F. Meisner

Can we continue research in splenectomized dogs? Mycoplasma haemocanis: old problem--new insight.

We report the appearance of a Mycoplasma haemocanis infection in laboratory dogs, which has been reported previously, yet, never before in Europe. Outbreak of the disease was triggered by a splenectomy intended to prepare the dogs for a hemorrhagic shock study. The clinical course of the dogs was dramatic including anorexia and hemolytic anemia. Treatment included allogeneic transfusion, prednisone, and oxytetracycline. Systematic follow-up (n = 12, blood smears, antibody testing and specific polymerase chain reaction) gives clear evidence that persistent eradication of M. haemocanis is unlikely. We, therefore, had to abandon the intended shock study. In the absence of effective surveillance and screening for M. haemocanis, the question arises whether it is prudent to continue shock research in splenectomized dogs.

Stent-Based Approach for Ventricle–to–Coronary Artery Bypass

Background—Ventricle-to–coronary artery bypass (VCAB) is an experimental revascularization procedure that provides predominantly systolic instead of diastolic blood flow to a coronary artery. Methods and Results—In a pig model, a stent-based procedure (VSTENT) was developed to create a VCAB. After thoracotomy, a covered VSTENT was implanted between the left ventricle and the left anterior descending coronary artery (LAD). Distal LAD flow, regional myocardial function, and intracoronary pressures were determined at different degrees of LAD stenosis and during complete LAD occlusion. During 3 hours of LAD occlusion, VSTENT preserved net forward flow at 70±6% and regional myocardial function at 71±8% of baseline. Preservation of net flow was influenced by the positioning of the VSTENT, with higher preservation also under conditions of increased oxygen demand if a “valve-like mechanism” was present during diastole. At a hemodynamically relevant level of LAD stenosis (>70%), systolic inflow was predominant after VSTENT implantation. Changes in mean diastolic intracoronary pressure that resulted from different degrees of LAD stenosis were linearly correlated to net flow after VSTENT implantation (r =0.88;P <0.001). Conclusions—VSTENT for ventricle-to–coronary artery bypass was feasible and preserved 70±6% of baseline flow during complete LAD occlusion. The degree of preservation was dependent on the position of the VSTENT creating a valve-like mechanism during diastole. Residual diastolic blood flow through a high-grade LAD stenosis influenced net flow favorably, because diastolic backflow decreased with increasing mean diastolic intracoronary pressure.

Comparison of regional blood flow values measured by radioactive and fluorescent microspheres.

Fluorescent microspheres (FM) have become an attractive alternative to radioactive microspheres (RM) for the measurement of regional blood flow (RBF). The aim of the present study was to investigate the comparability of both methods by measuring RBF with FM and RM. Eight anaesthetised pigs received simultaneous, left atrial injections of FM and RM with a diameter of 15 µm at six different time points. Blood reference samples were collected from the descending aorta. RBF was determined in tissue samples of the myocardium, spleen and kidneys of all 8 animals. After radioactivity of the tissue samples was determined, the samples were processed automatically for measuring fluorescence using a recently developed filter device (SPU). RBF was calculated with both the isotope and spectrometric data of both methods for each sample resulting in a total of 10,512 blood flow values. The comparison of the RBF values yielded high linear correlation (mean r2 = 0.95 ± 0.03 to 0.97 ± 0.02) and excellent agreement (bias 5.4–6.7%, precision 9.9– 16.5%) of both methods. Our results indicate the validity of MS and of the automated tissue processing technique by means of the SPU.

Inhaled nitric oxide induces cerebrovascular effects in anesthetized pigs

Although inhaled nitric oxide (NO(i)) is considered to act selectively on pulmonary vessels, EEG abnormalities and even occasional neurotoxic effects of NO(i) have been proposed. Here, we investigated cerebrovascular effects of increasing concentrations of 5, 10 and 50 ppm NO(i) in seven anesthetized pigs. Cerebral hemodynamics were assessed non-invasively by use of near-infared spectroscopy and indicator dilution techniques. NO(i) increased cerebral blood volume significantly and reversibly. This effect was not attributable to changes of macrohemodynamic parameters or arterial blood gases. Simultaneously, cerebral transit time increased while cerebral blood flow remained unchanged. These data demonstrate a vasodilatory action of NO(i) in the cerebral vasculature, which may occur preferentially in the venous compartment.

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

In severe hemorrhagic shock, left ventricular (LV) diastolic dysfunction is an early sign of cardiac failure due to compromised myocardial oxygenation. Immediate fluid replacement or, in particular, administration of a hemoglobin-based oxygen carrier (diaspirin cross-linked hemoglobin; DCLHb) improves myocardial oxygenation; therefore, positive effects on LV diastolic function could be expected. The effects of fluid resuscitation from severe hemorrhagic shock with DCLHb were investigated in 20 anesthetized domestic pigs. After generation of a critical left anterior descending coronary artery stenosis (narrowing of the artery until disappearance of reactive hyperemia after a 10-second complete vessel occlusion), hemorrhagic shock (mean arterial blood pressure 45 mm Hg) was induced within 15 min by controlled blood withdrawal and maintained for 60 min. Fluid resuscitation consisted of replacement of the plasma volume withdrawn during hemorrhage by infusion of either 10% DCLHb (DCLHb group, n = 10) or 8% human serum albumin (HSA) oncotically matched to DCLHb (HSA group, n = 10). After completion of resuscitation, an observation period of 60 min elapsed. Measurements of central hemodynamics, myocardial oxygenation, and LV diastolic function were performed at baseline, after induction of critical coronary artery stenosis, after 60 min of hemorrhagic shock, immediately after resuscitation, and 60 min later. While 5 out of 10 animals treated with HSA died within the first 20 min after fluid resuscitation from acute LV pump failure, all DCLHb-treated animals survived until the end of the protocol (p < 0.05). Despite superior myocardial oxygenation due to augmentation of the arterial O2 content as well as of coronary perfusion pressure, no beneficial effects on LV diastolic function were observed after infusion of DCLHb. Peak velocity of LV pressure decrease (dp/dtmin) did not reveal significant differences between the two groups. Immediately after completion of fluid resuscitation with DCLHb, the time constant of LV diastolic relaxation (τ) was prolonged when compared with HSA-treated animals (p < 0.05), indicating retardation of early LV diastolic relaxation. Our data suggest that DCLHb fails to improve LV diastolic function after fluid resuscitation from severe hemorrhagic shock. However, positive effects on myocardial perfusion and oxygenation result in a significant reduction of the mortality of severe hemorrhagic shock.

Use of procalcitonin as indicator of nonviral infections in transplantation and related immunologic diseases

Procalcitonin (PCT) is a new potential and reliable marker for detection of bacterial, fungal and protozoal infection. It allows to differentiate these from viral infection and early rejection in heart, heart-lung, lung, and liver transplant recipients. Procalcitonin is a propeptide of calcitonin with unknown origin that is not detectable in plasma of healthy individuals. It increases rapidly and significantly under severe bacterial, fungal, and protozoal infections in all transplant patients. Magnitude of value is clearly associated with the severity of infection. The release of PCT does not depend on the type of pathogens, even though Aspergillum resulted in the highest levels measured. Sensitivity, specificity, and prognostic value of PCT were remarkable. PCT provides vital information early to clinicians and allows them to improve the management of bacterial and fungal infections in immunocompromised transplant recipients. PCT facilitates and improves the outcome of survival rate and the quality of life in the postoperative period. Thus, PCT is a highly specific analyte that shows significant diagnostic validities when nonviral infections are compared with rejection episodes.