During cardiopulmonary bypass, where/how is heparin administered if blood cannot be aspirated from a vein?
During cardiopulmonary bypass, if drug administration (heparin, anesthetics, vasopresso, and vasodilator) is needed, it is done via the pump.
What are three beneficial effects of moderate hypothermia on the patient on cardiopulmonary bypass?
(1) Hepatic blood flow and enzymatic activity are decreased, reducing clearance of drugs eliminated by this route; (2) myocardial preservation is enhanced; and (3) the central nervous system (brain) is protected.
Name a short-acting agent that can prevent increased heart rate associated wilh noxious stimulation in the patient undergoing CABG surgery.
What coagulation test is used to assess heparin
efficacy in the patient undergoing coronary artery bypass graft (CABG) surgery?
The activated coagulation time (ACT)
What is the normal value for the activated coagulation time (ACT)? Adequate heparinization for cardiopulmonary bypass is indicated by an ACT that exceeds what value?
The normal ACT is 70-110 seconds. A safe ACT value for undergoing coronary artery bypass grafting is greater lhan 400 seconds
A cardiac surgery patient is heparinized, but the ACT does not increase above 400 seconds. Give two possible reasons why this might happen?
(1) The decreased effectiveness of heparin could be due to the presence of nitroglycerin. Nitroglycerin, a drug commonly administered to cardiovascular patients, reduces the effectiveness of heparin. (2) There also could be an antithrombin III deficiency
A patient about to undergo coronary artery bypass graft surgery is unresponsive to heparin (the ACT does not increase). What is the most likely reason the patient is unresponsive to heparin? What action should be taken to correct this unresponsiveness to heparin?
Most patients who are resistant to heparin have an antithrombin III deficiency. Infusion of two units of fresh frozen plasma generally results in adequate anticoagulation. Antithrombin III is present in fresh frozen plasma.
A patient who is heparinized and undergoing coronary artery bypass graft surgery requires fluid. What blood product can be given without reversing the effects of heparin? Explain.
Fresh frozen plasma. Antithrombin III must be present for heparin to exert its anticoagulant effects. FFP contains clotting factors as well as anticoagulant factors including antithrombin III. Administration of FFP has been shown to potentiate the effects of systemic heparinization
How is the heart arrested during cardiopulmonary
By infusing cold (4 degrees C) cardioplegia solution containing potassium into the aortic root. K+ produces myocardial depolarization resulting in cessation of electrical and mechanical activity. The heart is arrested by the high K+. The cold solution produces hypothermia and reduces metabolism of the cardiac muscle
To what temperature can you cool a patient before ventricular fibrillation occurs?
Ventricular fibrillation begins between 25 and 30 degrees C.
Blood draining from what cardiac vessels explains why the left ventricle will fill (unless vented) during cardiopulmonary bypass for aortocoronary bypass graft surgery?
Blood drains into the left ventricle from the Thebesian and bronchial veins. A small fraction of the coronary flow empties into the left ventricle via the Thebesian vessels.
Give two reasons why a central venous line is placed in the patient undergoing coronary artery bypass graft (CABG) surgery.
The central venous line allows: (1) access to the central circulation for infusion of cardioactive drugs, and (2) measurement of central venous pressure
The patient has a pulmonary capillary wedge pressure of 18 mmHg, systolic blood pressure
of 85 mmHg, and a cardiac index of 1.5. What is the most appropriate course of action for this patient?
The pulmonary capillary wedge pressure (PCWP) is elevated (normal:5-15 mmHg), the systolic blood pressure (SBP) is low (normal: 100-150 mmHg), and the cardiac index (CI) is low (normal: 2.8-4.2 L/min/m2). In spite of low systolic blood pressure, the patient has an adequate blood
volume, indicated by the PCWP. Therefore, an inotrope such as dobutamine, amrinone or norepinephrine is indicated to "push the volume forward."
During cardiopulmonary bypass, explain how the venous return is collected, and state the normal central venous pressure (CVP)?
Venous blood drains from the patient (usually from the right atrium) to a reservoir placed below the venous catheter. Venous blood flows to this reservoir by gravity. Central venous pressure is normally approximately 0 mm Hg (sometimes slightly higher and sometimes slightly lower) during cardiopulmonary bypass
Central venous pressure (CVP) increases substantially (to, for example 25 mm Hg) during cardiopulmonary bypass. Why?
An increased central venous pressure during cardiopulmonary bypass occurs if there is an obstruction to venous drainage. Causes of obstruction to venous return include: improper positioning of the venous cannula in the patient; a kink in the venous return tubing; entrained air in the venous return tubing creating an "air lock"; and unintended partial clamping of the venous return tubing.
Why should N2O be avoided in a patient undergoing cardiopulmonary bypass?
Clinically, N2O may be used before cardiopulmonary bypass if high dose narcotics are not used and hypotension does not occur. After cardiopulmonary bypass is initiated, N20 should be avoided because of the possibility of expanding air bubbles in the coronary and cerebral circulation
Your patient is on cardiopulmonary bypass. During rewarming phase, the MAP increases to 90 mm Hg. The bypass flow is 50 mL/kg/min. How should the elevated blood pressure be treated?
The blood pressure can be lowered by administering a vasodilator or administering an inhalational agent. Because the increased SVR (which increases the blood pressure) is usually due to inadequate anesthesia during rewarming, a volatile anesthetic is preferable to a vasodilator in patients with good ventricular function. In cases of poor ventricular function, inhalational agents are avoided because of the
potential myocardial depression after cardiopulmonary bypass. The pump flow is not excessive (at normothermia pump flow should be 50-70 mL/kg/min), so you would not try to lower blood pressure by turning down the pump flow
What percent of coronary bypass patients return to surgery? When do they usually return to surgery?
Postoperative re-exploration is necessary in 4% - 10% of cases usually in the first 24 hours
For what four reasons do most postoperative coronary bypass patients return to surgery?
(1) Persistent bleeding, (2) excessive blood loss, (3) cardiac tamponade, and (4) unexplained low cardiac output
The possibility of what problem must always be included in the differential diagnosis of unexplained low cardiac output after coronary
artery bypass graft surgery?
What is the major concern for the non cardiac surgery patient with congestive heart failure (CHF)?
Patients with congestive heart failure (CHF) are at increased risk of postoperative death
What three vessels can be compressed by the mediastinoscope? What are the consequences of compression of each of these vessels?
The innominate artery may be compressed, which will cause a cessation of flow through the vessels arising from it, the right carotid artery & the right subclavian artery. The mediastinoscope may also compress directly the right carotid or right subclavian arteries. Compression of the right innominate or carotid vessels could decrease cerebral perfusion if the patient has cerebral vascular disease. Collateral flow through the circle of Willis would be expected to maintain cerebral flow in healthy patients. Compression of the right subclavian artery will result in a loss of pulse and pressure in the right arm.
How do you monitor for occlusion of the innominate or subclavian arteries during mediastinoscopy?
It is recommended that the right radial artery be continuously monitored by: (a) palpation, (b) finger plethysmography (a device that measures changes in volume with pressure pulsations). (c) a pulse oximeter. or (d) a right radial artery line.
Where do you put the blood pressure cuff and pulse oximeter if the patient is undergoing mediastinoscopy and you do not place an arterial line? If you place an arterial line?
Here are the present recommendations. Place the blood pressure cuff on the left (to monitor for hemorrhage) and the pulse oximeter on the right finger (to monitor for innominate or right subclavian compression) if an arterial line is not placed. Place the blood pressure cuff and the pulse
oximeter on the left if an arterial line is placed in the right radial artery.
Should you put the blood pressure cuff on the left or the right when the patient is undergoing mediastinoscopy? Why?
The blood pressure cuff should be placed on the left. A drop in blood pressure in the left suggests hemorrhage, the most frequent severe complication of mediastinoscopy
What is the anesthetist's primary responsibility during mediastinoscopy?
The anesthetist's primary responsibility during mediastinoscopy is to detect the occurrence of complications of mediastinoscopy
Prior to mediastinoscopy, one would want to assure the availability of what?
Have blood available. Significant hemorrhage (occasionally massive hemorrhage) has been the most frequent major problem encountered during mediastinoscopy.
Identify the most likely reason for loss of a pulse in the right radial artery during a mediastinoscopy.
Compression of the right subclavian artery or brachiocephalic artery (innominate artery) can cause a loss of pulse and blood pressure in right arm.
List eleven complications of mediastinoscopy.
(1) Hemorrhage. (2) pneumothorax, (3) recurrent laryngeal nerve injury. (4) airway obstruction, (5) compression of the innominate artery. (6) chylothorax. (7) air embolism. (8) tension pneumomediastinum, (9) hemithorax. (10) phrenic nerve injury. and (11) esophageal injury
List the three most frequently encountered complications of mediastinoscopy, on order of greatest to least incidence.
The most common complication of mediastinoscopy is hemorrhage because of the proximity of the vessels and the vascularity of certain tumors. The second most common complication of mediastinoscopy is pneumothorax, usually right-sided. The third most common complication is recurrent laryngeal nerve injury, and is permanent in up to 50% of cases.
What is the most frequent major complication of mediastinoscopy? What is the second most frequent major complication of mediastinoscopy?
Significant hemorrhage is the most frequent major complication encountered during mediastinoscopy. Pneumothorax is the second most frequent major complication of mediastinoscopy. Injury to the recurrent laryngeal nerve is the third most frequent complication
List the one absolute contraindication for performing anesthesia for mediastinoscopy.
What are four relative contraindications of mediastinoscopy?
(1) Superior vena caval obstruction, (2) tracheal deviation, (3) thoracic aortic aneurysm, and (4) cerebrovascular disease
A patient with a mediastinal mass is induced and intubated, and blood pressure falls dramatically to 55/40 mm Hg. What should you do?
The mass may compress the pulmonary artery and heart as well as the inferior vena cava. If symptoms worsen during induction of general anesthesia in the supine position, the sitting, leaning forward, or even prone position is advised. With hypotension in the patient with a mediastinal mass, changing position may correct the problem
After a mediastinal resection, the patient presents with shortness of breath, unilateral breath sounds, tracheal deviation, and an increase in peak inspiratory pressure. What complication has occurred? What do you prepare to do?
The signs and symptoms suggest pneumothorax, the second most common complication of mediastinoscopy.The hallmark signs of tension pneumothorax are hypotension,
hypoxemia, tachycardia, increased CVP, and increased PIP. Other findings include absence of breath sounds on the affected side, asymmetric chest wall movement, tracheal shift, displacement of the cardiac impulse, hyperresonance to percussion, and extreme anxiety. Tension pneumothorax is potentially lethal; therefore, immediate treatment is essential. Chest decompression should be accomplished by placing a large-bore needle through the chest wall in the second intercostal space midclavicular line. The needle should be left in place until a tube thoracotomy is performed
What is superior vena cava syndrome?
Superior vena cava syndrome is a constellation of signs that develops in patients with a mediastinal tumor that obstructs venous drainage in the upper thorax. Cancer accounts for nearly all cases of superior vena cava syndrome
Identify the signs of superior vena cava syndrome.
Superior vena cava syndrome is due to increased venous pressure, leading to (1) dilation of collateral veins in the thorax and neck, (2) edema and cyanosis of the face, neck, and upper chest, (3) edema of the conjunctiva, and (4) evidence of increased ICP including headache and altered mental status
What are four absolute indications for one lung ventilation
Absolute indications for one-lung ventilation include: (1) presence of blood or infectious secretions in one lung (contamination of both lungs is life-threatening); (2) presence of bronchopIeural fistula or bronchocutaneous
fistula; (3) presence of giant cysts or unilateral bullae (which may rupture during positive pressure ventilation); (4) performing bronchopulmonary lavage is an absolute indication for one-lung anesthesia (it is mandatory to avoid accidental spillage of fluid from the lavaged lung to the
nondependent ventilated lung).
List three names of one-lung endotracheal tubes?
Robert Shaw, Carlens, White