Kristofer Nilsson
Title: Senior Lecturer School/office: School of Medical SciencesEmail: kristofer.nilsson@oru.se
Phone: +46 19 303000
Room: X1206

About Kristofer Nilsson
Kristofer F. Nilsson is an associate professor and senior lectuer in anesthesiology and intensive care at Örebro University. He is also specialist doctor in anesthesiology and intensive care at the Department of Cardiothoracic and Vascular Surgery at Örebro University Hospital.
Reasearch
Kristofer Nilsson received his medical degree and defended his thesis at Karolinska Institutet with the dissertation "Nitric oxide in experimental pulmonary embolism" in 2010. Kristofer has been active at Örebro University and Örebro University Hospital since 2011.
Kristofer runs and participates in a number of projects in experimental and clinical anesthesia and intensive care. The research projects aim to develop and evaluate innovative treatment methods for life-threatening bleeding and other conditions of circulatory collapse such as cardiac arrest. Furthermore, the research projects aim to develop methods for early detection, prevention and treatment of impaired organ function and complications associated with cardiovascular surgery and intensive care.
The research is conducted in experimental models, which is Kristofer's special competence, and as clinical studies. The experimental intensive care research includes models for different types of shock and organ failures where disease mechanisms and experimental treatment methods are investigated. The clinical studies mainly include prospective observational studies on cardiac surgery and vascular surgery patients where clinical variables and biomarkers in various body fluids are analyzed.
Kristofer is also an innovator with several patent applications and approved patents. He is also the co-founder of a small drug development company that was started thanks to research discoveries Kristofer made during his PhD work. Some of the research is conducted in collaboration with this company.
Kristofer and others have been awarded first prize in the Karolinska Innovations Contest (2005), the Innovation Bronze's Best Business Idea Award (2005) and the Swedish Intensive Care Association's 'Best Intensive Care-Related Article 2017 of the Year'.
Teaching
Kristofer has previously taught physiology at Karolinska Institutet. He is the course coordinator / examiner / assistant course coordinator for Independent Project, 30 higher education credits, at the Medical Program. He is the main supervisor and co-supervisor for several research students. Kristofer has supervised a large number of students in master thesis work at Örebro University. He has also contributed chapters to textbooks.
Research projects
Active projects
- Resuscitative endovascular balloon occlusion of the aorta in non-traumatic cardiac arrest
- Advanced endovascular vascular surgery for aortic aneurysm - mortality, incidence of complications and search for biomarkers for renal, spinal and gastrointestinal injury
- EndoVascular resuscitation and Trauma Management (EVTM) of noncompressible hemorrhage causing profound hypotension with impending cardiac arrest
- Resuscitative endovascular balloon occlusion of the aorta - Physiology and clinical aspects of an emerging technique
- Experimental and clinical studies of ruptured abdominal aortic aneurysm - effects of spontaneous and therapeutic hypothermia
- Experimental and clinical studies of the gastrointestinal tract in cardiac dysfunction and in cardiac surgery
- Ischemia-reperfusion injury during surgery and trauma - development of methods to reduce organ damage
- Combinations of arterial and venous endovascular balloon occlusion - a new method for management of traumatic retrohepatic venous and vena caval injuries?
- Nitric oxide based treatment of critical illness
- Platelet function in cardiothoracic surgery and cardiology
Completed projects
Research teams
Publications
Articles in journals
- McGreevy, D. T. , Pirouzram, A. , Gidlund, K. D. , Nilsson, K. F. & Hörer, T. M. (2023). A 12-year experience of endovascular repair for ruptured abdominal aortic aneurysms in all patients. Journal of Vascular Surgery, 77 (3), 741-749.
- Wikström, M. B. , Åström, J. , Hurtsén, A. S. , Hörer, T. M. & Nilsson, K. F. (2023). A porcine study of ultrasound-guided versus fluoroscopy-guided placement of endovascular balloons in the inferior vena cava (REBOVC) and the aorta (REBOA). Trauma surgery & acute care open, 8 (1).
- Hurtsén, A. S. , McGreevy, D. T. , Karlsson, C. , Frostell, C. G. , Hörer, T. M. & Nilsson, K. F. (2023). A randomized porcine study of hemorrhagic shock comparing end-tidal carbon dioxide targeted and proximal systolic blood pressure targeted partial resuscitative endovascular balloon occlusion of the aorta in the mitigation of metabolic injury. Intensive Care Medicine Experimental, 11 (1).
- Seifu, D. , Nilsson, K. F. , Chawla, R. , Genet, S. , Holst, M. , Debella, A. & Hellström, P. M. (2023). Detection and isolation of intestinal muscle relaxant substances from the root of Taverniera abyssinica A. Rich. Journal of Ethnopharmacology, 312.
- Dogan, E. M. , Axelsson, B. , Jauring, O. , Hörer, T. M. , Nilsson, K. F. & Edström, M. (2023). Intra-aortic and Intra-caval Balloon Pump Devices in Experimental Non-traumatic Cardiac Arrest and Cardiopulmonary Resuscitation. Journal of Cardiovascular Translational Research, 16 (4), 948-955.
- Skoog, P. , Seilitz, J. , Oikonomakis, I. , Hörer, T. M. & Nilsson, K. F. (2023). NO-Donation Increases Visceral Circulation in a Porcine Model of Abdominal Hypertension. Journal of Cardiovascular Translational Research, 16 (1), 42-50.
- Oikonomakis, I. , Brodin, D. , Hörer, T. M. , Skoog, P. , Seilitz, J. , Nilsson, K. F. , Meehan, A. D. & Jansson, K. (2022). Altered mRNA Expression Due to Rectal Perforation in a Porcine Model: A Pilot Study. Anticancer Research, 42 (6), 2827-2833.
- Oikonomakis, I. , Jansson, D. T. , Skoog, P. , Nilsson, K. F. , Meehan, A. D. , Hörer, T. M. & Jansson, K. (2022). Fully covered self-expandable metal stent placed over a stapled colon anastomosis in an animal model: A pilot study of colon metabolism over the stent. Journal of Gastroenterology and Hepatology Open (JGH Open), 6 (5), 338-343.
- McGreevy, D. , Björklund, J. , Nilsson, K. F. & Hörer, T. M. (2022). Hemodynamic Effect of Resuscitative Endovascular Balloon Occlusion Of The Aorta In Hemodynamic Instability Secondary To Acute Cardiac Tamponade In A Porcine Model. Shock, 57 (2), 291-297.
- McGreevy, D. T. , Björklund, J. , Nilsson, K. F. & Hörer, T. M. (2022). Hemodynamic Effects of Resuscitative Endovascular Balloon Occlusion of the Aorta During Hemodynamic Instability Secondary to Acute Cardiac Tamponade in a Porcine Model. Journal of Vascular Surgery, 75 (4), 18S-19S.
- McGreevy, D. , Sadeghi, M. , Nilsson, K. F. & Hörer, T. M. (2022). Low profile REBOA device for increasing systolic blood pressure in hemodynamic instability: single-center 4-year experience of use of ER-REBOA. European Journal of Trauma and Emergency Surgery, 48 (1), 307-313.
- Seiler, C. , Kristiansson, L. , Klingberg, C. , Sundh, J. , Eriksson, A. B. , Lundeqvist, D. , Nilsson, K. F. & Hårdstedt, M. (2022). Swimming-induced pulmonary edema: evaluation of prehospital treatment with continuous positive airway pressure or positive expiratory pressure device. Chest, 162 (2), 410-420.
- Seilitz, J. , Sandblom, I. , Kiszakiewicz, L. , Oikonomakis, I. , Jansson, K. , Axelsson, B. & Nilsson, K. F. (2021). A Randomized Porcine Study in Low Cardiac Output of Vasoactive and Inotropic Drug Effects on the Gastrointestinal Tract. Shock, 56 (2), 308-317.
- Wikström, M. B. , Smårs, S. M. , Karlsson, C. , Hurtsén, A. S. , Hörer, T. M. & Nilsson, K. F. (2021). A randomized porcine study of the hemodynamic and metabolic effects of combined endovascular occlusion of the vena cava and the aorta in normovolemia and in hemorrhagic shock. Journal of Trauma and Acute Care Surgery, 90 (5), 817-826.
- Mathisen, S. R. , Nilsson, K. F. & Larzon, T. (2021). A Single Center Study of ProGlide Used for Closure of Large-Bore Puncture Holes After EVAR for AAA. Vascular and Endovascular Surgery, 55 (8), 798-803.
- Duchesne, J. , McGreevy, D. , Nilsson, K. F. , DuBose, J. , Rasmussen, T. E. , Brenner, M. , Jacome, T. , Hörer, T. M. & et al. (2021). Delta Systolic Blood Pressure (SBP) Can be a Stronger Predictor of Mortality Than Pre-Aortic Occlusion SBP in Non-Compressible Torso Hemorrhage: an Abotrauma and AORTA Analysis. Shock, 56 (1S), 30-36.
- Seilitz, J. , Edström, M. , Sköldberg, M. , Westerling-Andersson, K. , Kasim, A. , Renberg, A. , Jansson, K. , Friberg, Ö. & et al. (2021). Early Onset of Postoperative Gastrointestinal Dysfunction Is Associated With Unfavorable Outcome in Cardiac Surgery: A Prospective Observational Study. Journal of Intensive Care Medicine, 36 (11), 1264-1271.
- Sadeghi, M. , Hurtsén, A. S. , Tegenfalk, J. , Skoog, P. , Jansson, K. , Hörer, T. M. & Nilsson, K. F. (2021). End-Tidal Carbon Dioxide as an Indicator of Partial REBOA and Distal Organ Metabolism in Normovolemia and Hemorrhagic Shock in Anesthetized Pigs. Shock, 56 (4), 647-654.
- Seilitz, J. , Edström, M. , Kasim, A. , Jansson, K. , Axelsson, B. & Nilsson, K. F. (2021). Intestinal fatty acid-binding protein and acute gastrointestinal injury grade in postoperative cardiac surgery patients. Journal of cardiac surgery, 36 (6), 1850-1857.
- Pirouzram, A. , Hamam, L. , Wallin, G. , Larzon, T. & Nilsson, K. F. (2021). Novel Experimental Technique to Create Size-Controlled Retroperitoneal Bleeding in the Infrarenal Aorta of Anesthetized Pigs. Innovations (Philadelphia): technology and techniques in cardiothoracic and vascular surgery, 16 (4), 379-385.
- Hurtsen, A. S. , Nilsson, I. Z. , Dogan, E. M. & Nilsson, K. F. (2020). A Comparative Study of Inhaled Nitric Oxide and an Intravenously Administered Nitric Oxide Donor in Acute Pulmonary Hypertension. Drug Design, Development and Therapy, 14, 635-644.
- Coccolini, F. , Ceresoli, M. , McGreevy, D. , Sadeghi, M. , Pirouzram, A. , Toivola, A. , Skoog, P. , Idoguchi, K. & et al. (2020). Aortic balloon occlusion (REBOA) in pelvic ring injuries: preliminary results of the ABO Trauma Registry. Updates in surgery, 72 (2), 527-536.
- Oikonomakis, I. , Hörer, T. M. , Skoog, P. , Nilsson, K. F. & Jansson, K. S. (2020). Early metabolic and inflammatory intraperitoneal changes after rectum perforation. Annals of coloproctology, 36 (6), 374-381.
- McGreevy, D. , Abu-Zidan, F. M. , Sadeghi, M. , Pirouzram, A. , Toivola, A. , Skoog, P. , Idoguchi, K. , Kon, Y. & et al. (2020). Feasibility and Clinical Outcome of Reboa in Patients with Impending Traumatic Cardiac Arrest. Shock, 54 (2), 218-223.
- Duchesne, J. , McGreevy, D. , Nilsson, K. F. , Hörer, T. M. , Brenner, M. , Rasmussen, T. , DuBose, J. & Tatum, D. (2020). IMPACT OF INTERMITTENT REBOA USE ON ISCHEMIA REPERFUSION INJURY: A TRANSLATIONAL ANALYSIS. Shock, 53 (Suppl. 1), 24-24.
- Nilsson, K. F. , Gozdzik, W. , Zielinski, S. , Ratajczak, K. , Göranson, S. P. , Rodziewicz, S. , Harbut, P. , Barteczko-Grajek, B. & et al. (2020). Pulmonary Vasodilation by Intravenous Infusion of Organic Mononitrites of 1,2-Propanediol in Acute Pulmonary Hypertension Induced by Aortic Cross Clamping and Reperfusion: A Comparison with Nitroglycerin in Anesthetised Pigs. Shock, 54 (1), 119-127.
- Wikström, M. B. , Krantz, J. , Hörer, T. M. & Nilsson, K. F. (2020). Reply to Rezende-Neto et al.. Journal of Trauma and Acute Care Surgery, 88 (6), e151-e152.
- Dogan, E. M. , Hörer, T. M. , Edström, M. , Martell, E. A. , Sandblom, I. , Marttala, J. , Krantz, J. , Axelsson, B. & et al. (2020). Resuscitative endovascular balloon occlusion of the aorta in zone I versus zone III in a porcine model of non-traumatic cardiac arrest and cardiopulmonary resuscitation: A randomized study. Resuscitation, 151, 150-156.
- Wikström, M. , Krantz, J. , Hörer, T. M. & Nilsson, K. F. (2020). Resuscitative endovascular balloon occlusion of the inferior vena cava is made hemodynamically possible by concomitant endovascular balloon occlusion of the aorta: a porcine study. Journal of Trauma and Acute Care Surgery, 88 (1), 160-168.
- Duchesne, J. , McGreevy, D. , Nilsson, K. F. , DuBose, J. , Rasmusse, T. E. , Brenner, M. , Jacome, T. , Hörer, T. M. & et al. (2020). To Ultrasound or not to Ultrasound: A REBOA Femoral Access Analysis from the ABOTrauma and AORTA Registries. Journal of endovascular resuscitation and trauma management, 4 (2), 80-87.
- Tatum, D. , McGreevy, D. , Nilsson, K. F. , DuBose, J. , Rasmussen, T. , Brenner, M. , Hörer, T. M. & Duchesne, J. (2020). TO US OR NOT TO US: A REBOA FEMORAL ACCESS ANALYSIS FROM ABOTRAUMA AND THE AORTA REGISTRY. Shock, 53 (Suppl. 1), 52-52.
- Sadeghi, M. , Dogan, E. M. , Karlsson, C. , Jansson, K. , Seilitz, J. , Skoog, P. , Hörer, T. M. & Nilsson, K. F. (2020). Total resuscitative endovascular balloon occlusion of the aorta causes inflammatory activation and organ damage within 30 minutes of occlusion in normovolemic pigs. BMC Surgery, 20 (1).
- Duchesne, J. , Tatum, D. , Hörer, T. M. , Nilsson, K. F. , McGreevy, D. , DuBose, J. & Brenner, M. (2019). IMPACT OF DELTA SYSTOLIC BLOOD PRESSURE AFTER REBOA PLACEMENT IN NON-COMPRESSIBLE TORSO HEMORRHAGE PATIENTS: AN ABOTRAUMA REGISTRY ANALYSIS. Shock, 51 (6), 159-159.
- McGreevy, D. , Dogan, S. , Oscarsson, V. , Vergari, M. , Eliasson, K. , Hörer, T. M. , Nilsson, K. F. & Norgren, L. (2019). Metabolic Response to Claudication in Peripheral Arterial Disease: a Microdialysis pilot study. Annals of Vascular Surgery, 58, 134-141.
- Seilitz, J. , Vidlund, M. , Axelsson, B. , Nilsson, K. F. , Norgren, L. , Friberg, Ö. & Jansson, K. (2019). Perioperative intraperitoneal metabolic markers in patients undergoing cardiac surgery with cardiopulmonary bypass: an exploratory pilot study. Perfusion, 34 (7), 552-560.
- Oikonomakis, I. , Jansson, D. , Hörer, T. M. , Skoog, P. , Nilsson, K. F. & Jansson, K. (2019). Results of postoperative microdialysis intraperitoneal and at the anastomosis in patients developing anastomotic leakage after rectal cancer surgery. Scandinavian Journal of Gastroenterology, 54 (10), 1261-1268.
- Dogan, E. M. , Beskow, L. , Calais, F. , Hörer, T. M. , Axelsson, B. & Nilsson, K. F. (2019). Resuscitative Endovascular Balloon Occlusion of the Aorta in Experimental Cardiopulmonary Resuscitation: Aortic Occlusion Level Matters. Shock, 52 (1), 67-74.
- Seilitz, J. , Hörer, T. M. , Skoog, P. , Sadeghi, M. , Jansson, K. , Axelsson, B. & Nilsson, K. F. (2019). Splanchnic Circulation and Intraabdominal Metabolism in Two Porcine Models of Low Cardiac Output. Journal of Cardiovascular Translational Research, 12 (3), 240-249.
- Nilsson, K. F. & Gustafsson, L. E. (2019). Treatment with new organic nitrites in pulmonary hypertension of acute experimental pulmonary embolism. Pharmacology Research & Perspectives, 7 (1).
- Sadeghi, M. , Hörer, T. M. , Forsman, D. , Dogan, E. M. , Jansson, K. , Kindler, C. , Skoog, P. & Nilsson, K. F. (2018). Blood pressure targeting by partial REBOA is possible in severe hemorrhagic shock in pigs and produces less circulatory, metabolic and inflammatory sequelae than total REBOA. Injury, 49 (12), 2132-2141.
- Nilsson, K. F. , Gozdzik, W. , Frostell, C. , Zielinski, S. , Zielinska, M. , Ratajczak, K. , Skrzypczak, P. , Rodziewicz, S. & et al. (2018). Organic mononitrites of 1,2-propanediol act as an effective NO-releasing vasodilator in pulmonary hypertension and exhibit no cross-tolerance with nitroglycerin in anesthetized pigs. Drug Design, Development and Therapy, 12, 685-694.
- Sadeghi, M. , Nilsson, K. F. , Larzon, T. , Pirouzram, A. , Toivola, A. , Skoog, P. , Idoguchi, K. , Kon, Y. & et al. (2018). The use of aortic balloon occlusion in traumatic shock: first report from the ABO trauma registry. European Journal of Trauma and Emergency Surgery, 44 (4), 491-501.
- Seilitz, J. , Westerling-Andersson, K. , Axelsson, B. & Nilsson, K. F. (2017). Assessment of acute gastrointestinal injury score in postoperative cardiac surgical patients. Acta Anaesthesiologica Scandinavica, 61 (8), 1044-1044.
- McGreevy, D. , Dogan, E. , Toivola, A. , Bilos, L. , Pirouzram, A. , Nilsson, K. F. & Hörer, T. (2017). Endovascular Resuscitation with Aortic Balloon Occlusion in Non-Trauma Cases: First use of ER-REBOA in Europe. Journal of Endovascular Resuscitation and Trauma Management (1), 42-49.
- Nilsson, K. F. , Sandin, J. , Gustafsson, L. E. & Frithiof, R. (2017). The novel nitric oxide donor PDNO attenuates ovine ischemia-reperfusion induced renal failure. Intensive Care Medicine Experimental, 5 (1).
- Hörer, T. M. , Cajander, P. , Jans, A. & Nilsson, K. F. (2016). A case of partial aortic balloon occlusion in an unstable multi-trauma patient. Trauma, 18 (2), 150-154.
- Hörer, T. M. , Skoog, P. , Quell, R. , Nilsson, K. F. , Larzon, T. & Souza, D. R. (2016). No-touch technique for radiocephalic arteriovenous fistula - surgical technique and preliminary results. Journal of Vascular Access, 17 (1), 6-12.
- Skoog, P. , Hörer, T. , Nilsson, K. F. , Agren, G. , Norgren, L. & Jansson, K. (2015). Intra-abdominal Hypertension: An Experimental Study of Early Effects on Intra-abdominal Metabolism. Annals of Vascular Surgery, 29 (1), 128-137.
- Skoog, P. , Hörer, T. M. , Nilsson, K. F. , Norgren, L. , Larzon, T. & Jansson, K. (2014). Abdominal Hypertension and Decompression: The Effect on Peritoneal Metabolism in an Experimental Porcine Study. European Journal of Vascular and Endovascular Surgery, 47 (4), 402-410.
- Hörer, T. M. , Skoog, P. , Nilsson, K. F. , Oikonomakis, I. , Larzon, T. , Norgren, L. & Jansson, K. (2014). Intraperitoneal Metabolic Consequences of Supraceliac Aortic Balloon Occlusion in an Experimental Animal Study Using Microdialysis. Annals of Vascular Surgery, 28 (5), 1286-1295.
- Guan, N. N. , Nilsson, K. F. , Wiklund, P. N. & Gustafsson, L. E. (2014). Release and inhibitory effects of prostaglandin D2 in guinea pig urinary bladder and the role of urothelium. Biochimica et Biophysica Acta, 1840 (12), 3443-3451.
- Nilsson, K. F. , Lundgren, M. , Agvald, P. , Adding, C. , Linnarsson, D. & Gustafsson, L. (2011). Formation of new bioactive organic nitrites and their identification with gas chromatography-mass spectrometry and liquid chromatography coupled to nitrite reduction. Biochemical Pharmacology, 82 (3), 248-259.
- Nilsson, K. F. , Grishina, V. A. , Glaumann, C. & Gustafsson, L. E. (2010). Estimation of endogenous adenosine activity at adenosine receptors in guinea-pig ileum using a new pharmacological method. Acta Physiologica, 199 (2), 231-241.
- Nilsson, K. F. , Gustafsson, L. E. , Adding, L. C. , Linnarsson, D. & Agvald, P. (2007). Increase in exhaled nitric oxide and protective role of the nitric oxide system in experimental pulmonary embolism. British Journal of Pharmacology, 150 (4), 494-501.
- Nilsson, K. F. (2007). NO enigma in pulmonary embolism. Acta Physiologica, 191 (3), 169-169.
- Agvald, P. , Adding, L. C. , Nilsson, K. F. , Gustafsson, L. E. & Linnarsson, D. (2006). Increased expired NO and roles of CO2 and endogenous NO after venous gas embolism in rabbits. European Journal of Applied Physiology, 97 (2), 210-215.
Articles, reviews/surveys
- Hörer, T. M. , Skoog, P. , Pirouzram, A. , Nilsson, K. F. & Larzon, T. (2016). A small case series of aortic balloon occlusion in trauma: lessons learned from its use in ruptured abdominal aortic aneurysms and a brief review. European Journal of Trauma and Emergency Surgery, 42 (5), 585-592.
Chapters in books
- Nilsson, K. F. & Axelsson, B. (2020). Postoperative critical care management considerations. In: Hörer, T., DuBose, J.J., Rasmussen, T., White, J.M., Endovascular resuscitation and trauma management: Bleeding and Haemodynamic Control (pp. 229-242). . Springer.
- Jansen, J. , the EVTM group, -. , Hörer, T. M. & Nilsson, K. F. (2017). Management of the REBOA patient in the intensive care unit. In: Top Stent: The art of EndoVascular hybrid Trauma and bleeding Management (pp. 195-203). . Örebro University Hospital.
Conference papers
- Stene Hurtsén, A. , Sadeghi, M. , Tegenfalk, J. , Skoog, P. , Jansson, K. , Hörer, T. M. & Nilsson, K. F. (2019). End-tidal carbon dioxide as an indicator of partial REBOA and distal organ metabolism in normovolemia and hemorrhagic shock in anesthetized pigs. Paper presented at Pan-American Endovascular Resuscitation and Trauma Management - PA-EVTM 2019, Denver, Colorado, USA, November 17-18, 2019.
Manuscripts
- Oikonomakis, I. , Brodin, D. , Hörer, T. M. , Skoog, P. , Seilitz, J. , Nilsson, K. F. , Meehan, A. D. & Jansson, K. Altered mRNA expression due to rectum perforation in a porcine model : A pilot study.
- Sadeghi, M. , Stene Hurtsén, A. , Tegenfalk, J. , Skoog, P. , Jansson, K. , Hörer, T. M. & Nilsson, K. F. End-tidal carbon dioxide as an indicator of partial REBOA and distal organ metabolism in normovolemia and hemorrhagic shock in anesthetized pigs.
- Oikonomakis, I. , Jansson, D. T. , Skoog, P. , Nilsson, K. F. , Meehan, A. D. , Hörer, T. M. & Jansson, K. Fully covered self-expandable metal stent placed over a colon anastomosis in an animal model : A pilot study of colon metabolism over the stent.
- Dogan, E. M. , Axelsson, B. , Jauring, O. , Hörer, T. M. , Nilsson, K. F. & Edström, M. Intra-aortic and intra-caval balloon pump devices in experimental cardiac arrest.
- Sadeghi, M. , Dogan, E. M. , Karlsson, C. , Jansson, K. , Seilitz, J. , Skoog, P. , Hörer, T. M. & Nilsson, K. F. Total resuscitative endovascular balloon occlusion of the aorta causes inflammatory activation and organ damage within 30 minutes of occlusion in normovolemic pigs.