Blood disorders Reduced Flashcards
What are some questions you might want to ask in regards to hematology?
- Have you ever had a blood problem?
- Anemia? Leukemia?
- Any clotting problems?
- Lots of bleeding from cuts, nosebleeds, surgery, dental work?
- Have you ever required a blood transfusion?
- Has a family member/blood relative ever had a serious bleeding condition or clotting problem?
What common medications would make you concerned in terms of possible hematological problems?
- Aspirin/NSAIDS
- Vitamin E,
- Ginseng, Gingko, Garlic, Saw Palmetto.
- How often, how much, and last dose?
Anemia Pathology
- Can be either Acute or Chronic
- Acute = Acute blood loss
- Chronic = Nutritional Hemolytic, Aplastic, Manifestation of another disease, Abnormal RBC structure (Sickle cell, Thalassemia)
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Disease state related to
- abnormal low concentration of hemoglobin (RBCs)
- Abnormal structure of hemoglobin
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Clinical manifestation of decreased oxygen carrying capacity and delivery
- Hemoglobin Defines oxygen carrying capacity
- Anemia decreases o2 carrying capacity
- Care must inclued treatment of the underlying disease as well as the state of anemia
- MUST avoid disruption of compensatory mecheanisms
Calculation of arterial blood oxygen content
CaO2 = (Hgb x 1.39) SaO2 + PaO2 (0.003)
- 1.39 = O2 bound to hemoglobin
- SaO2 = saturation of hemoglobin with O2
- PaO2 = arterial partial pressure of oxygen
- 0.003 = dissolved oxygen ml/mmHg/dl
- Normal O2 capacity = 16-20 mL/dL
Compensatory mechanisms for anemia
- Increase CO
- Increase 2,3-DPG
- Increased P50
- Increase plasma volume
- Decreased blood viscosity = increased CO
- Decreased SVR
- Blood shunting to organs with higher extraction ratios
- Kidneys release EPO
- RIGHTWARD shift in ox-hem disassociation curve
Oxyhemoglobin disassociation curve shifts to the right with:
Think of anything that increases metabolism → RBC will want to drop off Oxygen at the tissues
- Increased CO
- Acidosis = Decreased pH
- Increased 2-3 DPG
- Exercise
- Increased temeperature (sepsis)
- Hgb variants with decreased oxygen affinity (Sickle cell)
*
Oxyhemoglobin disassociation curve shifts to the left with:
Think anything that decreases metabolism →tissue does not need as much oxygen
- Decreased CO2
- Alkalosis = Increased pH
- Decreased 2/3 DPG
- Decreased temperature - hypothermia
- High oxygen affinity Hgb variants (Fetal Hgb)
(a leftward shift on someone that is dependent on a rightowrd shift may be a problem - we do this from hyperventilation and decreaseing temperature)
Changes that could interefere with oxygen delivery to the tissues
- Decreased CO
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LEFTWARD shft in oxy-heme disassociation curve
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Respiratory alkalosis
- hyperventilation/decreased PaCO2
- Hypothermia
- Abnormal Hgb such as fetal hemoglobin and carboxyhemoglobin
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Respiratory alkalosis
Anemia Basic Anesthetic management
- Know your pts preoperative Hgb and HCT
- anemia suspected if hemoglobin
- < 11.5 g/dl (females)
- < 12.5 g/dl (males)
- anemia suspected if hemoglobin
- Hgb and HCT are RELATIVE measuremants
Treating the underlying cause
Anesthesia management and considerations for chronic anemia
Goal = AVOID disruptions of compensatory mechhanisms that are aimed at maintinging O2 delivery to the tissues!
- Indentify and treat underlying disease if possible
- Maximize O2 delivery- High FiO2
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Avoid drug induced decreases in CO
- consider etomidate induction
- may want to use high opioid technique
- hydrate/avoid hypovolemia
- AVOID propofol, high amounts of IAs, STP
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AVOID leftward shifts of the oxyhemoglobin disassociation curve
- no hyperventilation/respiratory alkalosis
- no hypothermia
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Consder volitile anesthetics may be LESS soluble in plasma
- may have a faster induction, however, often OFFSET by the fact that these patients have and increased CO
Anemia and the decision to transfuse
Goal of transfusion therapy = Increase O2 carrying capacity and/or correct a coagulation disorder
- There is NO tranfusion trigger and the decision to transfuse is based on:
- The clinical judgment that the oxygen carrying capacity MUST be increased to prevent oxygenconsumtion(VO2) from being greater thanoxygendelivery (DO2)
- A drop in Hgb from 15 to 10 = 33% decrease in arterial oxygen content!
- it is also manifested by a RIGHT shift in the poxthemoglobin disassociation curve
2006 ASA guidelines regurding blood transfusion
- Rarely indicated if Hgb > 10 g/dL
- Almost ALWAYS indicated if Hgb < 6 g/dL
- If Hgb is 6-10: transfusion is based on the patients risk for complication and inadequate oxygenation
- Use of a transfusion trigger of Hgb is NOT RECOMMENDED
- Where apprropriate use of autologous blood, cell save or acute normovolemic hemodilution and measures to decrease blood loss (deliberate hypotension)
- Indications for transfusion are more liberal for autologous blood than blood from the blood bank
How do you know when to transfuse?
- You calculate the allowable blood loss for your surgical case
- ABL = EBV x (patients Hct - Allowable Hct)
patients Hct
- Know that:
- 1 unit of RBCs will increase Hct 3-5%;
- or it will increase Hgb ~1 g/dL
Nutritional anemias
- Iron deficiency
- Folic acid deficiency
- B12 deficiency
- Chronic illness (infections, cancer, RF, DM, AIDS, connective tissue disorders)
Iron deficiency anemia- RBCs are? Common causes in adults?
- Nutritional Anemia
- Ineffective erythropoesis and Microcytic RBCs
- In adults, depletion of iron stores is caused by chronic blood loss
- GI bleed
- menorrhagia
- cancer
- Most common form of nutritional anemia in infants and children
B12-def. anemia - RBCs are? May result in? Anesthesia considerations?
Macrocytic (Megaloblastic bone marrow morphology)
B12 deficiency may result in pernicious anemia
- Bilateral peripheral neuropathy
- Loss of proprioception/vibratory sensation in lower limbs
- Decreased deep tendon reflexes
- Unsteady gait
- Memory impairment/mental depression
Anesthesia considerations:
- Avoid regional blocks (neuropathys)
- Avoid N2O (binds B12)
- Maintain oxygenation
- Emergency correction for imminent surgery is RBC transfusion
Causes hemolytic anemias
Acquired Hemolytic Anemias
- Drug induced (High dose PCN, alpha- methyldopa)
- Disease/infection induced (malaria, epsteen Barr)
- Sensitization of RBCs (Maternal/fetal)
(particals released durring hemolysis can result in DIC and hypersplenism)
Hereditary hemolytic anemias
- Hereditary spherocytosis
- Paroxysmal nocturnal hemoglobinuria
- Glucose 6 Phospahete dihydrogenase deficiency
- Pyruvate Kinase Deficiency
Folic acid deficiency anemia- RBCs are? May result in? Anesthesia considerations?
Macrocytic (Megaloblastic bone marrow morphology)
Folic acid deficiency may result in penicious anemia
- Smooth tongue (difficult intubation)
- Hyperpigmentation
- Mental depression
- Peripheral edema
- Liver dysfunction
- Severely ill patient
Anesthesia considerations:
- Thorough airway assessment
- Have an alternative airway plan in place
- often have difficult airways d/t tongue texture!
Glucose-6-Phosphate dehydrogenase deficiency What is it? Who does it affect? What should you avoid?
Form of hemolytic anemia
- Most common enzymopathy; decreased G6PD activity leaves RBCs susceptible to damage by oxidation.
- Cell membranes have increased rigidity of membranes and there is accelrated RBC clearance
- Acute and chronic episodes.
- Most prevalent in: Blacks, Asians, Mediterranean populations
Anesestetic consideratons:
- AVOID: oxidative drugs (LAs, Benzos, Meth. Blue)
- AVOID: hypothermia, acidosis, hyperglycemia, infection
Peri-op risks and concerns for hemolytic anemia
Hemolytic anemia risks:
- Increased tissue hypoxia
- Increased infection risk if prior splenectomy
- Increased risk of venous thrombosis
To offset these risks preop planning should include:
- EPO given for 3 days pre-op
- Consider for transfusion if:
- Hgb acutely < 8 g/dL or
- Hgb chronically < 6 g/dL
- Adequate pre-op hydration and prophylactic RBC transfusions
- Caution with Methylene Blue - can increase hemolysis!!!
Sickle cell anemia patho
Cellular Pathology
- Inherited Single AA defect in the ß-globin chains
- Mutant S hemoglobin →valine substituted for a glutamic acid
- Hgb aggregates & forms polymers when there is low O2 concentrations
- Hemoglobin S has a shorter life span
Sickle cell trait vs. disease
- trait = heterozygus carriers (asymptomatic)
- disease = Homozygus (have the disease)
Explain a Sickle cell crisis
- Life threatening
- Acute vaso-occlusive crisis (Deoxygenation causes Hgb S to form insoluble globulin polymers)
- Ischemia and organ infarcts
- very painful
- Can cause stroke, renal failure, liver failure, splenic sequestration, PE and acute chest syndrome
Periop planning for Sickle cell anemia
- O2
- 12 hours hydration
- Pre-op exchange transfusons (HCT to 30% Hgb S <30%)
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Caution with pre-med
- avoid respiratory depression that can lead to acidosis
- USE Regional!
- AGGRESSIVE pain management
- Strict aseptic technique, must avoid infections
- Avoid tourniquets
AVOID ALL SITUATIONS LEADING TO
- Hypoxemia
- Hypovolemia
- Stasis