Unfolding Case: The Panel That Moved
A trend sparkline strip of seven stacked lanes, one per analyte, each carrying a three-point sparkline against a pale reference band, with out-of-band segments switching color, the analyte name and current value at the left of each lane, the signed delta at the right, and a bracket marking the two lanes that stay inside their band while climbing steeply.
The case
0700, admission. A 62-year-old adult arrives for observation after two days of vomiting and poor oral intake. Alert, oriented, dry mucous membranes, reports lightheadedness on standing. Heart rate 96, blood pressure 118/70 lying and 102/62 sitting. Admission panel drawn.
1500, eight hours. Vomited twice more overnight, tolerating sips only. Urine output has fallen to a dark, concentrated 20 mL per hour. Heart rate 104. Reports generalized weakness and cramping in the calves. Second panel drawn.
2300, sixteen hours. Weaker, needs two-person assist to stand, reports the muscle cramping is worse. Bowel sounds hypoactive. Heart rate 108 with occasional irregularity noted on auscultation. Third panel drawn.
Serial panel
| Analyte | 0700 | 1500 | 2300 | Δ over 16 h | Reference |
|---|---|---|---|---|---|
| Sodium | 138 | 142 | 145 | +7 | 135–145 mEq/L |
| Potassium | 3.7 | 3.3 | 3.0 | −0.7 | 3.5–5.0 mEq/L |
| Chloride | 99 | 95 | 91 | −8 | 98–106 mEq/L |
| Bicarbonate | 26 | 29 | 32 | +6 | 22–26 mEq/L |
| BUN | 18 | 26 | 34 | +16 | 10–20 mg/dL |
| Creatinine | 0.8 | 0.9 | 1.1 | +0.3 | 0.6–1.2 mg/dL |
| Glucose | 94 | 88 | 86 | −8 | 70–99 mg/dL |
Step 1 · CUE. Which values moved the most, and in which direction? Potassium fell 0.7 mEq/L and is now below its range. Chloride fell 8 mEq/L and is below its range. Bicarbonate rose 6 mEq/L and is above its range. BUN rose 16 mg/dL. Sodium and creatinine are both still inside their ranges and both are climbing steeply, which is the finding most candidates skip.
Step 2 · ANA. Which of these move together, and why? Chloride is lost in vomit as hydrochloric acid, bicarbonate rises to fill the space, and the pattern is a metabolic alkalosis. Alkalosis pulls potassium into the cell, so the serum potassium falls faster than the total body loss alone would explain. BUN rising far ahead of creatinine, and a ratio moving from about 22:1 to about 31:1, is a volume problem, not a kidney problem. Sodium climbing inside its range is free water loss.
Step 3 · PRI. Which abnormality is most likely to harm this patient first? The potassium at 3.0 mEq/L and still falling, because it is the one with an immediate rhythm consequence, and the newly irregular pulse says the heart has already noticed.
Step 4 · SOL. Three candidate actions. Which are defensible? (a) Obtain a 12-lead ECG, place the patient on continuous cardiac monitoring, and check the magnesium alongside the potassium. (b) Continue to monitor and recheck the panel in the morning. (c) Encourage oral fluids and re-offer the diet tray.
Step 5 · ACT. What is the single first action, and what assessment precedes it? Assess the apical pulse for a full minute and check level of consciousness, then place the patient on continuous cardiac monitoring and obtain the ECG, then notify the provider of the falling potassium, the falling chloride, and the rising bicarbonate together. The assessment is the action's first half, not a delay to it.
Step 6 · EVA. What tells you it worked, and when do you look? A repeat panel in four to six hours showing potassium at or above 3.5 mEq/L, chloride rising back toward 98 mEq/L, and BUN falling. At the bedside: urine output rising and lightening in color, resolution of the calf cramping, and no ectopy on the monitor.
Margin notenothing here is critical yet, and that is the point.
☐ CUE ☐ ANA ☐ PRI ☐ SOL ☐ ACT ☐ EVA
→ BOOK 02 · P3 for the clinical judgment loop. → BOOK 10 · P5 for the condition behind this trend, which this page deliberately never names.
Takeawaya trend can require action while every individual value is still inside its range.
Reference ranges vary between institutions and reference laboratories. Follow local protocol.