The child with shock: principles of management

Assessment and resuscitation of the shocked child is a complex and difficult topic even for those whose daily job it is to manage such situations. All the weirder, then, the college decision to include this specialised paediatric topic in their general adult intensive care examination process. It is unclear how detailed knowledge of this area identifies an adult intensivist as somebody deserving specialist-level accreditation. Certainly it enhances your practice, insofar as any medical knowledge does - but it is hard to argue that it forms a part of some sort of core body of essential knowledge.

Anyway, that rant is quite irrelevant. Paediatric shock is part of the curriculum. The shocked child has come up several times during the exam, in various variations:

• Question 7 from the second paper of 2016 (MOSF)
• Question 10 from the first paper of 2015 (peri-arrest infant)
• Question 4 from the first paper of 2012 (dehydration)

These questions have had no specific focus. They tend to ask you to "outline the principles of management" or "early management". Candidates may be called upon to "list, in broad terms, the key differential diagnoses" and to produce some sort of diagnostic approach. Question 4 from the first paper of 2012 was distinct in its focus on hypovolaemia; it came in the wake of the 2011 FEAST trial. There was nowhere else to put a few lines about assessment of dehydration, so it ended up in this chapter.

In terms of answering such questions, it appears from the college model answers that an A-B-C-D approach was favoured. Very generic answers seem to have been supported. In fact the college answer for Question 10 from the first paper of 2015 even includes the phrase "General ICU housekeeping". Elsewhere, the college throw away marks by casually referring to an "ABCDEFG approach", which is something they constantly reprimand the candidates for doing.  

Assessment of the shocked child

Oh's Manual presents a series of lists for the assessment and recognition of shock, which are fairly commonsense. These lists are reproduced here with a few minor modifications.

Generic to the infant/paediatric population
History Fever, feeding, urine output, diarrhoea, vomiting Irritability, lethargy Trauma Potential for ingestion  Vaccination history Unwell contacts	Examination Temperature Level of consciousness Peripheral perfusion, capillary refill Rash Skin turgor Mucous membranes Pulses Heart rate, rhythm Blood pressure Respiratory rate	Investigations CXR ECG ABG for lactate FBC and blood film BSL EUCs, LFTs Blood cultures TTE
Specific for the neonatal population:
Maternal Group B strep swab history Maternal chicken pox or herpes history Rapid breathing, sweating, tiring or cyanosis while feeding Antenatal care (any?) History of infant death in the family Cosanguineity Inborn errors of metabolism Congenital heart disease	Cardiac murmurs Abdominal distension (eg. pyloric stenosis) Differential cyanosis (PDA)	Ammonia level Urinary amino acid and organic acid screen CMV, HSV PCR Cranial ultrasound

Differential diagnosis of paediatric shock

This was asked about in Question 10 from the first paper of 2015. They gave us a two week old baby who has been well after birth, and who has progressively deteriorated. The picture was of severe metabolic acidosis. What could this be, the college asked. Differentials are necessarily broad, and can be split into age categories. A table of suitably broad differentials is offered below. It does not come from any specific source.

Differential Diagnosis of Paediatric Shock and Metabolic Acidosis

Domain	Neonate/infant age group	Children older than 12 months
Vascular	Cardiac tamponade following congenial defect repair Pulmonary embolism	Cardiac tamponade and pulmonary embolism
Infectious	Bacterial sepsis (eg. Gp B strep) Viral illness  Hypovolemia due to dehydration via diarrhoea, vomiting or failure to feed	Bacterial sepsis Viral illness  Immune compromise due to lymphoma or leukaemia Hypovolemia due to dehydration via diarrhoea, vomiting or decreased oral intae
Neoplastic
Drug-induced	Accidental overdose through maternal excretion into milk	Accidental overdose
Congenital	Heart defect, especially duct-dependent disease	Complications of previously stable heart defect (eg. "Eisenmongerisation" of the right heart)
Autoimmune	Anaphylaxis	Anaphylaxis
Trauma	Haemorrhage Neurogenic (eg. cord section) Tension pneumothorax	Haemorrhage Neurogenic (eg. cord section)
Endocrine or metabolic	Metabolic pathway defect	Hypothyroidism Hypoadrenalism Severe ketoacidosis Metabolic pathway defect

Assessment of hypovolaemia

Question 4 from the first paper of 2012 gave us a dehydrated child, and asked us exactly how dehydrated they were.. LITFL follows the college answer verbatim. Here it is, interpreted as a table:

Mild (5-6% loss of body weight)	Moderate (7-10% loss of body weight)	Severe (over 10% loss of body weight)
2 or more of: Restlessness or irritability. Sunken eyes (also ask the parent). Thirsty and drinks eagerly. Poor skin turgor; after pinch test the skin fold is visible for less than 2 seconds.		2 or more of: Abnormally sleepy or lethargic. Sunken eyes. Drinking poorly or not at all. Very poor skin turgor; after pinch test the skin fold is visible for longer than 2 seconds. Weak rapid pulse Cool or blue extremities Hypotension Rapid breathing Sunken anterior fontanelle.

That whole "two or more" thing comes from Gorelick (1997). "A subset of four factors—capillary refill >2 seconds, absent tears, dry mucous membranes, and ill general appearance—predicted dehydration as well as the entire set, with the presence of any two or more of these signs indicating a deficit of at least 5%".  In general, when it comes to assessing dehydration, Gorelick et al recommend using a combination of three signs (this is also mentioned in the college answer) - a combination of three signs had a sensitivity of 87% and specificity of 82% for detecting a water deficit of 5% or more.

This is not the only possible dehydration assessment scale. The following table is slightly modified from Vega and Avner, by way of Steiner et al (2004). It is a list of clinical features which stratifies dehydration in young infants.

Mild (5-6% loss of body weight) Thirst Restlessness

Moderate (7-10% loss of body weight) Drowsyness Postural hypotension Tachycardia Decreased pulse amplitude Tachypnoea Sunken anterior fontanelle Sunken eyes Absent tears Dry mucous membranes

Severe (over 10% loss of body weight) Cold, cyanotic extremities Not eating or drinking Drowsy and limp Rapid thready pulse Hypotension*

The Royal Children's Hospital give another, slightly different one:

Mild (less than 4% loss of body weight) no clinical features

Moderate (4-6% loss of body weight)  Delayed CRT  (Central Capillary Refill Time) > 2 secs Increased respiratory rate Mild decreased tissue turgor

Severe (over 7% loss of body weight) Very delayed CRT > 3 secs, mottled skin Other signs of shock (tachycardia, irritable or reduced conscious level, hypotension) Deep, acidotic breathing Decreased tissue turgor

Note the lack of "restlessness" and "also ask the parent". The pragmatic physicians from the RCH acknowledge the unreliability of subjective findings. At risk of inundating the candidate with more similar-looking dehydration assessment scales, one may merely refer to the popular Friedman (2004) which extends the pursuit of objective measurements further, extending the scale with urine output measurements, urinary specific gravity, specific heart rate ranges, and so forth. 

Management of the shocked child

This is an approach which supports undifferentiated shock presentations as described in the college answers. There needs to be a way for the candidate to appear confident and safe in managing generic issues while giving the appearance that they know exotic NICU interventions in significant detail. In other words,  "assess the airway and the need for intubation" needs to appear in there somewhere, but apart from such sophomoric crap you also need to mention how you'll put that infant on an alprostadil infusion to keep their ductus arteriosus patent while you wait for their duct-dependent congenital defect to be repaired.

Working on the premise that all readers seriously preparing for this exam are going to "assess the airway and the need for intubation", here is a succinct list of important neonatal and paediatric caveats which need to be mentioned as a part of the answer:

• Fluid resuscitation is still a part of well-accepted protocols, whereas fluid-restrictive strategies a'la FEAST are still controversial. O'hs Manual, in the "septic shock" section of Chapter 103 reports that septic children may require as much as 100ml/kg of fluid resuscitation.
• Remember normoglycaemia. According to the examiner's comments, "failure to immediately treat the hypoglycaemia was a fatal error" in Question 7 from the second paper of 2016. It is unclear as to the relevance of this in normoglycaemic shocked children, but each paediatric scenario thus far has involved hypoglycaemia.
• Lumbar puncture is for some reason contraindicated: "do not do a lumbar puncture in a shocked child", says Oh's Manual
• Maintenance fluid rate is calculated as follows:
  • - First 10kg: 4ml/kg/hr
    - Second 10kg: 2ml/kg/hr
    - All other kgs: 1ml/kg/hr
    Most of the online calculator apps reference this 1957 paper by Holliday and Segar. A good modern revision was performed by Meyers (2009). 
•  2/3 of the maintenance rate is usually given  to critically ill children because of their propensity to secrete ADH, thereby causing water retention.
• Isotonic fluids should be used for maintenance: Wang et al (2013) suggest that they are safer than hypotonic fluids. This contrasts slightly with the college answer. NICE guidelines (Neilson et al, 2015) also recommend isotonic crystalloid for maintenance, and make no mention of the dextrose cocktail which the college recommend ("add 100 ml of 50% dextrose to 900 ml 0.9% NaCl"). The RCH guidelines from Melbourne recommend the routine use of Plasmalyte 148 together with 5% dextrose, without offering any references.
• Replacement of volume in dehydration:
  Formula: Vol = % Dehydration x body weight x 10 (in mls). 
  The volume resuscitation formula given here is found in Question 7 from the second paper of 2016. NICE guidelines (Neilson et al, 2015) recommend isotonic crystalloid like 0.9% NaCl.
• Broselow tape: this needs to be mentioned as the source of all your paediatric drug doses, tube sizes and other calculations you'd rather outsource to an "analog app". 
• Social issues:  it looks good if you remember to keep the family in the loop. It makes you look like less of a sociopath.
• Transfer and retrieval: so far all the college questions have included something along the lines of "call for help" or 'organise retrieval" in the model answer. This demonstrates that the college want you to acknowledge the limitations of your training. The best place to care for a critically ill child is a large children's hospital with lots of experienced staff. An important plan of your plan of management will be sending your patient to such a place.

Management of the shocked child as a series of stage directions

The answer to a  "describe your approach" question can use a familar A-B-C-D template. This approach was taken by the college in their model answer to Question 7 from the second paper of 2016. 

1. Assess the need for intubation.
   - At this stage, senior assistance from somebody expert in paediatric critical care is required, as the intubation may be difficult.
2. Administer 100% oxygen.
3. Establish venous access.
   - Give a 20ml/kg bolus, FEAST be damned.
   - Inotropes and vasopressors if no longer fluid-responsive
   - Parameters guiding resuscitation (eg. lactate, haemodynamic variables, urine output) differ little from adult standards
4. Sedation and analgesia to support tolerance of invasive therapies
   (also decreases demands on the cardiac output)
5. Electrolyte correction
6. Maintenance fluid:  As per college answer, "add 100 ml of 50% dextrose to 900 ml 0.9% NaCl and infuse this at 2/3 maintenance rate (16 ml/hr in this case) (accept 24 ml/hr for 1^st 48 hours)". On close inspection, this concoction resembles the premixed "four percent and fifth" bags.
   - A urinary catheter will also be required.
7. No protein in diet until metabolic screen is cleared
   - Maintain normoglycaemia with infusion of 10% dextrose of dextrose-rich maintenance fluid
8. Blood transfusion may not be warranted
9. Empiric antibiotics if sepsis is suspected, within 1 hour.
   - Cultures of blood and urine.
   - Consider antivirals if there is suspicion of viral meningitis or encephalitis