Introducing a free-breathing MRI method to assess peri-operative myocardial oxygenation and function: A volunteer cohort study.

BACKGROUND: Induction of general anaesthesia has many potential triggers for peri-operative myocardial ischaemia including the acute disturbance of blood gases that frequently follows alterations in breathing and ventilation patterns. Free-breathing oxygenation-sensitive cardiovascular magnetic resonance (OS-CMR) imaging may provide the opportunity to continuously quantify the impact of such triggers on myocardial oxygenation. OBJECTIVE: To investigate the impact of breathing patterns that simulate induction of general anaesthesia on myocardial oxygenation in awake healthy adults using continuous OS-CMR imaging. DESIGN: Prospective observational study. SETTING: Single-centre university hospital. Recruitment from August 2020 to January 2022. PARTICIPANTS: Thirty-two healthy volunteers younger than 45 years old were recruited. Data were analysed from n  = 29 (69% male individuals). INTERVENTION: Participants performed a simulated induction breathing manoeuvre consisting of 2.5 min paced breathing with a respiration rate of 14 breaths per minute, followed by 5 deep breaths, then apnoea for up to 60s inside a magnetic resonance imaging scanner (MRI). Cardiac images were acquired with the traditional OS-CMR sequence (OS bh-cine ), which requires apnoea for acquisition and with two free-breathing OS-CMR sequences: a high-resolution single-shot sequence (OS fb-ss ) and a real-time cine sequence (OS fb-rtcine ). MAIN OUTCOME MEASURES: Myocardial oxygenation response at the end of the paced breathing period and at the 30 s timepoint during the subsequent apnoea, reflecting the time of successful intubation in a clinical setting. RESULTS: The paced breathing followed by five deep breaths significantly reduced myocardial oxygenation, which was observed with all three techniques (OS bh-cine -6.0 ±â€Š2.6%, OS fb-ss -12.0 ±â€Š5.9%, OS fb-rtcine -5.4 ±â€Š7.0%, all P  < 0.05). The subsequent vasodilating stimulus of apnoea then significantly increased myocardial oxygenation (OS bh-cine 6.8 ±â€Š3.1%, OS fb-ss 8.4 ±â€Š5.6%, OS fb-rtcine 15.7 ±â€Š10.0%, all P  < 0.01). The free-breathing sequences were reproducible and were not inferior to the original sequence for any stage. CONCLUSION: Breathing manoeuvres simulating induction of general anaesthesia cause dynamic alterations of myocardial oxygenation in young volunteers, which can be quantified continuously with free-breathing OS-CMR. Introducing these new imaging techniques into peri-operative studies may throw new light into the mechanisms of peri-operative perturbations of myocardial tissue oxygenation and ischaemia. VISUAL ABSTRACT: http://links.lww.com/EJA/A922.

Hyperoxia-induced deterioration of diastolic function in anaesthetised patients with coronary artery disease - Randomised crossover trial.

Background: There are no current recommendations for oxygen titration in patients with stable coronary artery disease. This study investigates the effect of iatrogenic hyperoxia on cardiac function in patients with coronary artery disease undergoing general anaesthesia. Methods: Patients scheduled for elective coronary artery bypass graft surgery were prospectively recruited into this randomised crossover clinical trial. All patients were exposed to inspired oxygen fractions of 0.3 (normoxaemia) and 0.8 (hyperoxia) in randomised order. A transoesophageal echocardiographic imaging protocol was performed during each exposure. Primary analysis investigated changes in 3D peak strain, whereas secondary analyses investigated other systolic and diastolic responses. Results: There was no statistical difference in systolic function between normoxaemia and hyperoxia. However, the response in systolic function to hyperoxia was dependent on ventricular function at normoxaemia. Patients with a normoxaemic left ventricular (LV) global longitudinal strain (GLS) poorer than the derived cut-off (>-15.4%) improved with hyperoxia (P<0.01), whereas in patients with normoxaemic LV-GLS <-15.4%, LV-GLS worsened with transition to hyperoxia (P<0.01). The same was seen for right ventricular GLS with a cut-off at -24.1%. Diastolic function worsened during hyperoxia indicated by a significant increase of averaged E/e' (8.6 [2.6]. vs 8.2 [2.4], P=0.01) and E/A ratio (1.4 (0.4) vs 1.3 (0.4), P=0.01). Conclusions: Although the response of biventricular systolic variables is dependent on systolic function at normoxaemia, diastolic function consistently worsens under hyperoxia. In coronary artery disease, intraoperative strain analysis may offer guidance for oxygen titration. Clinical trial registration: NCT04424433.

Hemolysis After Transcatheter Mitral Valve Implantation Resolved by Valve Retensioning.

Transcatheter mitral valve implantation is an emerging technology for the treatment of inoperable or high-risk patients with symptomatic severe mitral regurgitation. Known technical issues are obstruction of the left ventricular outflow tract, paravalvular leakage, and hemolysis. We report a case of valve retensioning successfully resolving paravalvular leakage and hemolysis. (Level of Difficulty: Intermediate.).

Levosimendan and systemic vascular resistance in cardiac surgery patients: a systematic review and meta-analysis.

Levosimendan is a potent non-adrenergic inodilator agent. The net effect of hemodynamic changes may result in a hyperdynamic state with low systemic vascular resistance. We conducted a systematic review and meta-analysis assessing hemodynamics in cardiac surgery patients treated with levosimendan. English-language literature was searched systematically from 2006 until October 2018, including randomized controlled trials and case-matched or retrospective studies providing at least two sequentially measured hemodynamic variables in adult patients who underwent cardiac surgery with cardiopulmonary bypass and were treated with levosimendan in comparison to alternative drugs or devices. Cardiac index significantly increased in the levosimendan group by 0.74 (0.24 to 1.23) [standardized mean difference (95% CI); p = 0.003] from baseline to postoperative day (POD) 1, and by 0.75 (0.25 to 1.25; p = 0.003) from baseline to POD 7, when corrected for the standardized mean difference at baseline by a multivariate mixed effects meta-analysis model. With this correction for baseline differences, other hemodynamic variables including systemic vascular resistance did not significantly differ until POD 1 [-0.17 (-0.64 to 0.30), p = 0.48] and POD 7 [-0.13 (-0.61 to 0.34), p = 0.58] between the levosimendan and the comparator group. Levosimendan increases cardiac index in patients undergoing cardiac surgery. Although levosimendan has inodilator properties, this meta-analysis finds no clinical evidence that levosimendan produces vasopressor-resistant vasoplegic syndrome.

Effectiveness of nitric oxide during spontaneous breathing in experimental lung injury.

Inhaled nitric oxide (iNO) improves gas exchange in about 60% of patients with acute respiratory distress syndrome (ARDS). Recruitment of atelectatic lung areas may improve responsiveness and preservation of spontaneous breathing (SB) may cause recruitment. Accordingly, preservation of SB may improve effectiveness of iNO. To test this hypothesis, iNO was evaluated in experimental acute lung injury (ALI) during SB. In 24 pigs with ALI, effects of 10 ppm iNO were evaluated during controlled mechanical ventilation (CMV) and SB in random order. Preservation of SB was provided by 4 different modes: Unassisted SB was enabled by biphasic positive airway pressure (BIPAP), moderate inspiratory assist was provided by pressure support (PS) and volume-assured pressure support (VAPS), maximum assist was ensured by assist control (A/C). Statistical analysis did not reveal gas exchange improvements due to SB alone. Significant gas exchange improvements due to iNO were only achieved during unassisted SB with BIPAP (P <.05) but not during CMV or assisted SB. The authors conclude that effectiveness of iNO may be improved by unassisted SB during BIPAP but not by assisted SB. Thus combined iNO and unassisted SB is possibly most effective to improve gas exchange in severe hypoxemic ARDS.

Pumpless extracorporeal lung assist for protective mechanical ventilation in experimental lung injury.

OBJECTIVE: To test the hypothesis that ventilation with 3 mL/kg tidal volume combined with extracorporeal CO2 removal by arteriovenous interventional lung assist reduces ventilator-associated organ injury in experimental acute lung injury when compared with ventilation with 6 mL/kg tidal volume without interventional lung assist. DESIGN: Prospective, randomized, controlled trial. SETTING: A university research laboratory. SUBJECTS: A total of 14 pigs weighing 46 +/- 4 kg (mean +/- sd). INTERVENTIONS: Acute lung injury was induced by repeated lung lavages until Pao2 was <100 mm Hg, with Fio2 of 1.0 and positive end-expiratory pressure of 5 cm H2O, for 1 hr without additional lavages. Animals were randomized to an interventional group with a tidal volume of 3 mL/kg with interventional lung assist (n = 7) or to a control group with a tidal volume of 6 mL/kg without interventional lung assist (n = 7) for 24 hrs. Organ function in vivo was determined by laboratory analyses, including calculations of pulmonary ventilation/perfusion distribution. Histologic assessment of organ injury was performed post mortem after 24 hrs. MEASUREMENTS AND MAIN RESULTS: In both groups, gas exchange improved in the course of the study (p < .05). However, in contrast to control animals, animals with lower tidal volumes and interventional lung assist had severe ventilation/perfusion mismatch, as indicated by increased perfusion to lung areas with a low ventilation/perfusion ratio (p < .05). Other variables of organ function in vivo and results of histologic examination post mortem did not reveal any statistical difference between groups. CONCLUSIONS: Combined ventilation with lower tidal volumes and extracorporeal CO2 removal as compared with traditional low tidal volumes without extracorporeal CO2 removal is not associated with differences in organ injury. Obviously, ventilation with tidal volumes of <6 mL/kg may cause pulmonary de-recruitment when positive end-expiratory pressure is not adequately increased.

Pathogenesis, diagnosis and management of pneumorrhachis.

Pneumorrhachis (PR), the presence of intraspinal air, is an exceptional but eminent radiographic finding, accompanied by different aetiologies and possible pathways of air entry into the spinal canal. By reviewing the literature and analysing a personal case of traumatic cervical PR after head injury, we present current data regarding the pathoanatomy, clinical and radiological presentation, diagnosis and differential diagnosis and treatment modalities of patients with PR and associated pathologies to highlight this uncommon phenomenon and outline aetiology-based guidelines for the practical management of PR. Air within the spinal canal can be divided into primary and secondary PR, descriptively classified into extra- or intradural PR and aetiologically subsumed into iatrogenic, traumatic and nontraumatic PR. Intraspinal air is usually found isolated not only in the cervical, thoracic and, less frequently, the lumbosacral regions but can also be located in the entire spinal canal. PR is almost exceptional associated with further air distributions in the body. The pathogenesis and aetiologies of PR are multifold and can be a diagnostic challenge. The diagnostic procedure should include spinal CT, the imaging tool of choice. PR has to be differentiated from free intraspinal gas collections and the coexistence of air and gas within the spinal canal has to be considered differential diagnostically. PR usually represents an asymptomatic epiphenomenon but can also be symptomatic by itself as well as by its underlying pathology. The latter, although often severe, might be concealed and has to be examined carefully to enable adequate patient treatment. The management of PR has to be individualized and frequently requires a multidisciplinary regime.