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 differential diagnosis of malaria includes:
TREATMENT OF MALARIA3
WHO has recently issued new guidelines for the treatment of malaria.
FALCIPARUM MALARIA (Table 65.1)
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 |
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.
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: • 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 |
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.
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:
OTHER FORMS OF MALARIA
Treatment of other forms of malaria is outlined in Table 65.3.
Uncomplicated P. vivax malaria |
Chloroquine 25 mg base/kg divided over 3 days, combined with primaquine 0.25 mg base/kg, taken with food once daily for 14 days is the treatment of choice for chloroquine-sensitive infections. In Oceania and Southeast Asia the dose of primaquine should be 0.5 mg/kg. |
Amodiaquine (30 mg base/kg divided over 3 days as 10 mg/kg single daily doses) combined with primaquine should be given for chloroquine-resistant vivax malaria. |
Complicated P. vivax malaria |
Treatment is the same as severe P. falciparum malaria. |
P. ovale and malariae malaria |
Treatment is the same as uncomplicated vivax malaria but without primaquine for malariae. |
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
PATHOGENESIS
Tuberculosis (TB) is usually caused by Mycobacterium tuberculosis and four others (M. bovis, M. africanum, M. microti and M. canetti) grouped in the Mycobacteriumcomplex. The genus Mycobacterium consists of many different species, all of which appear similar on acid-fast staining.