2A

Metformin increases the risk of contrast induced nephropathy and should be stopped 48 hours before any procedure that involves the use of intravenous contrast and should not be restarted until one is certain that contrast-induced nephropathy has not occurred. Contrast induced nephropathy is defined as an acute increase of 25 percent increase in serum creatinine from the baseline (or an increase of 44umol/L <0.5mg per dL> in the serum creatinine). Reference: New England Journal of Medicine

The group of drugs belonging to the class of thiazolidinediones should be used with caution in patients with diabetes and coronary heart disease or heart failure because of increased adverse cardiac events (especially congestive heart failure) that have been noted with their use. Lancet and NEJM

When initiating insulin in Type 1 diabetes, the total requirement of insulin is calculated at 0.5 to 1 unit per kg body weight. For a person who is 50kg, 50 units of insulin per day will be needed. Half of this - 25 units - should be prandial insulin and a similar amount should be basal insulin. The prandial insulin is spread out over three main meals: 8 units before breakfast, lunch and dinner. The basal insulin (25 units) is given two-thirds in the morning and one-third in the evening/night. This means that he should receive about 16 units in the morning and 9 units in the evening of basal insulin.
Biphasic insulin (Mixtard 30/70) which contains a pre-mixed combination of 30 percent short acting and 70 percent long acting insulin in the morning and evening makes it easier to administer because it avoids the need to mix two different types of insulin for the injections in the morning and evening. A long acting insulin (or a biphasic insulin) should not be prescribed before lunch because its peak action will be at midnight and that increases the risk of nocturnal hypoglycemia. Similarly, short acting insulin (or a biphasic insulin) must not be prescribed at bedtime if there is no bedtime snack.

Initiating insulin for long term control of Type 2 diabetes should be done by using a basal insulin (long acting insulin or biphasic insulin) given once a day, preferably at night. The starting dose is 0.2units per kg body weight. If a long acting insulin like Insulatard is used, it can be given at bedtime (or before dinner). However, if a biphasic insulin (like Mixtard 30/70) is used, it must be given before dinner only. It can be given at bedtime if the patient is in the habit of taking a snack at bedtime. When initiating insulin as part of the BIDS regimen, it is probably safer to discontinue sulphonylurea drugs until the effect of the insulin on the blood sugar has been observed. The sulphonylurea can be added in a low dose, if necessary, later. Metformin can be continued.

An insulin intravenous infusion regimen and a subcutaneous insulin sliding scale regimen (test and treat regimen) are both used for control of plasma glucose in an acute setting. An insulin intravenous infusion regimen is absolutely required when controlling blood sugar in a patient who is unable to take orally (example: during surgery or because of vomiting). An insulin sliding scale regimen where multiple doses of short acting insulin is given subcutaneously with frequent glucose monitoring is used for control of blood sugar in acute medical conditions where the patient is able to take orally. A subcutaneous sliding scale insulin regimen where insulin is given three or four times daily is often used as a substitute for an insulin infusion regimen because an insulin infusion regimen requires intensive monitoring. In an insulin intravenous infusion regimen, plasma glucose must be monitored every hour while in a subcutaneous sliding scale regimen, it is monitored every 8 hours or every 6 hours.
Plasma glucose control will be better with an insulin intravenous infusion regimen than with a subcutaneous sliding scale regimen.
When using a sliding scale insulin regimen where insulin is given more frequently than every eight hours subcutaneously, it is important to remember that hypoglycemia can occur abruptly because of insulin pharmacokinetics that result in overlap of insulin action.

The glycosylated hemoglobin (HbA1c) value is a net reflection of the plasma glucose values in the pre-prandial and postprandial states. When the glycosylated hemoglobin value is high but the fasting (pre-breakfast) glucose value is normal, we should first check the pre-prandial glucose values before lunch and before dinner. If these are normal, then we can assume that the postprandial values are high and proceed to check the plasma glucose two hours after meals. If the pre-prandial values are high, it is better to target therapy to ensure that these are well controlled before checking the postprandial glucose values. A glucose tolerance test only has diagnostic value and cannot be used to fine tune therapy.

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