Transcript SHOCK IN CHILDREN - UT Health Science Center

Pediatric Resident Curriculum for the PICU
UTHSCSA
SHOCK IN CHILDREN
Pediatric Resident Curriculum for the PICU
UTHSCSA
Definition
Circulatory system failure to supply
oxygen and nutrients to meet cellular
metabolic demands
Pediatric Resident Curriculum for the PICU
UTHSCSA
Other Definitions
• Blood Pressure
BP = CO x SVR
• Cardiac Output
CO = SV X HR
• Vascular Tone (SVR)
– Regulated by several mechanisms
Pediatric Resident Curriculum for the PICU
UTHSCSA
Oxygen Delivery
• DO2 = CO x CaO2 x 10
– Remember: CO depends on HR, preload,
afterload, and contractility
• CaO2 = Hgb x 1.34 x SaO2 + (PaO2 x 0.003)
– Remember: hemoglobin carries more than 99%
of oxygen in the blood under standard
conditions
Pediatric Resident Curriculum for the PICU
UTHSCSA
Hemodynamics
Myocardial
Contractility
Stroke Volume
Cardiac Output
Blood
Pressure
Preload
Afterload
Heart Rate
Systemic Vascular
Resistance
Textbook of Pediatric Advanced Life Support, 1988
Pediatric Resident Curriculum for the PICU
UTHSCSA
Defending the blood pressure
• Neural Sympathetic
– Baroreceptors
• Carotid Body
• Aortic Arch
– Volume receptors
• Right Atrium
• Pulmonary vascular
– Chemoreceptors
• Aortic and carotid
• Medullary
– Cerebral ischemic
response
• Humoral
– Adrenal medulla
• Catecholamines
– Hypothalamopituitary
response
• Adrenocorticotropic
hormone
• Vasopressin
– Renin-angiotensinaldosterone system
Pediatric Resident Curriculum for the PICU
UTHSCSA
Cardiovascular function
• Cardiac Output
 Clinical Assessment
• peripheral perfusion, temperature, capillary
refill, urine output, mentation, acid-base
status
 CO = HR x SV
• HR responds the quickest
• SV is a function of three variables
– preload, afterload, and myocardial
contractility
• A noncompliant heart cannot increase SV
Pediatric Resident Curriculum for the PICU
UTHSCSA
Stroke Volume
• Preload (LVEDV)
– Reflects patient’s volume status
– CVP or PCWP
– Starling curve
• Afterload
– The resistance to ventricular ejection
– Two variables:
• vascular tone and transmural pressure
• Myocardial Contractility (“squeeze”)
– Many factors including coronary perfusion,
baseline myocardial function, use of cardiotonic
medications
Pediatric Resident Curriculum for the PICU
UTHSCSA
Classification of Shock
• COMPENSATED
– blood flow is normal or increased and may be
maldistributed; vital organ function is
maintained
• UNCOMPENSATED
– microvascular perfusion is compromised;
significant reductions in effective circulating
volume
• IRREVERSIBLE
– inadequate perfusion of vital organs; irreparable
damage; death cannot be prevented
Pediatric Resident Curriculum for the PICU
UTHSCSA
Other Classifications
•
•
•
•
Hypovolemic or Hemorrhagic
Cardiogenic
Obstructive
Distributive
Pediatric Resident Curriculum for the PICU
UTHSCSA
Cardiovascular Changes in Shock
Type
Preload Afterload
Contractility
Cardiogenic



Hypovolemic


No change
Distributive



Septic
early


late




Pediatric Resident Curriculum for the PICU
UTHSCSA
Evaluation
• Regardless of the cause: ABC’s
– First assess airway patency, ventilation, then
circulatory system
• Respiratory Performance
– Respiratory rate and pattern, work of breathing,
oxygenation (color), level of alertness
• Circulation
– Heart rate, BP, perfusion, and pulses, liver size
– CVP monitoring may be helpful
Pediatric Resident Curriculum for the PICU
UTHSCSA
Evaluation
• Early Signs of Shock
– sinus tachycardia
– delayed capillary refill
– fussy, irritable
• Late Signs of Shock
– bradycardia
– altered mental status (lethargy, coma)
– hypotonia, decreased DTR’s
– Cheyne-Stokes breathing
– hypotension is a very late sign
– Lower limit of SBP = 70 + (2 x age in years)
Pediatric Resident Curriculum for the PICU
UTHSCSA
Cardiovascular Assessment
• Heart Rate
– Too high: 180 bpm for
infants, 160 bpm for
children >1year old
• Blood Pressure
– Lower limit of SBP =
70 + (2 x age in years)
• Peripheral Pulses
– Present/Absent
– Strength (diminished,
normal, bounding)
• Skin Perfusion
–
–
–
–
Capillary refill time
Temperature
Color
Mottling
• CNS Perfusion
– Recognition of
parents
– Reaction to pain
– Muscle tone
– Pupil size
• Renal Perfusion
– UOP >1cc/kg/hr
Pediatric Resident Curriculum for the PICU
UTHSCSA
Treatment
Airway management
– Always provide supplemental oxygen
– Endotracheal intubation and controlled
ventilation is suggested if respiratory failure or
airway compromise is likely
• elective is safer and less difficult
• decrease negative intrathoracic pressure
• improved oxygenation and O2 delivery and
decreased O2 consumption
• can hyperventilate if necessary
Pediatric Resident Curriculum for the PICU
UTHSCSA
Treatment
Circulation
– Based on presumed etiology
– Rapid restoration of intravascular volume
• PIV-if unstable you have 60-90 seconds
• I.O. if less than 4-6 years old
• Central venous catheter
• Use isotonic fluid: NS, LR, or 5% albumin
• PRBC’s to replace blood loss or if still
unstable after 60cc/kg of crystalloid
– anemia is poorly tolerated in the stressed,
hypoxic, hemodynamically unstable patient
Pediatric Resident Curriculum for the PICU
UTHSCSA
Vasoactive/Cardiotonic Agents
• Dopamine
–
–
–
–
1-5 mcg/kg/min: dopaminergic
5-15 mcg/kg/min: more beta-1
10-20 mcg/kg/min: more alpha-1
may be useful in distributive shock
• Dobutamine
– 2.5-15 mcg/kg/min: mostly beta-1, some beta-2
– may be useful in cardiogenic shock
• Epinephrine
– 0.05-0.1 mcg/kg/min: mostly beta-1, some beta-2
– > 0.1 to 0.2 mcg/kg/min: alpha-1
Pediatric Resident Curriculum for the PICU
UTHSCSA
Vasoactive/Cardiotonic Agents
• Norepinephrine
– 0.05-0.2mcg/kg/min: only alpha and beta-1
– Use up to 1mcg/kg/min
• Milrinone
– 50mcg/kg load then 0.375-0.75mcg/kg/min:
phosphodiesterase inhibitor; results in increased
inotropy and peripheral vasodilation (greater effect
on pulmonary vasculature)
• Phenylephrine
– 0.1-0.5mcg/kg/min: pure alpha
Pediatric Resident Curriculum for the PICU
UTHSCSA
Hypovolemic
• # 1 cause of death in children worldwide
• Causes
• Water Loss (diarrhea, vomiting with poor PO
intake, diabetes, major burns)
• Blood Loss (obvious trauma; occult bleeding
from pelvic fractures, blunt abdominal
trauma, “shaken baby”)
• Low preload leads to decreased SV and
decreased CO.
• Compensation occurs with increased HR and
SVR
Pediatric Resident Curriculum for the PICU
UTHSCSA
Hypovolemic Shock
• Mainstay of therapy is fluid
• Goals
– Restore intravascular volume
– Correct metabolic acidosis
– Treat the cause
• Degree of dehydration often underestimated
– Reassess perfusion, urine output, vital signs...
• Isotonic crystalloid is always a good choice
– 20 to 50 cc/kg rapidly if cardiac function is
normal
– NS can cause a hyperchloremic acidosis
Pediatric Resident Curriculum for the PICU
UTHSCSA
Treatment
Solution
Na+
NS
154
LR
130
Plasmalyte 140
Cl154
109
98
K+
0
4
5
Ca++
0
3
0
Mg++
0
0
3
Buffer
None
Lactate
Acetate
& Gluconate
 Inotropic and vasoactive drugs are not a substitute for
fluid, however...
– Can have various combinations of hypovolemic and
septic and cardiogenic shock
– May need to treat poor vascular tone and/or poor
cardiac function
Pediatric Resident Curriculum for the PICU
UTHSCSA
Hemorrhagic Shock
• Treatment is PRBCs or whole blood
– Treat the cause if able (stop the bleeding)
– Transfuse if significant blood loss is known or
if patient unstable after 60cc/kg crystalloid
• In an emergency can give group O PRBCs
before cross matching is complete or type
specific non-cross-matched blood products
Pediatric Resident Curriculum for the PICU
UTHSCSA
Cardiogenic
• Low CO and high systemic vascular resistance
• Result of primary cardiac dysfunction:
 A compensatory increase in SVR occurs to
maintain vital organ function
 Subsequent increase in LV afterload, LV
work, and cardiac oxygen consumption
 CO decreases and ultimately results in
volume retention, pulmonary edema, and
RV failure
Pediatric Resident Curriculum for the PICU
UTHSCSA
Cardiogenic Shock
Etiologies
• Congenital heart
disease
• Arrhythmias
• Ischemic heart
disease
• Myocarditis
• Myocardial injury
• Acute and chronic
drug toxicity
• Late septic shock
• Infiltrative diseases
– mucopolysaccharidoses
– glycogen storage
diseases
• Thyrotoxicosis
• Pheochromocytoma
Pediatric Resident Curriculum for the PICU
UTHSCSA
Cardiogenic Shock
• Initial clinical presentation can be identical to
hypovolemic shock
• Initial therapy is a fluid challenge
• If no improvement or if worsens after giving
volume, suspect cardiogenic shock
• Usually need invasive monitoring, further
evaluation, pharmacologic therapy
• Balancing fluid therapy and inotropic support can
be very difficult.
– Call an intensivist and/or a cardiologist
Pediatric Resident Curriculum for the PICU
UTHSCSA
Obstructive Shock
• Low CO secondary to a physical obstruction to flow
• Compensatory increased SVR
• Causes:
– Pericardial tamponade
– Tension pneumothorax
– Critical coarctation of the aorta
– Aortic stenosis
– Hypoplastic left heart syndrome
Pediatric Resident Curriculum for the PICU
UTHSCSA
Obstructive Shock
• Initial clinical presentation can be identical to
hypovolemic shock
• Initial therapy is a fluid challenge
• Treat the cause
– pericardial drain, chest tube, surgical
intervention
– if the patient is a neonate with a ductal
dependent lesion then give PGE
• Further evaluation, invasive monitoring,
pharmacologic therapy, appropriate consults
Pediatric Resident Curriculum for the PICU
UTHSCSA
Distributive Shock
• High CO and low SVR (opposite of hypovolemic,
cardiogenic, and obstructive)
• Maldistribution of blood flow causing
inadequate tissue perfusion
• Due to release of endotoxin, vasoactive
substances, complement cascade activation,
and microcirculation thrombosis
• Early septic shock is the most common form
Pediatric Resident Curriculum for the PICU
UTHSCSA
Distributive Shock
• Goal is to maintain intravascular volume and
minimize increases in interstitial fluid (the
primary problem is a decrease in SVR)
– Use crystalloid initially
– Additional fluid therapy should be based on
lab studies
– Can give up to 40cc/kg without monitoring
CVP
– Vasoactive/Cardiotonic agents often
necessary
– Treat the cause (i.e.. antimicrobial therapy)
Pediatric Resident Curriculum for the PICU
UTHSCSA
Distributive Shock
Etiologies
•
•
•
•
•
•
Anaphylaxis
Anaphylactoid reactions
Spinal cord injury/spinal shock
Head injury
Early sepsis
Drug intoxication
– Barbiturates, Phenothiazines,
Antihypertensives
Pediatric Resident Curriculum for the PICU
UTHSCSA
Metabolic Issues
Acid-Base
• Metabolic acidosis develops secondary to tissue
hypoperfusion
• Profound acidosis depresses myocardial
contractility and impairs the effectiveness of
catecholamines
• Tx: fluid administration and controlled
ventilation
• Buffer administration
– Sodium Bicarbonate 1-2meq/kg or can calculate a
1/2 correction = 0.3 x weight (kg) x base deficit
– hyperosmolarity, hypocalcemia, hypernatremia,
left-ward shift of the oxyhemoglobin dissociation
curve
Pediatric Resident Curriculum for the PICU
UTHSCSA
Metabolic Issues
Electrolytes
• Electrolytes
– Calcium is important for cardiac function and
for the pressor effect of catecholamines
– Hypoglycemia can lead to CNS damage and is
needed for proper cardiovascular function
– Check the BUN and creatinine to evaluate renal
function
– Hyperkalemia can occur from renal dysfunction
and/or acidosis
Pediatric Resident Curriculum for the PICU
UTHSCSA
Metabolic Issues
Special Topics
Congenital adrenal hyperplasia
• Infant presents in shock, usually in the second
week of life, typically a boy, with metabolic
acidosis, hyponatremia, hypoglycemia, and
hyperkalemia
Hyperammonemia
• mild elevations are common with shock
• levels > 1000 are consistent with inborn errors
of metabolism
• consider Reye Syndrome, toxins, hepatic
failure
Pediatric Resident Curriculum for the PICU
UTHSCSA
Other Studies
• Look for etiology of shock
• Evaluate hemoglobin, hematocrit, and platelet
count
– Should be followed as these values may drop after
fluid resuscitation
• Shock from any etiology can lead to DIC and
end organ damage
– CBC, PT, INR, PTT, Fibrinogen, Factor V, Factor
VIII, D-dimer, and/or FDPs
– Check LFT’s, follow CNS and pulmonary status
Pediatric Resident Curriculum for the PICU
UTHSCSA
Other Studies II
• Think about inborn errors of metabolism
–
–
–
–
–
Lactate and pyruvate
Ammonium, LFTs
Plasma amino acids, urine organic acids
Urinalysis with reducing substances
Urine tox screen
Pediatric Resident Curriculum for the PICU
UTHSCSA
Conclusion
• Goal of therapy is identification, evaluation, and
treatment of shock in its earliest stage
• Initial priorities are for the ABC’s
• Fluid resuscitation begins with 20cc/kg of
crystalloid or 10cc/kg of colloid
• Subsequent treatment depends on the etiology of
shock and the patient’s hemodynamic condition
• Successful resuscitation depends on early and
judicious intervention