Intra-aortic counter pulsation

The aim of intra-aortic counterpulsation is to balance myocardial oxygen supply to meet metabolic demands of the myocardium.

Supply refers to

· coronary artery anatomy

· diastolic pressure

· diastolic time

Demand refers to

· heart rate

· afterload

· preload

· contractility

Left ventricular failure is

l a series of physiological changes occurring as a result of injury, which will result in an imbalance between supply and demand

l CO falls resulting in decreased supply

l preload, afterload and heart rate increase in an attempt to compensate, resulting in increased demand

l as LVF progresses, a greater imbalance between supply and demand results in further pump failure

Intra-aortic counter pulsation influences

· cardiac output

· systemic vascular resistance

· ejection fraction

IACP indications

l refractory ventricular failure

l cardiogenic shock

l unstable refractory angina

l impending infarction

l mechanical complications due to acute myocardial infarction

l ischaemia related intractable ventricular arrhythmias

l cardiac support for high risk general surgical patients and coronary angiography/angioplasty patients

l septic shock

l weaning from CPB

l support for failed angioplasty

IACP contra-indications

· severe aortic insufficiency

· abdominal aortic aneurysm

· severe calcified aorto-iliac disease

· peripheral vascular disease

· sheathless insertion not recommended in obese patients

IACP clinical considerations

Insertion

Catheter equipment

One sterile kit includes 1x18 gauge angiographic needle, guide wire, dilators x 2, introducer sheath with haemostasis valve, 60cc syringe, male luer lock plug, 90 cm pressure tubing, 1x datascope connector and the balloon catheter.

NB. Size is important. 40 cc catheter for patients > 5’4”(165 cm) and 35 cc catheter for patients <> 165 cm)

Monitoring

l Monitor half hourly HR MAP CVP PAP PCWP

l Monitor hourly

degree of diastolic augmentation

degree of afterload reduction

haemodynamic profile using cardiac output studies

neurovascular status

neurological status

renal function

insertion site for bleeding

l Monitor daily

biochemistry/ bleeding/ clotting studies

IABP

· maintain optimal augmentation and afterload reduction

· note placement of IABP on daily chest x-ray

· zero transducer 8 hourly and prn

· IABP autofills 2hrly

IABP management in cardiac arrest

*Patient can be safely defibrillated in the event of VT, VF with the IABP on standby

· select standby mode

· defibrillate according to protocol

· select assist mode

In the event of circulatory collapse necessitating external cardiac massage

· select pressure triggered mode

· the inflation trigger is the pressure generated be ECM

Special treatment needs

· note and record quality of pedal pulses 1 hourly

· utilize pressure reducing mattress

· maintain anti - coagulant protocol with low dose

heparinization

· observe for complications of IABC

Fluid balance management

l 1 hourly assessment

Activity

· bed rest/log rolls

· do not elevate HOB > 30%

· do not flex balloon leg

· ROM uninvolved extremity

· dorsiflexion balloon leg

Diet

l as tolerated

l supplemental nutritional support

l N/E tube feeds

Triggering

The trigger for inflation is either the ECG, A-V or V pacing spike or the aortic pressure curve recorded at the tip of the IABC

ECG triggering

· preferably select the lead with the largest QRS complex

· persistent arrhythmias, tachyarrhythmias can make timing difficult

· efforts should be made to suppress arrhythmias and treat tachycardia

· in rapid atrial fibrillation position deflation point to extreme right

AV and V triggering:

· patient must be fully paced in this mode

· in intermittent pacing, select ECG trigger

Pressure triggering:

· use when atrial pacemaker spike interpreted as QRS complex

· use in transport when artifact interferes with triggering

Timing

Initially timing can be based on the ECG. The balloon is inflated at the peak of the T-wave (end systole) and deflated during the pr interval (end diastole). Fine tuning is then based on the aortic pressure waveform.

Inflation

· occurs at the dicrotic notch, indicative of aortic valve closure

Deflation

· occurs just before the aortic valve opens. Deflation should be timed to achieve the lowest presystolic pressure possible

Transport

Transport patients in the pressure wave triggering mode

Respiratory therapy

l evaluate breath sounds

l routine respiratory care

l modified respiratory therapy

Daily/prn lab work

l monitor K, se Cr, platelets, INR, clotting times

l CKMB, serial ECG

l ABG 4hrly

l blood/urine/sputum cultures if T > 39

Weaning

When haemodynamics improve, inotropic support is < style="">

· weaning by decreasing the ratio of unassisted to augmented beats from 1:1 to 1:3

· weaning by decreasing the degree of balloon augmentation from 100% to 30%

· anticoagulation to cease 4 hours prior to removal

· return to normal coagulation parameters

· patient to be independent of counterpulsation (30% augmentation) for at least five hours prior to removal of IABC

· serial haemodynamic profile to ascertain response to weaning

· observe clinical status to monitor tolerance to weaning

Removal

Removal of IABC necessitates return to theatre if balloon was inserted surgically under direct vision. Catheters inserted percutaneously, using the Seldinger technique, may be removed in the ICU setting using strict asepsis.

l IABP to standby

l balloon is deflated

l sheath and catheter removed simultaneously

l firm pressure applied to insertion site for 30 minutes or until all bleeding ceases

l pressure bag applied to insertion site for further 4-6 hrs

l observation of neurovascular status for 24 hours

Complications

Limb ischaemia:

l check distal pulses, colour, temperature 1 hourly

l use smallest sizes

l evaluate risk factors ( female, diabetic, PVD)

l select limb with best pulse

l remove sheath

l subcutaneous xylocaine for arterial spasm

l change insertion site

l bypass graft the femoral artery

l excessive bleeding from insertion site

l thrombocytopenia ( daily platelet count)

l balloon leak (remove IAC)

l infection (local or systemic)

l aortic dissection

l shoulder tip pain

l compartment syndrome (fasciotomy )