Plasma volume expansion from the intravenous glucose tolerance test before and after hip replacement surgery

Osmotic and Hemodynamic Effects of Hypertonic Glucose During Hemodialysis

It was the purpose to quantify the hemodynamic effects of a bolus of hypertonic glucose injected into the extracorporeal system in a group of stable and nondiabetic patients during hemodialysis (HD). Glucose and electrolytes were measured in frequent intervals. Arterial blood pressures and heart rates were continuously recorded by noninvasive vascular unloading technique. Beat-to-beat stroke volume, cardiac output, and total peripheral resistance were determined by Modelflow method. Relative blood volumes were continuously measured by ultrasonic and optical means. Eight patients were studied in two treatments. Although arterial pressures and heart rates remained stable, stroke volume and cardiac output transiently increased above (19.2 ± 12.3%) and total peripheral resistance dropped below baseline (18.2 ± 8.6%) by a comparable magnitude. Relative blood volume transiently increased above baseline at 100% (104.9 ± 1.0%). Glucose concentrations were significantly related to relative blood volumes (r = 0.86, p < 0.001). In spite of a substantial increase in blood volume, a bolus of hypertonic glucose does not increase arterial pressures in nondiabetic patients because of concomitant vasodilatation. The relative increase in blood volume quantified by noninvasive HD technology follows the course of glucose and could be used as a surrogate to characterize patients with regard to their glucose metabolism during HD.

How fast can glucose be infused in the perioperative setting?

Background

How the initial infusion rate of glucose solution should be set to avoid hyperglycemia in the perioperative setting is unclear.

Methods

Computer simulations were performed based on data from seven studies where the kinetics of glucose was calculated using a one-compartment model. Glucose had been infused intravenously on 44 occasions to volunteers and on 256 occasions to surgical patients at various stages of the perioperative process. The rates that yield plasma glucose concentrations of 7, 9, and 12 mmol/l were calculated and standardized to a 5 % glucose solution infused in a subject weighing 70 kg.

Results

The lowest infusion rates were found during surgery and the first hours after surgery. No more than 0.5 ml/min of glucose 5 % could be infused if plasma glucose above 7 mmol/l was not allowed, while 2 ml/min maintained a steady state concentration of 9 mmol/l. Intermediate infusion rates could be used in the preoperative period and 1–2 days after moderate-sized surgery (e.g., hysterectomy or hip replacement). Here, the half-lives averaged 30 min, which means that plasma glucose would rise by another 25 % if a control sample is taken 1 h after a continuous infusion is initiated. The highest infusion rates were found in non-surgical volunteers, where 8 ml/min could be infused before 9 mmol/l was reached.

Conclusions

Computer simulations suggested that rates of infusion of glucose should be reduced by 50 % in the perioperative period and a further 50 % on the day of surgery in order to avoid hyperglycemia.