A portable hemodynamic monitoring device comprising: a housing having a bottom surface configured to interface with a skin surface of an individual and to be fixed in place on the skin surface, the housing configured for removable coupling to a body part of the individual, the body part including at least one vessel of interest; an ultrasound unit coupled to the housing and adapted for adducing ultrasonic waves into the at least one vessel of interest in a continuous beam or programmed pulse repetition frequency, the ultrasound unit including: at least one transducer pair adapted to detect continuously or in accordance to the programmed pulse repetition frequency reflected ultrasonic waves derived at least in part from the produced ultrasonic waves directed at the at least one vessel of interest and oriented such that, in concert, the at least one transducer pair produces the ultrasonic waves at an angle of incidence between about 25 degrees to about 60 degrees in respect of a plane of the skin surface of the individual over the at least one vessel of interest; a processor configured for extracting hemodynamic parameters from one or more characteristics of the detected reflected ultrasonic waves in real-time or near real-time by applying a signal processing routine; a storage for storing the extracted one or more hemodynamic parameters; and a sensory output device adapted for providing feedback on a quality of the extracted hemodynamic parameters, the sensory output device including at least one of (i) a graphical display and (ii) an auditory display wherein the processor is configured to execute program instructions to: determine the individual's pre-challenge velocity time integral of the blood flow in the vessel of interest; prompt an operator for a fluid challenge; detect and/or calculate a post-challenge velocity time integral of the blood flow in the vessel of interest; and deliver an assessment of the individual's fluid responsiveness. a housing having a bottom surface configured to interface with a skin surface of an individual and to be fixed in place on the skin surface, the housing configured for removable coupling to a body part of the individual, the body part including at least one vessel of interest; an ultrasound unit coupled to the housing and adapted for adducing ultrasonic waves into the at least one vessel of interest in a continuous beam or programmed pulse repetition frequency, the ultrasound unit including: at least one transducer pair adapted to detect continuously or in accordance to the programmed pulse repetition frequency reflected ultrasonic waves derived at least in part from the produced ultrasonic waves directed at the at least one vessel of interest and oriented such that, in concert, the at least one transducer pair produces the ultrasonic waves at an angle of incidence between about 25 degrees to about 60 degrees in respect of a plane of the skin surface of the individual over the at least one vessel of interest; a processor configured for extracting hemodynamic parameters from one or more characteristics of the detected reflected ultrasonic waves in real-time or near real-time by applying a signal processing routine; a storage for storing the extracted one or more hemodynamic parameters; and a sensory output device adapted for providing feedback on a quality of the extracted hemodynamic parameters, the sensory output device including at least one of (i) a graphical display and (ii) an auditory display wherein the processor is configured to execute program instructions to: determine the individual's pre-challenge velocity time integral of the blood flow in the vessel of interest; prompt an operator for a fluid challenge; detect and/or calculate a post-challenge velocity time integral of the blood flow in the vessel of interest; and deliver an assessment of the individual's fluid responsiveness. determine the individual's pre-challenge velocity time integral of the blood flow in the vessel of interest; prompt an operator for a fluid challenge; detect and/or calculate a post-challenge velocity time integral of the blood flow in the vessel of interest; and deliver an assessment of the individual's fluid responsiveness.