**3.1 Therapeutic insertion of distal perfusion cannula**

Limb ischemia due to inadequate flow in the distal artery detected at early stage ideally should be treated with the introduction of the DPC if not placed at ECLS implantation. Apart from conscious avoidance, reasons for not introducing

**178**

**Figure 4.**

*Continuous DPC flow monitoring.*

**2.4 Early detection of limb ischemia**

*Advances in Extracorporeal Membrane Oxygenation - Volume 3*

posterior tibial artery and when not palpable a hand-held ultrasound Doppler should be utilised to confirm the flow. The flow may be graded for documentation as palpablestrong pulsatile, palpable- weak pulsatile, doppler- pulsatile, doppler- continuous flow and absent flow. Hourly recording of continuously monitored variables namely DPC flow, NIRS rSO2 are necessary to establish trends and detect limb ischemia before it is clinically apparent. Numbers and signs that may be missed during continuous monitoring can be caught in a vigilant hourly survey. Ischemia in toes is seen not uncommon, even in the presence of well-maintained DPC flow due to peripheral micro thromboembolization and/or vasospasm due to peripheral shut down or high dose vasopressors.

Early detection of inadequate limb perfusion allows for immediate intervention to avoid its catastrophic consequences. In absence of the DPC, continuous NIRS monitoring supplemented by an hourly survey by means of clinical examination and Doppler ultrasound flow check in the distal arteries is usually adequate to detect limb ischemia at an early stage. NIRS rSO2, clinical signs and ultrasound Doppler flow in the cannulated limb should be compared with opposite limb, not to confuse ischemia with peripheral shut down and peripheral vasospasm. In patients with a prophylactic or therapeutic introduction of DPC, it is important to remember that the DPC does not guarantee adequate perfusion. Thus, continuous measurement of DPC flow, maintenance of adequate anticoagulation and monitoring of actual limb perfusion remains essential. Awake non-intubated, non-sedated patients supported on ECLS may complain of pain, tingling- numbness or stiffness with the onset of limb ischemia. An increase in lactate levels without an attributable source and acute kidney failure may be signs of subclinical rhabdomyolysis and should immediately

prophylactic DPC are among others: failed percutaneous insertion, atherosclerotic plaque palpated in open cut-down and need to return to the intensive care unit for patient stabilisation. In a metanalysis reviewing 22 retrospective studies comparing peripheral ECLS with or without DPC, the presence of a DPC was associated with at least a 15.7% absolute reduction in the incidence of limb ischemia; although without any impact on the patient survival [35].

Several cannulas from an introducer sheath up to a paediatric arterial cannula are recommended in the literature for this purpose. An ideal is the one that is resistant to bending and thrombosis and offering a least resistance to flow. We found the incidences of limb ischemia and limb ischemia requiring surgical intervention were significantly higher for the introducer sheath compared with the 10–12F Bio-Medicus® paediatric seldinger cannula utilised for distal limb perfusion (30.6 vs. 15.6% and 15.4 vs. 6.25%, respectively) [11].

To introduce the DPC percutaneously, the superficial femoral artery may be visualised distal to the systemic cannula via Ultrasound. If this is not possible, a cut-down insertion should be performed. If introduced bedside, especially percutaneously, the position of the DPC should be confirmed via x-ray.

#### **3.2 Continuous infusion of anticoagulants and vasodilator drugs**

Any ECLS circuit exposes blood to non-biological surfaces and is in itself thrombogenic. Therefore, adequate anticoagulation, usually achieved by continuous intravenous delivery of unfractionated heparin is essential to prevent complications such as thrombus formation and clotting of the circuit and stroke, limb and bowel ischemia. Conventionally heparin is delivered via a central venous catheter. As the small arteries of the distal limb are specifically at risk of micro-thrombotic clotting complications a targeted delivery of anticoagulants may offer a strategy to prevent distal ischemia. Continuous heparin delivery in the ECLS circuit before oxygenator at beginning of ECLS should be considered in any institutional protocol.

Due to the discrepancy in size of the aorta and distal superficial femoral artery as well as resistance between the systemic cannula and the DPC, there is a significant discrepancy in the flow rate between them, sometimes resulting in very little or almost no flow through the for DPC. In these cases, a gate clamp on the systemic arm can be helpful; however, it may cause flow turbulence, is potentially thrombogenic and increases driving pressure in the system.

Alternatively, and already mentioned above, Epoprostenol, a potent vasodilator, which is established in the treatment of peripheral vascular disease, can be delivered directly into the limb via DPC side-port in order to induce peripheral vasodilatation and increase perfusion. Some paediatric aortic cannulas have a sideport that can be readily used for this purpose [10]. Otherwise, a 3/8–3/8″ connector with a side-port can be inserted into the arm feeding the DPC. In some patients this may result in an increased requirement of vasopressors to maintain central arterial pressure. As a word of caution, selective infusion of vasodilators may also result in hyper-perfusion and clinically relevant oedema, especially in presence of an *ipsilateral* venous cannula.

#### **3.3 Change of cannulation site**

Peripheral access for ECLS seek mainly due to urgency or bedside scenario is converted to central access once patient is stabilised or develops complication due to peripheral cannulation. One of the strategies in suspected or established limb involves shifting the arterial cannulation site followed by embolectomy and, if necessary, repair of the vessel. In many cases this may be the ascending aorta, as this offers

**181**

**Figure 5.**

*Protocol for management of limb ischemia.*

*Isn't Limb as Precious as Life?*

*DOI: http://dx.doi.org/10.5772/intechopen.86391*

**3.4 Management of advanced limb ischemia**

**Percutaneous cannul.**

**Prophylacc DPC** Peripheral vascular disease

Check fluoroscopy for locaon of DPC p

Cath-lab Bedside

Young age Female gender

certain advantages such as oxygenated blood supply to coronaries and avoidance of any watershed phenomenon, even in patients with compromised lung function. Also, the opposite superficial femoral artery or axillary artery may be utilised if the treating physician wants to avoid sternotomy or cannulation of the aorta is difficult. In patients with acceptable lung function and compromised cardiac function, ECLS can be converted into a uni- or bi-ventricular short-term ventricular assist device at this time avoiding the further use of the oxygenator and thus allowing for a less

Fasciotomy is a decompression manoeuvre performed on the limb with acute compartment syndrome, a surgical emergency. Release of pressure allows reperfusion of the ischemic muscles potentially avoiding amputation. A recent metanalysis consisting 1886 patients found 10% incidence of compartment syndrome requiring fasciotomy [13].

**ECLS Implantaon**

Consider small systemic cannula Accept low (adequate) ECLS flow

Maintain pulsale flow

**Open cut-down cannul.**

**Avoid DPC** Small systemic cannula

Operaon theatre

Pulsale flow Wean vasopressors Vigilant monitoring

**Limb ischemia**

**Monitoring**

Connuous: NIRS, DPC flow Hourly survey: Ischemia signs, doppler flow check in distal arteries

Early intervenon Introduce DPC

Change cannulaon site Bridge to substanve therapy

stringent anticoagulation regime and easier mobilisation of the patient.

### *Isn't Limb as Precious as Life? DOI: http://dx.doi.org/10.5772/intechopen.86391*

certain advantages such as oxygenated blood supply to coronaries and avoidance of any watershed phenomenon, even in patients with compromised lung function. Also, the opposite superficial femoral artery or axillary artery may be utilised if the treating physician wants to avoid sternotomy or cannulation of the aorta is difficult. In patients with acceptable lung function and compromised cardiac function, ECLS can be converted into a uni- or bi-ventricular short-term ventricular assist device at this time avoiding the further use of the oxygenator and thus allowing for a less stringent anticoagulation regime and easier mobilisation of the patient.
