Biomedical subjects

G Kemming

Publications and source records attributed to G Kemming.

26 records · Page 2Linked to original sources

PubMed1997

Myocardial blood flow heterogeneity in shock and small-volume resuscitation in pigs with coronary stenosis.

Myocardial blood flow heterogeneity in shock and small-volume resuscitation in pigs with coronary stenosis. J. Appl. Physiol. 83(6): 1832-1841, 1997.-We analyzed the effects of shock and small-volume resuscitation in the presence of coronary stenosis on fractal dimension (D) and spatial correlation (SC) of regional myocardial perfusion. Hemorrhagic shock was induced and maintained for 1 h. Pigs were resuscitated with hypertonic saline-dextran 60 [HSDex, 10% of shed blood volume (SBV)] or normal saline (NS; 80% of SBV). Therapy was continued after 30 min with dextran (10% SBV). At baseline, D was 1.39 +/- 0.06 (mean +/- SE; HSDex group) and 1.34 +/- 0.04 (NS group). SC was 0.26 +/- 0.07 (HSDex) and 0.26 +/- 0.04 (NS). Left anterior descending coronary artery stenosis changed neither D nor SC. Shock significantly reduced D (i.e., homogenized perfusion): 1.26 +/- 0.06 (HSDex) and 1.23 +/- 0.05 (NS). SC was increased: 0.41 +/- 0.1 (HSDex) and 0.48 +/- 0.07 (NS). Fluid therapy with HSDex further decreased D to 1.22 +/- 0.05, whereas NS did not change D. SC was increased by both HSDex (0.56 +/- 0.1) and NS (0.53 +/- 0.06). At 1 h after resuscitation, SC was constant in both groups, and D was reduced only in the NS group (1.18 +/- 0.02). We conclude that hemorrhagic shock homogenized regional myocardial perfusion in coronary stenosis and that fluid therapy failed to restore this.

Acid-Base Equilibrium↗

PubMed1996

Effects of hemodilution on gastric regional perfusion and intramucosal pH.

UNLABELLED: Acute normovolemic hemodilution (ANH) has been shown to be a cost-effective method of reducing allogenic blood transfusion during elective surgery. ANH has been implicated with impaired oxygenation in isolated canine gastric flaps. The present study was designed to investigate the effects of ANH on gastric mucosal oxygenation using a model closely imitating the clinical situation. Sixteen splenectomized anesthetized beagles were isovolemically hemodiluted to a hematocrit of 20 +/- 1% (6% hydroxyethyl starch; mol wt 200,000; substitution ratio 0.45-0.55). Blood volume (indocyanine green), cardiorespiratory parameters, gastric intramucosal pH (pHi), and gastric regional blood flow (radioactive microspheres; 15 microns) were measured before and after ANH. RESULTS: blood volume was unchanged (87 +/- 8 ml/kg before and 88 +/- 7 ml/kg after ANH). Median total gastric mucosal blood flow at baseline was 0.51 +/- 0.35 ml.min-1.g-1 and did not change significantly upon ANH. The mean pHi was 7.29 +/- 0.05 before and 7.28 +/- 0.05 after hemodilution. There was a homogenization of blood flow distribution in gastric mucosa. Severe hemodilution to a hematocrit of 20% does not impair gastric mucosal oxygenation and poses no risk to gastric mucosal integrity.

Animals↗

PubMed1996

Inhaled prostacyclin (PGI2) versus inhaled nitric oxide in adult respiratory distress syndrome.

Inhalation of nitric oxide (NO) and prostacyclin (PGI2) may induce selective pulmonary vasodilation and-by improving ventilation-perfusion ratio in ventilated areas of the lung-increase Pao2 in patients with acute lung injury. To assess the therapeutic efficacy of both compounds, dose-response curves were established in patients with adult respiratory distress syndrome (ARDS). Patients received both PGI2 (doses of 1, 10, and 25 ng/kg/min) and NO (concentrations of 1, 4, and 8 ppm). Cardiorespiratory parameters were assessed at control, at each drug concentration, and after withdrawal of NO and PGI2. PGI2 resulted in a significant, dose-dependent and selective reduction of pulmonary artery pressure (PAP) from 35.1 +/- 6.3 mm Hg at control to 33.1 +/- 4.8 (1 ng/kg/min), 31.3 +/- 4.8 mm Hg (10 ng/kg/min) and 29.6 +/- 4.5 mm Hg (25 ng/kg/min), respectively. Inhaled NO reduced PAP from 34.5 +/- 5.6 to 32.1 +/- 5.9 mm Hg at 4 ppm, and to 31.8 +/- 6.1 mm Hg at 8 ppm, respectively, with no effect at 1 ppm. Pao2/Flo2 ratio increased from 105 +/- 37 to 125 +/- 56 mm Hg (range of increase: 0 to 57 mm Hg) at PGI2 10 ng/kg/min and to 131 +/- 63 mm Hg (range: -5 to 89 mm Hg) at 25 ng/kg/min with no effect at 1 ng/kg/min. NO improved Pao2 (e.g., from 116 +/- 47 to 167 +/- 86 mm Hg at 8 ppm) and reduced intrapulmonary shunt at all doses tested. We conclude that both inhaled PGI2 and NO may induce selective pulmonary vasodilation and increase Pao2 in severe ARDS.

APACHE↗

PubMedDate not supplied

Hyperoxia in extreme hemodilution.

Intraoperative surgical blood loss is initially replaced by infusion of red cell-free, cristalloidal or colloidal solutions. When normovolemia is maintained the ensuing dilutional anemia is compensated by an increase of cardiac output and of arterial oxygen extraction. In the ideal case, a surgical blood loss can entirely be 'bridged' without transfusion by intraoperative normovolemic hemodilution. However major blood loss results in extreme hemodilution and the transfusion of red blood cells may finally become necessary to increase arterial oxygen content and to preserve tissue oxygenation. When transfusion has to be started before surgical control of bleeding has been achieved, parts of the red blood cells transfused will get lost, thereby increasing intraoperative transfusion needs. Beside red blood cell transfusion, arterial oxygen content can be rapidly increased by ventilating the patient with 100% oxygen (hyperoxic ventilation), thus enhancing the amount of physically dissolved oxygen in plasma (hyperoxia). In experimental and clinical studies hyperoxic ventilation has emerged as a simple, safe and effective intervention to enlarge the margin of safety for hemodynamic compensation and tissue oxygenation in hemodiluted subjects experiencing major bleeding. The hyperoxia-associated microcirculatory dysregulation and impaired tissue oxygenation known to take place in the presence of a physiologic hemoglobin concentration are not encountered in hemodiluted subjects. Hyperoxic hemodilution i.e. the combination of intraoperative extreme hemodilution and hyperoxic ventilation may therefore be considered a cost-effective, safe and efficient supplement to reduce allogeneic transfusion during surgical interventions associated with high blood losses. The vast majority of the experimental and clinical investigations this new concept is based on was initiated and performed under the guidance of Prof. Konrad Messmer.

Blood Loss, Surgical↗

PubMedDate not supplied

Searching the ideal inhaled vasodilator: from nitric oxide to prostacyclin.

Today, the technique to directly administer vasodilators via the airway to treat pulmonary hypertension and to improve pulmonary gas exchange is widely accepted among clinicians. The flood of scientific work focussing on this new therapeutic concept had been initiated by a fundamental new observation by Pepke-Zaba [1]and Frostell in 1991 [2]: Both scientists reported, that inhalation of exogenous nitric oxide (NO) gas selectively dilates pulmonary vessels without a concomittant systemic vasodilation. No more than another decade ago NO was identified as an important endogenous vasodilator [3]while having merely been regarded an environmental pollutant before that time. Although inhaled NO proved to be efficacious, alternatives were sought-after due to NO's potential side-effects. In search for the ideal inhaled vasodilator another group of endogenous mediators -- the prostanoids -- came into the focus of interest. The evidence for safety and efficacy of inhaled prostanoids is -- among a lot of other valuable work -- based on a series of experimental and clinical investigations that have been performed or designed at the Institute for Surgical Research under the guidance and mentorship of Prof. Dr. med. Dr. h.c. mult. K. Messmer [4-19]. In the following, the current and newly emerging clinical applications of inhaled prostanoids and the experimental data which they are based on, will be reviewed.

Administration, Inhalation↗

PubMedDate not supplied

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 O(2) 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/dt(min)) did not reveal significant differences between the two groups. Immediately after completion of fluid resuscitation with DCLHb, the time constant of LV diastolic relaxation (tau) 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.

Animals↗

PubMedDate not supplied

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.

Animals↗

PubMedDate not supplied

Improved ventricular function during inhalation of PGI(2) aerosol partly relies on enhanced myocardial contractility.

Inhaled prostacyclin (PGI(2)) aerosol induces selective pulmonary vasodilation. Further, it improves right ventricular (RV) function, which may largely rely on pulmonary vasodilation, but also on enhanced myocardial contractility. We investigated the effects of the inhaled PGI(2) analogs epoprostenol (EPO) and iloprost (ILO) on RV function and myocardial contractility in 9 anesthetized pigs receiving aerosolized EPO (25 and 50 ng.kg(-1).min(-1)) and, consecutively, ILO (60 ng.kg(-1).min(-1)) for 20 min each. We measured pulmonary artery pressure (PAP), RV ejection fraction (RVEF) and RV end-diastolic-volume (RV-EDV), and left ventricular end-systolic pressure-volume-relation (end-systolic elastance, E(es)). EPO and ILO reduced PAP, increased RVEF and reduced RVEDV. E(es) was enhanced during all doses tested, which reached statistical significance during EPO(25 ng) and ILO, but not during EPO(50 ng). PGI(2) aerosol enhances myocardial contractility in healthy pigs, contributing to improve RV function.

Administration, Inhalation↗