Lecture 5 IV Fluid and Blood in the Perioperative Period Flashcards
What percentatge of body weight in males is water? Females?
Total Body Water=60% of body weight in males and 55% of body weight in females. Up to 80% body weight in infants. Less in obese; fat contains little water
How much of total body water is intracellular?
two thirds
How much of total body water is extracellular?
one third
Of the extracellular water, how much is intravascular?
1/4-1/3
What is the approximate intravascular volume of a 60 kg female?
3.8 L
What is the approximate intravascular volume of a 70 kg male?
5 L
What factors can be used to preopratively assess fluid status?
mental status, h/o intake and output, blood pressure: supine and standing, heart rate, skin turgor, urinary output, serum BUN/osmolarity
Orthostatic hypotension is defined as….
systolic blood pressure decrease of >than 20 mm Hg from supine to standing (10% decrease normal 12-20% is borderline)
What percentage fluid deficit is indicated by orthostatic hypotension?
6-8%
In the presence of orthostatic hypotension, a failure of heart rate to increase may indicate….
autonomic dysfunction or antihypertensive drug therapy (beta-blockers)
What factors must you consider for perioperative fluid requirements?
maintenance fluid requirements, compensatory fluid bolus, NPO and other deficits: NG suction, bowel prep, Third Space losses, replacement of blood loss, special additional losses
How do you calculate maintenance fluid requirements?
1.5 ml/kg/hr for adults or 4:2:1 rule (4 ml/kg/hr for the 1st 10 kg of body weight, 2 mL/kg/hr for 2nd 10 kg, 1 mL/kg/hr for every kg thereafter)
How much is a customary compensatory fluid bolus early in anesthetic?
500 mL in 70 kg patient
How much fluid should be given to compensate for a bowel prep?
1 L
NPO deficit is calculated by…
number of hours NPO x maintenance fluid requirement (but usually start the hours at wake up time)
How do you calculate third space losses for superficial surgical trauma?
1 ml/kg/hr
How do you calculate third space losses for minimal surgical trauma (head and neck, hernia, knee surgery)?
2 ml/kg/hr
How do you calculate third space losses for moderate surgical trauma (hysterectomy, pelvic surgery)?
3 ml/kg/hr
How do you calculate third space losses for major surgical trauma (major intestinal surgery, major orthopedic procedures, open abdominal aortic aneurism repair)?
4 ml/kg/hr
How much blood loss can be ignored before replacing with fluids?
1.5-2 cc/kg
Blood loss after 1.5-2 cc/kg should be replaced with crystallod at a ratio of? With colloid?
3:1 crystalloid, 1:1 colloid
Hetastarch has what adverse effect?
mild coagulopathy when used over certain doses, rare allergic reactions. Can also elevate serum amylase
Hypertonic saline solutions may be used for…
cerebral edema. Draws water out of cells
How is oxygen delivery calculated?
oxygen delivery (DO2) = oxygen content (CaO2) x Cardiac Output (CO)
What is the main determinant of oxygen content in the blood?
hemoglobin
How is cardiac output calculated?
CO = HR x SV
How is oxygen content calculated?
Hgb x 1.39 x O2 Sat + PaO2 x 0.003. If PaO2=100, Hgb=15, and O2 sat 1, 0.3 ml O2/dl blood
What is the transfusion trigger?
Think oxygen delivery. Tolerance of acute anemia depends on: maintenance of intravascular volume, ability to increase cardiac output, increases in 2,3 DPG to deliver more of the carried oxygen to tissues.
What is cross matching blood?
major: donors erythrocytes incubated with recipients plasma, minor: donor’s plasma incubated with recipient’s erythrocytes. Blood unit is reserved for that patient, but can be re-matched for another patient
What is the difference between a type and screen and a type and cross?
Type and screen is a test done on the patient in which the recipient blood has been tested for ABO/Rh antigens and screened for common antiboides (not mixed with recipient blood). Blood is not reserved. In a type and cross, blood is reserved
What is type specific transfusion?
Only ABO-Rh is determined
If you don’t have time but must transfuse blood, what do you give?
O Rh negatve packed cells
What are the blood components as divided for transfusion?
packed red blood cells, platelet concentrate, fresh frozen plasma, cryoprecipitate, albumin, plasma protein fraction, leukocyte poor blood, factor VIII, antibody concentrates
1 unit of pRBC’s raises the Hgb….
1 gm/dL
Why can’t you use LR when transfusing pRBC?
LR has calcium which may cause clotting if mixed with pRBC
What is contained in fresh frozen plasma?
coagulation factors except platelets
What are the types of transfusion reactions?
febrile, allergic, hemolytic
What are the complications of blood therapy?
transfusion reactions, transmission of viral diseases, decreased 2,3 DPG, citrate (calcium binding, metabolism to bicarb), hypothermia, microaggregates, coagulation disorders (massive transfusion may lead to dilution of platelets and factor V and VIII)
How do you get autologous blood for transfusion prior to surgery?
1 unit donated every 7 days (up to 4 units) last unit donated >72 hrs prior to surgery
What are alternatives to blood products?
hematopoetic growth factors, isovolemic hemodilution, surgical technique, intra-operative blood salvage, coagulants, blood substitutes, hyperbaric oxygen therapy
