)

  SBP: systolic blood pressure

  CaCl: calcium chloride

Clinical Impact

The data supports administering calcium before verapamil to prevent hypotension, without negatively impacting the desired rate control effect.

There has been only one study trying this approach with diltiazem (Kolkebeck 2004). Although there was NOT a statistically significant difference, the group that received calcium did have less of a blood pressure decrease than the group receiving placebo (SBP difference -8 vs -14 mm Hg). 

Limitations The biggest weakness of this study, to me, is that the authors used the manufacturer-recommended dose for diltiazem of 0.25 mg/kg first (max 20 mg), then 0.35 mg/kg (max 25 mg). This dose is rather large and often causes hypotension. The authors note limitations including the small sample size, the convenience sample design, and that a low dose of calcium was used (333 mg of 10% calcium chloride, 90 mg elemental calcium).

Why not use smaller doses of diltiazem starting at 5 or 10 mg and repeat as needed? We have had good success using this approach with diltiazem combined with pre-treatment calcium gluconate 1-2 gm. Others have utilized diltiazem infusions without a bolus to avoid the hypotensive effects. This approach allows for slow titration and the option to stop (or slow) the infusion if hypotension occurs.

Still others might argue to just give metoprolol. Actually, calcium channel blockers have performed admirably versus beta-blockers in this scenario and are recommended as first line (more to come in a future post).

Conclusions

• Although most of the data is with verapamil, administering calcium before diltiazem may prevent some of the hypotension. 
• There currently isn't much published data for diltiazem. The one study, which was a negative one, had some limitations. 
• The appropriate calcium dose is unknown, but 90 mg of elemental calcium (calcium gluconate 1 gm or calcium chloride 0.333 gm) is often used. We use 1 or 2 gm of calcium gluconate.

- Bryan Hayes, PharmD 
( @PharmERToxGuy)

Reference
Moser LR, et al. The use of calcium salts in the prevention and management of verapamil-induced hypotension. Ann Pharmacother 2000;34:622-9. [PMID 10852091]

How Social Media is Making an Impact in Medicine

Whether you realize it or not, the use of social media (i.e. Facebook, twitter, and blogs) has found its way into the world of medical students, residents, physicians, and medical educators all around the world. The use of these resources has several advantages versus in-person/print educational tools:

• Overcomes physical or temporal barriers
• Provides searchable content
• Encourages interactivity

What are the most common social media tools used, opportunities, and challenges in medical education?

What they did:

• Systematic literature review of 14 studies

Questions asked:

• Do social media tools affected outcomes of satisfaction, knowledge, attitudes, and skills for physicians and physicians-in-training? 
• What challenges and opportunities specific to social media have educators encountered in implementing these interventions?

Results:

• Most common social media tools used: 
• Blogs 71%
• Wikis 21%
• Twitter 14%
• Facebook 14%
• Most common social media aims: 
• Enhance clinical skills or knowledge 50%
• Promote empathy, reflection, or professionalism 36%
• Increase interest in a field 14%
• Most commonly cited opportunities: 
• Active learning 71%
• More feedback 57%
• Enhanced collaboration 36%
• Professional development 36%
• Career advancement/networking 21% 
• Supportive learning communities 14%
• Most commonly cited challenges: 
• Technical issues 43%
• Variable learner participation 43%
• Privacy/security concerns 29%

Limitations:

• Only one randomized controlled trial reviewed
• No comparison group in evaluation of satisfaction
• Studies included were too heterogeneous to perform sensitivity, subgroup or meta-analyses

Conclusion:

• Social media use in medical education is an emerging field of scholarship that merits further investigation.

How can social media impact a conference?

What they did:

• Documented the use of social media at The International Conference on Emergency Medicine (ICEM) 2012
• Determine the presence and activity of speakers on social media platforms
• Use of Twitter by attendees and non-attendees

Primary Objective:

• Report the presence and use of social media

Results:

• 212 speakers: 
• 41.5% use Linkedin
• 15.6% use Twitter
• 9.4% use a website/blog
• <1% use Google Plus
• 4,500 tweets during conference: 
• >400 people produced tweets, but only 34% were physically present at the conference
• 74.4% of the tweets were related to the clinical and research material presented at the conference

Limitations:

• Difficult to determine the significance and impact of Twitter on changing clinician practice patterns

Conclusion: 

• A large number of original tweets regarding clinical material at the conference were produced, with a very large portion coming from non-attendees.

Can Tweets Predict Citations?

What they did:

• Looked at all tweets containing links to articles in the Journal of Medical Internet Research (JMIR)
• 4,208 tweets cited 286 articles

Goals and questions:

• To measure social impact of and public attention to scholarly articles by analyzing buzz in social media
• To explore the dynamics, content, and timing of tweets relative to the publication of a scholarly article
• Question: Are social media metrics sensitive and specific enough to predict highly cited articles?

Results:

• Most tweets were sent on the day (43.9%) or the day after (15.9%) an article was published in a 60 day period.
• 9/12 (75%) of highly tweeted articles were highly cited
• Top-cited articles can be predicted from top tweeted articles with 93% specificity and 75% sensitivity

Limitations:

• Internal validation of one journal and no external validation

Conclusions: 

• Tweets can predict highly cited articles within the first three days of article publication

Summary
These three publications demonstrate that social media is here to stay in Medicine and medical education. Twitter especially has grown in popularity. Overall social media has an incredible potential to enhance and engage active learning among physicians and physicians-in-training. The next step now is to focus future research on outcomes (i.e. change in practice patterns) to help validate this technology.

References:

• Cheston CC et al. Social Media Use in Medical Education: A Systematic Review. Acad Med 2013 June; 88 (6). PMID: 23619071
• Eysenbach, Gunther. Can Tweets Predicts Citations? Metrics of Social Impact Based on Twitter and Correlation with Traditional Metrics of Scientific Impact. J Med Internet Res 2011; 13 (4): e123. PMID:22173204
• Neill A et al. The Impact of Social Media on a Major International Emergency Medicine Conference. Emerg Med J 2013; 0: 1 – 4. PMID: 23423992