01Approach to the Critical Patient/attcp77

Immediate priorities

›Shock recognition and resuscitation

›Compensated dengue shock

›Narrowing pulse pressure <=20 mmHg with tachycardia

›Cold extremities with delayed capillary refill >2 seconds

›Rising hematocrit concurrent with platelet fall

›Decompensated dengue shock

›SBP <90 mmHg

›MAP <65 mmHg

›Altered mental status

›If shock present, initiate isotonic crystalloid bolus 10 ml/kg over 15 to 30 minutes

›Reassess after each bolus for response

›Titrate to resolution of shock signs

›Severe hemorrhage recognition

›Hematemesis or melena

›Gastric content aspiration risk

›Active GI bleeding protocol

›Clinically significant mucosal bleeding

›Hemostatic support planning

›Avoid prophylactic platelet transfusion

›If severe bleeding with hemodynamic instability, pRBC transfusion

›Target Hgb stabilization not arbitrary threshold

›Whole blood alternative in resource-limited settings

›Severe organ impairment recognition

›Hepatic failure threshold

›AST or ALT >=1000 IU/L

›Coagulopathy screening

›Dengue encephalitis

02History/hx58

Presentation pattern

›Febrile phase (days 1 to 3)

›Abrupt high-grade fever >=38.5 C

›Incubation period 5 to 7 days (range 3 to 10 days)

›Fever duration 2 to 7 days; may be biphasic

›Cardinal symptom complex

›Severe headache

›Retro-orbital pain

›Bone, joint, and muscle pain (breakbone fever)

›Early rash

›Transient facial erythema in first 24 to 48 hours

›Maculopapular or morbilliform eruption days 3 to 6

›Critical phase warning signs (days 4 to 6, around defervescence)

›Severe abdominal pain or tenderness

›Persistent vomiting unable to tolerate oral fluids

›Clinical fluid accumulation symptoms

›Dyspnea from pleural effusion

›Abdominal distension from ascites

›Mucosal bleeding

›Gum bleeding, epistaxis

›Hematemesis or melena

›Lethargy or restlessness

›Postural dizziness or syncope

Epidemiologic context

›Travel and exposure history

›Travel to dengue endemic region

›Asia, Latin America, Caribbean, Africa, Pacific Islands

›Dengue excluded if symptoms begin >2 weeks after leaving endemic area

03Physical Exam/exam67

Vitals and general appearance

›Vital sign interpretation

›Temperature

›High-grade fever >=38.5 C typical in febrile phase

›Defervescence marks transition to critical phase

›Heart rate

›Tachycardia as shock surrogate

›Relative bradycardia in uncomplicated dengue occasionally seen

›Blood pressure

›Pulse pressure <=20 mmHg = decompensated shock marker

›Rising diastolic with narrowing pulse pressure = earliest shock sign

›Respiratory rate

›Tachypnea from pleural effusion or metabolic acidosis

›Dyspnea disproportionate to fever suggests fluid accumulation

›General appearance

›Flushed facies in early febrile phase

›Toxic appearance in severe dengue

›Restlessness or lethargy as shock proxy

Skin and mucosal exam

›Rash assessment

›Maculopapular rash with islands of skin sparing (pathognomonic pattern)

›Days 3 to 6 distribution

›Centrifugal spread

›Petechiae and ecchymoses

›Spontaneous vs traumatic distinction

›Distribution documentation

›Facial flushing in early disease

›Tourniquet test

04Differential Diagnosis/ddx55

Life-threatening mimics

›Immediate exclusions required

›Malaria

›ICD-10 B50-B54

›Must be excluded in any febrile traveler from endemic area

›Thick and thin blood smear or rapid diagnostic test

›Viral hemorrhagic fevers

›ICD-10 A98-A99

›Travel to Ebola, Marburg, Lassa endemic zones

›Contact and droplet precautions immediately

›Septic shock from bacterial source

›ICD-10 A41.9

›Blood cultures before antibiotics

›Procalcitonin elevation more typical of bacterial sepsis

›Arthropod-borne flaviviral co-circulating infections

›Chikungunya

›Prominent symmetrical arthralgia of small joints

›Similar rash; co-circulates with dengue in same regions

›Zika virus

›ICD-10 A92.5

›Milder fever, conjunctivitis

›Less myalgia than dengue

›West Nile virus

›Neuroinvasive disease more prominent

Febrile illness differentials

›Enteric and systemic infections

›Typhoid fever

›ICD-10 A01.0

05Laboratory Tests/lt72

Core diagnostic labs

›Complete blood count with differential

›Leukopenia

›Typical early finding; <4 x10^9/L common

›Lymphopenia precedes thrombocytopenia

›Thrombocytopenia

›<100 x10^9/L supports dengue

›Platelet nadir commonly at defervescence

›Serial monitoring every 24 hours in febrile phase; every 12 hours in critical phase

›Rising hematocrit

›>=20% rise over baseline = significant plasma leakage WHO criterion

›Tracks disease severity

›Hepatic panel

›AST and ALT

›AST typically greater than ALT in dengue

›>=1000 IU/L = severe organ involvement criterion

›Early predictor of severe disease

›Serum albumin

›Low albumin in febrile phase predicts progression to severe dengue

›Monitors intravascular oncotic status

›Coagulation studies

›Prolonged aPTT common

›PT elevated in severe disease

›DIC assessment when hemorrhagic manifestations present

Dengue-specific diagnostics

›RT-PCR (NAAT)

›Preferred method for early confirmation

›Detects viral RNA in first 7 days of illness

06Diagnostic Tests/dt103

Scoring Systems

›WHO dengue classification and severity criteria

›WHO 2009 classification

›Dengue without warning signs

›Dengue with warning signs

›Severe dengue

›Warning signs triggering inpatient monitoring

›Severe abdominal pain or tenderness

›Persistent vomiting

›Clinical fluid accumulation (highest PPV up to 58% for severe dengue)

›Mucosal bleeding

›Lethargy or restlessness

›Liver enlargement >2 cm

›Rising hematocrit with rapid platelet drop

›Severe dengue criteria

›Severe plasma leakage with shock or respiratory distress

›Severe hemorrhage

›Severe organ impairment (AST or ALT >=1000 IU/L, encephalitis, myocarditis)

›Dengue hemorrhagic fever grading (WHO original)

›Grade I

›Fever with nonspecific constitutional symptoms

›Positive tourniquet test only hemorrhagic manifestation

›Grade II

›Grade I plus spontaneous bleeding

›Grade III

›Circulatory failure signs

›Narrow pulse pressure, hypotension, restlessness

›Grade IV

›Profound shock with undetectable BP and pulse

›Risk stratification scores

›dengue NS1 plus clinical decision aids

›Combination NS1 + IgM + IgG improves sensitivity

›No validated emergency severity score equivalent to CURB-65

›Clinical trajectory supersedes single laboratory value

›Serial platelet and hematocrit trends most actionable

›WHO warning sign checklist used at bedside

MRI

›MRI role in dengue

›Limited routine utility

›Not indicated in uncomplicated or typical dengue

›Availability and time constraints in acute setting

›Dengue encephalitis or neurologic complications

›MRI brain with and without contrast

›Findings: cerebral edema, white matter lesions, basal ganglia involvement

›Dengue myelitis

›MRI spine for limb weakness or sensory level

›Transverse myelitis pattern

›Contraindications

›Hemodynamically unstable patient

›Uncontrolled hemorrhage

›Incompatible implants

CT

›CT indications in dengue

›Intracranial hemorrhage concern

›Altered mental status with severe thrombocytopenia

›CT head non-contrast first line

›Platelet <20 x10^9/L with neurologic symptoms

›Chest CT

›Large or complex pleural effusion characterization

›Diagnostic uncertainty after chest x-ray

›Abdominal CT

›Intraabdominal hemorrhage concern

›Retroperitoneal bleed in severe dengue

›CT findings in dengue complications

›Pleural effusions

›Right-sided predominance

›Bilateral effusions in severe plasma leakage

›Ascites

›Free peritoneal fluid

›Gallbladder wall thickening (hallmark finding)

›Hepatomegaly

›Diffuse or focal changes

›Radiation and contrast consideration

›Pregnancy: minimize exposure; ultrasound preferred

›Renal function assessment for contrast

Ultrasound

›Abdominal ultrasound

›Primary imaging modality in dengue

›Detects subclinical plasma leakage before clinical signs

›Serial ultrasound tracks fluid accumulation progression

›Gallbladder wall thickening

›Pericholecystic fluid (hallmark of dengue plasma leakage)

›Wall thickening >3 mm

›Ascites and peritoneal fluid

›Free fluid in Morrison pouch

›Free fluid in pelvis

›Hepatomegaly assessment

›Liver span measurement

›Echogenicity changes in hepatitis

›Thoracic ultrasound

›Pleural effusion detection

›Right-sided more common in dengue

›B-profile and consolidation assessment

›Superior sensitivity compared to chest x-ray in many settings

›Lung parenchyma assessment

›B-lines indicating pulmonary edema from fluid overload

›Consolidation in secondary pneumonia

›Cardiac POCUS

›Myocarditis assessment

›LV systolic function gross estimate

›Wall motion abnormalities

›Pericardial effusion

›Pericarditis in dengue

›Tamponade physiology assessment

›Inferior vena cava assessment

›Volume status and fluid responsiveness adjunct

›Integrate with clinical exam and urine output

07Disposition/dispo42

Admission criteria

›Mandatory hospitalization indications

›Any WHO warning sign present

›Severe abdominal pain or tenderness

›Persistent vomiting with dehydration

›Clinical fluid accumulation

›Mucosal bleeding

›Lethargy or restlessness

›Liver enlargement >2 cm

›Rising hematocrit with rapid platelet drop

›Severe dengue criteria met

›Shock physiology

›Severe hemorrhage

›Organ impairment (AST or ALT >=1000 IU/L, encephalitis, myocarditis)

›Special population mandatory admission

›All pregnant patients with dengue warning signs

›Infants and young children with warning signs

›Patients with high-risk comorbidities and any warning sign

›ICU level care indications

›Dengue shock syndrome

›Vasopressor requirement

›Persistent shock after fluid resuscitation

›Severe hemorrhage requiring transfusion

›Ventilatory support requirement

›Respiratory failure from pleural effusions

›ARDS in severe dengue

Discharge criteria

›Outpatient management criteria (dengue without warning signs)

08Treatment/t80

Fluid management

›Oral rehydration for outpatient dengue

›Oral rehydration solution, water, juices, soups

›Cornerstone of outpatient management

›Small frequent volumes preferred over large boluses

›Target 2 to 3 liters per day oral intake

›Monitor urine output at home

›Adequate output target: urination at least every 6 hours

›Avoid alcohol due to hepatotoxicity risk with transaminitis

›IV fluid resuscitation for compensated shock

›Isotonic crystalloid first line

›Normal saline or Lactated Ringer

›5 to 10 ml/kg over 1 hour

›Reassess after each bolus; titrate to response

›If clinical improvement after bolus

›Reduce rate to 3 to 5 ml/kg per hour for 2 to 4 hours

›Then reduce to 2 to 3 ml/kg per hour for 2 to 4 hours

›Continue to taper based on hemodynamic response

›Colloid consideration

›Colloid (fresh frozen plasma, 5% albumin) if no improvement with isotonic crystalloid

›10 ml/kg over 30 minutes

›Class IIa recommendation in refractory compensated shock

›IV fluid resuscitation for decompensated shock

›Rapid isotonic crystalloid

›20 ml/kg over 15 to 30 minutes

›Repeat up to 40 to 60 ml/kg total if needed

›Vasopressors if no improvement after adequate fluid

›Norepinephrine 0.01 to 3 mcg/kg/minute IV infusion

›Titrate to MAP >=65 mmHg

›ICU monitoring required

›Avoid excessive fluid overload

›Risk of pulmonary edema

›Especially during convalescent phase when plasma returns

Antipyretic and supportive therapy

›Fever management

›Acetaminophen (paracetamol) only for fever control

›Adults: 500 to 1000 mg PO every 4 to 6 hours as needed

›Maximum 3000 to 4000 mg per 24 hours; reduce to 2000 mg/day in hepatic impairment

›Pediatric: 10 to 15 mg/kg per dose every 4 to 6 hours; maximum 5 doses per 24 hours

›Avoid NSAIDs and aspirin

›Increased bleeding risk via platelet inhibition

›Class I contraindication in dengue

›Tepid sponging for hyperthermia adjunct

›Nausea and vomiting management

›Metoclopramide IV

›10 mg IV every 8 hours

›Short course; dystonia monitoring

›Ondansetron IV

›4 to 8 mg IV every 8 hours

›QT prolongation risk review with thrombocytopenic coagulopathy

Transfusion and hemorrhage management

›Red blood cell transfusion

›Indication: clinically significant active hemorrhage

›Not prophylactic transfusion based on platelet count alone

›Hemodynamic instability from blood loss

›pRBC 1 unit IV; reassess after each unit

›Whole blood alternative in resource-limited settings

›Platelet transfusion

›Prophylactic platelet transfusion NOT beneficial

›May contribute to fluid overload

›No mortality benefit demonstrated

›WHO guidance against routine prophylactic transfusion

›Consider platelet transfusion when

›Clinically significant bleeding with platelet <20 x10^9/L

›Pre-procedure with platelet <50 x10^9/L

›Avoid intramuscular injections during acute illness

›Risk of large hematoma formation

›Subcutaneous or IV routes preferred

›Anticoagulant medications

›Hold all anticoagulants during acute dengue illness

›Warfarin, direct oral anticoagulants, heparin

›Resume only when platelet count recovering and hemorrhagic risk resolved

Therapies without proven benefit

›Corticosteroids

›Not recommended in routine dengue management

›No mortality benefit; potentially harmful

›Exception: autoimmune complications of dengue

›Class III recommendation (harm possible)

›Antiviral agents

›No approved antiviral therapy for dengue

›Sofosbuvir, ivermectin, chloroquine all without proven benefit

›Investigational agents not for standard practice

›Intravenous immunoglobulin

›No role in standard dengue management

09Special Populations/sp75

Pregnancy

›Physiologic and risk considerations

›Dengue in pregnancy carries increased maternal and fetal risk

›Increased risk of preterm delivery

›Increased risk of low birth weight

›Maternal hemorrhage risk amplified by physiologic coagulopathy

›Physiologic thrombocytopenia of pregnancy complicates interpretation

›Baseline platelet count review essential

›Serial platelet trending required

›Plasma volume expansion of pregnancy may mask plasma leakage

›Lower threshold for serial ultrasound assessment

›Mandatory hospitalization

›All pregnant patients with dengue should be hospitalized

›WHO Class I recommendation regardless of warning signs

›Obstetrics team involvement from admission

›Fetal monitoring when viable gestation

›Non-stress test or biophysical profile

›Continuous monitoring in shock or hemorrhage

›Treatment modifications in pregnancy

›Acetaminophen safe for antipyretic use

›Avoid NSAIDs and aspirin (fetal and maternal bleeding risk)

›Fluid management

›Careful fluid balance monitoring

›Fluid overload risk with pre-eclampsia overlap

›Avoid corticosteroids except if imminent delivery and fetal lung maturation indicated

›Dengvaxia vaccine is contraindicated in pregnancy

Geriatric

›Age-related risk factors

›Comorbidities compound severity

›Diabetes, cardiovascular disease, renal disease (all independently increase severe dengue OR)

›Polypharmacy interactions with treatment

›Dehydration tolerance reduced

›Diminished thirst response

›Reduced renal concentrating ability

›Atypical presentation risk

›Absent fever possible with immunosenescence

›Confusion as presenting complaint

›Clinical management modifications

›Lower threshold for hospitalization

›Any warning sign or high-risk comorbidity

›Frailty as independent disposition modifier

›Acetaminophen dose caution

›Reduce maximum dose with hepatic or renal impairment

›2000 mg per 24 hours maximum in frail older adults

›Fluid resuscitation caution

›Cardiac reserve often diminished

›Smaller fluid boluses with frequent reassessment

›5 ml/kg boluses with close monitoring in known heart failure

›Anticoagulant management complexity

›Many older adults on anticoagulation; hold during acute illness

›Warfarin reversal if supratherapeutic during hemorrhage

Pediatrics

›Physiologic differences

›Higher risk of severe dengue in young children

›DENV serotype 2 particularly associated with severe pediatric disease

›Vascular permeability response more pronounced

›Compensatory mechanisms mask shock longer

›Heart rate and pulse pressure more reliable than BP alone

›Capillary refill and mental status critical monitoring parameters

›Platelet nadir lower and faster in children

›More frequent platelet monitoring

›Lower absolute threshold for concern

›Weight-based fluid management

›Compensated shock in children

›Isotonic crystalloid 5 to 10 ml/kg over 1 hour

›Reassess and repeat if needed up to 20 to 30 ml/kg total

›Decompensated shock in children

›20 ml/kg isotonic crystalloid over 15 minutes

›Repeat up to total 40 to 60 ml/kg; escalate to colloid if no response

›Pediatric antipyretic dosing

›Acetaminophen 10 to 15 mg/kg per dose PO or PR

›Maximum 5 doses per 24 hours

›Maximum single dose 1000 mg

›Ibuprofen and aspirin strictly contraindicated

›Dengue monitoring in children

›Feeding tolerance as early severity marker

›Urine output target >=1 ml/kg per hour

›Hospitalize any child with warning signs without exception

10Background/b68

Epidemiology

›Global burden

›Dengue is the most prevalent mosquito-borne viral infection globally

›Estimated 390 million infections per year; 96 million clinically apparent

›3.9 billion people in 128 countries at risk

›Case fatality rate

›Untreated dengue shock syndrome: up to 20%

›With appropriate supportive care: <1%

›Early recognition and fluid management reduces mortality by >=20-fold

›Approximately 60 to 80% of infections are asymptomatic

›<=5% of symptomatic cases progress to severe disease

›Vector and transmission

›Primary vector: Aedes aegypti

›Daytime biting; urban and peri-urban environments

›Breeds in small standing water collections

›Secondary vector: Aedes albopictus

›Broader geographic range including temperate zones

›Expansion of dengue geographic spread

›No person-to-person transmission except rare vertical transmission and blood products

›Serotype distribution

›Four antigenically distinct serotypes (DENV-1, DENV-2, DENV-3, DENV-4)

›Lifelong immunity to infecting serotype

›Temporary cross-protective immunity; subsequent infection with different serotype = higher severity risk

›DENV-2 particularly associated with severe pediatric disease

Pathophysiology

›Triphasic clinical course

›Febrile phase (days 1 to 3)

›Viremia and systemic inflammatory response

›Fever, myalgia, rash from immune activation

›Critical phase (days 4 to 6)

›Plasma leakage due to increased vascular permeability

›Highest risk of shock, hemorrhage, organ failure

›Defervescence coincides with peak vascular leak

›Convalescent phase (days 7 to 10)

›Plasma re-absorption; risk of fluid overload if over-resuscitated

›Bradycardia and rash may occur

›Vascular permeability mechanism

›Nonstructural protein NS1 activates complement and disrupts endothelium

›Endothelial glycocalyx degradation

›Selective plasma leakage into serous cavities (pleural, peritoneal, pericardial)

›Antibody-dependent enhancement (ADE) in secondary infection

›Non-neutralizing antibodies from prior serotype enhance viral uptake

›Higher viral loads amplify inflammatory response

›Cytokine storm

›TNF-alpha, IL-6, IL-10 drive vascular leak and thrombocytopenia

›Thrombocytopenia mechanisms

›Peripheral destruction by antibody-mediated platelet clearance

›Bone marrow suppression by DENV direct infection of megakaryocytes

›Consumption during endothelial damage

Therapeutic Considerations

›Fluid management principles

›Goal is to maintain circulation without overloading

›Plasma leakage is transient (24 to 48 hours critical phase)

›Aggressive rehydration during leakage risks fluid overload at reabsorption

›Clinical endpoints superior to fixed-volume protocols

›Urine output, pulse pressure, capillary refill are bedside guides

›Hematocrit fall can indicate plasma reabsorption or hemorrhage; context critical

›Colloid advantage in refractory shock

›Maintains oncotic pressure during plasma leakage better than crystalloid

›No proven mortality benefit over aggressive crystalloid titration

›No disease-modifying pharmacotherapy

›No antiviral with proven efficacy

›Dengue management remains entirely supportive

›Vaccine prevention: Dengvaxia approved for seropositive individuals in endemic areas

›Seronegative individuals: vaccine increases risk of hospitalization

›Pre-vaccination serology required for safety

›Antibiotic stewardship

›Antibiotics not indicated for uncomplicated dengue

›Viral etiology; no primary bacterial target

›Reserve for confirmed or strongly suspected bacterial co-infection

›CRP elevation and procalcitonin rise support co-infection consideration

11Patient Discharge Instructions/pdi34

copy discharge instructions

›Dengue fever home care instructions

›Fluids and hydration

›Drink at least 2 to 3 liters per day of fluids

›Water, oral rehydration solutions, juices, and soups all acceptable

›Avoid alcohol during illness

›Small, frequent sips if nauseous

›Fever management at home

›Acetaminophen (Tylenol) only for fever and pain

›Do NOT take ibuprofen, naproxen, aspirin, or any anti-inflammatory medication

›These medications increase risk of serious bleeding

›Activity

›Rest as needed; avoid strenuous activity until fully recovered

›Mosquito precautions to prevent infecting others via mosquito bites

›Warning signs to return to emergency department immediately

›Severe abdominal pain or vomiting that will not stop

›Bleeding from gums, nose, or in urine, vomit, or stool

›Blood in vomit or black/tarry stools

›Difficulty breathing or shortness of breath

›Dizziness when standing; fainting

›Confusion, excessive sleepiness, or restlessness

›Cold or pale skin with fast heart rate

›Fever returns after being afebrile (can indicate transition to critical phase)

›No urination for more than 6 hours

›Follow-up instructions

›Blood work (CBC) required daily until platelet count is stable and rising

›Platelet count >=50,000 and improving before discharge confirmed safe

›Confirm lab appointment before leaving ED

12References/r19

Guidelines and key sources

›WHO dengue guidelines

›WHO Dengue Guidelines for Diagnosis, Treatment, Prevention and Control, 2009

›WHO Handbook for Clinical Management of Dengue, 2012

›Primary source for triphasic staging and warning sign criteria

›Society and evidence-based guidelines

›Pan American Health Organization (PAHO) dengue clinical guidance

›Centers for Disease Control and Prevention (CDC) dengue clinical guidance

›International Society for Infectious Diseases dengue resources

›Key clinical evidence

›Secondary infection OR 2.26 for severe dengue (referenced comorbidity data)

›Comorbidity risk ORs: diabetes 4.38, renal disease 4.67, hypertension 2.19, cardiovascular disease 2.79

›Tourniquet test sensitivity approximately 90% for early dengue

›Clinical fluid accumulation PPV up to 58% for severe dengue

›Early recognition and fluid management reduces mortality >=20-fold

›Coding references

›ICD-10 A90 dengue fever (classical dengue)

›ICD-10 A91 dengue hemorrhagic fever

›SNOMED CT dengue fever disorder concept

›SNOMED CT dengue hemorrhagic fever concept

Evidence & Review