Source

1. Cloherty and Stark's manual of neonatal care

#definition

one or more of the following of

• Poor central or peripheral pulses
• tachycardia
• mottled appearance
• pale color
• prolonged CRT (>3 sec)
• core-periphery difference of 3^o C
• low blood pressure

Additional features includes (to strengthen the diagnosis)

• urine output <0.5 ml/kg/hour in the last 6 hours
• serum lactate >5 mmol/L
• low PH (<7.25)
• base deficit of >-5mEq/L

Hypotension in neonates

• Mean blood pressure less than 5th percentile for the postnatal age in days
• British Association of perinatal medicine - working Definition MBP less than gestational age or <30 mm Hg whichever is higher
• MPB of 20 mm Hg isacceptable if CrCP (Cerebral critical closing pressure) is maintained - undermines the importance of organ perfusion rather than blood pressure alone
• Bedside capnography can be a surrogate marker for organ perfusion

Classification of neonatal shock

4 types irrespective of the etiology

Assessment of circulation

clinical signs

• pulses - especially femoral and brachial pulses
• heart rate - tachycardia denotes early phase of shock
• capillary refill time - unreliable in hypothermia, rapid CRT may denote septic shock
• cold peripheries - core-peripheral difference of 3^o C
• SpO₂ - pre-post ductal difference of 3%

Blood pressure

• Systolic BP - myocardial contractility
• Diastolic BP - basal vascular tone, low blood volume
• cuff width to arm ratio should be between 0.45 - 0.55
• invasive BP(iBP) can be considered in extremely low birth weight babies as oscillometric method can overestimate BP if MBP is less than 25 mm Hg
• in iBP, dampening of waveform can happen which can be due to introduction of air bubbles or use of small depth catheters
• it can under-read systolic and over-read diastolic pressures

Echo

• various parameters of echo helps in the assessment of shock

other methods of assessment

• chest x ray -helpful to diagnose cardiomegaly, pulmonary oligemia or plethora, pleural effusion, pneumothorax
• ECG - to diagnose myocardial injury and structural heart diseases
• Perfusion index (PI) - ratio of pulsatile and non-pulsatile blood flow
• plethysmograph variability index - derived from PI reflecting its dynamic change during one respiratory cycle
• Electrical bio-impedance and bio-reactance - continuous cardiac output measurement by measuring electrical impendence over thorax
• cerebral and somatic oxygenation ( near infra-red spectrometry)

Causes of shock

sepsis
perinatal asphyxia
left to right shunt

sepsis and shock

• vasodilation and vasoparesis leading to capillary vascular leak
• initially can be compensated with increased heart rate
• LV contractility deteriorate quickly with increase in SVR, leading to compromised blood flow, MODS and death

features of septic shock

• low DBP and hyperdynamic left ventricle in early stages
• low SBP in late stages
• state of relative adrenaline insufficiency (RAI)
  • < 5 μg/dL of plasma cortisol is suggestive of adrenocortical insufficiency
  • <15 μg/dL in a stressed neonate is suggestive of RAI

Diagnosis of shock

• confirmed sepsis - blood culture or sepsis screen positive
• Probable sepsis - blood culture and sepsis screen negative, but strongly suggestive of sepsis like sclerema or refractive metabolic acidosis

Perinatal asphyxia

• shock in initial 48 hours due to myocardial ischemia
• reduced stroke volume and low SBP,
• mimics
  • cardiogenic shock - arrhythmias, cardiomyopathy
  • pneumothorax, pleural effusion

Management of shock

Management of early signs of shock

• TABC - Temperature, airway, breathing and circulation
• administer antibiotics in the 1st hour if sepsis is suspected
• initial administration of 10 ml/kg of 0.9% saline over 30-60 mins
• permissive hypotension not advised
• withhold enteral feeds in acute phase of shock for the risk of redistribution of mesenteric circulation and gut ischemia
• monitor blood sugar, ionized calcium and electrolytes
• intubate if needed

Volume expansion

• 10 ml/kg of NS initially
• upto 20-30 ml/kg in cases of proven blood loss and distributive shock
• caution should be used to give fluid in PDA associated shock, post-asphyxia cardiogenic shock and shock during transitional circulation and POCE (point of care Echo) should always be used as a guide
• choice of agents
  • crystalliods
  • NS >>> RL
• Infants operate at the higher end of frank-starling curve, so they may not have enough left ventricular reserve for volume expansive. volume expansion helps cardiac output but not blood pressure
• start initially with one bolus, plan expansion with the help of POCE and BP

Choice of drugs

• should be decided based on POCE/ BP

• adrenal insufficiency - use hydrocortisone
• pulmonary artery hypertension - pulmonary vasodilator
• refractory to two inotropes - consider hydrocortisone
• rule out pneumothorax, cardiac tamponade, pleural collections
• use of two separate lines to provide maintenance fluids and inotropes is preferred
• avoid using inotropes with vasculocorrosive drugs like calcium gluconate
  

End-points of shock and weaning