Surgery – Means for introducing or removing material from body for... – Gas application
Reexamination Certificate
1998-03-10
2001-12-11
Mendez, Manuel (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Gas application
Reexamination Certificate
active
06328708
ABSTRACT:
The invention relates to a device which can be used to control the anaesthesia, analgesia and/or sedation of a patient.
Control is understood here as meaning that a patient's condition (anaesthesia, analgesia and/or sedation) can be changed in the shortest possible time from the patient's actual condition to a required or desired condition. This means e.g. that, in the case of anaesthesia, the conditions (1) analgesia, (2) loss of consciousness and (3) muscular relaxation are reached in the shortest possible time and that the transition from the anaesthetized condition to full consciousness proceeds rapidly and without complications. Control also means that, once a condition has been reached, it is kept stable over long periods (hours to days). This means that, even under drastically changing circumstances, the condition is maintained and subsequent control can be effected without problems.
If such control is to take place reliably and without complications, the active substance must first meet certain requirements. For example, one feature of the active substance must be a rapid onset of action (a few seconds). On the other hand, however, the action must also wear of f rapidly (for example 1-3 minutes; reversibility; all defunctionalization symptoms must disappear when anaesthesia has ended). A further requirement is an adequate (for example anaesthesio-logical) safety margin. The concentration required to achieve the desired condition (for example loss of pain sensation and loss of consciousness) should be several times lower than that which damages the patient's vital functions. Finally, however, the controllability is also a decisive factor, i.e. the condition can be deepened, relieved or ended by varying the concentration or the infusion rate. In the case of longer-lasting operations (e.g. operations which take more than 10 seconds), an additional requirement is that the active substance can be administered in higher concentrations over a longer period of time without causing appreciable side effects.
Although one of the remarkable features of the intravenous anaesthetics in current use is an immediate onset of action, they regularly exhibit a host of disadvantages. It should be emphasized that propofol and etomidate, in particular, have no analgesic action and are difficult to control. Other disadvantages of these injectable anaesthetics are side effects which are difficult to assess (for example drop in blood pressure, bradycardia, rigidity, allergic reactions) and in some cases serious contraindications. Finally, total intravenous anaesthesia (TIVA) with propofol also frequently results in protracted waking and disorientation, especially after longer periods of anaesthesia.
Thus it is seen that the presently known intravenous active substances do not meet the requirements.
Active substance combinations according to the state of the art do not represent a solution to this problem. In the case of anaesthetics in particular, it is known that combinations produce pharmacokinetic and pharmacodynamic interactions which very definitely cannot be adequately controlled in the maintenance of the anaesthesia. As a consequence of the different pharmacokinetics and pharmacodynamics of the respective active substances at a given moment during the anaesthesia, it is not possible correctly to adjust the concentration and/or the infusion rate. In other words, where active substance combinations are used in an intravenous preparation, the overall action virtually never corresponds to the sum of the individual actions. Such combination preparations therefore fail to meet the requirement of controllability.
There is consequently a need for a substance, to be used as a single substance or in combination with other active substances, which meets the requirements formulated above.
Very precise control of anaesthesia, especially the maintenance of anaesthesia, requires that a particular concentration of active substance in a patient's blood be unambiguously measurable at any time. In the case of simple and easily comprehensible operating procedures and known pharmacokinetics, limited control is possible by means of multistage infusion regimes, for example with propofol. However, such regimes are inflexible and are unsuitable especially when the active substance has to be administered in a controlled manner under changing anaesthetic and operative circumstances.
Because of the lack of flexibility of manual infusion regimes and the highly complex mathematical models for the pharmacokinetics of the known active substances, computer controlled infusion systems have been developed. These computer systems are programmed with a mathematical solution for the pharmacokinetic model of a patient in respect of the active substance used, for example propofol. The computer then calculates the infusion rate which is necessary to achieve and maintain a theoretical target blood concentration. This target value is determined and adjusted e.g. by an anaesthetist. The computer then also controls the infusion rate at which the active substance is administered to a patient. This type of control is also known as target controlled infusion (TCI).
However, there is always uncertainty as regards the concentration of the active substance because the pharmacokinetics differ from patient to patient. It has in fact been observed that very different target concentrations have been determined by anaesthetists in practice. It follows from this that there is a considerable need for a system which can adjust or control a particular condition during anaesthesia as a function of a patient's actual requirements during an operation. The substantial differences in the target concentrations of the active substance in the blood, and the appreciable variance observed in the course of operations with different patients and the drugs additionally used, lead to the conclusion that TCI does not yet meet the requirements of effective control in every respect.
Systems are currently under development which make it possible to adjust the degree of anaesthesia more precisely. These are closed circuit systems in which the administration of the injectable anaesthetic is controlled as a function of the depth of anaesthesia which is actually measured (so-called closed loop anaesthesia systems (CLAN)). However, these systems require a considerable expenditure on equipment in order precisely to determine the action of the anaesthetic, i.e. the depth of the anaesthesia, in a patient.
In summary, there is therefore not only a need for a substance with an anaesthetic, analgesic and sedative action which meets all the requirements for use in a true control system (TCI or CLAN), as previously discussed, but also a need for simpler systems which can also function without complex computer programs and/or expensive measuring instruments (as well as evaluation programs) and which, in contrast to the known systems, reflect the true condition (for example true concentration in the blood).
The object of the invention consists in providing a device (or facility) which makes it possible to ensure controlled anaesthesia, analgesia and/or sedation.
This object is achieved by means of a device which is characterized in that it comprises a container holding a liquid preparation which contains a lipophilic inert gas in an amount effective as an anaesthetic, analgesic or sedative, and means for the controlled administration of the preparation to the patient. The purpose of this device is to administer an inert gas-containing preparation to a patient intravenously or arterially in a time controlled manner. “In a time controlled manner” means here that the condition required for example in an operative procedure (anaesthesia, analgesia and/or sedation) can always be precisely controlled over a given period of time, for example 2 minutes or even 1 to 2 hours or more (up to days). This is achieved for example by aiming for a particular endtidal xenon concentration, which corresponds to the concentration in the blood. In the very simplest case, the
Burns Doane Swecker & Mathis L.L.P.
Mendez Manuel
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