IV Fluid Therapy Part 2

Indications for Intravenous (IV) Fluid Therapy

  • Patients in Shock or Hypovolemia

    • Definition: Shock/hypovolemia is defined as a fluid deficit specifically within the vasculature.
    • Urgency: Fluid administration must be rapid for patients in shock.
    • Critical Warning: Delaying the treatment of shock causes death.

  • Dehydrated Patients

    • Definition: Dehydration is a fluid deficit of the interstitium and intracellular spaces.
    • Progression: Severe dehydration has the potential to lead to hypovolemia.
    • Administration Rate: Unlike shock patients, dehydrated patients may receive fluids more slowly.

  • Patients with Electrolyte Dyscrasias

    • Fluid therapy is indicated to correct imbalances in electrolytes.

  • Patients with Metabolic Acid-Base Disorders

    • Fluid therapy is used to address metabolic disturbances in acid-base status.
    • Note on Respiratory Disorders: Respiratory acid-base disorders do not correct with fluid therapy.

  • Anesthetized Patients

    • Fluid therapy is a standard requirement for patients undergoing anesthesia to maintain cardiovascular stability.

Contraindications and Exclusions for IV Fluid Therapy

  • Congestive Heart Failure (CHF)

    • Do not administer IV fluids to patients with active CHF.
    • This contraindication extends to patients with a known history of most types of CHF.

  • Fluid-Overloaded Patients

    • IV fluids should be withheld from patients already exhibiting signs of fluid overload.

  • Maintenance of Self-Hydration

    • Patients that are capable of maintaining their own hydration and blood volume do not require IV fluid intervention.

Clinical Assessment of Hydration Status

  • Physical Examination Parameters

    • Mucous Membranes (mm): Evaluate for moisture and color.
    • Skin Turgor: Test via "skin tenting" to assess the elasticity and hydration of the skin.
    • Ocular Examination: Examine the eyes for signs of recession or dryness.
    • Pulses: Assess the strength and quality of peripheral pulses.
    • Mentation: Evaluate the patient's mental status and responsiveness.

  • Continuous Monitoring Tools

    • Blood Pressure (#1): Used to continuously assess cardiovascular parameters.
    • Electrocardiogram (ECG) (#2): Used alongside blood pressure for real-time monitoring of cardiac rhythm and stability.

Confounding Factors in Hydration Assessment

  • Geriatric or Emaciated Patients

    • These patients possess less subcutaneous (SQ) collagen.
    • Clinical Impact: This state may result in an artifactually prolonged skin tent, which can be misidentified as dehydration.

  • Ptyalism (Excessive Salivation)

    • Clinical Impact: Excessive drooling may give the false impression of moist oral mucous membranes even if the patient is dehydrated.
    • Clinical Pearl: Use vulvar or preputial mucous membranes instead to get a more accurate assessment.

  • Rapid Development of Effusion

    • Clinical Impact: A patient may present with a falsely normal skin turgor because fluid has not yet shifted from the interstitium into other compartments.

Clinical Assessment of Blood Volume and Shock

  • Heart Rate (HR) Changes

    • Early/Compensatory Shock: The heart rate increases as the body attempts to compensate for reduced volume.
    • Late/Decompensatory Shock: The heart rate decreases as compensatory mechanisms fail.
    • Species Specificity: It is critical to remember that cats clinically skip the compensatory stage of shock.

  • Blood Pressure (BP) Changes

    • Blood pressure decreases later in the progression of shock.
    • Clinical Action: Address any blood pressure abnormalities promptly to avoid progression to irreversible shock and death.

Advanced Cardiovascular and Hemodynamic Monitoring

  • Thoracic Radiography

    • Used to assess cardiac size and the size of the vena cava.
    • Specific Example (Hypertrophic Cardiomyopathy): In cats with hypertrophic cardiomyopathy (HCM), radiographs may show bi-atrial enlargement and the classic "valentine" heart shape.

  • Ultrasonography

    • Left Atrial Size: Measured as a ratio compared to the aorta (LA:Ao). The normal ratio is textLA:Ao=1−1.5\\text{LA:Ao} = 1 - 1.5.
    • Left Ventricular Volume: Assessed specifically in diastole.
    • Caudal Vena Cava: Evaluated for diameter and collapsibility.

  • Complex Hemodynamic Metrics

    • Cardiac output/index.
    • Pulse pressure variability.

Identification and Risk Factors for Fluid Overload

  • Clinical Indicators of Fluid Overload

    • Development of new effusion.
    • New or progressive pulmonary edema.
    • Peripheral edema.
    • Chemosis: Swelling of the conjunctiva.
    • Nasal Discharge: May be present (+/−+/-).

  • Visual Case Study: Patient on Ventilator

    • A patient with fluid overload showed significant muzzle, glossal, and periorbital edema.
    • Eight hours after stopping IV fluids and administering a single dose of furosemide (a loop diuretic\text{a loop diuretic}), there was a marked reduction in edema in these areas.

  • High-Risk Patient Categories

    • Oligoanuric Patients: Patients producing little to no urine.
    • Unmanaged Fluid Rates: Patients receiving fluid therapy without strict monitoring or rate adjustments.
    • Cardiac Disease History:
      • Patients with a history of Congestive Heart Failure (CHF).
      • Dogs and cats with dilated cardiomyopathy (DCM).
      • Cats with hypertrophic cardiomyopathy (HCM).

  • Preventative Monitoring

    • Weighing patients frequently is a primary method to catch fluid overload in its early stages.