Christoph Schelenz

The use and safety of transoesophageal echocardiography in the general ICU – a minireview

Background:  The efficacy of transoesophageal echocardiography (TEE) has been evaluated predominantly in medical and cardiac surgical ICUs. This article reviews the pertinent literature and evaluates the impact of TEE in a general surgical ICU.

Perioperative fluid therapy with tetrastarch and gelatin in cardiac surgery--a prospective sequential analysis*.

Objectives:To determine clinical outcomes of synthetic colloids, tetrastarch, and gelatin, used before and after cardiac surgery. Design:Prospective observational cohort study. Setting:Fifty-bed cardiac ICU. Patients:Six thousand four hundred seventy-eight consecutive patients with cardiopulmonary bypass surgery. Interventions:Fluid therapy in the operating room and on the ICU directed at preset hemodynamic goals: 1) hydroxyethyl starch (predominantly 6% hydroxyethyl starch 130/0.4) in 2004–2006, n = 2,137; 2) 4% gelatin in 2006–2008, n = 2,324; and 3) only crystalloids in 2008–2010, n = 2,017. Measurements and Main Results:Renal replacement therapy was more common during periods when patients received synthetic colloids compared to only crystalloids. Risk of renal replacement therapy was greater after hydroxyethyl starch (odds ratio, 2.29; 95% CI, 1.47–3.60) and gelatin (odds ratio, 2.75; 95% CI, 1.84–4.16; both p < 0.001) compared to crystalloid. Propensity score stratification confirmed greater use of renal replacement therapy in the hydroxyethyl starch and gelatin periods compared to the crystalloid period (odds ratio, 1.46 [1.08, 1.97]; p = 0.013 and odds ratio, 1.72 [1.33, 2.24]; p < 0.001, respectively). Time to vasopressor cessation, normalization of serum lactate, and mean arterial pressure did not differ among groups. Total fluid requirement was 163 mL/kg in the hydroxyethyl starch period, 207 mL/kg in the gelatin period, and 224 mL/kg in the crystalloid period. Fluid intake was higher in the crystalloid group only during the first 20 hours. Conclusions:In cardiac surgery patients, fluid therapy with perioperative administration of synthetic colloids carries a high risk of renal replacement therapy and is not more effective than treating with only crystalloids.

New Approaches for the Detection and Analysis of Electroencephalographic Burst-Suppression Patterns in Patients under Sedation

An automatic EEG pattern detection unit was developed and tested for the recognition of burst-suppression periods and for the separation of burst from suppression patterns. The median, standard deviation and the 95% edge frequency were computed from single channels of the EEG within a moving window and completed by the continuous computation of frequency band power via an adapted Hilbert resonance filter. These parameters were given to the inputs of two hierarchically arranged artificial neural networks (NNs). The output signals of NNs indicate the suppression and burst phases. The burst recognition was focused on the precise recognition of the burst onset. In subsequent processing steps the time course of percentages of burst patterns within their corresponding burst-suppression-phases was calculated and the time locations of burst onsets can be used to trigger an averaging for a burst-related analysis. The data for our investigations were derived from the routine EEG derivations of 12 patients with various neurosurgical diseases. A group-related training of the NNs was realized. For the group-related trained NNs EEG data for 6 patients were used for training and the data of 6 other patients for testing the classification performance of the pattern recognition units. Additionally, the reliability of the detection algorithm was tested with data of two patients with convulsive state, resistant to treatment, and burst-suppression like pattern EEG.

Increasing cardiac output by fluid loading: effects on indocyanine green plasma disappearance rate and splanchnic microcirculation

Background:  Sufficient cardiac pre‐load for maintaining adequate cardiac output is a major goal in the treatment of critically ill patients. We studied the effects of increasing cardiac output by fluid loading on the indocyanine green plasma disappearance rate (ICG‐PDR) and gastric mucosal regional CO2 tension (PRco2) as an indicator of splanchnic microcirculation.

Quantification of transient quadratic phase couplings within EEG burst patterns in sedated patients during electroencephalic burst-suppression period

The time dynamics of the quadratic phase coupling within burst patterns during electroencephalic burst-suppression has been quantified. It can be shown that a transient quadratic phase coupling (QPC) exists between the frequency ranges 0 to 2.5 and 3 to 7.5 Hz and between the frequency ranges 0 to 2.5 and 8 to 12 Hz. The QPC can be explained by an amplitude modulation, where the slow rhythm modulates the rhythmic activities with a higher frequency. By means of time-variant bicoherence analysis, a strong phase-locking between the modulating and the modulated component can be identified. The phase-locking is demonstrable within the first 250 ms after the burst onset and comes up to the maximum between 750 and 1250 ms. The effect is maintained over the whole first part of the burst (2 s) with a decreasing tendency after 1250 ms. All these effects cannot be found in the EEG before entering the burst suppression period (BSP). The transient coupling phenomena in the EEG bursts during BSP can be regarded as indicators for short-term interrelations between the underlying electrophysiologic processes.

Atropine test and circulatory arrest in the fossa posterior assessed by transcranial Doppler

Objective: To evaluate whether a negative atropine test (i. e., increase in heart rate of less than 3 % after intravenous administration of 3 mg atropine) correctly predicts circulatory arrest in the fossa posterior during craniocaudal herniation in patients with primary supratentorial lesions.¶Material and methods: Prospective, observational clinical study.¶Setting: Two surgical intensive care units in a university hospital.¶Patients: In 45 consecutive patients with suspected brain death, an atropine test (AT) and a transcranial Doppler sonography were performed simultaneously and, if necessary, repeatedly.¶Measurements and results: Forty-four patients fulfilled the typical criteria of a supratentorial and infratentorial circulatory arrest as the atropine test became negative. In one patient, who had undergone a decompressive craniectomy for uncontrollable intracranial pressure 4 h prior to the AT testing, we found a negative AT in the presence of an antegrade supratentorial and infratentorial flow.¶Conclusion: A negative atropine test indicates a circulatory arrest in the fossa posterior in patients with primary supratentorial lesions and craniocaudal herniation. In patients with brain-stem lesions, however, a negative atropine test does not unequivocally indicate a circulatory arrest.

Time-variant investigation of quadratic phase couplings caused by amplitude modulation in electroencephalic burst-suppression patterns.

Objective.Several studies suggest that parameters derivedfrom bispectral analysis of the EEG can be used to characterize specificcortical activation states represented by non linear interaction betweenbrain electrical oscillations. For example, it was shown that so-calledbispectral indices can be used to assess the depth of sedation. Themethods applied so far are based on interval-related procedures ofbispectral analysis. Consequently, the use of the resulting parametersfor on-line monitoring or investigations of signal properties duringtransition periods, e.g., when entering burst-suppression periods, isrestricted. The objective of this paper is to provide the methodologicalbasis for a time-continuous (on-line) investigation of quadratic phasecoupling induced by amplitude modulation. Methods.To accomplishthis aim an algorithm is presented which enables the analysis of thetemporal development in the degree of amplitude modulation (DAM), e.g.,during the transition to burst-suppression periods in patients withsevere neurological diseases. Results.It was found that theseperiods are associated with increasing DAM compared with the baselineconditions.

Catecholamine and Volume Therapy for Cardiac Surgery in Germany – Results from a Postal Survey

Background Management of cardiac surgery patients is a very standardized procedure in respective local institutions. Yet only very limited evidence exists concerning optimal indication, safety and efficacy of hemodynamic monitoring catecholamine and fluid therapy. Methods Between April and May 2013, all 81 German anaesthesia departments involved in cardiac surgery care were asked to participate in a questionnaire addressing the institutional specific current practice in hemodynamic monitoring, catecholamine and volume therapy. Results 51 (63%) questionnaires were completed and returned. All participating centers used basic hemodynamic monitoring (i.e. invasive arterial blood pressure and central venous pressure), supplemented by transesophageal echocardiography. Pulmonary arterial catheter and calibrated trend monitoring devices were also routinely available. In contrast, non-calibrated trend monitoring and esophageal doppler ultrasound devices were not commonly in use. Cerebral oximetry is increasingly emerging, but lacks clear indications. The majority of patients undergoing cardiac surgery, especially in university hospitals, required catecholamines during perioperative care, In case of low cardiac output syndrome, dobutamine (32%), epinephrine (30%) or phosphodiesterase inhibitors (8%) were first choice. In case of hypotension following vasoplegia, norepinephrine (96%) represented the most common catecholamine. 88% of the participating centers reported regular use of colloid fluids, with hydroxyethyl starches (HES) being first choice (64%). Conclusions Choice of hemodynamic monitoring is homogenous throughout German centers treating cardiac surgery patients. Norepinephrine is the first line catecholamine in cases of decrease in peripheral vascular resistance. However, catecholamine choice for low cardiac output syndrome varies considerably. HES was the primary colloid used for fluid resuscitation. After conduct of this survey, HES use was restricted by European regulatory authorities in critically ill patients and should only be considered as second-line fluid in surgical patients without renal impairment or severe coagulopathy. Large clinical studies addressing catecholamine and fluid therapy in cardiac surgery patients are lacking.

Positive end-expiratory pressure does not affect indocyanine green plasma disappearance rate or gastric mucosal perfusion after cardiac surgery

Background and objective: Positive end‐expiratory pressure (PEEP) may affect hepato‐splanchnic blood flow. We studied whether a PEEP of 10 mbar may negatively influence flow‐dependent liver function (indocyanine green plasma disappearance rate, ICG‐PDR) and splanchnic microcirculation as estimated by gastric mucosal PCO2 (PRCO2). Methods: In a randomized, controlled clinical study, we enrolled 28 patients after elective cardiac surgery using cardiopulmonary bypass. In 14 patients (13 male, 1 female; age 48–74, mean 63 ± 7 yr) we assessed ICG‐PDR and PRCO2 on intensive care unit admission with PEEP 5 mbar, after 2 h with PEEP of 10 mbar and again after 2 h at PEEP 5 mbar. Inspiratory peak pressure was adjusted to maintain normocapnia. Fourteen other patients (8 male, 6 female; age 46–86, mean 68 ± 11 yr) in whom PEEP was 5 mbar throughout served as controls. All patients underwent haemodynamic monitoring by measurement of central venous pressure, left atrial pressure and cardiac index using pulmonary artery thermodilution. Results: While doses of vasoactive drugs and cardiac filling pressures did not change significantly, cardiac index slightly increased in both groups. ICG‐PDR remained unchanged either within or between both groups (PEEP10 group: 24.0 ± 6.9, 22.0 ± 7.9 and 25.5 ± 7.7% min−1 vs. controls: 22.0 ± 7.5, 23.8 ± 8.4 and 21.4 ± 6.5% min−1) (P = 0.05). The difference between PRCO2 and end‐tidal PCO2 (PCO2‐gap) did not change significantly (PEEP10 group: 1.1 ± 0.9, 1.3 ± 0.7 and 1.3 ± 0.9 kPa vs. controls: 0.8 ± 0.5, 0.9 ± 0.5 and 0.9 ± 0.5 kPa). Conclusion: A PEEP of 10 mbar for 2 h does not compromise liver function and gastric mucosal perfusion in patients after cardiac surgery with maintained cardiac output.

TEE bei intracavaler Ausdehnung von Nierenzellkarzinomen Intraoperatives Management mit transösophagealer Echokardiographie

ZusammenfassungFragestellung. Stellenwert der transösophagealen Echokardiographie (TEE) für das intraoperative Management bei Patienten mit intrakavaler Ausdehnung von Nierenzellkarzinomen. Methodik. Retrospektive Auswertung des intraoperativen Einsatzes der TEE bei 4 konsekutiven Patienten. Ergebnisse. Die TEE mit multiplaner Sonde erlaubte in allen Fällen die Visualisierung des Kavazapfens, der genauen Ausdehnung sowie der Lagebeziehung zu Lebervenen und rechtem Vorhof, eine Überwachung zur Emboliedetektion und eine Beurteilung der kardialen Vorlast und Funktion. Schlussfolgerung. Die intraoperative TEE mit multiplaner Sonde stellt für das anästhesiologische wie operative Management bei Nierenzellkarzinomen mit intrakavaler Ausdehnung eine wesentliche Bereicherung dar.AbstractObjective. To evaluate the role of intraoperative real-time transesophageal echocardiography (TEE) for the anesthetic and surgical management of patients with renal cell carcinoma and vena cava extension. Methods. Retrospective analysis of the intraoperative application of TEE in a series of 4 patients. Results. Real-time TEE with a multiplane probe allowed visualization of inferior vena cava tumor extensions, accurate assessment of the distal extent of vena cava invasion into hepatic veins and right atrium, monitoring of embolism and evaluation of cardiac preload and function in all patients. Conclusion. Intraoperative TEE is a useful adjunct to the anesthetic and surgical management of patients with renal cell carcinoma and vena cava extension.