Massive pulmonary embolism (MPE) is a keystone in the history of ECMO, since the invention of the heart-lung machine was urged by the disappointing death of a patient suffering from this condition [ 1 ]. In 1931, Gibbon was assigned to monitor a lady with pulmonary embolism after a cholecystectomy; he had to call his chief when the situation was deteriorating at the point that a pulmonary embolectomy could be tried as a last chance. Gibbon [ 2 ] vividly described what happened:
During that long night, helplessly watching the patient struggle for life as her blood became darker and her veins more distended, the idea naturally occurred to me that if it were pos- sible to remove continuously some of the blue blood from the patient’s swollen veins, put oxygen into that blood and allow carbon dioxide to escape from it, and then to inject con- tinuously the now-red blood back into the patient’s arteries, we might have saved her life.
We would have bypassed the obstructing embolus and performed part of the work of the patient’s heart and lungs outside the body.
Then Gibbon and his wife started their experimental work on acute occlusive pulmonary hypertension and right ventricular failure [ 3 , 4 ] and fi nally developed the heart-lung machine [ 2 ] reporting in 1937 the possibility to maintain circulation in cats with experimental occlusion of the pulmonary artery [ 5 ].
M. Bombino (*) • S. Redaelli
Department of Emergency and Urgency, General Intensive Care Unit , San Gerardo Hospital , Via Pergolesi, 33 , Monza (MB) 20900 , Italy e-mail: michela.bombino@gmail.com; sara.redaelli14@gmail.com A. Pesenti
Department of Health Sciences , University of Milano-Bicocca, San Serardo Hospital , Via Pergolesi, 33 , Monza (MB) 20900 , Italy e-mail: antonio.pesenti@unimib.it
Pulmonary Embolism, 16
Pulmonary Hypertension, Septic Shock and Trauma
Michela Bombino , Sara Redaelli , and Antonio Pesenti
Many years passed since then, but the indication for ECMO in supporting the failing right ventricle (RV) never subsided. The rationale of ECMO support in RV failure is to divert some blood from the right atrium to the arterial circulation, thus unloading the RV and relieving its dilatation, which in turn will lead to increased left ventricular output due to ventricular interdependence [ 6 , 7 ]. ECMO relieves hypoxemia due to shunt in this setting and, through the required anticoagulation, provides also a therapeutic mean in thromboembolism.
In idiopathic pulmonary arterial hypertension, extracorporeal support is used to bridge patients to lung transplantation when medical therapy is exhausted or as a temporary aid in cases of increased cardiovascular requirement.
16.1.1 ECMO in Massive Pulmonary Embolism
Despite the great therapeutic armamentarium available for MPE, the reported mor- tality of patients presenting with RV failure and cardiogenic shock is still as high as 20–50 % [ 8 ].
Davies reported the fi rst successful use of ECMO as a temporary support in MPE outside the operating room in 1995 [ 9 ]. It is noteworthy that the patient was kept conscious during the 6-day ECMO support. Plenty of case reports have been pub- lished since then on the successful use of extracorporeal support in MPE leading to cardiac arrest or cardiogenic shock [ 10 – 27 ]; some patients were treated only with ECMO, and others were successfully bridged to surgical or catheter thrombectomy.
Case reports are biased by the high survival rate, since they report almost always on successful cases. Key points in the published case reports are the prompt institution of percutaneous ECMO, the achievement of haemodynamic stabilisation, the pos- sibility to perform diagnostic exams during ECMO and the transport of the patient to a facility where surgical embolectomy could be feasible.
Maggio and co-workers [ 28 ] published one of the largest series, including 21 patients with MPE with profound shock and severe hypoxemia treated with V-A (19 patients) or VV ECMO (2 patients). The overall survival rate was 62 %. They pointed out the feasibility of the rapid institution of percutaneous ECMO support as a rescue manoeuvre also when the patients suffered cardiac arrest due to ful- minant PE (8 cases). ECLS can be part of a therapeutic strategy comprising thrombolytics and other kinds of thrombectomies or can be curative with antico- agulation by itself. Daily follow-up with echocardiography would recognise the few patients requiring surgical embolectomy. Unfortunately, neurological com- plications leading to death were high in this patient population (4 patients, 50 % of the deaths).
Other case series [ 29 – 31 ] with good overall results have been published. Hashiba [ 30 ] reported 12 patients with fulminant PE in cardiac arrest at time of ECMO institu- tion, 10 of them survived. The authors pointed out that both survival and neurological outcomes of cardiac arrest patients with MPE were better compared to the outcomes of 16 patients with post-acute myocardial infarction cardiac arrest (survival 83.3 % vs.
12.5 %, p < 0.001; good neurological outcome 58.3 % vs. 6.3 %, p = 0.004).
Recently, Sakuma [ 32 ] reported the Japanese experience with percutaneous ECMO as adjunctive support in MPE. 193 cases were collected from the literature;
the overall survival rate was 73, 65 % in patients with cardiac arrest at the time of ECMO institution and as high as 86 % in those with cardiogenic shock.
In conclusion, ECMO support is of established benefi t in patients with MPE- related cardiac failure, and it is recognised as a fundamental step in its interven- tional treatment algorithm [ 33 , 34 ].
16.1.2 ECMO in Pulmonary Arterial Hypertension
The term pulmonary hypertension (PH) comprises different clinical entities as pointed out by the 2008 Dana Point classifi cation [ 35 ]. The importance of an early diagnosis and the recognition of common pathophysiologic mechanisms underlying some diseases are pivotal steps to establish an optimal management [ 36 – 41 ].
Furthermore, algorithms have been developed for the assessment and accurate clas- sifi cation of PH and for treatment allocation. Despite improvement in overall man- agement for these patients, mortality is still high; poor prognostic factors are a scleroderma-associated diagnosis and indices of RV failure.
RV failure can supervene in the setting of pulmonary arterial hypertension (PAH) also if there is a response to pulmonary vasodilators. Its pathophysiology is largely reviewed in the literature [ 7 , 42 – 47 ]: RV adapts better to volume overload than pres- sure overload, chronic pressure overload will cause RV dilatation and increase in wall stress leading to hypertrophic remodelling, RV ischemia can ensue and cardiac out- put will decrease due to ventricular interdependence. Treatment of RV failure depends on underlying disease and its stage [ 7 , 45 – 47 ] and the chronic or acute presentation.
ECMO can play a role in some conditions leading to RV failure as a temporary sup- port in “crisis” deteriorations or most commonly as a bridge to transplantation.
Veno-venous ECMO has been successfully used in cases of RV failure due to chronic pulmonary embolism hypertension after pulmonary endarterectomy to treat reperfusion syndrome or persistent pulmonary hypertension after surgery [ 48 , 49 ].
In a recent survey on surgical management and outcome of patients with chronic thromboembolic pulmonary hypertension, Mayer reported a 9.6 % incidence of pul- monary reperfusion oedema, and 16.7 % of the patients had persistent pulmonary hypertension. The need for ECMO in this population was 3.1 % [ 50 ].
In idiopathic PAH, ECMO has been used with different indications. Pereszlenyi [ 51 ] reported the use of ECMO intra- and postoperatively in patients undergoing bilateral lung transplantation: ECMO allowed the maintenance of protective venti- lation and a controlled reperfusion of the allograft.
VA ECMO is the choice if the patient is haemodynamically unstable due to global heart failure [ 52 – 54 ], but different approaches have been advocated to unload the RV. In the case of a patent foramen ovale, VV ECMO can succeed by itself in this task [ 55 ]. In other cases, VV ECMO plus an atrial septostomy has been applied [ 56 , 57 ], or a shunt between the pulmonary artery and the left atrium (PA-LA) inter- posed with a low-resistance pumpless system [ 54 , 58 ]. The introduction of ECMO
as “bridge to transplantation” in idiopathic PAH patients has been reported to decrease the waiting list mortality and was not associated with a worse outcome after transplantation [ 59 ].
Another ECMO indication is to overcome a pulmonary hypertensive crisis in otherwise stable patients on pharmacological therapy [ 55 , 60 ] or in cases of abrupt RV failure due to anaesthesia as described in a parturient PAH patient [ 61 ]. In the last case, ECMO has also been used as a pre-emptive measure [ 62 ] during elective termination of gestation.
In conclusion, temporary support of RV failure with ECMO during hyperten- sive pulmonary crisis or its long-term use as a “bridge” to lung transplantation is largely reported in the literature. ECMO support before transplantation is now fea- sible in awake, non-intubated patients with the possibility to perform physical therapy while waiting for organ assignment and is associated with a better progno- sis [ 63 – 65 ].