Positive end-expiratory pressure increases the right-to-left shunt in mechanically ventilated patients with patent foramen ovale

Malposition of a Femoral Tunneled Dialysis Catheter through a Patent Foramen Ovale

Patent foramen ovale (PFO) is a common congenital abnormality of high prevalence in adults. Its clinical significance is magnified in a right-to-left shunt, where paradoxical embolism can have catastrophic outcomes involving the brain, heart, mesenteric circulation, or extremities. Right-to-left shunting through a PFO is caused by increased right atrial pressure, as seen in the setting of pulmonary artery hypertension or pulmonary embolism. This case highlights the relevance of central venous catheter placement in the setting of a PFO. While the patient did not experience clinical sequelae from line placement, she was at high risk for paradoxical embolus. Recognizing the possibility of a PFO during central venous catheter placement, especially in the setting of increased right pressures, should be a consideration of all interventional radiologists.

Agitated Saline Contrast Injection in Patients with Severe Hypoxemia

The use of agitated saline contrast (ASC) during echocardiographic examinations is a well-established practice, most commonly performed to identify atrial septal abnormalities in the context of stroke. In the intensive care unit, this technique may be employed to identify anatomic right-to-left shunts (either intracardiac or transpulmonary) that may be contributing to hypoxemic respiratory failure. This narrative review will describe the technique of ASC injection, summarize clinical scenarios where it may be useful, and review the strengths and limitations of the tool.

Risk factors and complications associated with intra-operative or post-operative identification of a PFO in cardiac surgery patients: A cohort study

Introduction

It is unknown whether patent foramen ovale (PFO) reopening in the peri-operative setting of cardiac surgery affects the risk for stroke and post-operative outcomes.

Methods

We performed a single-center, retrospective study based on a prospectively collected database in a tertiary cardiac surgery center. Using logistic regression, we assessed risk factors of PFO finding around surgery and subsequent clinical complications.

Results

Between January 2007 and July 2019, 11034 patients who underwent cardiac surgery in our center were included. A total of 233 patients (2.1%) presented a finding of PFO including 138 per-operative disclosures and 95 post-operative finding for hypoxemia. In the whole cohort, the mean age was 68.4 ± 11.5 years including 73.9% of men. Post-operative PFO finding was associated with more ischemic strokes compared with per-operative finding and control group [7(7.4%) vs. 3(2.2%) vs. 236(2.2), respectively; p = 0.003]. Moreover, patients with post-operative PFO reopening experienced a higher rate of pneumonia, reintubation, and longer length of stay in the ICU. Post-operative reopening of PFO, but not per-operative finding, was independently associated with ischemic strokes {adjusted odds-ratio = 3.5, 95% confidence interval (CI) [1.6-7.8]; p = 0.002}. Other variables associated with stroke incidence included age, mitral valve surgery, and ascending aorta surgery. Per- or post-operative PFO closure was associated with reduced adverse respiratory outcomes and a trend of the lower cerebral ischemic event.

Conclusion

Patent foramen ovale finding incidence in peri-operative cardiac surgery care was rare (2%) but post-operative finding of PFO was associated with a increased risk of ischemic strokes, worsened respiratory outcomes, and prolonged hospitalization.

[Thalamic infarction following paradoxical embolism during total hip replacement : Case report and pathophysiological considerations]

Because of a painful right-sided coxarthrosis a 57-year-old female patient underwent a cementless total arthroplasty under general anesthesia. Except for Asperger's syndrome and an occlusion of a vein in her left eye she stated no other diseases or complaints, especially no cardiac problems. Postoperatively she developed neurological symptoms of left-sided hemiparesis and hemihypesthesia. A cranial computer tomography was performed and a right-sided infarction of the thalamic region was found. A patent foramen ovale (PFO) and atrial septal aneurysm were detected 5 days later. The incidence of a PFO is given as 25% of the population. A paradoxical air embolism in the presence of a PFO is a feared complication in neurosurgical interventions in a semi-sitting or sitting position. Corpuscular emboli, such as bone, cement, fat or wound debris may be the reason for paradoxical embolisms in combination especially with partial or total hip replacement. The kind of embolism in the case described could not be clarified. Deep vein thrombosis or cardiac arrhythmia could be excluded. Therefore, it can be considered most likely that the operation site was the source of the embolism. The trigger for a paradoxical embolism is a reversal of the pressure difference between the right and left atria: normally the left atrial pressure exceeds the right atrial pressure by ca. 2-4 mm Hg, resulting possibly in a small clinically irrelevant left-to-right shunt. If the pulmonary arterial circulation is compromised and pulmonary vascular resistance increases, the pressure gradient between the left and right atria reverses and a right-to-left shunt can occur causing a paradoxical embolism. Positive end-expiratory pressure (PEEP) ventilation during anesthesia could be an important reason for a shunt reversal between the right and left atria and therefore favoring a paradoxical embolism but the pathophysiological role of PEEP has not yet been finally clarified.

Optimal Positive End Expiratory Pressure Levels in Ventilated Patients Without Acute Respiratory Distress Syndrome: A Bayesian Network Meta-Analysis and Systematic Review of Randomized Controlled Trials

Background: To find the optimal positive end expiratory pressure (PEEP) in mechanical ventilated patients without Acute Respiratory Distress Syndrome (ARDS), we conducted a Bayesian network meta-analysis and systematic review of randomized controlled trials (RCTs) comparing different level of PEEP based on a novel classification of PEEP level: ZEEP group (PEEP = 0 cm H2O); lower PEEP group (PEEP = 1–6 cm H2O); intermediate PEEP group (PEEP = 7–10 cm H2O); higher PEEP group (PEEP > 10 cm H2O).

Result: Twenty eight eligible studies with 2,712 patients were included. There were no significant differences in the duration of mechanical ventilation between higher and intermediate PEEP (MD: 0.020, 95% CI: −0.14, 0.28), higher and lower PEEP (MD: −0.010, 95% CI: −0.23, 0.22), higher PEEP and ZEEP (MD: 0.010, 95% CI: −0.40, 0.22), intermediate and lower PEEP (MD: −0.040, 95% CI: −0.18, 0.040), intermediate PEEP and ZEEP (MD: −0.010, 95% CI: −0.42, 0.10), lower PEEP and ZEEP (MD: 0.020, 95% CI: −0.32, 0.13), respectively. Higher PEEP was associated with significantly higher PaO2/FiO2 ratio(PFR) when compared to ZEEP (MD: 73.24, 95% CI: 11.03, 130.7), and higher incidence of pneumothorax when compared to intermediate PEEP, lower PEEP and ZEEP (OR: 2.91e + 12, 95% CI: 40.3, 1.76e + 39; OR: 1.85e + 12, 95% CI: 29.2, 1.18e + 39; and OR: 1.44e + 12, 95% CI: 16.9, 8.70e + 38, respectively). There was no association between PEEP levels and other secondary outcomes.

Conclusion: We identified higher PEEP was associated with significantly higher PFR and higher incidence of pneumothorax. Nonetheless, in terms of other outcomes, no significant differences were detected among four levels of PEEP.

Systematic Review Registration: The study had registered on an international prospective register of systematic reviews, PROSPERO, on 09 April 2021, identifier: [CRD42021241745].

A 70-Year-Old Woman With Refractory Hypoxemia

CASE PRESENTATION

A 70-year-old woman was transferred to our ED from an outside ED for hypoxemia. Three weeks earlier, an inpatient evaluation for syncope revealed a right intraventricular filling defect, multiple pulmonary nodules, pulmonary emboli, and a left breast mass. She underwent breast biopsy, was started on rivaroxaban, and was discharged with outpatient follow-up. She experienced progressively worsening dyspnea, prompting a return to the outside ED, where she was found to be severely hypoxemic and was intubated. Her medical history included diabetes, hypertension, hyperlipidemia, COPD, hypothyroidism, diastolic heart failure, and a 40+ pack-year smoking history.

Higher versus lower positive end-expiratory pressure in patients without acute respiratory distress syndrome: a meta-analysis of randomized controlled trials

Background

We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) to assess the association of higher positive end-expiratory pressure (PEEP), as opposed to lower PEEP, with hospital mortality in adult intensive care unit (ICU) patients undergoing invasive mechanical ventilation for reasons other than acute respiratory distress syndrome (ARDS).

Methods

We performed an electronic search of MEDLINE, EMBASE, Scopus, Cochrane Central Register of Controlled Trials, CINAHL, and Web of Science from inception until June 16, 2021 with no language restrictions. In addition, a research-in-progress database and grey literature were searched.

Results

We identified 22 RCTs (2225 patients) comparing higher PEEP (1007 patients) with lower PEEP (991 patients). No statistically significant association between higher PEEP and hospital mortality was observed (risk ratio 1.02, 95% confidence interval 0.89–1.16; I² = 0%, p = 0.62; low certainty of evidence). Among secondary outcomes, higher PEEP was associated with better oxygenation, higher respiratory system compliance, and lower risk of hypoxemia and ARDS occurrence. Furthermore, barotrauma, hypotension, duration of ventilation, lengths of stay, and ICU mortality were similar between the two groups.

Conclusions

In our meta-analysis of RCTs, higher PEEP, compared with lower PEEP, was not associated with mortality in patients without ARDS receiving invasive mechanical ventilation. Further large high-quality RCTs are required to confirm these findings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03669-4.

Effect of different levels of PEEP on mortality in ICU patients without acute respiratory distress syndrome: systematic review and meta-analysis with trial sequential analysis

OBJECTIVE

To determine whether higher positive end- expiratory pressure (PEEP) could provide a survival advantage for patients without acute respiratory distress syndrome (ARDS) compared with lower PEEP.

METHODS

Eligible studies were identified through searches of Embase, Cochrane Library, Web of Science, Medline, and Wanfang database from inception up to 1 June 2021. Trial sequential analysis (TSA) was used in this meta-analysis.

DATA SYNTHESIS

Twenty-seven randomized controlled trials (RCTs) were identified for further evaluation. Higher and lower PEEP arms included 1330 patients and 1650 patients, respectively. A mean level of 9.6±3.4 cmH₂O was applied in the higher PEEP groups and 1.9±2.6 cmH₂O was used in the lower PEEP groups. Higher PEEP, compared with lower PEEP, was not associated with reduction of all-cause mortality (RR 1.03; 95% CI 0.91-1.18; P =0.627), and 28-day mortality (RR 1.07 ; 95% CI 0.92-1.24; P =0.365). In terms of risk of ARDS (RR 0.43; 95% CI 0.24-0.78; P =0.005), duration of intensive care unit (MD -1.04; 95%CI-1.36 to -0.73; P < 0.00001), and oxygenation (MD 40.30; 95%CI 0.94 to 79.65; P = 0.045), higher PEEP was superior to lower PEEP. Besides, the pooled analysis showed no significant differences between groups both in the duration of mechanical ventilation (MD 0.00; 95%CI-0.13 to 0.13; P = 0.996) and hospital stay (MD -0.66; 95%CI-1.94 to 0.61; P = 0.309). More importantly, lower PEEP did not increase the risk of pneumonia, atelectasis, barotrauma, hypoxemia, or hypotension among patients compared with higher PEEP. The TSA analysis showed that the results of all-cause mortality and 28-day mortality might be false-negative results.

CONCLUSIONS

Our results suggest that a lower PEEP ventilation strategy was non-inferior to a higher PEEP ventilation strategy in ICU patients without ARDS, with no increased risk of all-cause mortality and 28-day mortality. Further high-quality RCTs should be performed to confirm these findings.

Increased Risk of Perioperative Ischemic Stroke in Patients Who Undergo Noncardiac Surgery with Preexisting Atrial Septal Defect or Patent Foramen Ovale

OBJECTIVES

To evaluate whether a preoperative diagnosis of atrial septal defect (ASD) or patent foramen ovale (PFO) is associated with perioperative stroke in noncardiac surgery and their outcomes.

DESIGN

Retrospective cohort analysis.

SETTING

United States hospitals.

PARTICIPANTS

Adults patients (≥18 years old) who underwent major noncardiac surgery from 2010 to 2015 were identified using the Healthcare Cost and Utilization Project's National Readmission Database.

INTERVENTIONS

Preoperative diagnosis of ASD or patent foramen ovale.

MEASUREMENTS AND MAIN RESULTS

Among the 19,659,161 hospitalizations for major noncardiac surgery analyzed, 12,248 (0.06%) had a preoperative diagnosis of ASD/PFO. Perioperative ischemic stroke occurred in 723 (5.9%) of patients with ASD/PFO and 373,291 (0.02%) of those without ASD/PFO (adjusted odds ratio [aOR], 16.7; 95% confidence interval [CI]: 13.9-20.0). Amongst the different types of noncardiac surgeries, obstetric, endocrine, and skin and burn surgery were associated with higher risk of stroke in patients with pre-existing ASD/PFO. Moreover, patients with ASD/PFO also had an increased in-hospital mortality (aOR, 4.6, 95% CI: 3.6-6.0), 30-day readmission (aOR, 1.2, 95% CI: 1.04-1.38), and 30-day stroke (aOR, 7.2, 95% CI: 3.1-16.6). After adjusting for atrial fibrillation, ischemic stroke remained significantly high in the ASD/PFO group (aOR: 23.7, 95%CI 19.4-28.9), as well as in-hospital mortality (aOR: 5.6, 95% CI 4.1-7.7), 30-day readmission (aOR: 1.19, 95%CI 1.0-1.4), and 30-day stroke (aOR: 9.3, 95% CI 3.7-23.6).

CONCLUSIONS

Among adult patients undergoing major noncardiac surgery, pre-existing ASD/PFO is associated with increased risk of perioperative ischemic stroke, in-hospital mortality, 30-day stroke, and 30-day readmission after surgery.

RELAx - REstricted versus Liberal positive end-expiratory pressure in patients without ARDS: protocol for a randomized controlled trial

BACKGROUND

Evidence for benefit of high positive end-expiratory pressure (PEEP) is largely lacking for invasively ventilated, critically ill patients with uninjured lungs. We hypothesize that ventilation with low PEEP is noninferior to ventilation with high PEEP with regard to the number of ventilator-free days and being alive at day 28 in this population.  METHODS/DESIGN: The "REstricted versus Liberal positive end-expiratory pressure in patients without ARDS" trial (RELAx) is a national, multicenter, randomized controlled, noninferiority trial in adult intensive care unit (ICU) patients with uninjured lungs who are expected not to be extubated within 24 h. RELAx will run in 13 ICUs in the Netherlands to enroll 980 patients under invasive ventilation. In all patients, low tidal volumes are used. Patients assigned to ventilation with low PEEP will receive the lowest possible PEEP between 0 and 5 cm H2O, while patients assigned to ventilation with high PEEP will receive PEEP of 8 cm H2O. The primary endpoint is the number of ventilator-free days and being alive at day 28, a composite endpoint for liberation from the ventilator and mortality until day 28, with a noninferiority margin for a difference between groups of 0.5 days. Secondary endpoints are length of stay (LOS), mortality, and occurrence of pulmonary complications, including severe hypoxemia, major atelectasis, need for rescue therapies, pneumonia, pneumothorax, and development of acute respiratory distress syndrome (ARDS). Hemodynamic support and sedation needs will be collected and compared.

DISCUSSION

RELAx will be the first sufficiently sized randomized controlled trial in invasively ventilated, critically ill patients with uninjured lungs using a clinically relevant and objective endpoint to determine whether invasive, low-tidal-volume ventilation with low PEEP is noninferior to ventilation with high PEEP.

TRIAL REGISTRATION

ClinicalTrials.gov , ID: NCT03167580 . Registered on 23 May 2017.

Serpentine thrombus in the heart: a rare case of trapped thrombus in patent foramen ovale

A 77-year-old Caucasian woman with recent abdominal surgery was diagnosed with multiple paradoxical systemic emboli in the mesenteric and renal circulation. Diagnosis was made by direct visualisation of a serpentine thrombus traversing both atria through patent foramen ovale (PFO) by transesophageal echocardiogram (TEE). Concomitantly, the patient was found to have deep venous thrombosis and pulmonary embolism. A decision was made to pursue cardiothoracic surgery preceded by inferior vena cava filter placement. She was started on intravenous anticoagulation. Repeat TEE was negative for thrombus and the patient did not present any new clinical signs of embolisation by this time. Consequently, the treatment plan was modified and the patient received oral systemic anticoagulation followed by PFO closure with the use of St. Jude Amplatzer Cribriform septal occluder device. During the outpatient follow-up the patient was asymptomatic and there was no significant flow through the device on transthoracic echocardiogram.

Paradoxical worsening of hypoxemia in a patient treated by noninvasive positive pressure ventilation for obesity hypoventilation syndrome with concomitant obstructive sleep apnea: a case report

BACKGROUND

Noninvasive positive pressure ventilation is frequently prescribed to obese patients with obstructive sleep apnea syndrome and obesity hypoventilation syndrome. However, mechanical ventilation with a positive end-expiratory pressure can induce or worsen a right-to-left shunt through a patent foramen ovale associated with systemic hypoxemia. Thus, in obese patients treated with noninvasive positive pressure ventilation, a paradoxical worsening of hypoxemia may reveal the existence of a patent foramen ovale.

CASE PRESENTATION

A 50-year-old African woman was referred to our sleep center for severe obstructive sleep apnea syndrome and obesity hypoventilation syndrome. Because she had alveolar hypoventilation and had failed previous obstructive sleep apnea syndrome therapy, noninvasive positive pressure ventilation was started. In May 2015, she had a normal residual apnea/hypopnea index calculated by the ventilator software with no hypoventilation. Six months later, severe hypoxemia without hypercapnia was noted. Contrast transthoracic echocardiography showed right-to-left shunt through a patent foramen ovale. This finding prompted a decrease in expiratory and inspiratory positive airway pressures, after which the ventilator software recorded a normal residual apnea/hypopnea index and the blood gas values improved.

CONCLUSION

Noninvasive positive pressure ventilation therapy for combined obstructive sleep apnea syndrome and obesity hypoventilation syndrome must be monitored by arterial blood gas measurements, both to reassess the hypercapnia and to look for worsening hypoxemia due to a patent foramen ovale.

A Case of Shunting Postoperative Patent Foramen Ovale Under Mechanical Ventilation Controlled by Different Ventilator Settings

A 56-year old male with ischemic heart disease and an unremarkable preoperative echocardiogram underwent surgical coronary revascularization. An intraoperative post pump trans-esophageal echocardiogram (TOE) performed while the patient was being ventilated at a positive end expiratory pressure (PEEP) of 8 cm H2O demonstrated a right to left interatrial shunt across a patent foramen ovale (PFO). Whereas oxygen saturation was normal, a reduction of the PEEP to 3 cm H2O led to the complete resolution of the shunt with no change in arterial blood gases. Attempts to increase the PEEP level above 3 mmHg resulted in recurrence of the interatrial shunt. The remaining of the TEE was unremarkable. Mechanical ventilation, particularly with PEEP, causes an increase in intrathoracic pressure. The resulting rise in right atrial pressure, mostly during inspiration, may unveil and pop open an unrecognized PFO, thus provoking a right to left shunt across a seemingly intact interatrial septum. This phenomenon increases the risk of paradoxical embolism and can lead to hypoxemia. The immediate management would be to adjust the ventilatory settings to a lower PEEP level. A routine search for a PFO should be performed in ventilated patients who undergo a TEE.

Intracardiac Right-to-Left Shunt Impeding Liberation From Veno-Venous Extracorporeal Membrane Oxygenation: Two Case Studies

OBJECTIVES

Veno-venous extracorporeal membrane oxygenation is an increasingly used form of advanced respiratory support, but its effects on the physiology of the right heart are incompletely understood. We seek to illustrate the impact of veno-venous extracorporeal membrane oxygenation return blood flow upon the right atrium by considering the physiologic effects during interatrial shunting.

PATIENTS

Two veno-venous extracorporeal membrane oxygenation patients in whom an extracorporeal membrane oxygenation induced right-to-left interatrial shunt appears to have created a barrier to liberation from extracorporeal support.

CONCLUSIONS

Veno-venous extracorporeal membrane oxygenation return flow generates a high-pressure jet that has potential to exert focal pressure upon the intra-atrial septum. In patients with potential for interatrial flow, this may lead to a right-to-left shunt, which becomes physiologically apparent only when sweep gas flow is ceased.

Patent foramen ovale diagnosis: The importance of provocative maneuvers

Patent foramen ovale (PFO) is a frequent congenital anomaly, but massive right-to-left shunt (RTLS) is normally prevented by higher pressures in left heart chambers. However, mechanical ventilation with positive end-expiratory pressure (PEEP) can significantly increase right atrial pressure, accentuating the RTLS, mainly after major cardiothoracic surgery. We report a patient admitted to the intensive care unit after cardiac surgery. Pre- and intraoperative transesophageal echocardiography only described an aneurysmal interatrial septum with no shunt. However, high-PEEP ventilation induced a paradoxical response with life-threatening hypoxemia, triggering further echocardiographic evaluation, revealing massive RTLS across a stretch PFO. Provocative maneuvers (Valsalva/PEEP) significantly increase echocardiographic sensitivity, unmasking silent PFO. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 45:58-61, 2017.

Associations between positive end-expiratory pressure and outcome of patients without ARDS at onset of ventilation: a systematic review and meta-analysis of randomized controlled trials

Background

The aim of this investigation was to compare ventilation at different levels of positive end-expiratory pressure (PEEP) with regard to clinical important outcomes of intensive care unit (ICU) patients without acute respiratory distress syndrome (ARDS) at onset of ventilation.

Methods

Meta-analysis of randomized controlled trials (RCTs) comparing a lower level of PEEP with a higher level of PEEP was performed. The primary outcome was in-hospital mortality.

Results

Twenty-one RCTs (1393 patients) were eligible. PEEP ranged from 0 to 10 cmH₂O and from 5 to 30 cmH₂O in the lower PEEP and the higher PEEP arms of included RCTs, respectively. In-hospital mortality was not different between the two PEEP arms in seven RCTs (risk ratio [RR] 0.87; 95% confidence interval [CI] 0.62–1.21; I² = 26%, low quality of evidence [QoE]), as was duration of mechanical ventilation in three RCTs (standardized mean difference [SMD] 0.68; 95% CI −0.24 to 1.61; I² = 82%, very low QoE). PaO₂/FiO₂ was higher in the higher PEEP arms in five RCTs (SMD 0.72; 95% CI 0.10–1.35; I² = 86%, very low QoE). Development of ARDS and the occurrence of hypoxemia (2 RCTs) were lower in the higher PEEP arms in four RCTs and two RCTs, respectively (RR 0.43; 95% CI 0.21–0.91; I² = 56%, low QoE; RR 0.42; 95%–CI 0.19–0.92; I² = 19%, low QoE). There was no association between the level of PEEP and any hemodynamic parameter (four RCTs).

Conclusion

Ventilation with higher levels of PEEP in ICU patients without ARDS at onset of ventilation was not associated with lower in-hospital mortality or shorter duration of ventilation, but with a lower incidence of ARDS and hypoxemia, as well as higher PaO₂/FiO₂. These findings should be interpreted with caution, as heterogeneity was moderate to high, the QoE was low to very low, and the available studies prevented us from addressing the effects of moderate levels of PEEP.

Electronic supplementary material

The online version of this article (doi:10.1186/s13613-016-0208-7) contains supplementary material, which is available to authorized users.

Diagnostic Bedside Ultrasonography for Acute Respiratory Failure and Severe Hypoxemia in the Medical Intensive Care Unit: Basics and Comprehensive Approaches

Bedside goal-directed ultrasound is a powerful tool for rapid differential diagnosis and monitoring of cardiopulmonary disease in the critically ill patient population. The bedside intensivist is in a unique position to integrate ultrasound findings with the overall clinical situation. Medically critically ill patients who require urgent bedside diagnostic assessment fall into 2 categories: (1) acute respiratory failure and (2) hemodynamic derangements. The first portion of this review outlines the diagnostic role of bedside ultrasound in the medically critically ill patient population for the diagnosis and treatment of acute respiratory failure, acute respiratory distress, and severe hypoxemia. The second portion will focus on the diagnostic role of ultrasound for the evaluation and treatment of shock states, as well as describe protocolized approaches for evaluation of shock during cardiopulmonary resuscitation. Different respiratory system pathologies that result in acute respiratory failure (such as increased interstitial fluid, alveolar consolidation, pleural effusion) cause characteristic ultrasonographic findings; diaphragmatic assessment may also add information. Intracardiac shunting can cause severe hypoxemia. Protocolized approaches for the evaluation of patients with acute respiratory failure or distress are discussed.

Worsening Hypoxemia in the Face of Increasing PEEP: A Case of Large Pulmonary Embolism in the Setting of Intracardiac Shunt

Patient: Male, 40

Final Diagnosis: Patent foramen ovale

Symptoms: Dyspnea exertional • hemoptysis • shortness of breath

Medication: —

Clinical Procedure: Airway pressure release ventilation

Specialty: Critical Care Medicine

Unusual cause of hypoxemia after automatic implantable cardioverter-defibrillatorleads extraction

The indication of pacemaker/AICD removal are numerous. Serious complication can occur during their removal, severe tricuspid regurgitation is one of the complication. The occurrence of PFO is not uncommon among adult population. Shunting across PFO in most circumstance is negligible, but in some necessitates closure due to hypoxemia. We report a case of 62 year old man, while undergoing AICD removal, had an emergency sternotomy for cardiac tamponade. Postoperatively, he experienced profound hypoxemia refractory to oxygen therapy. Transthoracic Echocardiogram was performed to rule out intracardiac shunts at an early stage, but it was difficult to obtain an good imaging windows poststernotomy. A small pulmonary emboli was noted on CTPA, but was not sufficient to account for the level of hypoxemia and did not resolve with anticoagulation. Transesophageal echocardiogram showed flail septal tricuspid valve with severe TR and bidirectional shunt through large PFO. Patient was posted for surgery, tricuspid valve was replaced and PFO surgically closed. Subsequently, patient recovered well ad was discharged to home. Cause of hypoxemia might be due to respiratory or cardiac dysfunction. But for hypoxemia refractory to oxygen therapy, transoesophageal echocardiogram should be always considered and performed early as an diagnostic tool in post cardiac surgical patients.

Acute respiratory distress syndrome (ARDS)-associated acute cor pulmonale and patent foramen ovale: a multicenter noninvasive hemodynamic study

Introduction

Acute cor pulmonale (ACP) and patent foramen ovale (PFO) remain common in patients under protective ventilation for acute respiratory distress syndrome (ARDS). We sought to describe the hemodynamic profile associated with either ACP or PFO, or both, during the early course of moderate-to-severe ARDS using echocardiography.

Methods

In this 32-month prospective multicenter study, 195 patients with moderate-to-severe ARDS were assessed using echocardiography during the first 48 h of admission (age: 56 (SD: 15) years; Simplified Acute Physiology Score: 46 (17); PaO₂/FiO₂: 115 (39); V_T: 6.5 (1.7) mL/kg; PEEP: 11 (3) cmH₂O; driving pressure: 15 (5) cmH₂O). ACP was defined by the association of right ventricular (RV) dilatation and systolic paradoxical ventricular septal motion. PFO was detected during a contrast study using agitated saline in the transesophageal bicaval view.

Results

ACP was present in 36 patients, PFO in 21 patients, both PFO and ACP in 8 patients and the 130 remaining patients had neither PFO nor ACP. Patients with ACP exhibited a restricted left ventricle (LV) secondary to RV dilatation and had concomitant RV dysfunction, irrespective of associated PFO, but preserved LV systolic function. Despite elevated systolic pulmonary artery pressure (sPAP), patients with isolated PFO had a normal RV systolic function. sPAP and PaCO₂ levels were significantly correlated.

Conclusions

In patients under protective mechanical ventilation with moderate-to-severe ARDS, ACP was associated with LV restriction and RV failure, whether PFO was present or not. Despite elevated sPAP, PFO shunting was associated with preserved RV systolic function.

[Practical conduct for patients with a lonely hypoxemia at rest or during exercise]

INTRODUCTION

Hypoxemia is a decrease in blood oxygen partial pressure. This work aims at presenting a practical conduct for patients with a lonely hypoxemia at rest or during exercise, defined by the absence of dyspnea at rest, obvious clinical or radiographic abnormality.

STATE OF THE ART

Diagnostic tools available to the clinician are clinical examination, CT scan, echocardiography, hyperoxia test, trans cranial ultrasound and lung scintigraphy. This work proposes a practical diagnostic approach, with a main role of chest CT.

PERSPECTIVES

Work is underway to determine more precisely the place of echocardiography for the diagnosis of intra or extra cardiac shunts.

CONCLUSIONS

The finding of a lonely hypoxemia requires careful diagnostic approach to quickly rule out potentially serious causes and not to disregard the rare causes.

Nitric oxide therapy for post-laparoscopic surgery associated patent foramen ovale: incidence, mechanisms, diagnosis and therapy

OBJECTIVE

Postoperative hypoxemia is a common clinical challenge. The diagnosis of an underlying cause of hypoxemia may not immediately be apparent. Clinically silent and non-functional intracardiac shunt may become apparent and pose significant management problems in the postoperative period.

DATA SOURCE

We describe a case where clinically significant hypoxemia resulted from a patent foramen ovale (PFO) after laparoscopic surgery due to changes in the intra-abdominal and intrathoracic pressures.

CONCLUSION

This condition was effectively diagnosed by bedside echocardiography, and was effectively treated with nitric oxide.

Temporal evolution of acute respiratory distress syndrome definitions

OBJECTIVE

to review the evolution of acute respiratory distress syndrome (ARDS) definitions and present the current definition for the syndrome.

DATA SOURCE

a literature review and selection of the most relevant articles on ARDS definitions was performed using the MEDLINE®/PubMed® Resource Guide database (last ten years), in addition to including the most important articles (classic articles) that described the disease evolution.

DATA SYNTHESIS

the review included the following subjects: introduction; importance of definition; description of the first diagnostic criterion and subsequently used definitions, such as acute lung injury score; definition by the American-European Consensus Conference, and its limitations; description of the definition by Delphi, and its problems; accuracy of the aforementioned definitions; description of most recent definition (the Berlin definition), and its limitations; and practical importance of the new definition.

CONCLUSIONS

ARDS is a serious disease that remains an ongoing diagnostic and therapeutic challenge. The evolution of definitions used to describe the disease shows that studies are needed to validate the current definition, especially in pediatrics, where the data are very scarce.

In silico study of the haemodynamic effects induced by mechanical ventilation and biventricular pacemaker

In silico modeling of the cardiovascular system (CVS) can help both in understanding pharmacological or pathophysiological process and in providing information which could not be obtained by means of traditional clinical research methods due to practical or ethical reasons. In this work the numerical CVS was used to study the effect of interaction between mechanical ventilation and biventricular pacemaker by haemodynamic and energetic point of view. Starting from literature data on patients with intra and/or inter-ventricular activation time delay and treated using biventricular pacemaker, we used in silico simulator to analyse the effects induced by mechanical ventilatory assistance (MVA). After reproducing baseline and CRT conditions, the MVA was simulated changing the mean intrathoracic pressure value. Results show that simultaneous application of CRT and MVA yields a reduction of cardiac output, left ventricular end-diastolic and end-systolic volume when positive mean intrathoracic pressure is applied. In the same conditions, when MVA is applied, left ventricular ejection fraction, mean left (right) atrial and pulmonary arterial pressure increase.

Recurrent episodic hypoxaemic respiratory failure following a stroke

A 68-year-old man with no cardiovascular risk factors was admitted with a stroke because of multiple brain infarcts in different vascular territories. He required mechanical ventilation for hypoxia as a result of aspiration pneumonia. Subsequent recovery was hindered by episodic, unexplained hypoxia. Investigations excluded pulmonary embolism, pulmonary hypertension and severe lung diseases. Transthoracic echocardiography (TTE) with saline bubble contrast showed mild, delayed, right-to-left shunting, thought to represent an insignificant, intrapulmonary, non-cardiac shunt. Hypoxic episodes worsened, requiring admission from community rehabilitation hospital to our centre and another period of mechanical ventilation. Elevated alveolar-arterial gradients indicated a non-hypoventilatory cause. Repeat TTE bubble contrast study and transoesophageal echocardiography (TOE) demonstrated a patent foramen ovale (PFO) with large shunt potential, associated with an aneurysmal interatrial septum. This provided a unifying explanation for cryptogenic stroke and recurrent hypoxaemia. After percutaneous PFO closure hypoxic episodes ceased and he returned successfully to rehabilitation.

Patent foramen ovale: Its significance in anesthesia and intensive care: An illustrated case

Patent foramen ovale (PFO) is defined as a valve-like opening at the level of foramen ovale or between septum primum and secundum without evidence of the anatomical defect. Paradoxical embolism (PDE) is an embolus passing through a defect PFO leading to end-organ dysfunction. PDE in septic shock is not yet reported in the literature. A 49-year male presented to the emergency department with shortness of breath since one day and pain in the left side of the chest. Chest x0 -ray revealed middle-left lobe pneumonia with pleural effusion; he was started on Co-amoxiclav, and admitted to the ward. After 6 h, his chest pain suddenly significantly increased difficulty in breathing and his oxygen saturation dropped. X-ray of the chest showed left pneumothorax, chest drain was inserted and he was intubated. He became hemodynamically unstable with maximum ventilatory support and noradrenalin. On day 4, he was found to have new pansystolic murmur in the tricuspid area. An echocardiogram revealed global hypokinesia, two mobile thrombi in the right atrial cavity, and PFO. It was noticed that his right toe had blackish discoloration. An angiogram showed occlusion of the right superficial femoral artery and immediately an embolectomy. On day 11, he was transferred to the ward. PDE needs a high index of suspicion in septic shock patients with ARDS. PDE requires PEEP adjustment, early anticoagulation, and thromboprophylaxis.

The evolving management of venous bullet emboli: a case series and literature review

Bullet emboli are an infrequent and unique complication of penetrating trauma. Complications of venous and arterial bullet emboli can be devastating and commonly include limb-threatening ischaemia,pulmonary embolism, cardiac valvular incompetence, and cerebrovascular accidents. Bullets from penetrating wounds can gain access to the venous circulation and embolise to nearly every large vascular bed. Venous emboli are often occult phenomenon and may remain unrecognised until migration leads to vascular injury or flow obstruction with resultant oedema. The majority of arterial emboli present early with end-organ or limb ischaemia. We describe four separate cases involving venous bullet embolism and the subsequent management of each case. Review of the literature focusing on the reported management of these injuries, comparison of techniques of management, as well as the evolving role of endovascular techniques in the management of bullet emboli is provided.

Prevalence and prognosis of shunting across patent foramen ovale during acute respiratory distress syndrome

OBJECTIVE

Right-to-left shunting across a patent foramen ovale may occur in acute respiratory distress syndrome as a result of pulmonary hypertension and positive-pressure mechanical ventilation. The shunt may worsen the hypoxemia. The objective of our study was to determine the prevalence, clinical implications, and prognosis of patent foramen ovale shunting during acute respiratory distress syndrome.

DESIGN

Prospective study.

SETTING

Medical intensive care unit of a university hospital in Créteil, France.

PATIENTS

Two hundred three consecutive patients with acute respiratory distress syndrome.

INTERVENTIONS

Patent foramen ovale shunting was detected by using transesophageal echocardiography with modified gelatin contrast. Moderate-to-large shunting was defined as right-to-left passage of at least 10 bubbles through a valve-like structure within three cardiac cycles after complete opacification of the right atrium. In 85 patients without and 31 with shunting, the influence of the positive end-expiratory pressure level on shunting was studied.

MEASUREMENTS AND RESULTS

The prevalence of moderate-to-large patent foramen ovale shunting was 19.2% (39 patients). Compared to those in the group without shunting, the patients in group with shunting had larger right ventricle dimensions, higher pulmonary artery systolic pressure, and a higher prevalence of cor pulmonale. Compared to patients without shunting, patients with shunting had a poorer Pa(O(2))/Fi(O(2)) ratio response to positive end-expiratory pressure, more often required prone positioning and nitric oxide as adjunctive interventions, and had fewer ventilator-free and intensive care unit-free days within the first 28 days.

CONCLUSIONS

Moderate-to-large patent foramen ovale shunting occurred in 19.2% of patients with acute respiratory distress syndrome, in keeping with findings from autopsy studies. Patent foramen ovale was associated with a poor oxygenation response to positive end-expiratory pressure, greater use of adjunctive interventions, and a longer intensive care unit stay.

Acute pulmonary embolism and a patent foramen ovale: analysis of atrial right-to-left shunting by biphasic transcardiopulmonary thermodilution curves

A 69-year-old woman with an acute pulmonary embolism developed an intracardiac right-to-left shunt, which was diagnosed early on and quantified via biphasic transcardiopulmonary thermodilution curves. With transesophageal echocardiography, a patent foramen ovale and an impressive atrial right-to-left shunt were visualized.

Acute respiratory distress syndrome 40 years later: time to revisit its definition

OBJECTIVE

Acute respiratory distress syndrome is a common disorder associated with significant mortality and morbidity. The aim of this article is to critically evaluate the definition of acute respiratory distress syndrome and examine the impact the definition has on clinical practice and research.

DATA SOURCES

Articles from a MEDLINE search (1950 to August 2007) using the Medical Subject Heading respiratory distress syndrome, adult, diagnosis, limited to the English language and human subjects, their relevant bibliographies, and personal collections, were reviewed.

DATA SYNTHESIS

The definition of acute respiratory distress syndrome is important to researchers, clinicians, and administrators alike. It has evolved significantly over the last 40 years, culminating in the American-European Consensus Conference definition, which was published in 1994. Although the American-European Consensus Conference definition is widely used, it has some important limitations that may impact on the conduct of clinical research, on resource allocation, and ultimately on the bedside management of such patients. These limitations stem partially from the fact that as defined, acute respiratory distress syndrome is a heterogeneous entity and also involve the reliability and validity of the criteria used in the definition. This article critically evaluates the American-European Consensus Conference definition and its limitations. Importantly, it highlights how these limitations may contribute to clinical trials that have failed to detect a potential true treatment effect. Finally, recommendations are made that could be considered in future definition modifications with an emphasis on the significance of accurately identifying the target population in future trials and subsequently in clinical care.

CONCLUSION

How acute respiratory distress syndrome is defined has a significant impact on the results of randomized, controlled trials and epidemiologic studies. Changes to the current American-European Consensus Conference definition are likely to have an important role in advancing the understanding and management of acute respiratory distress syndrome.

[Minimally invasive cardiopulmonary monitoring with the PiCCO Plus system]

Insertion of a central venous catheter and an arterial catheter would be indicated in hemodynamically unstable or severely hypoxic patients in critical care units. In this setting, cardiorespiratory monitoring by transpulmonary thermodilution (TPTD) can be considered minimally invasive given that only a single arterial thermodilution catheter and a single central venous catheter are required to be connected to a specific monitor (the PiCCO Plus, Pulsion Medical Systems, Munich, Germany). TDTP simultaneously measures cardiac output, preloading, and cardiac function in hemodynamically unstable patients and predicts the response to volume. The technique can be managed by any health care professional. In hypoxic patients, TDTP identifies cases of pulmonary edema that might benefit from a negative fluid balance, evaluates pulmonary vascular permeability, facilitates our understanding of pathophysiologic mechanisms of hypoxemia, and predicts the likelihood of deleterious hemodynamic effects of positive end-expiratory pressures.

The Incidental Finding of a Patent Foramen Ovale During Cardiac Surgery: Should It Always Be Repaired? A Core Review

With the increased use of intraoperative transesophageal echocardiography, patent foramen ovale (PFO) has become a common finding during heart surgery. This finding presents a difficult dilemma for cardiac surgeons, since the impact of intraoperatively diagnosed PFOs on postoperative outcome is unknown. Changes in the surgical plan required for closure of a PFO subject the patient to the possibility of additional risk. On the other hand, a decision to not close a PFO exposes the patient to unclear immediate and long-term consequences. Deciding whether or not to close a PFO currently depends on the clinicians' personal preferences, the probability of intraoperative and postoperative hypoxemia, and any anticipated deviation from the initial surgical plan. Most clinicians agree that an intraoperatively diagnosed PFO must be closed when surgery leads to a high risk of hypoxemia (e.g., left ventricular assist devices placement, heart transplantation); should be closed in most cases when minimal deviation from the initial surgical plan is needed for PFO closure (e.g., mitral valve or tricuspid valve surgeries); and probably, should be closed during heart surgeries performed without atriotomy and bicaval cannulation when the risk of perioperative or remote PFO-related complications is increased. The recent development of percutaneous methods of PFO closure provides a valuable backup for those cases when PFO is not closed and postoperative hypoxemia or other complications may be attributable to the uncorrected PFO.

Hypoxemia Complicating LVAD Insertion: Novel Application of the Amplatzer PFO Occlusion Device

We report a case of profound systemic hypoxemia complicating left ventricular assist device (LVAD) insertion due to right to left shunting through a patent foramen ovale (PFO) in association with a Chiari network. The patient was successfully managed with percutaneous closure of the interatrial defect using an Amplatzer PFO occlusion device and judicious reduction in LVAD flows.