Stefan Huber

The induction of mild hypothermia improves systolic function of the resuscitated porcine heart at no further sympathetic activation

Aim:u2002 Mild hypothermia (MH) after cardiac arrest attenuates hypoxic brain injury and improves survival. As MH increases contractility in normal hearts, we hypothesized that MH improves cardiovascular function after cardiac arrest.

The Influence of Medical Information on the Perioperative Course of Stress in Cardiac Surgery Patients

Cardiac surgery correlates with increased perioperative stress and anxiety. We tested whether preoperative extensive oral information in combination with more personal attention by the surgeon is associated with any effect on patients’ perioperative stress, anxiety, and well-being. Sixty patients awaiting open heart surgery were divided into two groups. Group I consisted of 30 patients who received routine medical information through an informative pamphlet. In Group II (n = 30 patients), additional, extensive oral medical information and more personal attention by the surgeon was provided before surgery. Salivary cortisol, plasma cortisol, state anxiety, and patients’ well-being were measured perioperatively. Extensive preoperative oral information in combination with more personal attention by the physician did not have any significant influence on the perioperative psychoendocrinologic course of stress. During transport to the operating room, salivary cortisol increased significantly (P < 0.001) in both groups (ranges are 95% confidence intervals) (Group I, 23.2 nmol/L [17.1–31.5]; Group II, 14.6 nmol/L [9.9–21.3]) versus the first day in the hospital (Group I, 8.4 nmol/L [6.2–11.4]; Group II, 6.7 nmol/L [5.3–8.6]). After the induction of anesthesia, plasma cortisol decreased significantly (P < 0.001) in both groups (Group I, 170.1 nmol/L [143.6–201.4]; Group II, 172.0 nmol/L [142.2–208.1]) versus preoperative levels. After surgery, well-being decreased (P = 0.003) in all patients, and patients’ state anxiety was reduced (P = 0.001) after surgery. Our data demonstrate a lack of effect of extensive oral medical information that was presented as part of clinical routine on the perioperative psychoendocrinologic course of stress. High levels of stress during transport to the operating room were detected.

Mild hypothermia attenuates circulatory and pulmonary dysfunction during experimental endotoxemia.

Objective:We tested whether mild hypothermia impacts on circulatory and respiratory dysfunction during experimental endotoxemia. Design:Randomized controlled prospective experimental study. Setting:Large animal facility, Medical University of Graz, Austria. Subjects:Thirteen anesthetized and mechanically ventilated pigs. Interventions:Lipopolysaccharide was administered for 4 hours. With the beginning of lipopolysaccharide infusion, animals were assigned to either normothermia (38°C, n = 7) or mild hypothermia (33°C, n = 6, intravascular cooling) and followed for 8 hours in total. Measurements and Main Results:At the end of the protocol, cardiac output was lower in mild hypothermia than in normothermia (4.5u2009±u20090.4u2009L/min vs 6.6u2009±u20090.4u2009L/min, p < 0.05), but systemic vascular resistance (885u2009±u200977 dyn·s/cm5 vs 531u2009±u200929 dyn·s/cm5, p < 0.05) and (77% ± 6% vs 54% ± 3%, p < 0.05) were higher. Indices of left ventricular contractility in vivo were not different between groups. The high-frequency band in spectral analysis of heart rate variability indicated a better preserved vagal autonomic modulation of sinuatrial node activity in mild hypothermia versus normothermia (87u2009±u20095 vs 47u2009±u20095, normalized units, p < 0.05). Plasma norepinephrine levels were elevated compared with baseline in normothermia (2.13u2009±u20090.27 log pg/mL vs 0.27u2009±u20090.17 log pg/mL, p < 0.05) but not in mild hypothermia (1.02u2009±u20090.31 vs 0.55u2009±u20090.26, p = not significant). At 38°C in vitro, left ventricular muscle strips isolated from the mild hypothermia group had a higher force response to isoproterenol. SaO2 (100% ± 0% vs 92% ± 3%, p < 0.05) and the oxygenation index (PO2/FIO2, 386u2009±u200952 mmu2009Hg vs 132u2009±u200932 mmu2009Hg, p < 0.05) were substantially higher in mild hypothermia versus normothermia. Plasma cytokine levels were not consistently different between groups (interleukin 10) or higher (tumor necrosis factor-&agr; and interleukin 6 and 8) during mild hypothermia versus normothermia. Conclusion:The induction of mild hypothermia attenuates cardiac and respiratory dysfunction and counteracts sympathetic activation during experimental endotoxemia. This was not associated with lower plasma cytokine levels, indicating a reduction of cytokine responsiveness by mild hypothermia.

Left ventricular diastolic dysfunction during acute myocardial infarction: effect of mild hypothermia.

Background Mild hypothermia (MH) decreases infarct size and mortality in experimental reperfused myocardial infarction, but may potentiate ischaemia-induced left ventricular (LV) diastolic dysfunction. Methods In anaesthetized pigs (70 ± 2 kg), polystyrol microspheres (45 μm) were infused repeatedly into the left circumflex artery until cardiac power output decreased >40%. Then, pigs were assigned to normothermia (NT, 38.0 °C, n = 8) or MH (33.0 °C, n = 8, intravascular cooling) and followed for 6 h (CME 6 h). *p < 0.05 vs baseline, †p < 0.05 vs NT. Results In NT, cardiac output (CO) decreased from 6.2 ± 0.3 to 3.4 ± 0.2* l/min, and heart rate increased from 89 ± 4 to 101 ± 6* bpm. LV end-diastolic volume fell from 139 ± 8 to 64 ± 4 ml*, while LV ejection fraction remained constant (49 ± 1 vs 53 ± 4%). The corresponding end-diastolic pressure–volume relationship was progressively shifted leftwards, reflecting severe LV diastolic dysfunction. In MH, CO fell to a similar degree. Spontaneous bradycardia compensated for slowed LV relaxation, and the leftward shift of the end-diastolic pressure–volume relationship was less pronounced during MH. MH increased systemic vascular resistance, such that mean aortic pressure remained higher in MH vs NT (69 ± 2† vs 54 ± 4 mmHg). Mixed venous oxygen saturation at CME 6 h was higher in MH than in NT (59 ± 4† vs 42 ± 2%) due to lowered systemic oxygen demand during cooling. Conclusion We conclude that (i) an acute loss of end-diastolic LV compliance is a major component of acute cardiac pump failure during experimental myocardial infarction, and that (ii) MH does not potentiate this diastolic LV failure, but stabilizes haemodynamics and improves systemic oxygen supply/demand imbalance by reducing demand.

Mild hypothermia induces incomplete left ventricular relaxation despite spontaneous bradycardia in pigs.

Mild hypothermia (MH) decreases left ventricular (LV) end‐diastolic capacitance. We sought to clarify whether this results from incomplete relaxation.

A porcine model of early atrial fibrillation using a custom-built, radio transmission-controlled pacemaker

Mechanisms underlying atrial remodeling toward atrial fibrillation (AF) are incompletely understood. We induced AF in 16 pigs by 6weeks of rapid atrial pacing (RAP, 600bpm) using a custom-built, telemetrically controlled pacemaker. AF evolution was monitored three times per week telemetrically in unstressed, conscious animals. We established a dose-response relationship between RAP duration and occurrence of sustained AF >60minutes. Left atrial (LA) dilatation was present already at 2weeks of RAP. There was no evidence of left ventricular heart failure after 6weeks of RAP. As a proof-of-principle, arterial hypertension was induced in 5/16 animals by implanting desoxycorticosterone acetate (DOCA, an aldosterone-analog) subcutaneously to accelerate atrial remodeling. RAP+DOCA resulted in increased AF stability with earlier onset of sustained AF and accelerated anatomical atrial remodeling with more pronounced LA dilatation. This novel porcine model can serve to characterize effects of maladaptive stimuli or protective interventions specifically during early AF.

Arterial hypertension drives arrhythmia progression via specific structural remodeling in a porcine model of atrial fibrillation

BACKGROUNDnArterial hypertension (HT) contributes to progression of atrial fibrillation (AF) via unknown mechanisms.nnnOBJECTIVEnWe aimed to characterize electrical and structural changes accounting for increased AF stability in a large animal model of rapid atrial pacing (RAP)-induced AF combined with desoxycorticosterone acetate (DOCA)-induced HT.nnnMETHODSnEighteen pigs were instrumented with right atrial endocardial pacemaker leads and custom-made pacemakers to induce AF by continuous RAP (600 beats/min). DOCA pellets were subcutaneously implanted in a subgroup of 9 animals (AF+HT group); the other 9 animals served as controls (AF group). Final experiments included electrophysiology studies, endocardial electroanatomic mapping, and high-density mapping with epicardial multielectrode arrays. In addition, 3-dimensional computational modeling was performed.nnnRESULTSnDOCA implantation led to secondary HT (median [interquartile range] aortic pressure 109.9 [100-137] mm Hg in AF+HT vs 82.2 [79-96] mm Hg in AF; P < .05), increased AF stability (55.6% vs 12.5% of animals with AF episodes lasting >1 hour; P < .05), concentric left ventricular hypertrophy, atrial dilatation (119 ± 31 cm2 in AF+HT vs 78 ± 23 cm2 in AF; Pxa0<xa0.05), and fibrosis. Collagen accumulation in the AF+HT group was mainly found in non-intermyocyte areas (1.62 ± 0.38 cm3 in AF+HT vs 0.96 ± 0.3 cm3 in AF; P < .05). Left and right atrial effective refractory periods, action potential durations, endo- and epicardial conduction velocities, and measures of AF complexity were comparable between the 2 groups. A 3-dimensional computational model confirmed an increase in AF stability observed in the inxa0vivo experiments associated with increased atrial size.nnnCONCLUSIONnIn this model of secondary HT, higher AF stability after 2 weeks of RAP is mainly driven by atrial dilatation.

Endoscopic vein harvesting in coronary artery bypass surgery

ZusammenfassungGRUNDLAGEN: Wundheilungsstörungen und Wundinfektionen am Bein nach Entnahme der Vena saphena magna (VSM) für aorto-coronare Bypassoperationen (CABG) stellen eine schwerwiegende Komplikation dar. Speziell bei Patienten mit Adipositas, Diabetes mellitus und peripheren Durchblutungsstörungen treten vermehrt tiefreichende Wundheilungsstörungen mit starken Schmerzen auf. METHODIK: Unser Ziel war es, die Anwendbarkeit und die Ergebnisse der endoskopischen Beinvenenentnahme zu untersuchen. Von Oktober 2002 bis November 2005 setzten wir bei 63 Patienten mit koronarer Herzerkrankung, die sich einer CABG-Operation unterziehen mussten, das VasoView® System der Fa. Guidant zur endoskopischen Entnahme der VSM ein. Wir untersuchten Entnahmezeit und Präparationszeit der Vene, intraoperative Komplikationen und Konversion zur offenen Entnahmetechnik, Qualität der entnommen Vene und Anzahl an Reparaturnähten, Flowwerte der eingesetzten Venengrafts und postoperative Wundkomplikationen. ERGEBNISSE: Die mittlere Entnahmezeit betrug 37,5 min (19–72 min). Aufgrund von Blutungen und Fettgewebsansammlungen im Präparationskanal musste bei 4 Patienten zur offenen Entnahmetechnik konvertiert werden. Die Qualität der präparierten Venen wurde mit einem Score von 1,4 auf einer Skala von 1–5 beurteilt. Die Seitenäste wurden ligiert und geklippt, im Mittel mussten 1,4 Löcher pro Vene von ausgerissenen Seitenästen mit Prolene übernäht werden. Bei einer Patientin war die Wand der endoskopisch entnommenen VSM zu dünn und varikös, sodass die Vene nicht als Bypassgraft verwendet werden konnte. Bei 17 Patienten (29%) wurde aus der endoskopisch präparierten Vene ein Graft eingesetzt, bei 37 Patienten (64%) 2 Grafts und bei 4 Patienten (7%) 3 Grafts. Die Flowwerte der eingesetzten Grafts waren im Mittel 50 ml/min (10–159 ml/min). Postoperativ traten bei 22 Patienten (37%) umschriebene Hämatome entlang des Präparationskanals auf, die bei Entlassung gänzlich zurückgegangen waren. Wundheilungsstörungen und Wundinfektionen am Bein traten bei keinem der Patienten auf. SCHLUSSFOLGERUNGEN: Die Vorteile der endoskopischen Entnahmetechnik der VSM sind die geringere Traumatisierung des Beines und die schmerzfreie und schnellere Mobilisierbarkeit der Patienten. Die Präparationszeit der Vene ist trotz learning curve akzeptabel. Die Operationszeit wird nicht verzögert. Die Visualisierung ist ausgezeichnet und die Handhabung des Systems ist schnell erlernbar. Die präparierten Venen sind mit dieser Entnahmetechnik den konventionell offen entnommenen Venen ebenbürtig, mit dem Vorteil der geringeren postoperativen Schmerzen und dem besseren kosmetischen Ergebnis. Die Konversionsrate zur offenen Technik ist gering (4 von 63). Postoperative Wundkomplikationen sind nicht zu erwarten.SummaryBACKGROUND: Leg wound complications and infections after harvesting of the greater saphenous vein (GSV) in coronary artery bypass surgery (CABG) represent a serious source of patient morbidity. Especially, in patients with obesity, diabetes and peripheral vascular disease, severe wound complications with increased pain occur more often. METHODS: Our aim was to evaluate the feasibility and the results of the endoscopic saphenous vein harvesting. From October 2002 until November 2005, in 63 patients with coronary artery disease, scheduled for elective CABG surgery, endoscopic vein harvesting (EVH) was performed using the Guidant VasoView® System. We investigated harvesting time and preparation time for the vein, intraoperative complications and conversion to traditional open harvesting, quality of the harvested vein including number of repairs needed, flow rates of the bypass grafts and postoperative wound related complications. RESULTS: The mean harvesting time was 37.5 min (19–72 min). Four patients had to be converted to the open harvesting technique because of bleeding and massive build up of fatty tissue inside the preparation tunnel. The quality of the harvested veins was assessed with a score of 1.4 on a scale ranging from 1 to 5. Side branches were either ligated or clipped. Small holes tears not suitable for tying were repaired with a prolene suture. The mean number of repairs was 1.4. In one patient, the wall of the endoscopically harvested vein was too thin and varicose, so that the vein was not suited to be used as a bypass graft. In 17 patients (29%) the EVH vein was needed for only one graft, in 37 patients (64%) the harvested vein was used for 2 grafts, and in 4 patients (7%) for 3 grafts. The mean flow rate of the EVH grafts was 50 ml/min (10–159 ml/min). Postoperatively, 22 patients (37%) had hematomas along the course of the preparation tunnel. These hematomas, however, had diminished at the time of discharge. There were no leg wound complications or infections. CONCLUSIONS: The advantages of EVH are the reduced trauma to the leg and the painless and faster mobilization of the patients. The harvesting time is acceptable despite a learning curve. The operative time is not prolonged. The visualisation of the EVH system is excellent and the handling can be adopted easily. The quality of the endoscopically harvested veins is equal to an open harvest technique, with the advantages of less postoperative pain and a better cosmetic result. The conversion rate is low (4 of 63). Postoperative wound complications are not to be expected.