Gereon Schälte

Comparison of electrical velocimetry and thermodilution techniques for the measurement of cardiac output

Aim:  To compare a new method of non‐invasive determination of cardiac output based on electrical velocimetry (EV‐CO) with invasive thermodilution methods.

The intraoperative decrease of selenium is associated with the postoperative development of multiorgan dysfunction in cardiac surgical patients

Objective:The trace elements selenium, copper, and zinc are essential for maintaining the oxidative balance. A depletion of antioxidative trace elements has been observed in critically ill patients and is associated with the development of multiorgan dysfunction and an increased mortality. Cardiac surgery using cardiopulmonary bypass provokes ischemia-reperfusion-mediated oxidative stress. We hypothesized that an intraoperative decrease of circulating trace elements may be involved in this response. Design:Prospective observational clinical study. Setting:University hospital cardiothoracic operation theater and intensive care unit. Patients:Sixty patients (age 65 ± 14 yrs) undergoing cardiac surgery with the use of cardiopulmonary bypass. Measurements and Main Results:Whole blood concentrations of selenium, copper, and zinc were measured after induction of anesthesia and 1 hr after admission to the intensive care unit. All patients were separated in a priori defined subgroups according to the development of no organ failure, single organ failure, and ≥2 organ failures in the postoperative period. Results:Fifty patients exhibited a significant selenium deficiency already before surgery, whereas copper and zinc concentrations were within the reference range.In all patients, blood levels of selenium, copper, and zinc were significantly reduced after end of surgery when compared to preoperative values (selenium: 89.05 ± 12.65 to 70.84 ± 10.46 &mgr;g/L; zinc: 5.15 ± 0.68 to 4.19 ± 0.73 mg/L; copper: 0.86 ± 0.15 to 0.65 ± 0.14 mg/L; p < .001).During their intensive care unit stay, 17 patients were free from any organ failure, while 31 patients developed single-organ failure and 12 patients multiple organ failure.Multilogistic regression analysis showed that selenium concentrations at end of surgery were independently associated with the postoperative occurrence of multiorgan failure (p = .0026, odds ratio 0.8479, 95% confidence interval 0.7617 to 0.9440). Conclusions:Cardiac surgery using cardiopulmonary bypass resulted in a profound intraoperative decrease of whole blood levels of antioxidant trace elements. Low selenium concentrations at end of surgery were an independent predictor for the postoperative development of multiorgan failure.

Thoracic stent graft sizing for frozen elephant trunk repair in acute type A dissection

OBJECTIVE Although stenting of the descending aorta simultaneously with proximal aortic repair has become an accepted part of the therapy for acute type A dissection, no general recommendations have been accepted regarding the choice of diameter and length of the stent grafts. The present study explored the safety and effectiveness of sizing the stent graft of the hybrid prosthesis in relation to the total aortic diameter and extending the landing zone to the level of the T10-T12 vertebrae. METHODS The frozen elephant trunk procedure was performed on 32 patients with acute type A aortic dissection. The stent graft size was chosen according to the total aortic diameter measured on contrast-enhanced computed tomography scans. The stent graft was inserted with the distal landing zone at the level of vertebrae T10-T12. All patients underwent computed tomography or magnetic resonance angiography before discharge; 8 patients underwent subsequent endovascular stent extension. RESULTS The 30-day survival was 100%, with 3.1% (1/32) overall mortality at 17 ± 4 months (range, 1-33) of follow-up. The postoperative complications included pneumonia in 5, pulmonary embolism in 3, sepsis in 1, and permanent recurrent laryngeal nerve damage in 1 patient. No ischemic brain or spinal cord injury occurred. During follow-up, no endoleaks or false lumen patency developed. CONCLUSIONS Sizing the stent graft of the hybrid prosthesis according to the total aortic diameter and choosing a distal landing zone between vertebrae T10 and T12 is safe, with low midterm mortality and morbidity. It allows an extensive repair of the dissected aorta with early definite occlusion of the false lumen and prepares for potential endovascular extension of the graft.

Selenium blood concentrations in patients undergoing elective cardiac surgery and receiving perioperative sodium selenite

OBJECTIVES We recently reported that cardiac surgical patients in our institution exhibited low selenium blood levels preoperatively, which were further aggravated during surgery and independently associated with the development of postoperative multiorgan failure. Low circulating selenium levels result in a decreased antioxidant capacity. Both can be treated effectively by sodium-selenite administration. Little is known about the kinetics of exogenously administered sodium-selenite during acute perioperative oxidative stress. The aim of this study was to assess the effects of perioperative high-dose sodium-selenite administration on selenium blood concentrations in cardiac surgical patients. METHODS One hundred four cardiac surgical patients were enrolled in this prospective observational trial. Patients received an intravenous bolus of 2000 μg selenium after an induction of anesthesia and 1000 μg selenium every day further during their intensive care unit (ICU) stay. Selenium blood levels were measured at regular intervals. RESULTS Preoperative sodium-selenite administration increased selenium blood concentrations to normal values on ICU admission, but failed to prevent a significant decrease of circulating selenium on the first postoperative day. During the further ICU stay, selenium blood levels were normalized by the administration strategy and did not exceed the German reference range. No acute selenium-specific side effects occurred. When matching the participating patients to a historical control group without sodium-selenite administration, the chosen strategy was associated with a decrease in SAPS II (23 ± 7 versus 29 ± 8, P = 0.005) and SOFA scores (4 ± 3 versus 7 ± 2, P = 0.007) on the first postoperative day, but was unable to improve the postoperative outcome in patients staying >1 d in ICU. CONCLUSIONS Despite preemptive high-dose sodium-selenite administration, cardiac surgical patients experienced a significant decrease in circulating selenium levels on the first postoperative day.

Laypersons can successfully place supraglottic airways with 3 minutes of training. A comparison of four different devices in the manikin

IntroductionSupraglottic airway devices have frequently been shown to facilitate airway management and are implemented in the ILCOR resuscitation algorithm. Limited data exists concerning laypersons without any medical or paramedical background. We hypothesized that even laymen would be able to operate supraglottic airway devices after a brief training session.MethodsFour different supraglottic airway devices: Laryngeal Mask Classic (LMA), Laryngeal Tube (LT), Intubating Laryngeal Mask (FT) and CobraPLA (Cobra) were tested in 141 volunteers recruited in a technical university cafeteria and in a shopping mall. All volunteers received a brief standardized training session. Primary endpoint was the time required to definitive insertion. In a short questionnaire applicants were asked to assess the devices and to answer some general questions about BLS.ResultsThe longest time to insertion was observed for Cobra (31.9 ± 27.9 s, range: 9-120, p < 0.0001; all means ± standard deviation). There was no significant difference between the insertion times of the other three devices. Fewest insertion attempts were needed for the FT (1.07 ± 0.26), followed by the LMA (1.23 ± 0.52, p > 0.05), the LT (1.36 ± 0.61, p < 0.05) and the Cobra (1.45 ± 0.7, p < 0.0001). Ventilation was achieved on the first attempt significantly more often with the FT (p < 0.001) compared to the other devices. Nearly 90% of the participants were in favor of implementing supraglottic airway devices in first aid algorithms and classes.ConclusionLaypersons are able to operate supraglottic airway devices in manikin with minimal instruction. Ventilation was achieved with all devices tested after a reasonable time and with a high success rate of > 95%. The use of supraglottic airway devices in first aid and BLS algorithms should be considered.

The intuitive use of laryngeal airway tools by first year medical students

BackgroundProviding a secured airway is of paramount importance in cardiopulmonary resuscitation. Although intubating the trachea is yet seen as gold standard, this technique is still reserved to experienced healthcare professionals. Compared to bag-valve facemask ventilation, however, the insertion of a laryngeal mask airway offers the opportunity to ventilate the patient effectively and can also be placed easily by lay responders. Obviously, it might be inserted without detailed background knowledge.The purpose of the study was to investigate the intuitive use of airway devices by first-year medical students as well as the effect of a simple, but well-directed training programme. Retention of skills was re-evaluated six months thereafter.MethodsThe insertion of a LMA-Classic and a LMA-Fastrach performed by inexperienced medical students was compared in an airway model. The improvement on their performance after a training programme of overall two hours was examined afterwards.ResultsPrior to any instruction, mean time to correct placement was 55.5 ± 29.6 s for the LMA-Classic and 38.1 ± 24.9 s for the LMA-Fastrach. Following training, time to correct placement decreased significantly with 22.9 ± 13.5 s for the LMA-Classic and 22.9 ± 19.0 s for the LMA-Fastrach, respectively (p < 0.05). After six months, the results are comparable prior (55.6 ± 29.9 vs 43.1 ± 34.7 s) and after a further training period (23.5 ± 13.2 vs 26.6 ± 21.6, p < 0.05).ConclusionUntrained laypersons are able to use different airway devices in a manikin and may therefore provide a secured airway even without having any detailed background knowledge about the tool. Minimal theoretical instruction and practical skill training can improve their performance significantly. However, refreshment of knowledge seems justified after six months.

Xenon consumption during general surgery: a retrospective observational study

BackgroundHigh costs still limits the widespread use of xenon in the clinical practice. Therefore, we evaluated xenon consumption of different delivery modes during general surgery.MethodsA total of 48 patients that underwent general surgery with balanced xenon anaesthesia were retrospectively analysed according to the mode of xenon delivery during maintenance phase (ECO mode, AUTO mode or MANUAL mode).ResultsXenon consumption was highest during the wash-in phase (9.4 ± 2.1l) and further decreased throughout maintenance of anaesthesia. Comparison of different xenon delivery modes revealed significant reduced xenon consumption during ECO mode (18.5 ± 3.7L (ECO) vs. 24.7 ± 11.5L (AUTO) vs. 29.6 ± 14.3L (MANUAL); p = 0.033). No differences could be detected with regard to anaesthetic depth, oxygenation or performance of anaesthesia.ConclusionThe closed-circuit respirator Felix Dual offers effective reduction of xenon consumption during general surgery when ECO mode is used.

Milrinone Relaxes Pulmonary Veins in Guinea Pigs and Humans

Introduction The phosphodiesterase-III inhibitor milrinone improves ventricular contractility, relaxes pulmonary arteries and reduces right ventricular afterload. Thus, it is used to treat heart failure and pulmonary hypertension (PH). However, its action on pulmonary veins (PVs) is not defined, although particularly PH due to left heart disease primarily affects the pulmonary venous bed. We examined milrinone-induced relaxation in PVs from guinea pigs (GPs) and humans. Material and Methods Precision-cut lung slices (PCLS) were prepared from GPs or from patients undergoing lobectomy. Milrinone-induced relaxation was studied by videomicroscopy in naïve PVs and in PVs pre-constricted with the ETA-receptor agonist BP0104. Baseline luminal area was defined as 100%. Intracellular cAMP was measured by ELISA and milrinone-induced changes of segmental vascular resistances were studied in the GP isolated perfused lung (IPL). Results In the IPL (GP), milrinone (10 µM) lowered the postcapillary resistance of pre-constricted vessels. In PCLS (GP), milrinone relaxed naïve and pre-constricted PVs (120%) and this relaxation was attenuated by inhibition of protein kinase G (KT 5823), adenyl cyclase (SQ 22536) and protein kinase A (KT 5720), but not by inhibition of NO-synthesis (L-NAME). In addition, milrinone-induced relaxation was dependent on the activation of KATP-, BKCa 2+- and Kv-channels. Human PVs also relaxed to milrinone (121%), however only if pre-constricted. Discussion Milrinone relaxes PVs from GPs and humans. In GPs, milrinone-induced relaxation is based on KATP-, BKCa 2+- and Kv-channel-activation and on cAMP/PKA/PKG. The relaxant properties of milrinone on PVs lead to reduced postcapillary resistance and hydrostatic pressures. Hence they alleviate pulmonary edema and suggest beneficial effects of milrinone in PH due to left heart disease.

Safety and pitfalls in frozen elephant trunk implantation

The frozen elephant trunk (FET) procedure, or open stent grafting, is a tool for the combined open and endovascular treatment via a median sternotomy of extensive aortic disease involving both aortic arch and descending thoracic aorta. The technique aims to stabilize the maximum extent of the thoracic aorta in one step, with the goal of either rendering a secondary intervention to the downstream aorta unnecessary or producing an easy landing zone for secondary thoracic endovascular aortic repair (TEVAR) or open surgery. Even though large case series have reported good results, we still have no conclusive evidence as to which patients and what kind of pathologies benefit from this technique. The surgical sequences described for total arch replacement with the FET procedure are just as varied as the associated devices and indications. This article focuses on important perioperative and surgical aspects, as well as potential complications during FET procedures.

Influence of temperature on the positive inotropic effect of levosimendan, dobutamine and milrinone

Background and objective Patients in cardiac surgery and critically ill patients often demonstrate either hypothermia or fever. In addition, owing to heart failure, they frequently require inotropic support. The relative effectiveness of modern inotropic agents at various temperatures has not yet been evaluated. Therefore, we investigated the influence of levosimendan, dobutamine and milrinone on the contractile response of myocardial trabeculae at various temperatures. Methods A total of 120 guinea pig ventricular trabeculae were placed in oxygenated 4-(2-hydroxyethyl)-1-piperazineethanesulphonic acid (HEPES) buffer, stimulated at a frequency of 1.3 Hz and randomly assigned to a temperature of 31°C, 34°C, 37°C or 40°C. Concentrations of all substances were increased stepwise from 10−9 to 10−5 mol l−1 (milrinone up to 10−4 mol l−1). Maximum developed force, time to peak tension, Tsystolic50% and Tdiastolic50% were continuously recorded. Results All agents showed a dose-dependent positive inotropic effect (P < 0.0001 for all). Levosimendan acted at every temperature as a positive inotrope (P = 0.0643). Dobutamine-related inotropy showed a clear trend towards temperature dependence, although statistical evaluation did not prove this (P = 0.0624). Milrinone-related inotropy was abolished at 31°C and 34°C, and temperature dependence was significant (P < 0.0001). Hypothermia induced a positive inotropic effect. Conclusion Our results suggest no modulation of levosimendan-induced inotropy under the experimental temperatures tested. This observation is possibly due to its Ca2+-sensitizing mechanism, which might not be influenced by temperature-related changes in intracellular Ca2+ levels. In contrast, the inotropic effect of cyclic AMP-coupled dobutamine and milrinone is suppressed under hypothermia-related interaction with intracellular Ca2+ homeostasis. Hence, levosimendan might prove to be the preferred inotropic drug in hypothermic patients.