III. GENERAL PRINCIPLES OF ANESTHESIA
FLUID VOLUME ASSESSMENT AND MANAGEMENT
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BLOOD TYPES | ANTIGEN | ANTIBODY |
A | A | B |
B | B | A |
AB | AB | NONE |
O | NONE | AB |
- Vitamin-K-dependent factors are II, VII, IX, and X and their formation is blocked with warfarin therapy. A prolonged PT is not affected by administering factor VIII.
- PRBCs and FFP must be ABO compatible. Although ABO-compatible platelet transfusions are preferred, it has been shown that platelets often give adequate hemostasis without ABO compatibility. Cryoprecipitate is not required to be ABO compatible.
- Factor VII has the shortest half-life among the clotting factors.
- Clotting factor VII becomes deficient first in severe liver failure, warfarin administration, and vitamin K deficiency.
- Transfusion related acute lung injury (TRALI) is the most common cause of death with blood administration.
- Acute hemolytic transfusion reaction may be the diagnosis if a patient develops dark red urine after receiving blood.
- The most common transfusion related infections:
- Cytomegalovirus (< 1%)
- Hepatitis C 1:600,000
- HIV 1:800,000
- West Nile virus 1:1,000,000+
- In anesthetized patients, an acute hemolytic reaction is manifested by:
- Hyperthermia
- Unexplained tachycardia
- Hypotension
- Hemoglobinuria
- Diffuse oozing in the surgical field.
- 22 degrees Celsius is the optimal temperature for storing platelets. In cold temperatures, platelets can undergo irreversible shape changes. This is why they are stored at room temperature. However, the pH drops because of platelet metabolism and bacterial growth is a concern. For these reasons, platelets can only be safely stored at this temperature for 5 days.
- Maximum allowable blood loss (MABL) = EBV x (HctS – HctI) / HctS
- PTT is prolonged by 1 liter of Hetastarch 6% because it lowers factor VIII:C levels by 50%.
- Calcium is the electrolyte in lactated Ringer’s that causes the reversal effect of anticoagulation when reconstituted with packed red blood cells.
- The maximum amount of Hetastarch one can receive in 24 hours is 20 mL/kg.
- Hetastarch 6% would expand the intravascular volume for 36 hours.
- Maximum daily dose is 20 mL/kg/day. Dextran 40 is used to enhance blood flow by thinning the blood (lowered blood viscosity). Doses higher than this can cause ABO incompatibility issues, coagulopathies, and possibly renal failure.
- Hetastarch can cause a transient increase in amylase.
- Fresh frozen plasma is thawed at 4OC and yields cryoprecipitate.
- Cryoprecipitate has the highest concentration of fibrinogen.
- Clotting is prevented in packed red blood cells because citrate binds with clotting factor IV.
ANEMIA | PACKED RED BLOOD CELLS |
THROMBOCYTOPENIA | PLATELETS |
FACTOR VIII DEFICIENCY | CRYOPRECIPITATE |
- FFP is transfused for microvascular bleeding, when the concentration of coagulation factors is deficient, to patients with an inherited coagulopathy, for the reversal of warfarin administration, and for a deficiency resulting from a dilutional coagulopathy.
- Stored blood has an average pH of 6.9 at the end of 5 weeks.
- The storage life of whole blood stored with citrate phosphate dextrose (CPD) is 3 weeks.
- The storage life of RBCs stored with Adsol is 6 weeks.
Bloodless Medicine (Including Blood Salvage Devices and Hemodilution Techniques)
- Withdrawing blood immediately before or just after the induction and its replacement with asanguinous (acellular) fluid is called acute normovolemic hemodilution. It will be transfused as needed.
- Unlike predonated autologous (self-donated) units of blood, blood withdrawn during acute normovolemic dilution does not undergo biochemical alterations associated with storage.
- Advantages of acute normovolemic hemodilution:
- Blood disease infections lower
- Transfusion reactions lower
- Immune system responses decrease
- Platelet function is maintained
- Normothermia
- Decreased requirement for allogenic (from other persons) blood transfusions
- Decreased viscosity may improve in tissue perfusion
- Hemodilution should be considered in any patient with an adequate hematocrit who is expected to lose more than 2 units of blood.
- Acute normovolemic hemodilution (ANH) cannot or should not be used in the patient with:
- Anemia
- Decreased renal function
- Significant coronary artery disease or heart disease
- Carotid artery disease
- Pulmonary disease
- Liver disease
- Inadequate vascular access
- Myocardial ischemia and cerebral hypoxia are the two major complications of acute normovolemic dilution.
- Acute normovolemic hemodilution (ANH) cannot be instituted if a patient has:
- FEV1/FVC ratio 0.6 after bronchodilator
- Coronary stents
- Alanine aminotransferase 1000 IU/L
- Perioperative blood salvage means recovering blood lost from the surgical field or wound drains and readministering it to the patient. In most cases, the salvaged material is “washed” and only the RBC component of blood is returned.
- Seven situations in which intraoperative blood salvage is commonly employed are:
- Cardiovascular surgical procedures
- Aortic reconstruction
- Spinal instrumentation
- Joint arthroplasty
- Liver transplantation
- Resection of arteriovenous malformations
- Occasionally in the management of trauma patient
- The RBCs are typically returned from the “cell saver” to the patient in volumes of 125 or 225 mL with a hematocrit of 45-65%. Expect the administration of allogenic blood because about 50% of RBCs are salvaged.
- Contraindications to intraoperative blood salvage are:
- Bacteria
- Cancer cells
- Urine
- Fecal matter
- Amniotic fluid
- Even after the washing process from intraoperative blood salvage, there is a possibility of infusing harmful wastes/products that can result in complications.
- The washing process removes essentially all clotting factors and most platelets and creates dilutional coagulopathy after intraoperative blood salvage.
- Coronary artery bypass grafting (CABG) and arteriovenous malformation resection both utilize cell savers.
Goal – Directed Fluid Management
- Normal Na+ concentration is 135-145 mEq/L. Hyponatremia occurs when the serum level is less than 135 mEq/L.
- Dose of [Na +] = Bodyweight X 0.6 X (desired [Na +] level-current [Na +] level in mEq/L)
- Neurologic symptoms are present at 120 mEq/L; cardiac at 100 mEq/L.
- Three percent NaCI is infused no faster than 1-2 mL/kg/hr. Correction too fast may lead to central pontine myelinolysis. When Na+ reaches 120 mEq/L, fluid restriction and diuretics guides the treatment plan.
WEIGHT | RATE |
First 10 kg | 4 mL/kg/hour |
Next 10 kg | 2 mL/kg/hour |
Each kg above 20 kg total | 1 mL/kg/hour |
AGE | BLOOD VOLUME |
Premature neonates | 95 mL/kg |
Full-term neonates | 85 mL/kg |
Infants | 80 mL/kg |
Adult males | 75 mL/kg |
Adult females | 65 mL/kg |
DEGREE OF TISSUE TRAUMA | ADDITIONAL FLUID REQUIREMENT |
Minimal | 0-2 mL/kg |
Moderate | 2-4 mL/kg |
Severe | 4-8 mL/kg |
Massive Transfusion Protocol
- 10 units of blood is considered a massive transfusion.
- Metabolic alkalosis is the most common acid-base imbalance after a massive transfusion of blood products.
- Transfusion of blood generally occurs after blood volumes losses greater than 10-20%.
- The most common cause of bleeding following massive blood transfusion is dilutional thrombocytopenia. Clinically significant hypocalcemia, causing cardiac depression, does not occur in most normal patients unless the transfusion rate exceeds 1 U every 5 min.
- Whenever massive transfusion therapy is employed, there is risk of:
- Citrate toxicity
- Metabolic alkalosis
- Coagulation abnormalities- dilutional thrombocytopenia
- Hypothermia
- Transfusion reactions
- Electrolyte disturbances- hypocalcemia, hyperkalemia, and hypernatremia