All posts by admin

SVT

Supraventricular tachycardia – where abnormal rhythm initiated above atrioventricular node, so narrow complex (with normal conduction down bundles of His). Typically rate over 220, with abrupt onset (can be inferred from history).

ECG showing SVT and effect of adenosine
SVT showing effect of adenosine

Accessory pathway that bypasses the AVN is the usual reason, esp infants, but nodal reentrants quite common in older kids. Get a 12 lead before doing anything, unless absolutely impossible.

An accessory pathway usually has a delta wave (upsloping PR). If retrograde conduction, then inverted P wave seen immediately after the QRS. If a nodal reentrant, P wave is subsumed into QRS complex.

If decompensated then synchronised cardioversion (under IM/IN ketamine).

Vagal manoeuvres do work, such as doing a valsalva manoeuvre (get child to blow through straw!), bag of icy water held to face (count to 5). Older kids can stand on their hands! Carotid sinus massage is the least effective.

But best to go straight to IV adenosine if access available. Adenosine causes sinus arrest, which feels terrifying for child. Within a few seconds, wears off and spontaneous return of rhythm, hopefully a normal one. Can also induce wheeze. Give in antecubital fossa, so as close to heart as possible.

Starting dose lower if over 1yr. Then increase by 50-100mcg/kg each time. If adenosine doesn’t work:

  • check max dose (different for neonates and older children, 12mg max)
  • check rapid bolus and flush
  • check diagnosis is correct.

Digoxin is good for babies and infants but needs 2 loading doses 6 hours apart, and you may not get a result until then. Propanolol is contraindicated in asthma. Amiodarone should be used before 3rd shock. Verapamil is contraindicated under 1 year as can cause arrest.

Prognosis

SVT usually settles down by 6-12 months but may recur around the age of 8yrs. Onset outside infancy will probably not resolve spontaneously. Prevention needs to be discussed: some families will be happy just treating episodes as they occur. Otherwise use digoxin in infancy to prevent, propanolol later.

Rare forms

Rare forms:

  • Permanent form of Junctional Reciprocating Tachycardia (PFJRT) – chronic SVT, so may go unrecognised and then cause cardiomyopathy. The accessory pathway is resistant to DC shock and adenosine. Inverted P wave seen.
  • Ectopic atrial tachycardia – due to an ectopic focus. May also be chronic. Demonstrates warm up and slow down in rate, whereas others tend to have fixed rate. First degree block seen. Resistant to DC shock and adenosine.
  • Atrial flutter usually seen only in congenital heart disease but does occur in neonates with normal hearts! In which case it tends not to recur. Ventricular rate divides neatly into 300.
  • Atrial fibrillation – needs anticoagulation before DC conversion so control rate first with digoxin while loading warfarin.

Schistosomiasis

Egg in freshwater taken up by snails.  Cercariae released into water and penetrate skin.  With this first infection, urticaria, discrete raised lesions 1-3cm and immune response (to dying larvae, rather than living!).  These then migrate into lungs, so acute schistosomiasis causing immune complex deposition, lymphadenopathy, eosinophilia, pulmonary infiltrates. 

Larvae mature in liver.  Adult worms migrate to mesenteric vessels of bowel, where eggs are laid.  Chronic blood loss from gut lesions. Hepatomegaly, splenomegaly, eventually varices if fibrotic. 

Worms can live 3-10 years.  Immunity only really develops where lots of dead worms, not necessarily high worm burden!  Eggs only start appearing 8 weeks after infection, and multiple samples required (intermittent excretion, perhaps every few days). 

Serology only really useful in travellers as persists? Praziquantel often causes abdo pain, rash, headache.  Only acts on adult worms.   

Latex allergy

The name for pure natural rubber. Found all over the place – foam (mattresses), condoms, balloons, seals, adhesives. In hospitals, BP cuffs, elastic bandages, catheters and ET tubes, pulse oximeters… Not so often in surgical gloves now. Can cause mild and severe (anaphylaxis) reactions, plus delayed (non type 1) allergy. Allergy first described in 1979, became epidemic in 1980s.

The rubber tree Hevea brasiliensis is not the same as “rubber plants” (Ficus) you get as pot plants, although you can be allergic to those too, of course.

About half of latex allergic patients also have fruit allergies, especially avocado, banana, kiwi, melon but also chestnut and tree nuts.

Certain high risk groups:

  • Spina bifida
  • Health care workers

Atopic or irritant dermatitis may also be caused by rubber chemicals rather then latex itself.

Diagnosis

  • Blood IgE test – as with other IgE tests, potential for false positives esp with grass/fruit allergy.
  • Skin prick test with standardised latex
  • Prick through suspected glove! Needs latex free environment, of course. Potential for reaction to powder, rather than latex…
  • Glove test – wet hand! Risk of anaphylaxis.

Risk of Anaphylaxis

As with other allergies, seems to vary between individuals. And previous reactions do not reliably predict future reactions.

With health care, difficult. First on surgical list. Label patient. Latex free environment, as far as possible. Reports of probable reactions from IV fluids and needle puncture of bungs in IV sets.

Need for careful occupational advice.

Fabry’s disease

Alpha-galactosidase defect, one of the lysosomal storage disorders, with accumulation in various tissues.

X-linked but females get disease, so not correct to call them carriers.

Classically, “pain attacks”, affecting the extremities. In the abdomen, can mimic appendicitis. Due to accumulation in nerves. Since nothing to really see on examination, easily misdiagnosed as functional.

Other features:

  • Renal impairment and failure.
  • Angiokeratomas – a more specific feature, but not always present, and seen in other lysosomal disorders.
  • Corneal changes
  • Cerebrovascular and cardiac problems

[Omim]

Campylobacter

Common cause of bloody diarrhoea. As with other causes of bloody diarrhea, often associated with fever and abdominal cramps.

Usually self resolving within a week. Antibiotics help if symptoms severe enough.

Excretion continues for a number of weeks, although risk of spreading infection after diarrhoea has settled of course much less, assuming decent hygiene.

Chronic excretion can occur with continuous symptoms rarely, certainly in immunosuppressed patients. Asymptomatic carriers exist, although seems to be more common in developing countries (so malnutrition probably a factor) and reinfection can also occur, of course.

About 1 in 1000 cases develop Guillain Barre syndrome after the infection. Inflammatory bowel disease seems more common after campylobacter infection?

Liver Function Tests

Bilirubin needs to be around 60 to see visible jaundice.

AST is less specific than ALT – also produced in kidney, brain etc. But perhaps changes more quickly than ALT. Most important other source of AST and ALT is muscle – so check CK too, especially if bilirubin normal. Myopathies, viral myositis, muscular dystrophy can all present with “abnormal LFTs”.

Gamma GT is also found in other tissues so not 100% specific but typically suggests cholestasis or other biliary problem (together with alkaline phosphatase).

Alkaline phosphatase also produced in bone, so look at calcium, phosphate and vitamin D as well as signs of rickets or renal disease. Most common cause of isolated high alkaline phosphatase is benign transient hyperphosphatasaemia.

Falling transaminases can be ominous in situation of bilirubin, albumin, coagulation deteriorating…

Asthma and Obesity

Obesity can mimic asthma, it affects respiratory symptoms and lung mechanics, but it can also overlap of course. Asthma is more often diagnosed in obese (misdiagnosed?). High birth weight is associated. , as is maternal obesity (and gestational weight gain) in pregnancy. Each BMI increase of 1kg/m2 increases risk by 2-3%!

Obesity is one of the factors associated with fatal asthma attacks (but note socioeconomic confounding).

Weight reduction leads to improved lung function, health status, symptoms and morbidity in adults. Not yet proven in adolescents.

Slightly increased risk of acute asthma attacks in obese adults and school age children.

Osteogenesis imperfecta

Recurrent fractures, often with minimal trauma, family history. Joint and bone pain can be an issue even without fractures.

No single test for osteogenesis imperfecta.  Clues might be deformities, short stature, hypermobility and poor dentition.

Type 1 is most mild, no deformities. Type 2 lethal in early life, antenatal scan may show chest wall abnormality and respiratory failure often at birth.

Type 3 is severe, with fractures in the womb or during birth. Short stature, deformities marked.

Type 4 variable, may only be diagnosed later in life. Type 5 associated with excessive callus formation.

Bisphosphonate infusions are used for the most severely affected. Otherwise, management revolves around:

  • Fracture and pain management
  • Aids eg wheelchairs
  • Physiotherapy, esp if immobile due to fractures

Epstein Barr virus

One of the Herpes virus family, and like other herpesviruses (herpes, varicella) becomes latent in the body after infection, in the case of EBV in B-lymphocytes. Immune system has developed specific strategies over the course of human evolution to control it – hence specific immunodeficiencies such as Duncan’s syndrome where EBV appears to be the only infection that becomes problematic (even catastrophic).

Associated with a number of tumours, including non-Hodgkin’s lymphoma, Burkitt Lymphoma (especially in Africa), nasopharyngeal carcinoma.

In most children, a mild febrile illness, with lymphadenopathy (“glandular fever” or infectious mononucleosis), sore throat (can be severe). Failure to improve with antibiotics is a clue! Peak age for severe presentations is teenagers – “kissing disease” (sexually transmitted!? Edinburgh students study found lower rates if routine barrier methods used). Prolonged incubation period of 30-50 days!

Classically rash triggered by amoxicillin (which is why amoxicillin isn’t recommended for sore throats, but rash can be seen with penicillin too) – maculopapular, sometimes petechial and/or urticarial, which is rather more suggestive.

On examination, hepatosplenomegaly can be seen.

Blood film characteristically shows atypical lymphocytosis. Monospot test (for heterophile antibodies) 70-90% sensitive so has false negatives as well as false positives so may need to proceed to PCR if important to know.

Mild hepatitis and cholestasis pretty common.

Rarer features are dacrocystitis, pneumonia, myocarditis, low platelets and neutrophils, interstitial nephritis, encephalitis. Haemophagocytic syndrome. 20x higher risk of Guillain Barre syndrome after EBV

Management

Supportive.

Splenic rupture after EBV has been reported but is very rare. Advice usually given to avoid contact sports. In ultrasound studies, peak spleen size is typically noted within the first 2 weeks of illness, but may extend to 3.5 weeks. The majority of spleen injuries occur within the first 21 days of illness and are exceedingly rare at >28 days, so one month avoidance probably sufficient.

A minority develop chronic fatigue type symptoms.

[Sports health 2014]

Anaemia

Like many things, low red cell count can be problem of production, loss or destruction.

So causes include:

  • Bone marrow failure or infiltration (leukaemia, Fanconi’s, Blackfan Diamond, erythrovirus/parvovirus)
  • Nose bleeds, gastrointestinal losses eg Meckel’s, gastritis, heavy periods
  • Haemolysis eg G6PD deficiency, hypersplenism, autoimmune
  • Iron, folate or B12 deficiency

In children, one of the most common causes is excessive milk consumption, which appears to lead to a low level colitis. Pica is often the presenting problem.

Investigations

  • Blood film – Howell Jolly bodies if hypersplenism. Leucoerythroblastic reaction (with immature red cells, as well as immature white cells) can be due to malignancy but can also be due to infection and haemolysis. Spherocytes or other abnormal forms may suggest a hereditary haemolytic condition. Sickle cells in sickle cell disease.
  • Low MCV suggests lack of iron, but may also be due to thalassaemia.
  • Reticulocyte count – indicates on going red cell production, may be high if recovering from low production
  • White cell count and platelets – if low too, suggests bone marrow failure but parvovirus can knock off all cell lines too.
  • Coagulation – deranged coagulation with low platelets suggests disseminated intravascular coagulation (DIC), usually due to sepsis, but can also reflect haemophagocytosis syndrome (due to sepsis or rheumatological disease)
  • Renal function – haemolytic uraemic syndrome (usually with diarrhoea and bloody stools, but not always)

Iron is found in red meat, pulses, green leafy vegetables, wholemeal bread, nuts, dried fruit, fortified breakfast cereals.