Raman spectroscopic monitoring of hemodialysis

Abstract

Spectroscopic systems and methods are disclosed for determining levels of at least one analyte in blood undergoing hemodialysis. In one aspect, the invention employs Raman spectroscopy to monitor and/or control hemodialysis. In one embodiment, the system uses a laser light directed to circulating blood from a patient undergoing dialysis to make Raman spectral measurements. For example, the laser light can be directed into a segment of the dialysis tubing. The system can utilize unique Raman spectroscopic signature of one or more analytes, e.g., urea, to identify and quantify such analytes against a whole blood background. Based on the spectral response, the concentration of the analytes can be monitored and/or used to control hemodialysis.

1 . A method for monitoring hemodialysis, the method comprising the steps of:
 irradiating a sample of blood undergoing hemodialysis with light;   obtaining a Raman spectrum of chemical constituents from the sample; and   analyzing the Raman spectrum to detect one analyte in the sample, the analyte being indicative of the progress of dialysis.   
   
   
       2 . The method of  claim 1 , further comprising:
 repeating the steps of irradiating and analyzing to detect changes in level of the analyte over time.   
   
   
       3 . The method of  claim 1 , wherein the step of irradiating the sample further comprises irradiating the sample with light of at least one wavelength in the range from about 700 nanometers to about 2.5 micrometers. 
   
   
       4 . The method of  claim 1 , wherein the step of irradiating the sample further comprises irradiating the sample with light from a multi-mode laser. 
   
   
       5 . The method of  claim 1 , wherein the step of irradiating the sample further comprises irradiating the sample with a broad band light source. 
   
   
       6 . The method of  claim 1 , wherein the step of irradiating the sample further comprises irradiating the sample with infrared light. 
   
   
       7 . The method of  claim 1 , wherein the step of analyzing the spectrum further comprises analyzing a Raman spectrum of light scattered by the sample using a low resolution detector. 
   
   
       8 . The method of  claim 1 , wherein the step of analyzing the spectrum further comprises determining the concentration of at least one analyte in the sample. 
   
   
       9 . The method of  claim 1 , wherein the analyte is selected from a group consisting of: a urea-based compound, an ammonium-based compound, a uric acid-based compound, and a nitrogen-based compound. 
   
   
       10 . The method of  claim 1 , wherein the analyte is urea. 
   
   
       11 . The method of  claim 1 , wherein the analyte is blood urea nitrogen. 
   
   
       12 . The method of  claim 1 , wherein the blood sample is flowing through a transparent tube. 
   
   
       13 . The method of  claim 12  wherein the tube is part of a hemodialysis system. 
   
   
       14 . A method for monitoring a subject's urea concentration, the method comprising the steps of:
 irradiating the blood sample from a subject;   collecting a Raman spectrum of light scattered by the sample;   analyzing the Raman spectrum to detect the concentration of urea in the sample, the concentration of urea being indicative of the progress of dialysis or kidney function.   
   
   
       15 . The method of  claim 14 , further comprising:
 repeating the steps of irradiating and analyzing to detect changes in urea concentration over time.   
   
   
       16 . The method of  claim 14 , wherein the decrease in concentration of urea is indicative of elimination of toxins from the blood sample during dialysis. 
   
   
       17 . The method of  claim 14 , wherein the Raman spectrum is analyzed by a low resolution Raman spectroscopy system. 
   
   
       18 . In a hemodialysis system, the improvement characterized by a Raman spectral analysis system comprising:
 means for irradiating a sample of blood undergoing hemodialysis;   means for obtaining a Raman spectrum of chemical constituents from the sample; and   means for analyzing the Raman spectrum to detect the concentration of at least one analyte in the sample, the concentration of the analyte being indicative of the progress of hemodialysis.   
   
   
       19 . A hemodialysis system comprising
 at least one blood cleaning element for removing toxins from blood;   a light source to irradiate a sample of blood undergoing hemodialysis;   a Raman spectrometer to detect the concentration of at least one analyte in the sample, the concentration of the analyte being indicative of the progress of hemodialysis.   
   
   
       20 . The system of  claim 19 , wherein the system further comprises a processor that controls hemodialysis based, at least in part, on data from the Raman spectrometer.