DK2985_C000 1..28 - AlSharqia Echo Club

Echocardiography During Cardiac Surgery 299PEEP = 0 cm H2OPEEP = 10 cm H2OPPV INSPIRATIONExpiratory velocity: 84.5 cm/secInspiratory velocity: 71.6 cm/secDifference: 12.9 cm/secPPV INSPIRATIONExpiratory velocity: 82.6 cm/secInspiratory velocity: 63.9 cm/secDifference: 18.7 cm/secFigure 13.17 Effect of 10 cmH 2 O of positive-end expiratory pressure (PEEP) on the right ventricular outflow tract velocities obtainedfrom a deep transgastric view. Note that the absolute velocities values were reduced and the inspiratory to expiratory gradient increased(PPV, positive-pressure ventilation).2. Intravenous Anesthetic Agents on Systolic FunctionOpioidsMost evidence indicates that fentanyl produces little orno direct change in myocardial contractility and thatopioids have depression-sparing actions when combinedwith a potent inhaled agent. Maintaining preload is essentialto promote hemodynamic stability and preserveadequate cardiac function. Opioids can decrease preloadthrough direct sympatholytic and vagotonic actions. (Cardiovascularpharmacology of anesthetics. In: EstafanousFG, ed. Cardiac Anesthesia: Principles and ClinicalPractice. 2nd ed. Lippincott Williams & Wilkins, 2001.)BenzodiazepinesBenzodiazepines by themselves produce only a milddecrease in myocardial contractility. Nevertheless, ventricularfilling pressures can decrease after the induction ofanesthesia with benzodiazepines, particularly during hypovolemia.The SVR may also decrease, resulting in loweringof systemic blood pressure by up to 20%. (Cardiovascularpharmacology of anesthetics. In: Estafanous FG, ed.Cardiac Anesthesia: Principles and Clinical Practice. 2nded. Chapter 10. Lippincott Williams & Wilkins, 2001.)PropofolMore often than not, propofol has been shown to be adirect myocardial depressant in animals and humans.Using arterial systolic blood pressure and TEE short-axisleft ventricular measurements to evaluate the end-systolicpressure–volume relationship in humans, Mulier et al.(31) demonstrated that propofol has dose-dependent,negative inotropic properties. Furthermore, the negativeinotropic properties of propofol are greater than those ofequipotent doses of thiopenthal in both intensity and duration(Fig. 13.18). More recently, Schmidt et al. (32)suggested that milder sedative concentrations of propofol(0.65–2.6 mg/mL) produce significant vasodilatation butno direct negative inotropic effects. Venodilatation andreduction in preload as well as dose-related arterial vasodilatationand afterload reduction have been demonstratedto be important effects of propofol administration. Thesephenomena affect the systemic circulation to a greaterdegree than the pulmonary circulation. (Cardiovascularpharmacology of anesthetics. In: Estafanous FG, ed.Cardiac Anesthesia: Principles and Clinical Practice.2nd ed. Chapter 10. Lippincott Williams & Wilkins,2001.)BarbituratesMyocardial contractility is decreased with barbiturates,through mechanisms involving calcium transport and itsinteraction with myofibrils. Its negative inotropic actionis greater than that produced by benzodiazepines, etomidate,or ketamine, but probably not as large as the oneproduced by potent inhaled anesthetics. (Cardiovascularpharmacology of anesthetics. In: Estafanous FG, ed.Cardiac Anesthesia: Principles and Clinical Practice. 2nded. Chapter 10. Lippincott Williams & Wilkins, 2001).KetamineInduction doses of ketamine increase heart rate (HR),cardiac output (CO), pulmonary and systemic bloodpressure, as well as pulmonary and systemic vascular