Impact of HMS Plus Device on Postoperative Blood Loss During Cardiac Surgery
Condition: Cardiac Surgical Procedure
MeSH terms: Postoperative Hemorrhage
Study type: Observational

Summary: 
      Activated clotting times (ACT) is employed most commonly to assess anticoagulation and ensure
      adequate heparin and protamine dosing during cardiopulmonary bypass (CPB). However, many
      studies have demonstrated a lack of correlation between plasma heparin levels and ACT during
      CPB.

      HMS Plus device estimate the free plasma heparin level from a whole-blood sample and also
      include the dose of protamine necessary to neutralize the circulating heparin at the end of
      CPB. It could predict a higher heparin dose and lower protamine dose but it's interest on
      postoperative bleeding and perioperative transfusion is unclear.
    

Detailed description: 
      Adult cardiac surgery is often complicated by elevated blood losses that account for elevated
      transfusion requirements. Perioperative bleeding and transfusion of blood products are major
      risk factors for morbidity and mortality.

      Cardiac surgery is a challenge in the management of coagulation because of the requirement
      for both a fully anticoagulated state for CPB and a return-to-normal hemostasis at its
      conclusion. Conditions during CPB, such as hemodilution, hypothermia, platelet activation and
      coagulopathy are know to cause falsify elevated ACT readings. For these reasons, relying on
      the ACT alone may lead to inadequate anticoagulation.

      Moreover, no consensus about the monitoring or level of anticoagulation required has been
      reached. Similarly, the neutralization of heparin is performed with protamine (dose/dose).
      This empirical approach does not include inter- and intra-individual variations, which can
      involve bleeding complications. By using the HMS Plus, heparin and protamine dosing are
      individualized based on each patient's responsiveness to heparin, eliminating the need for
      empiric weight-based dosing.

      HMS Plus provided a rapid assessment of heparin concentration that correlated well with
      anti-Xa assays. This could attenuates this hemostatic activation by decreasing excessive
      generation of thrombin and plasmin. Also, this ensures preservation of coagulation factors
      and decreases thrombin-mediated consumption and activation of platelets during CPB.

      HMS Plus is ability to calculate the amount of circulating heparin at the end of CPB and give
      the exact dose of protamine necessary to neutralize the heparin. Targeted dosing can prevent
      excessive protamine administration and reduce protamine-induced platelet dysfunction.

      In a meta-analysis of 4 randomized controlled trials involving a total of 507 patients,
      postoperatively blood loss was lower in the HMS group compared with the control group. But
      the supporting studies were limited by small sample sizes, outdated practice techniques, not
      involve surgery at risk and have liberal transfusion practices. Moreover, studies observed
      errors in calculating the heparin bolus dose with HMS Plus if patient had an inadequate
      antithrombin level. The administration of more heparin is a cause of heparin rebound in the
      postoperative period and potentially was increasing the risk for bleeding.

      So, it would be necessary to compare ACT Plus and HMS Plus devices on postoperatively
      bleeding in a study involve patients at risk to bleeding and with a transfusion protocol.
    

Observational model: Case-Control
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        Patients undergoing elective cardiac surgery with cardiopulmonary bypass
      
Keywords: anticoagulation; cardiopulmonary bypass; heparin; protamine; postoperatively bleeding