Fluid, electrolytes and nutrition: physiological and clinical aspects

Abstract

Fluid and electrolyte balance is often poorly understood and inappropriate prescribing can cause increased post-operative morbidity and mortality. The efficiency of the physiological response to a salt or water deficit, developed through evolution, contrasts with the relatively inefficient mechanism for dealing with salt excess. Saline has a Na + :Cl -of 1 :1 and can produce hyperchloraemic acidosis, renal vasoconstriction and reduced glomerular filtration rate. In contrast, the more physiological Hartmann's solution with a Na + :Cl -of 1 . 18 :1 does not cause hyperchloraemia and Na excretion following infusion is more rapid. Salt and water overload causes not only peripheral and pulmonary oedema, but may also produce splanchnic oedema, resulting in ileus or acute intestinal failure. This overload may sometimes be an inevitable consequence of resuscitation, yet it may take 3 weeks to excrete this excess. It is important to avoid unnecessary additional overload by not prescribing excessive maintenance fluids after the need for resuscitation has passed. Most patients require 2-2 . 5 litres water and 60-100 mmol Na/d for maintenance in order to prevent a positive fluid balance. This requirement must not be confused with those for resuscitation of the hypovolaemic patient in whom the main aim of fluid therapy is repletion of the intravascular volume. Fluid and electrolyte balance is a vital component of the metabolic care of surgical and critically-ill patients, with important consequences for gastrointestinal function and hence nutrition. It is also of importance when prescribing artificial nutrition and should be given the same careful consideration as other nutritional and pharmacological needs.

A meta-analysis of randomised controlled trials of intravenous fluid therapy in major elective open abdominal surgery: getting the balance right

“…Splanchnic oedema can result in increased intra-abdominal pressure, ascites (42) and, in extreme cases, the abdominal compartment syndrome (43) . Intra-abdominal hypertension may lead to reduction in mesenteric blood flow, ileus or functional obstruction of anastomoses, increased gut permeability, intestinal failure and even anastomotic dehiscence (8) . In addition, hyperchloraemic acidosis, as a result of saline infusions, may reduce gastric blood flow and decrease gastric intramucosal pH in elderly surgical patients (44) .…”

“…or unbalanced solution (7)(8)(9)(10)(11) . Colloids are retained primarily in the intravascular compartment and produce less interstitial fluid overload than crystalloids (9) .…”

“…The goal of peri-operative fluid therapy should be to restore and maintain normal physiology, blood volume and organ function (8,16) by using an appropriate volume of the right fluid to achieve a state of homoeostasis. Both fluid overload and underhydration can detract from achieving this goal, resulting in adverse outcomes (3,17,18) .…”

“…75 litres (20,23,25,26) . The aim of ideal peri-operative fluid therapy should be maintenance of zero fluid balance with minimal weight gain or loss (8,18) . Until recently, peri-operative maintenance fluid therapy consisted of the provision of at least 3 litres of water and 154 mmol Na.…”

Exploring the Interrelationship Between Electrolytes, Anemia, and Glycosylated Hemoglobin (Hba1c) Levels in Type 2 Diabetics

“…The electrolytes in serum include sodium, potassium, chloride, and bicarbonate [15]. Electrolyte disorders in diabetes are usually multifactorial in nature.…”