Hemodynamic Assessment and Invasive Monitoring Kevin M. Creamer M.D. Pediatric Critical Care Walter Reed AMC
Introduction Hemodynamic Determinants & Assessment Monitoring Considerations A Cautionary Tale Monitoring indications “Normal Values” Complications Hemodynamic scenarios Overview
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
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
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
The heart is a lazy stupid organ, but it is strong like bull Its only algorithm: I must maintain CO!
Hemodynamic Determinants Preload Afterload Contractility Heart Rate Rhythm
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….
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
Preload HR CO Contractility SV DO2 Afterload Hg CaO2 PaO2 Sat %
Starling’s Law 3 Cardiac performance 2 1 Preload
Hemodynamic Determinants • CO = HR X SV • Preload -Volume • Afterload -Resistance to LV emptying • Contractility -Squeeze • Heart Rate - rate = SV • Rhythm -Atrial kick 10% CO
Cardiac output I • Pulse quality • Central vs. Peripheral pulses • Differential Temperatures • Dipstick of SVR and indirectly CO • Capillary refill time (CRT)
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?
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
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
Monitoring Considerations • Minimal risk to patient • Noninvasive and painless if possible • Data should be reproducible, relevant and understandable • Provide easy visual or auditory queues
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)
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
Paid Advertisement Newman, J Ped Surg, 1986
Indications • Unstable BP: Arterial line • Vasoactive infusion or CVP monitoring: Central Line • Ventricular dysfunction and vascular collapse: Art line and PA Catheter
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
Vascular resistance • SVR (MAP – CVP) / CO • PVR (MPAP – PCWP) / CO δBP SVR = CO
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
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
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
Complications I • Bleeding - SC > IJ > Fem • Infection - PAC > CVL > Art (Femoral not worse) • Thrombosis - >1wk 1/3 Femoral • Arrhythmia • Pneumothorax • Vascular erosion
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
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
Caveats • If your patient has: • UOP > 1cc/kg/hr • No metabolic acidosis • A good hemodynamic exam • Think twice about interventions to “fix” the numbers
Treatment priorities Preload Contractility Afterload
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
Vasopressors • Dopamine - 10 to 20 mcg/kg/min • Epinephrine - 0.3 to 2 mcg/kg/min • Norepinephrine - 0.05 to 1 mcg/kg/min
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 ???
Scenario I • NOT NECESSARILY, Does one of the PIV’s draw blood? • The need is for frequent labs and not ABGs or BP monitoring
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?
Scenario II • Do you fix preload, afterload or contractility next ? • An ECHO may help but to titer therapy a PA catheter is indicated
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?
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.
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?
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
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?
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
Interactive Scenario Choices • 2yo with Meningococcemia • 10yo with Pneumonia s/p Cardiac Arrest • Done with scenarios