(Ivanhoe Newswire) — Administering Ritalin, a commonly used stimulant, to patients recovering from anesthesia sped up the process. This study is the first to demonstrate in mammals what could be a safe and effective way to induce arousal from general anesthesia.
“Currently at the end of a surgical procedure, the anesthesiologist just lets general anesthetic drugs wear off, and the patient regains consciousness,” Emery Brown, MD, PhD, of the MGH Department of Anesthesia, Critical Care and Pain Medicine, senior author of the paper, was quoted as saying. “If these findings can be replicated in humans, it could change the practice of anesthesiology — potentially reducing post-anesthesia complications like delirium and cognitive dysfunction in pediatric and elderly patients.”
General anesthesia has been an essential tool of medicine, but only in recent years have researchers begun to investigate the neurobiology of general anesthesia and to understand exactly how anesthetic drugs produce their effects. Studies by Brown and other scientists have shown that the state of general anesthesia is actually a controlled and reversible coma and bears little similarity to natural sleep. Several neurotransmitter pathways in the brain are known to be generally involved in arousal, but which ones may contribute to recovery from general anesthesia is not yet known.
The stimulant drug methylphenidate (Ritalin), widely used to treat attention-deficit hyperactivity disorder, is known to affect arousal-associated pathways controlled by the neurotransmitters dopamine, norepinephrine and histamine. The current study was designed to see whether methylphenidate could stimulate arousal in rats receiving the anesthetic drug isoflurane. The first experiments showed that animals receiving intravenous methylphenidate five minutes before discontinuation of isoflurane recovered significantly faster than did rats receiving a saline injection. Another experiment showed that methylphenidate induced signs of arousal — movement, standing up, etc. — in animals continuing to receive isoflurane at a dose that would have been sufficient to maintain unconsciousness. EEG readings taken during that experiment showed that brain rhythms associated with arousal returned within 30 seconds of methylphenidate administration. Giving a drug that interferes with the dopamine pathway blocked the arousal effects of methylphenidate, supporting the role of that pathway in the drug’s effects.
“Our results tell us that, even though we don’t yet know the precise mechanisms underlying general anesthesia, we can overcome its effects by activating arousal pathways,” Ken Solt, MD, of the MGH Department of Anesthesia, Critical Care and Pain Medicine, the paper’s lead and corresponding author, was quoted as saying. “Instead of the traditional paradigm of reversing drug actions at the molecular level, methylphenidate acts at the level of neural circuits to overcome the effects of isoflurane. Since we still know very little about the pathways involved in general anesthesia, we will be testing the actions of methylphenidate with other anesthetic agents to see if these arousal effects are broadly applicable.”
SOURCE: Anesthesia, published online September 21, 2011
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