Category:Electrolyte replacements

An electrolyte replacement is a medicine preparation of one or more of the principal ions of the extracellular and intracellular fluid: sodium, potassium, calcium, magnesium, chloride, bicarbonate, and (less commonly used as medicine) phosphate. The category includes the intravenous crystalloid fluids of resuscitation and maintenance care, the oral rehydration salts of the cholera and gastroenteritis pharmacopoeia, and the individual ion preparations (potassium chloride for hypokalemia, magnesium sulfate for hypomagnesemia or eclampsia, calcium gluconate for hypocalcemia or hyperkalemia, sodium bicarbonate for severe acidosis). These medicines are among the oldest in continuous use in hospital medicine and remain among the most consequential.

The intravenous administration of electrolyte solution was invented in response to a public-health crisis. In 1831 the second cholera pandemic reached England, and the Edinburgh physician William Brooke O'Shaughnessy examined samples of the blood and the rice-water stool of cholera victims; he reported in the Lancet that the blood was concentrated and chemically depleted of salt, and that the stool was, by contrast, enriched in salts and water. He concluded that intravenous restoration of the lost salt and water might save the patient.^[1] Shortly afterwards in 1832, the Leith physician Thomas Latta administered the first intravenous saline infusion to a moribund cholera patient, an elderly woman, and reported the result in the same journal: she rallied within minutes and survived for some hours. Latta's solution was poorly characterised (the contemporary chemistry could not give him a precise composition), and the technique was not widely adopted at the time, but the principle that intravenous salt and water could replace what had been lost was established in 1832.

The pharmacology of crystalloid resuscitation was systematised over the following century. The physiologist Sydney Ringer at University College London reported in 1882 that frog hearts beat longer in vitro when the perfusate contained, in addition to sodium chloride, small concentrations of potassium and calcium chloride; the resulting Ringer's solution became the standard physiologic salt solution.^[2] In 1932 the American pediatrician Alexis Hartmann modified Ringer's by adding sodium lactate (intended to be metabolised in vivo to bicarbonate and so to provide alkali without the precipitation problems of bicarbonate), producing the lactated Ringer's solution that remains, with minor variation, the standard balanced crystalloid of contemporary practice. The competing alternative, normal saline (0.9 percent sodium chloride, isotonic with plasma but with a chloride concentration of 154 mmol/L, substantially higher than plasma's 100 mmol/L), entered routine use in the late nineteenth century; the SMART and SALT-ED trials in 2018 and the PLUS trial in 2022 showed that balanced solutions reduced acute kidney injury compared to saline in critically ill adults, although the absolute effect was modest.^[3]

The oral rehydration story is a second chapter, with public-health consequences arguably larger than any other single twentieth-century medicine. The observation that intestinal glucose absorption was coupled to sodium absorption by the sodium-glucose cotransporter SGLT1, demonstrated in the 1950s and 1960s by Crane and Schultz, suggested that oral salt-and-water solution containing glucose at the appropriate ratio could replace intestinal losses without requiring intravenous access. In the cholera outbreak among Bangladeshi refugees in West Bengal in 1971, Dilip Mahalanabis of the Johns Hopkins International Centre for Medical Research and Training and his colleagues administered an oral solution of sodium chloride, sodium bicarbonate, potassium chloride, and glucose to several thousand patients in conditions where intravenous resuscitation was impossible; the mortality from cholera, then approaching 30 percent without IV therapy, fell to under 4 percent.^[4] The WHO formula (later modified to a reduced-osmolarity version that performed better) has been credited by the Lancet as "potentially the most important medical advance of the twentieth century" and is estimated to save more than a million children per year from death by diarrhoeal dehydration.

The individual electrolyte preparations are used in correction of specific deficits. Potassium chloride is administered orally (slow-release tablets, liquid) for chronic hypokalemia and intravenously (at carefully limited infusion rates to avoid arrhythmia and pain at the infusion site) for acute hypokalemia or for potassium depletion in diabetic ketoacidosis. Magnesium sulfate is given intravenously for hypomagnesemia (often co-existing with hypokalemia and refractory until the magnesium is replaced), for eclampsia and severe pre-eclampsia (the international standard for prevention of eclamptic seizure since the Magpie trial of 2002), for torsades de pointes, and (in inhaled form, less established) for severe asthma. Calcium gluconate or chloride is given intravenously for symptomatic hypocalcemia, for the cardiac stabilisation of hyperkalemia (independent of the potassium concentration), for the antidotal management of calcium channel blocker overdose, and for magnesium overdose. Sodium bicarbonate is given intravenously for severe metabolic acidosis with haemodynamic compromise and for the alkalinisation of urine in tricyclic antidepressant or salicylate overdose.

The use of these medicines requires attention to the rates of administration. Rapid intravenous potassium causes arrhythmia and cardiac arrest; rapid hyponatremia correction with hypertonic saline causes osmotic demyelination; rapid calcium administration in a peripheral vein causes painful infiltration and tissue necrosis; rapid magnesium administration causes hypotonia and respiratory depression. The clinical pharmacology of electrolyte replacement is therefore as much about the rate and the route as about the dose.

By ion and route:

• Intravenous crystalloid fluids:
  • Isotonic saline (0.9% sodium chloride, "normal saline")
  • Balanced solutions: lactated Ringer's, Plasma-Lyte, Hartmann's solution
  • Hypertonic saline (1.8%, 3%, 7.5%, 23.4%): for symptomatic hyponatremia, raised intracranial pressure
  • Dextrose solutions (D5W, D10W) for free-water replacement and as glucose source
  • Combined solutions (D5 ½ NS with potassium, the maintenance combinations)
• Oral rehydration solutions (WHO formula and the commercial Pedialyte / Hydralyte derivatives)
• Potassium: potassium chloride (oral slow-release, liquid, intravenous); potassium bicarbonate, citrate (for combined alkali and potassium replacement)
• Magnesium: magnesium sulfate (intravenous, intramuscular), magnesium oxide and citrate (oral)
• Calcium: calcium gluconate and chloride (intravenous), calcium carbonate and citrate (oral); the calcium supplements for osteoporosis are cross-listed
• Sodium bicarbonate (intravenous, oral)
• Phosphate: sodium and potassium phosphate (intravenous, oral; rarely the sole indication, often combined with calcium)
• Zinc and trace elements: not strictly electrolytes but commonly co-supplemented in parenteral nutrition

The boundary of this category is "medicine that replaces an inorganic ion of the body fluids." The iron supplements are not electrolytes in the strict sense (iron is not an extracellular-fluid ion but rather a transition metal of haemoglobin and other proteins) and are collected separately under iron supplements and hematinics. The trace elements (zinc, copper, selenium, chromium, manganese, iodine, molybdenum) are added to total parenteral nutrition solutions and are listed under their own category. The synthetic colloids (the hydroxyethyl starches, the dextrans, the gelatins) are plasma volume expanders rather than electrolyte replacements and have largely been retired in favour of crystalloids after large outcome trials demonstrated kidney-injury and bleeding signals with the starches. Blood products (packed red cells, fresh frozen plasma, platelets, cryoprecipitate, albumin solutions) are not electrolyte replacements in this category sense and are listed elsewhere.

This category page is an encyclopedia article about its subject. The actual index of medicines belonging to the category is generated automatically by the wiki engine, from category-membership declarations on the individual medicine pages, and appears at the foot of the page below the references.