CASE REPORT |
https://doi.org/10.5005/jp-journals-10089-0061 |
Prone Positioning to Improve Oxygenation on VV-ECMO after Pulmonary Endarterectomy
1Department of Critical Care Medicine, Narayana Institute of Cardiac Sciences, Narayana Health City, Bengaluru, Karnataka, India
2Department of Anesthesiology, Narayana Institute of Cardiac Sciences, Bommasandra, Karnataka, India
Corresponding Author: Girish I Ramagondawar, Department of Critical Care Medicine, Narayana Institute of Cardiac Sciences, Narayana Health City, Bengaluru, Karnataka, India, Phone: +91 9620642372, e-mail: girish.ir.dr@narayanahealth.org
Received on: 14 June 2023; Accepted on: 04 July 2023; Published on: 23 August 2023
ABSTRACT
Patients on venovenous extracorporeal membrane oxygenator (VV-ECMO) can develop refractory hypoxemia, and various rescue measures are available. We present two cases of refractory hypoxemia noted postoperatively (post-op) due to reperfusion injury associated with pulmonary hemorrhage. These patients were supported with VV-ECMO and received prone ventilation (PV) due to refractory hypoxia. We noted an improvement in oxygenation with PV, which facilitated lung recruitment and successful weaning from VV-ECMO.
How to cite this article: Ramagondawar GI, Patangi SO. Prone Positioning to Improve Oxygenation on VV-ECMO after Pulmonary Endarterectomy. J Acute Care 2023;2(1):26–29.
Source of support: Nil
Conflict of interest: None
Patient consent statement: The author(s) have obtained written informed consent from the patients (for case 1, 2) for publication of the case report details and related images.
Keywords: Acute respiratory distress syndrome, Case report, Prone ventilation, Pulmonary endarterectomy, Pulmonary hemorrhage, Venovenous
BACKGROUND
The incidence of chronic thromboembolic pulmonary hypertension (CTEPH) following acute pulmonary embolism is 3.13% (95% confidence interval (CI): 2.11–4.63%).1 Studies from China revealed the incidence of CTEPH more [4.46% (95% CI: 1.68–11.32%)] than those from Europe [2.82% (95% CI: 1.82 - 4.34%)].1
The primary objective of a venovenous extracorporeal membrane oxygenator (VV-ECMO) is to optimize gas exchange while providing rest to the lungs. The Extracorporeal Life Support Organization’s April 2023 registry report states a survival of 58% for adult respiratory failure supported on VV-ECMO.2
Severe hypoxemia on VV-ECMO is defined as the partial pressure of oxygen (PaO2) of <50 mm Hg in two arterial blood samples taken at least 60 minutes apart.3
On VV-ECMO, the standard options to treat hypoxemia include strategies to avoid or minimize recirculation, the pharmacologic modulation of the intrapulmonary shunt, the use of β-blockers, therapeutic hypothermia, prone positioning, and transition from VV-ECMO to venoarterial-ECMO or a hybrid configuration.3
CASE DESCRIPTION
Case 1
An elderly man with CTEPH with complete occlusion of the left pulmonary artery (LPA) was operated on for pulmonary thromboendarterectomy (PTE). The LPA complete clot load could not be removed due to distal segmental disease. The patient underwent tracheotomy on the 7th postoperative (post-op) day (POD). On POD 22nd, in view of respiratory acidosis, pH of <7.2, partial pressure of arterial CO2 of >80 mm Hg, and PaO2 of <45 mm Hg, which developed secondary to pulmonary hemorrhage showing marginal improvement with prone ventilation (PV). VV-ECMO was initiated. Cannulation was carried out via a right femoral–right internal jugular vein approach. Initial ECMO settings were a sweep gas flow of 1.5 L/minute, pump flow of 4.4 L/minute, and 3000 RPM. Anticoagulation was achieved and maintained with unfractionated heparin targeting activated clotting time of 140–160 seconds. Rest ventilation was set at a Pmax of 20 cm H2O, positive end-expiratory pressure of 10 cm H2O, a respiratory rate of 10 breaths/minute, and his plateau pressure <25 cm H2O. He developed a lung bleed and was taken to a hybrid catheterization laboratory, and the culprit’s vessel was embolized.
On POD 28th, after 10 days of VV-ECMO run, patient PaO2 continued to be in the range of 45–50 mm Hg, and a decision was taken to prone him on VV-ECMO. After six cycles of PV, gas exchange improved, a chest X-ray showed significant improvement (Fig. 1), he was weaned off the ventilator and was on minimal oxygen support on the tracheal mask was decannulated from VV-ECMO when the sweep was off. He could maintain oxygen saturation of >94% on room air and was discharged home on the 51st POD.
Figs 1A to D: Serial X-ray of case 1: (A) Immediate post-op; (B) Before initiation of VV-ECMO; (C) During VV-ECMO had lung bleed; (D) Postdischarge X-ray
Case 2
A middle-aged woman underwent PTE for CTEPH. VV-ECMO was initiated for pulmonary hemorrhage on day 3 for low PaO2. She underwent a tracheotomy, experienced multiple lung bleeds, and had the culprit vessels embolized. On VV-ECMO, two cycles of PV were performed to counter her high extraction on a standard oxygenator even though the postoxygenator PaO2 level was >450 mm Hg. Each cycle PV was for 16 hours duration.
On day 43 of her recovery, she had her sweep gas and VV-ECMO weaned off. During the next few days of her intensive thoracic unit stay, she was weaned off from the ventilator and was discharged home on room air (Fig. 2).
Figs 2A to D: Serial X-ray of case 2: (A) Immediate post-op; (B) Before went on VV-ECMO; (C) During VV-ECMO had lung bleed; (D) Postdischarge X-ray
DISCUSSION
Pulmonary thromboendarterectomy (PTE) is a procedure used to treat surgically accessible CTEP.4 Reperfusion injury is the common cause of hypoxemia post-PTE surgery. There was a significant improvement in gas exchange which resulted in the reduction of sweep gas flow while PV was performed on VV-ECMO. VV-ECMO support is often used to provide respiratory support in patients with severe hypoxemia. However, ECMO support can be associated with complications such as bleeding, infection, and thrombosis. VV-ECMO is a life support technique used to augment gas exchange for critically ill patients who have failed conventional forms of mechanical ventilation.5
When encountered with hypoxemia on VV-ECMO, raising the hemoglobin to 12 gm/dL is recommended, but a study by Voelker et al. also found a 61% survival rate in a group of 18 patients with acute respiratory distress syndrome (ARDS) in whom hemoglobin concentrations were kept between 7 and 9 gm/dL with a transfusion trigger at 7 gm/dL.6 Published literature states that PV improves gas exchange and reduces ventilator-associated lung injury (VALI). By redistributing the patient’s body weight and expanding the patient’s under-ventilated lung areas, prone positioning enhances oxygenation.
Prone positioning can help patients on VV-ECMO to improve gas exchange and reduce the risk of VALI via its effects on various physiological parameters.7 Lucchini et al. conducted a retrospective study from November 2009 to 2014, which included a total of 45 PV in 14 VV-ECMO patients. The median duration of prone positioning cycles was 8 hours. No accidental dislodgement of intravascular lines, endotracheal tubes, chest tubes, or a decrease in VV-ECMO blood flow was observed, concluding that the application of PV during VV-ECMO has shown to be a safe and reliable technique when performed in a recognized ECMO center.8
In another study by Kipping et al., ECMO patients, 74 PV were performed during VV-ECMO is safe and improves oxygenation even after repositioning. This might ameliorate hypoxemia and reduce the harm from mechanical ventilation.9
Prone ventilation (PV) was done to facilitate lung recruitment and positional drainage of secretions. We have highlighted PV as an adjuvant therapy to successfully combat hypoxia on VV-ECMO and thereby reduce the duration of the VV-ECMO run. VV-ECMO runs can be longer in situations where low oxygenation can be the culprit cause. However, with PV, the duration of VV-ECMO can be reduced.
Physiological effects of the prone position in ECMO patients are:
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Improved oxygenation: Due to a decrease in the ventilation-perfusion ratio, PV can increase oxygenation in patients with ARDS. The prone positioning in severe ARDS study demonstrated improvements in blood gases during the PV session in patients with severe ARDS; early application of prolonged prone-positioning sessions significantly decreased 28 and 90-day mortality.10 Albert et al. conducted a retrospective analysis of data collected prospectively by Guérin et al. and concluded that the increase in survival seen in patients with ARDS who receive PV does not depend on whether the change in position improves gas exchange and infer that it results from the ability of prone positioning to reduce VILI.11
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Reduced right ventricular strain: Prone position was shown to reduce right ventricular strain in patients on VV-ECMO. The incidence of RV failure related to ARDS has been reported to be 10–25%. The PV, according to the authors, enhanced right ventricular function and reduced the likelihood of right heart failure.12
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Prone ventilation (PV) increases chest wall elastance; this change is usually accompanied by improved lung recruitment, a reduction in alveolar shunt, and better ventilation/perfusion ratio with a consequent improvement in oxygenation and CO2 clearance and a reduction in VALI.13
Literature with regard to PV on VV-ECMO after PTE surgery to counteract hypoxemia secondary to lung bleed is not available to our knowledge. Hence, we presented this case report series to highlight this therapy. Hopefully, this report will aid clinicians with an option to counter the frequently faced conundrum of how to tackle hypoxia on VV-ECMO.
We did not find a similarity in timelines with regard to the improvement of gas exchange in both our cases. The first patient took six cycles of PV as opposed to the second patient needing only two cycles of PV to achieve adequacy of oxygenation, which resulted in a successful wean off VV-ECMO. However, with each cycle of PV, there was a marginal improvement in oxygenation within the hour in both cases, which didn’t sustain when the prone cycle was terminated. However, in subsequent prone cycles, the sustainability of oxygenation improved in both cases, which facilitated a successful wean.
Prone ventilation (PV) in patients on VV-ECMO should be considered as an adjunctive therapy to optimize gas exchange. However, this should only be done with a team of healthcare professionals who are skilled in this technique. Before PV, it is important to assess the patient’s clinical condition and the stability of the ECMO circuit to prevent potential complications.
ORCID
Sanjay O Patangi https://orcid.org/0000-0002-5303-2925
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