Lippincott's Anesthesia Review: 1001 Questions and Answers by Sikka Paul

Author:Sikka, Paul
Language: eng
Format: epub
Publisher: LWW
Published: 2014-07-27T16:00:00+00:00

Figure 11-2. Reused with permission from Shanewise JS, Shin JJ, Vezina DP, et al. Comprehensive and abbreviated intraoperative TEE examination. In: Savage RM, Aronson S, Shernan SK, eds. Comprehensive Textbook of Perioperative Transesophageal Echocardiography. 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2011: 86.

29. D. Pure high-dose opioid anesthesia (e.g., fentanyl 50–100 μg/kg or sufentanil 15–25 μg/kg) has fallen out of vogue in cardiac anesthesia practice. It was useful at a time in anesthesia when the only inhaled agents available produced unacceptable myocardial depression. The main disadvantages of high-dose opioid technique include prolonged postoperative respiratory depression (early extubation is becoming a very common trend in coronary artery bypass grafting surgeries), high incidence of patient awareness/recall, exaggerated hypertensive response to stimulation like sternotomy in a patient with good left-ventricular function, bradycardia, chest-wall rigidity, postoperative ileus, and impaired immunity.

30. A. A progressive decline in cardiac output is sometimes seen after the chest is opened. This is attributed to the loss of negative intrathoracic pressure and decreased preload. Hence a IV fluid bolus may help. Factors potentiating such a response include deep anesthesia and preoperative angiotensin-receptor-blockade use. Another common response seen during sternal retraction and pericardiectomy is bradycardia and hypotension due to exaggerated vagal response. This is potentiated by hypoxia, β-blockers, and calcium channel blockers.

31. C. Aprotinin, an inhibitor of serine proteases, such as plasmin, kallikrein, and trypsin, also helps to preserve platelet aggregation and adhesiveness. It has been shown to decrease blood loss and transfusion requirements and should be considered in redo surgeries, Jehovah’s witnesses, recent administration of glycoprotein IIb/IIIa inhibitors (abciximab [ReoPro], eptifibatide [Integrilin], or tirofiban [Aggrastat], patients with coagulopathies, and patients with long pump runs. However, repeat exposure to aprotinin has been shown to cause allergic reactions, which may include anaphylaxis. Patients on a combination of aspirin and ADP-receptor antagonist are at high risk of bleeding and may benefit from aprotinin.

32. A. The events occurring in sequence after heparinization are aortic cannulation followed by venous cannulation. Venous cannulation usually causes hemodynamic changes, and we have an access to provide rapid infusion through the aortic cannula if necessary. Venous cannulation also frequently precipitates arrhythmias. Premature atrial contractions and transient bursts of a supraventricular tachycardia are common. Sustained arrhythmias must be treated pharmacologically, electrically, or by immediate anticoagulation and initiation of bypass depending on the amount of hemodynamic compromise. Sometimes, stopping the surgical stimulus is all that is needed. Superior vena cava syndrome can be caused by a malpositioned venous cannulas can be interfering with venous drainage from the head and neck.

33. B. After initiation of CPB, pump flow is gradually increased to 2 to 2.5 L/min/m2 and MAPs are monitored. It is common to see an initial fall in BP. Initial mean systemic arterial (radial) pressures of 30 to 40 mm Hg are not unusual. Abrupt hemodilution, which reduces blood viscosity and effectively lowers systemic vascular resistance (SVR), may be responsible for this drop. The effect is partially compensated by subsequent hypothermia, which tends to raise blood viscosity again.

A disastrous scenario

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