Sun28November0628PM 23

In hypovolaemic shock which of the following is true?

(Please select 1 option)

A narrowed pulse pressure indicates significant blood loss Correct

Anuria (less than 17 ml/hr) occurs early

Tachycardia and lowered blood pressure are early manifestations

Haematocrit and haemoglobin are good indicators of estimated blood loss

Vasodilatation is an early response to blood loss

Explanation

Haemorrhage is the commonest cause of shock and post injury death in the trauma patient, and the only method of stopping on-going losses and stabilising the patient may be surgical. Therefore early surgical review is vital, along with early identification of shock itself.

Early circulatory changes are compensatory and include tachycardia and cutaneous vasoconstriction.

As the amount of blood loss increases and tissue perfusion further decreases, urine output is reduced and so eventually is the patient's level of conciousness.

Significant reduction in blood pressure is a relatively late manifestation and a narrowed pulse pressure is an indicator of significant blood loss. Unfortunately, haemoglobin and haematocrit are unreliable in estimating acute blood loss, and should not be used for diagnosing shock as they may only show minimal acute decrease in massive blood loss.

Oliguria is defined as a urine output of less than 17 ml/hr or more practically less than 400 ml in 24 hours. Oliguria only occurs when 30-40% of the circulating volume (class III haemorrhage) has been lost.

Anuria is defined as a urine output of less than 50 ml in 24 hours and only occurs when greater than 40% of the circulating volume has been lost.