Shock

• Shock is a critical condition that develops when oxygenation and delivery of nutrients to tissues is insufficient to meet the body’s requirements for survival.
• Blood pressure may be low, normal, or high.
• All types of shock may result in impaired organ functioning of multiple body systems.
• There are 4 main causes of shock: Inadequate blood volume or hemoglobin carrying capacity, impaired distribution and insufficient cardiac function, and obstructive blood flow.
• Stressors such as fever, pain, respiratory distress, trauma, and infection may worsen symptoms of shock.
• Shock may lead to tissue death, anaerobic metabolism, lactic acid and CO₂ buildup in tissues, organ damage and failure.
• In order for tissues to receive proper oxygenation, there must be adequate amounts of O₂ in the bloodstream, adequate blood flow to tissues, and an appropriate distribution of blood to tissues.
• Oxygen content in the blood is determined by hemoglobin concentration and oxygen saturation of the hemoglobin.
• Cardiac output is the volume of blood that the heart pumps each minute.
• Stroke volume refers to the volume of blood pumped with each heartbeat.
• Cardiac Output=Stroke volume x heart rate.
• Infants have a small stroke volume that cannot increase by much. They rely on an increased heart rate to maintain cardiac output
• Distribution of blood flow is determined by the size of blood vessels. Large vessels have low resistance. Small vessels have high levels of vascular resistance.
• Vasoconstriction or vasodilation impact vascular resistance even if blood flow is adequate.
• Stroke volume is determined by preload, contractility, and afterload.
• Preload refers to the volume of blood in a ventricle prior to a contraction.
• Contractility is the strength of a contraction.
• CAfterload is the resistance that the ventricle is ejecting against.
• Reduced preload is the most common cause of low stroke volume and cardiac output.
• Preload, Contractility, and Afterload
• Reduced preload is the most common cause of low stroke volume and cardiac output. It results in hypovolemic shock. Causes include blood loss, dehydration, and vasodilation.
• Poor contractility, also known as myocardial dysfunction, impairs stroke volume and cardiac output. It results in cardiogenic shock. It is due to the heart’s inability to pump properly. Abnormalities in the tissues of the heart, myocarditis, hypoglycemia, and toxic doses of drugs such as calcium channel blockers impair contractility.
• High afterload is an uncommon cause of shock among children. Cardiogenic shock result states which may increase afterload include pulmonary hypertension, congenital deformities, and HTN.

Compensatory Mechanisms

• Compensated shock occurs when a child is able to maintain an adequate blood pressure, yet signs of impaired perfusion are present. Oxygenation and nutrient supply to the tissues is inadequate.
• Attempt to maintain O₂ and nutrient supplies to the body.
• Tachycardia is the body’s first compensatory response.
• Blood flow is shunted to the vital organs. This is called a selective increase in vasoconstriction (SVR). As a result, peripheral circulation is limited. Capillary refill time slows, extremities cool, peripheral pulses become weaker, and urine production diminishes. An increase in SVR raises the diastolic BP.
• An increase in contractility is an increase in the strength of the contraction of the heart. The ventricles empty more completely.
• An increase in smooth muscle tone aids blood return to the heart.
• Blood pressure is the result of SVR and cardiac output.
• Compensatory mechanisms may initially maintain blood pressure.
• Do not rely on blood pressure alone to determine if shock is present or not.
• Pulse pressure is the difference between systolic and diastolic BP. The pulse pressure is often narrow; however, if sepsis occurs it may widen.
• SVR may increase or decrease with septic shock. Hypotension may appear as a late sign of septic shock.

Signs that Compensatory Mechanisms are Failing

• Increasing heart rate
• Weak or absent peripheral pulses
• Narrowing pulse pressure
• Cool extremities
• Delayed capillary refill
• Decreasing level of consciousness
• Low blood pressure

Signs of Clinical Improvement

• Pulse and blood pressure within normal limits for child’s age
• Pulses readily palpable
• Capillary refill time <2 seconds
• Awake, alert and oriented within normal limits for age
• Urinary output >1 mL/kg/hr.
• Normal acid base balance
• Central venous O₂ saturation >70
• Warm extremities

Shock Treatment

• Early treatment of shock improves the likelihood of improved outcomes and saves lives.
• Treatment of shock focuses on improving oxygenation and perfusion. These goals restore organ functions, prevent acute and long-term complications, and reduce mortality.
• The four main types of shock are:
  • Hypovolemic (e.g., hemorrhage, fluid loss, severe dehydration)
  • Distributive (e.g., septic shock, anaphylactic shock, neurogenic shock)
  • Cardiogenic (e.g., congenital heart disease, myocarditis, arrhythmia, poison, trauma)
  • Obstructive (e.g., cardiac tamponade, tension pneumothorax, congenital heart defect)
• A child in shock may be suffering from more than one type of shock.

Initial Treatment

Initial treatment of shock focuses on improved oxygenation, perfusion, and supplying metabolic demand. Prompt interventions are needed to reverse shock and treat the underlying cause of shock.

• Positioning: If the child is awake and stable, support the positon of comfort. A small child may be calmer if held by a parent or other caregiver. Comfort is an important consideration to decrease stress and reduce oxygen demand.
• Airway and Breathing: Ensure patent airway, high flow O₂, mechanical ventilation.
• Vascular Access: Needed for fluid and medication administration. Peripheral, intraosseous(IO), or central line placement. If a peripheral line cannot be quickly placed, obtain IO access immediately.
• Fluids: Begin as soon as vascular access obtained. Give a 20 mL/kg bolus of 5-20 minutes. If cardiogenic shock is suspected, give 5-10 mL/kg over 10 to 20 minutes. Reassess and re-bolus as needed to maintain BP and signs of adequate perfusion.
• Monitoring: Includes ongoing assessment by care providers as well as the use of technology. Common tools include pulse oximeter, vital signs monitoring, evaluation of mental status, and urinary output.
• Frequent Reassessment: The condition of a child in shock may change very quickly. Continually evaluate respiratory, cardiac, and neurologic status so trends can be identified, preparations can be made for future interventions, and the effectiveness of treatment can be determined.
• Laboratory Studies: Use lab tests to identify underlying causes of shock, evaluate interventions, plan treatment, and determine the severity of shock.
• Medication: Medications are used to normalize cardiovascular function and improve oxygenation.
• Expert Consultation: Specialists may be needed to provide surgical interventions, correct metabolic and other abnormalities. Consult experts as soon as possible.

Infusion of Fluids During Shock

• Crystalloid Isotonic Solutions
  • Most common initial fluid type administered to children in shock
  • Distributed in extracellular space, so large amounts of crystalloid solution may be needed to restore intravascular volume
  • Examples include lactated Ringer’s (LR) and normal saline (NS)
  • Inexpensive, commonly available, well tolerated
  • Large volume required may be detrimental for children with cardiac or kidney illness; may cause pulmonary edema
• Colloid Solutions
  • Colloidal solutions stay in intravascular compartment longer than crystalloid solutions
  • Less volume needs to be infused compared to crystalloids
  • Examples include fresh frozen plasma (FFP), albumin, and synthetic plasma expanders such as hetastarch and dextran
  • Less available, preparation may be time consuming, blood-based products may cause allergic reactions;synthetics may cause coagulation problems;both may cause pulmonary edema
  • Beneficial if additional fluids needed or for children suffering from malnutrition or kidney disease

Tips for Fluid Administration

• Frequently evaluate the effects of fluid administration by using observation and laboratory values.
• Modification of fluid administration may be needed for children suffering from burns, poisoning, ingestion of cardiac drugs, or DKA.
• Infusion devices designed for children may deliver insufficient amounts of rapid fluids.
• Place as large an IV catheter as possible.
• Use a 3-way stopcock on the IV tubing.
• Push IV fluids via a 30 or 60 mL syringe, pressure bag, or rapid infusion equipment.
• Standard infusion pumps may not deliver an adequate amount of volume rapidly.

Administration of Blood Products

• During hemorrhagic shock, blood is administered if perfusion remains inadequate despite administration of two to three 20mL/kg boluses of isotonic crystalloid.
• Fully cross-matched blood may not be available. If cross-matched blood is unavailable and a transfusion is needed, use type specific blood. If type specific blood is unavailable, use type O- blood for females or type O- or O+ for males if needed to prevent cardiac arrest.
• Rapid infusion of blood may lead to hypothermia, coagulation problems, myocardial dysfunction, ionized hypocalcemia, and hypotension.
• Limit complications by administering warm blood and having calcium IV available.
• Using plasma in addition to RBCs may lead to a better outcome if a large volume of blood product is needed
• Administer 3 mL of crystalloid for every milliliter of blood lost
• Rapidly infuse crystalloid at 20 mL/kg.
• If a child is hemodynamically unstable after 2-3 boluses of crystalloid, consider administering PRBCs in 10 mL/kg boluses.

Estimating Blood Loss

• Mild: <30%. Tachycardia, thready pulses peripherally. Normal systolic BP and pulse pressure. Irritable, confused, anxious. Skin is cool. Capillary refill time is slow. Mottling may occur. Low urinary output. Compensated shock.
• Moderate: 30%-45%. Very rapid HR, thready central pulses, peripheral pulses not palpable, narrowed pulse pressure. Low normal systolic BP. Lethargic, diminished response to pain. Cyanosis present. Very slow capillary refill. Scant urine. Hemorrhagic shock.
• Severe: >45%. Tachycardia deteriorating to bradycardia. Weak or absent peripheral pulses. Marked hypotension. Diastolic pressure may be absent. Widened pulse pressure. Comatose. Skin pale, cold. Anuria. Hemorrhagic shock.

Hypovolemic Shock

• Non-hemorrhagic vs. hemorrhagic.
• Provide rapid,adequate fluid volume.
• Determine extent of hypovolemia by clinical presentation, type of fluid loss, laboratory studies.
• Severity determined by % of fluid loss.
• Normalize acid-base balance.
• Reverse metabolic imbalances.
• Initially administer 20mL/kg bolus of crystalloid. Repeat boluses as needed.
• Medications are not commonly used to treat hypovolemic shock. Epinephrine is sometimes administered to increase cardiac contractility and vascular tone.
• Medications are not commonly used to treat hypovolemic shock. Epinephrine is sometimes administered to increase cardiac contractility and vascular tone.
• Initial tachypnea may produce respiratory alkalosis. As the child’s condition deteriorates, metabolic acidosis may develop. Acidosis is usually well tolerated for short periods. In specific circumstances and with prolonged metabolic acidosis, sodium bicarbonate administration may be indicated.
• Take steps to prevent further fluid loss.
• If albumin is low, consider colloidal solutions.
• Diagnostics include CBC, ABGs, electrolytes, type and cross match (hemorrhagic shock), serum or plasma lactate concentration, imaging studies.
• Failure to improve after 3 boluses of isotonic fluids may be due to:
  • A greater fluid volume loss than was previously estimated
  • Ongoing fluid loss
  • Incorrect diagnosis
  • A need for blood or colloidal fluids

Distributive Shock

Septic Shock

Shock caused by infection

Goals of treatment are to restore hemodynamic stability and control infection

Administer fluids with caution in children with shock and a fever, especially if you are in a setting without a NICU/PICU

Anaphylactic Shock

• Goals of treatment are to reverse and prevent cardiopulmonary distress and control the allergic reaction.
• May need artificial airway placement and mechanical ventilation.
• Follow general guidelines for treatment of shock.
• The most important medication to treat anaphylaxis is epinephrine. It may be given IM or via auto injector. Administer a second dose if needed 10-15 minutes after the initial dose.
• Administer isotonic crystalloids.
• Albuterol may be administered via nebulizer or inhaler to relieve bronchospasm.
• Antihistamines such as Benadryl, ranitidine, and famotidine are useful.
• Corticosteroids such as methylprednisolone reduce edema.
• 25%-30% of children experience late phase symptoms several hours after the acute phase.

Neurogenic Shock

• Use general procedures for treating shock.
• Common symptoms include hypotension, hypothermia, wide pulse pressure, and bradycardia.
• Position supine or in Trendelenburg position.
• Administer a trial of isotonic crystalloid and evaluate response.
• If fluid refractory hypotension occurs, administer vasopressors such as epinephrine or norepinephrine.
• May require warming or cooling treatments, as sensitivity to ambient temperature may occur.

Cardiogenic Shock

• Main goals of treatment: Increase cardiac output, reduce metabolic needs of the body.
• Differentiate between cardiogenic and hypovolemic shock by administering 5-10mL/kg bolus of isotonic crystalloid over 10-20 minutes. If condition does not improve or worsens, treat as cardiogenic shock.
• Administer fluids cautiously. Monitor for signs of pulmonary edema and increased respiratory distress.
• Provide O₂. Prepare for mechanical ventilation and non-invasive positive pressure.
• Obtain central venous access.
• Common diagnostic tools include: ABG, Hgb, lactate concentration levels, cardiac enzymes, thyroid function tests, chest x-ray, ECG, and echocardiogram.
• If normotensive,administer diuretics and vasodilators.
• Common medications include vasodilators, inotropic agents, phosphodiesterase inhibitors, antipyretics, sedatives, and analgesics.
• Mechanical circulatory support may be needed. These tools are available only at specialized centers.
• Consult with a specialist quickly when cardiogenic shock is suspected.

Obstructive Shock

• Follow general guidelines for treatment of shock
• Signs of obstructive shock may initially resemble hypovolemic shock. Consider administering 10-20 mL/kg bolus of isotonic crystalloid fluid to ascertain type of shock
• Immediate recognition of obstructive shock is needed; as obstructive shock may rapidly progress to cardiopulmonary failure and cardiac arrest
• Primary goals of treatment of obstructive shock are to correct the underlying cause of shock and restore perfusion

Cardiac Tamponade

• Fluid administration may provide temporary improvement until pericardial drainage is obtained
• Obtain specialist assistance immediately
• Pericardiocentesis is ideally performed by specialists. It is performed with the aid of fluoroscopy and echocardiogram.
• Pericardiocentesis may be performed in an emergency if cardiac arrest is imminent or occurs.

Tension Pneumothorax

• Immediate needle decompression is needed. An 18- to 20-gauge needle is inserted over the top of the child’s third rib following the midclavicular line. Success is determined by air being expelled rapidly and clinical improvement.
• Thoracotomy and chest tube placement is required after needle decompression is performed.

Massive Pulmonary Embolism

• Support ventilation and oxygenation
• Consult specialist
• Imaging diagnostics include echocardiogram, CT scan, angiography, and ventilation-perfusion scan. CT angiography is the best tool to use. 
• Additional diagnostics include ECG, D-dimer, CBC, ABG, CXR.
• Key drugs are anticoagulants: heparin or enoxaparin if not in shock.
• If severe cardiac distress occurs; consider fibrinolytic agents such as recombinant tissue plasminogen activator (rtPA).
  

Intraosseous Access

• Rapid, safe, reliable venous access for children of all ages.
• If cardiac arrest or severe cardiovascular compromise is present, may use as initial attempt for venous access.
• Proximal tibia is the most commonly used site. Other sites include distal tibia, distal femur, and anterior-superior iliac spine. Device is now available to access humerus.
• Contraindications: Fractures and crushing injuries near the insertion site, fragile bones, previous failed attempts in same bone, infection in overlying tissues.
• Use universal precautions while obtaining access.
• After insertion, assess site for swelling or needle displacement.
• Generally used for <24 hours.
• Proximal tibial intraosseous access
  • Position leg with a slight external rotation
  • Disinfect site
  • Using a large bore (18-gauge or lower)IO or bone marrow needle, insert the needle medially below the knee, 1-3 cm (1finger width)below the flat bony prominence (may use standard hypodermic needle, but it may clog)
  • Leave the stylet in the needle
  • Use a firm surface , not your hand, to stabilize the leg
  • Insert the needle using a boring motion. You have reached the marrow space when you feel a decrease in resistance
  • Remove the stylet
  • Attach a syringe
  • Aspirate blood and bone marrow
  • Send blood to lab if available
  • Infuse small amount of saline
  • Check for swelling anteriorly and posteriorly
  • If no swelling, secure the needle with tape
  • Attach IV tubing
  • Tape tubing to skin
  • Infuse fluid via syringe or 3-way stopcock device
  • Follow procedures for administering fluids and medications using same procedures for any other venous access device
  • Use similar procedure for accessing other sites if needed