Guidelines for the Care of Postoperative Cardiac Surgery Patients
1. Know the anatomy. The anatomy of the patient will predict their physiology and treatment course. Often the physiology is very different than the typical two pump, in series circulation of patients without congenital heart disease. Postoperative treatment without an understanding of the specific anatomy can lead to lethal mistakes.
2. Postoperative problems arise as a consequence of cardiopulmonary bypass and as a consequence of unique features of each type of congenital heart disease. Most often problems are a consequence of bypass, but always look for causes related to the anatomy first.
3. Data sources include the cardiology clinic records, echo reports, operative reports, cath reports AND conversations with cardiology, ICU, anesthesia and CV surgery attendings. Make them explain it to you!
POSTOPERTIVE CARDIAC RULES TO LIVE BY
1. Know the anatomy (preoperative and postoperative)
2. Active anticipatory management – by and large, postoperative cardiac patients have predictable phases to their recovery and require active interventions to stay on course.
3. If you are having trouble with rule 2, you are probably violating rule 1. Verify the anatomy (eg. Re-echo the patient, propose catheterization)
What to know about the patient’s anatomy and history
1. The lesion, its components, and specific variations (eg. Complete AV canal with malalignment and hypoplastic RV is very different than complete AV canal with normal sized ventricles).
2. Previous operations and how they impact the anatomy and physiology.
3. Pertinent echocardiographic data (Level and size of shunts, obstructions, estimates of chamber and vessel pressures and gradients, ventricular function, coronary anatomy).
4. Catheterization data (level and size of shunts, estimates of SVR and PVR, ventricular function).
5. Unique post operative problems and risks that can occur.
6. Ask the parents/guardians about other medical problems.
7. Read about the anatomy before the patient arrives in the ICU. The surgeries of the week are posted in the ICU. Cardiac cath conference occurs every Thursday at 4 pm.
What to know about the patient’s operation
1. Indications of operation and timing (why did they do it)
2. Surgical procedure (what did they do)
3. Surgical conditions (how did they do it)
o Bypass – time on the heart-lung machine
o Cross Clamp – how long is the heart arrested and without blood supply
o Deep hypothermic circulatory arrest – rarely performed. Essentially cooling the patient and stopping all support
4. Complications/other important intra-operative events
o Any problems before starting bypass (eg. Tet spells)
o Need to revise the repair
o Vasoactive agents
o Arrythmias and need for cardioversion when coming off bypass
o Any other problems during the repair or coming off bypass
5. Intra-operative asssessment
o Intra-operative transesophageal echocardiogram - identifies the nature of the repair, detects residual defects, leaks and gradients if present, and assesses ventricular function.
o CV surgerons will often measure pressure gradients and saturations in the OR before and after repairs (usually recorded in the cardiopulmonary bypass record).
6. What is the post operative anatomy
o Was the procedure palliative or corrective?
o Residual cardiac disease (eg. VSDs, residual valve stenosis)?
What to do when the patient arrives in the ICU
1. Don’t panic
2. Follow 1 – 6 in “What to know about the patient’s operation.”
3. Verify current medication dosages, ventilator settings, IV fluid rates, identify tubes and lines.
4. Physical exam focusing on cardiovascular and respiratory systems. Take note of murmurs, perfusion, liver size – remember your physical exam will change, it is important to have an accurate baseline exam.
5. Laboratory Evaluation
o Chest xray – confirm ETT, tubes and line placement, and assess cardiac size and lung fields
o EKG –determine if the patients is in a regular sinus rhythm and assess for new abnormalities (e.g. RBBB which is common following TOF repair)
o Arterial blood gas analysis with electrolytes
o Electrolytes including ionized calcium and magnesium
6. Interpret the data from the bedside monitoring and initial laboratory testing
7. Formulate a plan for the first postoperative night
1. Bleeding – cardiopulmonary bypass alters the coagulation system through factor hemodilution and platelet dysfunction. Bleeding will be manifested through mediastinal tube output. It is important to characterize and quantify the drainage on an hourly basis.
o “Acceptable” output is 2-4 cc/kg/hr of bloody drainage
o “Unacceptable” output is >10 cc/kg in 1 hour or >5 cc/kg/hr in 3 consecutive hours
*If the mediastinal tube abruptly stops draining, it must be evaluated immediately for a clot in the tube. Cardiac tamponade can occur if the tube becomes obstructed.
2. Electrolyte management – postoperative cardiac patients experience derangements in normal fluid balance, electrolyte balance and calcium and magnesium homeostasis. Electrolyte abnormalities can precipitate atrial and ventricular dysrhythmias in the postoperative cardiac patient.
o Calcium – is a potent inotrope. Follow ionized calcium levels (total body calcium will be low due to hemodilution). Maintain ionized calcium 4.6 –5.2 (serum) or 1.0 – 1.2 (blood gas)
o Potassium – hypokalemia (<3.5 mmol/L) and hyperkalemia (>5.5 mmol/L) must be treated
o Magnesium is a co-transporter of calcium- maintain serum magnesium ≥2.0 mg/dL
3. Temperature contol – fever occurs commonly in the postoperative cardiac surgery patient due to cardiopulmonary bypass activation of the inflammatory cascade. Fever will increase the metabolic demands on the myocardium and therefore should be aggressively treated.
4. Fluid balance – postoperative cardiac patients typically have significant total body water and salt overload from dilution of blood with crystalloid in the bypass circuit. Cardiopulmonary bypass also causes endothelial cell dysfunction and capillary leak, which causes fluid to be redistributed into the soft tissues, lungs, kidneys, myocardium, etc. Even though patients are typically fluid overloaded, their intravascular volume can become depleted from capillary leak as well as from ongoing chest tube drainage.
o Intravascular volume depletion frequently presents as tachycardia, hypotension and a reduced filling pressure (CVP or RA pressure). Patients whose pulmonary blood flow is dependent on systemic blood pressure (eg. Blalock Taussig shunts, Glenn procedures) may also manifest oxygen desaturation. Treat with 5 – 10 cc/kg of crystalloid or blood products if indicated.
o Fluid overload – treatment with diuretics is usually initiated 8 –24 hours after surgery. Patients with a stable blood pressure, including those receiving vasoactive drugs are candidates for diuretic therapy. The usual first line agent is furosemide (Lasix) 1 mg/kg IV every 8-12 hours or a constant infusion may be used at 2 – 8 mg/kg/day. Remember that diuretics can cause electrolyte derangements.
5. Acid – base balance – if an acidosis (pH <7.34) or alkalosis (pH >7.45) exists, the cause – metabolic, respiratory or mixed should be determined and a decision made about the necessity of intervention.
o Metabolic acidosis – if this occurs, low cardiac output should be suspected and an evaluation of the cause be performed. Buffer therapy with sodium bicarbonate may be initiated when appropriate (pH < 7.34 or base excess ≥ - 3), but the underlying cause must be evaluated.
6. Analgesia and sedation – must be addressed. Patient comfort is frequently forgotten. Untreated pain can cause tachycardia and increased metabolic demands. Neuromuscular blockade (paralysis) may be used under certain circumstances (eg. Pulmonary hypertension)
o Opioids – morphine or fentanyl (may be used as a continuous infusion in intubated patients or in a PCA in older, extubated patients). Hypotension is a side effect of both,
o Benzodiazepines – versed or ativan may be used with caution as hypotension may occur especially in patients who are hypovolemic or in those that are receiving continuous narcotic infusions
Organize your Daily Plan – Follow this Checklist!
ICU PEARLS FOR THE CARDIAC PATIENT
1. CARDIAC PATIENTS REQUIRE VIGILANCE. THESE PATIENTS SHOULD BE ASSESSED AND RE-ASSESSED BY A PHYSICIAN MANY TIMES DURING THE DAY AND NIGHT!
2. Why is the patient still intubated and what is the goal of mechanical ventilation (eg. Hyperventilation to control PVR, need to decrease LV afterload)?
3. Check the rhythm. Loss of atrio-ventricular synchrony can produce dramatic decreases in cardiac output. Frequently, you need to compare the current EKG to a baseline EKG.
4. Intracardiac lines and CVP measurements. Use them. The pressures and the wave forms provide vital information
5. You can perform a “mini-catheterization” by checking oxygen saturations drawn from the different intracardiac lines.
6. If a patient has low cardiac output, focus on the unique features of the anatomy and operation first, then look for consequences of cardiopulmonary bypass (see RULE 3)
7. Patients with LV dysfunction like mechanical ventilation and patients with RV dysfunction hate it.
IF you understand all of this while caring for your 1st postoperative patient, apply immediately for a critical care fellowship. Ask questions! The only dumb one is the one that is not asked.
References and Suggested Texts
1. Pediatric Cardiac Intensive Care. Chang AC, Hanley FL, Wernovsky G, Wessel DL, Eds. Lippencott Williams & Wilkins 1998
2. Critical Heart Disease in Infants and Children. Nichols DG, Cameron DE, Greeley WJ, et al. Mosby-Yearbook 1995
3. Essentails of Pediatric Intensive Care. Levin DL, Morriss DL. Churchill Livingstone Inc 1997
Commonly Used Vasoactive Agents