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Coexisting conditions > Heme > Flashcards

Heme Flashcards

1
Q

What lab values define anemia?

men

women

pregnancy

A
  • men
    • Hgb <13 (nml = 13-17.5)
    • Hct <40% (nml = 42-52%)
  • women
    • Hgb <12 (nml = 12-15.5)
    • Hct <36% (nml = 37-47%
  • pregnancy hgb < 11
    • due to increase in plasma volume
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2
Q

How do you calculate arterial oxygen content?

normal?

A
  • CaO2 = (Hgb x 1.39)SaO2 + PaO2 (0.003)
    • 1.39 = O2 bound to hbg
    • SaO2 = satuation of hgb with O2
    • PaO2 = arterial pressure of O2
    • 0.003 = dissolved Oxygen
  • Normal is 16-20
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3
Q

How does the body compensate for anemia?

A
  • Decreased blood viscoscity
  • decreased SVR
  • increased CO
    • increased SV and HR
    • chronic severe anemia can lead to high output heart failure
  • Tissue redistribution of blood to organs with high extraction ratios
    • myocardium, brain, kidneys
    • causes pallor
  • Kidneys secrete EPO
  • Right shift on oxyhemoglobin curve
    • increased 2,3 DPG
    • fascilitates O2 release to tissues
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4
Q

Basic anesthetic management for acute and chronic anemias

A
  • Care must reflect underlying disease as well as anemia
  • avoid disruption of compensatory mechanisms that are helping get O2 delivered to tissues
    • avoid decreasing CO (avoid high gas)
    • avoid left shift (alkalosis, hypothermia)
  • Maximize O2 delivery
    • increase FiO2, transfuse PRBCs
  • If you expect blood loss, dilute first with fluids
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5
Q

What affects does anemia have on VA?

A
  • VA are less soluble in anemic patients
    • results in accelerated uptake, but this is negated by increased CO
  • no clinically detectable differences in the rate of induction
  • the problem with VA and anemic pts is the myocardial depression
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6
Q

How do you decide to transfuse an anemic patient?

A
  • Hgb level
  • risk of anemia vs risk of transfusion
  • presence of co-existing disease
  • magnitude of anticipated blood loss
  • Clinical judgement that the O2 carrying capacity must be increased
  • there is no longer a transfusion trigger–old “10/30” rule has no supportive evidence
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7
Q

What are the goals of transfusing?

A
  • to increase O2 carrying capacity
    • PRBCs
  • correct a coagulation disorder
    • FFP, platelets, DDAVP, cryo
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8
Q

How can the Hgb guide you in deciding to transfuse?

What specific co-ex disease process would you transfuse a little more aggressively?

A
  • Hgb > 10, rarely indicated
  • Hgb <6, almost always indicated
  • Hgb 6-10, based on pts risk for complications and inadequate oxygenation
  • Chronic anemia is generally well tolerated
  • CAD- transfuse more agressively because Hgb <7 can lead to myocardial ischemia
    • or Hct 28-30%
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9
Q

What are the risks of RBC transfusion?

A
  • Hep B, C, HIV, and bacterial infections
  • Longer ICU and hospital stays
  • increased rates of ventilator associated PNA and transfusion related acute lung injury
  • Hemolytic transfusion reactions
  • higher mortality rates
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10
Q

What are the guidelines for replacement of expected blood loss?

A
  • <15% of total blood volume = no replacement needed
  • 15-30% of total blood volume = replace with crystalloid
    • replace 3:1
  • >30% generally requires RBC
    • replace 1:1
  • >50% requires massive transfusion
    • RBC accompanied with FFP and platelets in ratio of 1:1:1
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11
Q

How do you calculate ABL?

estimated blood volume for men?

women?

A

ABL = (EBV x (pts Hct - allowable Hct))/pts Hct

**can replact Hgb in this equation

Men = 75 ml/kg

women = 65 ml/kg

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12
Q

1 unit PRBCs increases Hgb by ___ and Hct by ____.

1 unit PRBCs has a Hct of _____.

A

Hgb increased by 1 g/dl, Hct by 2-3%

70%

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13
Q

What are S/S of actute blood loss?

20%?

40%?

A
  • 20%
    • tachycardia
    • orthostatic hypotension
    • CVP change
  • 40%
    • tachycardia
    • hypotension
    • tachypnea
    • oliguria
    • acidosis
    • restlessness
    • diaphoresis
    • ECG ischemia
    • CVP change
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14
Q

How long does it take Hct to reach plateau after acute blood loss?

Decrease in Hct by 1% q24 hours can only mean ______

A
  • Hct will take 3 days to reach plateau due to intravascular fluid shifts
  • Decrease in Hct by 1% q 24 hours can only mean there is acute blood loss or intravascular hemolysis
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15
Q

Management of anesthesia with acute blood loss:

monitoring

induction

maintenance

A
  • Monitoring:
    • invasive? CVP, art, +/- PA
    • foley
  • Induction
    • Ketamine
    • etomidate- need good volume
  • Maintenance
    • may not tolerate VA
    • scopalomine, benzos, opioids all good choices
    • use vasopressors sparingly
    • keep warm
    • watch surgical field
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16
Q

What labs would you want to monitor with acute blood loss?

A
  • coags (PT, PTT, INR)
  • CBC
  • fibrinogen
  • Ca and K levels
  • ABGs
    • metabolic acidosis reflects hypovolemia and inadequate O2 delivery to tissues
  • *Watch surgical field for oozing
17
Q

What should you anticipate post op with acute blood loss?

A
  • may require post-op ventilation due to anticipated fluid shifts from resuscitation
  • Pulmonary edema
  • ARDS
18
Q

What is definition of massive transfusion?

A
  • transfusion > 10 units of RBC in 24 hour period
  • replacement of at least one blood volume in 24 hr period
  • replacement of 50% blood volume in 6 hr period
19
Q

What are complications associated with massive transfusion?

A
  • Hypothermia- use fluid warmer
  • volume overload
  • dilutional coagulopathy- no clotting factors in PRBCs
  • decreased 2,3 dpg- effects curve
  • hyperkalemia due to K leak
  • citrate toxicity- binds to Ca and causes hypocalcemia
  • blood contains glucose which is converted to lactat and can cause acidosis
20
Q

What disease processes can cause anemia?

A
  • renal disease
  • cancer
  • lupus
  • RA
  • DM
21
Q

What do you need to consider for anesthetic management of B12 deficiency?

A
  • airway evaluation and plan
    • thick large tongue
  • maintain adequate oxygenation
  • avoid N2O- depresses bone marrow and decreases B12
  • RBC transfusion for life-threatening anemia (usually unnecessary)
  • may want to avoid regional if paresthesia is present
22
Q

What is the anesthetic management of a pt with hereditary spherocytosis?

A
  • Depends on severity and if hemolysis is staple or in a period of exacerbation
  • avoid infections- higher risk due to splenomegaly and fewer macrophages ?
    • also higher risk of arterial and venous thromboembolism with no spleen
  • cardiac bypass and mechanical heart valves are especially disruptive, lead to excessive hemolysis
    • ask surgeon to do procedure off pump
      *
23
Q

Paroxysmal nocturnal hemoglobinuria anesthetic management

A
  • avoid respiratory depressants
  • avoid hypoxemia, hypo-perfusion and hypercarbia
    • use ETT, not LMA
  • maintain hydration and DVT prophylaxis
  • if transfusion required, use “washed” RBCs to decrease complement activation
24
Q

Anesthetic management of G6PD Deficiency

Many things you should avoid

Safe drugs?

A
  • Try to avoid hemolysis
    • avoid oxidative drugs:
      • NSAIDS, quinolones, sulfa
  • Avoid drugs that further depress G6PD deficiency
    • Iso, Sevo, diazepam, metroclopramide
  • Avoid Methylene blue- life threatening if administered
  • Avoid drugs that cause methemoglobinemia
    • lidocaine, prilocaine, benzocaine, silver nitrate
  • Avoid and aggressively treat conditions that cause oxidative stress:
    • hypothermia, acidosis, hyperglycemia, infections
  • Safe drugs:
    • codeine, midaz, propofol, fentanyl, ketamine, des
25
Q

What are the perioperative risks and concerns associataed with hemolytic anemias? (3)

What are the treatments?

A
  • Risks:
    • increased risk of tissue hypoxia
    • If previous splenectomy, increase risk of periop infection
    • increased risk of venous thrombosis d/t activation of coagulation cascade
  • Treatment:
    • erythropoietin is often prescribed for 3 days preoperatively
    • Acute drops below <8 g/dl and cronic <6 g/dl should be considered for transfusion
    • preop hydration and prohpylactic RBCs
    • Caution with methylene blue administration
26
Q

What sickle cell patients are at higher risk for perioperative complications?

Pt risk factors

surgical considerations

A
  • Risk factors:
    • advanced age
    • frequent severe sickling epidsodes
    • evidence of end-organ damage (low O2 saturation, elevated Cr, cardiac dysfunction, stroke)
    • concurrent infection- postpone if infected
  • Surgical considerations:
    • Low risk surgeries- extremity and minor procedures
    • moderate risk- inraabdominal
    • high risk- intracranial, intrathoracic, and hip replacement
27
Q

When would you consider a preop transfusion of a sickle cell patient?

What would your goals be?

A
  • Pt may benefit from conservative transfusions with high risk surgeries
    • goal to increase HCT to 30% without regard to ratio of sickle Hgb to normal Hgb
    • For major noncardiac surgeries transfuse goal of HbS <30%
    • Cardiopulmonary bipass surgeries goal of HbS <5% (require exchange transfusion)
28
Q

What should you avoid during the peri-op management of a sickle cell patient?

A
  • Hypoxemia/acidosis
  • hypovolemia
  • stasis
  • hypothermia
29
Q

How can you reduce the peri-op risks of Sickle cell disease?

Besides a conservative blood transfusion….

A
  • Supplemental O2- even when transporting
  • Pre0op hydration for 12 hrs before surgery (usually admitted night before)
  • Avoid resp dep with premeds
  • Regional is good for pain control
  • aggressive pain management
  • avoid infections
  • avoid tourniquets (but not contraindicated)
  • keep patient warm
  • maintain high CO
  • position to prevent stasis
30
Q

What are the perioperative risks and concerns for Thalassemia Major?

A
  • CHF common with severe anemia (might want echo)
  • Cardiac arrhythmias d/t heart failure
  • pt may not tolerate cardiac depression caused by anesthetic agents
  • pts are very sensitive to digitalis
  • hepatosplenomegaly
    • hypersplenism can result in thrombocytopenia and increased risk of infection
  • Coagulopathy- may not be able to use regional
  • Complications associated with high Fe- see other card

Coexisting conditions (34 decks)

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