Journal Club Podcast #49: April 2019
A brief look at the efficacy of sodium bicarbonate in the management of cardiac arrest…
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Article 2: Kim J, Kim K, Park J, Jo YH, Lee JH, Hwang JE, Ha C, Ko YS, Jung E. Sodium bicarbonate administration during ongoing resuscitation is associated with increased return of spontaneous circulation. Am J Emerg Med. 2016 Feb;34(2):225-9. Answer Key.
Article 3: Kawano T, Grunau B, Scheuermeyer FX, et al. Prehospital sodium bicarbonate use could worsen long term survival with favorable neurological recovery among patients with out-of-hospital cardiac arrest. Resuscitation. 2017 Oct;119:63-69. Answer Key.
Article 4: Ahn S, Kim YJ, Sohn CH,et al. Sodium bicarbonate on severe metabolic acidosis during prolonged cardiopulmonary resuscitation: a double-blind, randomized, placebo-controlled pilot study. J Thorac Dis. 2018 Apr;10(4):2295-2302. Answer Key.
You're working a busy shift in TCC one Sunday afternoon when you get a page that EMS is bringing in a patient in cardiac arrest. The patient is a 57-year-old male with unknown past medical history who collapsed while at church. On EMS arrival at the scene, the patient was in ventricular fibrillation. He was defibrillated twice, devolved into PEA, then went back into ventricular fibrillation two more times en route. He arrives in ventricular fibrillation after a final failed attempt at defibrillation. A bolus of amiodarone has also been given, along with four rounds of epinephrine.
You resume CPR as you switch the patient over to your monitor. He is being bagged via a laryngeal airway device with a good waveform on capnography. You defibrillate the patient, which results in PEA. He has now been in cardiac arrest for twenty minutes, and you begin to wonder what other management options you have. You consider whether you should give sodium bicarbonate or calcium chloride given his prolonged cardiac arrest, but your attending tells you that neither treatment is beneficial (though you aren't sure epinephrine is beneficial either, and you keep giving that).
After a total of thirty minutes of downtime, the patient is now in asystole and the decision is made to call the code. As you leave the room, you wonder whether you should have given sodium bicarbonate after all. You figure the patient had probably become quite acidotic, which you know decreases catecholamine responsiveness, and think trying to ameliorate that acidosis would help the patient. Not satisfied with your attending's brush-off, you decide to search the literature yourself and see what evidence is out there...
Population: Adult patients suffering out of hospital cardiac arrest. Special interest was paid to those with prolonged cardiac arrest
Intervention: Sodium bicarbonate administration
Comparison: Standard care
Outcome: Survival to hospital discharge with good neurologic function
The Clinical Queries tool in PubMed was searched using the terms “bicarbonate AND arrest,” resulting in 555 citations (https://tinyurl.com/yxj2682c). Of these, four articles were chosen. A search of the Cochrane Database did not identify any systematic reviews on this topic.
The debate surrounding the use of sodium bicarbonate in cardiac arrest is longstanding. Early Advanced Cardiac Life Support (ACLS) guidelines recommended routine bicarbonate administration for cardiac arrest, while more recent revisions have recommended against its routine use. Stoking this ongoing debate is a lack of rigorous evidence to direct practice.
Those randomized controlled trials on the topic either looked at outcomes of little importance to patients (Vukmir 2006)—such as return of spontaneous circulation (ROSC) or survival to the emergency department (ED)—or enrolled such a small sample of patients that clinical significance could not be determined (Ahn 2018). Vukmir et al found no difference in survival to ED admission (RR 0.99; 95% CI 0.70 to 1.40) among all patients, though they did demonstrate a trend toward improved survival in those patients with prolonged (> 15 minutes) cardiac arrest (RR 2.0; 95% CI 0.92 to 4.5). Unfortunately they did not look at long-term survival or neurologic outcomes. Ahn et al found no difference in ROSC or survival to hospital admission (RR 0.25; 95% CI 0.03 to 2.2), but the confidence intervals are so wide that they do not exclude a potentially clinically significant difference.
Larger observational studies have demonstrated conflicting results. Kawano et al (Kawano 2017) found a decrease in rates of survival to hospital discharge with bicarbonate administration (AOR 0.48, 95% CI 0.35-0.65) and a decrease in survival with a favorable neurologic outcome (AOR 0.61, 95% CI 0.43-0.86), after adjustment for multiple confounders. Kim et al (Kim 2016) demonstrated an increase in ROSC with bicarbonate administration (OR of 2.49; 95% CI 1.33 to 4.65) independent of other factors. While Kawano et al looked at more clinically appropriate outcomes, both studies were severely limited by a high risk of selection bias and imbalance with regards to both known and unknown confounders between the groups.
While there is not a substantial body of evidence to either support of refute the utility of bicarbonate administration in cardiac arrest, the bulk of the evidence does not suggest any benefit. Instead, providers should focus on those factors that have been shown to improve outcomes, such as high quality chest compressions with minimal interruptions and early defibrillation (when appropriate). Bicarbonate, meanwhile, should be reserved for specific case, such as hyperkalemia or suspected TCA overdose.