Dengue fever - occurance , diagnosis and management

Dengue fever is quite common during the rainy season

1. Dengue fever By-Prerana

2. Dengue fever Introduction: Dengue is an acute infectious viral disease. It is caused by Flavi virus , Dengue serotype DENV 1,2,3,4. Transmitted by vector- Aedes aegypti Epidemic in the rainy season.

3. Dengue infection Symptomatic Asymptomatic Mild. Moderate. Severe. Dengue shock Syndrome With high risk/ comorbid conditions. With warning signs Infants,old pregnancy, immunosuppressive,chronic illness

4. Pathophysiology Sequential infection with any two of the four serotypes of dengue virus results in DHF/DSS. Antibodies produced during 1 st infection are able to neutralise 2 nd infection of the same serotype. If infection with other serotype occurs , the 2 nd infection is under the influence of enhancing antibodies and the disease is severe as the antibodies generated previously are not specific for other serotypes. Hence they bind to virions but do not neutralise them, instead increase the uptake by antigen presenting cells – activation and proliferation of memory T cells and the release of cytokines. That causes endothelial cell damage manifesting as increased capillary permeability- haemoconcentration and circulatory insufficiency.

5. Phases Febrile phase Critical phase Recovery phase

6. Criteria for DHF Fever for 2-7 days Positive tourniquet test with bleeding tendencies- bleeding from gums or injection sites , epistaxis etc. Thrombocytopenia Rise in haematocrit >20% Sign of plasma leakage like pleural effusion , ascites and hypoproteinemia.

7. Febrile phase High grade fever lasting 2-7 days Facial flushing with skin erythema, myalgia , arthralgia , severe backache(break bone fever), pharyngitis , nausea and vomiting . Mild hemorrhagic manifestations like petechiae and mucosal bleeding. A positive tourniquet test increases the probability of dengue.

8. Warning signs Abdominal pain Persistent vomiting Lethargy , restlessness Liver enlargement >2cms Clinical fluid accumulation Bleeding manifestations like mucosal bleeds, epistaxis or black stools. Laboratory- Increase in hematocrit with concurrent decrease in the platelet count.

9. Critical phase Usually occurs after 3-4 days of onset of fever. An increase in capillary permeability with increasing hematocrit. Progressive decrease in the white cell and platelet count. Significant plasma leakage. Respiratory distress due to pleural effusion or ascites may occur. Pleural effusion and ascites maybe clinically detectable depending on the degree of plasma leakage and the volume of fluid therapy. Those who deteriorate will manifest with warning signs(severe dengue).

10. Recovery phase After 24-48 hours of critical phase then gradual re absorption of extra vascular fluid takes place in the next 48-72 hours. Hematocrit stabilises or may be lower due to the dilutional effect of reabsorbed fluid. Some may experience generalised rashes called isles of white in the sea of red. Overall clinical improvement with good appetite , GI symptoms abate and general well being improves.

11. Investigations Confirmation of diagnosis by: Direct methods- virus isolation by culture,genome detection by PCR , NS1 antigen detection. Indirect methods- IgM detection, IgG detection Full blood count must be done and repeated daily until critical phase is over. Children with severe dengue infection show increasing PCV and low platelet and leukocyte count with lymphocyte predominance. X-Ray chest and USG abdomen may show varying degree of fluid accumulation.

12. Prevention Elimination of adult aedes aegypti mosquitoes and larvae.

13. Indication of platelet transfusion Platelet count less than 10000/meter cube in absence of bleeding manifestations. Haemorrhage with or without thrombocytopenia.

14. Dengue management with risk factors

15. Management of bleeding Petechial spots and mild mucosal bleed –supportive care , hydration and monitoring. Monitoring of BP,RR,HR and fluid input and urine output every 30 minutes till patient is stable , then every 2 to 4 hours. Severe bleeding and hemodynamic instability—combination of fresh frozen plasma and platelet concentration to be considered.

16. Severe dengue Plasma leakage leading to shock / fluid accumulation with respiratory distress. Severe bleeding Organ dysfunction Assessment of shock Hypotension Undetectable BP NS/RL -10-20ml/kg. Once improvement. Secure two IV lines No improvement If PCVis falling over 1 hr begins,gradually Administer NS in one Start colloids Without improvement in decrease the infusion Line and 5% dextrose 10ml/kg. Vitals –blood transfusion and potassium in another. Is recommended.

17. Criteria for discharge No fever for 24-48 hours. Normal blood pressure. Adequate urine output. No respiratory distress. Platelet count >50,000/mm3

18. Complications of DHF Convulsions due to high fever. Unrecognised severe plasma leakage leading to shock. Profound shock leading to metabolic acidosis and severe bleeding as a result of DIC and multiorgan failure— renal and hepatic dysfunction. Excessive fluid replacement leads to massive effusions causing respiratory compromise. Metabolic abnormalities like hypoglycaemia, hypocalcemia or hyponatremia.

19. Management-Dengue without warning signs Bed rest. Tepid sponging to reduce the body temperature. Symptomatic treatment with paracetamol. Encouraged to drink plenty of fluids. Aspirin/NSAIDS like ibuprofen should be avoided as they may predispose to mucosal bleed. Careful monitoring of warning signs with PCV and platelet count.

20. Differential diagnosis Chikungunia infection— fever is for a shorter duration and thrombocytopenia and bleeding is less frequent . Patients present with skin eruptions, mucosal lesions , polyarthralgia and encephalopathy. Influenza Malaria Enteric fever Leptospirosis

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