To the Editor
Response to Dr. Freundlich et al
We would like to thank Dr. Freundlich and colleagues for their informed comments regarding our study. The concerns regarding the lack of adjusting the analysis to reflect serum pH, serum lactate, and the cationic difference between calcium gluconate and calcium chloride are points well taken. Serum pH does impact free calcium levels through ionic coupling with bicarbonate. In vivo this equilibration occurs very quickly. Thus measured iCa2+ levels reliably reflect available calcium stores unless the pH is changing very rapidly. Error can be introduced into iCa2+ measurements if samples are stored for a long period of time before being analyzed. In refrigerated samples, the pH generally drops and the measured iCa2+ will be falsely elevated whereas the opposite occurs in frozen samples. All of the labs we report were from fresh samples. Lactate is known to bind calcium similar to albumin; so this would only alter total calcium levels, not iCa2+. Regarding calcium repletion, calcium chloride contains 27 mg/mL elemental calcium whereas calcium gluconate contains only 9.3 mg/mL. In our pilot study only two patients received a single dose of calcium gluconate, and in both cases, received calcium chloride for all subsequent doses. Given the limited sample size, we chose not to exclude these cases. In future studies with larger patient numbers, we will be careful to evaluate and report elemental calcium. Thank you again for these insightful comments.
Sincerely,
Emily J. MacKay, DO1
Michael D. Stubna, PhD2
Daniel N. Holena, MD, MSCE3
Patrick M. Reilly, MD3,4
Mark J. Seamon, MD3
Brian P. Smith, MD3
Lewis J. Kaplan, MD3,4
Jeremy W. Cannon, MD MS3,4,5
1Department Anesthesiology & Critical Care, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
2Mountain Track Apps, Philadelphia, PA
3Division of Traumatology, Surgical Critical Care & Emergency Surgery, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
4Department of Surgery, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA
5Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD
Dear Editorial Staff
In the event you wish to publish an erratum. FFP IQR range should read [1–3] rather than [103] and Total Units ≥ 10 should be [n (%)] rather than [median (IQR)].
Appreciatively,
Emily J. MacKay, DO
Footnotes
Presentations: This work was presented as a poster at the 75th Annual Meeting of the American Association for the Surgery of Trauma, September 14–17, 2016, in Waikoloa, HI.
Financial Disclosures: None. The authors received no funding for this work and have no relevant conflicts of interest to declare.
Author Contributions:
E.J.M. and J.W.C. designed the study; E.J.M. performed the data acquisition; E.J.M. M.D.S., D.N.H., M.D.N., L.J.K., and J.W.C. performed data analysis; all authors interpreted the data; E.J.M. and J.W.C. prepared the manuscript, which all authors critically revised.