Principles of Postoperative ICU Management: Part 1

1. Principles of Postoperative ICU Management: Part 1 Allison K. Cabalka, MD Associate Professor of Pediatrics Consultant, Pediatric Cardiology Mayo Clinic

2. Objectives • Describe basic hemodynamic monitoring and evaluation of the postop CHD patient • Review common vasoactive medications used in the ICU • Briefly discuss postoperative arrhythmias and treatment

3. Objectives • Describe basic hemodynamic monitoring and evaluation of the postop CHD patient • Review common vasoactive medications used in the ICU • Briefly discuss postoperative arrhythmias and treatment

4. 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?

5. 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

6. 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

7. Bedside Monitor: Basics PGE1-dependent neonate awaiting neonatal surgery…

8. Bedside Monitor: Basics Heart Rate & Rhythm

9. Bedside Monitor: Basics BP

10. Bedside Monitor: Basics CVP

11. Bedside Monitor: Basics Pulse Oximeter

12. Bedside Monitor: Basics RESP

13. 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

14. Volume Status?

15. 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

16. 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)

17. 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)

18. 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

19. Objectives • Describe basic hemodynamic monitoring and evaluation of the postop CHD patient • Review common vasoactive medications used in the ICU • Briefly discuss postoperative arrhythmias and treatment

20. 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…

21. 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

22. 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

23. Inotropic Drugs

24. 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

25. 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

26. 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

27. 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

28. Epinephrine • Low/medium dose (<0.08 mcg/kg/min): • Mixed beta1 and beta2agonist • 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

29. Epinephrine • Indications: • Depressed ventricular function • Low cardiac output • Systemic hypotension • Side effects: • Ventricular arrhythmia • Hypokalemia • Hyperglycemia • Central venous access is required

30. 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)

31. 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

32. 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

33. What About Vasodilation?

34. Vasodilators: Basic Principles • Work = Δ P x V ΔP-pressure V-Volume that the heart pumps • Decreased blood pressure = decreased work • Afterload = Pressure

35. Nitroprusside • Direct smooth muscle relaxation • Venous and arteriolar relaxation • Decreased afterload • Decreased preload • Decreases SVR and PVR

36. 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

37. What About Vasoconstriction?

38. 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)

39. 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

40. Objectives • Describe basic hemodynamic monitoring and evaluation of the postop CHD patient • Review common vasoactive medications used in the ICU • Briefly discuss postoperative arrhythmias and treatment

41. 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

42. Pediatric Postop Arrhythmia 28/189 (15%) pediatric patients experienced an arrhythmia Arrhythmia # % Correlated with length of bypass time and crossclamp time Delaney J et al, J Thor Cardiovasc Surg 2006

43. Tachycardia Sinus Tachycardia is the most common tachycardia in children

44. 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…

45. Premature Beats • Usually in isolation, PAC or PVC (some PJC) • Not clinically significant • Atrial irritability is common (check lines?) • Surgical manipulation also contributes

46. 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

47. Automatic Focus

48. 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

49. Junctional Ectopic Tachycardia

50. 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