Hypovolemic phlebotomy and low central venous pressure: a paradigm shift in liver surgery?

Preventing blood loss in liver surgery has always been a key objective for surgical teams, as bleeding is considered a major risk factor for postoperative complications. Hemorrhage affects not only short-term outcomes—such as biliary fistula and postoperative bleeding—but also long-term results, including inadequate oncological margins. In addition, excessive blood loss compromises hemodynamic stability and organ perfusion.

However, not all preventive strategies are equally effective. Total vascular exclusion of the liver, widely practiced before the 2000s with excellent results in trained teams (1), was once considered the ultimate weapon against bleeding during hepatic transection. Its significant hemodynamic consequences, however, were associated with increased postoperative morbidity (2), ultimately restricting its use to selected indications.

In open liver surgery, maintaining a low central venous pressure (CVP)—which closely reflects suprahepatic venous pressure—has emerged as a cornerstone strategy in the absence of vascular exclusion. The liver, receiving 20–25% of cardiac output and containing nearly 20% of total blood volume, is highly vascularized. During transection, bleeding may originate from portal capillaries (controlled by portal clamping) or from suprahepatic veins and sinusoids, which are directly influenced by CVP.

Several approaches have been proposed to reduce CVP, including fluid restriction, diuretics, nitroprusside, and the Trendelenburg position. Hypovolemic phlebotomy (HP)—intentional blood withdrawal after anesthesia induction without volume replacement before liver transection—offers a more direct approach. By reducing circulating blood volume, HP lowers CVP and pressure in suprahepatic veins, thereby reducing bleeding from the transection plane.

A recent double-blind randomized study by Lapisatepun et al. (3) demonstrated that HP, with or without vascular clamping, was more effective in reducing intraoperative bleeding than conventional restrictive strategies. The study’s methodological rigor deserves recognition, especially given the challenges of implementing double-blind randomization in the operating room.

These findings reinforce previous observational and retrospective studies. Ryckx et al. (4) identified HP-induced CVP reduction as an independent predictor of blood loss during liver transection. In a cohort of 100 patients, a median HP volume of 400 mL led to a 5.5 mmHg CVP decrease and a median blood loss of only 165 mL—remarkably low for major liver surgery.

The PRICE 1 feasibility study (5) reported a lower transfusion rate in the HP group compared to controls (13% vs. 33%). A recent meta-analysis (6) involving 1,759 HP patients and 1,610 controls showed significant reductions in blood loss and transfusion rates, without increased complications or hospital stay duration.

Regarding Lapisatepun et al.’s study (3), several aspects warrant closer scrutiny. Although bleeding during transection was lower in the HP group, the number of transfused red blood cell units was not significantly different between groups, raising questions about the clinical impact of the observed reduction in blood loss.

Secondly, both groups achieved CVP ≤5 mmHg, but the HP group reached this target more rapidly. This finding is noteworthy, as achieving low CVP is not always straightforward, particularly in fragile or hemodynamically unstable patients (7). Additional details regarding anesthetic management during blood withdrawal in the HP group would therefore be valuable, as this phase may be critical to both efficacy and safety. The authors suggest that faster CVP reduction explains the decreased bleeding. However, since CVP was similar equal in both groups at the start of transection, this explanation alone appears insufficient. We propose an alternative hypothesis: not all CVP-lowering methods have the same impact on bleeding, when similar CVP values are achieved. Nitroprusside, for instance, lowers CVP by relaxing the venous system (8), leading to vein dilation. A dilated vein may bleed more profusely when injured than a vein subjected to HP, fluid restriction, or diuretics, which reduce intravascular volume and may promote relative vasoconstriction—especially if blood pressure regulation is not fully suppressed by anesthesia.

Therefore, a detailled description of control group management is essential, including fluid restriction, pharmacologic treatment, and patient positioning. Such information is critical to fully interpret the comparative efficacy of HP.

Two key questions remain:

• Can HP be safely applied to fragile patients, often underrepresented in trials?
• Do allogeneic blood transfusions carry clinically relevant side effects (9,10), even at the low volumes achieved by experienced teams performing major liver surgery?

This methodologically robust study provides strong evidence that HP is currently the most effective blood-sparing strategy for major open liver surgery, likely without increased risk in low-risk patients. Further multicenter randomized trials are needed to confirm HP’s safety in high-risk populations and to demonstrate long-term benefits and cost-effectiveness.

A paradoxical yet compelling conclusion emerges: to reduce bleeding in major hepatic surgery in patients at low cardiovascular risk, one must first intentionally bleed the patient before the incision is even made!

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, HepatoBiliary Surgery and Nutrition. The article did not undergo external peer review.

Funding: None.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://hbsn.amegroups.com/article/view/10.21037/hbsn-2025-702/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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