For patients not an a Variable Rate Insulin Infusion (VRII), a raised blood glucose > 10 mmol/L should be repeated within 2 hours and if persistently elevated the doctor / ACCP covering the unit should be informed.
An unexpectedly high or low sample taken from an arterial line or central line port may represent dilution from the flush line or contamination with glucose and should be checked with capillary point-of-care (POC) sample. The contents of the flush solution must be checked to confirm that it contains no glucose. Similarly, POC capillary glucose is the least accurate method and an unexpectedly abnormal sample should be checked against an arterial or venous blood gas analysis.
If Variable Rate Insulin Infusion is commenced, then blood glucose should be checked 1 hourly, ideally via ABG / VBG. POC capillary sampling is acceptable if patient’s glucose control has been stable to over the preceding 24 hours and no arterial or venous access is available for monitoring. There may be considerable difference between POC analysis and gas analyser results (up to 2mmol/L) so once one method is used it is preferable to continue with this. Unexpected or grossly abnormal results must be checked with another device.
A VRII should be commenced if a patient’s blood glucose is confirmed to be > 10mmol/L on 2 separate readings taken 1-2 hours apart.
Target range for glucose control is 6 - 10 mmol/L.
::: info Pending further evidence to support individualised treatment thresholds and target ranges according to preadmission glycaemic control, all patients will be initiated on the above protocol. Admission diabetic status and HBA1c should be documented to facilitate post management post critical care and to aid decision making in individual cases where large doses of exogenous insulin are required. :::
When the patient is well and has commenced diet, record pre meal capillary blood glucose levels to assist the accurate adjustment in insulin dosages.
A VRII should be commenced according to the initial glucose reading using the table in the Hyperglycaemia protocol shown in the table above.
Insulin infusion should be via a Dynamic Sliding Scale using the Critical Care Network insulin calculator: saferinsulin.org
If a Dynamic Sliding Scale Calculator is unavailable, a paper-based Variable Rate Insulin Infusion modified for use in Critical Care should be used. If the patient is awaiting step down to the wards, the pink Variable Rate Insulin Infusion chart should be used or consideration given to restarting usual diabetes medications – particularly if the patient is eating and drinking.
Prefilled Insulin Actrapid 50 units or Humulin S in Sodium Chloride 0.9% 50ml should be used via a dedicated peripheral cannula or central lumen that has been confirmed to be patent and can be easily aspirated and flushed.
Insulin preparations should be replaced every 24 hours to minimise the loss of potency
If a Variable Rate Insulin Infusion is being stopped temporarily or is no longer required, blood glucose should be monitored hourly for at least 4 hours after stopping: this is particularly relevant when suspending for procedures or scans.