Cholera

Cholera is mentioned in Sivakumar and Pelly's chapter on tropical diseases in Oh's Manual, barely a paragraph nested between typhoid fever and leptospirosis. It has not been interrogated in the SAQs directly, and is an infrequent differential. In Western ICUs, it is so infrequent that most physicians will not have seen one. Beyond Oh's Manual ICU literature concerning cholera is almost non-existant. It is usually mentioned as a footnote by authors discussing electrolyte and acid-base disturbances.

Microbiology

• Vibrio cholera is an aerobic Gram-negative rod
• It is a rapidly motile comma-shaped bacillus.
• The diarrhoea is caused by the action of the enterotoxin on cAMP production; the massive increase in enterocyte cAMP results in absurd excesses of secretory activity.
• The incubation period varies from 12 hours to several days.

Clinical manifestations and features of history

• Returning traveller
• Painless watery diarrhoea - up to 20L/day
• Vomiting
• Painful muscle cramps
• Severe acidosis and Kussmaul breathing
• Fever is rare

Characteristic laboratory findings

• Stool examination shows neither leucocytes nor erythrocytes.
• Ridiculous electrolyte derangement is to be expected
  • Though one would expect a hyperchloraemic acidosis, this is one of those situations where albumin and phosphate become so concentrated by dehydration that the anion gap actually increases. One should expect some mixture of NAGMA and HAGMA.

Critical complications

• Shock (hypovolemic)
• Acute renal failure
• Seizures and coma (due to electrolyte depletion)
• Severe acidosis
• Respiratory failure
• Rhabdomyolysis due to hypokalemia

Diagnostic approach

• O antigen in stool samples: rapid and as sensitive and specific as stool culture.
• Stool culture
• Stool Gram stain

Management

• The Sanford Guide recomends doxycycline or azithromycin
• Aggressive rehydration is the key