Fluid sampling system

A method for sampling body fluid from a patient or animal comprising the steps of:

• providing and extending a sampling lumen from a first sample site of the patient or animal to a first pump for withdrawing a fluid sample from the patient or animal;
• withdrawing, continuously or periodically during time interval Δt, the fluid sample through the sampling lumen from the first sample site of the patient or animal;
• automatically transferring at least part of the fluid sample to a sampling device for storage and/or analysis;
• providing and extending a return lumen from the first pump to a second sample site of the patient or animal;
• simultaneously returning to the patient or animal part of the sample fluid not transferred to the sampling device through the return lumen to the second sample site of the patient or animal, the second sample site being different than the first sample site and the sampling lumen being distinct from the return lumen;
• providing and extending a supply lumen from a second pump to or proximate the first sample site of the patient or animal;
• and
• providing an active substance through the supply lumen at or proximate the first sample site during time interval Δt, the active substance being an internal reference for calibrating a sensor or a reference for determining a concentration of another substance,
• wherein the method for sampling body fluid is configured to allow mixing of the active substance provided at and/or proximate the first sample site with the fluid of the patient or animal, and further configured to withdraw the mixture of the fluid of the patient or animal and the active substance from the patient or animal at the first sample site.

A patient or animal fluid sampling system, comprising;

• a housing;
• a first pump operable to withdraw a fluid sample from a first sample site of the patient or animal;
• a sampling lumen extending from the first sample site of the patient or animal to the first pump for withdrawing the fluid sample from the patient or animal;
• a return lumen extending from the first pump to a second sample site of the patient or animal for returning at least part of the fluid sample to the second sample site, the first pump operable to return at least part of the fluid sample through the return lumen, the second sample site being different than the first sample site;
• a valve directing the fluid sample withdrawn from the patient or animal by the first pump to a sampling device and to the second sample site, the first pump operable to return the fluid sample directed by the valve through the return lumen to the second sample site of the patient or animal or to the sampling device;
• a supply lumen for providing an active substance at and/or proximate the first sample site of the patient or animal;
• a second pump, the supply lumen extending from the second pump to and/or proximate the first sample site, the second pump being operable to provide the active substance through the supply lumen;
• a connection to a reservoir containing the active substance, the active substance being an anti-coagulant, a flushing fluid, an internal reference for calibrating a sensor, or a reference for determining a concentration of another substance;
• and
• at least one energy source operable to energize at least the first pump and second pump;
• wherein the fluid sampling system is adapted for withdrawing the fluid sample simultaneously with returning the fluid sample to the patient or animal, and the fluid sampling system is configured to allow mixing of the active substance provided at and/or proximate the first sample site with the fluid of the patient or animal, and further configured to withdraw the mixture of the fluid of the patient or animal and the active substance from the patient or animal at the first sample site.