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Hemodynamic Assessment and Invasive Monitoring

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  1. Hemodynamic Assessment and Invasive Monitoring Kevin M. Creamer M.D. Pediatric Critical Care Walter Reed AMC

  2. Introduction Hemodynamic Determinants & Assessment Monitoring Considerations A Cautionary Tale Monitoring indications “Normal Values” Complications Hemodynamic scenarios Overview

  3. Seven Alternatives to Evidence Based Medicine • Eminence Based Medicine • Vehemence Based Medicine • Eloquence Based Medicine • Providence Based Medicine • Diffidence Based Medicine • Nervousness Based Medicine • Confidence Based Medicine

  4. Eminence Based Medicine • Experience is worth any amount of evidence • “making the same mistakes with increasing confidence over an impressive number of years” Fitzgerald, Br Med J, 1999

  5. Introduction • Purpose of repeated hemodynamic assessment and continuous monitoring • Gain an understanding of the patient’s physiologic status • Make timely interventions • Assess effectiveness of therapies • Provide warning of hemodynamic changes that may be dangerous

  6. The heart is a lazy stupid organ, but it is strong like bull Its only algorithm: I must maintain CO!

  7. Hemodynamic Determinants Preload Afterload Contractility Heart Rate Rhythm

  8. Hemodynamic Determinants • Ohm’s Law (V= I X R) • BP = CO X SVR • Important Physiologic principle • manipulation of variables can alter hemodynamics • Ex. BP can be normal in the face of low CO when….

  9. Hemodynamic Determinants • Preload: volume indirectly generates a pressure based on compliance • This is why normal CVP is not an absolute • Afterload: any factor that resists ejection of blood from the heart • Impedance, Inertia, Ejection pressure, Ventricular outflow tract obstruction, and wall stress • SVR is a gross approximation of afterload

  10. Preload HR CO Contractility SV DO2 Afterload Hg CaO2 PaO2 Sat %

  11. Starling’s Law 3 Cardiac performance 2 1 Preload

  12. Hemodynamic Determinants • CO = HR X SV • Preload -Volume • Afterload -Resistance to LV emptying • Contractility -Squeeze • Heart Rate - rate =  SV • Rhythm -Atrial kick 10% CO

  13. Hemodynamic Assessment

  14. Cardiac output I • Pulse quality • Central vs. Peripheral pulses • Differential Temperatures • Dipstick of SVR and indirectly CO • Capillary refill time (CRT)

  15. Cardiac output II • Organ Perfusion • CNS – Alert > Verbal > Pain > Unresponsive ? • Renal - UOP • only organ with easily measured output • Foley catheter is a poor smart man’s PA catheter • Acidosis?

  16. Hemodynamic Assessment • Stroke volume - pulse quality • Preload - Liver size, CXR - heart size • Relative liver size may be better than CVP for initial assessment of preload • SVR - CRT, Pulse pressure, differential temperatures

  17. Inadequate Hemodynamics • Common features • Elevated HR - attempt to  CO • Elevated RR - beware Resp. alkalosis • Decreased pulses -  CO • Depressed LOC -  CO • Acidosis -  CO • Falling UOP -  CO

  18. Distinguishing Exam

  19. Monitoring Considerations • Minimal risk to patient • Noninvasive and painless if possible • Data should be reproducible, relevant and understandable • Provide easy visual or auditory queues

  20. A Cautionary Tale • Virginia PICU 1989 to 1993, • Two separate groups of Intensivists • 78 Infants with RSV disease • Group 1 - (n=38) invasive monitoring • Group 2 - (n=40) less monitoring • Groups comparable re: age, gender, disease severity, and medical Hx. • D. Wilson, (J.Pediatr 1996:128:357-62)

  21. More isn’t better

  22. More might be worse

  23. All children with concerning hemodynamics should be monitored Continuous HR, RR, Pulse ox, intermittent NIBP Consider foley for any patient whose UOP is questionable or to monitor CO Frequent sampling needs require either a large PIV, Art line or CVC Some children who need reliable IV access may need a PIC or central line Monitoring Indications

  24. Paid Advertisement Newman, J Ped Surg, 1986

  25. Indications • Unstable BP: Arterial line • Vasoactive infusion or CVP monitoring: Central Line • Ventricular dysfunction and vascular collapse: Art line and PA Catheter

  26. PA Catheter Measures • CO via thermodilution • PA Pressures • Preload to right (CVP) and Left (PCWP) heart • Allows for calculation of resistances by rearranging Ohm’s law • Most useful in determining which of 3 determinants needs fixing: Preload, Afterload, Contractility CVP PAP T PCWP

  27. Vascular resistance • SVR (MAP – CVP) / CO • PVR (MPAP – PCWP) / CO δBP SVR = CO

  28. CVP CI = CO BSA PAOP (PCWP) SVRI = (MAP - CVP)  CI x 80 PVRI = (MPAP - PCWP)  CI X 80 3-5 mm Hb 3.5-5.5 L/min/m2 4-12mm Hb 800 - 1600 dyne-sec/cm5/m2 80 -240dyne-sec/cm5/m2 “Normal” Values

  29. CaO2 = (Hg X 1.34 X Sat%) + (PaO2 X 0.003) DO2 = CI X CaO2 VO2 = CI X avDo2 17-20cc O2 /dL 400-600 ml X min / M2 140-160 ml X min / M2 “Normal” Values

  30. Estimate Cardiac Index • Normal O2 Consumption < 3 wo 120-130 ml/min/m2 > 3 wo 150-160 ml/min/m2 • CI = VO2 / (A-v DO2 X 10) • Arterial O2 content - venous

  31. Distinguishing Parameters

  32. Complications I • Bleeding - SC > IJ > Fem • Infection - PAC > CVL > Art (Femoral not worse) • Thrombosis - >1wk 1/3 Femoral • Arrhythmia • Pneumothorax • Vascular erosion

  33. Complications II • CVL – 0.24-0.52 infections/100 days • CVL - 241 CVL, 23% minor bleeding, 7 major complications, 5% septicemia • Prospective study of 774 catheters in children • 7/774 significant bleeding (1%) • 3/377 arterial thrombosis (1%) • 11/774 sepsis (1.5%) Salzman 1995 Adv. Ped. Inf., Odetola,CCM(A), 2001, Dis,Luyt, S. Africa 1996, Smith-Wright, CCM, 1984

  34. Catheter Risk • Meta-analysis found duration >7days, replacement over wire, multi vs. single lumen all independent predictors of CRBSI • Biopatch  CRBSI 3.3% to 1.2% • RCT Heparin bonded catheter in 209 pediatric patients • Infection  4% and thrombosis 0% • Mino/Rif impregnated lines  BSI .3% Maki, CCM(A),2001,Pierce, ICM,2000 Darouiche, NEJM, 1999

  35. Hemodynamic Scenarios

  36. Caveats • If your patient has: • UOP > 1cc/kg/hr • No metabolic acidosis • A good hemodynamic exam • Think twice about interventions to “fix” the numbers

  37. Treatment priorities Preload Contractility Afterload

  38. Inotropes • Dopamine - 5 to 10 mcg/kg/min • Dobutamine - 2 to 20 mcg/kg/min • Milrinone - 50 to 75 mcg/kg load over 10 to 20 minutes, then 0.5 to 1 mcg/kg/min (inodilator) • Epinephrine - 0.1 to 0.3 mcg/kg/min

  39. Vasopressors • Dopamine - 10 to 20 mcg/kg/min • Epinephrine - 0.3 to 2 mcg/kg/min • Norepinephrine - 0.05 to 1 mcg/kg/min

  40. Scenario I • A 12yo diabetic with DKA and a pH 7.15 and glucose level of 600 is admitted from the ED. She is is tachycardic with an otherwise normal hemodynamic exam and has two large bore IVs. The PICU nurses wants to know if you are going to place and Arterial Line? YOU REPLY ???

  41. Scenario I • NOT NECESSARILY, Does one of the PIV’s draw blood? • The need is for frequent labs and not ABGs or BP monitoring

  42. Scenario II • A 4mo with HIV, RSV and ARDS has poor perfusion, a HR 180, BP 60/30, and CVP 14 after 80cc/kg of fluid and is on Dopamine and Dobutamine (each at 10mcg/kg/min) • What do you do next?

  43. Scenario II • Do you fix preload, afterload or contractility next ? • An ECHO may help but to titer therapy a PA catheter is indicated

  44. Scenario III • A 12 yo s/p ASD repair has hemodynamic changes 2 hours after surgery. Initially he was warm with HR 90, BP 110/60 and CVP 10, now HR has jumped to 125, BP is 90/70 and CVP is 22 with 1+ pulses and cool extremities • What is going on?

  45. Scenario III • Cardiac Tamponade !! Diminished CO with elevated CVP and narrow pulse pressure • Volume may help transiently but patient needs emergent pericardiocentesis or trip to OR.

  46. Scenario IV • A 10 yo febrile neutropenic patient has a HR 160, BP 80/40, and CVP 5 with warm extremities 1+ pulses, no UOP and no palpable liver after 40cc/kg of saline, 1u PRBCs and 1 pheresis pack of platelets.What is the Dx? • What should be done for monitoring and management?

  47. Scenario IV • You can safely call this an unstable BP and this patient would benefit from continuous arterial monitoring • The patient still requires more preload prior to the initiation of Inotropes

  48. Scenario V • A 2yo with meningococcemia has a HR of 174, BP 66/28, CVP 10, PCWP 8, CI 5.5, PVRI 160, and SVRI 500 with warm ruddy extremities and 1+ pulses on Dopamine 10mcg/kg/min • What is your assessment? • What does the patient need?

  49. Scenario V • Vascular tone!! The patient has adequate CO but no vascular tone. Epinephrine or norepinephrine added would help improve BP and vital organ perfusion

  50. Interactive Scenario Choices • 2yo with Meningococcemia • 10yo with Pneumonia s/p Cardiac Arrest • Done with scenarios