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Postoperative Complications of Cardiac Surgery

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by

Pardeep Singh

on 22 October 2012

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Transcript of Postoperative Complications of Cardiac Surgery

Mechanisms:
Renal artery vasoconstriction
Loss of pulsatile flow during bypass
Atheroembolic disease

Prevention:
Optimize renal perfusion and avoid nephrotoxic meds such as Aminoglycosides, ACE inhibitors, and radiocontrast agents.
Low-dose dopamine and loop diuretics are attempted for optimizing renal perfusion but have not shown proven efficacy. In an off-pump surgery, it may be used to decide on timing of conversion to on-pump.
A decrease in cerebral saturation to less than 50% saturation correlates with postoperative neurocognitive dysfunction during off-pump cardiac manipulation for graft placement. Stroke

Two most important predictors:
Aortic atheroma
Prior history of stroke

Patients who have limited or no atheroma have a less than 2% incidence while those with a grade 4 or grade 5 atheroma have a 40% stroke rate.
Patients with carotid stenosis of less than 50% have a 1% or incidence, whilst those with 90% stenosis or greater have a 6.5% stroke rate

Postperfusion syndrome, which is a constellation of neurocognitive impairments attributed to cardiopulmonary bypass (CPB), may also occur post cardiac surgery. Neurologic complications may result from:

Atheroembolism of aortic debris
Embolism of LA or LV thrombus
Cerebral hypoperfusion
Air embolism
Microembolisms of granulocyte aggregates, fibrin, and platelets. Pulmonary Hypertension

Present in some patients with structural or congenital heart disease.

Complications such as pneumonia and atelectasis may cause hypoxic vasoconstriction

Treatment is with short term inhaled nitric oxide
rebound pulmonary hypertension that occurs upon withdrawal may be treated with sildenafil Pneumonia
Atelectasis
Decreased Thoracic Compliance
Difficulty Weaning
Diaphragmatic Dysfunction – phrenic nerve injury
Acute Lung Injury and Acute Respiratory Distress Syndrome
Incidence: <2% of cardiac surgery that used bypass

Characterized by Acute Onset, Bilateral Infiltrates, Decreased ratio of arterial oxygen tension to fraction of inspired oxygen (decreased PaO2:FiO2), and a lack of evidence of elevated left atrial pressure. Early Graft Occlusion:
Occurs within 30 days after surgery and occurs in 5 -10% of saphenous vein grafts.
Generally related to technical problems at the anastomosis
Risk reduced with early aspirin therapy which should be typically started six hours after surgery.

Immunosuppression from CPB (peaks on POD 1)

Later Hematologic Complications:
Chronic Hemolysis from paravalvular leak
Diagnose by serial hemoglobin, serum LDH, haptoglobin, and serum and urine bilirubin levels.

Heparin-Induced Thrombocytopenia and Thrombosis (5%) How does one exclude cardiac dysfunction? Constrictive pericarditis
incidence of 0.2% to 2.0%
late complication that presents on average of 82 days after surgery

Pneumopericardium causing cardiac dysfunction can occur from positive pressure ventilation Continuous telemetry
Continuous invasive blood pressure monitoring
Pulse oximetry
Measuring cardiac filling pressures and cardiac output by means of a pulmonary artery catheter if needed (i.e.. Swan-Ganz). This may be removed within 12 to 24 hours of surgery if significant if pressors, dilators, inotropic agents are no longer required.
Monitor fluid shifts Immediate Post-op Monitoring in ICU Incidence of up to 5% after median sternotomy
Detected at median of 7 postoperative days
Sternal wound infections are often monomicrobial with most common cause being coagulase negative Staph.

Culture of Staph. Aureus from blood should raise suspicion of Mediastinitis. One study revealed that these patients will have purulent discharge 85% of the time.
Early wound dehiscence is due to group A Strep or C. perfringens.
Hallmark Radiographic Findings: Localized mediastinal fluid and Pneumomediastinum
Treatment involves debridement and broad spectrum antibiotics. 8. Sternal Infections Acute renal failure occurs in up to 30% of patients when defined as a 50% increase in baseline creatinine.

Severe enough to require dialysis in up to 5% of patients
Risk Factors:
Poor cardiac performance
Perioperative hemodynamic instability 6. Renal Dysfunction Detecting Cerebral Hypoperfusion:

Cerebral oximetry monitors cerebral venous oxygen saturation and may be used as an adjunct to detect cerebral hypoperfusion and thus eliminate nonembolic causes of stroke and cognitive dysfunction. Encephalopathy (Delirium)

Peaks within 24 hours after surgery and only 10% of patients have symptoms by the 10th day.

Associated with preoperative substance abuse syndromes, metabolic conditions, and dementia, but Not with age, alcoholism, narcotics, or sedatives.

Early recognition is important as prompt initiation of therapy may prevent worsening of the complication. 5. Neurologic Dysfunction Incidence of >5% with frequency increasing among elderly
Neurologic insult may result in:
Focal injuries: Stroke (5% in age >65)
Deterioration in intellectual function
Memory deficits
Seizures
Stupor or Coma 5. Neurologic Dysfunction Bleeding
Usually due to:
Incomplete surgical hemostasis
Residual heparin effect after bypass
Clotting factor depletion
Hypothermia
Postoperative Hypotension
Hemodilution (dilutional thrombocytopenia and coagulopathy
Platelet dysfunction
Postoperative bleeding is significantly less in off-pump procedures
Severe bleeding requiring >10 units RBCs: 3% to 5% of cases 3. Hematologic Dysfunction A consequence of severely decreased systemic vascular resistance (SVR)

Occurs in 5 – 8% of patients undergoing cardiac surgery

Most patients respond to low dose noradrenaline.

Pathogenesis believed to be due to a systemic inflammatory response to surgery

Some patients have been shown to have a deficiency of vasopressin or increased production of nitric oxide. 2. Vasodilatory Shock 1. Telemetry to identify dysrhythmias

2. ECG to look for myocardial ischemia/injury/infarct

3. Assess hemodynamics via pulmonary artery catheter to evaluate pressure tracings, cardiac output, and systemic and pulmonary vascular resistance

4. Echocardiography
E: Pericarditis, Pericardial Effusion, and Tamponade

Tamponade
compromise cardiac output with as little as 150 mLs of fluid
Most common early finding is tachycardia
Regional tamponade responding to surgical evacuation after primary CT surgery, is sometimes difficult to diagnose postoperatively by hemodynamics and even echo. A small study of 21 patients revealed that only absence of heparin treatment, a large positive fluid balance, and a low cardiac index predicted a favourable hemodynamic response to re-thoracotomy 1. Cardiac Dysfunction
E: Pericarditis, Pericardial Effusion, and Tamponade

Pericarditis after CABG is known as postpericardiotomy syndrome

Presents frequently as chest pain
2 days to several weeks after surgery
Continued pericardial inflammation of several months can result in constrictive pericarditis
May see Eosinophilia and Atypical Lymphocytosis 1. Cardiac Dysfunction
C. Dysrhythmias

Atrial Arrhythmias: Rate control at 80-100 beats per minute. Prophylaxis with beta-blockers or amiodarone helps prevent postop AF.
If AF is new and does not terminate within 24 hours, it’s recommended that the patient be started on anticoagulation and continued for 4 weeks minimum if AF stops prior to discharge.

Ventricular arrhythmias: Sustained VT must be promptly converted electrically or chemically. Magnesium supplementation may reduce incidence but trials have revealed no impact on length of hospital stay, frequency of perioperative MI, or mortality.
3.1% incidence of sustained VT at a mean of 4 days after surgery, with an in-hospital mortality rate of 25%.

Bradyarrythmias – common after valve surgery – control with pacing wires. 1. Cardiac Dysfunction B. Physiologic

Inadequate preload

Excessive afterload

Poor inotropy (i.e.. Cardiomyopathy) 1. Cardiac Dysfunction Most common causes are:

A. Mechanical

B. Physiologic

C. Dysrhythmias

D. Myocardial infarction

E. Pericarditis, Pericardial Effusion, and Tamponade 1. Cardiac Dysfunction 1. Cardiac Dysfunction/Complications
2. Vasodilatory (Distributive) Shock
3. Hematologic Dysfunction
4. Pulmonary Dysfunction
5. Neurologic Dysfunction
6. Renal Dysfunction
7. Gastrointestinal Dysfunction
8. Wound Dehiscence / Infections Overview of Complications: Continue frequent monitoring of vital signs and hourly fluid shifts.

Continue monitoring fluid shifts by measuring:
Chest and mediastinal tube drainage
Urine output
Patient weight Upon transition to a high-dependency unit: Vasospasm
Altered platelet-endothelial cell interactions
Generalized inflammatory response due to contact of with bypass equipment
This all results in decreased blood flow to vital or organs such as the brain, heart, kidneys, and gut. Postoperative complications that distinguish cardiac surgery from other types of surgery, particularly due to the use of cardiopulmonary bypass involve: Complications of Cardiac Surgery May use signal averaged ECG to predict postoperative AF
Patients at high risk for post-operative AF may be started on prophylactic amiodarone 7 days prior to surgery
Class I evidence for use of Flecainide, Dofetilide, and Ibutilide for pharmacologic conversion.
Class I evidence for use of Beta Blockers for post-operative management of atrial fibrillation.
Class IIa evidence for use of Amiodarone for conversion. A quick word about arrhythmias: 1. Cardiac Dysfunction/Complications
Mechanical, Physiologic, Dysrhythmias, MI
2. Vasodilatory Shock
3. Hematologic Dysfunction
4. Pulmonary Dysfunction
5. Neurologic Dysfunction
6. Renal Dysfunction
7. Gastrointestinal Dysfunction
8. Wound Dehiscence / Infections Wrap up: Usually late but serious complications (1.3%) that occur beyond 7 days postoperatively and include:

Bowel ischemia from embolization or low flow (5%)
Upper or lower GI bleeding (40%) from gastritis, peptic ulceration and diverticular disease
Diarrhea from pseudomembranous colitis
Pancreatitis (34%)
Cholecystitis (11%)
Septic rupture of spleen 7. Gastrointestinal Complications Pleural Effusion
Causes:
Heart failure
Postpericardiotomy syndrome
Pneumonia
Pulmonary Embolism
Central line erosion through central venous structures
Chylothorax
Hemothorax 4. Pulmonary Dysfunction Thrombosis
Increased risk after undergoing cardiopulmonary bypass due to increase platelet activity E. Pericarditis, Pericardial Effusion, and Tamponade:
Postpericardiotomy effusions
occur 1 to 2 weeks after surgery
incidence of 60%
aortic root surgery predisposed to a 6-fold increase in effusions. This warrants surveillance echo every 6 months for 2 years postoperatively. 1. Cardiac Dysfunction
D. Myocardial infarction

Diagnosed by New Q-waves, New LBBB, or a Troponin of greater than 5 to 10 times the upper limit of normal.

Incidence of 5% of patients undergoing CABG. 1. Cardiac Dysfunction A. Mechanical
Spasm
Occlusion of coronary artery graft
Prosthetic valve paravalvular regurgitation
Cardiac tamponade
Hematoma
Systolic anterior motion of mitral valve with left ventricular outflow tract obstruction. 1. Cardiac Dysfunction 1. To review early and late complications of cardiac surgery, including the unique problems associated with cardiopulmonary bypass.

2. To understand how to monitor for and diagnose these complications by means of common, urgent investigations and changes in vital signs.

3. To review the treatment measures for these complications. Objectives 4. Pulmonary Dysfunction (continued)
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