Since the dawn of IV TPN insulin has been added to the formula as needed to keep the blood glucose below 200 gm%. This is renal threshold. The aim is to prevent glucosuria and associated osmolar dehydration. An objection was that 17% of the insulin adheres to the glass. Since what adheres is immediate, this makes no difference re clinical efficacy. An estimate of how much insulin should be added is 5 U regular insulin per glucose + in the urine. i.e., 2 + glucosuria requires the addition of 10 more unites to the formula.
Ignoring glucosuria will lead to hyperosmolar nonketoic dehydration and potentially death. Prolonged hyperglycemia will predispose the patient to fungal infection.
Mitchell,
Renal threshold for glucose you quoted (200 gm%) seems a tad high - by over three orders of magnitude.
In normal humans the threshold is reported to be 180mg/dl. However, among diabetics the value has quite a range.
The goal is to prevent glucosuria and diuresis. I prefer to tailor the added insulin to keep the blood sugar about 80 to 110 mg%.
Try to maintain blood sugar level between 80 and 100mg%, preferably by delivery of the TPN under strict, conscientious control, using an IV pump and well trained Nursing Staff surveillance. Add insulin to the TPN judiciously as indicated to achieve the desired TPN goal while maintaining normal blood sugar range. This demands dedicated, educated, motivated effort. If unwilling to adhere to the principles of safe, effective TPN administration and management, don't expose the patient to danger by dabbling with it. The insulin sticking to the glass is irrelevant "ancient history"-- TPN is provided in plastic bags. Moreover, enough insulin is given to achieve the optimal blood sugar level and total TPN goal, no matter what minute quantity might be "lost" during infusion. Treat the patient!!! Don't forget that insulin requirements can change during the course of illness and dosage must be adjusted accordingly, e.g. ,should infection, pneumonia, other stressful events intercede. Monitor blood potassium and phosphorus levels as insulin dose is changed, as these cations move into the cells, as the sugar and insulin move increasingly into the cells from the vascular compartment. It's all about clinical chemistry and metabolism and responses to pathophysiology and/or therapeutic measures---and good old common sense and judgment, coupled with adequate education, training, and experience.
To continue the dialog, Watch for a change in the clinical status. The 3 's: sepsis, stress and steroids are associated with insulin resistance. Knowing the above you are forewarned thus fore armed. Complications from chronic hyperglycemia during TPN should not occur.
Amen to that, Mitch. Hope you and your Family have a Happy Holiday and New Year 2017. Stay active and productive!
It is not that easy. I am a proponent of "infusion interrupt" But be aware that blood glucose will drop when the infusion is DCed. Slowing the rate before interrupt will simply lower the glucose. Decreasing the glucose concentration using a formula of D15 and fat 20 is a good idea. We now know that over feeding hyper tonic dextrose is pro inflammatory...a contributor to insulin resistance. In conclusion: keep the final dextrose solution low by adding fat as a 3in one. Then do not decrease the rate infusion before interrupt. Just stop/heparin flush and clamp.
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