The measurement of serum osmolality and its application to clinical practice and laboratory: literature review

Faria, Daniel K.; Mendes, Maria Elizabete; Sumita, Nairo M.

doi:10.5935/1676-2444.20170008

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Jornal Brasileiro de Patologia e Medicina Laboratorial

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LABORATORY MEDICINE, Review article • J. Bras. Patol. Med. Lab. 53 (1) • Jan-Feb 2017 • https://doi.org/10.5935/1676-2444.20170008 copy

The measurement of serum osmolality and its application to clinical practice and laboratory: literature review

A medida da osmolalidade sérica e sua aplicação na prática clínica e laboratorial: revisão da literatura

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Introduction:

Serum osmolality is an essential laboratory parameter to understand several clinical disorders such as electrolyte disturbances, exogenous intoxication and hydration status.

Objective:

This study aims to update knowledge about the osmolality examination through research papers published to date.

Materials and methods:

The survey was conducted on PubMed database. It highlights main concepts, both historical and physiological aspects, and the clinical applications of the serum osmolality test. In addition, an extensive survey of formulas for the serum osmolality calculation was conducted.

Discussion:

The measurement of serum osmolality is relevant in changes in intracellular and extracellular balance, as a trusted and valuable indicator of solute concentration in the blood. The mathematical equations for serum osmolality calculation acquire relevance in health services where serum is not available, and situations in which calculation of the osmolal gap is necessary, but the variability of the formulas is a significant bias.

Conclusion:

The measurement of serum osmolality is useful in cases of dehydration, sodium and potassium disorders, glucose alteration, exogenous poisoning, adrenal insufficiency, neurological injury, physical exercise and others.

Key words:
osmolar concentration; osmosis; osmometry; plasma osmolality; serum osmolality; osmolal gap

Theme	No. of articles
Sodium disorders (hypernatremia and hyponatremia)	39
Diabetes mellitus and insipidus	25
Therapeutic drugs in hyperosmolar or hyposmolar states	19
Acute kidney injury, chronic kidney disease	17
Physiological aspects of osmolality	15
Acute and chronic neurological injury (traumatic and non-traumatic)	14
Exogenous intoxication (alcohol and other drugs)	13
Use of contrast medium	13
Albumin	11
Endocrine diseases^† † disorders related to thyroid hormones, lipoproteins, growth hormone, parathormone, aldosterone, glucocorticoids, and vitamin D.	11
Syndrome of inappropriate antidiuretic hormone secretion	10
Hypervolemic syndromes (ascites and heart failure)	9
Ocular osmolality	8
Dialysis	8
Water intoxication (primary polydipsia)	5
Osmolal gap calculation	4
Dehydration	4
Potassium, calcium or magnesium deficiency	4
Osmotic demyelination syndrome (pontine myelinolysis)	4
Sports medicine	4
Veterinary medicine	4
Physiological aspects in children	3
Sepsis	2
Hyperviscosity in oncological diseases	2
Mannitol	2
Copeptin	2
Hypovolemic shock	2
Diarrhea	2
Urine osmolality	2
Acid-base imbalance	2
Polyuria	1
Fluids during pregnancy	1
Cerebral salt-wasting syndrome	1
Gastrointestinal surgeries	1
Cardiac arrest	1
Acute respiratory failure	1
Spherocytosis	1
Sarcoidosis	1
Chron’s disease	1
Enteral nutrition	1
Plasmapheresis	1
Extracorporeal circulation	1

No.	Formulas	References
1	Osm = 2^* * 2.14. Na + BUN/2.8 + glucose/18	¹1 Rasouli M. Basic concepts and practical equations on osmolality: biochemical approach. Clin Biochem. 2016; 49(12): 936-41. PMID: 27343561. 2 Glaser DS. Utility of the serum osmol gap in the diagnosis of methanol or ethylene glycol ingestion. Ann Emerg Med. 1996; 27(3): 343-6. PubMed PMID: 8599495. 3 Kraut JA, Xing SX. Approach to the evaluation of a patient with an increased serum osmolal gap and high-anion-gap metabolic acidosis. Am J Kidney Dis. 2011; 58(3): 480-4. PubMed PMID: 21794966. 4 Berend K, Vries APJ, Gans R. Physiological approach to assessment of acid-base disturbances. N Engl J Med. 2014; 371: 1434-45. PubMed PMID: 25295502. 5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782. 6 Mcquillen KK, Anderson AC. Osmol gaps in the pediatric population. Acad Emerg Med. 1999; 6(1): 27-30. PubMed PMID: 9928973. 7 Dorwart WV, Chalmers L. Comparison of methods for calculating serum osmolality from chemical concentrations, and the prognostic value of such calculations. Clin Chem. 1975; 21(2): 190-7. PuMed PMID: 1112025. ^- ⁸8 Purssell RA, Pudek M, Brubacher J, Abu-Laban RB. Derivation and validation of a formula to calculate the contribution of ethanol to the osmolal gap. Ann Emerg Med. 2001; 38(6): 653-65. PubMed PMID: 11719745.
2	Osm = 1.86^* * 2.14. Na + BUN/2.8 + glucose/18 + 9	¹1 Rasouli M. Basic concepts and practical equations on osmolality: biochemical approach. Clin Biochem. 2016; 49(12): 936-41. PMID: 27343561. ^, ²2 Glaser DS. Utility of the serum osmol gap in the diagnosis of methanol or ethylene glycol ingestion. Ann Emerg Med. 1996; 27(3): 343-6. PubMed PMID: 8599495. ^, ⁵5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782. ^, ⁷7 Dorwart WV, Chalmers L. Comparison of methods for calculating serum osmolality from chemical concentrations, and the prognostic value of such calculations. Clin Chem. 1975; 21(2): 190-7. PuMed PMID: 1112025. ^, ⁹9 Bhagat CI, Garcia-Webb P, Fletcher E, Beilby JP. Calculated vs. measured plasma osmolalities revisited. Clin Chem. 1984; 30(10): 1703-5. PubMed PMID: 6537784.
3	Osm = 1.85^* * 2.14. Na + BUN/2.18 + glucose/17,5 + ethanol/4.22	²2 Glaser DS. Utility of the serum osmol gap in the diagnosis of methanol or ethylene glycol ingestion. Ann Emerg Med. 1996; 27(3): 343-6. PubMed PMID: 8599495.
4	Osm = 1.86^* * 2.14. Na + BUN/2.8 + glucose/18	²2 Glaser DS. Utility of the serum osmol gap in the diagnosis of methanol or ethylene glycol ingestion. Ann Emerg Med. 1996; 27(3): 343-6. PubMed PMID: 8599495. ^, ⁵5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782. 6 Mcquillen KK, Anderson AC. Osmol gaps in the pediatric population. Acad Emerg Med. 1999; 6(1): 27-30. PubMed PMID: 9928973. ^- ⁷7 Dorwart WV, Chalmers L. Comparison of methods for calculating serum osmolality from chemical concentrations, and the prognostic value of such calculations. Clin Chem. 1975; 21(2): 190-7. PuMed PMID: 1112025.
5	Osm = 1.86^* * 2.14. Na + BUN/2.8 + glucose/18 + 5	²2 Glaser DS. Utility of the serum osmol gap in the diagnosis of methanol or ethylene glycol ingestion. Ann Emerg Med. 1996; 27(3): 343-6. PubMed PMID: 8599495. ^, ⁵5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782. ^, ⁷7 Dorwart WV, Chalmers L. Comparison of methods for calculating serum osmolality from chemical concentrations, and the prognostic value of such calculations. Clin Chem. 1975; 21(2): 190-7. PuMed PMID: 1112025.
6	Osm = 2^* * 2.14. (Na + K) + BUN/2.8 + glucose/18	²2 Glaser DS. Utility of the serum osmol gap in the diagnosis of methanol or ethylene glycol ingestion. Ann Emerg Med. 1996; 27(3): 343-6. PubMed PMID: 8599495. ^, ⁵5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782. ^, ⁷7 Dorwart WV, Chalmers L. Comparison of methods for calculating serum osmolality from chemical concentrations, and the prognostic value of such calculations. Clin Chem. 1975; 21(2): 190-7. PuMed PMID: 1112025.
7	Osm = 2^* * 2.14. Na + BUN/3 + glucose/20	²2 Glaser DS. Utility of the serum osmol gap in the diagnosis of methanol or ethylene glycol ingestion. Ann Emerg Med. 1996; 27(3): 343-6. PubMed PMID: 8599495. ^, ⁵5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782. ^, ⁷7 Dorwart WV, Chalmers L. Comparison of methods for calculating serum osmolality from chemical concentrations, and the prognostic value of such calculations. Clin Chem. 1975; 21(2): 190-7. PuMed PMID: 1112025.
8	Osm = 2.1^* * 2.14. Na	²2 Glaser DS. Utility of the serum osmol gap in the diagnosis of methanol or ethylene glycol ingestion. Ann Emerg Med. 1996; 27(3): 343-6. PubMed PMID: 8599495. ^, ⁵5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782. ^, ⁷7 Dorwart WV, Chalmers L. Comparison of methods for calculating serum osmolality from chemical concentrations, and the prognostic value of such calculations. Clin Chem. 1975; 21(2): 190-7. PuMed PMID: 1112025. ^, ¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
9	Osm = 2.63^* * 2.14. Na – 65.4	²2 Glaser DS. Utility of the serum osmol gap in the diagnosis of methanol or ethylene glycol ingestion. Ann Emerg Med. 1996; 27(3): 343-6. PubMed PMID: 8599495. ^, ⁵5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782. ^, ⁷7 Dorwart WV, Chalmers L. Comparison of methods for calculating serum osmolality from chemical concentrations, and the prognostic value of such calculations. Clin Chem. 1975; 21(2): 190-7. PuMed PMID: 1112025. ^, ¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
10	Osm = 1.75^* * 2.14. Na + BUN/2.8 + glucose/18 + 10.1	²2 Glaser DS. Utility of the serum osmol gap in the diagnosis of methanol or ethylene glycol ingestion. Ann Emerg Med. 1996; 27(3): 343-6. PubMed PMID: 8599495. ^, ⁷7 Dorwart WV, Chalmers L. Comparison of methods for calculating serum osmolality from chemical concentrations, and the prognostic value of such calculations. Clin Chem. 1975; 21(2): 190-7. PuMed PMID: 1112025.
11	Osm = 1.85^* * 2.14. Na + 1.84^* * 2.14. K + BUN/2.8 + glucose/18 + calcium + 1.17^* * 2.14. magnesium + 1.14	²2 Glaser DS. Utility of the serum osmol gap in the diagnosis of methanol or ethylene glycol ingestion. Ann Emerg Med. 1996; 27(3): 343-6. PubMed PMID: 8599495. ^, ⁷7 Dorwart WV, Chalmers L. Comparison of methods for calculating serum osmolality from chemical concentrations, and the prognostic value of such calculations. Clin Chem. 1975; 21(2): 190-7. PuMed PMID: 1112025.
12	Osm = 2^* * 2.14. Na + BUN/2.8	²2 Glaser DS. Utility of the serum osmol gap in the diagnosis of methanol or ethylene glycol ingestion. Ann Emerg Med. 1996; 27(3): 343-6. PubMed PMID: 8599495. ^, ⁷7 Dorwart WV, Chalmers L. Comparison of methods for calculating serum osmolality from chemical concentrations, and the prognostic value of such calculations. Clin Chem. 1975; 21(2): 190-7. PuMed PMID: 1112025.
13	Osm = 2^* * 2.14. Na + glucose/18	²2 Glaser DS. Utility of the serum osmol gap in the diagnosis of methanol or ethylene glycol ingestion. Ann Emerg Med. 1996; 27(3): 343-6. PubMed PMID: 8599495. ^, ⁷7 Dorwart WV, Chalmers L. Comparison of methods for calculating serum osmolality from chemical concentrations, and the prognostic value of such calculations. Clin Chem. 1975; 21(2): 190-7. PuMed PMID: 1112025.
14	Osm = 2^* * 2.14. Na	²2 Glaser DS. Utility of the serum osmol gap in the diagnosis of methanol or ethylene glycol ingestion. Ann Emerg Med. 1996; 27(3): 343-6. PubMed PMID: 8599495. ^, ⁷7 Dorwart WV, Chalmers L. Comparison of methods for calculating serum osmolality from chemical concentrations, and the prognostic value of such calculations. Clin Chem. 1975; 21(2): 190-7. PuMed PMID: 1112025. ^, ¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
15	Osm = 2^* * 2.14. Na + 7	²2 Glaser DS. Utility of the serum osmol gap in the diagnosis of methanol or ethylene glycol ingestion. Ann Emerg Med. 1996; 27(3): 343-6. PubMed PMID: 8599495. ^, ⁷7 Dorwart WV, Chalmers L. Comparison of methods for calculating serum osmolality from chemical concentrations, and the prognostic value of such calculations. Clin Chem. 1975; 21(2): 190-7. PuMed PMID: 1112025. ^, ¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
16	Osm = 1.5^* * 2.14. Na + BUN/2.8 + glucose/18 + 45	⁵5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782.
17	Osm = 1.8^* * 2.14. (total of cations) + BUN/6 + glucose/18	⁵5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782.
18	Osm = 1.85^* * 2.14. Na + 1.84^* * 2.14. K + BUN/2.8 + glucose/18 + 1.15^* * 2.14. calcium + 1.17^* * 2.14. magnesium + 1.15	⁵5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782.
19	Osm = 1.86^* * 2.14. (Na + K) + BUN/2.8 + glucose/18 + 10	⁵5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782.
20	Osm = 1.89^* * 2.14. Na + 1.38^* * 2.14. K + BUN/2.7 + glucose/16.7 + 7.45	⁵5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782.
21	Osm = 2^* * 2.14. Na + BUN/3 + glucose/20 + 8	⁵5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782.
22	Osm = (1.86^* * 2.14. Na + BUN/2.8 + glucose/18)/0.93	⁵5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782. ^, ⁶6 Mcquillen KK, Anderson AC. Osmol gaps in the pediatric population. Acad Emerg Med. 1999; 6(1): 27-30. PubMed PMID: 9928973.
23	Osm = 2^* * 2.14. Na + BUN/2.8 + glucose/18 + ethanol/4.6	⁵5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782. ^, ⁸8 Purssell RA, Pudek M, Brubacher J, Abu-Laban RB. Derivation and validation of a formula to calculate the contribution of ethanol to the osmolal gap. Ann Emerg Med. 2001; 38(6): 653-65. PubMed PMID: 11719745.
24	Osm = 2^* * 2.14. Na + 10	⁵5 Kruse JA, Cadnapaphornchaihai P. The serum osmole gap. J Crit Care. 1994; 9(3): 185-197. PubMed PMID: 7981782. ^, ¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
25	Osm = 1.82^* * 2.14. Na + BUN/2.9 + glucose/23.9 + 24	⁶6 Mcquillen KK, Anderson AC. Osmol gaps in the pediatric population. Acad Emerg Med. 1999; 6(1): 27-30. PubMed PMID: 9928973.
26	Osm = 2^* * 2.14. Na + BUN/2.8 + glucose/18 + ethanol/3.7	⁸8 Purssell RA, Pudek M, Brubacher J, Abu-Laban RB. Derivation and validation of a formula to calculate the contribution of ethanol to the osmolal gap. Ann Emerg Med. 2001; 38(6): 653-65. PubMed PMID: 11719745.
27	Osm = 1.09^* * 2.14. 1.86^* * 2.14. Na + BUN + glucose	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
28	Osm = 1.36^* * 2.14. Na + 0.45^* * 2.14. BUN + 1.6^* * 2.14. glucose + 91.75	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
29	Osm = 1.75^* * 2.14. Na + BUN/2 + glucose + 10.1	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
30	Osm = 1.8^* * 2.14. (Na + K + calcium) + 0.47^* * 2.14. BUN/2 + glucose	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
31	Osm = 1.85^* * 2.14. Na + BUN/2 + glucose + 8.55	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
32	Osm = 1.85^* * 2.14. Na + 1.84^* * 2.14. K + BUN/2 + glucose + 1.15^* * 2.14. calcium + 1.17^* * 2.14. magnesium	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
33	Osm = 1.86^* * 2.14. Na + BUN/2 + glucose	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
34	Osm = 1.86^* * 2.14. Na + BUN/2 + glucose + 5	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
35	Osm = 1.86^* * 2.14. Na + BUN/2 + glucose + 9	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
36	Osm = (1.86^* * 2.14. Na + BUN/2 + glucose)/0.93	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
37	Osm = (1.86^* * 2.14. Na + 1.28^* * 2.14. BUN/2 + 1.03^* * 2.14. glucose)^* * 2.14. 0.985	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
38	Osm = 1.86^* * 2.14. (Na + K) + BUN + glucose	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
39	Osm = 1.897^* * 2.14. Na + BUN/2 + glucose + 13.5	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
40	Osm = 1.9^* * 2.14. (Na + K) + BUN/2 + glucose	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
41	Osm = 1.9^* * 2.14. (Na + K) + BUN/2 + glucose + 5	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
42	Osm = 2^* * 2.14. Na + BUN/2	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
43	Osm = 2^* * 2.14. Na + glucose	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
44	Osm = 2^* * 2.14. Na + BUN/2 + glucose	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
45	Osm = 2^* * 2.14. Na + 0.93^* * 2.14. BUN/2 + glucose	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
46	Osm = 2^* * 2.14. Na + 0.93^* * 2.14. BUN/2 + 0.9^* * 2.14. glucose	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
47	Osm = 2^* * 2.14. Na + 0.93^* * 2.14. BUN/2 + 0.9^* * 2.14. glucose + 8	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
48	Osm = (2^* * 2.14. Na + BUN + glucose + 35.2)^* * 2.14. 0.985	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
49	Osm = [2^* * 2.14. (Na + K) + BUN/2 + glucose]^* * 2.14. 0.985	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
50	Osm = 2^* * 2.14. (Na + K) + BUN/2 + glucose	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
51	Osm = 2^* * 2.14. (Na + K) + 0.93^* * 2.14. BUN/2 + glucose	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
52	Osm = (Na + K + chlorine + lactate + glucose + bicarbonate + BUN + 6.5)^* * 2.14. 0.985	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
53	Osm = 2^* * 2.14. Na + BUN + 1.15^* * 2.14. glucose	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685. ^, ¹¹11 Khajuria A, Krahn J. Osmolality revisited - deriving and validating the best formula for calculated osmolality. Clin Biochem. 2005; 38(6): 514-9. PubMed PMID: 15885229.
54	Osm = 1.86^* * 2.14. (Na + K) + BUN + 1.15glucose + 14	¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685. ^, ¹¹11 Khajuria A, Krahn J. Osmolality revisited - deriving and validating the best formula for calculated osmolality. Clin Biochem. 2005; 38(6): 514-9. PubMed PMID: 15885229. ^, ¹²12 Nelson PH. Osmosis and thermodynamics explained by solute blocking. Eur Biophys J. 2016 May 25. PubMed PMID: 27225298.
55	Osm = 1.86^* * 2.14. Na + BUN + glucose + 9	⁹9 Bhagat CI, Garcia-Webb P, Fletcher E, Beilby JP. Calculated vs. measured plasma osmolalities revisited. Clin Chem. 1984; 30(10): 1703-5. PubMed PMID: 6537784. ^, ¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
56	Osm = 1.86^* * 2.14. (Na + K) + BUN + glucose + 10	⁹9 Bhagat CI, Garcia-Webb P, Fletcher E, Beilby JP. Calculated vs. measured plasma osmolalities revisited. Clin Chem. 1984; 30(10): 1703-5. PubMed PMID: 6537784. ^, ¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
57	Osm = 1.89^* * 2.14. Na + 1.38^* * 2.14. K + 1.03^* * 2.14. BUN + 1.08^* * 2.14. glucose + 7.47	⁹9 Bhagat CI, Garcia-Webb P, Fletcher E, Beilby JP. Calculated vs. measured plasma osmolalities revisited. Clin Chem. 1984; 30(10): 1703-5. PubMed PMID: 6537784. ^, ¹⁰10 Fazekas AS, Funk GC, Klobassa DS, et al. Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med. 2013; 39(2): 302-8. PubMed PMID: 23081685.
58	Osm = 2^* * 2.14. Na + BUN + glucose	¹³13 Arora A. The 'gap' in the 'plasma osmolar gap'. BMJ Case Rep. 2013. PubMed PMID: 23929610.
59	Osm = 1.86^* * 2.14. (Na + K) + BUN + 1.15^* * 2.14. glucose + 1.2^* * 2.14. ethanol + 14	¹¹11 Khajuria A, Krahn J. Osmolality revisited - deriving and validating the best formula for calculated osmolality. Clin Biochem. 2005; 38(6): 514-9. PubMed PMID: 15885229.
60	Osm = 2^* * 2.14. Na + BUN + 1.15 × glucose + 1.2^* * 2.14. ethanol	¹¹11 Khajuria A, Krahn J. Osmolality revisited - deriving and validating the best formula for calculated osmolality. Clin Biochem. 2005; 38(6): 514-9. PubMed PMID: 15885229.
61	Osm = 2^* * 2.14. Na + BUN + glucose + ethanol	¹⁴14 Lynd LD, Richardson KJ, Purssell RA, et al. An evaluation of the osmole gap as a screening test for toxic alcohol poisoning. BMC Emerg Med. 2008; 8: 5. PubMed PMID: 18442409.
62	Osm = 2^* * 2.14. Na + BUN + glucose + 1,25^* * 2.14. ethanol	¹⁴14 Lynd LD, Richardson KJ, Purssell RA, et al. An evaluation of the osmole gap as a screening test for toxic alcohol poisoning. BMC Emerg Med. 2008; 8: 5. PubMed PMID: 18442409.
63	Osm = 2^* * 2.14. Na + BUN/2.8 + 1.15^* * 2.14. glucose/18	¹⁵15 Hansen L, Lange R, Gupta S. Development and evaluation of a guideline for monitoring propylene glycol toxicity in pediatric intensive care unit patients receiving continuous infusion lorazepam. J Pediatr Pharmacol Ther. 2015; 20(5): 367-72. doi:10,5863/1551-6776-20.5.367. PubMed PMID: 26472950. https://doi.org/10.5863/1551-6776-20.5.3...
64	Osm = 2^* * 2.14. Na + BUN/2.8 + 1.15^* * 2.14. glucose/18 + 1.2^* * 2.14. ethanol/4.6	¹⁶16 Krasowski MD, Wilcoxon RM, Miron J. A retrospective analysis of glycol and toxic alcohol ingestion: utility of anion and osmolal gaps. BMC Clin Pathol. 2012; 12: 1. PubMed PMID: 22240170. ^, ¹⁷17 Ehlers A, Morris C, Krasowski. A rapid analysis of plasma/serum ethylene and propylene glycol by headspace gas chromatography. Springerplus. 2013; 2(1): 203. PubMed PMID: 23741644.
65	Osm = 1.86^* * 2.14. (Na + K) + BUN + glucose + 9	⁹9 Bhagat CI, Garcia-Webb P, Fletcher E, Beilby JP. Calculated vs. measured plasma osmolalities revisited. Clin Chem. 1984; 30(10): 1703-5. PubMed PMID: 6537784.

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[1] CORRESPONDING AUTHOR: Daniel Kanaan Faria Divisão do Laboratório Central do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo; Av. Dr. Enéas de Carvalho Aguiar, 155, 2º andar; CEP: 05403-010; São Paulo-SP, Brasil; e-mail: daniel.kanaan@hc.fm.usp.br