Fluid Therapy and Replacement Flashcards
Indications upon physical examination of hypovolemia
Abnormal skin turgor
Dehydration of mucous membranes
*Thready peripheral pulses
*Increased resting HR and BP
Orthostatic HR and BP changes upon changing from supine to sitting or standing position
*Decreased urinary flow rate
*“Many of these symptoms will be masked during anesthesia. Of these symptoms these are most reliable intraoperatively”
Indications of hypervolemia in patients with normal cardiac, hepatic and renal function
Increased urinary flow rate
Pitting edema
Late signs: tachycardia, tachypnea, elevated jugular PP, pulmonary crackles, wheezing, cyanosis, and pink, frothy pulmonary secretions
Laboratory signs of dehydration
Rising hematocrit and hemoglobin
Progressive metabolic acidosis
Urinary specific gravity > 1.010
Urinary Na+ < 10mEq/L
Urinary osmolality > 450mOsm/L
Hypernatremia
BUN-to-creatine ration > 10:1
What is the difference between crystalloids and colloids?
- *Crystalloid solutions** are aqueous solns of ions (salts) with or without glucose
- Rapidly equilibriate with and distribute throughout the entire extracellular fluid space
- When given in sufficient amounts, are just as effective in restoring intravascular volume (3-4x more is needed usually)
- IV half life 20-30 min
- Large administrations (>4-5L) may contribute to tissue edema that can impair O2 transport
- *Colloid solutions** also contain high-molecular-weight substances such as proteins or large glucose polymers (help to maintain oncotic pressure better)
- Remain more intravascular
- More efficient in restoring normal intravascular volume and CO
What is the preferred solution for hypochloremic metabolic alkalosis and for diluting RBC prior to transfusion?
Normal saline
What is hyperchloremic metabolic acidosis?
Hyperchloremic acidosis is a form of metabolic acidosis associated with a normal anion gap, a decrease in plasma bicarbonate concentration, and an increase in plasma chloride concentration
Indications for use of colloids
- Fluid resuscitation in patients with severe intravascular fluid deficit (ex. hemorrhagic shock) prior to the arrival of blood for transfusion
- Fluid resuscitation presence of severe hypoalbuminemia or conditions associated with large protien losses such as burns
Blood derived colloids
Albumin (5% and 25%)
Plasma protein fraction (5%) - contains a and B-globulins in addition to albumin (may cause hypotensive allergic reaction)
Both are heated to 60 degrees for at least 10 h to minimize risk of transmitting hepatitis and other viral disease.
IV Half-life = 16-24 hours
Synthetic colloids
- Gelatins - associated with histamine-released allergic reactions, not available in USA
-
Dextrose starches (Dextran) - used as volume expander, reduces blood viscosity, von Wllebrand factor antigen, platelet adhesion, and RBC aggregation
- Contraindicated in acute kidney injury and those at risk of kidney disease
- Prevention of anaphylactic reactions by administration of Dextran I (Promit) prior to infusion
- Hetastarch - great plasma expander and less expensive than albumin, can decrease von Willebrand factor antigen levels, may prolong prothrombin time, potentially nephrotoxic in ederly
- Duration of volume expansion is 2-5 hours
Perioperative fluid therapy includes
Normal losses (maintenance requirements) Pre-existing fluid deficits Surgical wound losses including blood loss
Estimation of maintenance fluid requirements
4-2-1 Rule
For the first 10kg = 4mL/kg/hr
For the next 10kg = 2mL/kg/hr
For each kg above 20kg = 1mL/kg/hr
Fully soaked “4x4” is considered to hold?
10mL of blood
Fully soaked “lap” may hold?
100-150mL of blood
Below a hemoglobin concentration of ___g/dL, the resting cardiac output increases to maintain normal oxygen delivery
7
Average blood volumes of Neonates (Premature, Full-term), Infants, Adults (Men, Women) in mL/kg?
Neonates (Preterm) = 95mL/kg
Neonates (Full-term) = 85mL/kg
Infants = 80mL/kg
Adults (Men) = 75mL/kg
Adults (Women) = 65mL/kg
Estimating the amount of blood loss necessary for hematocrit to fall to 30%
- Estimate blood volume
- Estimate red blood cell volume (RBCV) at preoperative hematocrit (RBCVpreop)
- Estimate RBCV at hematocrit of 30% (RBCV30%)
- Calculate the RBCV lost when hematocrit is 30%
RBCVlost = RBCVpreop - RBCV30% - Allowable blood loss = RBCVlost x 3
An 85kg woman has a preoperative hematocrit of 35%. How much blood loss will decrease her hematocrit to 30%?
Estimated blood volume = 65mL/kg x 85kg = 5525mL
RBCV35% = 5525 x 35% = 1934mL
RBCV30% = 5525 x 30% = 1658mL
RBC loss at 30% = 1934 - 1658 = 276mL
Allowable blood loss = 3 x 276mL = 828mL
Diffusion is the random movement of molecules due to kinetic energy, what does the rate depend on?
PERMEABILITY OF SUBSTANCE
CONCENTRATION DIFFERENCES
PRESSURE DIFFERENCES
ELECTRICAL POTENTIAL
What is the difference between osmolality and osmolarity?
Osmolarity = #Osmoles/L
Osmolality = #Osmoles/kg of H2O
Normal human osmolality = 275-300mOsm/kg
Differences between hypo/iso/hypertonic solutions?
Body composition of fluids
Total body water (TBW) content in Adults (Males, Females), Newborns, and Obese patients?
What are differences between intracellular and extracellular fluid?
Intracellular
Comprises 2/3 total body water
Osmotic pressure determined by K+ (Na/K ATPase pump)
High protein content
Extracellular
Comprises 1/3 total body water
Osmotic pressure determined by Na+
Two compartments (Interstitial and intravascular or plasma)
Common hypotonic solutions, uses, and risks?
- 25%, 0.45% Normal Saline
- 5% Dextrose
Uses:
Hypernatremia
Diabetic ketoacidosis
Hyperosmolar hyperglycemia
Risks:
Increase ICP
Worsen hypotension
Hyperglycemia
Hemolysis
Common isotonic solutions, uses, and risks?
LR, 0.9% Normal saline
Normasol
Plasma-Lyte
Uses:
Replace extracellular volume
Risks:
Fluid overload
Caution in cardiac/renal patients
What is the most physiological solution, what are considerations you should be aware of?
Lactated Ringers
Lactate is converted to bicarbonate (metabolic alkalosis) Contains potassium (caution in renal patients, hyperkalemic, diabetics) Contains calcium (DONT USE WITH BLOOD PRODUCTS)
Consideration with Normal Saline?
Preferred use in renal patients, brain injury, BLOOD ADMINISTRATION
Contains no potassium
Greater than 4L can cause hyperchloremic metabolic acidosis
Common hypertonic solutions, uses, and risks?
D5 Normal Saline/Lactated Ringers
3% Normal Saline (Neuro ICU)
Mannitol (0.25g/kg) used for nephrectomy
Uses:
Plasma expanders
Reduce cerebral edema
Risks:
Hyperchloremic metabolic acidosis
Pulmonary edema
IV Infiltration
Cellular dehydration
Pulmonary artery catheter, uses and risks?
What is a central venous catheter and what is it used for?
What is pulmonary artery occlusive pressure (PAOP)?
Approximates LVEDP, normal is 8-12mmHg
<8 indicates hypovolemia (<15 in patients with poor ventricular compliance)
>18 may imply left ventricular overload
Can calculate CO with it and guide fluid therapy accordingly
SVV vs. PPV
What are pulse contour devices?
Esophogeal doppler uses
How can you estimate LV size?
What is third space fluid loss?
Surgical evaporative blood loss (open procedures)
What is the “classic” fluid replacement approach?
What is the “goal directed” fluid replacement approach?
What is advanced recovery after surgery (ARAS)?
Fluid considerations with kidney transplants and steep trendelenburg?
