haemorrhagic shock

Question 1

Discuss causes of hypovolaemic shock

Answer 1

Decreased intravascular space

• bleeding
• GI
• –vomiting and NG tube output
• – diarrhoea
• -enterocutaneous fistula
• renal losses
• –polyuria in DKA
• • post obstructive diuresiss
• -neurogenic DI in head injury
• inflammatory
• -pancreatitis
• • thermal or chemical burns
• -abdo surgery

Decreased Venous return to the heart

• abdo compartment syndrome
• elevated intrathoracic pressures
• –positive pressure ventilation
• -tension
• -excessive PEEP
• venodiation
• anaphylaxis
• spinal and epidural anaethesia

Question 2

Discuss pathophysiology of decreased preload

Answer 2

CO =HR x SV

SV = preload, contractility, afterload

There is a direct relationship between sarcomere length and contractile force (frank starling curve). Increasing preload increases the force of muscel contraction and CO up to a maximum after which the output plateaus

Question 3

Discuss phys and pathophys changes in hypovolemic shock

Answer 3

Hyopovolaemia leads to decrease preload and decreased SV.
Compensation starts with adrenergic response increasing both inotropy and chronotropy
As shock progresses to maintain perfusion systemic resitance and lv afterload increase redirecting blood from periphery and from splanchnic bed to central
Kidney blood flow may decrease to as little 5%-10%
Venous capacitance vessel also constrict
RAS and vasopressin are released increasing re-absorption of na and water contributing to circulating fluid volume