Comparison of portable blood-warming devices under simulated pre-hospital conditions: a randomised in-vitro blood circuit study

Traumatisme et température

Le patient traumatisé est exposé à l’hypothermie. La mortalité des traumatisés hypothermes est multipliée par quatre ou cinq. Les interactions de l’hypothermie avec l’hémostase et le système cardiovasculaire sont délétères. Les effets sur la coagulation sont multiples et concourent directement à la surmortalité faisant de l’hypothermie une composante majeure de la « triade létale ». Les causes d’hypothermie chez le patient traumatisé sont multiples : 1) environnementales, le risque augmente quand la température ambiante diminue ; 2) cliniques, le risque augmente avec la gravité ; et aussi 3) thérapeutiques, par exemple par la perfusion de solutés à température ambiante. Une prise en charge optimale repose sur une mesure précoce et un monitorage continu de la température corporelle. L’objectif thérapeutique est de maintenir une température corporelle au moins égale à 36 °C. Limiter le déshabillage du patient, le protéger du froid avec une couverture de survie, l’installer rapidement dans une ambulance chauffée, recourir à des dispositifs de réchauffement actifs, perfuser des solutés réchauffés sont les éléments fondamentaux de la prise en charge d’un patient traumatisé, potentiellement hypotherme.

Effect of warming and infusion of red blood cell concentrates on markers of haemolysis: An ex vivo simulation study

BACKGROUND

Transfusion of red blood cell (RBC) concentrates is a common procedure to restore blood volume and tissue oxygen delivery in patients with trauma. Although RBC warmers may prevent hypothermia, some warming or infusion equipment may lead to haemolysis and patient injury.

OBJECTIVES

The aim of this study was to test the effect of (i) RBC warming and (ii) administration via manual vs. pump infusion on haemolysis.

METHODS

This experimental ex vivo study studied haemolysis markers of RBC injury. The sample consisted of 90 RBC infusions in two simulations, randomly, 45 warmed RBC infusions and 45 nonwarmed RBC infusions, in two or three stages: before the intervention (baseline-warming, N= 45; nonwarming, N= 45), after water bath warming at 42 °C (warmed, N= 45), and then after the warmed or nonwarmed RBCs were infused by manual or pump infusion at a rate of 100 mL/h (infusion-warming, N= 45; nonwarming, N= 45).

RESULTS

Warmed RBCs showed significantly lower total haemoglobin (Hb) and haematocrit levels and increase in free Hb levels, haemolysis levels, and lactate dehydrogenase (LDH) activity (all p<0.05) than baseline RBCs. Pump infusion RBCs were associated with reduced total Hb and increased free Hb, haemolysis, and potassium (K) levels (all p<0.05) compared with warmed RBCs. In contrast, manual infusion of warmed RBCs resulted in significantly reduced total Hb levels and increased LDH activity (both <0.05). After infusion, total Hb, free Hb, haematocrit, haemolysis, and LDH values were significantly different for warmed vs. nonwarmed RBCs (p<0.05).

CONCLUSIONS

Haemolysis biomarkers increase with RBC warming and infusion, especially when using infusion pumps. Critically ill patients should be carefully monitored for possible complications during and after RBC infusion.

Warming blood products for transfusion to neonates: In vitro assessments

BACKGROUND

Blood products may be transfused into neonates at temperatures at or below room temperature. The benefits and risks of warming blood to 37°C are not defined in this population or with the equipment used in neonates. Physiologic warming might enhance product effectiveness or decrease transfusion-associated hypothermia.

STUDY DESIGN AND METHODS

We utilized an in vitro model of neonatal transfusions, with a syringe pump, blood tubing, and 24-gauge catheter and compared current practice (cold products) vs an inline blood warmer. Transfusions were performed rapidly (30 minutes) and slower (120 minutes) to model emergent vs routine situations. We tested red blood cells, fresh-frozen plasma, apheresis platelets (PLTs), and cold-stored low-titer group O whole blood. We used infrared detectors and inline probes to measure temperatures at the origin and at the simulated patient. We assessed warmer-induced damage by measuring plasma hemoglobin and hematocrit (seeking hemolysis), fibrinogen (seeking activation of coagulation), and PLT count and TEG-MA (seeking PLT destruction or dysfunction).

RESULTS

The cold-stored products were 4.2 ± 1.0°C (mean ± SD) at the origin and 21.5 ± 0.1°C at the patient. With the inline warmer, products were 37.8 ± 0.6°C at the warmer and 32.6 ± 1.7°C at the patient during a 30-minute infusion, but were 34.5 ± 2.1 with a foil sheath covering the terminal tubing. We found no warmer-induced damage using any metric.

CONCLUSION

In simulated neonatal intensive care unit (NICU) transfusions, an inline blood warmer can deliver blood products at near-physiologic temperatures with no detected damage. We suggest in vivo testing of warmed NICU transfusions, assessing product effectiveness and hypothermia risk reduction.