Circulation Flashcards
What proportion of TBW is intracellular volume?
2/3rds TBW - 70kg man = approx 28 litres
What proportion of the ECF is plasma volume?
20%
What proportion of the ECF is interstitial fluid?
80%
What proportion of TBW is the extracellular fluid?
1/3rd
What is the definition of shock?
Inability of the circulatory system to meet end organ perfusion requirements.
What are the different types of shock?
- Distributive
- Obstructive
- Cardiogenic
- Hypovolaemic
- Neurogenic
How does the body respond to hypovolaemia?
- Tachycardia
- Increased contractility of the heart
- Peripheral vessel constriction - maintain oxygenation to brain and heart
What are the 5 major sites for major haemorrhage?
On the floor and 4 more:
- 3 main central cavities - Chest, abdomen, pelvis
- Long bones
Why are pelvic fractures such a bleeding risk?
There are numerous sources of bleeding in pelvic fractures:
- Bones
- Venous plexus
- Arterial plexus
Why can pelvic fracture cause such a large loss of blood?
Pelvic ring is disturbed, meaning that tamponade of any bleeding does not occur allowing the blood to communicate to the retroperitoneal space (which has a furhter 5L of volume), the thighs and the peritoneum
Therefore pelvic fractures can be considered bleeding into a free space potentially able to hold the entire blood volume
How would you approach assessing circulation in someone in a pre-hospital setting?
- Inspect - major haemorrhage, patient status
-
Palpation - CRT, Pulse rate and rhythm, peripheral pulses, skin temp
- GET ACCESS AT THIS POINT - IV/IO
- Auscultate - heart sounds
- Blood pressure measurement
- Assess major bleeding sites
- AVPU - are they cerebrating
What are you looking for when inspecting the patient for circulation?
- Hands/face blue
- Mottled skin
- AVPU - quick cranial perfusion assessment
What does pallor/cyanosis indicate?
Poor perfusion to tissues
What is normal for a Capillary refill time (CRT)?
2 seconds or less
Where can cap refill be performed?
- Peripherally - Nail bed
- Centrally - sternum, forehead
What would tachycardia and hypotension indicate in a patient who is suscpected to be bleeding?
Severe shock
What would a weak/thready pulse indicate?
Hypovolaemia
What is an absent radial pulse indicative of in terms of management?
Begin IV fluids
Is a low BP in isolation indicative of shock?
No - need other clinical signs such as tachycardia, pale skin, decreased consciousness
What is regarded as the minimum BP that a radial pulse is palpable at?
>80 mmHg
If the femoral pulse is palpable but the radial is absent, what would you guess the blood pressure is roughly sitting at?
70-80 mmHg
What is the minimum systolic BP that the carotid pulse is palpable at??
>/= 60 mmHg
Does hypotension usually occur early or late in shock?
Late - occurs with over 25% blood loss
What is the order in which pulses become absent as hypovolaemia worsens?
Radial absent -> femoral absent -> carotid absent
How would you manage external haemorrhage?
- Pressure and elevation
- Wound Packing
- Tourniquet
Why can it sometimes be difficuult to obtain IV access?
People can be peripherally shut down - access should be established early if needed
What are complications that can occur when gaining IV access?
- Thrombophlebitis
- Thromboembolism
- Sepsis
- Air embolism
- Arterial puncture
When is intraosseous access considered/indicated for?
- To prevent an emergent situation
- When obtaining peripheral or central intravenous access is difficult
What is intraosseous access?
Involves inserting a needle into the vascular intramedullary space that, in turn, provides direct access to the central circulation via the Volkmann canals. It is fast and reliable
What are contraindications to IO access?
- Inability to locate landmarks
- Fractures in the same extremity as targeted bone
- Previous surgery involving hardware in the targeted bone
- Infection at insertion site/within target bone
- Local vascular compromise
- Previous failed IO within 24 hours in target bone
What are complications of IO access?
- Incorrect positioning leading to extravasation/sub-periosteal infusion
- Osteomyelitis
- Physeal plate injury
- Local infection, pain
- Compartment syndrome
- Fat embolism
How would you insert EZY-IO access?
https://www.youtube.com/watch?v=j3QRXjn-Owc
- Skin cleaned and limb stabilised.
-
Needle gently inserted at 90o to insertion site until contact felt with bone
- If 5mm mark on the needle is not visible then a larger needle is needed.
- If 5mm mark is visible then gentle and steady pressure + drill power applied until:
- Sudden ‘give’/‘pop’ is felt - entry to the medullary space.
- The desired depth is obtained
- Remove power driver and stylet from catheter, aspirate to confirm the placement
- Flush and dress the site appropriately.
What are the main types of IO access?
- IO needle
- EZY-IO
- FAST1
What locations are used for IO access?
- Proximal tibia - Tibial tuberosity
- Distal tibia - medial malleolus
- Humeral head
- Distal femur
- Iliac crest
Which site for IO access can achieve higher flow rates, Humeral head or tibia?
Humeral head
Rank access sites for IO in terms of flow rate?
- Humerus
- Femur
- Malleolus
- Tibia
What are risks of giving someone fluids in a pre-hospital setting?
- Delay to patient transfer
- Re-bleeding
- Increased blood loss
Why can re-bleeding occur in someone who has been given fluids in a pre-hospital setting?
An increase in blood flow can lead to re-bleeding from sites where bleeding may have previously ceased. This is described as ‘popping the clot’ whereby an increase in hydrostatic pressure cause displacement of the clot leading to re bleeding
When should fluids not be given in a pre-hopital setting?
If the radial pulse is palpable
How much fluid should be given to someone if they are deemed to require fluids?
250 ml Bolus saline, then reasess. If radial pulse still not palpable, give another 250mL bolus
