Tropical diseases

Chapter 65 Tropical diseases



Once an exotic and esoteric topic, modern travel and the quest for unusual holidays has the potential to bring tropical diseases to every ICU. This chapter covers some important diseases, which are common in the tropical belt.



MALARIA




CLINICAL FEATURES




SEVERE MALARIA




Definition


The diagnosis of severe malaria requires the presence of one or more of the following with no other confirmed cause occurring in a patient with asexual Plasmodium falciparum parasitaemia:1











The incubation period is at least 7 days. The usual range is 9–14 days but this may be longer. Anaemia, jaundice, renal dysfunction, haemostatic abnormalities, thrombocytopenia, pulmonary oedema, shock, hypoglycaemia, and severe metabolic acidosis are common in severe malaria. Several of the above coexist or may develop in rapid succession. Cough, convulsions, and hypoglycaemia are more common in children. Jaundice is common, but hepatic failure is uncommon. The acidosis of malaria is multifactorial and probably very similar to other forms of sepsis involving tissue hypoxia, liver dysfunction, and impaired renal handling of bicarbonate.


The differential diagnosis of malaria includes:









Pregnancy increases the risk of development of severe malaria. During pregnancy both maternal and fetal morbidity and mortality are increased.


Poor prognostic indicators include age under 3 years, cerebral malaria, circulatory collapse and organ dysfunction. Laboratory evidence of poor prognosis includes hyperparasitaemia (> 250 000/μl or > 5%), peripheral schizontaemia, severe anaemia (PCV < 15% or Hb < 50 g/l), raisedblood urea > 60 mg/dl and serum creatinine > 265 μmol/l (> 3.0 mg/dl), raised venous lactate (> 5 mmol/l), raised CSF lactate (> 6 mmol/l), low CSF glucose and a very high concentration of TNF-α.





TREATMENT OF MALARIA3


WHO has recently issued new guidelines for the treatment of malaria.



FALCIPARUM MALARIA (Table 65.1)


To counter the threat of resistance of P. falciparum to monotherapies, and to improve treatment outcome, combinations of antimalarials are now recommended by WHO for the treatment of falciparum malaria. Antimalarial combination therapy is the simultaneous use of two or more blood schizontocidal drugs with independent modes of action. Artemisin-based combination therapy (ACT) is the recommended treatment for uncomplicated falciparum malaria.


Table 65.1 WHO recommendations for treatment of uncomplicated P. falciparum malaria



















Artesunate + amodiaquine
4 mg/kg of artesunate and 10 mg base/kg of amodiaquine given once a day for 3 days
Artesunate + sulfadoxine–pyrimethamine
4 mg/kg of artesunate given once a day for 3 days and a single administration of sulfadoxine–pyrimethamine (25/1.25 mg base/kg body weight) on day 1
Artesunate + mefloquine
4 mg/kg of artesunate given once a day for 3 days and 25 mg base/kg of mefloquine, usually split over 2 or 3 days
Artemether–lumefantrine
Are available as co-formulated tablets containing 20 mg of artemether and 120 mg of lumefantrine. The recommended treatment for persons weighing more than 34 kg is 4 tablets twice a day for 3 days

One of the following ACTs is currently recommended: artesunate + amodiaquine, artesunate + sulfadoxine–pyrimethamine, artesunate + mefloquine, or artemether–lumefantrine. The choice of ACT in a country or region will be based on the level of resistance of the partner medicine in the combination.



Severe falciparum malaria (Table 65.2)


Two classes of drug are currently available for the parenteral treatment of severe malaria: the cinchona alkaloids (quinine and quinidine) and the artemisinin derivatives (artesunate, artemether and artemotil). Recent evidence4,5 suggests superior efficacy of artesunate over quinine in adults. The dosage of artemisinin derivatives does not need adjustment in vital organ dysfunction.


Table 65.2 WHO recommendations for treatment of severe P. falciparum malaria









Artesunate
2.4 mg/kg i.v. or i.m. given on admission (time = 0), then at 12 hours and 24 hours, then once a day is recommended in low transmission areas or outside malaria endemic areas. If artesunate is not available, quinine i.v. should be used.
For children in high transmission areas, one of the following antimalarial medicines is recommended as there is insufficient evidence to recommend any of these antimalarial medicines over another for severe malaria:



Following initial parenteral treatment, once the patient can tolerate it, current practice is to switch to oral therapy and complete a full 7 days of treatment. In non-pregnantadults, doxycycline (3.5 mg/kg per day) is added to quinine, artesunate or artemether and should also be given for 7 days. During pregnancy or in children, clindamycin is used instead of doxycycline.


In patients with features of severe malaria, a mixed infection with falciparum should be assumed even if only a benign species is identified in the film. Occasionally, severe malaria can occur with vivax species. If the clinical suspicion is high, a therapeutic trial of antimalarial treatment is justified, even if the film is negative.


Severe malaria leads to severe septic shock, and the principles of management are the same including resuscitation and provision of supportive treatment. These patients are at risk of acute lung injury but do need adequate fluid resuscitation. Convulsions must be actively treated. Complications should be managed as they present. The threshold for dialysis should be low. Pneumonia and bacterial septicaemia are also common, and should be recognised and treated.


Exchange blood transfusion (EBT) has been used in severe malaria. However, recent WHO guidelines3 do not recommend EBT, and note the lack of consensus on indications, benefits and dangers involved, or on practical details such as the volume of blood that should be exchanged. Traditional indications for EBT if pathogen-free compatible blood is available are:







PROGNOSIS


Data are largely derived from endemic areas where presentation with convulsions, acidosis or hypoglycaemia is associated with a poorer outcome. Mortality in an artesunate-treated severe falciparum malaria group in one trial5 was still high (15% vs. 22% in quinine-treated patients). In cerebral malaria, mortality is around 20%. The prognosis of cerebral malaria is frequently determined by the management of other complications such as renal failure and acidosis, but neurological sequelae are increasingly recognised.



TUBERCULOSIS



< div class='tao-gold-member'>

Jul 7, 2016 | Posted by in CRITICAL CARE | Comments Off on Tropical diseases

Full access? Get Clinical Tree

Get Clinical Tree app for offline access