Saline solution drip

This was initially introduced by Latta in 1832 during a cholera epidemic which had reached Britain in the previous year and was killing huge numbers of people. Latta was the leader of a group of three Leith doctors, the other two being Dr Thomas Craigie and Dr Robert Lewins. Whilst all three were based in Leith the experiments were undertaken on five patients in the Edinburgh Cholera Hospital on Drummond Street, a building which was the original Old Surgeons' Hall and which had been bought by the Royal Infirmary of Edinburgh. The value of isolating such patients in specialist hospitals had been learned early in the epidemic.^[6] Although his results were both remarkably good and effective in saving human lives, the research appeared to thereafter be forgotten for 70 years before rematerialising in wider use.

Intravenous theory had existed prior to this date but had never been successfully put into practice. The critical aspect of Latta's theory was the nature of the liquid, correctly speculating that a salt solution could substitute for blood. Basing his experiments on the theories of Dr William Brooke O'Shaughnessy, Latta had equally observed that cholera victims lost a huge proportion of water content from their blood. Replenishment of this in combination with "oxygenating salts" were seen as key to patient recovery. The theory was then put into practice. Latta at first tried to administer the salt solution rectally, but on 23 May 1832 he wrote to the Central Board of Health notifying them of his intention to begin the treatment intravenously. This method was an immediate success. His letter described his method and response: "I attempted to restore the blood to its natural state, by injecting copiously into the larger intestines warm water.. trusting that the power of absorption might not be altogether lost, but by these means I produced, in no case, any permanent benefit.. I at length resolved to throw the fluid immediately into the circulation. In this, having no precedent to direct me, I proceeded with much caution. The first subject of experiment was an aged female. She had apparently reached the last moments of her earthly existence, and now nothing could injure her – indeed, so entirely was she reduced, that I feared I should be unable to get my apparatus ready ere she expired. Having inserted a tube into the basilic vein, cautiously – anxiously, I watched the effects; ounce after ounce was injected, but no visible change was produced. Still persevering, I though she began to breathe less laboriously, soon the sharpened features, and sunken eye, and fallen jaw, pale and cold, bearing the manifest impress of death's signet, began to glow with returning animation; the pulse, which had long ceased, returned to the wrist; at first small and quick, by degrees it became more and more distinct ... and in the short space of half an hour, when six pints had been injected, she expressed in a firm voice that she was free from all uneasiness, actually became jocular, and fancied all she needed was a little sleep."^[7][8][9]

The results were published in The Lancet on 23 June 1832 and the methodology began to spread; by then the epidemic was on the wane.

This extract from The Lancet graphically illustrates the treatment: "The very remarkable effects of this remedy require to be witnessed to be believed. Shortly after the commencement of the injection the pulse, which was not perceptible, gradually returns; the eyes, which were sunk and turned upwards, are suddenly brought forward, and the patient looks round as if in health, the natural heat of the body is gradually restored, the tongue and breath, which were in some cases at the temperature of 79° and 80°, rise to 88° and 90°, and soon become natural, the laborious respiration and oppression of weight of the chest are relieved ... the whole countenance assumes a natural healthy appearance".^[10]

Results were inconsistent, almost certainly because the correct proportions of salt for physiological saline were then unknown, leaving Latta unable to gauge the proportions of potassium, sodium, bicarbonate, and chloride in the blood so as to prevent hemolysis and the destruction of red blood cells. Though a few of Latta's patients appear to have survived, most died after a temporary period of excitation like that described in his letter to the Lancet. The standard use of saline solutions (largely for recovery procedures) did not begin until 1902, when electrolyte balance and the mechanisms of hypovolemic shock were better understood.

Latta was based at the Leith Dispensary and Humane Society at 17 Broad Wynd, the forerunners of Leith Hospital.. Having suffered from tuberculosis for several years, he died in 1833. His death certificate was signed by Dr James Scarth Combe.^[11]