Positive airway pressure (PAP) should be maintained at less than 25 mm Hg postoperatively. PAP is measured by a catheter usually fed through the right ventricle to the main pulmonary artery:
‥ Normal PAP is 10–20 mg Hg (mean 15 mm Hg). PAP is usually about 25%–34% the systemic blood pressure rate. Oxygen saturation is usually about 80%.
‥ Increased PAP may indicate pulmonary obstruction or embolus, left-to-right shunt, left ventricular failure, pulmonary hypertension, mitral stenosis, pneumothorax, lung/alveolar hypoplasia, hyperviscosity of blood, or increased left atrial pressure.
‥ Decreased PAP may indicate a decrease in intravascular volume, decreased cardiac output, or obstruction of pulmonary blood flow.
The pooling of blood may produce higher outflow from the chest tube when the patient is moved. Bright crimson blood and a steady stream of discharge are signs of acute onset bleeding. In particular, if discharge slows down after first speeding up, dark red blood signifies older blood rather than recent bleeding. No more than 200 mL in 2–6 hours of chest tube drainage should be used. A transesophageal echocardiography may be necessary if there is a suspicion of cardiac tamponade in addition to coagulation testing, repeat chest x-rays to measure the width of the mediastinum, and excessive bleeding.
The criteria ( 50 mL/hr) for weaning from ventilation in the initial postoperative period are met by chest tube drainage of 40 mL/hr. Awakens without stimulation and a sufficient reversal of neuromuscular inhibition are further requirements. The ideal core temperature is greater than 35.5°C. With a cardiac index of over 2.2 L/min/m2, a systolic blood pressure of 100–140 mm Hg, a heart rate of less than 120 bpm, and no arrhythmias, hemodynamic status should be stable. The pH of the blood should be between 7.30 and 7.50, the partial pressure of carbon dioxide should be under 50 torr, the partial pressure of oxygen in the arterial blood should be over 75 torr, and the fraction of inspired oxygen (FiO2) should be at or above 0.5.
For the first 48 hours following surgery, blood glucose levels should be kept below 180 mg/dL to lower the risk of wound infection in both diabetics and non-diabetics. The most popular insulin is Novolin R, which is administered as a bolus and is then followed by a 100 U/100 mL normal saline infusion. It is not advised to lower blood sugar to fewer than 120 mg/dL. Increased insulin resistance brought on by a stress reaction, total parenteral feeding without an appropriate insulin response, and sepsis may result in hyperglycemia following surgery.
A primary risk factor for developing intraoperative or postoperative (most common) embolic strokes is manipulation of the ascending aorta. Atrial fibrillation (Afib) is another condition that frequently precedes strokes, especially if it lasts for a long time (48 hours). Heparin usage requires caution because 30% of infarcts have a chance of turning hemorrhagic. Several infarcts of various sizes could develop after cardiac surgery. The initial computed tomography (CT) scan may not be diagnostic, thus subsequent scans may be required. The most sensitive diagnostic is diffusion-weighted magnetic resonance imaging, but it may not be available and could reveal infarcts that weren't known to exist before surgery.
Systolic blood pressure that is noticeably lower during intake than expiration is known as pulsus paradoxus. A pulsus paradoxus with a difference of more than 10 mm Hg is regarded as abnormal and is frequently a symptom of cardiac tamponade. It is normal to experience a drop in blood pressure of 10 mm Hg or less during inspiration, but a larger pressure difference could be a sign of various cardiopulmonary complications, such as pericardial effusion, pericarditis, pulmonary embolism, cardiogenic shock, chronic obstructive pulmonary disease, asthma, and obstruction of the superior vena cava. If pulsus paradoxus is discovered, blood pressure data should be reassessed to guarantee accuracy.
Indications for renal replacement therapy (RRT) include metabolic acidosis, fluid overload, and hyperkalemia. Increased disorientation, pericarditis, or gastrointestinal bleeding are some further warning signs. Increased oliguria and serum creatinine necessitate further analysis and could initiate RRT to stop further kidney damage. For patients needing RRT following heart surgery, intermittent hemodialysis (given over 3–4 hours three times a week) and continuous venovenous hemofiltration are frequently employed. Slow continuous ultrafiltration, continuous venovenous hemofiltration, and continuous venovenous hemodiafiltration are all examples of continuous venovenous systems.
