Uta-Carolin Pietsch

A new vagal anchor electrode for real-time monitoring of the recurrent laryngeal nerve

BACKGROUND Despite conventional neuromonitoring, the recurrent laryngeal nerve (RLN) is still at risk for damage during thyroid surgery. The feasibility of continuous RLN monitoring by vagal nerve (VN) stimulation with a new anchor electrode should be shown, and electromyographic signal alterations of stressed RLN were analyzed to be alerted to imminent nerve failure whereby the nerve damage becomes reversible. METHODS VN stimulation was achieved in 23 pigs. Sensed signals were analyzed and stored as real-time audio/video feedback EMG system. RLN was stressed by mechanical and thermal injury; signal alterations were evaluated. RESULTS VNs were successfully real-time stimulated by using the anchor electrode. No complications or side effects during stimulation were detected. RLN injury led to an alteration of signal amplitude and latency period but signal restitution after injury. CONCLUSIONS Real-time monitoring of the RLN is technically feasible to perceive imminent nerve failure. The anchor electrode was safely and easy to handle. Its implementation is being tested in an ongoing clinical trial.

Endothelin a receptor blockade reduces hepatic ischemia/reperfusion injury after warm ischemia in a pig model

It is well established that endothelin-1 (ET-1) is a very potent mediator of vasoconstriction that leads to microcirculatory disturbances. The aim of the study was to evaluate the effect of a selective endothelin A receptor antagonist on severe ischemia/reperfusion injury in a pig model. Fourteen pigs were subjected to 120 minutes of complete vascular exclusion of the liver with a passive bypass. The animals were randomized into two groups: a control group, which was given isotonic saline solution, and a therapy group, which received the selective endothelin A receptor antagonist BSF 208075 at the beginning of reperfusion. On postoperative days 4 and 7, animals were relaparotomized to obtain tissue specimens. Blood monitoring included aspartate aminotransferase (AST), alanine aminotransferase (ALT), glutamate dehydrogenase (GLDH), alkaline phosphatase, and ET-1. Partial oxygen tension (ptiO2) was measured by a Clarke-type electrode and blood flow by laser Doppler. A semiquantitative scoring index was used for assessment of histologic injury and for immunohistochemical analysis of ET-1. Treatment with the endothelin A receptor antagonist significantly reduced the severity of the ischemia/reperfusion injury, as evidenced by lower levels of AST, ALT, and GLDH. The dramatic increase in plasma ET-1 in the therapy group is clear evidence of effective receptor blockade. Analysis of PtiO2 and blood flow revealed a significant improvement in capillary perfusion and blood flow in the treated group and was associated with relevant reduction of tissue injury. In summary, in the control group we observed serious microcirculatory disturbances and severe histologic damage in the liver after reperfusion. Treatment with a selective endothelin A receptor antagonist attenuated the ischemia/reperfusion injury in a porcine model of severe ischemia/reperfusion, as demonstrated by improved microcirculation, a reduction in histologic damage, and an decrease in liver enzymes.

Blood lactate and pyruvate levels in the perioperative period of liver resection with pringle maneuver

INTRODUCTION Bleeding during liver surgery is often routinely controlled by the Pringle maneuver consisting in the temporary clamping of hepatic artery, portal vein, and bile duct. This study aimed at investigating a possible influence of the Pringle maneuver on tissue hypoxia during liver resection. METHODS Twenty-five consecutive patients undergoing elective liver resection were prospectively randomized either to be treated with the Pringle maneuver (Pringle group, n = 14) or without clamping (Controls, n = 11). Blood lactate levels, pyruvate levels, and hepatic vein oxygen saturation were monitored perioperatively. RESULTS Patients were comparable with respect to resection time, intraoperative blood loss, and duration of surgery. The Pringle maneuver induced a significant increase in arterial lactate levels during liver resection when compared to Controls (2.6 +/- 0.3 vs 1.8 +/- 0.2 mmol/l; p < 0.05). Further, the Pringle maneuver significantly increased hepatic venous lactate (3.3 +/- 0.3 vs 1.6 +/- 0.3 mmol/l; p < 0.05) and lactate/pyruvate ratio in hepatic venous blood (43 +/- 8 vs 21 +/- 5; p < 0.05) during surgery. This was paralleled by a temporal decrease in hepatic venous oxygen saturation in the Pringle group (61 +/- 4 vs 73 +/- 4%; p < 0.05). CONCLUSION Our findings demonstrate that liver metabolism and tissue oxygenation were markedly affected by occlusion of the liver hilus. Restricting the use of the Pringle maneuver to cases with severe bleeding might therefore be beneficial in patients undergoing liver resection.

Effects of ETA Receptor Antagonism on Proinflammatory Gene Expression and Microcirculation Following Hepatic Ischemia/Reperfusion

Background: The objective of this study was to investigate the effect of a specific endothelinA receptor antagonist (ETA‐RA) on mRNA expression of genes encoding vasoactive mediators and proinflammatory cytokines and on the microhemodynamics (assessed by measurement of laser Doppler flow and tissue blood gases) following complete vascular exclusion of the porcine liver.

Is perioperative low molecular weight hydroxyethyl starch infusion a risk factor for delayed graft function in renal transplant recipients

BACKGROUND Crystalloid or colloid fluids may be utilized during kidney transplantation. Histopathological and clinical data indicate that hydroxyethyl starch (HES) may have nephrotoxic potential. METHODS This retrospective single-centre cohort study screened 192 and included 113 patients who underwent renal transplantation between 2003 and 2007 at University of Leipzig Medical Faculty, Germany. The primary outcome parameter was delayed graft function (DGF). Patients were divided into two groups. Patients in group CRYS (N = 73) received crystalloid solution (acetated Ringers or normal saline) only. Patients in the group HES (N = 40) received a minimum of 500 mL 6% HES 130/0.4 and additional crystalloid solution by discretion of the transplant team. RESULTS Patients in both groups did not differ with respect to demographic data and American Society of Anesthesiologists Physical Status Classification System scores, except for the donor age, which was significantly lower in the group HES. The rate of DGF was not found to be different in group CRYS (31.5%) when compared to group HES (32.5%) (P = 1.00, n.s.). CONCLUSION In this single-centre retrospective cohort study, infusion of low molecular weight 6% HES 130/0.4 during and after renal transplantation was found to have no significant negative effect upon the rate of DGF.

Endothelin receptors in the detached retina of the pig.

Endothelin-1 (ET-1) is a potent vasoconstrictor that causes hypoperfusion of the neurosensory retina. We investigated immunohistochemically the expression of the receptors for ET-1, ET(A) and ET(B), in control and locally detached retinas of the pig. Immunoreactivity for ET(A) was expressed in the innermost retinal layers and in the outer plexiform layer in control retinas, and was additionally strongly expressed by retinal blood vessels at 7 days after detachment of the sensory retina from the pigment epithelium. Immunoreactivity for ET(B) was expressed by the innermost retinal layers, by ganglion cell somata, and by Müller glial cells in the control tissue, and was not altered in its expression after detachment. The vascular expression of ET(A) may suggest a hypoperfusion of the retina after detachment.

Effects of Propofol and Isoflurane Anesthesia on the Intraocular Pressure and Hemodynamics of Pigs

To determine the conditions under which anesthetized pigs can be used in acute noninvasive investigations of ocular hydro- and hemodynamics, the intraocular pressure (IOP) of adult pigs was recorded under the following conditions: (1) after intravenous injection of propofol plus ketamine; (2) during inhalation of isoflurane, and (3) 2 h after topical administration of bimatoprost or (4) timolol. Propofol/ketamine and isoflurane induced significant decreases in the IOP. The pulsation of the ophthalmic artery appeared at a significantly higher IOP in animals anesthetized with isoflurane than in those anesthetized with propofol/ketamine. Bimatoprost and timolol did not significantly decrease the IOP within 2 h after topical administration. It is concluded that different techniques for the acute noninvasive investigation of ocular hydro- and hemodynamics are applicable in anesthetized pigs. To test the effects of antiglaucoma agents, investigation periods longer than 2 h are required. We recommend the use of intravenous propofol/ketamine anesthesia rather than isoflurane anesthesia in future experiments using pigs.

Erythropoietin stimulates hepatocyte regeneration after liver resection

Aim The increased relevance of liver surgery and transplantation as a therapeutic modality over the last two decades mandates the development of novel strategies to improve liver regeneration. Here we studied whether erythropoietin (EPO) improves liver regeneration after hepatectomy in pigs. Methods Eighteen female pigs underwent laparoscopic left lateral liver resection and were allocated randomly into three groups. No EPO was administered to the control group (group 1, n=6). Group 2 (n=6) received EPO topically to the liver resection surface in a fibrin sealant. Group 3 (n=6) received EPO topically and systemically. Pigs were sacrificed 14 days after hepatectomy. The fraction of proliferating hepatocytes was determined by ki-67 immunostaining. Liver volume was determined by the principle of Archimedes, Results Liver weight and volume were significantly increased in group 3 (1249 ± 223 g, 1073 ± 190 ml) compared to group 2 (1027 ± 167 g, 894 ± 105 ml) and group 1 (923 ± 186 g, 813 ± 165 ml). Ki-67 immunostaining of liver tissue close to the resection surface demonstrated a significantly increased percentage of proliferating hepatocytes in group 3 (4.3 ± 1.96 %) and in group 2 (3.5% ± 0.98 %) as compared to group 1 (1.15 ± 1.2 %) 14 days after hepatectomy. Conclusions Our results indicate for the first time that EPO supports liver regeneration after

Paratrend sensor as a novel method for continuous monitoring of hepatic microperfusion

DESPITE THE REMARKABLE progress in liver tranplantation, 7% of graft losses occur due to vascular complications, especially of the hepatic artery. The continuous monitoring of hepatic microcirculation following liver transplantation represents a technique for early detection of vascular complications. Multiple methods have been employed to measure liver blood flow in vivo. However, most of the methods, like indocyanine green clearance, indicator dilution, or fractionation techniques, are limited by an indirect approach and the lack of repetitive sampling. Electromagnetic and Doppler flow probes and laser flowmetry allow direct quantification of whole organ blood flow but have the drawback of short-term intraoperative application, especially in the clinical setting. All of the methods mentioned above preclude continuous monitoring of hepatic perfusion in patients over several days after liver transplantation. In contrast, assessment of hepatic pCO2, pO2, and pH with the Paratrend has the potential to provide a continuous real-time quantitative monitoring of liver microcirculation with little invasiveness. Measurement of hepatic tissue oxygenation has been shown to correlate significantly with microcirculatory impairment and liver dysfunction induced by vascular problems. Additional measurement of pCO2 and pH permits assessment of tissueacid base and the metabolic state in the liver. Up to now the Paratrend technique was not inserted in parenchymal organs except for brain/spinal cord monitoring and a hemorrhagic shock study in the liver. The aim of the present study was to evaluate the Paratend technique for continuous quantitation of hepatic microcirculation in a preclinical animal model of hepatic artery and portal vein occlusion. The Paratrend technique was compared with the established methods of laser Doppler flowmetry and pO2 measurement by the Licox device.

Percutaneous intragastric catheter (PIC) for administration of an unpalatable substance to large animals.

We studied an easy and reliable technique for administration of an unpalatable substance to large animals. There were three groups of pigs: group I (n = 6) received 1 g ethanol/kg body weight per day orally with water for 24 days, group II (n = 6) received 2 g ethanol/kg orally with water for 24 days and 4 g ethanol/kg via percutaneous intragastric catheter (PIC) for the next 24 days, group III (n = 6) received 6 g ethanol/kg via PIC for 72 days. The catheter was placed after insufflation of the stomach using an orogastric tube. PIC was successfully placed in each pig. No complications occurred during placement. The total amount of the administrated dose was assimilated each time. PIC is a safe, effective, well tolerated, and precise method of administering ethanol that is inexpensive and easy to perform. Ethanol administration via PIC is a convenient and effective mean of exposing animals to high levels of alcohol on a long-term basis.