Method and apparatus for monitoring blood chemistry

A method for monitoring a predetermined parameter of a patient's blood while infusing an infusion fluid through a sensor assembly and catheter into the patient, the method comprising:

• operating an infusion pump in a forward direction, to infuse the infusion fluid through the sensor assembly and catheter into the patient;
• interrupting infusion of the infusion fluid into the patient by operating the infusion pump in a reverse direction, to draw a blood sample from the patient through the catheter and into the sensor assembly;
• monitoring signals produced by first and second sensors of the sensor assembly and detecting changes in the signals indicative of the arrival of the blood sample at the first and second sensors;
• ceasing operation of the infusion pump in the reverse direction in a prescribed manner after detecting the arrival of the blood sample at the first and second sensors and
• monitoring the signals produced by the first and second sensors of the sensor assembly, while the blood sample is in sensing contact with such sensors, to produce measurements of first and second predetermined parameters of the patient's blood.

Apparatus for monitoring a predetermined parameter of a patient's blood while infusing an infusion fluid into the patient, comprising:

• an infusion line and a catheter configured for insertion into a blood vessel of the patient;
• a reversible infusion pump connected between a source of an infusion fluid and the infusion line and catheter;
• a blood chemistry sensor assembly mounted in fluid communication with the infusion line and including a first sensor that provides a signal indicative of a predetermined parameter of any fluid present in the infusion line;
• and
• a controller that operates the infusion pump in a forward direction, to pump the infusion fluid through the infusion line and catheter for infusion into the patient, and that intermittently interrupts its operating of the infusion pump in the forward direction to operate the infusion pump in a rearward direction, to draw a blood sample from the patient through the catheter and infusion line into sensing contact with the first sensor of the blood chemistry sensor assembly;
• wherein the controller further is configured to monitor the signal provided by the first sensor of the blood chemistry sensor assembly and to detect a change in the signal indicative of the arrival of the blood sample at the first sensor;
• wherein the controller, in response to detecting the arrival of the blood sample at the first sensor, ceases its operating of the infusion pump in the rearward direction;
• and wherein the signal produced by the first sensor provides an indication of a predetermined parameter of the patient's blood when the blood sample is in sensing contact with the first sensor.

Apparatus for monitoring a predetermined parameter of patient's blood while infusing an infusion fluid into the patient, comprising:

• an infusion line and a catheter configured for insertion into a blood vessel of the patient;
• a reversible infusion pump connected between a source of an infusion fluid and the infusion line and catheter;
• a blood chemistry senior assembly mounted in flow communication with the infusion line and including first and second sensors that each provide a signal indicative of a different predetermined parameter of any fluid present un the infusion line;
• and
• a controller that operates the infusion pump in a forward direction, to pump the infusion fluid through the infusion line and catheter for infusion into the patient, and that intermittently interrupts its operating of the infusion pump in the forward direction to operate the infusion pump in a rearward direction, to draw a blood sample from the patient through the catheter and infusion line into sensing contact with the first and second sensors of the blood chemistry sensor assembly;
• wherein the controller further is configured to monitor the signals provided by the first and second sensors of the blood chemistry sensor assembly and to detect changes in the signals indicative of the arrival of the blood sample at the first and second sensors;
• wherein the controller ceases its operating of the infusion pump in the rearward direction in a prescribed manner after detecting the arrival of the blood sample at the first and second sensors and the controller thereafter resumes its operating of the pump in the forward direction, to reinfuse the drawn blood sample back into the patient via the infusion tube and catheter;
• and wherein the signal produced by the first sensor provides an indication of a predetermined parameter of the patient's blood when the blood sample is in sensing contact with the first sensor.