Transcript Shock in the Pediatric Patient: or Oxygen Doesn’t Go Where
Shock in the Pediatric Patient: or Oxygen Don’t Go Where the Blood Won’t Flow!
James D. Fortenberry MD FAAP, FCCM Medical Director, PICU Division of Critical Care Medicine Children’s Healthcare of Atlanta
Objectives
Define shock and its different categories Review basic physiologic aspects of shock Describe management of shock including:
oxygen supply and demand
fluid resuscitation
crystalloid vs. colloid controversy
vasopressor support
Definition of Shock
Uncontrolled blood or fluid loss Blood pressure less than 5th percentile for age Altered mental status, low urine output, poor capillary refill None of the above
Definition of Shock
An acute complex pathophysiologic state of circulatory dysfunction which results in a failure of the organism to deliver sufficient amounts of oxygen and other nutrients to satisfy the requirements of tissue beds
SUPPLY
<
DEMAND
Definition of Shock
Inadequate tissue perfusion to meet tissue demands Usually result of inadequate blood flow and/or oxygen delivery
Shock is not a blood pressure diagnosis!!
Characteristics of Shock
End organ dysfunction:
reduced urine output
altered mental status poor peripheral perfusion Metabolic dysfunction:
acidosis altered metabolic demands
Essentials of Life
Gas exchange capability of lungs Hemoglobin Oxygen content Cardiac output Tissues to utilize substrate
Arterial Oxygen Content
100 mm Hg Hgb 15 gm/100 mL Hemoglobin SaO 2 97% Oxygen Saturation O 2 bound to Hgb + + PaO 2 100 mmHg Partial Pressure O 2 in plasma
Oxygen Delivery
DO 2=Cardiac Output x 1.34 (Hgb x SaO 2 ) + Pa0 2 x 0.003
Oxygen Express
O 2 O 2 O 2 O 2 O 2 O 2 Ca0 2 O 2 O 2 O 2 O 2 O 2 O 2
Cardiac Output
The volume of blood ejected by the heart in one minute 4 - 8 liters / minute
Cardiac Output
C.O.=Heart Rate x Stroke Volume
Heart rate Stroke volume:
Preload- volume of blood in ventricle
Afterload- resistance to contraction
Contractility- force applied
Cardiac Output
C.O.=Mean arterial pressure (MAP) - CVP/SVR
To improve CO: MAP CVP SVR
Preload Afterload Contractility Stroke Volume x Heart Rate O 2 Content x Cardiac Output x Resistance O 2 Delivery
Classification of Shock
Hypovolemic
dehydration,burns, hemorrhage
Distributive
septic, anaphylactic, spinal
Cardiogenic
myocarditis,dysrhythmia Obstructive
tamponade,pneumothorax
Compensated
organ perfusion is maintained Uncompensated
Circulatory failure with end organ dysfunction Irreversible
Irreparable loss of essential organs
Mechanical Requirements for Adequate Tissue Perfusion
Fluid Pump Vessels Flow
Hypovolemic Shock:
Inadequate Fluid Volume (decreased preload)
Hypovolemic Shock: Causes
Fluid depletion
internal external Hemorrhage
internal external
Cardiogenic Shock:
Pump Malfunction (decreased contractility)
Cardiogenic Shock: Causes
Electrical Failure Mechanical Failure
Cardiomyopathy metabolic
anatomic hypoxia/ischemia
Distributive Shock
Abnormal Vessel Tone (decreased afterload)
Distributive Shock
Vasodilation Venous Pooling Decreased Preload Maldistribution of regional blood flow
Distributive Shock:
Causes
Sepsis Anaphylaxis Neurogenesis (spinal) Drug intoxication (TCA, calcium, Channel blocker)
Septic Shock Decreased Volume Decreased Pump Function Abnormal Vessel Tone
Cardiac Output
C.O.=Heart Rate x Stroke Volume
Heart rate Stroke volume:
Preload- volume of blood in ventricle
Afterload- resistance to contraction
Contractility- force applied
Clinical Assessment
Heart rate Peripheral circulation
capillary refill
pulses extremity temperature Pulmonary End organ perfusion
brain kidney
Improving Stroke Volume:
Therapy for Cardiovascular Support
Preload Contractility Volume Inotropes Afterload Vasodilators
Septic Shock
Early (“Warm”) Decreased peripheral vascular resistance Increased cardiac output Late (“Cold”) Increased peripheral vascular resistance Decreased cardiac output
Assessment of Circulation
Early Late Heart rate Blood pressure Peripheral circulation Tachycardia Tachycardia/ Bradycardia Normal Decreased Warm/Cool Decreased/ Increased pulses Cool Decreased pulses
Heart Rate and Perfusion Pressure (MAP-CVP) Parameters by Age
Age Term newborn < 1 < 2 < 7 < 15 Heart Rate MAP-CVP 120-180 55 120-180 120-160 120-160 90-140 60 65 65 65
Assessment of Circulation
Early Late End-organ: Skin Brain Kidneys Decreased cap refill Irritable, restless Oliguria Very decreased cap refill Lethargic, unresponsive Oliguria, anuria
OBSTRUCTIVE SHOCK
OBSTRUCTED FLOW
Obstructive Shock: Causes
Pericardial tamponade Pulmonary embolism Pulmonary hypertension
Hemodynamic Assessment of Shock
Type of Shock Preload Afterload Contractility Cardiogenic Hypovolemic Septic Early Late Obstructive
Cardiac Output
Distributive
Goals of Resuscitation
Overall goal:
increase O 2 delivery decrease demand O 2 content Cardiac output
Treatment
Sedation/analgesia Blood pressure
Principles of Management
A: Airway
patent upper airway B: Breathing
adequate ventilation and oxygenation C: Circulation
optimize
cardiac function oxygenation
Act quickly, Think slowly.
Greek Proverb
Airway Management
Patients in shock have:
O 2 delivery progressive respiratory fatigue/failure energy shunted from vital organs
afterload
Airway Management
Early intubation provides:
O 2 delivery and content controlled ventilation which:
reduces metabolic demand allows C.O. to vital organs
Therapy
Vagolysis Chromotropy Preload Heart Rate Stroke Volume Afterload Contractility Volume CVP Vasodilators Vasoconstrictors Correct acidosis hypoxia hypoglycemia Inotropic agents
Colloid
Fluid Choices
Crystalloid
Crystalloids
Hypotonic Fluids (D 5 1/4 NS)
No role in resuscitation Maintenance fluids only
Fluids, Fluids, Fluids
Key to most resuscitative efforts Give generously and reassess
Crystalloids
Isotonic Fluids
Intravascular volume expansion Hauser:
crystalloids rapidly redistribute Lethal animal model
NS = good resuscitative fluid 4x blood volume to restore hemodynamics
Crystalloids
Isotonic Fluids
2 trauma studies
crystalloids = colloids but:
4x amount longer time to resuscitation
Crystalloids
Complications
Under-resuscitation
renal failure Over-resuscitation
pulmonary edema
peripheral edema
Crystalloids
Summary Crystalloids less effective than equal volume of colloids
Preferred when 1 o and/or electrolytes deficit is water Good in initial resuscitation to restore extracellular volume Hypertonic solutions however, may act as plasma volume expanders
Fluid Transport
Oncotic pressure (tendency to pull unit) Hydrostatic pressure (tendency to drive unit) Capillary
Colloids
Albumin
Hepatic production MW = 69,000 80% of COP Serum t 1/2 : 18 hours endogenous 16 hours exogenous
Colloids
Hydroxyethyl Starch (Hespan)
Synthetic
Derived from corn starch Average MW = 69,000 Stable, nonantigenic
Used for volume expansion Renal excretion
t 1/2 2-67 hours 90% gone in 42 days
Colloids
Hydroxyethyl Starch (Hespan)
Greater in COP than albumin Longer duration of action 0.006% adverse reactions No effect on blood typing Prolongs PT, PTT and clotting times Dosage
20 ml/Kg/day
max 1500 ml/day
Fluid Choices
Based on:
type of deficit urgency of repletion pathophysiology of condition plasma COP
Fluid Choices
Crystalloids for initial resuscitation PRBC’s to replace blood loss
Fluid Management in Pediatric Septic Shock
Emphasis on the golden hour Early aggressive use of fluids may improve outcome Titrate-Reassess!
Clinical Practice Parameters, Carcillo et al., CCM, 2002
Alpha-Beta Meter
Dopamine Epinephrine
ß
Inotropes
Agent Site of action Dopamine Dopaminergic
Dose (
g/kg/min) 1-3 5-10 Dobutamine
and
11-20 1-20 Epinephrine
0.05-1.0
Norepinephrine
0.05-1.0
Nitroprusside Milrinone Vasodilator Arterial > venous PDE inhibitor 0.5-1.0
0.5-0.75
Effects Renal vasodilator Inotrope Vasoconstriction Increase PVR Inotrope Vasodilation Inotrope Tachycardia Profound vasoconstriction Inotrope Vasodilation Inotrope Vasodilator
Dopamine Activity
0.5-5.0 mcg/kg/min - dopaminergic receptors 2.0-10 mcg/kg/min - beta receptors (inotrope) 10-20 mcg/kg/min - alpha and beta receptors Over 20 mcg/kg/min - alpha receptors (pressors)
A Rational Approach to Shock in the Pediatric Patient
Shock / Hypotension Volume Resuscitation Signs of adequate circulation Adequate MAP Yes NO NO pressors
A Rational Approach to Pressor Use in the PICU
Signs of adequate circulation Adequate MAP NO Dopamine Inadequate MAP Dopamine and/or Norepinephrine
A Rational Approach to Pressor Use in the PICU
Dopamine and/or norepinephrine adequate MAP CO Dobutamine or Milrinone Inadequate MAP low C.O.
tachycardia epinephrine phenylephrine??
“New” Therapies in Septic Shock
Steroids Vasopressin Activated Protein C (Xigris) in septic shock
Management of Pediatric Septic Shock: The Golden Hour
First 15 minutes Emphasis on response to volume
Clinical Practice Parameters, Carcillo et al., CCM, 2002
Patients don’t suddenly deteriorate, healthcare professionals suddenly notice!
Anonymous