Last Updated on September 18, 2022
“Dengue is a bread and butter. Every doctor must know dengue from front till the end”
Introduction
• Dengue must be identified and risk-stratified early
• Dengue is a notifiable disease
Pathogen
• Dengue virus (single-stranded RNA virus, from Flavivirus genus)
• Intrinsic incubation: 4 – 7 days, up to 14 days (viraemic period, may be asymptomatic)
Warning signs of dengue
Warning signs suggest high possibility of complications in dengue infection / rapid progression into severe dengue
- (unprovoked) Mucosal bleeding
- Persistent vomiting (≥3 times over 24 hours)
- Abdominal pain / tenderness
- Tender liver
- Persistent diarrhoea (≥3 times over 24 hours)
- Lethargy / confusion / restlessness
- Laboratory: ↑HCT with rapid ↓Platelet count
Diagnosis of dengue
(A) Probable dengue
- Live in dengue area
- Fever with ≥2 other clinical findings
(B) Laboratory-confirmed dengue
e.g. Dengue rapid combo test / Dengue serology
Classification of dengue
- Dengue ± warning signs
- Severe dengue
Pathophysiology
• Dengue virus impairs endothelial cell adhesion and tight junction → vascular hyperpermeability → leakage of plasma into extravascular compartment (i.e. 3rd space loss) → haemoconcentration, hypovolaemic shock
• Abnormal haemostasis (thrombocytopenia / coagulopathy)
• Stimulation of cytokines and other inflammatory mediators →
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Further reading
1. https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1008603
Phases in dengue
Febrile phase
- High grade fever lasting 2 – 7 days + facial flushing, rash, generalised body ache, vomiting, headache, sore throat, eye redness
- Mild haemorrhagic manifestation e.g. petechiae / mucosal membrane bleeding
- May have liver tenderness
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Change in blood parameters
- Earliest FBC change: progressive decreasing WCC and low platelet count
Critical phase
- Onset: Often occurs after 3rd day of fever OR indicated by rapid drop in temperature
- Duration: 24 – 48 hours
- In severe dengue infection, patient may deteriorate
- Most patients recover spontaneously or require short period of fluid and electrolyte therapy; but some patients may develop compensated / decompensated shock due to plasma leakage
- Organ dysfunction usually but not exclusively occurring in this phase
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Changes in blood parameters that are usually observed:
- FBC: haemoconcentration, thrombocytopenia, leucopenia with relative lymphocytosis
- LFT: elevation of transaminases (typically AST > ALT), hypoproteinaemia, hypoalbuminaemia
Recovery phase
- Onset: after 24 – 48 hours of critical phase
- Plasma leakage stops, followed by reabsorption of extravascular fluid → haemodilution
- Patient’s general wellbeing improves — appetite returns, GI symptoms improve, diuresis ensues
- Haemodynamics stabilise
- May have classical rash — ‘isles of white in the sea of red’
- In some condition, organ dysfunctions may worsen
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Changes in blood parameters that are usually observed:
- FBC: Haematocrit stabilises, then drops further due to haemodilution; WCC recovery followed by platelet count recovery
Plasma leakage
Plasma leakage → hypovolaemia → reflex tachycardia & generalized vasoconstriction
Manifestations of vasoconstriction
Differential Diagnoses
• Malaria
• Leptospirosis
• Typhoid fever
• COVID 19
Physical Examination
Haemodynamics
Brain, cardiovascular, lungs, kidney, skin
Normal Circulation | Compensated Shock | Decompensated / Hypotensive Shock | |
Consciousness level | Clear & alert | Clear (may be missed if you do not touch patient) | Change of mental state - restless / drowsy |
Temperature of extremities | Warm & pink | Cold | Cold clammy extremities |
Capillary refill time (CRT) | Brisk (<2 seconds) | Prolonged (>2 seconds) | Mottled skin, very prolonged CRT |
Peripheral pulse volume | Good volume | Weak & thready pulses | Feeble / Absent |
Heart rate | Normal | Tachycardia | Severe tachycardia // bradycardia in late shock |
Blood pressure | Normal | - Normal SBP with rising DBP - Postural hypotension | Hypotension / Unrecordable BP |
Pulse pressure | Normal | Narrowing pulse pressure | Narrowed (≤20 mmHg) / Unrecordable |
Respiratory rate | Normal | Tachypnoea | Metabolic acidosis / Hypernoea |
Urine output | Normal | Reducing trend | Oliguria / Anuria |
Investigations
Full blood count (FBC)
- Progressive decrease in WCC followed by platelet reduction is suspicious of dengue
White cell count
• Leucopenia with relative lymphocytosis can be usually observed during critical phase
• Leucocytosis + dengue shock may suggest plasma leakage / bleeding, rather than secondary bacterial infection
Haematocrit
Median normal values:
• Female — 40%
• Male — >60 years old = 42%; ≤60 years old = 46%
Notes:
• Correlates well with plasma volume loss & severity
• Confounding factors: haemorrhage, excessive fluid replacement, haemodilutional state
Management
Does this patient require fluid?
Algorithm A — Fluid management in compensated shock
Algorithm B — Fluid management in decompensated shock
Algorithm C — Fluid management in decompensated shock (with presence of bleeding & leaking or other causes of shock)
Common Q&A
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Take Home Message
1. Remember to analyse the severity and anticipate the complications of dengue fever
2. CCTVR: shock can be missed if you do not touch the patient