Karl-Peter Ittner

Downregulation of Angiotensin II Type 1 Receptors During Sepsis

Our study aimed to characterize the mechanisms underlying the attenuated cardiovascular responsiveness toward the renin-angiotensin system during sepsis. For this purpose, we determined the effects of experimental Gram-negative and Gram-positive sepsis in rats. We found that sepsis led to a ubiquitous upregulation of NO synthase isoform II expression and to pronounced hypotension. Despite increased plasma renin activity and plasma angiotensin (Ang) II levels, plasma aldosterone concentrations were normal, and the blood pressure response to exogenous Ang II was markedly diminished in septic rats. Mimicking the fall of blood pressure during sepsis by short-term infusion of the NO donor sodium nitroprusside in normal rats did not alter their blood pressure response to exogenous Ang II. Therefore, we considered the possibility of an altered expression of Ang II receptors during sepsis. It turned out that Ang II type 1 receptor expression was markedly downregulated in all organs of septic rats. Further in vitro studies with rat renal mesangial cells showed that NO and a combination of proinflammatory cytokines (interleukin-1&bgr;, tumor necrosis factor-&agr;, and interferon-&ggr;) downregulated Ang II type 1 receptor expression in a synergistic fashion. In summary, our data suggest that sepsis causes a systemic downregulation of Ang II type 1 receptors that is likely mediated by proinflammatory cytokines and NO. We suggest that this downregulation of Ang II type 1 receptors is the main reason for the attenuated responsiveness of blood pressure and of aldosterone formation to Ang II and, therefore, contributes to the characteristic septic shock.

Nitric oxide synthase isoform III gene expression in rat liver is up‐regulated by lipopolysaccharide and lipoteichoic acid

This study was done to investigate the influence of Gram‐negative and Gram‐positive sepsis on the expression of the three isoforms of nitric oxide synthase (NOS) gene in rat liver and kidney. Male Sprague‐Dawley rats were treated with lipopolysaccharide (LPS, 10 mg/kg i.v.) as an in vivo model for Gram‐negative sepsis or lipoteichoic acid (LTA, 10 mg/kg i.v.) as an in vivo model for Gram‐positive sepsis. Animals were killed 12 h and 24 h after i.v. treatment. NOS mRNA of the three isoforms was determined by RNase protection assay. NOS II gene expression was strongly induced after LPS or LTA treatment in rat liver and kidney, indicating the efficacy of this treatment to induce sepsis. We found no change of NOS I gene expression after LPS or LTA injection in rat liver and kidney. NOS III gene expression was increased about 8‐fold 12 h and about 5‐fold 24 h after induction of sepsis in the rat liver whereas in the kidney there was no significant increase in NOS III gene expression. After correction for length NOS III mRNA was about 4‐ and 40‐fold more abundant 12 h and 24 h after LPS treatment than NOS II mRNA in the liver, respectively. Twelve and 24 h after LTA treatment NOS III mRNA was about 18‐ and 140‐fold more abundant than NOS II in the liver. These findings suggest that NOS III is an even more potent source of NO than NOS II in the liver after stimulation with LPS or LTA.

Elimination of methohexitone after long-term, high-dose infusion in patients with critically elevated intracranial pressure.

OBJECTIVEnTo determine the plasma elimination of methohexitone in patients with critically elevated intracranial pressure (ICP) who received the drug in high doses for several days.nnnDESIGNnDrug-monitoring study.nnnSETTINGnIntensive care unit at a university hospital.nnnPATIENTSnTwelve intensive care unit patients with brain injuries who received methohexitone as a final therapeutic approach after routine therapy had proved to be insufficient in controlling critically elevated ICP.nnnMEASUREMENTS AND MAIN RESULTSnPlasma samples were taken during methohexitone infusion, before cessation, and in distinct, short increments after discontinuation of the infusion. Methohexitone was determined in plasma by reverse-phase high-pressure liquid chromatography and photometric detection. The median duration of infusion of methohexitone was 137 hrs (minimum, 27 hrs; maximum, 445 hrs), with a median infusion rate of 62.5 microg/kg/min (minimum, 22.5 microg/kg/min; maximum, 116.2 microg/kg/min). Plasma concentrations of methohexitone at burst suppression under concomitant analgesic sedation ranged from 1.6 to 17.3 microg/mL (median, 4.7 microg/mL). After cessation of methohexitone infusion, the decline of plasma concentrations followed a biexponential function. Clearance rates, volume of distribution at steady state, context-sensitive half-time, and initial and terminal elimination half-times were calculated. Pharmacokinetic data showed remarkable interindividual variability that could not be correlated to the infusion rate, to the duration of the infusion, or to obvious differences in physiology or the disease states of these patients. Even in patients with high plasma concentrations who received the drug for a considerable length of time, the initial decline in plasma concentration was exponential, indicating redistribution.nnnCONCLUSIONSnWe conclude that the elimination kinetics of methohexitone after long-term, high-dose infusion in critically ill patients with brain injuries may favor the use of methohexitone over thiopentone for controlling critically elevated ICP by allowing for a more timely neurologic examination after cessation.

The effects of midazolam on intraocular pressure in children during examination under sedation

Background To obtain reliable and accurate measurements of the intraocular pressure (IOP) in children often requires sedation or anaesthesia. Therefore, we investigated the effects of oral midazolam on IOP in children. Methods In a prospective study, IOP was measured in 72 eyes of 36 cooperative children without glaucoma requiring general anaesthesia (mean age 3.5±1.3u2005years, body weight ≤20u2005kg) by using a Perkins hand-held tonometer. Measurements of IOP were performed before, and 15 and 30u2005min after sedation with orally administered midazolam (1u2005mg/kg) given as preoperative medication, and 5 and 15u2005min after induction of general anaesthesia. The individual IOP courses were analysed. Results In all of the cooperative children, IOP measurement was possible after sedation with midazolam. Mean IOP was 11.2±0.3u2005mmHg before sedation, 10.9±0.2u2005mmHg at 15u2005min, and 10.7±0.3u2005mmHg 30u2005min after administration of midazolam. This small decrease was not statistically significant, whilst the IOP decline at 5 and 15u2005min after induction of general anaesthesia was statistically significant (p<0.0001). Conclusion Sedation with midazolam can be assumed to be an applicable, well-tolerated, safe method for IOP measurements in children.

The effect of urapidil and ramipril on hyperglycemia in streptozotocin diabetic rats.

Abstract. Angiotensin-converting enzyme inhibitors and α1-adrenoceptor antagonists improve glucose disposal in diabetes mellitus. We compared the effect of the antihypertensive hybrid drug urapidil [α1-adrenoceptor antagonist serotonin 1A (5-hydroxytryptamine 1A, 5-HT1A) receptor agonist] on hyperglycemia in streptozotocin diabetic rats with the angiotensin-converting enzyme inhibitor ramipril. 5-HT1A receptor agonists induce hyperglycemia. This could be an important disadvantage during treatment of diabetes mellitus with urapidil. Diabetes was induced by streptozotocin (70xa0mg/kg i.p.). Treatment for 7xa0days (ramipril 10xa0mg/kg p.o.; urapidil 20xa0mg/kg p.o.) significantly decreased mean blood glucose values (urapidil: 15.7±0.9xa0mmol/l, P=0.007; ramipril: 15.0±0.8xa0mmol/l, P=0.038 vs. diabetic control group: 18.7±1.0xa0mmol/l). Both drugs reduced significantly blood pressure, urinary glucose, water consumption, and food requirement. Serotonin concentration in the brain (medulla oblongata, pituitary) was not affected. A normalization comparable with healthy control rats was observed only in a diabetic control group with insulin therapy. In conclusion, our results demonstrate that the antihypertensive drug urapidil has no detrimental effect on hyperglycemia compared with the angiotensin-converting enzyme inhibitor ramipril in experimental diabetes mellitus despite its 5-HT1A receptor agonistic properties.

Bosentan reduces oxidative burst in acid aspiration-induced lung injury in rats

BACKGROUNDnAcid aspiration induces lung injury by causing an intense inflammatory reaction. Neutrophils are attracted by various cytokines, such as TNFbeta, and release reactive oxygen species, which then cause acute lung injury. Endothelin antagonists, such as bosentan, have been found to possess anti-inflammatory properties.nnnMATERIALS AND METHODSnWe performed a prospective, randomised, controlled study to evaluate the effects of bosentan in a rat model of acid-induced lung injury. Sprague-Dawley rats underwent sevoflurane anaesthesia; lung injury was then induced by instillation of 1.2mL/kg, 0.1M hydrochloric acid. The lungs were ventilated for 6h and then randomised into three groups: bosentan 30mg/kg body weight, 90mg/kg body weight or sodium chloride, each applied immediately after acid aspiration via a gastric tube.nnnRESULTSnAfter induction of acute lung inflammation, the production of reactive oxygen species by PMN following stimulation with FMLP increased significantly. Comparison of pre-treatment and post-treatment in the 90mg/kg bosentan treatment group did not show a significant increase of reactive oxygen species following stimulation with FMLP. A comparison of the absolute difference of the MESF demonstrated a significant difference between the control group and the group treated with 90mg/kg bosentan.nnnCONCLUSIONSnBosentan administration at 90mg/kg body weight reduced the release of reactive oxygen species after 360min in acid aspiration-induced lung injury in rats.

Effect of three different doses of urapidil on blood glucose concentrations in the streptozotocin diabetic rat.

BACKGROUND AND OBJECTIVEnDiabetes mellitus associated with hypertension often causes perioperative complications. The alpha1-adrenoceptor antagonist/5-hydroxytryptamine-1A receptor agonist urapidil is an approved drug used in hypertension and hypertensive emergencies. 5-Hydroxytryptamine-1A (5-HT1A) receptor agonists impair glucose metabolism. To evaluate a possible dose-dependent hyperglycaemic effect of urapidil due to its 5-HT1A receptor agonistic properties, the effect of three doses of urapidil on hyperglycaemia in the streptozotocin diabetic rat was investigated.nnnMETHODSnMale Wistar-Kyoto rats were made diabetic by streptozotocin and randomly allocated to the following daily treatments for 7 days (n = 6 each): urapidil 6 mg kg(-1), urapidil 20 mg kg(-1), urapidil 60 mg kg(-1), insulin 4 IU kg(-1) subcutaneously. One diabetic group and one non-diabetic healthy group served as controls.nnnRESULTSnTreatment for 7 days with urapidil 20 mg kg(-1) and urapidil 60 mg kg(-1) reduced mean glucose concentrations significantly (urapidil-20: 15.6 +/- 1.1 mmol L(-1), P = 0.023; urapidil-60: 15.8 +/- 0.8 mmol L(-1), P = 0.04) compared with diabetic controls (20.9 +/- 0.8 mmol L(-1)), whereas those after urapidil 6 mg kg(-1) were similar to diabetic controls. Insulin treatment normalized blood glucose concentrations.nnnCONCLUSIONSnThe alpha1-adrenoceptor antagonist/5-HT1A receptor agonist urapidil has no hyperglycaemic effect on experimental diabetes mellitus, even in high doses, despite its 5-HT1A receptor agonistic properties.

Filter Adsorption of Anidulafungin to a Polysulfone‐Based Hemofilter During CVVHD In Vitro

Candidemia is frequent in critically ill patients, especially in combination with an acute kidney injury (AKI). Echinocandins generally are recommended for therapy of such infections. Recent studies found no need for dosage adjustment in patients with end-stage renal disease receiving hemodialysis, or patients with AKI receiving continuous venovenous hemofiltration. The aim of this in vitro study was to examine the adsorption of anidulafungin to the surface of the hemofilter during continuous venovenous hemodialysis (CVVHD) and its effect on anidulafungin concentrations. The concentration of anidulafungin in the dialyzed fluid, and the dialysate during CVVHD in vitro was examined using three different dialyzed fluids (saline; saline with 40 g/L human albumin; and a mixture of human erythrocytes and fresh frozen plasma). After the end of dialysis, the hemofilter was opened and portions of the filter capillaries were also analyzed to determine the amount of anidulafungin adsorbed. When dialyzing saline, about 99% of the anidulafungin used adsorbed to the hemofilter capillaries; in the experiments with saline with 40 g/L albumin, about 60% adsorbed to the hemofilters surface, and when blood was dialyzed, 35% was found adsorbed after analyzing the filter capillaries. Anidulafungin was not detectable in the dialysate of any of the experiments, consequently the dialysis clearance was 0 mL/min. In conclusion, during CVVHD in vitro we found remarkable adsorption of anidulafungin to the hemofilters surface, yet the effect on the tissue concentration needs further examination.