Fluid Resuscitation study guide previews.

The Passive Leg Raise (PLR) is a reversible autotransfusion maneuver that mobilizes blood from the lower extremities and splanchnic circulation to the central circulation. It simulates a fluid bolus (~300-500 mL) to test for fluid responsiveness in real time - without giving actual IV fluids.

This mimics the effect of a fluid challenge. Transition to supine while raising both legs to ~45. This causes a transient shift of ~300-500 mL of venous blood centrally.

Albumin introduces the clinical pattern, physiology, and bedside decisions that matter for emergency and critical care practice.

D5W introduces the clinical pattern, physiology, and bedside decisions that matter for emergency and critical care practice.

What it is includes pressure in the thoracic vena cava near RA leading to historically used as preload/volume marker. How to use include CVP measured via central line and Traditionally “CVP < 8 mmHg” interpreted as hypovolemia. Confounded by includes intrathoracic pressure, PEEP, RV dysfunction, intra-abdominal pressure. What it is includes respiratory variation in arterial pulse pressure in mechanically ventilated patients. How to use include Requires arterial line, controlled ventilation, sinus rhythm, PPV ≥ 13% leading to fluid responsive likely, PPV ≤ 9% leading to unlikely, and % = gray zone.

Not valid with includes arrhythmias, spontaneous breaths, low Vt (< 8 mL/kg), high PEEP, RV dysfunction. What it is includes reversible, “autotransfusion” of ~300 mL by elevating legs to 45. How to use include Measure stroke volume/cardiac output surrogate (echo VTI, pulse contour, NICOM) and PLR-induced increased SV ≥ 10-15% = fluid responsive. Not reliable in high intra-abdominal pressure or if patient cannot tolerate leg elevation. What it is includes bedside US of IVC diameter & respiratory variation as a volume estimate.

How to use include Collapsibility > 50% suggests low volume, Distensibility > 18% suggests fluid responsive, and Dilated, non-collapsing IVC suggests high RA pressure.

Understanding fluid compartments is foundational for fluid management. Total body water accounts for ~60% of adult body weight (higher in infants, lower in the elderly). Body fluids are distributed across intracellular, extracellular, intravascular, and interstitial spaces. Different intravenous fluid choices (D5W, normal saline, lactated Ringer’s, albumin) distribute variably across these compartments, influencing clinical use.

Total body water ~60% of adult body weight (range 45-75% depending on age).• Intracellular fluid (ICF): ~66% of total body water.• Extracellular fluid (ECF): ~33% of total body water, further divided into: • Intravascular (plasma): ~8% of total. • Extravascular (interstitial): ~22% of total.

Organ water content examples includes brain: 85%• Lungs: 80%• Kidneys: 80%• Heart: 75%• Muscle: 70%• Skin: 70%• Liver: 70%• Bone: 20%. Intracellular includes inside cells, ~2/3 of total body fluid.• Extracellular: Outside cells, ~1/3 of total body fluid. • Intravascular: Plasma volume, ~8%. • Interstitial (extravascular): Fluid between cells, ~22%. Fluid movement between compartments depends on permeability of membranes and the tonicity/osmolarity of infused solutions:• Water moves freely across compartments to equalize solute concentration.• Cell membranes and capillary walls regulate movement of solutes.

Intravenous fluids are categorized based on tonicity relative to plasma: hypotonic, isotonic, or hypertonic. Tonicity determines how water moves across cell membranes, influencing whether cells swell, remain stable, or shrink. This understanding is essential for safe and effective fluid resuscitation and maintenance therapy.

Tonicity describes how a solution influences water movement across a cell membrane.• Water moves from areas of low solute concentration (low tonicity) to high solute concentration (high tonicity).• Goal: equilibrium where intracellular and extracellular solute concentrations are equal.

Hypotonic Isotonic Hypertonic is lower solute concentration than intracellular fluid leading to water shifts into cells leading to cell swelling.Examples:• D5W (after glucose metabolism, leaves free water)• 0.45% normal saline (half‑NS)Distribution:• Only ~8% remains intravascular• Majority distributes intracellularly.

Lactated Ringers introduces the clinical pattern, physiology, and bedside decisions that matter for emergency and critical care practice.

Normal Saline introduces the clinical pattern, physiology, and bedside decisions that matter for emergency and critical care practice.

Plasma-Lyte introduces the clinical pattern, physiology, and bedside decisions that matter for emergency and critical care practice.

This is a foundational concept for managing shock at the bedside. Mean Systemic Filling Pressure (MSFP) leading to the upstream pressure driving venous return. Veins are highly compliant (hold ~70% of blood volume).

Two major forces determine how fluid shifts across blood vessels Hydrostatic Pressure - Pressure of fluid inside the vessel pushing fluid outward.• Oncotic Pressure - Pressure generated by solute/proteins that pulls fluid inward. Intravenous Fluid Basics: Crystalloid Versus Colloid Explained is iV solutions with small, water-soluble molecules such as electrolytes and glucose. Examples includes normal Saline (0.9%), Half Normal Saline (0.45%), Lactated Ringers (LR), Plasmalyte, D5W. Composition includes primarily electrolytes (Na⁺, Cl⁻, K⁺, Ca²⁺, Mg²⁺), glucose, or organic anions (e.g., lactate, acetate).

Distribution includes equilibrates across the entire extracellular space (intravascular + extravascular). Retention includes ~25% of isotonic crystalloid remains intravascular; ~75% shifts to extravascular space. Intravenous Fluid Basics: Crystalloid Versus Colloid Explained is iV solutions with larger molecules (proteins/starches) that exert oncotic pressure. Examples includes albumin (most common), historical HES (hydroxyethyl starch, now avoided), gelatin-based solutions. Composition includes large molecules (proteins like albumin) harvested from human plasma or synthetic starches/gelatins. Distribution includes mostly retained in the intravascular space due to oncotic effect.

Retention includes ~100% of colloid volume stays intravascular initially; leakage occurs over time. Risks includes allergic reactions (rare), higher cost, no proven mortality benefit in most settings. Total body water ≈ 60% of adult weight.• Intracellular: ~66% of body water.• Extracellular: ~33% of body water. - Intravascular: ~25% of extracellular (~8% total). - Extravascular: ~75% of extracellular (~25% total).