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Principles of Postoperative ICU Management: Part 1 Allison K. Cabalka, MD Associate Professor of Pediatrics Consultant, Pediatric Cardiology Mayo Clinic Objectives 1. Describe basic hemodynamic monitoring and evaluation of the postop CHD patient 2. Review common vasoactive medications used in the ICU 3. Briefly discuss postoperative arrhythmias and treatment Objectives 1. Describe basic hemodynamic monitoring and evaluation of the postop CHD patient 2. Review common vasoactive medications used in the ICU 3. Briefly discuss postoperative arrhythmias and treatment Basic Assessment • Know preoperative anatomy • Were there any important preoperative co-morbidities? – Airway, GI, nutritional, neurological, etc. • Review detailed surgical notes – Was this palliative or complete repair? – Expected status? – Any important intraoperative events? Physical Exam • General appearance? – Overall color, quick assessment • Use your hands! – Cardiac ‘output’?: Are the toes warm? • Peripheral vs. central pulses, perfusion • Hepatomegaly, ascites, edema • Get out your stethescope! – Any concerning lung sounds, murmurs, gallops Hemodynamic Monitoring • Invasive lines – Arterial blood pressure – Central venous pressure • Ventilator – Peak/mean airway pressures/PEEP – Oxygen saturation – pulse oximetry • What goes in vs. what comes out? – Fluids and medications in – Urine and chest tube output Bedside Monitor: Basics PGE1-dependent neonate awaiting neonatal surgery… Bedside Monitor: Basics Heart Rate & Rhythm Bedside Monitor: Basics BP Bedside Monitor: Basics CVP Bedside Monitor: Basics Pulse Oximeter Bedside Monitor: Basics RESP Postop Hypotension? 3 Main Causes: • Low intravascular volume (hypovolemia) – Inadequate filling pressure, blood loss • Low cardiac index – Poor pump function • Maldistribution of intravascular volume – Vasodilation with poor peripheral vascular tone – Usually normal cardiac function Volume Status? CVP • Used to assess right ventricular function and systemic fluid status – Normal CVP is 2-6 mm Hg • CVP is elevated by: – Overhydration - increases venous return – Heart failure or stiff RV which limit venous inflow and leads to venous congestion – Positive pressure ventilation • CVP decreases with: – Hypovolemia, shock from hemorrhage, fluid shifts, and low intravascular volume/dehydration Assessment of Volume Status • Some postop conditions require higher filling pressures to maintain cardiac output • Postop TOF with stiff, hypertrophied right ventricle • Fontan or single ventricle patient • Consequences of sustained high CVP? – Ascites, liver congestion, effusions (chylothorax) Volume Resuscitation • Basic colloid or crystalloid solution – 5% Albumin, Normal saline/LR • Be sure that Hgb is high enough for clinical situation – Cyanotic patients typically require a higher Hgb – O2 carrying capacity depends on Hgb • Remember equation for cardiac output (systemic index) PRBC Transfusion? • Recent studies suggest adverse effects in adults undergoing heart surgery • Is it associated with prolonged duration of mechanical ventilation in neonates? – Recent publication from Boston Children’s – Neonates undergoing 2-ventricle repair – Multivariate analysis: strongest predictors of DMV were total support time, greater intraoperative blood use & early postop blood use Kipps AK, et.al., Ped Crit Care Med, 2011 Objectives 1. Describe basic hemodynamic monitoring and evaluation of the postop CHD patient 2. Review common vasoactive medications used in the ICU 3. Briefly discuss postoperative arrhythmias and treatment So You’ve Done Your Volume Resuscitation… • • • • CVP appropriate or high Hgb appropriate (but not too high) BP is still not what you’d like UOP is still not what you’d like • Time for vasoactive agents • And perhaps an echocardiogram… Basic ICU Medications • Most medications used in the fresh postop CHD pt are “vasoactive” • That is, manipulating vascular bed in some way or another – Inotropic medications – Afterload reduction – Pulmonary vasodilators Basics of Receptors • Alpha adrenergic – Alpha-1 receptors located in vessel walls, activation induces significant vasoconstriction • Beta adrenergic – Beta-1 receptors most common in the heart, stimulation increases inotropy and chronotropy with minimal vasoconstriction – Stimulation of Beta-2 adrenergic receptors in blood vessels induces vasodilation • Dopamine – Renal, splanchnic (mesenteric), coronary, and cerebral vascular beds – Stimulation of these receptors leads to vasodilation Inotropic Drugs Dobutamine • Primarily acts on beta1 receptors, with some beta2 and alpha effect • Increase in cardiac index secondary to increased stroke volume – Occurs without a significant increase in heart rate – Less arrhythmia than epinephrine or isoproterenol • SVR is either unchanged or decreased (at higher dose) • No effect on pulmonary vascular resistance Dobutamine: Indications • Depressed LV function and elevated LV filling pressures (without significant hypotension) • Desire for afterload reduction + inotropy – Dosing 2-20 mcg/kg/min titrated to effect – Higher doses required in young children compared to adults Dopamine • Sympathomimetic amine – Direct stimulation of beta1 and alpha1 receptors – Precursor of norepinephrine and epinephrine • Indications: – Low cardiac output after cardiac surgery – Septic shock – Premature infants with hypotension • Dosing range: 2-20 mcg/kg/min Dopamine: Side Effects • Extravasation – Tissue necrosis and gangrene – Central venous infusion preferable • Arrhythmia – Supraventricular tachyarrhythmias – Risk factors: • Preexisting supraventricular rhythm • High dose dopamine (10-20mcg/kg/min) – Increased PVC’s at >5mcg/kg/min Epinephrine • Low/medium dose (<0.08 mcg/kg/min): – Mixed beta1 and beta2 agonist – Inotrope and chronotropic – Decreases PVR and increases PBF • May result in V/Q mismatch • High dose: – Alpha agonist – Vasoconstrictor – Increases PVR • Likely reduces renal and mesenteric blood flow Epinephrine • Indications: – Depressed ventricular function – Low cardiac output – Systemic hypotension • Side effects: – Ventricular arrhythmia – Hypokalemia – Hyperglycemia • Central venous access is required Epinephrine and Cardiac Arrest • Drug of choice in CPR • Given as a bolus in doses that stimulate alpha-adrenergic receptors (0.01 mg/kg = 0.1 cc/kg of 1:10,000) • Repeated q 3-5 minutes during resuscitation • No longer a role for high dose Epi – No better outcomes (may be worse) Milrinone • Phosphodiesterase inhibitor – Inhibits cyclic nucleotide phosphodiesterase(III) • Increases cAMP in myocardial and vascular muscle • Increased cAMP = increased intracellular calcium concentration • Increased intracellular calcium – Improves myocardial contractility – Relaxes systemic vasculature Milrinone • Indications: – Low cardiac output S/P surgery – Dilated cardiomyopathy – Sepsis associated cardiac dysfunction • Effects: – – – – Increases cardiac index Increases heart rate Decreases PVR and SVR Improves diastolic relaxation • Dosage: 0.25-1.0 mcg/kg/min – Load ‘on pump’ 50 mcg/kg What About Vasodilation? Vasodilators: Basic Principles • Work = Δ P x V ΔP-pressure V-Volume that the heart pumps • Decreased blood pressure = decreased work • Afterload = Pressure Nitroprusside • Direct smooth muscle relaxation • Venous and arteriolar relaxation – Decreased afterload – Decreased preload • Decreases SVR and PVR Nitroprusside • • • • Ventricular dysfunction Afterload reduction after cardiac surgery Low cardiac output syndrome Hypertensive emergencies – Blood pressure control S/P coarctation • Dosing Range: 0.5-8 mcg/kg/min – May be delivered in peripheral vein What About Vasoconstriction? Norepinephrine • Endogenous catecholamine that acts at sympathetic postganglionic fibers – Potent beta1 and alpha stimulator – Minor beta2 effects • Clinical Effects: – Increased cardiac index – Increased systemic and pulmonary vascular resistance • Dosage: 0.05-0.1 mcg/kg/min (max 1-2 mcg/k/min) Norepinephrine: Indications • Vasodilatory shock (“warm”) – Hyperdynamic septic shock • Augments coronary blood flow by increasing systemic diastolic pressure – Remember the effect of increasing afterload! • Central venous access required Objectives 1. Describe basic hemodynamic monitoring and evaluation of the postop CHD patient 2. Review common vasoactive medications used in the ICU 3. Briefly discuss postoperative arrhythmias and treatment Background • Existing data reports 27 to 48%* incidence of arrhythmias in pediatric post-operative patients • Effects of cardiopulmonary bypass/surgery – Catecholamine stimulation – Suture lines/patches/scarring – Residual hemodynamic issues *Valsangiacoma E, Schmid ER, Schupbach RW et al; Ann Thorac Surg 2002 *Pfammatter JP, Bachmann DCG, Bendict PW, et al; Pediatr Crit Care Med 2001 Pediatric Postop Arrhythmia 28/189 (15%) pediatric patients experienced an arrhythmia Arrhythmia # % Junctional ectopic tachycardia (JET) 16 8.5 Complete atrioventricular block (CAVB) 7 3.7 Ventricular tachycardia (VT) 4 2.1 Reentrant supraventricular tachycardia (SVT) 1 0.5 Correlated with length of bypass time and crossclamp time Delaney J et al, J Thor Cardiovasc Surg 2006 Tachycardia Sinus Tachycardia is the most common tachycardia in children Sinus Tachycardia • Evaluation once rhythm is confirmed: – – – – Hypovolemia Anemia Epinephrine Afterload reducing agents with low intravascular volume • Remember fever and pain contribute • Evaluate response to treatment – Rate should NOT remain fixed… Premature Beats • Usually in isolation, PAC or PVC (some PJC) – Not clinically significant • Atrial irritability is common (check lines?) – Surgical manipulation also contributes Postoperative SVT • Automatic focus tachycardia – Atrial ectopic tachycardia – Junctional ectopic tachycardia • AV Node dependent re-entry tachycardia – Supraventricular tachycardia • Concealed bypass tract, WPW, AVNRT • AV Node independent re-entry tachycardia – Atrial flutter – Atrial fibrillation Junctional Ectopic Tachycardia • Common post-operative arrhythmia – Originates from AV node – Particularly in postop TOF/Fontan patient • Heart rates >150 beats per minute • Loss of AV synchrony – Look for AV dissociation • Slower P wave rate – Easy to diagnose with pacing wires postop Junctional Ectopic Tachycardia Junctional Ectopic Tachycardia • Treat with IV Amiodarone – Load 5-10 mg/kg IV – Drip infusion of total of 10-20 mg/kg/24 hrs • Alternative or complimentary – Cooling (blanket, cooled NG lavage) – Reduction of sympathetic stimulation (Epinephrine) – Correct Ca++ and Mg+ levels – Volume replacement – Muscle relaxation Supraventricular Tachycardia SVT ECG Treatment: Intravenous Adenosine Rapid IV Push Dose: 0.1 mg/kg Pre-excitation (WPW) This patient is at risk for postoperative SVT! Recurrent SVT: Rx options Adenosine may be repeated but if SVT recurs: • Procainamide IV – 15 mg/kg IV load over 30 min – 20-80 mcg/k/min IV drip • Beta-blocker therapy – Propranolol – Esmolol Propranolol • β-blockade: atrial or ventricular arrhythmias – Recommended IV dose • 0.01 to 0.1 mg/kg (max 1 mg in infants and 3 mg in children) • Given by slow infusion over 10 minutes – Recommended PO dose • 0.5 to 1 mg/kg/d in divided doses q 6 to 8 – Usual PO dose is 2 to 4 mg/kg/day – Maximum recommended dose is 16 mg/kg/day or 60 mg/day AV Node Independent Re-Entry • Atrial fibrillation – Irregularly irregular – No organized atrial contractility • Atrial flutter – Regular atrial rate, variable conduction • These are extremely common in the postop adult congenital heart patient! – Especially Atrial Fibrillation Management of Afib/Aflutter • Clinically unstable = Cardioversion • Optimization of heart rate – Negative chronotropic agents to slow HR via effect on AV node – Beta-blocker • Metoprolol (IV bolus of 2.5 to 5.0 mg over two min; repeat q5min up to 15 mg total • Esmolol (bolus 0.5 mg/kg over 1min; followed by 50 µg/kg/min, repeat 0.5 mg/kg and increase drip to 100 ug/kg/min Long-term AFib/Flutter • Optimally perform cardioversion to convert to sinus rhythm • Long-term rate control for Afib with Beta-blocker agents – Atenolol, Metoprolol, Nadolol • If remains in Afib, must anti-coagulate Postoperative Rhythm Issues • Arrhythmias are common in the postop period – Depending on the hemodynamic status of the patient, may be life-threatening • Junctional ectopic tachycardia is the most common rhythm issue • Amiodarone is useful for treatment of a broad-spectrum of arrhythmias • AV Block seen with surgery near the AV node – It may resolve…be patient! Conclusion • Use all your ‘tools’ to evaluate the postoperative CHD patient • Use common sense! • Use teamwork!