Potassium pathophysiology

FIGURE 13-1. Electrolyte transport in the airway epithelial cell. Ca, calcium cAMP, cyclic-3, 5 -adenosine monophosphate Cl, chloride Na, sodium K potassium. (From Milavetz G, Smith JJ. Cystic fibrosis. In DiPiro JT, Talbert RL, Yee GC, et al, (eds.) Pharmacotherapy A Pathophysiologic Approach. 6th ed. New York McGraw-Hill 2005 592, with permission.)... 

HYPOKALEMIA (SERUM POTASSIUM LESS THAN 3.5 MEQ/L) Pathophysiology... 

Robbins, J., KCNQ potassium channels physiology, pathophysiology, and pharmacology, Pharmacology and Therapeutics 2001, 90, 1-19. 

Pathophysiology In HF patients, the levels of aldosterone are elevated, even in the presence of ACE inhibitors or angiotensin-receptor blockers (34,35). Aldosterone has detrimental effects in HE such as causing potassium and magnesium loss, sodium retention, baroreceptor dysfunction, and myocardial fibrosis it also decreases the neuronal uptake... 

Pathophysiology Non-potassium-sparing diuretics are the treatment of choice to reduce fluid retention and dyspnea. Acting at specific sites of nephrons, they inhibit sodium and water reabsorption. Loop diuretics act on the loop of Henle, producing a maximal diuretic effect equivalent to 20% to 25% of the filtered sodium load and promoting the free water clearance. Currently available loop diuretics include furosemide, bumetanide, torsemide, and ethacrynic acid. Because of their potency, they are generally effective in patients with advanced renal insufficiency (glomerular filtration rates <25 ml/min) (49). 

Wright FS, Giebesch G. Regulation of potassium excretion. In the kidney physiology and pathophysiology. Seldin DW, Giebisch G (editors). Raven Press, New York 1992 p. 2206-2247. 

The volume to be infused and rate of delivery are only part of the therapeutic plan for fluid therapy, albeit the most important in acute resuscitation. The electrolyte and acid-base status of the horse should also be considered and fluids chosen to help to correct physiological imbalances. Unfortunately, it is not possible to predict electrolyte and acid-base disturbances accurately based on clinical signs. Seemingly similar clinical presentations may have a quite different pathophysiology (Brownlow Hutchins 1982, Svendsen et al 1979). The recent availability of relatively inexpensive, portable blood gas and electrolyte measuring equipment (Grosenbaugh et al 1998) has made determining the acid-base status possible in ambulatory equine practice and allows the field veterinarian to monitor and treat these disturbances. As stated earlier, in the absence of specific laboratory information, fluid therapy should probably be limited to isotonic polyionic crystalloid fluids, possibly with the addition of 10-20 mEq/1 potassium chloride in the maintenance phase. 

Brophy DF and Gehr TWB (2002) Disorders of potassium and magnesium homeostasis. In DiPiro JT et al. (eds.) Pharmacotherapy A Pathophysiologic Approach, 5th edn., pp. 989-993 New York McGraw-Hill. 

Future Direction. Potassium channels, especially the KCNQ family, are widely involved with the physiology and pathophysiology of the human body. Research into their biology will continue to blossom as more cloned KCNQ subunits are available, along with selective agents to modify their action. 

Frassetto, L., R.C. Morris, D.E. Sellmeyer, K. Todd, and A. Sebastian. Diet, Evolution and Aging The Pathophysiologic Effects of the Post-Agricultural Inversion of the Potassium-to-Sodium and Base-to-Chloride Ratios in the Human Diet. European Journal of Nutrition 40, no. 5 (October 2001) 200-213. 

Agarwal R, Afzalpurkar R, Fordtran JS. Pathophysiology of potassium absorption and secretion by the human intestine. Gastroenterology 1994 107 548-571. 

Desir GV (1995).The structure, regulation and pathophysiology of potassium channels. Curr Opin Nephrol Hypertens 4 402-405. 

Wright FS and Giebisch G (1992) Regulation of potassium excretion. In Seldin DW and Giebisch G, eds. The Kidney Physiology and Pathophysiology. 2nd edn. Raven Press New York, pp. 2209-2247. 

Sebastian, A., et al.. Estimation of the net acid load of the diet of ancestral preagri-cultural Homo sapiens and their hominid ancestors. Am. J. Clin. Nutr., 76,1308,2002. Frassetto, L., et al.. Diet, evolution and aging — the pathophysiologic effects of the post-agricultural inversion of the potassium-to-sodium and base-to-chloride ratios in the human diet, Eur. J. Nutr., 40, 200, 2001. 

---