Mechanical Hemolysis Research Articles

Hemoglobinuria and Mechanical Hemolysis Associated with Red Blood Cell Transfusion in Pediatric Patients

AbstractAbstract 3429 Introduction:Mechanical hemolysis is a non-immune mediated destruction of red blood cells that can be associated with blood transfusion. Various etiologies include the use of blood warmers, small bore needles or high infusion rates. We report the investigation of hemoglobinuria cases observed post-packed red blood cell (PRBC) transfusion with subsequent changes in management. Case report:Over a time period of 2 months, 6 events of hemoglobinuria and hemolysis were reported in 5 patients in the pediatric hematology/oncology treatment center. Each child presented with abnormally tea-colored urine following PRBC transfusion. Transfusion reaction workup included a direct antiglobulin test (DAT), urinalysis (UA), serum haptoglobin (H), lactate dehydrogenase (LDH), and total bilirubin (T-B). All patients had a negative or unchanged DAT, negative RBC antibody screen, decreased H, increased T-B, and increased LDH (4 out of 6), suggestive of intravascular hemolysis (Table). In spite of hemolysis, hemoglobin (Hgb)/hematocrit(Hct) increased normally. Multiple factors were investigated to determine a cause: collection and processing of blood units; handling of blood at the transfusion service; and blood administration by nursing staff. The only significant change identified was the implementation of a new infusion pump (pump A) replacing a model that was phased out. A hospital-wide retrospective review of urinalysis (UA) was performed over a one month time period, along with prospective UA surveillance in the outpatient unit.CaseDateUnitSAge (yr)DiagnosisUA Dipstick Blood/RBCLDH (U/L)H (mg/dL)T-B (mg/dL)DAT16/7/12CPDA1F4RMS3+/0-3637131.4Neg26/12/12CPDA1 × 3M10ALL2+/0-233190.5Neg36/29/12CPDA1M4DBA3+/0-3364<81.6Pos*47/9/12AS-5F7ALLNeg/0-3–<83.3Neg57/14/12CPDA1 × 2F11PTLD2+/0-3338<82.3Neg67/18/12AS-5 × 2M10ALLTrace/0-3400<82.8NegPatient 2 and 6 are identical.Corrective actions: 7/13- Pressure sensors changed from 12 to 6psi; 7/16- CPDA1 units replaced by AS-5 in children over 9 months; 7/23- Pump A replaced by pump B in out-patient unit.Abbreviations: S-Sex; RMS:Rhabdomyosarcoma; ALL-Acute Lymphoblastic leukemia; PTLD-Post Transplant Lymphoproliferative disorder; DBA Diamond Blackfan Anemia; DAT-Direct antiglobulin test; LDH- Lactate Dehydrogenase; H- Haptoglobin; T-B-Total Bilirubin. Normal values: LDH <340 U/L; H: 35–278mg/dL; T-B <1.4 mg/dL. CPDA-Citrate Phosphate buffer; AS-Additive solution.*DAT was unchanged from pre-transfusion. Results:In the 6 cases, a total of 10 irradiated PRBC units (7 with citrate phosphate dextrose buffer (CPDA1, HCT 65–80%) and 3 with additive solution (AS-5, HCT 55–65%)) were transfused. Although Pump A had been validated by the manufacturer with non-irradiated additive solution units, an in vitro study with irradiated CPDA1 RBC units was performed to compare pump A with an alternative pump B. Samples were taken after infusion using the pumps only (no needle or catheter) and dripped directly into the test tube for measurement of free hemoglobin (FHb). Irradiated CPDA1 units infused at a low rate (50ml/hr) showed an increase in FHb level at 1998mg/dL with pump A versus 496 mg/dL with pump B. Non-irradiated AS-5 units tested as controls resulted in a FHb level at 246mg/dL with pump A versus 117mg/dL with pump B. CPDA1 units were subsequently replaced with AS-5 units for transfusion. Finally, pump A was replaced by pump B in the outpatient hematology oncology unit. In vitro studies are still ongoing to determine if irradiation of the PRBC may also play a role in the mechanical hemolysis observed with pump A.One month retrospective UA review found no association between patients with hemoglobinuria and RBC transfusion. The UA prospective surveillance performed in the outpatient unit revealed that 7 of 26 patients had trace hemoglobinuria. Each one had a confounding factor (chronic hemolysis) for hemoglobinuria. Conclusion:Preliminary investigation determined that the infusion of highly concentrated irradiated RBC (CDPA1) using a specific commercial pump was associated with mechanical hemolysis. The change to less concentrated RBC units through an alternative pump has been to date, an effective corrective action. Disclosures:No relevant conflicts of interest to declare.

Protocolo diagnóstico de las anemias hemolíticas

The hemolytic anemias diagnosis remains a clinical challenge. Once a presumptive diagnosis is made based on clinical and laboratory data, the first step is to perform a direct Coombs test. If it is positive, the evaluation should de pointed towards immune haemolytic anemias, among which those mediated by aloantibodies, autoantibodies or drug-related are the most prominent. If the direct Coombs test is negative, we should consider the non-immune haemolytic anemias. The peripheral blood smear review and the familiy history are highly valuable in the diferential diagnosis. Mechanical hemolysis and congenital haemolytic anemias (membrane defects, enzimopathies, hemoglobinopathies, thalassemias…) are the main possibilities.

Red blood cell endothelial nitric oxide synthase does not modulate red blood cell storage hemolysis

The red blood cell (RBC) endothelial nitric oxide synthase (eNOS) has been shown to regulate intrinsic RBC rheologic properties, such as membrane deformability, suggesting that a functional eNOS could be important in RBC viability and function during storage. This study examines the correlation between RBC eNOS deficiency and the propensity of RBCs to hemolyze under selected stress conditions including prolonged hypothermic storage. Fresh or stored RBCs from normal and eNOS knockout (KO) mice or from healthy human volunteers were subjected to selected hemolytic stress conditions including mechanical stress hemolysis, osmotic stress hemolysis, and oxidation stress hemolysis and evaluated during standard storage in CPDA-1 solutions. Fresh RBCs from normal and eNOS KO mice demonstrated comparable susceptibility to hemolysis triggered by mechanical stress (mechanical fragility index 6.5 ± 0.5 in eNOS KO vs. 6.4 ± 0.4 for controls; n = 8-9), osmotic stress, and oxidative stress. Additionally, RBCs from both mouse groups exhibited similar hemolytic profile at the end of 14-day hypothermic storage, analogous to 42 days of human RBC storage. Storage of human RBCs (28 days in CPDA-1) in the presence of NOS cofactors (L-arginine and tetrahydro-L-biopterin) or inhibitor (N(5) -[imino(methylamino)methyl]-L-ornithine monoacetate) did not affect cell recovery or hemolytic response to the selected stressors. These studies suggest that RBC eNOS does not modulate susceptibility to hemolysis in response to selected stress conditions or prolonged hypothermic storage. Other strategies to increase nitric oxide (NO) bioactivity after prolonged storage utilizing NOS-independent pathways such as the nitrate-nitrite-NO pathway may prove a more promising approach.

Influence of mechanical hemolysis of blood on two D-dimer immunoassays

Although there is broad information about the influence of spurious hemolysis on several laboratory tests, less is known on the bias produced on D-dimer testing. Four different pools were obtained from primary blood tubes, and each of them was divided into four aliquots. The first nonhemolyzed was centrifuged, the plasma was separated and then tested for hemolysis index and D-dimer. The second (hemolyzed aliquot A), third (hemolyzed aliquot B) and fourth (hemolyzed aliquot C) aliquots were mechanically hemolyzed by aspirating whole blood one, two and three times through a fine needle. The plasma was then separated and tested for hemolysis index and D-dimer. D-dimer was quantified by HemosIL AcuStar D-dimer and HemosIL D-dimer HS for ACL TOP. Undetectable hemolysis was present in aliquot nonhemolyzed (<0.5 g/l), whereas the concentration of cell-free hemoglobin significantly increased from hemolyzed aliquot A (5.5-7.0 g/l hemoglobin) to hemolyzed aliquot B (11.5 and 15.0 g/l hemoglobin) and hemolyzed aliquot C (20-22 g/l hemoglobin). The plasma concentration of D-dimer decreased from aliquots nonhemolyzed to hemolyzed aliquot C, achieving clinical significance fromhemolyzed aliquot A and hemolyzed aliquot B when measured with D-dimer HS for ACL TOP and AcuStar D-dimer, respectively. The decrease with AcuStar D-dimer was -5 ± 3% in hemolyzed aliquot A, -7 ± 3% in hemolyzed aliquot B, and -9 ± 3% in hemolyzed aliquot C, whereas the decrease with D-dimer HS for ACL TOP was -5 ± 3% in hemolyzed aliquot A, -8 ± 3% in hemolyzed aliquot B and -9 ± 3% in hemolyzed aliquot C. The similar trend towards decreasing values observed when measuring D-dimer with chemiluminescent and turbidimetric immmunoassays on four heterogeneous plasma pools suggest that the hemolysis interference is more likely to be biological than analytical. The modest bias observed in samples with frank hemolysis (i.e. cell-free hemoglobin of 11.5 g/l) confirms that both methods are robust against this type of interference, so that test results might be released in the majority of mildly hemolyzed samples.

Computational prediction of mechanical hemolysis in aortic valved prostheses

The paper reports the prediction of mechanical hemolysis by three different models for the case of blood flow through aortic valved prostheses. Two of the adopted models are based on the action of instantaneous shear stress on the blood cells (stress-based), while the third accounts for the finite response time of cell deformation and relaxation (strain-based). Two aortic Dacron grafts commonly adopted in clinical practice are considered, and both are equipped with a bileaflet mechanical valve. One of the grafts reproduces the three sinuses of Valsalva, while the other is a straight tube. A direct numerical simulation approach is utilized to solve the complex fluid-structure-interaction problem and obtain detailed information of the flow patterns. To evaluate hemolysis, a large number of Lagrangian tracer particles were released at the inlet of the computational domain (upstream of the valve), and blood damage was evaluated along each trajectory for each model. We found that stress-based models predict higher levels of blood damage than the strain-based one. The same level of blood damage is observed in the two geometric configurations we considered, indicating that the adopted mechanical valve is primary risk factor for hemolysis.

C113 力学的要因による溶血現象の解明に向けた赤血球膜破断の分子動力学シミュレーション(C1-3 軟組織・血液のバイオメカニクス2)

C113 力学的要因による溶血現象の解明に向けた赤血球膜破断の分子動力学シミュレーション(C1-3 軟組織・血液のバイオメカニクス2)

Erythrocyte mechanical fragility is increased in patients with type 2 diabetes

BackgroundAnemia is common among patients with type 2 diabetes. We determined whether type 2 diabetic patients significantly differed in erythrocyte mechanical fragility as compared with nondiabetic subjects. MethodsWe recruited 25 Caucasian patients with type 2 diabetes (14 men and 11 women; mean age 58±8years) and 25 age-, race- and sex-matched nondiabetic individuals. The fragility of erythrocytes was tested by inducing mechanical hemolysis by double aspiration of K2EDTA blood through a 0.5mL insulin syringe equipped with a very thin needle. The plasma was then separated from the blood cells by centrifugation at 2000xg for 15min at room temperature. A Beckman Coulter DxC 800 was used to measure the hemolysis index by direct spectrophotometry. ResultsCompared with matched nondiabetic controls, type 2 diabetic patients had a significantly increased mechanical fragility of erythrocytes (hemolysis index ratio 21±13 vs. 14±10, p=0.02). Univariable linear regression analysis revealed that there was a strong positive association between percent hemolysis and fasting plasma glucose (r=0.669, p<0.001) and hemoglobin A1c (r=0.549, p<0.005) in type 2 diabetic subjects, but not in matched nondiabetic controls. ConclusionsOur data suggest that patients with type 2 diabetes have a significantly higher erythrocyte mechanical fragility than matched nondiabetic subjects, and that fasting plasma glucose is the strongest correlate of increased mechanical fragility of erythrocytes in this patients group.

Percussion hemoglobinuria - a novel term for hand trauma-induced mechanical hemolysis: a case report

IntroductionExtracorpuscular hemolysis caused by mechanical trauma has been well described in relation to lower extremity use, such as in soldiers and runners. Terms such as "march hemoglobinuria", "foot strike hemolysis" and "runners hemoglobinuria" have previously been coined and are easily recalled. Newer cases, however, are being identified in individuals vigorously using their upper extremities, such as drum players who use their hands to strike the instrument. Given the increased recognition of upper extremity-related mechanical hemolysis and hemoglobinuria in drummers, and the use of hand drumming worldwide, we would like introduce a novel term for this condition and call it "percussion hemoglobinuria".Case presentationA 24-year-old Caucasian man presented with reddish brown discoloration of his urine after playing the djembe drum. Urine examination after a rigorous practice session revealed blood on the dipstick, and 0 to 2 red blood cells per high power field microscopically. The urine sample was negative for myoglobulin. Other causes of hemolysis and hematuria were excluded and cessation of drum playing resulted in resolution of his symptoms.ConclusionsThe association of mechanical trauma-induced hemoglobinuria and playing hand percussion instruments is increasingly being recognized. We, however, feel that the true prevalence is higher than what has been previously recorded in the literature. By coining the term "percussion hemoglobinuria" we hope to raise the awareness of screening for upper extremity trauma-induced mechanical hemolysis in the evaluation of a patient with hemoglobinuria.

Modeling of Mechanical Blood Damage: a Discussion of Current Approaches and Alternative Proposals

In artificial organs such as vascular prostheses and detoxification devices, blood is exposed to mechanical stresses that can damage red blood cells, possibly leading to membrane lysis. In this work a theoretical analysis of mechanical hemolysis in artificial organs is presented, by firstly considering the main features of the current modeling approaches in literature. Two alternative modeling approaches, based on a physical description of the hemolysis process, are then presented, discussed and compared with experimental data.

The impact of suctioning RBCs from a simulated operative site on mechanical fragility and hemolysis

BackgroundIntraoperative cell salvage exerts shear stress upon RBCs, particularly as they are suctioned from the surgical field. Shear stress can result in overt hemolysis or it can cause sublethal injury to the suctioned RBCs. The mechanical fragility (MF) test uses shear stress to measure the extent of RBC sublethal injury. RBCs that have sustained sublethal injury are more susceptible to shear stress induced hemolysis. In this study we suctioned whole blood samples from an artificial surgical field to determine if pre-menopausal female RBCs would demonstrate greater resistance to hemolysis and less sublethal injury compared to that of males and post-menopausal females.MethodsTen CPD-preserved whole blood units from these 3 donor groups were obtained and samples suctioned at -150 mmHg from a simulated surgical field. The MF test was then performed and the % hemolysis calculated. In addition the MF test was serially performed on these whole blood units during the 21 days of storage.ResultsThere were no differences in the extent of hemolysis or RBC shear stress resistance after suctioning between the 3 donor groups. During storage the pre-menopausal female RBCs demonstrated higher shear stress tolerance compared to the males or post-menopausal females at all of the time points.ConclusionAlthough during static storage pre-menopausal female RBCs in CPD-preserved whole blood demonstrated higher shear stress tolerance, this enhanced resistance was not observed after suctioning from a simulated surgical field.

Prospective Evaluation of the Rate and Impact of Hemolysis on Intraoperative Parathyroid Hormone (IOPTH) Assay Results

Intraoperative parathyroid hormone (IOPTH) is commonly used during minimally invasive parathyroidectomy. Retrospective evidence suggested that hemolysis may artificially lower IOPTH results. Falsely decreased IOPTH measurements could result in either failed parathyroidectomy or unnecessary bilateral neck exploration. A total of 130 IOPTH specimens from 30 patients were assayed before and after induction of mechanical hemolysis using a vortex and inert sterile glass beads. Free hemoglobin (Hg) was measured as a surrogate for extent of hemolysis. Paired sample t test was used for comparison of matched prehemolysis and posthemolysis specimens. Of the samples, 16.9% were hemolyzed at the baseline (11 of 72 pre-excision, 11 of 55 postexcision). We successfully induced moderate hemolysis (ΔHg 0.1-1.0mg/DL) in 66 samples that had minimal hemolysis at baseline. In these, mechanical hemolysis increased free Hg by an average of 0.37mg/DL (533%; mean posthemolysis free Hg=0.43; moderate hemolysis) and lowered PTH values by an average of 39% (median=36%, SD=11%; P=.002). The decrease in PTH was related to the extent of hemolysis induced (r=0.51; P<.001), but was unrelated to the specimen's baseline (true) PTH (P=.24). In 12 of 30 patients, the experimentally hemolyzed pre-excision PTH value would have reduced the 50% threshold sufficiently to cause a false-negative result. In 6 of the 30 parathyroidectomies, a hemolyzed postexcision PTH value would have decreased PTH value sufficiently to cause a false-positive result. Hemolysis of IOPTH specimens occurs commonly and falsely reduces PTH results. In 18 of 30 patients, this effect was sufficient to have contributed to either a false-positive or false-negative IOPTH result.

Red Blood Cell Damage from Extracorporeal Circulation in Hemodialysis

Blood damage is an unavoidable side effect of extracorporeal circulation. The effects of blood damage on patients' hematocrit and erythropoietin requirement as well as other potential side effects have not been studied for uneventful treatments. Comparing long nocturnal dialysis with regular 4-hour, three times per week dialysis allows for the conclusion that the influence of blood damage caused by extracorporeal circulation is small compared with biochemical effects. Acute hemolysis is one of the few remaining mechanical problems of dialysis. Acute hemolysis is caused by obstructions within the extracorporeal circuit caused by manufacturing errors, kinking of blood tubing or user errors, or by a combination of excessive flow and improper cannula or catheter dimensions. The risk of acute hemolysis can be further reduced by industrial quality control, better design of dialysis equipment, and hemodialysis machine control. Adverse effects caused by chronic mechanical hemolysis need to be studied.

Structural state of erythrocyte membranes in a human with Alzheimer’s disease

The structural state of erythrocyte membranes collected from patients with Alzheimer’s disease (AD) was studied. The structural state was characterized by the degree of hemolysis and the content of malonic dialdehyde (MDA), as measures of the peroxide oxidation of lipids (POL), and by the microviscosity of the lipid bilayer. The microviscosity of the membranes was measured by the EPR spin probe method, with 2,2,6,6-tetramethyl-4-capryloyl-oxypiperidine-1-oxyl (lipid probe) and 5,6-benzo-2,2,6,6-tetramethyl-1,2,3,4-tetrahydro-gamma-carboline-3-oxyl (protein probe). It was established that all patients with AD feature an increased fluidity of both the lipid and near-protein areas of erythrocyte membranes. Based on the POL intensity, three groups of patients were identified. The first group was characterized by an increased POL intensity. This group featured a high degree of hemolysis and a high MDA content both before and after incubation, with increases in both these parameters being observed upon incubation. The second and third groups were characterized by a low POL intensity. The second group exhibited a low degree of hemolysis and no increment upon incubation, with the MDA/PH ratio being much higher than unity. The third group was characterized by an increased degree of mechanical hemolysis and by decreases in the degree of homolysis and the MDA content upon incubation.

Parametric Study of Blade Tip Clearance, Flow Rate, and Impeller Speed on Blood Damage in Rotary Blood Pump

Phenomenological studies on mechanical hemolysis in rotary blood pumps have provided empirical relationships that predict hemoglobin release as an exponential function of shear rate and time. However, these relations are not universally valid in all flow circumstances, particularly in small gap clearances. The experiments in this study were conducted at multiple operating points based on flow rate, impeller speed, and tip gap clearance. Fresh bovine red blood cells were resuspended in phosphate-buffered saline at about 30% hematocrit, and circulated for 30 min in a centrifugal blood pump with a variable tip gap, designed specifically for these studies. Blood damage indices were found to increase with increased impeller speed or decreased flow rate. The hemolysis index for 50-microm tip gap was found to be less than 200-microm gap, despite increased shear rate. This is explained by a cell screening effect that prevents cells from entering the smaller gap. It is suggested that these parameters should be reflected in the hemolysis model not only for the design, but for the practical use of rotary blood pumps, and that further investigation is needed to explore other possible factors contributing to hemolysis.

Hemolytic anemia in a patient with hypertrophic obstructive cardiomyopathy

A 66-year-old woman was referred for further evaluation and treatment of normocytic and normochromic anemia with hemoglobin level of 8.6 g/dL. A peripheral blood smear showed fragmented erythrocytes. The patient was then referred to the department of cardiology because of systolic murmur, ECG abnormality, and red cell fragmentation. Transthoracic echocardiography revealed hypertrophic cardiomyopathy with particularly increased interventricular septal thickness of 24 mm and a hyperkinetic wall motion, resulting in marked obstruction to left ventricular outflow tract (pressure gradient of 200 mmHg). Mitral regurgitation due to systolic anterior motion of the mitral valve leaflets was also seen. The cause of anemia was thought to be mechanical intravascular hemolysis due to left ventricular outflow tract obstruction and mitral regurgitation. She was treated with atenolol and the class Ia antiarrhythmic drug cibenzoline to relieve the outflow tract obstruction, and the pressure gradient was reduced to 70 mmHg. After 3 months of treatment, her hemoglobin level had increased to 11.4 g/dL without additional treatment for anemia.

Rethinking turbulence in blood

Blood flow, normally laminar, can exhibit high frequency fluctuations suggesting turbulence, which has important implications for the pathophysiology of vascular diseases and the design of blood-bearing devices. According to the classical model of turbulence in a homogeneous fluid, these fluctuations can be attributed to the cascade of eddies down to the Kolmogorov length scale, which, for apparent turbulence in blood, is reported to be on the order of tens of microns. On the other hand, blood is a suspension of mostly red blood cells (RBC), the size and concentration of which would seem to preclude the formation of eddies down to these scales. Assuming dissipation occurs instead via cell-cell interactions mediated by the plasma, here we show how turbulent velocity fluctuations, normally ascribed to turbulent (Reynolds) stresses, could give rise to viscous shear stresses. This may help to resolve fundamental inconsistencies in the understanding of mechanical hemolysis, and it provides a physical basis for the forces actually experienced by formed elements in the blood under nominally turbulent flow. In summary, RBC must be acknowledged as equal players if a satisfactory definition of turbulence in blood is to be achieved.

Plasma Exchange During Cardiopulmonary Bypass in Patients With Severe Hemolysis in Cardiac Surgery

Severe mechanical hemolysis after cardiac surgery is a rare occurrence but one of the most common complications leading to reoperation. The aim of this study was to assess the efficiency and safety of plasma exchange (PE) during cardiopulmonary bypass (CPB). Five patients required PE because of severe hemolysis after cardiac surgery in Fuwai Hospital from January 2002 to December 2007: two with periprosthetic leakage and infective endocarditis, one with periprosthetic leakage, one with unsatisfied right ventricular outflow tract patching, and one with thromboses during extracorporeal membrane oxygenation (ECMO). They all needed blood purification to avoid acute renal insufficiency. The amount of transfused crystalloid solution, nonprotein colloid, plasma, and blood were 1,620+/-906.6 mL, 1,960+/-939.7 mL, 2,240+/-844.4 mL, and 680+/-228.1 mL. The volume of PE was 3,800+/-1,701.5 mL, and the volume of ultrafiltrate was 2,470+/-1,327.4 mL. The concentration of free hemoglobin (FHb) before PE, after PE, and before discharge were 3,840+/-538 mg/L, 325+/-27 mg/L, and 60.4+/-27 mg/L, respectively. Five patients were successfully treated with PE during CPB without major complications. All patients recovered well. Plasma exchange during CPB for severe hemolysis is a safe technique. Acute renal failure induced by severe hemolysis can be prevented by PE.

Measurement of erythrocyte aggregation in a microchip stirring system by light transmission

In the analysis of red blood cell (RBC) aggregation using optical detection, various shearing methods have been used to disperse RBCs in confined geometries. This study investigated RBC aggregation measurement in a microchip-stirring system by analysis of light transmission. A stirring-aided disaggregation mechanism in a microchip, consisting of a flat-cylindrical test chamber (D=4 mm, H=0.3 mm) and a magnetic stirrer (d=0.14 mm, l=2.2 mm), was used to generate a given shear which was large enough to disperse RBC aggregates, but not large enough to cause any mechanical hemolysis of cells. After stirring for 10 s followed by an abrupt halt of the stirring, the intensity of the light transmitted through a microchip was measured with respect to time and analyzed. A comparative study was conducted with varying test chamber height and hematocrit. The AI and t1/2 as typical aggregation indices obtained by analysis of transmitted light, which showed a good reproducibility (coefficient of variation (CV)<2.8%, n=10), also were found to be nearly independent of the chamber dimensions (CV<3.4%). The present aggregometry also showed the similar results of aggregation indices with varying hematocrits compared to those obtained using a laser-assisted optical rotational cell analyzer (LORCA). The essential feature of the present design is the adoption of a disposable microchip requiring a minimum blood sample volume as small as 6 mul, which enables it to be used easily in a clinical setting.

Endogenous Carbon Monoxide Production: A Rare and Detrimental Complication of Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is a technique that can support gas-exchange and cardiac function in patients with acute respiratory or cardiac failure that is not responsive to conservative treatment. ECMO is a high-risk procedure in critically ill patients and both technical and patient-related complications frequently occur. We report on a patient with end-stage pulmonary fibrosis (histiocytosis x), in whom ECMO was used as bridge to urgent lung transplantation. Respiratory insufficiency necessitating ECMO therapy was due to spontaneous pneumothorax with bronchopleural fistula. Access was initially made by femoral veno-venous canulation. Due to right heart failure, access was switched to veno-arterial using the two existing canulae as efferent system and implanting a third canula on the femoral artery using a graft. Despite marked hemodynamic improvement after this intervention, high flow rates creating high premembrane pressures were required to ensure oxygenation. High levels of carboxyhemoglobin (COHb) occurred, most likely due to massive mechanical hemolysis in the ECMO circuit. This may have had detrimental effects by further complicating tissue oxygenation. We recommend that COHb should routinely be checked in ECMO patients.

Acute hemolysis with subsequent life-threatening pancreatitis in hemodialysis. A complication which is not preventable with current dialysis equipment

A retrospective study was undertaken of 14 patients (eleven men, three women; mean age 52 [33-68] years in whom haemolysis had occurred during chronic haemodialysis (n = 12) or haemofiltration (n = 2). The haemolysis was of mechanical cause in eight patients, by an osmotic mechanism in one, and of unknown cause in five. Cardinal symptoms were nausea in 14 patients, abdominal pain in nine, vomiting in eight and raised blood pressure in ten. The plasma was discoloured in all patients and there was also an increase in free haemoglobin (110-2400 mg/dl) and (or) lactate dehydrogenase (311-7403 U/l). In all of eleven patients in whom it was measured the activity of serum amylase and (or) lipase was more than doubled (to 73-2400 U/l and 473-16,740 U/l, respectively). All patients were treated symptomatically, three had a blood exchange, two others plasma separation. Eight patients recovered within a few days, but necrotizing pancreatitis developed in six, three of whom died while two had permanent sequelae. This series shows that dialysis-induced acute haemolysis can cause life-threatening pancreatitis. Narrowings within the extracorporeal circuit, not always recognized in current dialysis equipment, are the most frequent cause of the mechanical haemolysis.