Iraq: the environmental challenge to HM land forces.

In 2003, occasional military patients with hyponatraemia, hypokalaemia and alkalosis were encountered in Iraq. Development of central pontine myelinolysis in one patient indicated treatment should be cautious. Two years later, heat illness continued to occur during the very hot summer months and 23 cases were admitted to a British military field hospital near Basra, Iraq. Incidence was < 0.15% of deployed personnel per summer month. Serum sodium and potassium concentrations were directly (r = 0.66, p = 0.0002) and serum sodium and bicarbonate concentrations inversely (r= -0.64, p = 0.002) correlated. The magnitude of these changes was unrelated to the glomerular filtered load of sodium. While blood pressure was undiminished, estimated glomerular filtration rate was reduced. These electrolyte changes were compatible with secondary hyperaldosteronism but field conditions constrained further investigation. Hyponatraemia was probably due to salt deficiency rather than overhydration. In some military personnel summer salt supplementation could be essential during operations in hot countries.