Special Feature American Society of Nephrology Quiz and Questionnaire 2013: Electrolyte and Acid-Base Biff F. Palmer,* Mark A. Perazella,† and Michael J. Choi‡ Abstract The Nephrology Quiz and Questionnaire (NQ&Q) remains an extremely popular session for attendees of the annual meeting of the American Society of Nephrology. As in past years, the conference hall was overflowing with interested audience members. Topics covered by expert discussants included electrolyte and acid-base disorders, *Department of Internal Medicine, glomerular disease, ESRD/dialysis, and transplantation. Complex cases representing each of these categories University of Texas along with single-best-answer questions were prepared by a panel of experts. Prior to the meeting, program Southwestern Medical directors of United States nephrology training programs answered questions through an Internet-based ques- Center, Dallas, Texas; † tionnaire. A new addition to the NQ&Q was participation in the questionnaire by nephrology fellows. To review Department of Internal Medicine, the process, members of the audience test their knowledge and judgment on a series of case-oriented questions Yale University School prepared and discussed by experts. Their answers are compared in real time using audience response devices with of Medicine, New the answers of nephrology fellows and training program directors. The correct and incorrect answers are then Haven, Connecticut; ‡ briefly discussed after the audience responses, and the results of the questionnaire are displayed. This article and Division of recapitulates the session and reproduces its educational value for the readers of CJASN. Enjoy the clinical cases Nephrology, Department of and expert discussions. Medicine, Johns Clin J Am Soc Nephrol 9: 1132–1137, 2014. doi: 10.2215/CJN.11731113 Hopkins University, Baltimore, Maryland Correspondence: Introduction: Mark A. Perazella and Michael complicated and challenging electrolyte/acid-base Dr. Biff F. Palmer, J. Choi (Comoderators) cases. Overall, an educational experience was had Department of For most American Society of Nephrology Kidney by all participants. We hope that this “distillate” Internal Medicine, Week attendees, case-based clinical nephrology talks CJASN University of Texas from Atlanta will serve the subscribers well Southwestern Medical are the most exciting venues of the meeting. The Ne- and provide some fresh insights into the complex- Center, 5323 Harry phrology Quiz and Questionnaire (NQ&Q) is the ity and vibrancy of clinical nephrology for those Hines Boulevard, essence of clinical nephrology and represents what who were unable to attend the meeting (Mark A. Dallas, TX 75390. drew many of us into the field of nephrology. The Email: biff.palmer@ Perazella, MD, Yale University, Comoderator, and utsouthwestern.edu 2013 NQ&Q in Atlanta, Georgia, with full-house at- Michael Choi, MD, Johns Hopkins University, tendance, was no exception. Each of the discussants Comoderator). prepared vignettes of puzzling cases, each illustrat- ing some topical, challenging, or controversial as- pect of the diagnosis or management of various Electrolyte Case 1: Biff F. Palmer (Discussant) areas of nephrology. These eight interesting cases A 19-year-old woman is transported to the emergency were presented and eloquently discussed by our department after being found on the floor of her four expert The American Society of Nephrology apartment unable to move. The patient states she was in (ASN) faculty. Subsequently, each discussant pre- her usual state of health up until 36 hours earlier, when pared a manuscript summarizing his or her discus- she noticed the onset of episodic but progressively sion of the cases, which serves as the main text of this worsening generalized weakness. There was no history of article. bladder or bowel incontinence or loss of consciousness. In this NQ&Q, Dr. Biff Palmer presents his two Medical history was unremarkable, and the patient challenging electrolyte/acid-base cases and elo- reported no ingestions; however, the roommate who quently synthesizes the available data to make the accompanies her says she has been acting “alittle correct diagnosis. The audience responses are re- crazy” recently. Vital signs on admission showed a tem- viewed along with the responses of training program perature of 37°C, BP of 110/60 mmHg, and pulse of directors and nephrology fellows obtained before the 95 beats/min. Physical examination is remarkable meeting. This review provides an interesting perspec- for erythematous discoloration around her lips and tive into the thought processes of nephrologists with nose and erythema of the oral and pharyngeal mucosa. varying levels of training and experience. Dr. Palmer Conjunctival injections are present. There is 2/6 reviews essential clinical and laboratory data avail- weakness in both upper and lower extremities and able in the cases and walks the reader through the generalized hyporeflexia. Laboratory data are given in diagnosis and appropriate management of these two Table 1. 1132 Copyright © 2014 by the American Society of Nephrology www.cjasn.org Vol 9 June, 2014 Clin J Am Soc Nephrol 9: 1132–1137, June, 2014 Quiz and Questionnaire 2013, Palmer 1133 choice C the correct answer (Figure 1). Signs of inhalant Table 1. Laboratory data for Case 1 abuse include drying and redness around the mouth and nose, spots or sores around the mouth, and red or runny Laboratory Test Value eyes or nose. Inhalant abuse now includes a broad range Serum creatinine (mg/dl) 1.8 of volatile solvents and gas products to include model BUN (mg/dl) 38 airplane glue, paint thinner, gasoline, and nail polish Serum electrolytes (mEq/L) remover. Na+ 136 Examination of the metabolic profile discloses evidence K+ 1.5 2 of a triple acid-base disturbance composed of anion gap Cl 105 metabolic acidosis, hyperchloremic normal gap metabolic HCO3 10 acidosis, and respiratory acidosis. One should systemati- Arterial blood gas on room air cally interpret serum chemistries in order to identify the pH 7.1 overt and, more important, the subtle abnormalities that pCO2 35 pO 110 may exist in a laboratory report (1). 2 fi Glucose (mg/dl) 132 In this regard, a useful starting point is to rst examine Albumin (g/dl) 4.2 the serum Na+ concentrationinordertodetermine Urine electrolytes (mEq/L) whether a disturbance in the plasma tonicity is present. Na+ 42 This patient’s serum Na+ is mildly reduced, suggesting a K+ 38 2 relative excess of free water. Despite the downward trend Cl 65 in Na+, the serum Cl2 concentration is increased. Changes in Urine pH 6.0 hydration status alone will cause the serum Cl2 to change in Urine urea (mg/dl) 38 parallel and to the same extent as the serum Na+ concentra- Urine osmolality (mOsm/kg) 610 tion. Whenever the serum Cl2 moves in a direction opposite or changes disproportionately to the change in serum Na+, an acid-base disorder is suggested. In this patient, the serum Question 1 Cl2 is increased with respect to the serum Na+, suggesting Which one of the following best describes the acid-base the presence of chronic respiratory alkalosis or normal anion findings in this case? gap metabolic acidosis (2). The next step is to calculate the serum anion gap. A. Proximal renal tubular acidosis Calculation of the anion gap should be a routine part of B. Renal tubular acidosis of renal insufficiency the examination of every set of electrolytes, no matter how C. Overproduction of an organic acid normal the individual values may appear. In this case, the D. Distal renal tubular acidosis anion gap is 21 mEq/L, thus identifying the presence of an anion gap metabolic acidosis as at least one of the Discussion of Case 1 acid-base disturbances in this case. This 19-year-old woman presents with severe weakness Given the anion gap metabolic acidosis, the next step is 2 in the setting of hypokalemia and metabolic acidosis to determine whether the measured serum HCO3 is equal 2 resulting from deliberate inhalation of toluene. As dis- to the predicted serum HCO3 . In general, the serum 2 cussed in more detail below, the mechanism by which the HCO3 concentration will fall by an amount equal to the acid-base disturbance develops in this setting can best be increase in anion gap. Assuming a normal value of 12, the described as overproduction of an organic acid, making anion gap has increased by 9 in this patient. One would Figure 1. | Question 1: Distribution of answers from fellows in training, training program directors (TPD), and audience members at the Kidney Week meeting. The correct answer is C. 1134 Clinical Journal of the American Society of Nephrology 2 predict the serum HCO3 should be approximately 15 of urinary ammonium by calculating the urinary anion mEq/L, assuming a normal value of 24 mEq/L (2429=15). gap (UAG): Because the measured value is 10 mEq/L, one can con- þ þ 2 clude that a normal gap hyperchloremic metabolic acido- UAG ¼ðUrine Na þ Urine K Þ 2 Urine Cl sis is also present, as suggested by the disproportionate rise in serum Cl2 concentration noted above. The expected Under normal circumstances the UAG is positive, with 2 respiratory compensation for a measured HCO3 of 10 values ranging from 30 to 50. A negative value for the UAG mEq/L in the setting of metabolic acidosis would be a suggests the presence of increased renal excretion of an + + pCO2 of approximately 25 mmHg. The measure value of unmeasured cation, a cation other than Na or K . One + 35 mmHg indicates insufficient respiratory compensation such cation is NH4 . Metabolic acidosis of extrarenal origin and confirms the presence of respiratory acidosis. The re- is associated with a marked increase in urinary ammonium mainder of the discussion will focus on the cause of each of excretion, and therefore a large negative value will be the acid-base disorders identified in this patient with tolu- obtained for the UAG.