Replacing the Transfusion of 1-2 Units of Blood with Plasma Expanders that Increase Oxygen Delivery Capacity: Evidence from Experimental Studies

Mismatch between Tissue Partial Oxygen Pressure and Near-Infrared Spectroscopy Neuromonitoring of Tissue Respiration in Acute Brain Trauma: The Rationale for Implementing a Multimodal Monitoring Strategy

The brain tissue partial oxygen pressure (PbtO₂) and near-infrared spectroscopy (NIRS) neuromonitoring are frequently compared in the management of acute moderate and severe traumatic brain injury patients; however, the relationship between their respective output parameters flows from the complex pathogenesis of tissue respiration after brain trauma. NIRS neuromonitoring overcomes certain limitations related to the heterogeneity of the pathology across the brain that cannot be adequately addressed by local-sample invasive neuromonitoring (e.g., PbtO₂ neuromonitoring, microdialysis), and it allows clinicians to assess parameters that cannot otherwise be scanned. The anatomical co-registration of an NIRS signal with axial imaging (e.g., computerized tomography scan) enhances the optical signal, which can be changed by the anatomy of the lesions and the significance of the radiological assessment. These arguments led us to conclude that rather than aiming to substitute PbtO₂ with tissue saturation, multiple types of NIRS should be included via multimodal systemic- and neuro-monitoring, whose values then are incorporated into biosignatures linked to patient status and prognosis. Discussion on the abnormalities in tissue respiration due to brain trauma and how they affect the PbtO₂ and NIRS neuromonitoring is given.

Extended photoacoustic transport model for characterization of red blood cell morphology in microchannel flow

The dynamic response behavior of red blood cells holds the key to understanding red blood cell related diseases. In this regard, an understanding of the physiological functions of erythrocytes is significant before focusing on red blood cell aggregation in the microcirculatory system. In this work, we present a theoretical model for a photoacoustic signal that occurs when deformed red blood cells pass through a microfluidic channel. Using a Green's function approach, the photoacoustic pressure wave is obtained analytically by solving a combined Navier-Stokes and photoacoustic equation system. The photoacoustic wave expression includes determinant parameters for the cell deformability such as plasma viscosity, density, and red blood cell aggregation, as well as involving laser parameters such as beamwidth, pulse duration, and repetition rate. The effects of aggregation on blood rheology are also investigated. The results presented by this study show good agreements with the experimental ones in the literature. The comprehensive analytical solution of the extended photoacoustic transport model including a modified Morse type potential function sheds light on the dynamics of aggregate formation and demonstrates that the profile of a photoacoustic pressure wave has the potential for detecting and characterizing red blood cell aggregation.

Experimental Study on the Efficacy of Site-Specific PEGylated Human Serum Albumins in Resuscitation From Hemorrhagic Shock

OBJECTIVES

To evaluate the resuscitative efficacy and the effect on reperfusion injury of two site-specific PEGylated human serum albumins modified with linear or branched PEG20kDa, compared with saline, 8% human serum albumin and 25% human serum albumin, in a hemorrhagic shock model.

SETTING

Laboratory.

SUBJECTS

Male Wistar rats.

DESIGN

Prospective study.

INTERVENTIONS

Rats were bled to hemorrhagic hypovolemic shock and resuscitated with different resuscitation fluids.

MEASUREMENTS AND MAIN RESULTS

The mean arterial pressure and blood gas variables were measured. Hemorheology analysis was performed to evaluate the influence of resuscitation on RBCs and blood viscosity. The microvascular state was indirectly characterized in terms of monocyte chemotactic protein-1 and endothelial nitric oxide synthase that related to shear stress and vasodilation, respectively. The levels of inflammation-related factors and apoptosis-related proteins were used to evaluate the reperfusion injury in lungs. The results showed that PEGylated human serum albumin could improve the level of mean arterial pressure and blood gas variables more effectively at the end of resuscitation. poly(ethylene glycol) modification was able to increase the viscosity of human serum albumin to the level of effectively enhancing the expression of monocyte chemotactic protein-1 and endothelial nitric oxide synthase, which could promote microvascular perfusion. The hyperosmotic resuscitative agents including both 25% human serum albumin and PEGylated human serum albumins could greatly attenuate lung injury. No significant therapeutic advantages but some disadvantages were found for Y shaped poly(ethylene glycol) modification over linear poly(ethylene glycol) modification, such as causing the decrease of erythrocyte deformability.

CONCLUSIONS

Linear high molecular weight site-specific PEGylated human serum albumin is recommended to be used as a hyperosmotic resuscitative agent.

Past, present and forecast of transfusion medicine: What has changed and what is expected to change?

Blood transfusion is the second most used medical procedures in health care systems worldwide. Over the last few decades, significant changes have been evolved in transfusion medicine practices. These changes were mainly needed to increase safety, efficacy, and availability of blood products as well as reduce recipients' unnecessary exposure to allogeneic blood. Blood products collection, processing, and storage as well as transfusion practices throughout all patient populations were the main stream of these changes. Health care systems across the world have adopted some or most of these changes to reduce transfusion risks, to improve overall patients' outcome, and to reduce health care costs. In this article, we are going to present and discuss some of these recent modifications and their impact on patients' safety.