Introduction Invasive Hemodynamic Monitoring Audis Bethea, Pharm.D. Assistant Professor Therapeutics IV January 21, 2004 Hemodynamic monitoring is necessary to assess and manage shock Information obtained through hemodynamic monitoring: Cardiovascular perfomance (right and left ventricular function) Changes in hemodynamic status and organ perfusion Pharmacologic and nonpharmacologic therapy Prognosis Hemodynamic monitoring supplements clinical judgment Cardiovascular System Determinants of Cardiovascular Function Vascular network of > 60,000 miles Circulating 8 L of blood every day Provides O 2 to over 100 trillion cells Right side unoxygenated blood to the lungs Left side oxygenated blood systemically Vasculature Arteries carry blood away from the heart Veins carry blood to the heart Capillaries responsible for exchange of nutrients and gases Cardiac output (CO) = Heart rate (HR) x Stroke volume (SV) Volume of blood ejected from the left ventricle per unit time (L/min) HR is regulated by the sympathetic nervous system SV is the volume of blood ejected by the ventricles during systole Three factors influencing stroke volume Preload (LVEDV or LVEDP) stretching of the LV muscle fibers after diastole Afterload (SVR) force left ventricle has to overcome to eject blood Contractility (Inotropy) force and velocity of muscular contraction Cardiac index (CI) cardiac output adjusted for body surface area Determinants of Cardiovascular Function Hemodynamic Monitoring Preload Determines the strength of ventricular contraction Stroke volume Dependent upon EDV, pleural pressure, vascular compliance, and vascular resistance Contractility Non-invasive Vital signs HR, BP, and RR Arterial oxygen saturation Transthoracic echocardiography Invasive Eliminates potential for error due to measurement technique Assessment is not inhibited in low-flow states Recommended for all ICU patients with cardiovascular instability In 50% of shock patients non-invasive methods underestimate BP by > 30 mmhg
Invasive Hemodynamic Monitoring Pulmonary Artery Catheter Arterial catheter Inserted into radial or brachial artery Used for hemodynamic monitoring MAP driving pressure for peripheral blood flow MAP = [SBP + 2(DBP)] / 3 Central venous catheter Administration of IVF and medications Central Venous Pressure Hemodynamic data Volume status Ventricular function Oxygen delivery / consumption Fluid / medication administration CVP = RAP or RVEDP Assesses fluid status or volume s PA Catheter Hemodynamic Parameters PA Catheter Hemodynamic Parameters Cardiac output (CO) 4-7 L/min, Cardiac index (CI) 2.4-4 L/min/m 2 Assessment of cardiac function Thermodilution in temperature of blood after injection of cold H 2 O Cardiac malformations / abnormalities may effect measurements Systemic vascular resistance (SVR) 800 1400 dyne/sec/min -5 Vascular resistance across the entire systemic circulation Mean arterial pressure (MAP) 80 100 mmhg Driving pressure for peripheral blood flow Central venous pressure (CVP) 1-6 mmhg Used to qualitatively assess fluid status or blood volume changes Pulmonary capillary wedge pressure (6 12 mmhg) Closest approximation of preload Objective method of evaluating left ventricular function Elevated PCWP is often indicative of pulmonary edema Pulmonary artery pressure (20 30 mmhg) Pressure produced by the right ventricle ejecting blood into the pulmonary artery Elevated in patients with acute or chronic parenchymal pulmonary disease, PE, hypoxemia, acidosis, and patients receiving vasoactive drugs pulmonary artery pressure occurs with diminished vascular volume Systemic O2 Transport via PA Catheter Systemic O2 Transport via PA Catheter O 2 delivery (Do 2 ) 520 570 ml/min m 2 Product of CI and Cao 2 Cao 2 = Hemoglobin (Hgb) X arterial O 2 (Sao 2 ) Do 2 = CI x 13.4 x Hgb x Sao 2 Mixed venous O 2 sat. (Svo 2 ) 70 75% Indicator of tissue perfusion Indicator of the body s O 2 consumption (Vo 2 ) Oxygen consumption (Vo 2 ) 110 160 ml/min m 2 Estimates the oxygen demand of the body Vo 2 = CI x 13.4 x Hb x (Sao 2 Svo 2 ) Vo 2 is independent of supply except at low rates of Do 2 and in critically ill patients Critically ill have an Vo 2 resulting in O 2 deprivation at normal rates of delivery Oxygen extraction ratio (O 2ER ) 20 30% Calculation assesses the uptake of oxygen through the microcirculation (capillaries) O 2ER = (Vo 2 / Do 2 ) x 100
Complications of PA Catheters Patient Case Infection Pulmonary infarction Pulmonary thrombosis Arrhythmias Intracardiac damage Pneumothorax Arterial-venous fistulas Pulmonary artery perforation 62 yo male admitted to the ICU following surgical repair of an abdominal aortic aneurysm. The patient is intubated and receiving 60% O 2. He weights 78 kg and has a BSA of 1.8 m 2. He has a history of HTN, (BP 140/100) for which he takes nadolol and HCTZ. His ABGs are adequate and he is receiving 150 ml/hr of LR solution intravenously. His 2-hour post-op and initial (in parentheses) hemodynamic profiles are as follows: BP 90/50 mmhg (130/78), MAP 63 mmhg (95), pulse 88 bpm (80), CO 4 L/min (5), PCWP 6 mmhg (12), SVR 1800 dyne sec cm -5 (1392), urine output 25 ml/hr (70), temperature 37 o C (37), Hgb 8 g/dl (12). Based on the hemodynamic profile, determine the etiology of this patient s cardiovascular failure. 1. What shock state is this patient experiencing? Patient Case Hemodynamic Drugs Answers tomorrow!! These medications are administered via continuous infusion Infusion rate (ml/min) = desired dose rate (R) = R drug concentration (C) C Therapeutic effects elicit vasoconstriction and increased CO Goal of therapy Optimize MAP and/or CO increasing tissue perfusion and O 2 delivery Adrenoreceptors Vasopressors and Inotropes: Norepinephrine Activates α and β 1 receptors Widespread vasoconstriction contractility and SV Hemodynamic parameters BP, HR PCWP, dose-dependent MAP, SVR, dose-dependent CO, mostly at lower doses 2 30 mcg/min; up to 200 mcg/min > 30 mcg/min risk of AE Severe acidosis effects HTN, ischemia, tachyarrhythmias
Vasopressors and Inotropes: Epinephrine Vasopressors and Inotropes: Phenylephrine Activates α1, α2, β1, β2 receptors Low dose: vasodilation and CO High dose: vasoconstriction and CO Low dose: HR, minor BP and SVR High dose: HR, BP, PCWP, MAP, SVR CO throughout the dosing range Low dose 0.01 0.05 mcg/kg/min High dose > 0.05 mcg/kg/min Severe acidosis effects HTN, tissue ischemia, tachyarrhythmias Synthetic, non-catecholamine Selectively activates α1 receptors Systemic vasoconstriction BP, PCWP, MAP, SVR 30 300 mcg/min Moderate acidosis effects HTN, tissue ischemia, reflex bradycardia Vasopressors and Inotropes: Dopamine Vasopressors and Inotropes: Dopamine Dose-dependent α1, α2, β1, β2, DA activity Low dose: vasodilation Mid-dose: vasodilation, HR, contractility High dose: vasoconstriction, HR, contractility Mid-dose: HR, CO, mild MAP, SVR High dose: BP, HR, CO, PCWP, MAP, SVR Low dose 0.5 3 mcg/kg/min Mid-dose 3 10 mcg/kg/min High dose 10 20 mcg/kg/min Moderate to severe acidosis effects HTN, ischemia, tachyarrhythmias Potential tachyphylaxis Vasopressors and Inotropes: Vasopressin Vasopressors and Inotropes: Vasopressin Antidiuretic hormone (ADH) HR, PCWP, CO BP, MAP, SVR Vasodilation due to acidosis Vasopressin reverses effects of acidosis Physiologic activity Serum osmolality Vascular volume Hormones Alterations in serum Paco2 and Pao2 0.01 0.5 mcg/min > 0.04 mcg/min risk of AE Acidosis does not affect activity Stimulates vascular V1 receptors Stimulation of renal V2 receptors HTN, tissue ischemia, hypervolemia
Vasopressors and Inotropes: Dobutamine Vasopressors and Inotropes: Milrinone Synthetic catecholamine β1, β2 w/ extremely weak α activity in SV, HR β2 activity overcomes the minimal α activity resulting in vasodilation BP and SVR HR and CO 2 20 mcg/kg/min Severe acidosis may effects HTN, hypokalemia, tachyarrythmias Tachyphylaxis Phosphodiesterase inhibitor intracellular camp intracellular Ca ++ intracellular Ca ++, contractility camp promotes relaxation of smooth muscle tissue BP, PCWP, SVR HR, CO (mcg/kg/min) LD: 50 mcg/kg MD: 0.375 0.5 mcg/kg/min Adjust for renal dysfunction CrCl 30 50 ml/min 0.33 0.43 CrCl 5 20 ml/min 0.2 0.28 CrCl < 5 ml/min not recommended BP, tachyarrhythmia, rare thrombocytopenia Preparation and Administration All admixtures are placed in 250 ml Vasopressin and milrinone are exceptions Dextrose 5% is preferred diluent Premix bags: Dopamine, dobutamine, and milrinone Central line infusion is preferred