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insulin

insulin

introduction

  • insulin dosing should be considered in terms of:
    • basal dosing with a long acting agent
    • prandial dosing prior to meals with regular insulin
    • corrective dosing with rapid acting insulin
    • therapeutic infusion regular insulin for Mx of diabetic ketoacidosis (DKA)

types of insulin

  • most current insulin preparations in Australia contain human insulin prepared by recombinant DNA technology. Only Hypurin Neutral and Hypurin Isophane contain insulin of bovine origin.
  • Protaphane, Actrapid and Mixtard should be given 30min before meals
  • Ultrarapid insulins such as Humalog, Humalog Mix 25, NovoRapid, and NovoMix 30 should be given immediately with meals 1)
  • ultra rapid onset and short duration:
    • glulisine (Apidra), lispro (Humalog) and aspart (NovoRapid) are modified human insulins that have onset and offset after subcutaneous injection that is half that of regular insulin.
    • glulisine - maximum effect after s/c dose ~60min and effect lasts ~1.5 hours
  • rapid onset, short duration:
    • regular/neutral/soluble insulin
      • maximum effect after s/c dose ~90min and effect lasts some 2.5 hours
      • often used as a corrective dose, as part of a sliding scale insulin regime, and as iv infusion for Mx of diabetic ketoacidosis (DKA)
      • eg. Actrapid, Humulin R
  • intermediate acting suspensions (NOT for iv use):
    • isophane insulin
      • Humulin NPH (rbe) - onset of action occurs at ~1hr, with a duration 16-18 hrs and peak at 4-10hrs.
      • Hypurin Isophane NPH (bovine)
      • Protaphane (rys)
  • long acting (NOT for iv use):
    • these are expensive, cannot be mixed with other insulins and thus require extra injection, and most find they don't last the full 24 hours, but can be given any time of day as long as it is the same time each day.
    • glargine insulin (Lantus)
      • lasts for 24 hours and has a very flat profile and thus provides good basal levels of insulin as a daily bolus injection.
      • for type 2 diabetics: initially 10 Units s/c once a day
    • detemir insulin (Levemir)
      • for type 2 diabetics: initially 10 Units or 0.1-0.2 Units/kg s/c once daily
  • mixed biphasic neutral + isophane insulin suspensions for once daily or bd s/c dosing (NOT for iv use)
    • Mixtard insulin contains recombinant human insulins (rys) - available as 30/70 or 50/50
    • Humulin 30/70 - duration of activity of 16-18hrs and peak at 2-12 hrs
  • mixed biphasic ultra rapid + protamine insulin suspensions for once daily s/c dosing (NOT for iv use)
    • Humalog Mix25 and Humalog Mix50 - lispro + protamine
    • NovoMix 30 - aspart + protamine

insulin administration errors

  • insulin dosing is one of the major causes of medication administration errors
  • ALWAYS write UNITS and not just IU or U which can be mistaken as 10 or 0 and thus cause a 10x increase in dose
  • DO NOT use tuberculin syringes as these are labeled differently and can easily result in a 10x increase in dose
  • name confusion with Humalog and Humulin, Humulin U and Humulin N, and with Insulin Lente and Insulin Lantus.
  • failure to re-suspend insulin suspensions prior to drawing up - gentle rolling of vial in palm is important for these otherwise one may draw up solution containing only 20 units/ml instead of 100 units/ml. Insulin pens also require this re-suspension prior to use.
  • pump programming errors
  • insulin infusion pumps turned off for inter-hospital transfers and then forgetting to be re-started.
  • computerised prescribing errors
  • blood glucose measuring device read out design errors which can allow read out to be mistaken (eg. LO may be mistaken as 10)

peri-operative insulin Mx

  • A reasonable trade off between avoiding hypoglycaemia and possible complications of hyperglycaemia is to aim for an intraoperative blood glucose level of 5 to 10 mmol/L.2)
  • Using the same principles used in managing blood pressure the important components are first to frequently (at least hourly) measure the blood glucose and not to over treat hyperglycaemia and hypoglycaemia (avoid Alpine BSLs).
  • 5% dextrose can be used to treat hypoglycaemia (2 ml/Kg) intravenously, but can also be given orally.
  • Hyperglycaemia is treated with corrective doses of insulin.
  • In the postoperative period the rapid acting insulins are likely to be much better for sliding scales than regular insulin.
  • diabetic patients need 3 levels of glycaemia control:
    • basal control
      • glargine insulin has such a flat profile that patients can take their usual dose before surgery with minimal risk of hypoglycaemia while also avoiding ketosis. This is easier than running a glucose-insulin or glucose-insulin-potassium (GIK) infusion.
      • glargine, which lasts for 24 hours and has a very flat profile. Glargine provides good basal levels of insulin as a daily bolus injection.
      • basal insulin can also be provided with continuous insulin pumps using rapid acting insulin such as aspart or lispro.
    • nutritional
      • 5% dextrose infusion 100ml/hr for fasting adults (higher if BGL falls below 4 mmol/L)
      • prandial dose insulin for those who are not fasting
    • corrective
      • orrective insulin in the operating room can be with regular insulin by the intravenous route that hastens the onset.
      • subcutaneous rapid acting insulin is an alternative - as an example see Sliding Scale Insulin below

sliding scale insulin (SSI)

  • NOTE: fasting diabetic patients should have 5% dextrose running at 100ml/hr (higher if BGL falls below 4 mmol/L)
  • the BGL should be determined 4hrly if fasting, or qid - 30min prior to meals and before sleep (or if features of hypoglycaemia or hyperglycaemia develop) and the s/c dose of regular insulin given according to the scale
  • those who are not fasting will develop unstable control if doses are not synchronised to be measured 30min before meals 3)
  • sliding scale insulin using regular insulin is not physiological and does not make clinical sense, indeed, in type 1 patients, is likely to lead to increased instability due to the delayed onset of action.
  • if a sliding scale is used for corrective Mx, it should be with a rapid acting agent and preferably dosing should be related to total daily requirements as each person will have different insulin sensitivities and these may change during their illness.
  • it is time we ceased using the traditional regular insulin sliding scale protocols! 4)
  • example traditional s/c sliding scale insulin for either fasting or oral diet patients, and can be used for type 1 and type 2 patients
blood glucose reading in mmol/L traditional regular insulin dose s/c in units
< 3.5 Mx as per hypoglycaemia
0-5 nil
5.1-8 4
8.1-12 8
12.1-16 12
above 16 16
above 20 notify Dr
insulin.txt · Last modified: 2012/09/27 06:25 by gary1