Fig. 34.2. Skin necrosis associated with an umbilical artery catheter. Such lesions develop after vasospasm or embolism. A: Spinal injury may be present when ischemia involves this region. B: The distal part

of an extremity is a common site for embolic arterial loss. The full extent of loss is unpredictable at this

stage. (From Fletcher MA. Physical Diagnosis in Neonatology. Philadelphia: Lippincott-Raven; 1998:127.)

Table 34.2 Laboratory Tests for Suspected Prothrombotic Disorders

Laboratory Test Collection Tube

Antiphospholipid antibody panel, anticardiolipin, lupus anticoagulant

(IgG, IgM)

Citrated plasma

Fibrinogen Citrated plasma

Protein C activity

Protein S activity

Antithrombin (activity assay)

Citrated plasma

Factor V Leiden

Prothrombin G

Methylenetetrahydrofolate reductase

Ethylenediaminetetraacetic acid

Homocysteine

Lipoprotein(a)

Citrated plasma

From Saxonhouse MA. Management of neonatal thrombosis. Clin Perinatol. 2012;39:191,with permission.

Chapter 34 ■ Management of Vascular Spasm and Thrombosis 227

c. Anticoagulation for at least 10 days; UFH or LMWH

is recommended for neonates with UAC-related

thrombosis.

d. If there are potentially life-, limb-, or organ-threatening signs in neonates with UAC-related thrombosis,

thrombolysis with rTPA should be considered.

e. If there are contraindications to thrombolysis, surgical thrombectomy may be indicated.

4. Anticoagulant/thrombolytic therapy

a. Contraindications

(1) Major surgery within the last 10 days

(2) Active or major bleeding: Intracranial, pulmonary, or gastrointestinal

(3) Preexisting cerebral ischemic lesions

(4) Seizures within 48 hours

(5) Relative contraindications (anticoagulant/

thrombolytic therapy may be given after correction of these abnormalities)

(a) Thrombocytopenia (platelet count <100 ×

109

/L)

(b) Hypofibrinogenemia (fibrinogen <100 mg/

dL)

(c) Severe coagulation factor deficiency

(d) Hypertension

b. Precautions

(1) No arterial punctures

(2) No subcutaneous or intramuscular injections

(3) No urinary catheterizations

(4) Avoid aspirin or other antiplatelet drugs.

(5) Monitor serial head ultrasound scans for intracranial hemorrhage.

c. Anticoagulants

(1) UFH

(a) Anticoagulant, antithrombotic effect limited by low plasma levels of antithrombin in

neonates.

 

h. Anticoagulation therapy with unfractionated heparin (UFH) or low-molecular-weight heparin

(LMWH) is used for clinically significant clots with

the goal of preventing clot extension or embolization.

i. Recombinant tissue plasminogen activator (rTPA) is

reserved for thrombolysis of severe life-, organ-, or

limb-threatening thrombosis.

j. The International Children’s Thrombophilia

Network, which is based in Canada, is a free

consultative service, maintained 24 hours a day, for

Fig. 34.1. Vasospasm following attempted radial artery catheterization in extremely preterm infant.

Table 34.1 Diagnosis of Vascular Thrombosis

Site Clinical Signs Diagnostic Imaging

CVL-associated venous thrombosis Malfunction of CVL, SVC syndrome, chylothorax, swelling and

livid discoloration of extremity, dilatation of collateral veins

over trunk or abdomen in chronic cases

Inferior vena cava thrombosis Lower limbs cool, cyanotic, edematous Contrast angiography

Doppler ultrasonography

Real-time 2D ultrasonography

Superior vena cava thrombosis

Renal vein thrombosis

Swelling of upper limbs and head, chylothorax

Flank mass, hematuria, thrombocytopenia, hypertension

Aortic or renal arterial thrombosis Systemic hypertension, hematuria, oliguria

Peripheral or central (aorta or iliac) arterial

thrombosis

Pallor, coldness, weak or absent peripheral pulse(s),

discoloration, gangrene

Right atrial thrombosis Congestive heart failure Echocardiography

Pulmonary thromboembolism Respiratory failure Lung perfusion scan

CVL, central venous line; SVC, superior vena cava.

}

226 Section V ■ Vascular Access

physicians worldwide who are caring for children

with thromboembolic disease. The toll-free number

in the North America is 1-800-NO-CLOTS; the

number for physicians elsewhere is 1-905-573-4795

(Web site http://www.1800noclots.ca/) The service

provides current management protocols as well as

links to the network and its services.

2. Management of catheter-related venous

thrombosis (12)

a. Either initial anticoagulation or supportive care

with radiological monitoring may be appropriate.

However, anticoagulation is recommended if extension of the thrombus occurs during supportive care.

b. Remove central venous lines (CVL) or umbilical

venous lines associated with confirmed thrombosis, preferably after 3 to 5 days of anticoagulation.

This recommendation has been made to reduce

the risk of paradoxical emboli at the time of CVL

removal.

c. Intravascular catheters are occasionally left in place

if local thrombolysis through the catheter is planned

(14).

d. Anticoagulation may be with LMWH or UFH for 3

to 5 days followed by LMWH.

e. Total duration of anticoagulation is between 6 and

12 weeks.

f. Thrombolytic therapy is not recommended for neonatal venous thrombosis unless major vessel occlusion is causing critical compromise of organs or limbs.

3. Management of arterial thrombosis (12)

a. Initiate management as for vasospasm if there are

peripheral signs of ischemia.

b. Remove catheter unless catheter-directed thrombolysis is planned (14)

A B

 

Chapter 34 ■ Management of Vascular Spasm and Thrombosis 225

Topical application of 2% nitroglycerine ointment at a dose of 4 mm/kg body weight, applied as a

thin film over the affected areas; may be repeated

after 8 hours (9–11).

D. Management of Catheter-Related

Thromboembolism

1. General principles

a. Thrombolysis to restore catheter patency for

obstructed central venous catheters is described in

Chapter 32.

b. Management of vascular thrombosis may involve

one or more of the following: Supportive care with

continued close observation, anticoagulation,

thrombolytic therapy, or surgical intervention

(1,8,12,13).

c. Infant should be managed in an appropriately

staffed and equipped neonatal intensive care unit

where anticoagulant or thrombolytic therapy can be

administered and monitored closely and supportive

and surgical care are readily available. Consultation

with pediatric hematology is recommended. Plastic

or vascular surgical consultation may be required.

d. Treatment of catheter-related thrombosis in neonates is still evolving. Current published guidelines

for treatment are based on common clinical practice, case studies, and extrapolation of principles of

therapy from adult guidelines (12,13).

e. Supportive care: Correct volume depletion, electrolyte abnormalities, anemia, thrombocytopenia,

treatment of sepsis.

f. Treatment is highly individualized and is determined by the site and extent of thrombosis, and the

degree to which diminished perfusion to the

affected extremity or organ affects function, and

the potential risk of bleeding complications associated with anticoagulant or thrombolytic therapy

(8,12,13).

g. Expectant management or “watchful waiting”—

close monitoring without anticoagulation or thrombolysis may be appropriate for some infants (1,12).

 

Jayashree Ramasethu

Management of Vascular Spasm

and Thrombosis

34

Intravascular arterial and venous catheters are associated

with significant risks of vascular thrombosis in newborn

infants (1,2). About 90% of neonatal venous thromboses are

associated with central venous catheters, although additional risk factors may be present (3).

A. Definitions

1. Vascular spasm is transient, reversible arterial constriction, often triggered by intravascular catheterization or

arterial blood sampling.

2. Thrombosis is the complete or partial obstruction of

arteries or veins by blood clot(s).

B. Assessment

1. Clinical diagnosis

a. The clinical signs associated with arterial or venous

thrombosis are shown in Table 34.1.

b. Vascular spasm of peripheral arteries is characterized by transient pallor, or cyanosis of the involved

extremity with diminished pulses and perfusion.

The clinical effects of vascular spasm usually last

<4 hours from the onset, but the condition may be

difficult to differentiate from more serious thromboembolism. The diagnosis of vasospasm of arteries is

usually made retrospectively after documentation of

the transient nature of ischemic changes and complete recovery of circulation (4) (Fig. 34.1 and 34.2).

c. Persistent bacteremia and thrombocytopenia are

nonspecific signs associated with vascular thrombosis at any site.

d. Clinical signs may be subtle or absent in many cases

of thrombosis, which may be detected incidentally

during ultrasonography for other indications.

2. Diagnostic imaging

a. Contrast angiography: Gold standard, gives best

definition of thrombosis but is difficult to perform in

critically ill neonates; requires infusion of radiocontrast material that may be hypertonic or cause undesired increase in vascular volume (3).

b. Doppler ultrasonography: Portable, noninvasive,

monitors improve over time, but may give both

false-positive and false-negative results compared

with contrast angiography (5).

3. Additional diagnostic tests

a. Obtain detailed family history in all cases of vascular thrombosis.

b. Laboratory testing for genetic thrombophilic disorder (Table 34.2) has been advocated, but its value is

debatable, particularly with catheter-related thrombosis in neonates (6–8). The tests do not influence

immediate management, and the volume of blood

required (4 to 6 mL) is a limitation. In addition,

protein-based assays are affected by age and by the

acute thromboembolic event and must be repeated

at 3 to 6 months of life before a definitive diagnosis

can be made.

C. Management of Arterial

Vascular Spasm

1. Warm contralateral extremity (reflex vasodilation).

2. Maintain neutral thermal environment for affected

extremity (i.e., keep heat lamps off area).

3. Maintain limb in horizontal position.

4. Correct hypotension or hypovolemia if present.

5. Consider removal of the catheter.

If mild cyanosis of the fingers or toes is noted after

insertion of an arterial catheter but peripheral pulses

are still palpable, a trial of reflex vasodilation with close

observation is reasonable, as vasospasm may resolve.

Continually assess the need for keeping the catheter in

place (i.e., the benefits of arterial access vs. the risk of

thrombosis and further complications.) A white or

“blanched” appearing extremity is an indication for

immediate removal of the catheter.

6. Topical nitroglycerine has been demonstrated to reverse

peripheral and umbilical artery catheter–induced ischemia in isolated case reports. Maintain good circulatory

volume. Monitor for hypotension and be prepared to

treat it immediately.

 

Chapter 33 ■ Extracorporeal Membrane Oxygenation Cannulation and Decannulation 223

9. Van Meurs KP, Mikesell GT, Seale WR, et al. Maximum blood

flow rates for arterial cannulae used in neonatal ECMO. ASAIO

Trans. 1990;36:M679.

10. Irish MS, O’Toole SJ, Kapur P, et al. Cervical ECMO cannula

placement in infants and children: recommendations for assessment

of adequate positioning and function. J Pediatr Surg. 1998;33:929.

11. Thomas TH, Price R, Ramaciotti C, et al. Echocardiography, not

chest radiography, for evaluation of cannula placement during

pediatric extracorporeal membrane oxygenation. Pediatr Crit Care

Med. 2009;10:56.

12. Neonatal ECMO Registry of the Extracorporeal Life Support

Organization (ELSO). Ann Arbor, MI: ELSO; 2011.

13. Rais-Bahrami K, Rivera O, Mikesell GT, et al. Improved oxygenation with reduced recirculation during venovenous extracorporeal membrane oxygenation: evaluation of a test catheter. Crit Care

Med. 1995;23:1722.

14. Rais-Bahrami K, Waltom DM, Sell JE, et al. Improved oxygenation with reduced recirculation during venovenous ECMO:

comparison of two catheters. Perfusion. 2002;17:415.

15. Paul JJ, Desai H, Baumgart S, et al. Aortic dissection in a neonate

associated with arterial cannulation for extracorporeal life support. ASAIO. 1997;43:92.

224

 

The decannulation procedure is the same as for the

venous catheter, with the exception that an inspiratory

hold that is not required.

20. Give protamine (1 mg IV) after removal of both catheters.

Administration of protamine is not mandatory if

there is no significant bleeding.

21. Irrigate the wound with sterile saline and cauterize any

bleeding sites.

22. If desired, pack the wound with a thrombin-soaked

absorbable gelatin sponge and close the neck incision

using subcuticular horizontal sutures of 4-0 Vicryl.

23. Remove the sutures holding the cannula behind the

right ear.

24. Place povidone–iodine ointment over the incision and

cover with semipermeable transparent dressing.

F. Complications

1. Vessel laceration, which may require a sternotomy for

correction

2. Excessive blood loss

3. Venous air embolus

References

1. O’Rourke PP, Crone RK, Vacanti JP, et al. Extracorporeal membrane oxygenation and conventional medical therapy in neonates

with persistent pulmonary hypertension of the newborn: a prospective randomized study. Pediatrics. 1989;84:957.

2. UK Collaborative ECMO Trial Group. UK Collaborative

Randomised Trial of Neonatal Extracorporeal Membrane

Oxygenation. Lancet. 1996;348:75.

3. Elbourne D, Field D, Mugford M. Extracorporeal membrane

oxygenation for severe respiratory failure in newborn infants.

Cochrane Database Syst Rev. 2002:CD001340.

4. Kanto WP, Shapiro MB. The development of prolonged extracorporeal circulation. In: Zwischenberger JB, Steinhorn RH, Bartlet

RH, eds. Extracorporeal Cardiopulmonary Support in Critical

Care. 2nd ed. Ann Arbor, MI: Extracorporeal Life Support

Organization; 2000:27.

5. Rais-Bahrami K, Short BL. The current status of neonatal extracorporeal membrane oxygenation. Semin Perinatol. 2000;24:406.

6. Bartlett RH, Roloff DW, Custer JR, et al. Extracorporeal life support: the University of Michigan experience. JAMA. 2000;283:904.

7. Rais-Bahrami K, Van Meurs KP. ECMO for neonatal respiratory

failure. Semin Perinatol. 2005;29:15.

8. Sutton RG, Salatich A, Jegier B, et al. A 2007 survey of extracorporeal life support members: personnel and equipment. J Extra

Corpor Technol. 2009;41:172.

Fig. 33.10. Placement of Satinsky vessel clamp prior to removal

of ECMO catheter.

 

E. Technique

Postdecannulation vessel reconstruction is beyond the

scope of this chapter.

1. Place the neck in an extended position, using the

shoulder roll.

2. Give fentanyl for analgesia, prior to giving vecuronium.

Because of the risk of air embolism during the

removal of the venous catheter, the infant must not be

allowed to breathe during decannulation. If two doses

of vecuronium do not produce paralysis, give pancuronium.

3. Increase ventilator setting to a rate of 40 to 50 breaths/

min, a peak inspiratory pressure of 20 to 25 cm H2O

222 Section V ■ Vascular Access

(depending on chest movement), and FiO2 of 0.30 to

0.40 after paralytic agent is given.

4. Clean the neck, and drape as for cannulation.

5. Anesthetize with 0.25% lidocaine with epinephrine.

6. Cut and remove the Vicryl suture.

7. Remove absorbable gelatin sponge packing, exposing

the catheters and vessels.

If a jugular bulb catheter is in place, it is usually

removed first to allow better visualization for removal

of the VV ECMO catheter.

8. The jugular bulb catheter should be clamped off before

removal, after the patient is taken off bypass. Be aware

that removing the catheter while on bypass without a

clamp in place will result in the introduction of air into

the circuit.

In case of VA ECMO, the venous catheter is usually

removed first because it is most readily accessible.

9. Separate the catheter from surrounding tissue by blunt

dissection.

10. Encircle the vein with a 2-0 silk tie, which is used for

traction and hemostatic control.

11. Place a Satinsky clamp around the vein to stabilize the

catheter (Fig. 33.10).

12. Place a 2-0 silk tie proximal to the clamp.

13. Cut the silk ties securing the catheter in the vein with a

no. 11 scalpel blade. The two proximal ties should be

cut where they cross the vessel loop (“bootie”).

14. Ask the ECMO specialist to remove the patient from

the ECMO circuit.

15. Monitor vital signs and oxygen saturation as an indication that ventilator settings are appropriate. Settings

may have to be increased when the patient is removed

from the circuit.

16. Provide an inspiratory “hold” on the ventilator while

the surgeon removes the venous catheter. Failure to do

this can result in air embolus.

17. Replace any significant blood loss.

18. Cut the 2-0 silk traction suture and tie the suture

proximal to the Satinsky clamp. Remove the Satinsky

clamp.

19. Isolate the arterial catheter, dissect free, and remove.

 

Chapter 33 ■ Extracorporeal Membrane Oxygenation Cannulation and Decannulation 221

2. Aortic dissection associated with arterial cannulation

(15).

3. Blood loss, particularly during the venous cannulation,

when side holes in the catheter are outside the vein

4. Venous spasm, resulting in inability to place a large

enough venous catheter to meet the required ECMO

flow to support the patient adequately

The rate of blood flow is impeded by the small

gauge of the catheter, requiring that a second venous

catheter be placed in the femoral vein. The two catheters must be Y-connected together into the ECMO

circuit.

5. Arrhythmias and/or bradycardia can occur, owing to

stimulation of the vagus nerve

6. Hypotension, due to an increase in the intravascular

space when the patient is connected to the ECMO

circuit

7. Conversion to VA from VV ECMO. This will occur if

a. The patient remains hypoxic despite adequate

ECMO flow.

b. The patient remains hypotensive despite vasopressor

support.

c. Cerebral venous saturations remain persistently

<60% after adequate flows and ventilator management have been undertaken.

Converting from VV to VA ECMO requires cannulation of carotid artery with a Bio-Medicus arterial catheter, and the double-lumen VV catheter

must be “Y’d” in together to make a double-lumen

venous drainage catheter (Fig. 33.9).

Extracorporeal Membrane

Oxygenation—Decannulation

A. Indications

1. Removal from ECMO after lung recovery

2. Removal from ECMO because of a complication such

as uncontrolled bleeding or failure of lung recovery

B. Contraindications

All intensive support is being withdrawn, and permission for

autopsy is obtained. It is usually optimal to remove the catheters during the autopsy.

C. Precautions

1. The patient must be paralyzed during the removal of

the venous catheter to avoid an air embolus.

2. The vessels are fragile and may tear. A backup unit of

blood should be available at the bedside.

3. Delay removing catheter for 12 to 24 hours after taking

the patient off bypass in cases in which there is a high

risk of reoccurrence of pulmonary hypertension and

thus need for second ECMO run (e.g., severe congenital diaphragmatic hernia). This procedure places a risk

of development of right atrial clots from the venous

catheter and, in some patients, has resulted in superior

venocaval syndrome. Therefore, the time the catheters

are left in place should be limited to no more than

24 hours.

D. Personnel, Equipment,

and Medications

Personnel

Same as for cannulation, with the exception that the primer

is not required

Equipment

Sterile

1. Surgical tray with towels and suture as for cannulation

2. Semipermeable transparent dressing

3. Povidone–iodine ointment

4. Syringes (1 to 20 mL) and needles (18 to 26 gauge)

5. Unit of blood

6. Absorbable gelatin sponge

Nonsterile

Same as for cannulation

Medications

1. Fentanyl (10 to 20 μg/kg)

2. Vecuronium bromide (0.2 mg/kg)

3. A short-acting paralyzing agent is preferred because of

the relatively short duration of the procedure. This

allows the infant to breathe spontaneously as soon as

possible after decannulation, which facilitates rapid

weaning from ventilator support.

4. Lidocaine, 0.25%, with epinephrine

5. Topical thrombin

6. Protamine sulfate (1 mg only)

 

a. Do not squeeze the tubing while attaching; air will

enter when the tubing is released.

b. If air is seen in the tubing, the catheters must be disconnected from the circuit. Prior to reconnection,

air is removed, and the catheters are reconnected as

described in E1.

2. Remove all sterile tubing clamps from the catheters,

and have a nonsterile assistant hold the catheters.

Nonsterile tubing clamps remain in place on the arterial and venous sides of the circuit at this juncture.

3. Place the patient on ECMO by removing the arterial

clamp, placing a clamp on the bridge (Fig. 33.9A), and

removing the venous clamp. This will remove all nonsterile clamps from the circuit.

Many centers are now using a “bloodless bridge”

that has sterile-heparinized saline with stopcock design;

thus, a clamp on the bridge is not necessary. The bridge

is left closed with the stopcock mechanism during cannulation so that only the clamps on the catheters need

to be removed.

4. Increase ECMO flow in 50-mL increments over 20 to

30 minutes, until adequate oxygenation is achieved

(usually at 120 mL/kg/min).

Transfusion may be needed if hypotension occurs at

this stage.

5. Decrease the ventilator settings and oxygen concentration gradually as the ECMO flows are increased.

Typical resting ventilator settings for VA ECMO

are at a rate of 10 to 15 breaths/min, a peak pressure

220 Section V ■ Vascular Access

limit of 15 to 20 cm H2O, and FiO2 of 0.21 to 0.30.

For VV ECMO, it is recommended to keep ventilator

settings at a rate of 20 to 30 breaths/min, a peak inspiratory pressure of 20 to 25 cm H2O, and FiO2 of 0.30

to 0.35.

F. Closure of the Neck Wound

1. Obtain radiographic confirmation of appropriate catheter position and achievement of an adequate flow rate

through the ECMO circuit prior to closure of the neck

wound.

2. Cut and remove traction sutures.

3. Approximate the skin with a running 4-0 Vicryl

(Ethicon) suture on an atraumatic needle.

4. Tie the Vicryl suture, and use the tails of the suture to

secure each catheter.

5. Tie catheters together with another silk tie.

6. Anesthetize the area behind the ear with 0.25%

Xylocaine with epinephrine.

7. Use 2-0 silk suture on a noncutting needle to place a

stitch behind the ear and tie around the catheter

to secure in place. Place a separate stitch for each

catheter.

8. Tie catheters together, dress the incision with povidone–

iodine ointment, and cover the area with semipermeable membrane dressing.

9. Secure the circuit tubing securely to the bedside to

reduce traction on the catheters.

G. Complications

1. Torn vessels, more commonly the vein

a. This risk is decreased if 6-0 Prolene stay sutures are

always used.

b. Do not attempt to use too large a catheter.

Fig. 33.9. Schematic view of converting from VA (A) to VV (B) ECMO. The double-lumen VV catheter

is “Y’d” together to make a double-lumen venous drainage catheter.

 

Chapter 33 ■ Extracorporeal Membrane Oxygenation Cannulation and Decannulation 219

A. Double-Lumen VV Catheters

1. Kendall 14-Fr catheter (Kendall Health Care Products,

Mansfield, Massachusetts)

2. OriGen 12-, 15-, and 18-Fr catheters (OriGen

Biomedical, Austin, Texas)

3. Avalon Elite DLC, 13- to 31-Fr catheter (Avalon

Laboratories LLC, Rancho Dominguez, California)

Note: The Avalon catheter requires insertion under

ultrasound or fluoroscopy guidance; refer to company

recommendations at www.avalonlabs.com

B. Advantages of VV Bypass

1. Provides excellent pulmonary support

2. Avoids carotid artery ligation

3. Oxygenated blood enters pulmonary circulation.

4. Particles coming from the ECMO circuit enter the

venous circulation instead of the arterial circulation.

C. Disadvantages of VV Bypass

1. Lack of cardiac support

2. ECMO support is dependent on the patient’s cardiac

function.

3. Catheter position and rotation are extremely critical.

4. Amount of recirculation

D. Cannulation Technique

The cannulation technique for VV ECMO is essentially

the same procedure as venous cannulation for VA ECMO,

with the following exceptions.

1. Both internal jugular vein and carotid arteries are identified and dissected free, although the internal jugular

vein is the only vessel cannulated with the doublelumen VV catheter. Both vessels are isolated in case a

rapid conversion to VA bypass becomes necessary. A

silastic loop may be tied loosely around the artery to

facilitate potential conversion to VA flow.

2. The cannula is advanced with the lumen, which will

carry oxygenated blood (“arterial side”) upward and

anterior to the venous side of the double-lumen

(Fig. 33.8).

Caution: Avoid bending the catheter or creating a

“crimp” in the catheter.

Correct positioning of the catheter helps direct the

oxygenated blood return toward the tricuspid valve,

thus minimizing the recirculation of the oxygenated

blood back to the ECMO circuit.

3. The proximal end of the internal jugular vein is also

cannulated for cephalad drainage, that is, a jugular

bulb catheter. This catheter is connected to the venous

tubing of the ECMO circuit via a Luer connector. For

this, we use a custom-made Carmeda heparin-coated

Bio-Medicus venous catheter, made specifically for use

as a cephalad catheter.

This allows additional venous drainage to the

ECMO circuit, prevents venous congestion, and also

allows for cephalic venous saturation measurement.

4. If using a jugular bulb catheter to measure cerebral

saturations, care should be used when entering the circuit; air will draw into the venous side of the circuit

rapidly if a stopcock is loose or is left open.

E. Placing Patient on the Extracorporeal

Membrane Oxygenation Circuit

The circuit has been previously primed with packed cells/

albumin. The priming procedure and the surgical placement of the ECMO catheters should be timed so that the

two are completed at the same time. Priming of the circuit

is beyond the scope of this chapter.

1. Fill catheters with sterile saline. Connect them to the

ECMO circuit by inserting the 0.25- × 0.25-inch connectors into the tubing as the assistant drips sterile

saline into the ends of the circuit tubing and the catheter, to ensure that all residual air is eliminated prior to

connection.