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Arginine-GHRH test - Investigation protocol

Indication

Assessment of  growth hormone reserve when insulin stress test is contraindicated.

Preparation and precautions

Patients should be fasting from midnight (water only). Warn the patient that they may well experience flushing, nausea, an unusual taste and a transient drop in blood pressure during the test.

Procedure

Wiegh the patient without shoes on and take baseline pulse and blood pressure recordings. Insert a cannula gauge 20 with a three-way tap into each arm. Allow the patient to rest for 15 minutes. Monitor the patient's pulse and BP every 15 minutes until +150 minutes into the test and every 30 minutes thereafter to +240 minutes.  Using a syringe or the vacutainer connector system, fill one plain clotted bottle for growth hormone and baseline IGF-I level from cannula 1, and label this -15 minutes. Label with patient identification, date and write time=0 minutes.

Using the separate cannula 2, give GHRH 1mcg/kg (maximum dose 100mcg) as a bolus injection and flush with 10ml normal saline. Then start an infusion of 0.5g/kg arginine (maximum dose 30g/300ml) over 30 minutes into cannula 2, as prescribed by the requesting doctor.

Take further blood samples from cannula 1 as above for GH only immediately after the infusion ends and label this + 30 minutes. Take further samples, also from cannula 1 at 45, 60, 90, 120 and 150 minutes after the start of the infusion. Mark the patient’s details, date and time of samples on each bottle. Each time samples are taken, flush the cannula with 2mls 0.9% sodium chloride and prior to taking blood samples, withdraw 2mls and discard to remove any trace of the sodium chloride flush.

The patient should remain fasting during the test but can sip water. After the 150 minute samples have been taken, both cannulae can be removed, and the patient offered a meal.

Patients should remain resting in bed and have pulse and BP monitored every 30 minutes until +240 minutes. The patient may then go home.

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