6.4 PALS Dysrhythmia & Shock Management

6.4 PALS Dysrhythmia & Shock Management

Pediatric Tachycardia: Sinus Tachycardia vs. SVT

Tachycardia with pulses is divided clinically into narrow-complex ($QRS < 0.09\text{ seconds}$) and wide-complex ($QRS \ge 0.09\text{ seconds}$) rhythms. A common diagnostic challenge is differentiating sinus tachycardia (ST) from supraventricular tachycardia (SVT). Rate thresholds are clues, not diagnostic boundaries; onset, variability, P waves, QRS width, age, symptoms, and response to treatment matter.

Table 6.4.1: Sinus Tachycardia vs. Supraventricular Tachycardia (SVT) in Pediatrics

SVT Management Algorithm

[Supraventricular Tachycardia Confirmed]
                    │
        Is the child hemodynamically STABLE?
       (Normal BP, alert mental status, good perfusion)
         /                                    \
       YES                                     NO (Hypotensive, altered, shock)
       │                                       │
[1. Vagal Maneuvers]                 [Immediate Synchronized Cardioversion]
   • Infant: Ice to upper face          • Initial dose: 0.5 to 1.0 J/kg
   • Child: Blow into syringe           • Subsequent dose: 2.0 J/kg
       │                                (Sedate if possible; do not delay)
[2. Adenosine Rapid IV Push]
   • 1st Dose: 0.1 mg/kg (max 6 mg)
   • 2nd Dose: 0.2 mg/kg (max 12 mg)
   • Follow immediately with 5-10 mL flush

• Vagal Maneuver Techniques:
  • Infants and Toddlers: Apply a crushed ice and water slurry inside a sealed plastic bag over the upper half of the face (forehead and bridge of nose) for 15 to 20 seconds, stimulating the diving reflex. Never occlude the mouth or nose.
  • Older Children: Have the child blow forcibly into a 10 mL syringe for 15 seconds to move the plunger, or bear down (Valsalva).
  • Contraindication: Never apply ocular globe pressure or bilateral carotid massage in pediatric patients due to risk of retinal detachment or cerebrovascular ischemia.
• Adenosine Administration:
  • Extremely short half-life ($<10\text{ seconds}$). Must be administered via a rapid IV push through an antecubital or central line using a two-syringe stopcock technique, followed instantly by a 5 to 10 mL normal saline flush.
• Synchronized Cardioversion:
  • Mandatory for unstable SVT (hypotension, poor perfusion, altered mental status).
  • Initial dose: 0.5 to 1.0 J/kg synchronized to the R wave.
  • If unsuccessful, escalate to 2.0 J/kg synchronized. Ensure the synchronizer flag tracks every R wave to avoid firing during the vulnerable repolarization period (R-on-T phenomenon triggering VF).

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Pediatric Shock Syndromes & Fluid Resuscitation Protocols

Shock is defined as an acute state of circulatory dysfunction resulting in failure to deliver adequate oxygen and nutrients to meet cellular metabolic demands.

Shock Classifications

1. Hypovolemic Shock (Most Common): Absolute intravascular volume depletion (severe dehydration, gastroenteritis, diabetic ketoacidosis, hemorrhage). Exam findings: Tachycardia, sunken fontanelle, dry mucous membranes, prolonged capillary refill, weak peripheral pulses, cool pale skin. Systemic vascular resistance (SVR) is elevated.
2. Distributive Shock (Septic, Anaphylactic, Neurogenic): Maldistribution of blood flow due to severe vasodilation and increased endothelial capillary permeability.
   • "Warm Shock" (Early hyperdynamic septic shock): Bounding peripheral pulses, flash capillary refill ($<1\text{ second}$), warm flushed skin, widened pulse pressure.
   • "Cold Shock" (Late hypodynamic septic shock): Peripheral vasoconstriction, high SVR, narrow pulse pressure, cool mottled extremities, delayed capillary refill.
3. Cardiogenic Shock: Intrinsic pump failure (myocarditis, congenital heart disease, severe arrhythmias, myocardial contusion). Exam findings: Tachycardia, gallop rhythm (S3/S4), elevated jugular venous pressure, hepatomegaly, pulmonary crackles/rales, cardiomegaly on chest radiography. SVR is high, cardiac index is low.
4. Obstructive Shock: Physical mechanical obstruction to cardiac inflow or outflow (tension pneumothorax, massive pulmonary embolism, cardiac tamponade, critical coarctation of the aorta / interrupted aortic arch in neonates). Exam findings: Pulsus paradoxus, distant heart sounds, tracheal deviation, absent unilateral breath sounds.

Fluid Resuscitation Guidelines

• Hypovolemic & Septic Shock:
  • Administer 10 to 20 mL/kg isotonic crystalloid (0.9% Normal Saline or Lactated Ringer's) as a rapid IV/IO bolus over 5 to 20 minutes.
  • Reassess the patient immediately after the bolus: evaluate heart rate, blood pressure, mental status, pulse quality, and capillary refill.
  • Look specifically for signs of fluid overload (hepatomegaly, new pulmonary rales, worsening tachypnea).
  • Repeat only while perfusion improves and overload remains absent; cumulative volume, timing, and transition to epinephrine or norepinephrine depend on response and the shock pathway.
• Cardiogenic Shock / Suspected Myocarditis:
  • Obtain early expert input. Give fluid only when a preload deficit is likely, in cautious aliquots with immediate reassessment; there is no universal 5-10 mL/kg prescription for every cardiogenic presentation.
  • Stop the infusion immediately if pulmonary crackles, worsening work of breathing, or liver enlargement develop. Initiate early inotropic/vasoactive support (epinephrine, milrinone, dopamine).
• Hemorrhagic Shock:
  • If blood loss is suspected and hypotension persists after 20 to 40 mL/kg of crystalloid, transfuse 10 mL/kg of Packed Red Blood Cells (PRBCs).

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Worked Pediatric Resuscitation Calculations

Case 1: Defibrillation & Cardioversion for a 16 kg Child

• Defibrillation for VF/pVT (Initial Dose: 2 J/kg): $\text{Energy} = 16\text{ kg} \times 2\text{ J/kg} = \mathbf{32\text{ Joules (unsynchronized)}}$
• Second Defibrillation Shock (4 J/kg): $\text{Energy} = 16\text{ kg} \times 4\text{ J/kg} = \mathbf{64\text{ Joules (unsynchronized)}}$
• Synchronized Cardioversion for Unstable SVT (Initial Dose: 0.5 to 1.0 J/kg): $\text{Energy} = 16\text{ kg} \times 1.0\text{ J/kg} = \mathbf{16\text{ Joules (synchronized)}}$

Case 2: Fluid Resuscitation for a 12 kg Child in Septic Shock

• Initial 20 mL/kg Crystalloid Bolus: $\text{Fluid Volume} = 12\text{ kg} \times 20\text{ mL/kg} = \mathbf{240\text{ mL of 0.9\% Normal Saline}}$
• Administration: Deliver 240 mL via rapid push-pull syringe or pressure bag over 5 to 10 minutes.

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NPS Exam Traps Callout Box: PALS & Shock

[!WARNING] NPS Exam Trap 1: The Pediatric Bradycardia Protocol In adult ACLS, CPR is not initiated for bradycardia if a pulse is present. In pediatric PALS, this is WRONG! If a child has a heart rate $<60\text{ bpm}$ with signs of hypoperfusion despite oxygenation and ventilation, you MUST start chest compressions immediately. Do not waste time giving atropine or waiting for complete asystole.

NPS Exam Trap 2: Fluid Resuscitation in Cardiogenic Shock Tachycardia, hepatomegaly, pulmonary findings, and poor perfusion raise concern for cardiogenic shock. Avoid reflexive repeated 20 mL/kg boluses; obtain expert consultation, assess preload and lung congestion, and use physiology-directed vasoactive support. If fluid is indicated, give a cautious aliquot and reassess immediately.

NPS Exam Trap 3: Adenosine Administration Technique Adenosine has an ultra-short half-life and rapid cellular uptake. Give it as a rapid IV/IO push through the closest suitable access and follow immediately with a flush. Slow administration may deliver too little active drug to the heart to terminate an AV-node-dependent rhythm.

NPS Exam Trap 4: Defibrillation vs. Synchronized Cardioversion Never select synchronized cardioversion for ventricular fibrillation or pulseless VT! The monitor cannot synchronize because there are no organized QRS complexes, causing the machine to withhold the shock indefinitely. Defibrillation for VF/pVT is always UNSYNCHRONIZED.