Intra Aortic Balloon Pump (IABP) Yan Wing Wa Department of Intensive Care Pamela Youde Nethersole Eastern Hospital Spring 2009

What is an IABP? The Intra-Aortic Balloon Counterpulsation system is a volume displacement device. It should be positioned so that the tip is approximately 1 to 2 cm below the origin of the left subclavian artery and above the renal arteries. On chest x-ray the tip should be visible in the 2nd or 3rd intercostal space.

Purpose of IABP Hemodynamic support in medical conditions Prophylactic hemodynamic support Cardiac support for hemodynamically challenged patients with mechanical defects PRIOR to correction Hemodynamic support in medical conditions such as: Cardiogenic Shock Threatening Extension of MI Unstable Angina Intractable Ventricular Dysrhythmias Septic Shock Syndrome Cardiac Contusion Prophylactic hemodynamic support for: Coronary Angiography Coronary Angioplasty Thrombolysis High-risk interventional procedures (stents) Cardiac support for hemodynamically challenged patients with mechanical defects PRIOR to correction: Valvular Stenosis Mitral Valve Insufficiency Ruptured Papillary Muscle Ventricular Septal Defect (VSD) LV Aneurysm Bridging Device to other mechanical assist, such as Ventricular Assist Device (VAD) Support During Transport

Surgical Indications Post surgical myocardial dysfunction Support for weaning from cardiopulmonary bypass (CPB) Cardiac support following correction of anatomical defects Maintenance of graft patency post CABG Pulsatile flow during CPB

IABP Kit Contents Introducer needle Guide wire Vessel dilators Sheath IABP (34 or 40cc) Gas tubing 60-mL syringe Three-way stopcock Arterial pressure tubing (not in kit)

IAB Sizing Chart The IAB Should be selected according to the following chart (chart located on every box). Note: The 50cc balloons are no longer made by Datascope 6

Insertion Techniques Percutaneous Surgical insertion Sheath less Femoral cut down Trans-thoracic

Positioning The end of the balloon should be just distal to the takeoff of the left subclavian artery Position should be confirmed by fluoroscopy or chest x-ray

Insertion Position On chest x-ray the tip should be visible in the 2nd or 3rd intercostal space

Pressure Waveforms Red wave = normal arterial pressure trace                                                                                                                                                  DEFLATED INFLATED Red wave = normal arterial pressure trace Blue wave = arterial pressure trace on IABP

Desired Outcome Appropriately timed blood volume displacement (30 – 50 mL) in the aorta by the rapid shuttling of helium gas in and out of the balloon chamber, resulting in changes in inflation and deflation hemodynamics

Inflation The goal of inflation is to increase or augment perfusion The principles of counterpulsation state that the balloon should be inflated at the start of diastole, just prior to the Dicrotic Notch. Aortic volume and pressure are increased through displacement principles causing: Increased coronary perfusion pressure Increased systemic perfusion pressure Increased O2 supply to both the coronary and peripheral tissue Increased baroreceptor response Decreased sympathetic stimulation causing decreased Heart Rate, decreased Systemic Vascular Resistance, and increased Left Ventricular function

Inflation of IABP Results In: Increased coronary perfusion pressure Increased systemic perfusion pressure Increased O2 supply to both the coronary and peripheral tissue Increased baroreceptor response Decreased sympathetic stimulation causing decreased HR, decreased SVR, and increased LV function

Deflation The goal of deflation is to reduce LV workload Deflation creates a "potential space" in the aorta, reducing aortic volume and pressure The principles of counterpulsation state that the balloon should be deflated at the start of systole, during Isovolumetric Contraction.

Deflation of the IABP Results In: Afterload reduction and therefore a reduction in MVO2 Reduction in peak systolic pressure, therefore a reduction in LV work Increased cardiac output Improved ejection fraction and forward flow

How do you Know? Afterload reduction? Change in diastolic pressures Unassisted and assisted Decreased workload? Change in systolic pressures Improved cardiac output? Increase in pulse pressures

Review of Arterial Pressure Landmarks AVO = Aortic valve opens, beginning of systole PSP = Peak systolic pressure, 65-75% of stroke volume has been delivered DN = Dicrotic notch, signifies aortic valve closure and the beginning of diastole AEDP = Aortic end diastolic pressure

IABP Waveform Zero baseline (on console) Balloon pressure baseline Rapid inflation Peak inflation artifact Balloon pressure plateau (IAB fully inflated) Rapid deflation Balloon deflation artifact Return to baseline (IAB fully deflated) Duration of balloon cycle

Inflate just prior to the dicrotic notch To accomplish the goals of inflation, the balloon must be inflated at the onset of diastole The result of properly timed inflation is a pressure rise during diastole The PDP/DA influences the gradient for coronary artery perfusion

Review of Arterial Pressure Landmarks in 1:2 Assist Patient AEDP PSP (unassisted systole) PDP/DA (diastolic augmentation) Balloon AEDP APSP (assisted systole) PAEDP = Patient aortic end diastolic pressure, this is the patient's unassisted diastole PSP = Peak systolic pressure, this is the patient's unassisted systole PDP/DA = Peak diastolic pressure or diastolic augmentation, this is the pressure generated in the aorta as the result of inflation BAEDP = Balloon aortic end diastolic pressure, this is the lowest pressure produced by deflation of the IAB APSP = Assisted peak systolic pressure, this systole follows balloon deflation and should reflect the decrease in LV work

Inflation Hemodynamics Coronary artery blood flow and pressure are increased Increased renal and cerebral blood flow Increased diastolic pressure increases perfusion to distal organs and tissues

Inflation Hemodynamics Coronary collateral circulation is potentially increased from the increase in coronary perfusion pressure (CPP) Systemic perfusion pressure is increased

Coronary Perfusion Pressure The pressure at which blood perfuses through the coronary circulation, mainly in diastole Blood flow to the left ventricle occurs principally during diastole and is largely determined by the driving pressure (diastolic pressure minus left ventricular diastolic pressure), the diastolic interval and the state of coronary vasodilatation The major vessels of the coronary circulation are the left main coronary that divides into *left anterior descending* and *circumflex* branches, and the right main coronary artery. The *left and right coronary arteries* originate at the base of the aorta from openings called the *coronary ostia* located behind the aortic valve leaflets. The left and right coronary arteries and their branches lie on the surface of the heart, and therefore are sometimes referred to as the *epicardial coronary vessels*. These vessels distribute blood flow to different regions of the heart muscle. When the vessels are not diseased, they have a low vascular resistance <../Hemodynamics/H002.htm> relative to their more distal and smaller branches that comprise the microvascular network <../Microcirculation/M014.htm>. As in all vascular beds, it is the small arteries and arterioles in the microcirculation that are the primary sites of vascular resistance, and therefore the primary site for regulation of blood flow. The arterioles branch into numerous capillaries that lie adjacent to the cardiac myocytes. A high capillary-to-cardiomyocyte ratio and short diffusion distances ensure adequate oxygen delivery to the myocytes and removal of metabolic waste products from the cells (e.g., CO_2 and H^+ ). Capillary blood flow enters venules that join together to form cardiac veins that drain into the *coronary sinus* located on the posterior side of the heart, which drains into the right atrium. There are also *anterior cardiac veins* and *thesbesian veins* drain directly into the cardiac chambers. Although there is _considerable heterogeneity_ among people, the following table indicates the regions of the heart that are generally supplied by the different coronary arteries. This anatomic distribution is important because these cardiac regions are assessed by 12-lead ECGs <../Arrhythmias/A013.htm> to help localize ischemic or infarcted regions, which can be loosely correlated with specific coronary vessels; however, because of vessel heterogeneity, actual vessel involvement in ischemic conditions needs to be verified by coronary angiograms or other imaging techniques. *Anatomic Region of Heart* *Coronary Artery (most likely associated)* Inferior Right coronary Anteroseptal Left anterior descending Anteroapical Left anterior descending (distal) Anterolateral Circumflex Posterior Right coronary artery

Deflation Hemodynamics The pressure that the LV must generate (afterload) is less throughout the systolic phase Decreases myocardial O2 demands Isovolumetric contraction (IVC) phase of systole is shortened

Deflation Hemodynamics Reduced afterload allows the LV to empty more effectively so stroke volume (SV) is increased Enhanced forward cardiac output decreases the amount of blood shunted from left to right in cases of intraventricular septal defects and incompetent mitral valve

Triggering It is necessary to establish a reliable trigger signal before balloon pumping can begin The computer in the IAB console needs a stimulus to cycle the pneumatic system, which inflates and deflates the balloon The trigger signal tells the computer that another cardiac cycle has begun

Triggering In most cases it is preferable to use the R wave of the ECG as the trigger signal There are other trigger options for instances when the R wave cannot be used or is not appropriate

Trigger Loss The console MUST see a trigger to initiate an inflate/deflate cycle If no trigger is seen when the clinician attempts to start pumping, no pumping will occur and an alarm will be sounded If the trigger is lost after pumping starts, no further pumping will occur until a trigger is re-established The pump will go to STANDBY and an alarm will be sounded

Trigger Loss If the current trigger is lost the clinician can choose an alternate, available trigger to resume pumping For example, if the ECG lead becomes disconnected the arterial pressure (AP) trigger may be selected until the ECG is re-established

ECG Trigger Since triggering on the R wave of the ECG is preferred, it is very important to give the IABP a good quality ECG signal and lead

Poor ECG Choices Note: changing QRS morphology may cause wandering timing Note: tall T waves may cause double triggering or may alter previously set timing points Note: wandering baseline may cause skipped trigger Note: artifact may cause inappropriate triggering 

ECG Gain In addition to selecting a lead with a QRS morphology that provides consistent, appropriate triggering, it is important to ensure the QRS complex has adequate amplitude The computer has a minimum height requirement to recognize the initial deflection as an R wave, whether upright or negative in configuration

Triggering on the Arterial Pressure Waveform Arterial pressure provides another signal to the IABP to determine where the cardiac cycle begins and ends It is used when the ECG has too much interference from patient movement or poor lead connection There are limitations to triggering on the arterial pressure curve AP trigger should be considered a backup trigger and not the one used as the primary trigger The PDP/DA influences the gradient for coronary artery perfusion Irregular heart rates and irregular pulse pressures can cause the pump to not see a trigger where it expects to find one If this happens, pumping will be temporarily interrupted as the computer relearns the parameters Late deflation will also cause missed triggers and an interruption in pumping

CPR AP trigger is the appropriate choice during CPR Once chest compressions are started an arterial pressure waveform will be generated Triggering on the AP will produce pumping in synchrony to chest compression and has been shown to assist with coronary and carotid perfusion CPP less than 15 will not allow return of spontaneous rhythm

TRIGGER MODES: ECG In most instances this is the trigger of choice. The computer analyzes the SLOPE and HEIGHT of a positively or negatively deflected QRS complex. Rejects pacer spikes on the basis of sharp rising edge. Automatically initiates ARRHYTHMIA TIMING when at least 8 out of 16 beats are detected as irregular.

TRIGGER MODES: ECG In AUTOPILOT mode, if no QRS or AP trigger is found, it will trigger on the V SPIKE of an AV paced rhythm. In OPERATOR mode, the ECG trigger key can be used to toggle between triggering on the R WAVE and the V SPIKE of a V or AV paced rhythm.

TRIGGER MODES: ARTERIAL PRESSURE (AP) The computer uses the SYSTOLIC UPSTROKE of an arterial pressure waveform as the trigger signal. A 14mmHg minimum pulse pressure is required to initially recognize the trigger. Once pumping begins the subsequent pulse pressure requirement is reduced to 7mmHg. Every 64th beat is unassisted and reassessed. This mode is available as an option for clinical situations where an ECG is unavailable or distorted. Not recommended for irregular rhythms or irregular pulse pressures.

Gas Alarms/Balloon Pressure Waveform During a cycle of inflation/deflation, helium is rapidly moved in and out of the balloon. The environment within the balloon and the surrounding forces that affect balloon behavior all contribute to a predictable pattern of gas flow and pressure. The gas pressure characteristics are converted into a waveform that is reflective of the behavior of the gas.

This transduced waveform tells much about the interaction of the balloon within the patient's aorta. Understanding the balloon pressure waveform is important for troubleshooting of the console as most alarms are based on the gas surveillance system.

IABP Waveform Zero baseline (on console) Balloon pressure baseline Rapid inflation Peak inflation artifact Balloon pressure plateau (IAB fully inflated) Rapid deflation Balloon deflation artifact Return to baseline (IAB fully deflated) Duration of balloon cycle

Normal Waveform Variations Tachycardia Bradycardia Hypertension Hypotension

Abnormal Waveform Variation: Wide Inflation and/or Deflation Artifact Check for kinks, as they may trap gas in the IAB. If water is present in the gas tubing, remove the condensation. Pushing the helium through the water during inflation and deflation slows down gas transition. If gas transition is prolonged too much, it can create alarms.

Abnormal Waveform Variation: Helium Loss / Gas Loss / Gas Leakage Alarms Observe for blood in the gas tubing. If even a slight amount is present, it may indicate a balloon rupture. Do not resume pumping. Notify physician immediately and prepare for IAB removal. Check connections where gas tubing connects to IAB and to pump. Secure if loose.

Abnormal Waveform Variation: High Pressure / Kinked Line Alarm Note that the plateau pressure is still greater than 250mmHg when it is time to deflate. This indicates that not all of the gas could enter the balloon. It is generally due to a kink in the catheter, either internal to the patient or external.

Reposition patient. Keep affected leg straight. Use rolled towel under hip to hyperextend hip. Apply slight traction to the catheter if kinking at the insertion site or in the artery is suspected. The distal portion of the IAB may be in the sheath if a long introducer sheath was used. Pull sheath back until IAB bladder has exited the sheath. Introducer sheath may be kinked which in turn is kinking the balloon. Suspect this particularly if placement of the sheath was difficult. Pull sheath back or rotate sheath a partial turn.

Check placement of the balloon; it may be too high or too low. IAB may be partially wrapped if alarm occurs shortly after insertion. Take steps to facilitate unwrapping (consult IAB manufacturer). The balloon may be too large for the patient. Reduce the helium volume the balloon is inflated with. (It is recommended to not reduce the volume below 2/3 of maximum. For example, do not decrease volume in a 40cc IAB below 27cc)

Abnormal Waveform Variation: High Baseline / Fill Pressure Check for intermittent obstruction of gas lumen. Check for overfill of system. This condition may occur during ascent in air transport since gas expands as you go up in altitude. Reset the alarm and restart pumping. The volume will be adjusted automatically for current barometric pressure. In AutoCAT® or TransAct® the vent valve may be malfunctioning. In the AutoCAT, ensure that the tubing to the condensation bottle (located behind the helium tank) is not kinked.

Complications of IABP The following patients are at the greatest risk of developing complications associated with IABP: Females, diabetics, smokers, obese patients Patients with PVD, HTN, high SVR, shock

Complications of IABP Aortic wall dissection, rupture or local vascular injury Care as indicated Emboli: thrombus, plaque or air Treatment of an air embolism is as follows: 100% oxygen, intubate, Trendelenberg in left lateral decubitus position, fluid resuscitation, etc. Administer 100% oxygen and intubate for significant respiratory distress or refractory hypoxemia. Oxygen may reduce bubble size by increasing the gradient for nitrogen to move out. Promptly place patient in Trendelenburg (head down) position and rotate toward the left lateral decubitus position. This maneuver helps trap air in the apex of the ventricle, prevents its ejection into the pulmonary arterial system, and maintains right ventricular output. Maintain systemic arterial pressure with fluid resuscitation and vasopressors/beta-adrenergic agents if necessary. Consider transfer to a hyperbaric chamber. Potential benefits of this therapy include (1) compression of existing air bubbles, (2) establishment of a high diffusion gradient to speed dissolution of existing bubbles, and (3) improved oxygenation of ischemic tissues and lowered intracranial pressure. Circulatory collapse should be addressed with CPR and consideration of more invasive procedures as described above.

Complications of IABP IABP Rupture: COFFEE GROUNDS seen in the drive line is a precursor to a rupture (make sure they are on the inside and not the outside of the tubing) NOTIFY PHYSICIAN!!!!! IF THERE IS A FLAGRANT RUPURE OF THE IABP CLAMP THE GAS LINE!!!!!

Complications of IABP Infection Check catheter insertion site often STRICT ASEPTIC TECHNIQUE Restrict movement while IABP in place

Complications of IABP Obstruction Malposition Too high – obstruction of left subclavian and carotids CHECK LEFT RADIAL ARTERY PULSE Too low – obstruction of renal and mesenteric arteries MONITOR URINE OUTPUT

Complications of IABP Compromised circulation due to catheter Ischemia Routine nursing care and monitoring Compartment syndrome Rare complication seen in the LE, usually related to infection Monitor calf circumference

Complications of IABP Hematologic ALL PATIENTS typed & crossmatched!!! Bleeding REMOVE THE DRESSING!!! PUT ON STERILE GLOVES!!! HOLD PRESSURE!!! Thrombocytopenia Routine monitoring

Weaning of IABP Timing of weaning Decreasing inotropic support Patient should be stable for 24-48 hours Decreasing inotropic support Decreasing pump ratio From 1:1 to 1:2 or 1:3 Decrease augmentation Monitor patient closely If patient becomes unstable, weaning should be immediately discontinued Weaning should only be attempted on order of a physician.

IAB Removal Discontinue heparin six hours prior Check platelets and coagulation factors Deflate the balloon Apply manual pressure above and below IABP insertion site Remove and alternate pressure to expel any clots Apply constant pressure to the insertion site for a minimum of 30 minutes Check distal pulses frequently IAB should only be pulled by a physician or the cardiac P.A.

Thank you for your attention