Mid-regional plasma pro-atrial natriuretic peptide and stroke volume responsiveness for detecting deviations in central blood volume following major abdominal surgery.

Background: A reduced central blood volume is reflected by a decrease in mid-regional plasma pro-atrial natriuretic peptide (MR-proANP), a stable precursor of ANP, and a volume deficit may also be assessed by the stroke volume (SV) response to head-down tilt (HDT). We determined plasma MR-proANP during major abdominal procedures and evaluated whether the patients were volume responsive by the end of the surgery, taking the fluid balance and the crystalloid/colloid ratio into account.

Methods: Patients undergoing pancreatic (n = 25), liver (n = 25), or gastroesophageal (n = 38) surgery were included prospectively. Plasma MR-proANP was determined before and after surgery, and the fluid response was assessed by the SV response to 10 HDT after the procedure. The fluid strategy was based mainly on lactated Ringer's solution for gastroesophageal procedures, while for pancreas and liver surgery, more human albumin 5% was administered.

Results: Plasma MR-proANP decreased for patients undergoing gastroesophageal surgery (-9% [95% CI -3.2 to -15.3], p = .004) and 10 patients were fluid responsive by the end of surgery (∆SV > 10% during HDT) with an administered crystalloid/colloid ratio of 3.3 (fluid balance +1389 ± 452 ml). Furthermore, plasma MR-proANP and fluid balance were correlated (r = .352 [95% CI 0.031-0.674], p < .001). In contrast, plasma MR-proANP did not change significantly during pancreatic and liver surgery during which the crystalloid/colloid ratio was 1.0 (fluid balance +385 ± 478 ml) and 1.9 (fluid balance +513 ± 381 ml), respectively. For these patients, there was no correlation between plasma MR-proANP and fluid balance, and no patient was fluid responsive.

Conclusion: Plasma MR-proANP was reduced in fluid responsive patients by the end of surgery for the patients for whom the fluid strategy was based on more lactated Ringer's solution than human albumin 5%.