Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
99 Cards in this Set
- Front
- Back
|
key concept regarding the half-life of colloids vs. crystalloids
|
-although the intravascular half-life of crystalloids is 20-30 min, for most colloids its 3-6 hours
|
|
|
key concept regarding when to transfuse
|
-patients with a normal hematocrit should generally be transfused only after losses greater than 10-20% of their blood volume, with the exact point depending on the patient's medical condition and surgical procedure
|
|
|
key concept regarding the most severe transfusion reactions
|
-the most severe transfusion reactions are due to ABO incompatibility
-naturally acquired antibodies can react against transfused antigens, active compliment, and result in intravascular hemolysis |
|
|
key concept regarding acute hemolytic reactions in anesthetized patients
|
-in anesthetized patients an acute hemolytic reaction will manifest as a rise in temperature, unexplained tachycardia, hypotension, hemoglobinuria, and diffuse oozing in the surgical field
|
|
|
key concept regarding transfusion of leukocyte containing blood products
|
-giving leukocyte containing blood products appears to be immunosuppressive
|
|
|
key concept regarding transfusions in immunocompromised patients
|
-immunocompromised/immunosuppressed patients (eg. premature infants, organ transplant recipients) are especially susceptable to severe CMV infections from the transfusion, and such patients should recieve only CMV-negative units
|
|
|
key concept regarding the most common cause of bleeding following massive blood transfusion
|
-the most common cause of bleeding following massive blood transfusion is dilutional thrombocytopenia
|
|
|
key concept regarding hypocalcemia and blood transfusions
|
-clinically significant hypocalcemia, causing cardiac depression, does not occur in most normal patients unless the transfusion rate exceeds 1 U every 5 min
|
|
|
key concept regarding the most common acid-base abnormality following massive blood transfusion
|
-its post-op metabolic alkalosis
|
|
|
note about evaluating fluid status clinically
|
-intravascular volume can be assessed in many ways, including physical exam, labs, and more sophisticated hemodynamic monitoring techniques, but because all are indirect nonspecific measures of volume status, you cant rely on any one monitor, but rather all put together
|
|
|
when is physical exam most reliable when assessing fluid status?
|
-preoperatively
-many drugs used during anesthesia and the response to surgical stress unfortunately alter the physical signs of hypovolemia and make them unreliable |
|
|
physical exam clues to hypovolemia
|
-skin turgor
-hydration of mucous membranes -fullness of a peripheral pulse -the resting heart rate and BP -orthostatis changes from supine to sitting or standing -urinary flow rate |
|
|
physical exam signs after 5% body weight fluid loss
|
mucous membranes: dry
sensorium: normal orthostatis changes: none urinary flow rate: mildly decrease pulse: normal or increased blood pressure: normal |
|
|
physical exam signs after 10% body weight fluid loss
|
mucous membranes: very dry
sensorium: lethargic orthostatis changes: present urinary flow rate: decreased pulse: increased > 100 bpm blood pressure: mildly decreased with respiratory variation |
|
|
physical exam signs after 15% body weight fluid loss
|
mucous membranes: parched
sensorium: obtunded orthostatic changes: marked heart rate: inc >15 bpm blood pressure: dec > 10 mmHg urinary flow rate: markedly decreased pulse rate: markedly increased >120 blood pressure: decreased |
|
|
intraop signs of volume status
|
-fullness of peripheral pulses (radial or dorsalis pedis)
-urinary flow rate -response of blood pressure to PPV -the vasodilating or negative inotropic effects of anesthetics |
|
|
signs of hypervolemia (in pts with normal cardiac, renal, and hepatic function)
|
-pitting edema (presacral if bed ridden, pretibial if ambulatory)
-increased urinary flow |
|
|
late signs of hypervolemia
|
-tachycardia
-pulmonary crackles -wheezing -cyanosis -pink, frothy pulmonary secretions |
|
|
lab measures that can be used as surrogates of intravascular volume
|
-serial hematocrits
-arterial blood pH -urinary specific gravity or osmolality -urinary sodium or chloride concentration -serum sodium -serum Cr to BUN ratio |
|
|
what is the caviate with these measurements?
|
-they are indirect indices of volume and cant be relied upon intraoperatively because theyre affected by many other variables and the results are often delayed
|
|
|
lab signs of dehydration
|
-rising hematocrit
-progressive metabolic acidosis -urine specific gravity >1.010 -urine Na < 10 mEq/L -urine osmolality > 450 mOsm/kg -hypernatremia -BUN-Cr ratio > 10:1 |
|
|
what are the only reliable signs of volume overload?
|
-radiographic signs of increased pulmonary vascular and interstitial markings (Kerly B lines) or diffuse alveolar infiltrates
|
|
|
hemodynamic ways of monitoring volume status
|
include:
-CVP monitoring -PA catheters -TEE -vigeleo -etc |
|
|
when is CVP monitoring indicated?
|
-in patients with normal cardiac and pulmonary function when volume status is difficult to assess by other means or when major rapid alterations are expected
|
|
|
low CVP values (<5 mmHg)
|
-may be normal unless associated with other signs of hypovolemia
|
|
|
what is equally important to the absolute CVP number?
|
the response to fluid
|
|
|
what does a small elevation of CVP (1-2 mmHg) after a 250cc bolus indicate?
|
the need for more fluid
|
|
|
what about a large increase (> 5 mmHg)?
|
the need for a slower rate of administration and reevaluation of volume status
|
|
|
CVP readings > 12 mmHg
|
-indicate hypervolemia in the absense of RV dysfunction, inc intrathoracic pressure, or restrictive pericardial disease
|
|
|
when is PA pressure monitoring necessary?
|
-if CVP doesnt correlate with clinical assessment, or if the pt has primary or 2 RV dysfunction
|
|
|
what is primary RV dysfunction due to?
|
pulmonary disease
|
|
|
what is secondary pulmonary dysfunction due to?
|
LV failure
|
|
|
what does pulmonary artery occlusion pressure < 8mmHg indicate?
|
hypovolemia, in the presense of other clinical signs
|
|
|
PAOP < 15 mmHg?
|
-can indicate hypovolemia in patients with poor ventricular compliance
|
|
|
PAOP > 18 mmHg?
|
-generally implys LV overload
|
|
|
things that alter the normal relationship between PAOP and LVED volume?
|
-MV disease (especially stensosi)
-severe AS -LA myxoma or thrombus -increased thoracic and pulmonary airway pressures |
|
|
when should all PA measurements be made?
|
-at end expiration
|
|
|
what might IV fluid therapy consist of?
|
-crystalloids, colloids, or both
|
|
|
crystalloids
|
-aqueous solutions of low-molecular weight ions (salts) with or without glucose
|
|
|
colloids
|
-also have high molecular weight substances like proteins or large glucose polymers
|
|
|
distribution of crystalloids vs colloids
|
-colloids maintain plasma colloid oncotic pressure and for the most part stay intravascular
-crystalloids rapidly equilibrate with and distribute throughout the entire extracellular fluid space |
|
|
use of crystalloids vs. colloids
|
-controversial
-colloid proponents say that by maintaining plasma oncotic pressure they are more effective at restoring normal intravascular volume and CO -crystalloid proponents say they are equally effective when given in sufficient amounts |
|
|
what is one concern that has been raised about colloids?
|
-that they may enhance the formation of pulmonary edema in patients with increased pulmonary capillary permeability
|
|
|
what about these concerns?
|
-they have been unfounded because pulmonary interstitial oncotic pressure parallels that of plasma
|
|
|
generalizations which can be made about colloid and crystalloid
|
-crystalloids, when given in sufficient amounts, are just as effective as colloids at restoring intravascular volume
-replacing an intravascular volume defecit with crystalloids generally requires 3-4 x the volume as colloid -most surgical patients have an extravascular fluid defecit which is greater than the intravascular one -severe intravascular fluid defecits can be more rapidly corrected using colloids -the rapid administration of large amounts of crystalloids (>4-5 L) is more frequently associated with significant tissue edema (and some evidence suggests, though does not prove, that significant tissue edema can impair oxygen transport, tissue healing, and return of bowel function following major surgery |
|
|
in what patients should crystalloids be the initial resuscitation fluid?
|
-hemorrhagic and septic shock
-burn patients -patients with head injury to maintain CPP -patients undergoing plasmaphoresis and hepatic resection |
|
|
when should colloids then be added?
|
-if 3-4 L of crystalloid is given and the hemodynamic response is inadequate
|
|
|
types of crystalloid solutions
|
-NS
-1/2 NS -LR -D5W -D5NS -D5 1/2 NS -D5 1/4 NS -D5 LR -3%S -5%S -7.5% NaHCO3 -Plasmalyte |
|
|
contents of NS
|
tonicity (mOsm/L): Iso (308)
Na: 154 Cl: 154 |
|
|
contents of LR
|
tonicity (mOsm/L): Iso (273)
Na: 130 Cl: 109 K: 4 Ca: 3 Lactate: 28 |
|
|
contents of 1/2 NS
|
tonicity: hypo (154)
Na: 77 Cl: 77 |
|
|
contents of D5W
|
tonicity: hypo (253)
glucose: 50 g/L |
|
|
contents of D5 NS
|
tonicity: hyper (586)
Na: 154 Cl: 154 glucose: 50 g/L |
|
|
contents of D5LR
|
tonicity: hyper (525)
Na: 130 Cl: 109 K: 4 Ca: 3 glucose: 50 lactate: 28 |
|
|
contents of D5 1/2 NS
|
tonicity: hyper (432)
Na: 77 Cl: 77 glucose: 50 |
|
|
contents of D5 1/4 NS
|
tonicity: iso (355)
Na: 38.5 Cl: 38.5 glucose: 50 |
|
|
contents of 3% S
|
tonicity: hyper (1026)
Na: 513 Cl: 513 |
|
|
contents of 5% S
|
tonicity: hyper (1710)
Na: 855 Cl: 855 |
|
|
contents of 7.5% NaHCO3
|
tonicity: hyper (1786)
Na: 893 HCO3: 893 |
|
|
contents of plasmalyte
|
tonicity: iso (294)
Na: 140 Cl: 98 K: 5 Mg: 3 acetate: 27 gluconate: 23 |
|
|
how are crystalloid solutions chosen?
|
based on the type of fluid being replaced
|
|
|
what should be used for losses primarily involving water?
|
-hypotonic, or maintenance type solutions
|
|
|
losses of both water and electrolytes
|
-isotonic electrolyte solutions, or replacement solutions
|
|
|
when is glucose added to solutions?
|
-to maintain tonicity
-to prevent ketosis and hypoglycemia due to fasting |
|
|
who is at increased risk of developing hypoglycemia?
|
-children after 4-8 hour fasts
-women after extended fasts moreso than men |
|
|
what is most commonly used to replace intraop fluid losses?
|
-since most fluid lost intraop is isotonic, replacement-type solutions are used, most commonly LR
|
|
|
effects of LR
|
-slightly hypotonic, providing 100 ml of free water per L
-lows serum Na to 130 -has the least effect on extracellular fluid composition, and tends to be the most physiologic when large volumes are needed |
|
|
what happens to the lactate in LR?
|
its converted by the liver to bicarbonate
|
|
|
what happens when NS is given in large volumes?
|
-you get a dilutional hyperchloremic acidosis due to the high Na and Cl content (154 mEq each)
-the acidosis occurs because plasma bicar decreases as Cl increases |
|
|
when is NS the preferred solution?
|
-for hypochloremic metabolic acidosis
-to dilute PRBCs |
|
|
when is D5W used?
|
-to replace pure water defecits, and as a maintenance fluid for patients on Na restriction
|
|
|
when is hypertonic 3% saline used?
|
to treat severe symptomatic hyponatremia
|
|
|
use of 3-7.5% saline solutions
|
-some have advocated their use in the resuscitation of patients in hypovolemic shock
|
|
|
what is the problem with these solutions?
|
-they have to be given slowly because they readily cause hemolysis
|
|
|
advantage of colloids
|
-they have higher molecular weight, and therefore tend to remain intravascularly
-intravascular half-life is 3-6 hours, vs. 20-30 min for crystalloids |
|
|
what limits the use of colloids?
|
-the substantial cost and occasional complications
|
|
|
common indications for colloids:
|
-resuscitation for severe intravascular volume defecit (eg. hemorrhagic shock) before blood products arrive for transfusion
-fluid resuscitation in the presence of severe hypoalbuminemia or other conditions associated with loss of large amounts of proteins, like burns -often used with crystalloids when fluid needs exceed 3-4 L |
|
|
other note about colloids and burn patients
|
-they should be considered if the injury involves >30% of the BSA, or if > 3-4L crystalloid has been given over 18-24 h postinjury
|
|
|
what should be noted about the preparation of colloid solutions?
|
-they are generally prepared in NS and can therefore cause a hyperchloremic metabolic acidosis
|
|
|
derivation of colloids
|
-all are either derived from plasma proteins or synthetic glucose polymers
|
|
|
blood-derived colloids
|
-albumin
-plasma protein fraction |
|
|
albumin concentrations
|
comes in 5% and 25 %
|
|
|
plasma protein fraction concentrations
|
5%
|
|
|
how are both prepared?
|
-both are heated to 60C for at least 10 hrs to minimize transmission of hepatitis and other viral diseases
|
|
|
makeup of plasminate
|
-has albumin plus a and B globilins
|
|
|
complications with plasmanate
|
-can cause hypotension, which is related to an allergic reaction, possibly involving activators of prekallikrein
|
|
|
synthetic colloids
|
-dextrose starches
-gelatins |
|
|
gelatins
|
-are not available in the US because theyre associated with histamine-mediated allergic reactions
|
|
|
dextrose starches
|
-dextran
-hetastarch |
|
|
types of dextran
|
-dextran 70 (macrodex), MW 70,000
-dextran 40 (rheomacrodex), MW 40,000 |
|
|
effect of dextran 70 vs. 40
|
-dextran 70 is a better volume expander, but 40 shows better improvement of blood flow through the microcirculation due to decreased blood viscosity
|
|
|
side effects of dextrans
|
-antiplatelet effect
-infusions >20 ml/kg/day can interfere with blood typing, may prolong bleeding time (40), and are associated with renal failure -can be antigenic, and can cause mild and severe anaphylactoid and anaphylactic reactions |
|
|
how can the anaphylactic reactions be prevented?
|
-by giving dextran 1 prior to 40 or 70, with the idea being that it acts as a hapten and binds the circulating dextran antibodies
|
|
|
hetastarch
|
(hydroxyethyl starch)
-a 6% solution with an avg MW 450,000 |
|
|
metabolism of hetastarch
|
-small molecules are eliminated by the kidneys
-large molecules have to be broken down by amylase |
|
|
advantages of hetastarch
|
-good plasma expander
-less expensive than albumin -nonantigenic, and anaphylactoid reactions are rare -coags and bleeding times are not usually effected with use of 0.5-1 L |
|
|
hetastarch and kidney transplant patients
|
-whether these patients do worse when given it is controversial
|
|
|
hetastarch and CPB patients
|
-again, controversial
|
|
|
likely replacement for hetastarch
|
-pentastarch, a lower molecular weight solution
|
