Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Patent
1997-10-10
2000-07-11
Coggins, Wynn Wood
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
604190, 604236, A61M 100
Patent
active
060865598
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method and a device for pressure-controllable handling of a fluid. The device makes possible, in particular, even and steadied, in particular pressure-controlled, injection of a fluid, which can be a liquid or a gas. The device can also be used in different ways as a probe for inserting cannulas and when placing catheters. In particular, the invention relates to the further development of a syringe for medical purposes. A preferred field of application is anaesthesia.
SUMMARY OF THE INVENTION
Known devices for handling a fluid, in particular syringes, are provided with a container for receipt and delivery of a fluid, with a plunger which can be pushed into the container, sealed with respect to the internal wall of the container by sealing means. They are used mostly where a fluid is stored for a certain time before being used. Apart from medical applications, this can be a device for lubricating components, or also a device for precise pressure-controlled dosage of a fluid. In the case of such applications, in addition to the amount to be dosed, the pressure of the fluid when injected, the change in its pressure, or the speed of the fluid injection are of importance. These parameters must often be adjusted and monitored in order, for example, to prevent damage when the fluid is injected.
The operation and the use of a known device will hereinafter be described with reference to a syringe, using the example of spinal anaesthesia.
A usually suddenly occurring drop in blood pressure, with reflex tachycardia--due to expansion of blood vessels as a result of the blockade of pre-ganglion sympathetic nerve fibres (=sympatholytic action) often observed during spinal anaesthesia is an undesirable and occasionally dangerous complication in this anaesthetic procedure. All anaesthetists would therefore like to see spinal anaesthesia which is more controllable and the distribution of which can be better calculated, and the improved circulatory stability which can be obtained in this way particularly with patients with cardiac and circulatory diseases.
The sole use of so-called hyperbaric local anaesthetics, which are made heavier than the fluid by the addition of glucose, and are consequently preferably distributed in the deeper regions in contrast to isobaric local anaesthesia, does not lead--as was expected--to better control of a spinal anaesthesia in clinical practice.
Some in-vitro tests have shown that the current standard injection techniques using thin spinal needles cause significant eddying of the local anaesthetic in the fluid space, resulting in complete or at least widespread mixing, even of hyperbaric local anaesthesia, with the fluid. These injection techniques are not suitable for underlying the fluid with a hyperbaric local anaesthetic with little, or without eddying and to thus provide a necessary precondition for effecting the distribution of the anaesthetic by suitable manoeuvring of the patient's position. The injection stream resulting from the high speeds of injection can, moreover, result in neural irritation or even trauma.
In particular, a slow and even injection using a thin spinal needle, with which a turbulent injection stream occurs more rapidly at the same speed of injection compared to thicker needles, can prevent eddying of the local anaesthetic in the fluid and possible neural irritation or trauma by the injection stream. When using thin spinal needles such a slow and even injection is not possible manually with a conventional syringe, as minimal changes in pressure on the syringe plunger (=changes in the pressure effected by the fingers) results in unevenness in the injection stream, which causes eddies of the local anaesthetic in the fluid.
It is known that with a slow injection a certain steadying of the injection speed can be obtained by pneumatic dampening. For this, in addition to the local anaesthetic, several milliliters of air are drawn up into the syringe; by means of a three-way tap (90 degree offset) the syringe is
REFERENCES:
patent: 4624659 (1986-11-01), Goldberg et al.
patent: 4660569 (1987-04-01), Etherington
Beard William
Bell Catherine L.
Coggins Wynn Wood
Nguyen A. T.
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