Dedicated monitoring of anesthetic and respiratory gases by Raman scattering.

The monitoring of respiratory and anesthetic gases in the operating room is important for patient safety. This study measured the accuracy and response time of a multiple-gas monitoring instrument that uses Raman light scattering. Measurements of oxygen, carbon dioxide, nitrogen, nitrous oxide, halothane, enflurane, and isoflurane concentrations were compared with a gas mixer standard and with measurements made with an infrared anesthetic agent analyzer. Correlation coefficients were all greater than 0.999, and probable errors were less than 0.43 vol% for the gases and less than 0.03 vol% for the volatile anesthetics. Response time was 67 ms with a sample flow rate of 150 ml/min. There was some signal overlap between nitrogen and nitrous oxide and between the volatile anesthetic agents. Such overlap can be compensated for by linear matrix analysis. The Raman instrument promises a monitoring capability equivalent to the mass spectrometer and should prove attractive for the monitoring of respiratory and anesthetic gases in the operating room.

Human haptoglobin adsorption by a total internal reflection fluorescence method.

Haptoglobin (Hp) is one of the major protein constituents of plasma. Three different forms are found in the population. The 1-1 and 2-2 forms adsorb similarly onto hydrophobic silica [treated with dimethyl dichlorosilane (DDS)] and onto clean silica, although the affinities on the silica surface are lower at 60 minutes contact time. The two forms desorb differently from silica, but desorb similarly from DDS-silica. Adsorption is less reversible on the hydrophobic surface. Due to its adsorbtion tendencies and its high concentration in plasma, the adsorption of Hp may be important in blood interaction at solid-liquid interfaces.

Oxy- and deoxyhaemoglobin adsorption onto glass and polymer surfaces.

The adsorption of deoxyhaemoglobin (deoxyHb) and oxyhaemoglobin (oxyHb) was determined on clean glass, n-pentyl triethoxysilane (NPS)-treated glass, polystyrene (PS), and a polyetherurethane (PEU). The adsorbed amounts range from 0.1 to 0.6 micrograms/cm2 for oxyHb and from 0.3 to 0.7 micrograms/cm2 for deoxyHb. DeoxyHb adsorbs onto all these surfaces more than oxyHb. The more hydrophobic the surface, the more adsorption of both deoxy and oxyHb forms. These results suggest the oxyHb and deoxyHb interact differently with the surfaces studied. It is likely that the surface hydrophobicity of Hb plays a major role in Hb adsorption onto surfaces; the deoxyHb surface is more hydrophobic than the oxyHb surface. The binding sites for Hb adsorption may include the clefts between alpha 1, beta 1. A surface-induced dimerization mechanism is proposed to explain the adsorption of oxyHb.