Heiko A. Kaiser

Background: High-flow nasal oxygenation is increasingly used during sedation procedures and general anesthesia in apneic patients. Transcutaneous CO₂ (p_tcCO₂)-monitoring is used to monitor hypercapnia. This study investigated p_tcCO₂-monitoring during apneic oxygenation. Methods: We included 100 patients scheduled for elective surgery under general anesthesia in this secondary analysis of a randomized controlled trial. Before surgery, we collected p_tcCO₂ measured by TCM4 and TCM5 monitors and arterial blood gas (ABG) measurements every two minutes during 15 minutes of apnea. Bland-Altman plots analyzed agreement between measurement slopes; linear mixed models estimated the different measuring method effect, and outlined differences in slope and offset between transcutaneous and arterial CO₂ partial pressures. Results: Bland-Altman plots showed a bias in slope (95% confidence intervals) between ABG and TCM4-measurements of 0.05mmHg/min (-0.05 to 0.15), and limits of agreement were -0.88mmHg/min (-1.06 to -0.70) and 0.98mmHg/min (0.81 to 1.16). Bias between ABG and TCM5 was -0.14mmHg/min (-0.23 to -0.04), and limits of agreement were -0.98mmHg/min (-1.14 to -0.83) and 0.71mmHg/min (0.55 to 0.87). A linear mixed model (predicting the CO₂-values) showed an offset between arterial and transcutaneous measurements of TCM4 (-15.2mmHg, 95%CI: -16.3 to -14.2) and TCM5 (-19.1mmHg, -20.1 to -18.0). Differences between the two transcutaneous measurements were statistically significant. Conclusions: Substantial differences were found between the two transcutaneous measurement systems, and between them and ABG. Transcutaneous CO₂ monitoring cannot replace arterial CO₂-monitoring during apneic oxygenation. In clinical settings with rapidly changing CO₂-values, arterial blood gas measurements are needed to reliably assess the CO₂-partial pressure in blood. Trial registration: ClinicalTrials.gov (NCT03478774).

Purpose of review: Since the advent of the Fontan palliation, survival of patients with univentricular congenital heart disease has increased significantly. These patients will, however, ultimately develop heart failure requiring advanced therapies such as heart transplantation. As wait times are long, mechanical circulatory support (MCS) is an attractive therapy, both for bridge to transplantation and destination therapy in patients not suitable for transplantation. This review aims to summarize current thinking about how to determine which patients would benefit from a ventricular assist device (VAD), the optimal time for implantation and which device should be considered. Recent findings: VAD implantation in end-stage Fontan is still in its infancy; however, case reports and research interest have increased extensively in the past few years. Mortality is significantly higher than in noncongenital heart disease patients. Implantation in patients with primarily systolic dysfunction is indicated, whereas patients with increased transpulmonary gradient may not benefit from a single-VAD solution. When possible, implantation should occur prior to clinical decompensation with evidence of end-organ damage, as outcomes at this point are worse. Summary: Fontan patients demonstrating signs of heart failure should be evaluated early and often for feasibility and optimal timing of VAD implantation. The frequency of this procedure will likely increase significantly in the future.

Zusammenfassung: Das Elektroenzephalogramm (EEG) findet im klinischen Alltag der Anästhesie des deutschsprachigen Raumes zunehmend Anwendung. Bei über 90 % der Patienten ändert sich das frontale EEG als Reaktion auf die Gabe der gebräuchlichen Narkotika (Propofol und volatile Narkosegase) in typischer Weise. Eine adäquate Narkosetiefe und angemessene Konzentrationen der Anästhetika im Gehirn erzeugen meist frontale Oszillationen zwischen 8 und 12 Hz (α-Oszillationen) sowie langsame δ‑Wellen zwischen 0,5 und 4 Hz. Die frontale EEG-Ableitung eignet sich gut zur Vermeidung einer unzureichenden Narkosetiefe bzw. einer Überdosierung von Anästhetika. Im Folgenden werden die klinische Interpretation der wichtigsten EEG-Muster und ihr biophysikalischer Hintergrund erläutert. Ebenso werden wichtige Limitationen und „Fallstricke“ für den klinischen Alltag diskutiert, die der Anästhesist kennen sollte, um das EEG als zwar unvollständigen, aber klinisch äußerst wichtigen Parameter des Bewusstseinslevels zu nutzen.

Stroke due to hypoperfusion or emboli is a devastating adverse event of cardiac surgery, but early detection and treatment could protect patients from an unfavorable postoperative course. Hypoperfusion and emboli can be detected with transcranial Doppler of the middle cerebral artery (MCA). The measured blood flow velocity correlates with cerebral oxygenation determined clinically by near-infrared spectroscopy (NIRS) of the frontal cortex. We tested the potential advantage of a spatially extended NIRS in detecting critical events in three cardiac surgery patients with a whole-head fiber holder of the FOIRE-3000 continuous-wave NIRS system. Principle components analysis was performed to differentiate between global and localized hypoperfusion or ischemic territories of the middle and anterior cerebral arteries. In one patient, we detected a critical hypoperfusion of the right MCA, which was not apparent in the frontal channels but was accompanied by intra- and postoperative neurological correlates of ischemia. We conclude that spatially extended NIRS of temporal and parietal vascular territories could improve the detection of critically low cerebral perfusion. Even in severe hemispheric stroke, NIRS of the frontal lobe may remain normal because the anterior cerebral artery can be supplied by the contralateral side directly or via the anterior communicating artery.

BACKGROUND: The aim of the study was to determine if training in transesophageal echocardiography (TEE) using a TEE simulator improves the ability of novice operators to perform and interpret a focused critical care TEE. METHODS: In this prospective, randomized, controlled study with blinded outcome assessment, 44 intensive care unit trainees were randomly assigned to a control group receiving 4 hours of lecture-based training only, or an intervention group which was additionally trained for 4 hours using a TEE simulator. After the training intervention, each participant performed 2 TEEs in intensive care unit patients which were evaluated by blinded assessors. The imaging quality of TEEs was measured using a predefined examination quality score ranging from 0 to 100 points. The correct quantification of pathologies and the interpretation of the TEEs were evaluated by blinded assessors using focused and comprehensive expert TEEs as comparators. RESULTS: A total of 114 TEEs were assessed. The mean examination quality score was 55.9 (95% confidence interval [CI], 50.3–61.5) for TEEs of the control group, 75.6 (95% CI, 70.1–81.0) for TEEs of the intervention group, and 88.5 (95% CI, 79.3–97.7) for TEEs in the expert group. The multiple comparisons revealed significant differences between all groups (19.7 [95% CI, 12.8–26.6], P < .001 for intervention versus control; 32.6 [95% CI, 23.0–42.3], P < .001 for expert versus control; 12.9 [95% CI, 3.4–22.5], P = .008 for expert versus intervention). Substantial agreement of the quantification and interpretation ratings of basic TEEs by the intervention (86.7% for quantification and 97.1% for interpretation) or expert group (93.2% for quantification and 98.4% for interpretation) with blinded assessors was detected. The control groups TEEs agreed less (75.6% for quantification and 91.8% for interpretation). CONCLUSIONS: Simulation-based TEE training improves the ability of novice operators to perform a focused critical care TEE in comparison to lecture-based education only. After 8 hours of simulator and lecture-based training, the majority of TEEs of novices are of sufficient quality for clinical use. Furthermore, a substantial skill level in correct quantification and interpretation of imaging is achieved.