Diaspirin cross-linked hemoglobin fails to improve left ventricular diastolic function after fluid resuscitation from hemorrhagic shock

Improved short-term survival with polyethylene glycol modified hemoglobin liposomes in critical normovolemic anemia

OBJECTIVE

To investigate the efficacy of a polyethylene glycol (PEG) modified formulation of liposome-encapsulated hemoglobin (LEH) as an oxygen-carrying blood substitute in the treatment of critical normovolemic anemia.

DESIGN AND SETTING

Prospective, controlled, randomized experimental study in a university research facility.

SUBJECTS

14 anesthetized and mechanically ventilated beagle dogs.

INTERVENTIONS

Animals were splenectomized and hemodiluted by exchange of whole blood for iso-oncotic hetastarch (HES). Target parameter of the hemodilution protocol was the individual critical hemoglobin concentration (Hb(crit)) corresponding with the onset of O(2) supply dependency of total body O(2) consumption. At Hb(crit) animals were randomized to receive a bolus infusion (20[Symbol: see text]ml/kg) of either LEH (n = 7) or normal saline (NS; n = 7). Subsequently animals were observed without further intervention.

MEASUREMENTS AND RESULTS

The primary endpoint was survival time after the completion of treatment; secondary endpoints were parameters of central hemodynamics, O(2) transport and tissue oxygenation. Animals in the LEH group survived significantly longer after completion of treatment (149 +/- 109 vs. 43+/- 56 min). Immediately after treatment LEH-treated animals presented with a more stable cardiovascular condition. After 30 min tissue O(2) tension on the surface of a skeletal muscle was significantly higher in the LEH group (23+/-8 vs. 9 +/- 2 mmHg). Nevertheless, treatment with LEH did not decrease mortality within the observation period.

CONCLUSIONS

In this present experimental study the infusion of a PEG-modified LEH provided adequate tissue oxygenation, hemodynamic stability, and a prolongation of survival time after critical anemia. However, these effects were sustained for only a short period of time.

Alternatives to allogeneic blood transfusions

Inherent risks and increasing costs of allogeneic transfusions underline the socioeconomic relevance of safe and effective alternatives to banked blood. The safety limits of a restrictive transfusion policy are given by a patient's individual tolerance of acute normovolaemic anaemia. latrogenic attempts to increase tolerance of anaemia are helpful in avoiding premature blood transfusions while at the same time maintaining adequate tissue oxygenation. Autologous transfusion techniques include preoperative autologous blood donation (PAD), acute normovolaemic haemodilution (ANH), and intraoperative cell salvage (ICS). The efficacy of PAD and ANH can be augmented by supplemental iron and/or erythropoietin. PAD is only cost-effective when based on a meticulous donation/transfusion plan calculated for the individual patient, and still carries the risk of mistransfusion (clerical error). In contrast, ANH has almost no risks and is more cost-effective. A significant reduction in allogeneic blood transfusions can also be achieved by ICS. Currently, some controversy regarding contraindications of ICS needs to be resolved. Artificial oxygen carriers based on perfluorocarbon (PFC) or haemoglobin (haemoglobin-based oxygen carriers, HBOCs) are attractive alternatives to allogeneic red blood cells. Nevertheless, to date no artificial oxygen carrier is available for routine clinical use, and further studies are needed to show the safety and efficacy of these substances.

Fluid resuscitation from severe hemorrhagic shock using diaspirin cross-linked hemoglobin fails to improve pancreatic and renal perfusion

BACKGROUND

Fluid resuscitation from hemorrhagic shock is intended to abolish microcirculatory disorders and to restore adequate tissue oxygenation. Diaspirin cross-linked hemoglobin (DCLHb) is a hemoglobin-based oxygen carrier (HBOC) with vasoconstrictive properties. Therefore, fluid resuscitation from severe hemorrhagic shock using DCLHb was expected to improve perfusion pressure and tissue perfusion of kidneys and pancreas.

METHODS

In 20 anesthetized domestic pigs with an experimentally induced coronary stenosis, shock (mean arterial pressure 45 mmHg) was induced by controlled withdrawal of blood and maintained for 60 min. Fluid resuscitation (replacement of the plasma volume withdrawn during hemorrhage) was performed with either 10% DCLHb (DCLHb group, n = 10) or 8% human serum albumin (HSA) oncotically matched to DCLHb (HSA group, n = 10). Completion of resuscitation was followed by a 60-min observation period. Regional blood flow to the kidneys and the pancreas was measured by use of the radioactive microspheres method at baseline, after shock and 60 min after fluid resuscitation.

RESULTS

All animals (10/10) resuscitated with DCLHb survived the 60-min observation period, while 5/10 control animals died within 20 min due to persisting subendocardial ischemia. In contrast to HSA survivors, pancreas and kidneys of DCLHb-treated animals revealed lower total and regional organ perfusion and regional oxygen delivery. Renal and pancreatic blood flow heterogeneity was higher in the DCLHb group.

CONCLUSION

DCLHb-induced vasoconstriction afforded superior myocardial perfusion, but impaired regional perfusion of the kidneys and the pancreas.

The use of a hemoglobin-based oxygen-carrying solution (HBOC-201) for extracorporeal membrane oxygenation in a porcine model with acute respiratory distress syndrome

OBJECTIVE

To evaluate whether hemoglobin-based oxygen-carrying solution (HBOC)-201 (Biopure) is an effective alternative to donor blood for extracorporeal membrane oxygenation support in a porcine model of acute respiratory distress syndrome (ARDS).

DESIGN

Randomized animal clinical trial.

SETTING

Animal surgical research laboratory.

SUBJECTS

Immature Yorkshire swine were assigned to one of three groups: 1, noninjured animals, donor porcine blood primed circuit; 2, ARDS-injured, HBOC-201 primed circuit; or 3, ARDS-injured, donor blood primed.

INTERVENTIONS

ARDS injury was induced in groups 2 and 3 with oleic acid infusion before bypass. All animals were placed on full venoarterial extracorporeal membrane oxygenation support for 8 hrs.

MEASUREMENTS AND MAIN RESULTS

Physiologic variables and laboratory samples were measured at baseline and hourly for 8 hrs. Data analysis consisted of repeated-measures analysis of variance with post hoc analysis. We found that 100% of animals survived on extracorporeal membrane oxygenation for the duration of the study period. HBOC-supported animals had comparable oxygen delivery to both donor blood groups. Mean pulmonary artery pressure, heart rate, and lactate concentrations were higher in the injury groups. Blood pressure was mildly increased in HBOC animals (p <.05 vs. control animals). Methemoglobin concentrations in the HBOC group were elevated and increased over time on extracorporeal membrane oxygenation (p <.001).

CONCLUSIONS

HBOC-201 appears to be an effective alternative circuit-priming agent for use during extracorporeal membrane oxygenation. HBOC offers the advantages of rapid availability and diminished donor blood cell exposure. The efficacy of HBOC in longer duration bypass, and its associated methemoglobinemia, need to be further investigated.

Myocardial strain rate is a superior method for evaluation of left ventricular subendocardial function compared with tissue Doppler imaging

OBJECTIVES

This study was performed to evaluate subendocardial function using strain rate imaging (SRI).

BACKGROUND

The subendocardium and mid-wall of the left ventricle (LV) play important roles in ventricular function. Previous methods used for evaluating this function are either invasive or cumbersome. Strain rate imaging by ultrasound is a newly developed echocardiographic modality based on tissue Doppler imaging (TDI) that allows quantitative assessment of regional myocardial wall motion.

METHODS

We examined eight sheep using TDI in apical four-chamber views to evaluate the LV free wall. Peak strain rates (SRs) during isovolumic relaxation (IR), isovolumic contraction (IC), and myocardial strain were measured in the endocardial (End), mid-myocardial (Mid), and epicardial (Epi) layers. For four hemodynamic conditions (created after baseline by blood, dobutamine, and metoprolol infusion), we compared differences in SR of End, Mid, and Epi layers to peak positive and negative first derivative of LV pressure (dP/dt).

RESULTS

Strain rate during IC showed a good correlation with +dP/dt (r = 0.74, p < 0.001) and during IR with -dP/dt (r = 0.67, p = 0.0003). There was a significant difference in SR between the myocardial layers during both IC and IR (End: -3.4 +/- 2.2 s(-1), Mid: -1.8 +/- 1.5 s(-1), Epi: -0.63 +/- 1.0 s(-1), p < 0.0001 during IC; End: 2.2 +/- 1.5 s(-1), Mid: 1.0 +/- 0.8 s(-1), Epi: 0.47 +/- 0.64 s(-1), p < 0.0001 during IR). Also, SRs of the End and Mid layers during IC were significantly altered by different hemodynamic conditions (End at baseline: 1.7 +/- 0.7 s(-1); blood: 2.0 +/- 1.1 s(-1); dobutamine: 3.4 +/- 2.3 s(-1); metoprolol: 1.0 +/- 0.4 s(-1); p < 0.05). Myocardial strain showed differences in each layer (End: -34.3 +/- 12.6%; Mid: -22.6 +/- 12.1%; Epi: -11.4 +/- 7.9%; p < 0.0001) and changed significantly in different hemodynamic conditions (p < 0.0001).

CONCLUSIONS

Strain and SR appear useful and sensitive for evaluating myocardial function, especially for the subendocardial region.