Pathogenesis of refeeding syndrome.

Pathogenesis of refeeding syndrome

 How does refeeding syndrome develop?

Prolonged fasting:

During prolonged fasting, hormonal and metabolic changes are aimed at preventing protein and muscle breakdown.

Muscle and other tissues decrease their use of ketone bodies and use fatty acids as the main energy source. This results in an increase in blood levels of ketone bodies, stimulating the brain to switch from glucose to ketone bodies as its main energy source.

The liver decreases its rate of gluconeogenesis, thus preserving muscle protein. During the period of prolonged starvation, several intracellular minerals become severely depleted. However, serum concentrations of these minerals (including phosphate) may remain normal. This is because these minerals are mainly in the intracellular compartment, which contracts during starvation. In addition, there is a reduction in renal excretion.

Refeeding:

During refeeding, glycaemia leads to increased insulin and decreased secretion of glucagon. Insulin stimulates glycogen, fat, and protein synthesis. This process requires minerals such as phosphate and magnesium and cofactors such as thiamine. Insulin stimulates the absorption of potassium into the cells through the sodium-potassium ATPase symporter, which also transports glucose into the cells. Magnesium and phosphate are also taken up into the cells. Water follows by osmosis. These processes result in a decrease in the serum levels of phosphate, potassium, and magnesium, all of which are already depleted.

The clinical features of the refeeding syndrome occur as a result of the functional deficits of these electrolytes and the rapid change in basal metabolic rate.

 

Patients at high risk of refeeding syndrome.

 Patients at high risk of refeeding syndrome

Patient populations at risk for refeeding syndrome include those with:

·       anorexia nervosa and other restrictive eating disorders,

·       chronic conditions causing malnutrition (cancer, congenital heart disease),

·       malabsorptive syndromes (inflammatory bowel disease, cystic fibrosis),

·       High stress patient unfed for >7 days.

·       cerebral palsy

·       bariatric surgery

·       bowel resections

·       Patients with uncontrolled diabetes mellitus (electrolyte depletion, diuresis).

·       Long term users of antacids (magnesium and aluminum salts bind phosphate)

·       Long term users of diuretics (loss of electrolytes).

Early identification of high-risk patients is crucial. The NICE guidelines provide a useful tool in this regard:

William syndrome .

William syndrome

Results from a deletion of a region of chromosome 7q11.23, containing the elastin gene.

Manifestations and picture:

·       Affected individuals often present with poor feeding and hypercalcaemia as a neonate (resolve in 2nd year).

·      Elfin facies (full cheeks, full lower lip (fish-shaped), long philtrum) sometimes a stellate iris.

·       Medial eyebrow flare, Depressed nasal bridge, Epicanthic folds

·    Cardiac: The elastin deletion causes arteriopathy, which can affect any artery, but the characteristic lesion is supravalvular aortic stenosis, peripheral Pulmonary artery stenosis.

·       Child: outgoing (cocktail party speech, Friendly manner), adult: withdrawn

·       Mild-to-moderate learning difficulties

·       Short stature

·       Hypoplastic nails

·       Skeletal: Scoliosis, kyphosis, Joint limitations

·       Renal: renal artery stenosis, Nephrocalcinosis, Pelvic kidney, Urethral stenosis

DiGeorge syndrome (velocardiofacial syndrome).

DiGeorge syndrome (velocardiofacial syndrome)

Caused by deletion of band q11 region of one copy of chromosome 22.

The deletion follows autosomal dominant inheritance.

It is helpful to test the parents as they may have a milder phenotype and not be aware of it.

However, the majority of cases are de novo.

Patients may have a long face, narrow palpebral fissures and over-folded ear helices. However, the facial phenotype is often subtle.

Affected individuals can have very variable medical complications affecting almost every system:

·       Cardiac defects (particularly tetralogy of Fallot, interrupted aortic arch, ventricular septal defect, and truncus arteriosus)

·       Palatal abnormalities including cleft palate

·       Immune deficiency (impaired T-cell production and function, thymic hypoplasia)

·       Hypocalcemia, especially in neonates (due to parathyroid dysfunction)

·       Renal tract abnormalities

·       Mild to moderate learning difficulties/ developmental delay/ Autism/ADHD.

·     There appears to be an increased incidence of psychiatric disorders, particularly within the schizophrenic spectrum.

Treatments and therapy for 22q11.2 deletion syndrome may include treatments for:

- Assessment of severity of croup using Westley Clinical Scoring System.

 Assessment of severity of croup using Westley Clinical Scoring System

A variety of scoring systems have been developed to evaluate the severity of croup.The most commonly used scoring system has been that of Westley et al.(1).

Assessment of severity of croup using Westley (2) Clinical Scoring System in emergency department, as shown in following table is very useful to plan for staying at observation unit, hospital admission, ICU admission

• Mild croup—Score 0–2; 
•  Moderate croup—Score 3–5;
•  Severe croup—Score 6–11;
•  Impending respiratory failure—Score 12–17. 

 Ibrahim Samaha

References:

1. Cherry, James D. "Croup." New England Journal of Medicine 358.4 (2008): 384-391.
2. Westley CR, Cotton EK, Brooks JG. Nebulized racemic epicontents of this manuscript. nephrine by IPPB for the treatment of croup: a double-blind study. Am J Dis Child 1978 May; 132 (5): 484-7