Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2000-10-13
2003-05-20
Walberg, Teresa (Department: 3742)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S066000, C607S068000, C607S070000, C607S139000, C607S072000, C607S140000
Reexamination Certificate
active
06567702
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to generating analgesic effects by Transcranial Electrical Stimulation (TCES). More particularly, it relates to specific operating conditions for TCES and a method for using animal models to determine the optimal operating conditions.
BACKGROUND ART
The use of electrical currents for the purpose of producing narcosis or analgesia was pioneered by the French physiologist Leduc nearly 100 years ago. Over the next 70 years, several attempts were made to produce and maintain a state of general anesthesia by administering different parameters of electrical currents, applied to the skin of the subject's head (i.e., transcranially and transcutaneously). However, due to the high intensity of current required to induce general anesthesia, these efforts were abandoned and superseded by attempts to produce analgesia, rather than general anesthesia, by application of electrical currents. Different types of Transcranial Electrical Stimulation (TCES) are suggested in the literature under a wide variety of names, including Cranial Electrotherapy Stimulation (CES), Low Current Electrostimulation, Auricular Microstimulation, and others [Limoge, 1999]. However, only French [Limoge, 1975] and Russian [Lebedev, 1988] currents are thought to produce an analgesic effect powerful enough to be utilized in clinical anesthesiology. Limoge currents consist of high frequency (166 kHz) intermittent bursts of bidirectionally balanced current “packed” into trains. The current is applied transcranially and transcutaneously at 100 Hz for 4 msec at 6 msec intervals. These currents are described in part in U.S. Pat. No. 3,835,833, issued to Limoge. TCES with Limoge currents is applied through a frontal cathode and a pair of anodes located at the level of mastoid bones [Mantz, 1992]. TCES with Limoge current has been successfully used as part of an anesthetic management in a wide variety of surgical cases. It has been shown to:
increase the potency of nitrous oxide in humans by 30-40% [Stanley, 1982A];
reduce the need for opiates during neuroleptanesthesia by 50-80% [Stanley, 1982B];
potentiate opioid-induced analgesia in rats [Dougherty, 1989]; and
decrease minimum alveolar concentration (MAC) of halothane in rats [Mantz, 1992].
In the mid-1980's, Russian investigators at the Pavlov Institute of Physiology in St. Petersburg determined parameters of TCES that produce a more profound analgesic effect than that observed with TCES with Limoge currents [Lebedev, 1983, 1988A, 1988B; Kovalev, 1987]. The major difference from Limoge currents was the use of a combination (2:1 or 3:1 ratio) of direct (DC) and alternating current (AC) of lower frequency (77-78Hz). The resultant current is also applied through frontal cathode and retromastoid anodes. The analgesic effect of “Lebedev current” was thought to be mediated by the AC, while the DC potentiated its action and eliminated the inherent seizure-provoking properties of AC [Rychkova, 1994]. This method of TCES has been successfully used in Russia in thousands of patients for different types of surgery, including cardiothoracic procedures, and in different age groups, including pediatrics [Katsnelson, 1987, 1989; Kartavkin, 1987; Zamiatnina, 1987]. So profound was the analgesic effect of TCES suggested by Russian researchers that intraoperative use of opioid narcotics in some cases could be completely avoided, and the analgesic effect extended into the immediate postoperative period [Lebedev, 1989]. This method has also been used successfully for treatment of chronic pain syndromes in awake subjects [Skorometz, 1987; Akimov, 1987; Gurchin, 1987; Kasimova, 1987]. Recently, Lebedev has restricted TCES stimulating parameters to administration of AC only, citing the same analgesic effect as with the combination of DC and AC [Lebedev, 1998]; however, no experimental data has been published to support that claim.
TCES with either Limoge or Lebedev current facilitates rapid recovery from general anesthesia without side effects such as respiratory depression, nausea and vomiting, itching, urinary retention, and immunosuppression [Stinus, 1990; Katsnelson, 1987]. Furthermore, both TCES modalities have been used successfully in the management of alcohol and opiate withdrawal states in awake patients [Auricombe, 1990; Krupitski, 1991]. Lebedev current has also been shown to promote tissue repair and decrease the incidence of surgical wound infections [Lebedev, 1998].
Despite these encouraging results, good controlled clinical studies are lacking. In addition, TCES studies in rats either failed to document prolongation of tail flick latency (TFL) with Limoge current [Stinus, 1990], or TFL responses were not studied [Lebedev, 1988]. TFL test is a standard measure of analgesia production in rats and mice, and correlates well with analgesic potency of drugs in humans. Lack of good controlled studies and consensus among researchers on the “best” TCES stimulation parameters has contributed to the conflicting results between laboratories regarding the efficacy of TCES and the TCES mechanism of action [Alling, 1990]. Broad disagreement exists about optimal current intensity, electrode positioning and configuration, signal waveform, and frequency. However, it has been established that frequency is the most important variable in determining efficacy of analgesia production. It is also agreed that a tolerance effect may be established relatively rapidly: after a short time period, analgesic effects are no longer observed. In order to re-establish analgesia, the signal must be adjusted periodically.
Various researchers have developed different signal parameters for TCES. A series of U.S. patents have been issued to Kastrubin et al. and Nozhnikov et al., including U.S. Pat. Nos. 3,989,051; 4,121,593; 4,140,133; 4,185,640; 4,334,525; 4,383,522; and 4,724,841. Their devices, generally used for electroanesthesia, generate square pulses of varied current, duration, and frequency. Recommended frequencies are above 100 Hz, and stimulation is by a combination of direct and alternating current. The combination of AC and DC is also included in an electrotherapy method disclosed in U.S. Pat. No. 5,387,231, issued to Sporer. This method is primarily for pain relief through muscle relaxation and uses frequencies typically below 15 Hz and microampere current value that is much lower than typically used in TCES.
Other TCES parameters have been used for a variety of different applications. For example, currents somewhat similar to Limoge currents are employed for treating headaches, as described in U.S. Pat. Nos. 4,844,075 and 4,856,526, both issued to Liss et al. Other methods involve applying trains of pulsed current separated by off periods, as described in U.S. Pat. No. 4,646,744, issued to Capel, or trains of different frequencies, U.S. Pat. No. 5,593,432, issued to Crowther et al., in order to avoid acclimation of the nerves to the imposed signal. Both of these methods are directed toward drug addiction recovery.
Mechanism of TCES action remains unknown. Perhaps the most plausible explanation is that the electrical current causes depolarization of nerve terminals with the release of inhibitory neurotransmitter(s), interrupting nociceptive (pain receptor-related) processing. The identity of mediating neurotransmitter(s) and nociceptive pathway(s) involved has been widely debated; opioids, serotonin, and norepinephrine have each been implicated as a possible mechanism for the analgesic response to TCES [Airapetov, 1987; Lebedev, 19988A; Malin, 1989; Mantz, 1992].
Thorough studies are needed both to better understand the mechanism of TCES and to correctly determine the optimal operating conditions. Absent a neurobiologic substrate to explain observed analgesia, mainstream medical opinion remains skeptical, and TCES continues to be mor
Maze Mervyn
Nekhendzy Vladimir
Fuqua Shawntina
Lumen Intellectual Property Services Inc.
The Board of Trustees of the Leland Stanford Junior University
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