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Bicarbonate Therapy in Severe Metabolic

Sandra Sabatini and Neil A. Kurtzman

Department of Internal Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas

ABSTRACT monly termed “potential” bicarbonate. The utility of bicarbonate administration to patients with severe Giving bicarbonate to a patient with a remains controversial. Chronic bicarbonate replacement is obviously indicated for true bicarbonate deficit is not controver- patients who continue to lose bicarbonate in the ambulatory setting, particularly sial. Controversy arises when the de- patients with syndromes or diarrhea. In patients with acute crease in bicarbonate concentration is lactic acidosis and ketoacidosis, lactate and ketone bodies can be converted back the result of its conversion to another to bicarbonate if the clinical situation improves. For these patients, therapy must , which, given time, can be converted be individualized. In general, bicarbonate should be given at an arterial pH back to bicarbonate. If one knew that the of Յ7.0. The amount given should be what is calculated to bring the pH up to 7.2. timely and efficient conversion of aceto- The urge to give bicarbonate to a patient with severe acidemia is apt to be all but acetate and ␤-hydroxybutyrate or lactate irresistible. Intervention should be restrained, however, unless the clinical situation back to bicarbonate would occur with- clearly suggests benefit. Here we discuss the pros and cons of bicarbonate therapy out morbidity or mortality, then there for patients with severe metabolic acidosis. would be no reason even to contemplate giving bicarbonate. J Am Soc Nephrol 20: 692–695, 2009. doi: 10.1681/ASN.2007121329 In considering acute bicarbonate re- placement, four questions should be considered: (1) What are the deleterious Metabolic acidosis is an -base disor- Ͻ Ͼ (P 0.01). Also, 80% of nephrologists effects of acidemia, and when are they der characterized by a primary con- CO would consider the P 2 in making their manifest? (2) When is acidemia severe sumption of body buffers including a fall decision to treat, whereas only 59% of enough to warrant therapy? (3) How in blood bicarbonate concentration. intensivists would (P Ͻ 0.02). For pa- much bicarbonate should be given, and There are many causes (Table 1), and tients with lactic acidosis, 86% of neph- how is that amount calculated? (4) What there are multiple mechanisms that min- rologists would treat with bicarbonate, are the deleterious effects of bicarbonate imize the fall in arterial pH. A patient whereas two thirds of intensivists would therapy? with metabolic acidosis may have a nor- give bicarbonate (P Ͻ 0.05). A wider Severe acidemia causes a decrease in mal or even high pH if there is another variance was noted in the therapy of dia- myocardial contractility, a fall in cardiac primary, contravening event that raises betic ketoacidosis. Sixty percent of neph- output, and a fall in BP. Acidemia also the bicarbonate concentration (vomit- rologists would treat with bicarbonate decreases the binding of norepinephrine ing) or lowers the arterial PCO - versus 28% of intensivists (P Ͻ 0.01). 2 (respira to its receptors. It also shifts the oxyhe- tory ). Metabolic acidosis differs Both groups would administer bicarbon- moglobin curve to the right, allowing from “acidemia” in that the latter refers ate by constant infusion, targeting an ar- more O2 to be released—the . solely to a fall in blood pH and not the terial pH of 7.2 as a goal. Seventy-five Protons bind to intracellular proteins as process. percent of nephrologists would calculate well as extracellular proteins, especially A recent online survey by Kraut and the amount of bicarbonate required, Kurtz1 highlighted the uncertainty over whereas only one third of intensivists when to give bicarbonate to patients with would do this. Published online ahead of print. Publication date metabolic acidosis. They reported that Metabolic acidosis results from a loss available at www.jasn.org. nephrologists will prescribe therapy at a of bicarbonate from the body (e.g., diar- Correspondence: Dr. Neil A. Kurtzman, Depart- higher pH compared with critical care rhea) or from its titration to an anionic ment of Internal Medicine, 3601 4th MS 9410, Texas Tech University Health Sciences Center, Lubbock, physicians. Forty percent of the intensiv- base that often can be converted back to TX 79430. Phone: 806-743-3181; Fax: 806-743- ists would not give bicarbonate unless bicarbonate, such as seen in diabetic ke- 1092; E-mail: [email protected] Ͻ the pH were 7.0; only 6% of nephrolo- toacidosis or lactic acidosis (Table 1). Copyright ᮊ 2009 by the American Society of gists would wait until pH gets this low This nonbicarbonate base anion is com- Nephrology

692 ISSN : 1046-6673/2004-692 J Am Soc Nephrol 20: 692–695, 2009 www.jasn.org CLINICAL COMMENTARY

Table 1. Causes of severe metabolic acidosis is given (1.5 mmol/kg over 5 min).8 By General Mechanism Specific Clinical Examples contrast, infusion with THAM® (Hos- pira Inc., Lake Forest, IL) or CarbiCarb® True HCO3 deficit Renal tubular acidosis (International Medication System, gastrointestinal Diarrhea South El Monte, CA) does not affect ar- ϩ 8,9 H gain terial PCO2. These observations have

exogenous acid NH4Cl administration, toxins led some investigators to recommend ei- abnormal lipid Diabetic ketoacidosisa ther of these compounds as preferred abnormal carbohydrate metabolism therapy.2 normal protein metabolism Uremic acidosis Bicarbonate therapy is also associated a Љ Љ Also a component of true HCO3 deficit because ketone bodies ( potential HCO3) are lost in the urine with an increase in mortality. This has both before and after admission. been noted in humans and experimental albumin and . Thus, aci- The volume of distribution of bicar- animals under a variety of acidemic con- demia may adversely affect cell functions bonate is approximately that of total ditions.10–12 The increase in mortality is such as enzymatic reactions, ATP gener- body water. In patients with metabolic blamed on a fall in BP and cardiac out- ation, fatty acid biosynthesis, and acidosis, it is said to vary from 50% to put. There are also shifts in ionized cal- formation/resorption.2–4 Ͼ100%, depending on the severity of the cium; in strong acid acidosis, All drugs that are the salts of weak acidemia.6 This distribution will obvi- also shifts out of the cell sensitizing the bases or have a dissociation con- ously affect the calculated bicarbonate heart to abnormal electrical activity and stant. Those that are the salts of a weak deficit. Any calculated amount will be subsequent arrhythmias. Moreover, a acid will have more of the drug in the only approximate, of course. The patient “paradoxic” intracellular acidosis may nonionized form in an acid environment should be carefully monitored and bicar- occur when giving bicarbonate therapy and, thus, may manifest increased toxic- bonate administration altered, when because CO2 generated from its titration ity. One such example of enhanced tox- given, to suit the course. Fernandez et al.7 freely diffuses across the cell membrane. icity during acidemia is that of acetylsal- derived a more precise formula for calcu- In addition, both volume expansion and icylic acid. Other salts of weak acids are lating the bicarbonate space: (0.4 ϩ 2.6/ hypernatremia can occur; in patients tolbutamide, methotrexate, phenobarbi- PHCO3) (body weight). A graphic repre- with compromised cardiac output, ful- tal, and phenytoin. The degree of ioniza- sentation of the formula (Figure 5 in minate congestive heart failure with flash tion is only one of the factors that deter- reference7) shows that the “apparent” bi- pulmonary edema may result. mine a drug’s across cell space increases quite mark- Many in vitro studies show that intra- membranes, but it is crucial in those edly with acidemia but decreases very lit- cellular alkalinization hastens cell death body compartments in which pH may tle with alkalemia. Although they used after anoxia13; if cell water is maintained change.5 actual data from several human studies, at pH 6.8, for example, more tissue re- The optimum extracellular pH for all it is not clear that renal response to aci- mains viable.14,15 Bicarbonate adminis- physiologic mechanisms and organ demia was accounted for as they ana- tration may stimulate superoxide forma- functions is 7.4. By contrast, intracellular lyzed acute acid-base disorders. This for- tion, increase proinflammatory cytokine pH is approximately 7.1 in virtually every mula, like any other guide to bicarbonate release, or enhance apoptosis. Whether tissue studied. Many diverse mecha- treatment, should just be a starting point, these observations relate to human dis- nisms are in place to maintain both ex- which is modified as events unfold. orders with acidemia is unknown. Re- tracellular and intracellular pH within In some patients, only a small amount bound alkalemia may also occur after this very narrow range. Deviations from of bicarbonate may be required. For ex- base administration, especially when the normal pH will obviously decrease the ample, if a patient has a PCO2 of 13 PCO2 is low. Giving bicarbonate to both efficiency of all reactions, although the mmHg and bicarbonate of 4 mEq/L, animals and humans increases blood lac- degree will vary depending on the spe- then his arterial pH is 7.1. If the bicar- tate and ketone bodies.6,16–18 This “po- cific event. For example, whereas aci- bonate is doubled (raised to only 8 mEq/ tential” bicarbonate will be converted demia protects the central nervous sys- L), then the blood pH will increase to 7.4. back to actual bicarbonate unless it lost tem against seizures, it sensitizes the This is true only if the PCO2 does not in the urine. myocardium to arrhythmias. Because we change. In this example, given a static do not measure intracellular pH, we PCO2, if the bicarbonate concentration must use extracellular pH (arterial or ve- rises only 1 mEq/L, then the pH would be nous) as a surrogate. Most authorities in above 7.2. Arterial PCO2 typically, how- acid-base physiology would give bicar- ever, does not remain the same after In ketoacidosis, substantial amounts of ␤ bonate to a patient with an arterial pH NaHCO3 infusion. In patients with se- acetoacetate and -hydroxybutyrate are Ͻ7.1, but, as we discuss, this is not a hard vere acidosis, it rises 6.7 Ϯ 1.8 mmHg lost in the urine before the patient arrives and fast rule. when an infusion of bicarbonate at the hospital. Thus, not only has the

J Am Soc Nephrol 20: 692–695, 2009 Bicarbonate and Metabolic Acidosis 693 CLINICAL COMMENTARY www.jasn.org patient converted bicarbonate to “poten- ninth time in diabetic ketoacidosis. He sponsible for the acidosis, base therapy tial bicarbonate,” he is truly bicarbonate was poorly responsive and had Kussmaul will be futile. deficient. More urinary loss of ketone respirations. Before any therapy, he had a If bicarbonate is given, then its bodies occurs after fluid administration plasma Na of 140 mEq/L, K of 4 mEq/L, amount should be calculated as the de- and volume repletion. Hence, the ubiq- Cl of 109 mEq/L, CO2 of 3 mEq/L, and sired minus the observed bicarbonate uitous hyperchloremic metabolic acido- of 1 mg/dl. The arterial pH concentration using a volume of distri- sis we see the day after insulin therapy is was 6.95, PCO2 was 14 mmHg, and the bution of total body water. It should also initiated. In ketoacidosis, it is almost calculated HCO3 was 3 mEq/L. Urine be assumed that the arterial PCO2 will not never necessary to give bicarbonate even and blood ketones were strongly posi- change. The desired bicarbonate concen- though the patient is bicarbonate defi- tive. He was treated with insulin and ap- tration at this unchanged PCO2 is that cient unless renal function is perma- propriate fluid and replace- which will give an arterial pH of 7.2. This nently impaired. Therapy with fluids and ment. He was not given bicarbonate. The calculation is only an approximation. At restores extracellular volume next day he was fully oriented. His the end of 2 h, an arterial blood gas and and renal blood flow, thus enhancing the plasma Na was 142, K was 4, Cl was 114, chemistries should be remeasured and a renal excretion of acid and regenerating and CO2 was 18 mEq/L. The remainder new plan for the next2hmade. Note that bicarbonate. Okuda et al.18 demon- of his clinical course was unremarkable. patient 1 got no bicarbonate. He was oth- strated in humans with diabetic ketoaci- erwise healthy with a normal cardiovas- dosis, as well as in the in situ acidemic Patient 2 cular system, whereas patient 2 received perfused rat liver (pH of 7.15), that bi- An 80-yr-old man was admitted with se- bicarbonate because he had a severely carbonate therapy markedly increased vere congestive heart failure. He was hy- compromised cardiovascular system. blood acetoacetate and ␤-hydroxybu- potensive and oliguric. He had both pul- Thus, it is impossible to be dogmatic tyrate levels. Infusion also increased monary and peripheral edema. His about the treatment of acidemia. No blood lactate levels approximately three- baseline creatinine was known to be 1.6 hard and fast rule works for every pa- fold. Others have reported similar find- mg/dl. On arrival at the emergency de- tient. ings.19 Indeed, bicarbonate therapy actu- partment, his plasma Na was 135 mEq/L, ally delays the removal of ketone bodies K was 4 mEq/L, Cl was 97 mEq/L, CO2 from the blood. was 7 mEq/L, and creatinine was 2.5 mg/ DISCLOSURES dl. His arterial pH was 7.1, PCO2 was 20 None. mmHg, and the calculated HCO3 was 6 LACTIC ACIDOSIS mEq/L. The blood lactate level was 20 mmol/L. The patient was intubated and REFERENCES Lactic acidosis is an ominous event and placed on a respirator, keeping his PCO2 generally signifies severe tissue hypoxia. at 20 mmHg. Continuous venovenous 1. Kraut JA, I Kurtz: Use of base in the treat- It may be secondary to an exogenous hemodialysis was begun with a bath con- ment of severe organic acidosis and critical toxin such as or metformin or taining 14 mEq/L of bicarbonate. He was care physicians: Results of an online survey. the result of severe tissue underperfusion given an infusion of 300 mEq of bicar- Clin Exp Nephrol 10: 111–117, 2006 from cardiogenic or hemorrhagic shock. bonate over 2 h; with a total body water 2. Luft F: Lactic acidosis update for critical care clinicians. J Am Soc Nephrol 12[Suppl 17]: The mortality of lactic acidosis ap- of 43 L, one would aim for an HCO3 of 14 ϫ ϭ S15–S19, 2001 proaches 80% or more. This is often be- mEq/L: (7 mEq/L 43 L 301 mEq). At 3. Schoolwerth A, Kaneko TM, Sediacek T, cause of the inability to correct ade- the end of that time, his pH was 7.2 and Block CA, Remillard BD: Acid-base distur- bances in the intensive care unit: Metabolic quately the underlying disorder(s). A the HCO3 was 13 mEq/L. Five days later, number of studies show even if blood he was transferred out of the intensive acidosis. Semin Dial 19: 492–495, 2006 lactate level is lowered with drug therapy, care unit, his lactic acidosis resolved. 4. Androgue HJ: Metabolic acidosis: Patho- physiology, diagnosis and management. J 17,20,21 mortality is unchanged. Nephrol 19: S62–S69, 2006 5. Brunten LL, Lazo JS, Parker K, Buxton I, Blu- FINAL THOUGHTS menthal D, eds.: Goodman and Gilman’s CASE EXAMPLES Pharmacological Basis of Therapeutics Dig- Bicarbonate therapy for metabolic aci- ital Edition, 11th Ed., New York, McGraw Hill, 2006 The following two cases demonstrate dosis is recommended at an arterial pH 6. Garella S, Dana CL, Chazan JA: Severity of that therapy for acidemia requires flexi- varying from as low as 6.9 to as high as metabolic acidosis as a determinant of bi- bility. 7.2. We suggest that bicarbonate therapy carbonate requirements. N Engl J Med 289: be given at pH 7.0 but that this target pH 121–126, 1973 7. Fernandez PC, Cohen RM, Feldman GM: Patient 1 be a guide that is variable depending on The concept of bicarbonate distribution A 20-yr-old man with a 5-yr history of clinical setting. Unless efforts are focused space: The crucial role of body buffers. Kid- type 1 diabetes was admitted for the on reversing the underlying defects re- ney Int 36: 747–752, 1989

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8. Levraut L, Garcia P, Giunti C, Ichai C, 13. Curren RT, Gores GJ, Thurman RG, Lemas- 18. Okuda Y, Androgue HJ, Field JB, Nohara H, Boureaba M, Ciebiera JP, Payan P, Grimaud ters JJ: Protection by acidic pH against an- Yamshita K: Counterproductive effects of

D: The increase in CO2 production induced oxic cell killing in the perfused rat liver: Ev- in diabetic ketoacido-

by NaHCO3 depends on blood albumin and idence for a pH paradox. FASEB J 5: 207– sis. J Clin Endocrinol Metab 81: 314–319, hemoglobin concentrations. Intensive Care 210, 1991 2000 Med 26: 558–564, 2000 14. Bing OH, Brooks WW, Messer JV: Heart 19. Makiasalo JH, Soini HO, Nordin HJ: Effects 9. Holmdahl MH, Wiklund L, Wetterberg T, muscle viability following hypoxia: Protec- of bicarbonate therapy on tissue - Streat S, Wahlander S, Sutin K, Nahas G: The tive effect of acidosis. Science 180: 1297– ation during resuscitation of hemorrhagic place of THAM in the management of aci- 1298, 1973 shock. Crit Care Med 17: 1170–1174, demia in clinical practice. Acta Anaesthesiol 15. Zager RA, Schimpf BA, Gmur DJ: Physio- 1989 Scand 44: 524–527, 2000 logic pH: Effects on posthypoxic proximal 20. Rhee KH, Toro LO, McDonald GG, Nunnally 10. Sing RF, Branas CA, Sing RF: Bicarbonate tubular injury. Circ Res 72: 837–846, RL, Levin DL: Carbicarb, sodium bicarbon- therapy in the treatment of lactic acidosis: 1993 ate, and sodium in hypoxic lactic Medicine or toxin? J Am Osteopath Assoc 16. Graf H, Leach W, Arieff AI: Evidence for a acidosis: Effect on arterial blood gases, lac- 95: 52–57, 1995 detrimental effect of bicarbonate therapy in tate concentration, hemodynamic variables 11. Stacpoole PW: Lactic acidosis: The case hypoxic lactic acidosis. Science 227: 754– and intracellular pH. Chest 104: 913–918, against bicarbonate therapy. Ann Intern 756, 1985 1993 Med 105: 276–279, 1986 17. Bersin RM, Chatterjee, Arieff AI: Metabolic 21. Cooper DJ, Walley KR, Wiccs BR, Russell JA: 12. Gehlbach BK, Schmidt GA: Bench-to-bed- and hemodynamic consequences of so- Bicarbonate does not improve the dynamics side review: Treating acid-base abnormali- dium bicarbonate administration in pa- in critically ill patients who lactic acidosis: A ties in the intensive care unit—The role of tients with heart disease. Am J Med 87: prospective, controlled clinical study. Ann buffers. Crit Care 8: 259–265, 2004 7–14, 1989 Intern Med 112: 492–498, 1990

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