tailieunhanh - Access: Acid-Base, Fluids, and Electrolytes - part 4

Khái niệm cơ bản của K + hằng định nội môi K + là sự chiếm ưu thế trong tế bào cation trong các Quy chế cơ thể của homeostasis + K là đạt được thông qua tế bào K + thay đổi và thận K + bài tiết • Rối loạn trong những kết quả cơ chế hằng định nội môi hoặc hạ kali máu hoặc tăng kali máu Hypo-và tăng kali máu | DISORDERS OF K BALANCE 135 TABLE 5-2 Basics of K Homeostasis K is the predominant intracellular cation in the body Regulation of K homeostasis is achieved through cellular K shifts and renal K excretion Disturbances in these homeostatic mechanisms result in either hypokalemia or hyperkalemia Hypo- and hyperkalemia disrupt action potential formation and promote various clinical symptoms and physical findings based on the following Neuromuscular dysfunction Inhibition of normal cell enzymatics Rapid recognition and treatment of these K disorders is required to avoid serious morbidity and mortality 136 DISORDERS OF K BALANCE K HOMEOSTASIS TABLE 5-3 Total Body K Stores K homeostasis involves maintenance of total body K stores within the normal range Total body K stores in an adult are between 3000 and 4000 mEq 50-60 mEq kg body weight Total body K content is also influenced by age and sex Compared with the young the elderly have 20 less total body K content Females have 25 less total body K than males K is readily absorbed from the GI tract and subsequently distributed in cells of muscle liver bone and red blood cells Maintenance of total body K stores within narrow limits is achieved by Regulation of K distribution between ECF and ICF Zero net balance between input and output K is an intracellular cation 98 of body K located in ICF Intracellular K concentration 145 mEq L Extracellular K concentration 4-5 mEq L Dietary K is excreted mainly in urine 90 and in feces 10 DISORDERS OF K BALANCE 137 TABLE 5-3 Continued The serum K concentration is an index of K balance It reasonably reflects total body K content In disease states serum K may not always reflect total body K stores Abbreviations GI gastrointestinal ECF extracellular fluid ICF intracellular fluid ROLE OF K IN THE RESTING MEMBRANE POTENTIAL TABLE 5-4 Role of K in Resting Membrane Potential Em The location of K and Na in their respective compartments is maintained by Na -K ATPase action in the cell membrane The .