RENAL PROBLEMS AND CRITICAL CARE Solution 6

This patient may have been hypovolemic pre-operatively due to the administration of laxatives, to prepare the bowel. Moreover, there may have been extensive insensible and third space losses during the case, due to his abdominal wall being open and bowel handling by the surgeons. It is important to always assume that the patient is hypovolemic first, and administer more fluids.

2 further liters of fluid are given in the next hour, and the patient puts out only 30ml of urine. His CVP is now 18cmH2O.

What are you going to do now?

I would treat this patient with diuretics.

But shouldn’t he diurese spontaneously?

The stress response to surgery, positive pressure ventilation and pain are all potent stimuli to the release of anti-diuretic hormone. In addition, inappropriate release of anti-natiuretic hormones such as aldosterone and glucocorticoids may occur. The result is paradoxical retention of fluid, despite aggressive resuscitation. The patients will often respond to a small bolus of furosemide (e.g. 10mg). It is essential to out rule a genuine injury (be it pre-, intra- or post-renal)  before resorting to this strategy.