Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
2001-06-20
2004-02-03
Gibson, Roy D. (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S108000
Reexamination Certificate
active
06685731
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and systems for improving cardiovascular parameters and cardiac markers of patients undergoing medical procedures involving general anesthesia. In particular, the present invention relates to methods and systems for improving cardiovascular parameters, in particular cardiac index (CI), systemic vascular resistance (SVR), and the circulating level of the cardiac protein Troponin I (cTnI) of patients during or after open heart surgery.
BACKGROUND OF THE INVENTION
There are many surgical procedures that are performed under general anesthesia. One major undesired consequence of general anesthesia is hypothermia, which is a reduction of the body's core temperature. Hypothermia causes physiologic diseration of all major body functions including that of cardiovascular and respiratory systems, nerve conduction, mental acuity, neuromuscular reaction time and metabolic rate. Countering these side effects is a major challenge both during the operation and particularly in the postoperative procedures and in intensive care units.
In open-heart surgeries, the treated patient is connected to a heart-lung machine during the open-heart phase of the surgery. However, during the period preceding this phase, it is important that the various physiological functions of the body will be in as best as possible condition prior to connection to the heart-lung machine. However, typically the cardiac index of the patient deteriorates during this period to levels below desired. That has an effect on the eventual recovery of the patient after the surgical procedure.
Generally, reduction in cardiac index is a major problem during surgical procedures performed under general anesthesia.
GENERAL DESCRIPTION OF THE INVENTION
The present invention provides a method and system, which bring to improvement in cardiovascular parameters and a cardiac protein marker of a patient undergoing a medical procedure under general anesthesia. This is a result, in accordance with the invention, from proper control of the body's core temperature. This control is achieved by a system comprising a heat exchanger which is in contact with the external body surface and employing a heating regime which takes into consideration the dynamic heat transfer properties of the body.
The term “improvement” or “improving” when relating to cardiovascular parameters means to denote improvement in one or more of such measured parameters as compared to patients undergoing a similar procedure with the body heat not being controlled in a manner as provided for in accordance with the invention. The purpose of such improvement is in essence to maintain the cardiovascular parameters as close as possible to normal, namely similar the level of such parameters in the individual prior to undergoing the surgical procedure.
The term “cardiovascular parameters” is used herein to denote measurable parameters of the cardiovascular system used to determine proper (or improper) operation of the heart and the vasculature. A very important cardiovascular parameter is the “cardiac output”. The cardiac output is a measure of the pumping capacity of the heart (typically measured in liters per minute), and is an important measure of proper heart function. Usually the Cardiac Output is expressed in relation to the body surface area (BSA) as the Cardiac Index—L/Min/m
2
. Another cardiovascular parameter is the systemic vascular resistance (SVR)—dynes-sec-cm
−5
which represents the cardiac afterload and is usually elevated as a result of hypothermia. This eventually necessitates augmentation of cardiac work to provide perfusion to body tissues. Cardiac troponine I (cTn-I) is a regulatory protein specific for the myocardium, the level of which is measured in the serum. The cTn-I level typically rises as a result of damage to the myocardium. cTn-I levels may significantly rise during a cardio-pulmonary bypass surgery.
The term “core temperature” is used herein to denote the temperature within the body, namely that of the internal organs and tissue. Core temperature is typically measured through the rectum but may also be measured by inserting probes through a variety of other body cavities, e.g. mouth, nasal, esophageal, bladder or ear temperature probes. The term “surface temperature” will be used to denote the temperature of the external body surface (which may be that of the skin or, where the skin has been damaged, e.g. in burn injury, that of the most external layers). It should be noted that the surface temperature may vary between different body portions. The surface temperature may be measured by a variety of temperature probes including, for example, an infrared sensor measuring infrared emission from a specific skin portion, probes attached to the skin such as thermal-couple devices, thermister, etc.
In accordance with a first aspect of the invention there is provided a method for improving cardiac paramaters, including, but not limited to cardiac index, systemic vascular resistance and Cardiac Troponin I in a patient undergoing a medical procedure under general anesthesia, comprising: contacting a substantial portion of the patient's external body surface, without covering the areas where surgical procedures are performed with a heat exchanger which can transfer heat to or absorb heat from the body surface; continuously measuring parameters from the body including at least the actual body core temperature (aBCT); and in a processor, receiving data signals corresponding to the measured parameters, comparing the aBCT with a desired body core temperature (dBCT) needed in order to maintain a desired cardiovascular parameters based on the aBCT/dBCT difference, emitting a control signal to control heat transfer properties of said heat exchanger.
In accordance with another aspect of the invention there is provided a system for improving the cardiac parameters, including, but not limited to cardiac index, systemic vascular resistance and the levels of Cardiac Troponin I of patients undergoing medical treatment under general anesthesia, the system comprising:
a processor controlled heating/cooling unit coupled to a flexible heat exchanger for contacting substantial portions of a patient's body surface and for transferring heat to or removing heat from said portions, said cooling unit having the ability to change heat transfer properties of the heat exchanger with said substantial portions:
at least one BCT-sensing device for measuring the patient's aBCT and emitting an aBCT data signal; and
a control module for receiving data signals from measuring devices, comprising the aBCT data signal, and for emitting a control signal for controlling heat exchange properties of said heat exchanger as a function of the data signals and a dBCT needed in order to maintain a desired cardiovascular parameters.
The invention yields an improvement of cardiovascular parameters and the after load, which is a consequence of the controlled heating-induced vasodilatation or reduction in the vasoconstriction.
In accordance with one preferred embodiment of the invention the system comprises at least one sensing device for measuring a parameter indicative of the heat transfer dynamics (HTD) between the body's surface and the body's core. Thus, in accordance with this embodiment, such a parameter is continuously measured and a data signal corresponding to this parameter emitted from the device is fed into said processor, and this signal is factored in the control signal emitted by the processor.
The term “substantial portion of the body surface” means to denote such a portion which is sufficient to achieve a sufficient degree of heat exchange to yield the dBCT. Typically, such a substantial portion will be at least 40%, preferably at least 50% of the body's surface.
The heat exchanger may either be provided with an internal heat or cold producing capability e.g. including a Peltier effects modules, or the heat exchanger may be linked to at least one source of cold and/or hot fluid, which
Kushnir Igal
Nesher Nachum
Gibson Roy D.
Ladas & Parry
M.T.R.E. Advanced Technologies Ltd.
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