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Shock

• Aetiology
• Blood Pressure
• Management of Shock
• Management of Secondary Complications

Shock is a complex syndrome of circulatory dysfunction associated with reduced oxygen and nutrient delivery to peripheral and ultimately to central organs. The aetiology is multifactorial and the syndrome is frequently complicated by secondary involvement of many organ systems.

The major secondary complication of severe shock, virtually universal in fatal shock, is a syndrome characterised as Systemic Inflammatory Response Syndrome (SIRS).

The key features of SIRS are

• circulatory failure
• endothelial dysfunction
• organ failure
• coagulation disturbances

These secondary phenomena are responsible for much of the mortality and morbidity and early recognition and aggressive management are essentials of successful management.

Aetiology

Likely clinical contexts

• feto-maternal haemorrhage
• vasa praevia
• cord accidents/acute bleeding
• perinatal asphyxia
• ELBW infant
• chorioamnionitis
• severe sepsis
• high fluid losses
• assisted ventilation (iatrogenic problems)

Clinical features of shock

• hypotension
• peripheral vasoconstriction
• tachycardia (sometimes only bradycardia in ELBW)
• tachypnoea
• hypoxia
• metabolic acidosis
• CNS disturbance (lethargy, irritability)
• oliguria

Blood Pressure

It is difficult to state meaningfully what a satisfactory blood pressure is in the context of the seriously ill infants for whom this is relevant in treatment. 'Normal' values may not necessarily be helpful in defining a level of blood pressure below which the infant is compromised. Careful clinical judgement is important.

The levels below are based on the best available evidence, but are probably higher than the level at which the infant is compromised. It is important to avoid over treatment and the lower end of these ranges should be used to guide treatment decisions.

The basic goal should be an infant with good clinical perfusion and pulses, normal neurological behaviour, urine output of >0.5ml/kg/hr and no metabolic acidosis or lactate accumulation.

'Normal' Ranges

See Blood Pressure tables

Management of Shock

Prevention, early diagnosis and aggressive management are the cornerstones of care. Once the secondary complications of shock (SIRS etc.) are established it is very difficult to reverse shock. The key goal is the establishment of adequate tissue perfusion and oxygenation.

Early consultation with NETS/ Level 3 centre is important once shock is diagnosed.

• Establish airway, breathing, circulation

• sick, clinically shocked neonates should be intubated and ventilated before they meet conventional ventilation criteria if this can be achieved safely (consider experience of operator).
  Intubation may precipitate decompensation in the critically ill child.
• perform once circulation stabilised, especially if using induction agents.
• if using vasodilating agents (e.g. opiates), volume load first
  

• Stop any bleeding
  
  
• Monitor oxygen saturations. Administer oxygen as needed
  
  
• Establish reliable intravenous access
  
  
  • Peripheral IV - do not waste time on peripheral IV if proving difficult
    
    
  • If peripheral access is difficult to achieve
    
    • Umbilical Venous catheter (5F for preterm, 5 - 8 F for term or 5 - 8F sterile feeding tube)
    • Intraosseous
      
      
• Consider and treat cause (including iatrogenic problems)
  • screen for sepsis
    
    
  • cover with broad spectrum antibiotics
    

• consider Herpes and need for acyclovir
• consider use of Immunoglobulin (Intragam) in established sepsis
  

• pneumothorax
• pericardial tamponade
• occult bleeding

• Ensure adequate volume replacement

There is no evidence that colloid has any advantage over saline in initial resuscitation

If blood loss, use blood early. Initially packed cells

• urgently Cross matched if available in time
• O Negative. Low titre. Uncrosssmatched
• placental blood (Heparinised syringe. Sterilise placental surface vein with alcohol. Use clot filter)

Once initially stabilised consider need for other blood products

• Fresh Frozen Plasma
• platelets

These should be given on the basis of active bleeding or significant abnormality on investigation.

• Consider treatment of acidosis

Primary goal is establishment of stable circulation, perfusion and ventilation

Once these are addressed and CO₂ is normal, if metabolic acidosis is present, correct acidosis using Sodium Bicarbonate (dose (mmol) = BE *wt/4)

• Inotropes

• If response poor

• check diagnosis
• transilluminate chest
• establish that ventilation and airway remain intact
• consider adequacy of volume replacement

Consider Adrenaline infusion (0.05 - 1.0 microgram/kg/min)

• consider use of steroids
• especially in ELBW infants
• dose: Hydrocortisone 3mg/kg 6 hourly

• noradrenaline should only be used in an ICU setting
  
  
• a poor response to inotrope therapy can be due to an acquired catecholamine resistance. This is most commonly a problem in overwhelming sepsis or in the chronically hypoxically stressed or failing myocardium.

Dopamine and Dobutamine will not work well in this situation. Early use of Adrenaline is advisable and urgent discussion with a Level 3 Consultant should be undertaken.

Management of Secondary Complications

• Respiratory

Early stabilisation of airway breathing and circulation has been dealt with above

Ongoing ventilatory problems are commonly a feature of the sicker infant. Pulmonary oedema, hyaline membrane disease, ARDS and pneumonia may all be associated and need to be considered and treated in their own right.

The combination of poor myocardial and circulatory performance with endothelial dysfunction commonly complicates respiratory management. End pressures used in ventilation should probably be higher because of this (6-8 cm) and careful attention needs to be paid to circulation.

The early ventilatory stabilisation of a critically ill patient may be associated with some understandable over-aggression, with the attendant risk of complications. It is important to reassess treatment quickly once stable to ensure that treatment is adequate but not excessive. Excessively low carbon dioxide levels are particularly to be avoided because of concerns about CNS injury (especially in conjunction with sepsis).

Ventilatory stabilisation should be undertaken on the advice of the NETS consultant. These guidelines are given as a starting point

Goals:	pH	7.2 - 7.35
	CO2	40 - 55
	O2	50-70
	Base Deficit	better than negative 8.00
	Saturations	85-95%

• Renal

Renal impairment is a significant component of most shock syndromes in the neonate.

Oliguria is the rule and may be associated with acute tubular necrosis or acute cortical necrosis. Complications include hyperkalaemia and fluid overload.

If urine output is below 0.5 ml/kg/hr manage by

• volume loading 10ml/kg
• frusemide 2mg/kg
• low dose dopamine at 2-5 microgram/kg/min

The ELBW infant with renal impairment is particularly prone to hyperkalaemia, which may cause cardiac death. The hyperkalaemia may be the presenting feature of the renal impairment and may commence in the first 2-3 days of life. High risk infants should have potassium levels 

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