Hyponatremia and brain injury: historical and contemporary perspectives.

Hyponatremia is common in neurocritical care patients and is associated with significant morbidity and mortality. Despite decades of research into the syndrome of inappropriate antidiuretic hormone (SIADH) and cerebral salt wasting (CSW), their underlying pathophysiological mechanisms are still not fully understood. This paper reviews the history behind our understanding of hyponatremia in patients with neurologic injury, including the first reports of CSW and SIADH, and current and future challenges to diagnosis and management in this setting. Such challenges include distinguishing CSW, SIADH, and hypovolemic hyponatremia due to a normal pressure natriuresis from the administration of large volumes of fluids, and hyponatremia due to certain medications used in the neurocritical care population. Potential treatments for hyponatremia include mineralocorticoids and vasopressin 2 receptor antagonists, but further work is required to validate their usage. Ultimately, a greater understanding of the pathophysiological mechanisms underlining hyponatremia in neurocritical care patients remains our biggest obstacle to optimizing patient outcomes in this challenging population.

The flame photometer as engine of nephrology: a biography.

In the 1940s, the flame photometer made possible for the first time relatively simple and quick measurements of sodium and potassium in serum and urine. During World War II, it unexpectedly fell into the hands of John P. Peters of Yale University, who sought to understand water and electrolyte physiology and apply such knowledge to patient problems. Pupils and young associates of Peters would seed the early nephrology divisions and training programs in the United States; the flame photometer was essential to their work and that of their trainees, both Americans and international visitors. Hyponatremia and the syndrome of inappropriate antidiuretic hormone secretion became the "attribute" disorders of nephrologists. Invention of a microflame photometer fostered the revival of micropuncture and transport studies. In the 1960s, the flame photometer was linked to Leonard Skeggs' sequential automated analysis system, leading to enormous numbers of routine measurements of electrolytes. The growing number of nephrologists, then based mostly at teaching hospitals, thus found plentiful instances of sodium and potassium abnormalities to address. The autoanalyzer also catalyzed use of the anion gap, another emblem of nephrology in its early decades. Not only ideas and theories, but also the usually invisible machinery, enable the growth of a knowledge base and formation of a scientific discipline or medical specialty. Of course, the flame photometer did not itself shape the agenda of nephrology, but it allowed the most influential group of progenitors and their progeny to explore normal function and bring a strongly physiologic imperative to their daily work with patients.