Investigations | Indication/clinical clues | Possible abnormality | Further investigation if abnormal | Possible diagnoses | Action | |||||
Dextrostix | All | Low | Blood glucose | Hypoglycaemia secondary to: | Intravenous dextrose | |||||
Blood glucose | Liver function tests | • Fasting | Fluids/insulin | |||||||
Blood ammonia | • Severe illness | |||||||||
Blood lactate | • Reye's syndrome | |||||||||
Blood and urine amino acids | • Organic aciduria | |||||||||
Urine organic acids | • Fatty acid oxidation defect | |||||||||
• Haemorrhagic shock and encephalopathy | ||||||||||
Previous polydipsia/polyuria | High | Diabetic ketoacidosis | ||||||||
Blood sodium | All | Low | Urinary sodium | Hypo/hypernatraemia +/− dehydration | Appropriate fluids | |||||
High | ||||||||||
Blood urea | All | High | Blood creatinine | Dehydration | Rehydrate | |||||
Blood film | Haemolytic-uraemic syndrome | Dialysis, plasmapheresis | ||||||||
Aspartate transaminase | All | High | Blood ammonia | Reye's syndrome | ||||||
Hypoxic-ischaemic | ||||||||||
Blood ammonia | All (unless cause known) | High | Blood orotic acid | Urea cycle defect | Sodium benzoate | |||||
Urine organic acids | Organic acidaemia | |||||||||
Full blood count and film | All | Low Hb | Hb electrophoresis | Anaemia | Transfusion | |||||
High WBC | Infection | 3rd generation cephalosporin | ||||||||
Low platelets | DIC, infection | |||||||||
Sickle cells | Sickle cell disease | |||||||||
Burr cells | Haemolytic-uraemic syndrome | Dialysis, plasmapheresis | ||||||||
Residence in endemic area | Parasites on thick/thin films | Malaria | Quinine | |||||||
Pica | Basophilic stippling | Wrist x ray—lead line | Lead encephalopathy | Chelation | ||||||
Blood culture | All | Appropriate antibiotics | ||||||||
Stool culture | All | Shigella, enteroviruses | ||||||||
Mycoplasma IgG, IgM | All (unless cause known) | Chest xray | Mycoplasma encephalitis | Erythromicin, ?prednisolone | ||||||
Viral titres | Analyse if unexplained | Repeat at discharge | ||||||||
Urine for toxin screen | Analyse if unexplained | Blood film—basophilic stipling, wristx ray—lead line | Poisoning | Antidote | ||||||
Blood lead | Analyse if unexplained | Chelation | ||||||||
CT scan without contrast | All (after resuscitation, afebrile patients should ideally be transferred for CT scan to a unit with neurosurgical facilities) | Blood | ||||||||
• Subdural | Skull x ray/skeletal survey/clotting screen | Non-accidental injury | Neurosurgical referral | |||||||
Child protection | ||||||||||
• Extradural | Neurosurgical referral | |||||||||
• Intracerebral | ||||||||||
Space occupying lesion | Tumour | Neurosurgical referral | ||||||||
Hydrocephalus | ||||||||||
• Obstructive | ?Space occupying lesion | Antituberculous cover | ||||||||
• Communicating | CSF examination | ?Meningitis, especially tuberculous | Neurosurgical referral | |||||||
Abscess | Culture aspirate | Neurosurgical referral Anaerobic cover | ||||||||
Contrast CT/MRI | ||||||||||
Swelling | Mannitol 0.25 g/kg | |||||||||
Focal low density | Cerebral abscess, herpes simplex, stroke, ADEM | |||||||||
Abnormal basal ganglia | Plasma/CSF lactate, blood gas | Leigh's syndrome, hypoxic-ischaemic, striatal necrosis | ||||||||
Lumbar puncture | In febrile if no clinical or radiological evidence of raised ICP (delay and treat if doubt) | |||||||||
• Pressure measurement | High | CT scan | Mannitol, ventilate | |||||||
• Microscopy | High WCC | Meningitis/encephalitis | 3rd generation cephalosporin, aciclovir | |||||||
• Gram, bacterial culture | High RBC | CT scan (traumatic tap should clear by 3rd bottle) | Haemorrhage/encephalitis/ non-accidental injury | Neurosurgical referral, aciclovir, child protection | ||||||
• Glucose | Low | Immediate and prolonged | ||||||||
• Protein | High | } Tuberculous meningitis | antituberculous therapy | |||||||
• PCR for viruses, TB | ||||||||||
• Prolonged search for acid fast bacilli, culture for TB on Lowenstein– Jensen | Prodrome > 7 days, optic atrophy, focal signs, abnormal movements, CSF polymorphs < 50%, hydrocephalus and/or basal enhancement on contrast CT | Tuberculous meningitis | Immediate and prolonged antituberculous therapy | |||||||
• Antibodies e.g. herpes simplex, Mycoplasma | Encephalitis | Aciclovir, erythromycin | ||||||||
• Lactate | Abnormal breathing/eye movements, basal ganglia lucencies | Muscle biopsy | Leigh's syndrome | |||||||
EEG | All, especially if ventilated or evidence of subtle seizures (nystagmus, tonic deviation of eyes, clonic jerking limbs) | Epileptiform discharges | Status epilepticus | IV benzodiazepines, phenytoin, thipentone | ||||||
Asymmetrical foci of spikes or periodic lateralising epileptiform discharges on slow background | Herpes simplex encephalitis (many patients do not have characteristic EEG) | High dose IV aciclovir for 2 weeks | ||||||||
MRI | Unexplained encephalopathy | Frontotemporal abnormality | CSF for herpes simplex PCR | Herpes simplex encephalitis | High dose IV aciclovir for 2 weeks | |||||
Thalamic abnormality | CSF for Epstein–Barr virus (arboviruses in endemic area) |