Lactate dehydrogenase and Haemolysis Index as quality control markers of haemolysis in intra-operative cell salvage

Hemolysis Index Correlations with Plasma-Free Hemoglobin and Plasma Lactate Dehydrogenase in Critically Ill Patients under Extracorporeal Membrane Oxygenation or Mechanical Circulatory Support-A Single-Center Study

Monitoring for thrombosis and hemolysis is crucial for patients under extracorporeal or mechanical circulatory support, but it can be costly. We investigated correlations between hemolysis index (HI) and plasma-free hemoglobin (PFH) levels on one hand, and between the HI and plasma lactate dehydrogenase (LDH) levels on the other, in critically ill patients with and without extracorporeal or mechanical circulatory support. Additionally, we calculated the cost reductions if monitoring through HI were to replace monitoring through PFH or plasma LDH. In a single-center study, HI was compared with PFH and plasma LDH levels in blood samples taken for routine purposes in critically ill patients with and without extracorporeal or mechanical circulatory support. A cost analysis, restricted to direct costs associated with each measurement, was made for an average 10-bed ICU. This study included 147 patients: 56 patients with extracorporeal or mechanical circulatory support (450 measurements) and 91 patients without extracorporeal or mechanical circulatory support (562 measurements). The HI correlated well with PFH levels (r = 0.96; p < 0.01) and poorly with plasma LDH levels (r = 0.07; p < 0.01) in patients with extracorporeal or mechanical circulatory support. Similarly, HI correlated well with PFH levels (r = 0.97; p < 0.01) and poorly with plasma LDH levels (r = -0.04; p = 0.39) in patients without extracorporeal or mechanical circulatory support. ROC analyses demonstrated a strong performance of HI, with the curve indicating excellent discrimination in the whole cohort (area under the ROC of 0.969) as well as in patients under ECMO or mechanical circulatory support (area under the ROC of 0.988). Although the negative predictive value of HI for predicting PFH levels > 10 mg/dL was high, its positive predictive value was found to be poor at various cutoffs. A simple cost analysis showed substantial cost reduction if HI were to replace PFH or plasma LDH for hemolysis monitoring. In conclusion, in this cohort of critically ill patients with and without extracorporeal or mechanical circulatory support, HI correlated well with PFH levels, but poorly with plasma LDH levels. Given the high correlation and substantial cost reductions, a strategy utilizing HI may be preferable for monitoring for hemolysis compared to monitoring strategies based on PFH or plasma LDH. The PPV of HI, however, is unacceptably low to be used as a diagnostic test.

Oxygen carrying capacity of salvaged blood in patients undergoing off-pump coronary artery bypass grafting surgery: a prospective observational study

BACKGROUND

Intraoperative cell salvage (ICS), hereby referred to 'mechanical red cell salvage', has been widely used and proven to be an effective way to reduce or avoid the need for allogeneic red blood cells (RBCs)transfusion and its associated complications in surgeries involving major blood loss. However, little is known about the influence of this technique on the functional state of salvaged RBCs. Furthermore, there are no articles that describe the change of free hemoglobin (fHb) in salvage blood during storage, which is a key index of the quality control of salvaged blood. Therefore, in this study, the influence of ICS on the function of salvaged RBCs and the changes of salvaged RBCs during storage were studied with respect to the presence of oxyhemoglobin affinity (recorded as a P50 value) and the level of 2, 3-diphosphoglycerate (2, 3-DPG) and fHb by comparing salvaged RBCs with self-venous RBCs and 2-week-old packed RBCs.

METHODS

Fifteen patients undergoing off-pump coronary artery bypass grafting (OPCAB) surgery were enrolled. Blood was collected and processed using a Dideco Electa device. The level of P50, 2, 3-DPG and fHB from salvaged RBCs, venous RBCs and 2-week-old packed RBCs was measured. We also measured the changes of these indicators among salvaged RBCs at 4 h (storage at 21-24 °C) and at 24 h (storage at 1-6 °C).

RESULTS

The P50 value of salvaged RBCs at 0 h (28.77 ± 0.27 mmHg) was significantly higher than the value of venous RBCs (27.07 ± 0.23 mmHg, p=0.000) and the value of the 2-week-old packed RBCs (16.26 ± 0.62 mmHg, p=0.000). P50 value did not change obviously at 4 h (p=0.121) and 24 h (p=0.384) compared with the value at 0 h. The 2, 3-DPG value of salvaged RBCs at 0 h (17.94 ± 6.91 μmol/g Hb) was significantly higher than the value of venous RBCs (12.73 ± 6.52 mmHg, p = 0.007) and the value of the 2-week-old packed RBCs (2.62 ± 3.13 mmHg, p=0.000). The level of 2, 3-DPG slightly decreased at 4 h (p=0.380) and 24 h (p=0.425) compared with the value at 0 h. Percentage of hemolysis of the salvaged blood at 0 h(0.51 ± 0.27 %) was significantly higher than the level of venous blood (0.07 ± 0.05 %, p=0.000) and the value of 2-week-old packed RBCs (0.07 ± 0.05 %, p=0.000), and reached 1.11 ± 0.42 % at 4 h (p=0.002) and 1.83 ± 0.77 % at 24 h (p=0.000).

CONCLUSIONS

The oxygen transport function of salvaged RBCs at 0 h was not influenced by the cell salvage process and was better than that of the venous RBCs and 2-week-old packed RBCs. At the end of storage, the oxygen transport function of salvaged RBCs did not change obviously, but percentage of hemolysis significantly increased.

Quick biochemical markers for assessment of quality control of intraoperative cell salvage: a prospective observational study

BACKGROUND

Intraoperative Cell Salvage (ICS), hereby referred to 'mechanical red cell salvage', has been widely used in adult elective major surgeries to reduce requirement for homologous red blood cell transfusion and its associated complications. However, amount of free haemoglobin (fHb) from ICS has been shown related to incidence of renal failure. fHb is the most important indicator of quality control of cell salvaged blood, thus monitoring the fHb concentration is imperative to minimise renal injury. However, currently there has been lacking quick biochemical markers to monitor the levels of fHb during ICS. The aim of this study was to screen quick biochemical markers for evaluating the amount of fHb during use of intraoperative cell salvage.

METHODS

Twenty patients undergoing elective cardiovascular surgery were enrolled. Blood was collected and processed using a Fresenius continuous auto-transfusion system device. The concentration of fHb, albumin (Alb), and calcium (Ca) in three washing modes were measured, and their clearance rates were calculated. The correlations among the clearances and concentrations of fHb, albumin, and calcium were analysed.

RESULTS

In three washing modes, concentrations of albumin and calcium are significantly associated with amount of fHb:fHb(g/L) = 0.111 Alb(g/L) -0.108, R = 0.638, p = 0.000; fHb(g/L) = 1.721 Ca(mmol/L) +0.091, R = 0.514, p = 0.000. Furthermore, the clearance rates of albumin and calcium significantly predict clearance of fHb, CR(fHb) = 0.310 CR(ALB) + 0.686, R = 0.753, p = 0.000, CR(fHb) = 0.073 CR(Ca) + 0.913, R = 0.497, p = 0.000.

CONCLUSIONS

In clinic practice, clearance rates of albumin, or calcium can be used to evaluate the quality of salvaged blood, fHb. Bed-side measurement of calcium could offer a more feasible means for clinicians to undertake a real-time assessment of fHb.