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A safe and noninvasive test for vagal integrity revisited
Nagammapudur S Balaji1, Peter F Crookes, Farzaneh Banki
1Department of Surgery, University of Southern California, Los Angeles, CA 90033, USA.
Hypothesis:
Measurement of pancreatic polypeptide (PP) response to sham feeding and pharmacological stimulation is a safe, noninvasive, and sensitive test for vagal integrity.
Design:
Interventional study with control arms.
Setting:
Tertiary center for esophageal surgery.
Patients:
Thirty healthy volunteers and 25 patients who underwent total esophagectomy formed the control group with intact vagi and known vagotomy, respectively.
Intervention:
Blood samples were obtained 15 minutes before and immediately before sham feeding to determine basal PP levels. Samples were also obtained 15, 30, 45, and 60 minutes after the sham feeding and 10 and 20 minutes after administration of 5 mg of intravenous edrophonium hydrochloride.
Main Outcome Measure:
Pancreatic polypeptide response to sham feeding and edrophonium administration were compared in both groups and the optimal percentage of rise from basal levels with maximal sensitivity and specificity was determined.
Results:
Basal levels were similar in both groups (50 vs 45 ng/L). The maximum percentage of rise within 30 minutes after sham feeding was significantly higher in healthy subjects than in patients who underwent vagotomy (P<.001). A rise of 50% was seen in 24 (83%) of the 29 healthy subjects vs 2 (8%) of the 25 patients who underwent vagotomy (P<.001). This rise in PP level had a sensitivity of 83%, specificity of 92%, and a positive predictive value of 92% for identifying an intact vagus. The administration of endrophonium did not improve these results.
Conclusions:
A rise of more than 50% in the PP level within 30 minutes of sham feeding is a strong indicator of vagal integrity. This test has the potential to investigate vagal injury after gastroesophageal surgery.