Post Cardiac Surgery Intensive Care

Anwar Murad

Cardiac Surgery

• Each of these procedures are done by the cardiac surgeon and usually share the same technical concerns during the operation– Coronary Artery Bypass Graft– Valvular repair/replacement– Aortic root repair/replacement– Repair of congenital/acquired defects– Resection of cardiac tumors

• In order to maintain a bloodless field for surgery, these patients are put “on pump”– Cardiopulmonary bypass

Cardiac Surgery

• Cannulas are inserted into the right atrium and aorta

• The aorta is clamped to prevent blood entering heart

• Blood pumped through oxygenator from right side and returned into aorta

• Cardioplegia induced with potassium rich solution and hypothermia (<32 C)

Cardiac Surgery

• The patient is anticoagulated during the pump run– ACT is measured to titrate heparin infusion

• The longer the pump run, the more likely complications will develop– Vasoplegia– Coagulopathies– Cardiac dysfunction– Multi Organ failure

• When the patient comes off pump, he may be on several inotropic agents and vasoactive medications

In the ICU• The anesthetist and surgeon will transfer and sign over the patient to the intensivist• The intensivist will the collect the following information

– Age– Sex– Prior medical history

• Medications• Allergies

– Type of surgery– Indication and urgency of operation– Coronary angiogram– Pre op echocardiogram and post op echocardiogram– Airway concerns– Pump time and cross clamp time– Operation success and complications– Current inotropes and vasoactive medications– Pacing requirement– Surgical concerns

In the ICU

• The intensivist will assess the patient– Neuro exam once awake to make sure no neurological deficit– Initial hemodynamics and rhythm

• HR/MAP/CVP/PA pressures/Wedge Pressure/Cardiac Index• Peripheral pulses• Auscultate the chest to rule out murmurs and rub

– Confirm ETT position by auscultation• Assess oxygen saturation via oximetry

– Examine abdomen– Assess lines, IABP, chest drains to make sure they are

functional

In the ICU

• The following labs and investigations will be requested– CBC

• To assess hemoglobin, platelets– Especially if bleeding

– Urea and electrolytes• To assess if any kidney injury has occurred• Electrolyte abnormalities need to be corrected to prevent dysrhythmias

– Potassium and magnesium especially

– Glucose• Glycemia needs to be controlled to prevent further post op complications

– Coagulation profile– Cardiac enzymes

• Usually will be abnormal initially but should decline over time

– ABG/VBG• Ensure good oxygenation and ventilation• Look for lactic acidosis• Mixed venous saturation should be >50% to confirm adequate oxygen delivery is

maintained

– ECG• Should be compared to pre op ECG• Ensure no new changes

– RBBB is the most common finding and not usually significant– Look at underlying rhythm– ST elevation in two contiguous leads may be due to acute graft failure

» THIS IS A CRITICAL EVENT– Diffuse ST elevations and PR depression is indicative of pericarditis

– CXR• Confirm placement of ETT, central lines, NGT, and chest tubes• Rule out effusions and pneumothorax

In The ICU

• Acutely, the following issues will need to be addressed– Hypothermia

• Patient needs to be rewarmed, as hypothermia predisposes to bleeding, cardiac dysfunction, vasoconstriction, increased oxygen consumption due to shivering

– Bleeding• Medical

– Due to prior antiplatelet therapy, coagulopathies, thrombocytopenia, platelet dysfunction, hypothermia

– Options include fresh frozen plasma, cryoprecipitate, platelets, protamine(to reverse heparin effect), DDAVP (to stimulate platelet function) and tranexamic acid

• Surgical– Most likely cause if sudden onset, rapid rate, and normal clotting function– Due to vascular injury or surgical leaks– Needs hemostasis by going back to the OR

In The ICU

• Hemodynamic support– BP=CO x SVR• CO= HR x Stroke Volume

– Stroke volume is determined by three factors» Pre load» After load» Contractility

– Therefore, if the patient is hypotensive, it is either due to two problems• Pump problem (Cardiac Output)• Circuit problem (Vascular Tone)

In The ICU

• Hemodynamic support– Cardiac output should be assessed first

• If cardiac index >2.2, then cardiac output is adequate• If C.I is low, assess fluid status and cardiac rhythm

– If CVP is low, a fluid bolus may be warranted– If the CVP increases by 4mmHg with fluid bolus, then the patient is likely

well filled and cardiac output will not respond to further fluid therapy– Rule out any bradyarrhythmias or tachyarrhythmias

» Patient may require pacing» Chemical or electrical cardioversion may be required for

tachyarrythmias

• If MAP is high, this may lead to decreased cardiac output due to increased afterload– May require antihypertensive therapy

In The ICU

• Hemodynamic Support– If cardiac output is still low despite adequate

volume, then other things need to be ruled out• ECG should be done to rule out graft failure• Tamponade

– This should be considered in any patient who is in cardiogenic shock refractory to inotropic agents

– Consider it in any patient who was initially bleeding but then stops with minimal drainage from chest tubes

• Otherwise, the cardiac dysfunction may be due to the pump run and pre op cardiomyopathy

• Agents that might be used– Vasopressors

• Norepinephrine– Alpha/Beta 2 agonist– May lead to coronary vasospasm, mesenteric ischemia,

dysrhythmias• Phenylnephrine

– Pure alpha agonist– May lead to increased afterload and decreased cardiac output

• Vasopressin– Peptide– Very powerful vasoconstrictor– May lead to coronary and mesenteric ischemia

– Inotropes• Dopamine

– Dose dependent response» Can be an inotrope or vasopressor depending on dose» Can lead to tachyrhythmias

• Dobutamine– Beta 1 agonist– Short acting– Leads to tachyarrhythmias– Causes per

• Milrinone– Phosphodiesterase inhibitor– Leads to calcium ion influx into myocardial cells – Slow onset and long half life– Renally cleared– Causes vasodilatation

• Levosimendan– Calcium sensitizer– Metabolite also active and has long half life– Causes peripheral vasodilatation

• Epinephrine– Both alpha and beta agonist– Lactic acidosis– Hyperglycemia– Tachyarrhythmias

– Anti-Hypertensive therapy• Nitroglycerin

– Predominantly a venodilator– Especially useful if coronary ischemia or vasospasm is evident

• Nitroprusside– Potent vasodilator (Arterial and venous)– Leads to smooth muscle relaxation– Renally cleared– Can lead to cyanide toxicity– May also lead to hypoxia

• Labetolol– Both an alpha and beta blocker– Used especially in patients where damage due to shear stress is a concern

» Aortic dissection, aortic root surgery– Can lead to bronchospasm

In The ICU

• Intra Aortic Balloon Pump– This is a long cylindrical balloon inserted into the

aorta via the femoral artery– It should be positioned so that the tip is just under

the root of the left subclavian artery• If too high, it will lead to upper limb ischemia• If too low, it will lead to renal and mesenteric ischemia

In The ICU

• IABP– It works by counter pulsation• It inflates during diastole to improve coronary perfusion

pressure• It deflates during systole to reduce afterload on the left

ventricle and improve cardiac output

– Contraindicated in aortic regurgitation aortic dissection, and severe peripheral vascular disease

In The ICU• Important considerations

– Arrhythmias• Atrial fibrillation is a common complication of cardiac surgery, and is usually seen 36 hours post op• Ventricular fibrillation/ventricular tachycardia is uncommon and pathological. They warrant further investigation

– RV failure• Seen especially in patients with significant pulmonary hypertension• Also seen in long pump runs• These leads to a pre load dependent condition• Therapy is targeted to maintain an adequate CVP to optimize cardiac output• Agents are started to try and reduce pulmonary artery pressures

– Milrinone– Levosimendan– Inhaled nitric oxide

– Aortic root surgery• A Benthall graft is replacement of the aortic root, ascending aorta, and aortic valve• The coronary arteries therefore need to be reimplanted onto the graft

– This can lead to complications– The native root may actually be left intact so that reimplantation is avoided

– Tamponade• This may develop gradually

– Findings may include high CVP, equalization of pressures, low voltages on ECG, increasing inotropic support, and end organ dysfunction

– Ultimately, an echocardiogram will be required, be it transthoracic or transesophageal