Heme Flashcards
(30 cards)
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
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
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
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
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
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
7
Q
What are the goals of transfusing?
A
- to increase O2 carrying capacity
- PRBCs
- correct a coagulation disorder
- FFP, platelets, DDAVP, cryo
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%
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
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
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
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%
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
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
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
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
*
- 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 oxidative drugs:
- 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
What are the perioperative risks and concerns associataed with hemolytic anemias? (3)
What are the treatments?
* 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
What sickle cell patients are at higher risk for perioperative complications?
Pt risk factors
surgical considerations
* 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
When would you consider a preop transfusion of a sickle cell patient?
What would your goals be?
* 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
What should you avoid during the peri-op management of a sickle cell patient?
* Hypoxemia/acidosis
* hypovolemia
* stasis
* hypothermia
29
How can you reduce the peri-op risks of Sickle cell disease?
Besides a conservative blood transfusion....
* 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
What are the perioperative risks and concerns for Thalassemia Major?
* 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
