Fluid Imbalance - Pharm 343.01 Course Overview PDF

Fluid (Water) Balance Total body water (TBW) represents 45-60% of total body weight Distribution into two (three?) compartments: H2 O...

Fluid (Water) Balance Total body water (TBW) represents 45-60% of total body weight Distribution into two (three?) compartments: H2 O 11 Source: www.peterloewen.com (Sodium & Water Assessment & Therapeutics)  Normal Fluid Balance Osmotic pressure maintains distribution of fluids in the compartments – Concentration of dissolved ions (electrolytes), proteins, and other large molecules – Water moves freely across cell membranes to maintain osmotic equilibrium WA TE WA R TE R Hypotonic Isotonic Hypertonic Solution Solution Solution 12  Normal Fluid Balance Osmotic pressure maintains distribution of fluids in the compartments – Concentration of dissolved ions (electrolytes), proteins, and other large molecules – Water moves freely across cell membranes to maintain osmotic equilibrium Intracellular fluid (ICF) volume is critical for normal cell function – e.g., alterations to ICF volume in the brain can result in significant dysfunction (confusion ⟹ death) Extracellular fluid (ECF) volume is essential for tissue perfusion (delivery of oxygen & nutrients; removal of metabolic waste products) 13  Conditions Related to Fluid Status When assessing a patient’s clinical fluid status, we are mostly concerned with the extracellular fluid volume (interstitial water and intravascular water [serum/plasma/blood volume]) Blood volume and serum osmolality are tightly regulated (homeostasis) Homeostasis can be disrupted by a variety of acute and chronic diseases as well as the intended and unintended effects of drug therapy 14  Signs & Symptoms of Dehydration Dry mucous membranes Skin tenting (poor skin turgor) ↓Urine output Postural changes: (lying ⟹ standing) dizziness, HR↑, SBP↓ Cool extremities ↓Capillary refill ↓Cognitive function Sunken eyes (orbital depression) 18  Signs & Symptoms of Dehydration in an Infant or Young Child Dry mouth and tongue Lack of tears when crying No wet diaper for 3 hours Sunken eyes, cheeks Sunken soft spot on top of skull Listlessness or irritability (change from normal behaviour) Send for medical attention immediately. Jane’s youngest child was also recently sick – have they recovered or need medical attention? 19  Dehydration Management Typical maintenance is 2000-3000 mL/day – 6-8 x 250 mL glasses of water per day If the patient is mildly dehydrated, encourage them to drink (water, WHO-ORS, water+salt, sports drink) Depending on severity, referral for medical attention may be necessary along with intravenous fluid replacement Distribution of 1000 mL* Tonicity ICF ECF D5W (5% Dextrose†) Hypotonic 666 mL 333 mL 0.45% NaCl (half normal saline) Hypotonic 333 mL 666 mL Lactated Ringer’s Isotonic 30 mL 970 mL 0.9% NaCl (normal saline) Isotonic 0 1000 mL 3% NaCl (hypertonic saline) Hypertonic -2000 mL 3000 mL †Dextrose is an ineffective osmole 20 *Source: www.peterloewen.com (Sodium & Water Assessment & Therapeutics)  Signs & Symptoms of Edema Excess fluid volume in the extracellular compartment – Usually caused by heart, kidney, or liver failure – Also occurs in pregnancy and malnutrition First sign is often swelling in the feet, ankles, and lower legs ⟹ described as pitting edema http://www.med-health.net/images/10437462/image001.jpg 22 https://www.uptodate.com/contents/heart-failure-the-basics/print  Signs & Symptoms of Edema Pulmonary edema – Increase in respiratory rate – Shortness of breath sensation – Crackles (rales) present on auscultation Weight gain Increased jugular venous pressure Positive hepatojugular reflux: firm pressure over the liver temporarily increases venous return to the heart – https://www.youtube.com/watch?v=JxyECMTEmmc 23  Management Correct the underlying cause – Heart failure – Sodium restriction (1,000 to 2,000 mg/day) Medications: diuretics (↑ renal sodium excretion) – Loop diuretics (furosemide, ethacrynic acid) – Thiazide diuretics (hydrochlorothiazide, chlorthalidone, metolazone) – Potassium sparing diuretics (triamterene, amiloride, spironolactone) 24