Fluid and Resus common QnA for HO

Part 1: Fluid and its components

Q1. What are the common cause of fluid loss in surgery?

• apparent loss: diarrhea, vomiting and high output stoma
• 3rd space loss: 
• loss of water, electrolyte and colloid particles into interstitial space
• which could contribute to edema
• Intestinal obstruction, pancreatitis and ascites
• others: insensible fluid loss (hyperventilation/pyrexia), stress response

Q1a. How patient loss fluids from IO?

• apparent loss: vomiting
• 3rd space loss: 
• increased secretions
• bowel obstruction will cause bowel to secrete a lot of secretion to overcome the obstruction. 
• mucosal edema, so fluid not absorbed
• so there will be a lot of accumulation of fluid that leads to third space loss
• fluid accumulation in bowel can reach up to 6L
• that could lead to hypovolemic shock

Q1b. How patient loss fluid from pancreatitis?

• systemic inflammation 
• inflammation causing release of inflammatory cytokine and other pro-inflammatory mediators,
• leading to capillary leakage
• thus loss of circulatory albumin and fluids to interstitium
• capillary leakage cause fluid shift to third space and then hypotension leads to hypovolemic shock.

Q2. What is the main difference between crystalloid and colloid?

• molecular size
• affects shifting of fluid where low molecular size - low tonicity

Q3. How does fluid moves in human body?

• from low concentration to high concentration 
• big molecules fluid (colloids) 
• has ability to pull fluids from other compartments : oncotic pressure
• opposite of oncotic pressure: hydrostatic pressure

** not through pressure gradient / osmosis

Q4. What is isotonic?

• a solution concentration that is similar to plasma
• the osmolarity of plasma is around 300 mosm/L
• Normal saline: 308
• Half saline: 154 (hypotonic)
• 3% saline: 1026 (hypertonic)

Q5. What is the difference between Normal Saline (NS) and Hartmann(HM) solution?

• Hartmann has additional potassium, lactate, calcium
• the most "physiological" solution

Q5a. What is the function of lactate in HM

• lactate will be metabolised by liver to HCO3, thus acting as buffer
• especially in met acidosis

Q5b. Can we use HM as resuscitation fluid?

• No
• usually when patient needs resuscitation, already with multiple organ failure or impairment
• so although Hartmann has lactate that could help as buffer, the liver is unable to convert lactate to bicarbonate, which could lead to accumulation
• the accumulation of lactate will worsen the metabolic acidosis
• and Pt in acidosis usually has hyperkalemia, Hartment contains K+ which would further worsen the situation

Q5b. So when do we use hartmann?

• as maintanence, especially in those who need replace electrolyte loss (diarrhea and vomiting)

Q6. What is the function of Dextrose 5%?

• provide hydration
• the have glucose in solution not for calorie to avoid lysis and avoid hypotonic
• calorie in D5: 170/L
• it is just to render solution isotonic once infused in the circulation, once they reach liver will convert into free fluid
• - provide free water that can pass through membrane pores, expanding both intracellular and extracellular spaces

Part 2: Fluid and resuscitations

Q7. 60year old, 70kg man presents with diarrhea and vomiting for 1 week. brought in with hypovolemic shock
Outline your management for this man

- ABC

• assess airway
• breathing
• circulation
• check the vital signs: unstable/ stable

- insert 2 large bore needles and give IV NS

- run fast 1 pint NS

Q7a : If patient doesn't respond to fluid resus? 

• reaccess: if the volume is improved, but patient still hypotensive, he might have other component of shock
• for example: septicaemic shock --> we might need to start inotrope for vasoconstriction
• if cardiogenic shock / has underlying IHD --> get an ECG, and we might need to start with dopamine or dobutamine as the inotropic support. 
• if volume is still low, 
• can infuse COLLOID to hold the fluid in the circulation
• colloid has oncotic pressure that will hold the fluid intravascularly, thus maintain the BP

• So why we cant give colloid straight away for resus?
• Colloid causes shifting of fluid out of the cell, worsen the hypoperfusion
• in shock, circulation fails and tissue is hypoperfused, if we infuse hypertonic solution all fluid will move from the tissue into the intravascular system . 
• Therefore load with volume first (crystalloid)
• resume the circulation
• let them reach the heart, brain and kidney
• after that infuse colloid to hold the volume. 

Q8: Define shock

• must have 2 components
• circulatory failure: seen via vital signs
• inadequate tissue perfusion : seen via low SPO2
• sequelae of low perfusion
• multiorgan failure

Q9: Why we cant have central line when patient is in shock?

• it is about the catheter's caliber. the shorter the calibre, faster the infusion. 
• if central line, it has long calibre and the rate of infusion is slower
• insertion takes a lot of time
• in shock we need large supply of fluid for the patient 
• Poiseuille law

Q10: How do you know patient responded to your fluid resuscitation? what are your AIMS?

• vital signs 
• HR <90
• BP >90/60 , MAP >60
• SPO2 >95%
• RR <20
• u/o  >0.5ml/kg/hr