**2.2 ECLS and DPC implantation strategies**

The individual approach of ECLS implantation heavily depends upon the place (out of the hospital, floor, bedside or operation theatre), urgency (elective or emergency), and aetiology (PCCS, post-PCI, primary graft failure or bridge to transplant) of the cardio-respiratory failure. In patients with cardiopulmonary arrest under resuscitation or peri-arrest patients, quick introduction of ECLS through is of utmost importance in order to sustain the patient's life. In this situation, the primary goal is the insertion of systemic arterial and venous cannulas and there may not be time for simultaneous DPC insertion. Such emergency bedside ECLS implantation in the intensive therapy unit is a scenario that usually does not offer facilities of an operation theatre making percutaneous insertion of peripheral cannulas necessary (**Figure 1**), often without availability of sonography to appropriately size for the smallest cannulae or fluoroscopy for intravascular positioning. In this context, it is important to note that percutaneous insertion of the DPC can be challenging in the presence of a systemic arterial cannula already in place, either due to the reduction or even absence of blood flow distal to the cannulation site or vasospasm and vessel injury during primary cannulation. Nevertheless, if it is attempted, ultrasound guidance during insertion is helpful and angiographic confirmation of DPC tip position in the superficial femoral artery should be obtained [25, 28].

PCCS is a scenario usually encountered after complex and long operations and has an extreme mortality. While ECLS is the only treatment option for these patients, it is important to make the decision to use it as early as possible and avoid repeated and prolonged attempts to wean the patient of CPB as these cause considerable collateral damage. ECLS should not be viewed as a last resort after all else has failed and the patient is in a catastrophic state but rather as a tool to be proactively used to ensure protection of organ function, continuous, uninterrupted sufficient perfusion and maintenance of a functioning coagulation system, thus preventing the well-known ICU exsanguination of these patients and offering both the heart as well as the patient a reasonable chance to recover.

For this, CPB can be converted directly to central ECLS, using the established cannulation or to peripheral ECLS. Peripheral ECLS allows the chest to be fully closed and no re-opening is needed for explantation of the ECLS system or for cannula-site bleeding especially in these patients on anti-coagulation therapy. With the patient stable on CPB it is safe and easy to perform a cut down to the groin vessels and placement of the cannulas under direct vision (**Figure 2**). If necessary, DPC can be introduced simultaneously. If the myocardial function is somewhat preserved, ECLS flows should be kept at a level allowing for blood flow through the heart to maintain left ventricular ejection in order to prevent its dilatation, stasis of

**Figure 1.** *Percutaneous cannulation.*

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pulsatility.

**Table 1.**

*Advances in Extracorporeal Membrane Oxygenation - Volume 3*

Cut down and under vision cannulation whenever feasible Percutaneous cannulation only with USG/Fluoroscopy

Accept low ECLS flow when possible to reduce cannula size

Selective infusion of prostacyclin via distal perfusion cannula Keep patient awake- can complain of limb pain (ischemia) Suspect limb ischemia if serum Lactate levels high Achieve and maintain good anticoagulation

Use of small calibre systemic arterial cannula Use of Prophylactic distal arterial perfusion cannula Use of Prophylactic distal venous drainage cannula Utilise contralateral limb for venous drainage cannula

**Prevention of limb ischemia**

Bear high suspicion for ischemia

Maintain left ventricular ejection

Wean vasopressors as soon as possible

Near infra-red spectroscopy in distal limb Continuous measurement of DPC flow Doppler Ultrasound of distal limb arteries

Prefer open cut-down and repair of vessels Perform balloon thrombo-embolectomy

Maintain pulsatile flow

**Implantation**

**Maintenance**

**Monitoring**

Temperature **Explantation**

Avoid groin compression

*Prevention of limb ischemia.*

further. While maintaining central blood pressure levels, capillary perfusion of end organs, specifically the intestine as well as the limbs may be significantly reduced in such a scenario. Therefore, it is important to strike a balance between vasopressor delivery dependent blood pressure management, maintenance of fluid balance, arterio-venous perfusion pressure delta and capillary delivery, prioritising vasopressor weaning over 'drying up the lungs'. Maintenance of good intravascular volume also allows better ECLS flow and cardiac output along with

In essence, utilisation of a small calibre systemic femoral cannula, when possible, acceptance a biomechanical output with low ECLS flow, continued pulsatile flow and avoidance of high dose vasopressors obviate the need for prophylactic DPC insertion in patients, potentially protecting them from DPC related complications. With this conservative management and a protocol of continuous, diligent monitoring, patients that develop limb ischemia can then be detected at an early

stage and treated with subsequent DPC, if necessary.

**Figure 2.** *Open cut-down cannulation.*

blood and possible atrial and ventricular thrombus formation. In severe myocardial injury, the heart can be rested with full ECLS flow without ejection. In this case, the need for ventricular decompression should be discussed. With biological no-flow, a case of high vasopressor requirement or expected longer duration of support, the DPC can introduced at the same time.

Peri or post-PCI, with fluoroscopy readily available, all ECLS cannulas can be introduced percutaneously and their position be confirmed before the patient leaves the cath-lab. ECLS as a bridge to transplant in awake patients is a recent trend that offers early ambulation and avoids ventilator-associated complications [29]. However, bedside ECLS can be challenging as a cut down is not comfortable in such patients and difficult outside the environment of the operating theatre. In these patients, the systemic arterial and venous cannulae are introduced percutaneously under local anaesthesia or the patient undergoes a short analgo-sedation as full sedation may be too high risk. As a general principal, contralateral femoral arterial and venous cannulation should be encouraged, as the venous stasis and possible limb oedema caused by the venous cannula may intensify any ipsilateral arterial cannula related compromised distal limb perfusion [15].

## **2.3 Expectant monitoring of limb**

#### *2.3.1 Continuous monitoring*

Continuous diligent monitoring of the limb for any signs of ischemia is a key to allow for timely and appropriate intervention. One elegant and inexpensive method of continuous monitoring is placing an additional pulse-oximetry probe on the toes of the cannulated limb. Its reading and waveform can be compared with the probe placed on the normal limb. However, hypothermia and non-pulsatile flow may not offer reliable pulse-oximetry reading. Near infra-red spectroscopy (NIRS), routinely used and established in transcranial cerebral oximetry can be helpful in such cases and is an alternative method for continuous monitoring. It involves application of sensor pads on the legs that detects regional oxygen saturation (rSO2)

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*Isn't Limb as Precious as Life?*

**Figure 3.**

*NIRS continuous monitoring.*

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

continuously, representing adequacy of tissue oxygenation. It should be applied as soon as ECLS is started. The rSO2 of the cannulated limb is compared with that of the opposite limb as well as with the baseline rSO2 providing live evidence of a drop in limb perfusion (**Figure 3**). A reduction in rSO2 values in the cannulated limb to less than 40 or more than 25% from baseline suggest inadequate limb perfusion and mandates urgent intervention [30, 31]. Technical glitches, however, like improper sensor pads attachments should be addressed before attempting to improve distal limb perfusion. Dong and colleagues utilised the NIRS successfully in a group of ECLS patients to detect and successfully treat limb ischemia with DPC in all patients having NIRS whereas 13.9% of the cohort not monitored required a fasciotomy [31]. Indeed, NIRS may reliably detect limb ischemia before it becomes clinically evident [31, 32]. Lamb *et al.* suggest continuous monitoring of limb utilising NIRS and evaluation of pedal doppler signals in case of a drop in baseline NIRS values to ensure adequate distal limb perfusion [33]. If available, we suggest that

In presence of DPC, continuous monitoring of its trans-canullar flow is the gold standard in monitoring distal limb perfusion (**Figure 4**). The DPC flow is dependent on a variety of factors, namely total ECLS flow, mean arterial pressure and systemic and peripheral vascular resistance, and possible thrombo-embolic occlusion in the DPC or distal artery. Therefore, any drop in the DPC flow must be correlated with these factors before any intervention. A drop in the DPC flow should also be cross-checked with the clinical signs of limb ischemia and drop in NIRS rSO2. An hourly record of the DPC flow along with other ECLS parameters should be maintained and perfusionists should be alerted if there is a significant change. Cannula or connecting line bending, thrombosis and dislocation are common non patient related reasons for decreased DPC flow. Both antegrade and retrograde blood flow should be checked by clamps on either side of DPC side-port [10]. In the absence of a side-port, the DPC may have to be disconnected to assess for backflow through the cannula and appropriate flow in the proximal line. Thrombosis in the DPC is usually accompanied by embolization into the distal femoral artery and mandates embolectomy and DPC replacement. Only in the minority of cases it can be addressed by

Despite continuous monitoring of limb perfusion by means of NIRS and DPC flow, hourly inspection for skin colour change, palpation for temperature, capillary return at toe tips, calf palpation and calf girth measurement for compartment syndrome is of paramount importance. Pedal pulses should be checked in the *dorsalis pedis* and

NIRS should be part of the protocol for peripheral ECLS.

aspiration of the thrombotic material.

*2.3.2 Hourly monitoring*

**Figure 3.** *NIRS continuous monitoring.*

continuously, representing adequacy of tissue oxygenation. It should be applied as soon as ECLS is started. The rSO2 of the cannulated limb is compared with that of the opposite limb as well as with the baseline rSO2 providing live evidence of a drop in limb perfusion (**Figure 3**). A reduction in rSO2 values in the cannulated limb to less than 40 or more than 25% from baseline suggest inadequate limb perfusion and mandates urgent intervention [30, 31]. Technical glitches, however, like improper sensor pads attachments should be addressed before attempting to improve distal limb perfusion. Dong and colleagues utilised the NIRS successfully in a group of ECLS patients to detect and successfully treat limb ischemia with DPC in all patients having NIRS whereas 13.9% of the cohort not monitored required a fasciotomy [31]. Indeed, NIRS may reliably detect limb ischemia before it becomes clinically evident [31, 32]. Lamb *et al.* suggest continuous monitoring of limb utilising NIRS and evaluation of pedal doppler signals in case of a drop in baseline NIRS values to ensure adequate distal limb perfusion [33]. If available, we suggest that NIRS should be part of the protocol for peripheral ECLS.

In presence of DPC, continuous monitoring of its trans-canullar flow is the gold standard in monitoring distal limb perfusion (**Figure 4**). The DPC flow is dependent on a variety of factors, namely total ECLS flow, mean arterial pressure and systemic and peripheral vascular resistance, and possible thrombo-embolic occlusion in the DPC or distal artery. Therefore, any drop in the DPC flow must be correlated with these factors before any intervention. A drop in the DPC flow should also be cross-checked with the clinical signs of limb ischemia and drop in NIRS rSO2. An hourly record of the DPC flow along with other ECLS parameters should be maintained and perfusionists should be alerted if there is a significant change. Cannula or connecting line bending, thrombosis and dislocation are common non patient related reasons for decreased DPC flow. Both antegrade and retrograde blood flow should be checked by clamps on either side of DPC side-port [10]. In the absence of a side-port, the DPC may have to be disconnected to assess for backflow through the cannula and appropriate flow in the proximal line. Thrombosis in the DPC is usually accompanied by embolization into the distal femoral artery and mandates embolectomy and DPC replacement. Only in the minority of cases it can be addressed by aspiration of the thrombotic material.
