Challenging surgical dogma: are routine postoperative day 1 laboratory tests necessary after bariatric operations?

Nicholas P. McKenna, Amy E. Glasgow, Omair A. Shariq, David W. Larson, Omar M. Ghanem, Travis J. McKenzie, Elizabeth B. Habermann

Research output: Contribution to journalArticlepeer-review


Background: Postoperative day (POD) 1 laboratory tests are routinely ordered after bariatric operations. Objectives: Determine how often these laboratory tests are abnormal and whether they represent value-added care. Setting: Academic medical center, United States. Methods: Patients undergoing bariatric operations for obesity and complications from prior bariatric surgery from 1 January 2011 to 12 December 2020 at a single institution were identified. Patients with POD 1 hemoglobin, potassium, creatinine, or glucose serum laboratory tests obtained before 08:00 on POD 1 were reviewed. Laboratory-specific exclusion criteria were applied. Abnormal laboratory test results were a hemoglobin < 8.0 g/dL or a hemoglobin drop of > 3.0 g/dL; a potassium < 3.5 mmol/L (hypokalemia), 5.5–5.9 mmol/L (mild hyperkalemia), or ≥ 6.0 mmol/L (severe hyperkalemia); a creatinine increase of 0.3 g/dL or 1.5X the preoperative value (acute kidney injury); and a glucose > 180 mg/dL (hyperglycemia). Intervention for abnormal hemoglobin, potassium, and glucose was also assessed. Results: Of 2090 patients who underwent bariatric operations, 1969 met inclusion criteria for hemoglobin analysis, 1223 for potassium analysis, 1446 for creatinine analysis, and 563 for glucose analysis. Only 0.2% (n = 4) of patients had a hemoglobin < 8.0 g/dL< and only 3.1% (n = 62) had a > 3.0 g/dL hemoglobin drop. Potassium was abnormal in 2.8% of patients (n = 34 total). An acute kidney injury was diagnosed in 1.8% (n = 26) of patients. Hyperglycemia was identified in 2.1% (n = 12) of patients. Of 5227 laboratory test values, only 1.5% were abnormal. Further, of laboratory tests analyzed for intervention (n = 3781), only 14 (0.4%) were actively acted upon. Conclusions: Routine POD 1 laboratory tests after bariatric operations seem to be a continuation of a surgical tradition rather than a clinically valuable tool. POD 1 laboratory tests should be ordered based on specific patient co-morbidities and clinical criteria.

Original languageEnglish (US)
Pages (from-to)1261-1268
Number of pages8
JournalSurgery for Obesity and Related Diseases
Issue number11
StatePublished - Nov 2022


  • Bariatric surgery
  • Gastric bypass
  • Serum laboratory tests
  • Sleeve gastrectomy

ASJC Scopus subject areas

  • Surgery


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