[Preoperative iron deficiency with/without anemia-an underestimated risk factor?] / Präoperativer Eisenmangel mit/ohne Anämie ­ ein unterschätzter Risikofaktor?

BACKGROUND: Every third surgical patient already suffers from anemia before surgery. The main cause is iron deficiency. OBJECTIVE: This article describes the perioperative risk of iron deficiency with/without anemia and summarizes potential preventive measures. MATERIAL AND METHODS: Presentation of various current original papers, guidelines and own experiences from the German patient blood management network. RESULTS AND CONCLUSION: Preoperative iron deficiency with/without anemia is an underestimated risk factor for perioperative complications. The implementation of preoperative diagnostics and treatment as part of a comprehensive patient blood management reduces complications and increases patient safety.

[Impact of acute normovolemic hemodilution on primary hemostasis]. / Einfluss der akuten normovolämischen Hämodilution auf die primäre Hämostase.

BACKGROUND: Acute normovolemic hemodilution (ANH) is performed with the intention to reduce the requirement for allogeneic blood transfusions. After preoperative withdrawal of whole blood, corresponding amounts of crystalloids and/or colloids are infused to maintain normovolemia. The main benefit of ANH is the availability of whole blood containing red blood cells, clotting factors and platelets for reinfusion after removal during the dilution process. Until retransfusion whole blood components are stored at the patient's bedside in the operating theatre. AIM: It was the aim of the present investigation to analyze potential changes in ex vivo induced platelet aggregation in stored blood components. MATERIAL AND METHODS: After obtaining approval 15 patients undergoing complex cardiac surgery were enrolled into this prospective observational study. Acute normovolemic hemodilution (ANH) was routinely performed in this collective based on institutional standards. Besides analyses of pH and plasma concentrations of ionized calcium and hemoglobin, hematological analyses included aggregometric measurements using multiple electrode aggregometry (MEA, Multiplate®, Roche, Grenzach, Germany). Ex vivo platelet aggregation was induced using arachidonic acid (ASPI test), as well as thrombin receptor activating peptide (TRAP test) and adenosine diphosphate (ADP test). Laboratory analyses were performed before beginning ANH (baseline), as well as immediately (T1), 30 min (T2), 60 min (T3), 90 min (T4), 120 min (T5), 150 min (T6) and 180 min (T7) after beginning of storage. The areas under the aggregation curves (AUC) in the MEA were defined as primary (ASPI test) and secondary endpoints (ADP test, TRAP test). RESULTS: As compared to baseline, arachidonic acid induced platelet aggregation was significantly reduced at T1 [77 U (68/94 U) vs. 53 U (25/86 U), p = 0.003] and each consecutive measuring point. As compared to T1 (begin of storage), arachidonic acid induced platelet aggregation was significantly reduced at T4 [26 U (14/54 U); p = 0.002], T5 [30 U (21/36 U); p = 0.007], T6 [25 U (17/40 U); p = 0.004] and T7 [28 U (17/39 U); p < 0.001]. The extent of ex vivo induced platelet aggregation in the TRAP test and ADP test remained unchanged during the study period. The pH as well as the concentrations of ionized calcium and hemoglobin remained unchanged in the blood component during storage. CONCLUSION: The results of the present study indicate that disturbances of platelet aggregation may occur during storage of whole blood components prepared for the purpose of ANH. Further investigations are needed to analyze whether the observed phenomena are of hemostatic relevance.

Effects of hyperoxic ventilation on 6-h survival at the critical haemoglobin concentration aggravated by experimentally induced tachycardia in anaesthetized pigs.

AIM: Administration of 100% oxygen [hyperoxic ventilation (HV)] has been proven to ameliorate oxygen transport, tissue oxygenation and survival in different models of extreme normovolemic and hypovolemic anaemia. However, up to date, it is unknown whether HV is also able to improve outcome of extreme anaemia if myocardial oxygen consumption is contemporaneously increased by tachycardia. Therefore, we investigated the influence of HV on the 6-h survival rate during extreme anaemia and aggravated by experimentally induced tachycardia in a prospective, randomized study in a pig model of critical anaemia. METHODS: After government approval, 14 anesthetized pigs mechanically ventilated on room air were haemodiluted by replacing a certain amount of whole blood with hydroxethyl starch 6% (200.000/0.5) until their individual critical haemoglobin concentration (Hb(crit)) was achieved. At Hb(crit), tachycardia (180 bpm) was induced in all animals by atrial pacing. Thereafter, animals were observed for the next 6 h either at room air (FiO(2) 0.21; group NOX) or during HV (FiO(2) 1.0; group HOX) without further intervention. As primary outcome parameter of this study, the 6-h survival rate was selected. RESULTS: Hyperoxic ventilation increased the 6-h survival rate from 14 to 100%. In contrast to the NOX group, macrohaemodynamics and oxygen transport improved in the HOX group during the observation period without apparent adverse effects of HV. CONCLUSIONS: Hyperoxic ventilation can be considered a safe and effective measure for the optimization of oxygen supply during extreme anaemia and despite concomitant tachycardia within 6 h. Whether HV can also be recommended beyond this period warrants further studies.