Continuous monitoring of blood parameters in intensive care patients

Introduction

Monitoring of blood parameters, such as glucose, hemoglobin and oxygen saturation, is essential in critically ill patients. The current invasive methods are not frequent enough for efficient tight glycemic control, and result in a high rate of hypoglycemia. In addition, there is a growing need for a continuous hemoglobin measurement in postoperative care units and ICUs. The purpose of this study is to evaluate the feasibility of the fully noninvasive blood monitor (NBM device; OrSense Ltd, Nes Ziona, Israel) for continuous monitoring of glucose, hemoglobin and oxygen saturation in critically ill patients.

Methods

The study was conducted on 14 patients (seven female, seven male, ages 34 to 92 years) in the ICU of the Rabin Medical Center, upon receipt of informed consent. The NBM probe was placed on patients' thumbs, where it performed measurements for up to 24 hours, with readings every 10 minutes. Patient compliance was good and no adverse effects were identified. The results obtained from the NBM device were compared with blood samples taken through an arterial line every 30 to 60 minutes and were analyzed with a blood gas machine (ABL 700; Radiometer, Copenhagen, Denmark).

Results

A total of 208 paired data points were obtained in the trial. At each point, an algorithm based on a uniform model (with personal glucose calibration) was used to calculate the three blood parameters. The reference glucose range was 62 to 369 mg/dl. The median relative absolute difference was 7.3%, and a Clarke error grid analysis showed that 95.2% of the measurements fell within zones A (74.5%) and B (20.7%). The reference range of the hemoglobin was 7 to 14.5 g/dl and the median absolute error obtained was 1 g/dl. Oxygen saturation levels were tracked simultaneously with a mean error of 2.5%.

Conclusion

The present study indicates the potential use of the noninvasive NBM for continual, accurate, safe, and easy-to-use multiparameter monitoring in critically ill patients. The device holds the promise of improving patient care and survival, as well as reducing staff workload.