Dehydration (Week 4) PDF

Dehydration Readings: Applied Pathophysiology – Chapter 8, p.210 Principles of Pathophysiology – Chapter 30, pp.670-672  Dehydration Dehydration is a form of fluid deficit, World Health Organization: The top 10 causes of death characterised by alteration in fluid and...

Dehydration Readings: Applied Pathophysiology – Chapter 8, p.210 Principles of Pathophysiology – Chapter 30, pp.670-672  Dehydration Dehydration is a form of fluid deficit, World Health Organization: The top 10 causes of death characterised by alteration in fluid and electrolyte balance: – Negative fluid balance – Sodium imbalance Dehydration secondary to diarrhoeal illness is the leading cause of infant and child mortality. – Water and electrolytes (sodium, chloride, potassium and bicarbonate) are lost through liquid stools, vomit, sweat, urine and breathing. – Children in developing countries are the most affected. https://www.who.int/news-room/fact-sheets/detail/the-top-10-causes-of-death  Dehydration Pathophysiology Water balance Dehydration affects all water compartments – ECF and ICF. Causes of dehydration: Decreased fluid intake Increased fluid output – Excessive diuresis e.g., diabetic hyperglycaemia – Gastrointestinal e.g., diarrhoea and vomiting – Insensible e.g., excessive sweating Fluid shift between compartments – Ascites – Capillary leakage e.g., burns, sepsis. Marieb & Hoehn (2023) Figure 26.7, p.1053. Craft et al. (2023) Figure 29.2, p.887. Dehydration Pathophysiology Classifications: based on blood sodium concentration. 1. Hyponatraemic – not proportional loss 2. Isonatraemic – volume depletion proportional loss 3. Hypernatraemic – not proportional loss Nath & Braun (2023). Table 8.3, p.215. Dehydration Clinical Manifestations Increased thirst Dry skin and mucous membranes Decreased or absent tears Change in vital signs – Increased respiratory rate – Decreased blood pressure – Weak pulse Increased body temperature Prolonged capillary refill time Weight loss Depressed fontanel Poor tissue turgor Dark sunken eyes Decreased level of consciousness Decreased (oliguria) or absent (anuria) urine output Patton & Thibodeau. (2014). Mosby’s Handbook of Anatomy & Physiology p.522. Dehydration Clinical Manifestations Severe dehydration – at least two of the following signs: – Lethargy/unconscious – Sunken eyes – Unable to drink, or drink poorly – Skin pinch goes back very slowly (≥ 2 seconds) Some dehydration – two or more of the following signs: – Restlessness, irritability – Sunken eyes – Drinks eagerly, thirsty Assessment of skin turgor. After squeezing the skin together, release should result in the ridges immediately returning to a normal appearance. Dehydration should be suspected when ridges remain after release. Nath & Braun (2023). Figure 8.8, p.209. Dehydration Diagnosis  History and physical examination are the basis of diagnosis Fluid intake: volume and type – hypertonic/hypotonic Fluid output: quantity and type – urine/stool/emesis/sweat  Severe cases: laboratory analyses Blood concentrations of:  Electrolytes – sodium, potassium, chloride  Bicarbonate – acid-base balance o Anion gap Poor perfusion may lead to renal damage, build-up of lactic acid (metabolic acidosis)  Blood urea nitrogen (BUN) increases due to impaired excretion  Serum creatinine increases due to renal blood flow  Specific gravity – urine osmolality is an indication of kidney ability to excrete/conserve water o Concentrated urine – more particles; higher specific gravity o Diluted urine – lower concentration of particles; lower specific gravity Treatment plan formulation based on data  Dehydration Treatment 1. Rehydration – fluid replacement 2. Correction of electrolyte imbalance Mild to moderate: oral administration – Fluid contains sodium, potassium, glucose. – Appropriate proportion to promote ready absorption from GI tract to circulation. – Frequent administration; small amounts. Severe: intravenous administration (Ringer’s lactate or isotonic saline) – Ringer’s lactate: sodium, chloride, potassium, calcium and lactate. – Mirror plasma concentration. – Large volume fluid replacement.  Volume replacement amount should be based on fluid deficit amount. Avoid rapid correction of hyponatraemia: associated with neurologic complications. Avoid rapid correction of hypernatraemia: cellular swelling, cell rupture.  Dehydration Treatment  Type of fluid depends on the clinical situation. Isotonic solution – same tonicity as plasma; distributes equally between intravascular, interstitial and intracellular spaces. Hypotonic solution – lower tonicity as plasma; fluid movement from intravascular spaces to interstitial and intracellular spaces. Hypertonic solution – higher tonicity as plasma; fluid movement from interstitial and intracellular spaces to intravascular spaces. Bullock & Hales (2023). Table 30.1, p.672. Clinical Snapshot Dehydration Bullock & Hales (2023). Figure 30.4, p.672.