Fluid Management Flashcards
The water content in the human body by weight?
60%
Into which 2 main compartments is the water distributed into?
Intracellular space Extracellular space (consisting of interstitial fluid and plasma fluid)
Water distribution between compartments?
Intracellular space: 65% of total body water (TBW)
Extracellular space: 35% TBW
(Interstitial = 27,5%)
(Plasma/intravascular = 7,5%)
How is TBW normally governed/regulated?
By regulating the ECF
Changes in the ICF passively follow changes in the ECF
Fluid management physiology (heart)?
Drop in plasma volume (decreased filling pressure of the heart)
- Increased ADH production from posterior pituitary (regulated by baroreceptors) = stimulates water intake (thirst) and re-absorption of water in the kidney
- Decreased ANP (atrial natriuretic peptide) = reduced sodium excretion by the kidney (therefore sodium retention)
Increases in plasma volume will thus result in the reverse, so a decrease in ADH production and an increased right atrial stretch thus increased ANP production (increased sodium excretion in the kidneys)
Fluid management physiology (kidneys)?
Juxta-glomerular apparatus (JGA) senses decreases in arterial filling pressure
Releases Renin
Renin cleaves angiotensinogen = angiotensin I
Angiotensin I = angiotensin II by ACE
Angiotensin II: potent vasoconstrictor and releases aldosterone (Na retention and K excretion from adrenal cortex
A fall in renal perfusion pressure redistributes renal blood flow from outer cortex to inner cortex (to enhance increased Na and water retention by the long loops of Henle)
What is the circulatory/neural response to stress?
Sympathetic stimulation
Central catechloamine release:
- Adrenaline: B-agonist (increase in CO with vasodilation of vessels supplying heart and skeletal muscles)
- Noradrenaline: Alpha-agonist effect (vasoconstriction in all organs except brain, heart and skeletal muscle = blood redistributed away from kidney, gut and liver)
Concurrent parasympathetic inhibition
Increase in HR
Maintenance of BP in face of reduced circulating blood volume
What is the metabolic/humeral/hormonal response to stress?
Anti-insulin hormone release:
- Catechloamine release
- Glucocorticoid release
- Thyroid hormone release
- Growth hormone release
Increase release of glucose from the liver by glycogen breakdown and gluconeogenesis
Insulin suppression limits glucose to flight/fight organs only, which can readily use glucose in the absence of insulin
Other organs become fat adapted (over a few days) and rely on FFA and ketones for their energy
What are the consequences of the stress response?
Maximal sodium and water retention
Dilutional hyponatraemia
Hypokalaemia (and subsequent metabolic acidosis)
Diminished renal blood flow with risk of renal failure
Hyperglycaemia
Sharp fall in intravascular pressure resulting in net uptake of extravascular fluid into the intravascular space resulting in haemodilution
Coagulation enhanced
What happens if a state of shock persists?
Cytokine release
Loss of capillary integrity
Failure of endothelial barrier to prevent extrusion of proteins
Fluid leak resulting in loss of plasma protein from intravascular space into the extravascular space
Increased oncotic pressure in extracellular fluid with tissue oedema
Worsening of hypovolaemic state
Decreased organ perusion pressure and multiple organ failure
What are the objectives of fluid therapy in shock?
Early and complete restoration of tissue blood flow and oxygen supplies
Reduce biochemical disturbances
Preservation of organ function (NB gut and kidney)
Avoidance of transfusion complications
Types of IV fluids (list)?
Crystalloids
Synthetic colloids
Blood
List the different crystalloids?
Isotonic fluids (suitable for intravascular resuscitation):
- Normal 0,9% saline
- Ringers Lactate Solution
- Modified Ringers Lactate (Plasmalyte L)
Hypotonic fluids (suitable for maintenance, replacement and rehydration):
- Half-normal saline
- Rehydration fluid
- General maintenance solution(most commonly prescribed)
- Maintelye solution
List the different synthetic colloids?
Gelatins (Gelofusine, Haemaccel)
Dextrans (Macrodex, Rheomacrodex)
Starches (Voluven, Venofundin)
Benefit of synthetic colloids over crystalloids?
Gelatinous particles do not dissolve readily, nor do they settle under gravity
Colloids have a high capacity for binding with water and other substances
They do not pass easily through cell membranes
Faster plasma volume expansion and better initial resuscitation than crystalloids
Improve “rheology” of plasma and improving organ blood flow
Risks of synthetic colloid use?
Do not resuscitate intracellular or interstitial fluid volume, and may diminish renal function as a consequence if used as a sole resuscitation fluid
Some degree of allergic risk
Interfere with coagulation to some degree
Type of blood products (list)?
Whole blood
Packed RBC’s (red cell concentrate)
Fresh frozen plasma (FFP)
Properties of whole blood products?
Screened for HepB, HepC, HIV and syphilis
Used mainly as raw material for producing numerous blood components
Approx volume: 550ml
Haematrocrit: 35%
Preservative: CPD-A (citrate, phosphate, dextrose, adenine)
Shelf life: 35 days at 4 degrees C
Indications for use of whole blood products?
Massive hemorrhage with the possibility of recurrence
Rx of established hypovolaemic shock
Blood replacement after burns
Properties of packed RBC’s?
Plasma and anticoagulant are removed from a whole unit of blood
RBC’s resuspended in smaller volume of nutrient fluid, SAGM (saline, adenosine, glucose, mannitol)
Little citrate remains
Approx volume: 300ml
Haematocrit: 60%
Shelf life: 42 days at 4 degrees C
Indications for use of packed RBC’s?
Ongoing hemorrhage where initial volume resuscitation has been carried out with crystalloids/synthetic colloids
Normovolaemic anaemia when iron therapy inappropriate
Pre-op for non elective surgery
Properties of and indications for FFP?
Plasma is extracted from whole blood and immediately frozen to preserve labile clotting factors
Sole use is to replace deficient clotting factors in patients who also need plasma volume support
Requesting for stored blood?
Group and save:
Patients blood group determined and specimen screened for antibodies
Sample kept for 72 hours during which time blood may be requested
Cross-match blood:
Must indicate degree of surgery
1. Routine: complete cross-match, and can indicate time when blood will be needed
2. ASAP: full cross-match done, and blood available within 30 min
3. STAT: incomplete cross-match done, enabling group specific blood to be issued within 5 minutes (cross-match completed during infusion and doctor informed of the results)
Checking blood products?
Unit number matches those on cross-match request form
Blood is compatible group for patient
Blood is within expiry date
Blood is for the correct patient (correct patient name, folder number and hospital number)
Administering blood?
Blood should be warmed prior to infusion (never >37 degreesC as this causes haemolysis and may provoke transfusion reaction)
Only blood giving sets with a blood filter within drip chamber must be used
Use aseptic technique when connect unit of blood to blood giving set
Transfusion of a unit should be competed within 6 hours
Monitor patient pre-, peri- and post-transfusion for possible transfusion reactions and fluid overload
(HR, BR, RR, LOC, general well-being on inquiry)
Return empty blood bags to blood bank
Complications of blood transfusions?
IMMUNE related:
- Haemolytic (ABO or rhesus incompatibility)
- Non-haemolytic (fever, urticaria, purpura, TRALI, anaphylaxis, immune suppression, graph vs host disease)
NON-IMMUNE related:
- Infectious
- Massive blood transfusion (hypothermia, hyperkalaemia, hypocalcemia, citrate toxicity, DIC, acid-base changes, fluid overload)
Clinical presentations of transfusion reactions?
Restlessness, anxiety N and V Back, flank or praecordial pain Facial flushing, sweating and itching Abnormal bleeding (DIC) Pyrexia/rigors/cold-clammy peripheries Tachy/brady cardia Tachypnoea or bronchospasm Haemoglobinura, oliguria or anuria Jaundice Coma and death
Management of a transfusion reaction?
STOP infusion IMMEDIATELY
Resuscitate patient
ABC’s
- Increase fiO2
- Assist ventilation
- Vasopressors and/or inotropes if indicated
Antihistamines/steroids
Encourage good urine flow if haemolysis/haemoglobinuria
Bloods: FBC (Hb), clotting profile (coagulopathy and DIC), U and E (renal failure)
Inform blood bank promptly
Send to blood bank:
- All units of blood and giving sets
- Post transfusion specimens of blood
- Urine sample
- Completed untoward reaction report form
When should a patient be transfused?
In an ICU patient not actively bleeding:
Should NOT be transfused until Hb >7 g/dL
Aim to get Hb to 9 g/dL
What are the properties of crystalloids?
Expand ECF
Redistributed between the intravascular and interstitial compartments in 1:4 ratio (1ml intravascular and 4ml ECF)
Full volume expansion by crystalloids after blood loss requires 3-4 x the volume loss
When should isotonic and hypotonic crystalloid fluids be used?
Isotonic fluids are suitable for intravascular resuscitation
Hypotonic fluids are suitable for maintenance, replacement and rehydration
The principle of fluid management in theatre is divided into which 3 categories?
- Re-hydration for period of starvation (1-2 ml/kg/hr x hours starved)
- Maintenance requirements during operation (1-2 ml/kg/hr)
- Replacement of ongoing losses (with isotonic crystalloids until loss exceeds 1L - then replacement should be with colloids and blood products)
Use of colloids vs crystalloids?
Colloids should be administered for haemodynamic stability
(Blood loss should be replaced with colloids on a 1:1 basis)
Crystalloids should be administered mainly for maintenance
Haemacell (Gaelatin) adv and disadv?
Advantages:
Effective
1:1
Stays in blood compartment
Disadvantages: Short acting Expensive High risk for anaphylaxis Coagulation effects
