A method, comprising: receiving, by a processing system, measurements of at least one blood-related parameter corresponding to a patient undergoing hemodialysis, the at least one blood-related parameter comprising hematocrit and/or relative blood volume; estimating, by the processing system, values of hemodialysis treatment-related parameters by applying a vascular refill model based on the received measurements of the at least one blood-related parameter, wherein the hemodialysis treatment-related parameters are indicative of an effect of vascular refill on the patient caused by the hemodialysis; and determining, by the processing system, based on the estimated values of the hemodialysis treatment-related parameters, a hemodialysis treatment-related operation; providing information regarding the hemodialysis-related operation; wherein the vascular refill model is a two-compartment model based on a first compartment corresponding to blood plasma in the patient's body, a second compartment based on interstitial fluid in the patient's body, and a semi-permeable membrane separating the first compartment and the second compartment; characterized in that the hemodialysis treatment-related parameters include a filtration coefficient L p and a hydrostatic capillary pressure P c; wherein the dynamics of the two-compartment model are described by the following system of equations: { dV p dt = J v + κ − J UF, dc p dt = J s − c p J v + κ − J UF V p, dV i dt = − J v − κ, dc i dt = − J s + c i J v + κ V i, where J v = L p σ a p 1 c p + a p 2 c p 2 − a i 1 c i + a i 2 c i 2 − P c − P i, J s = { J v 1 − σ c i − c p − c i e x − 1 + ακ if J v > 0, ακ if J v = 0, J v 1 − σ c p − c p − c i e x − 1 + ακ if J v < 0, and x = J v 1 − σ PS wherein V p corresponds to the volume of the plasma in the first compartment as a function of time t, J v corresponds to the amount of fluid crossing the membrane at a certain time, k corresponds to a constant lymph flow from interstitium to plasma, J UF corresponds to ultrafiltration rate, J s corresponds to net protein flux, c p corresponds to a protein concentration in plasma as a function of time t, c i corresponds to a protein concentration in interstitium as a function of time t, V i corresponds to the volume of the interstitial fluid in the second compartment as a function of time t, σ corresponds to the osmotic reflection coefficient, P i corresponds to hydrostatic interstitial pressure, α corresponds to a concentration of protein backflow from the lymph, x corresponds to a Peclet number describing convective flux relative to diffusive capacity of the membrane, and PS corresponds to a permeability-surface area product; and wherein a p1, a p2, a i1, and a i2 are parameters of quadratic polynomial approximations of plasma and interstitial colloid osmotic pressures, respectively. receiving, by a processing system, measurements of at least one blood-related parameter corresponding to a patient undergoing hemodialysis, the at least one blood-related parameter comprising hematocrit and/or relative blood volume; estimating, by the processing system, values of hemodialysis treatment-related parameters by applying a vascular refill model based on the received measurements of the at least one blood-related parameter, wherein the hemodialysis treatment-related parameters are indicative of an effect of vascular refill on the patient caused by the hemodialysis; and determining, by the processing system, based on the estimated values of the hemodialysis treatment-related parameters, a hemodialysis treatment-related operation; providing information regarding the hemodialysis-related operation; wherein the vascular refill model is a two-compartment model based on a first compartment corresponding to blood plasma in the patient's body, a second compartment based on interstitial fluid in the patient's body, and a semi-permeable membrane separating the first compartment and the second compartment; characterized in that the hemodialysis treatment-related parameters include a filtration coefficient L p and a hydrostatic capillary pressure P c; wherein the dynamics of the two-compartment model are described by the following system of equations: { dV p dt = J v + κ − J UF, dc p dt = J s − c p J v + κ − J UF V p, dV i dt = − J v − κ, dc i dt = − J s + c i J v + κ V i, where J v = L p σ a p 1 c p + a p 2 c p 2 − a i 1 c i + a i 2 c i 2 − P c − P i, J s = { J v 1 − σ c i − c p − c i e x − 1 + ακ if J v > 0, ακ if J v = 0, J v 1 − σ c p − c p − c i e x − 1 + ακ if J v < 0, and x = J v 1 − σ PS wherein V p corresponds to the volume of the plasma in the first compartment as a function of time t, J v corresponds to the amount of fluid crossing the membrane at a certain time, k corresponds to a constant lymph flow from interstitium to plasma, J UF corresponds to ultrafiltration rate, J s corresponds to net protein flux, c p corresponds to a protein concentration in plasma as a function of time t, c i corresponds to a protein concentration in interstitium as a function of time t, V i corresponds to the volume of the interstitial fluid in the second compartment as a function of time t, σ corresponds to the osmotic reflection coefficient, P i corresponds to hydrostatic interstitial pressure, α corresponds to a concentration of protein backflow from the lymph, x corresponds to a Peclet number describing convective flux relative to diffusive capacity of the membrane, and PS corresponds to a permeability-surface area product; and wherein a p1, a p2, a i1, and a i2 are parameters of quadratic polynomial approximations of plasma and interstitial colloid osmotic pressures, respectively.