Korean J Pain.  2014 Oct;27(4):313-320. 10.3344/kjp.2014.27.4.313.

Safe Sedation and Hypnosis using Dexmedetomidine for Minimally Invasive Spine Surgery in a Prone Position

• Kim KH

• KMID: 1802496
• DOI: http://doi.org/10.3344/kjp.2014.27.4.313

Abstract

Dexmedetomidine, an imidazoline compound, is a highly selective alpha2-adrenoceptor agonist with sympatholytic, sedative, amnestic, and analgesic properties. In order to minimize the patients' pain and anxiety during minimally invasive spine surgery (MISS) when compared to conventional surgery under general anesthesia, an adequate conscious sedation (CS) or monitored anesthetic care (MAC) should be provided. Commonly used intravenous sedatives and hypnotics, such as midazolam and propofol, are not suitable for operations in a prone position due to undesired respiratory depression. Dexmedetomidine converges on an endogenous non-rapid eye movement (NREM) sleep-promoting pathway to exert its sedative effects. The great merit of dexmedetomidine for CS or MAC is the ability of the operator to recognize nerve damage during percutaneous endoscopic lumbar discectomy, a representative MISS. However, there are 2 shortcomings for dexmedetomidine in MISS: hypotension/bradycardia and delayed emergence. Its hypotension/bradycardiac effects can be prevented by ketamine intraoperatively. Using atipamezole (an alpha2-adrenoceptor antagonist) might allow doctors to control the rate of recovery from procedural sedation in the future. MAC, with other analgesics such as ketorolac and opioids, creates ideal conditions for MISS. In conclusion, dexmedetomidine provides a favorable surgical condition in patients receiving MISS in a prone position due to its unique properties of conscious sedation followed by unconscious hypnosis with analgesia. However, no respiratory depression occurs based on the dexmedetomidine-related endogenous sleep pathways involves the inhibition of the locus coeruleus in the pons, which facilitates VLPO firing in the anterior hypothalamus.

Keyword

adrenergic alpha-2 receptor agonists; conscious sedation; dexmedetomidine; minimally invasive surgical procedures; percutaneous discectomy

MeSH Terms

Adrenergic alpha-2 Receptor Agonists
Analgesia
Analgesics
Analgesics, Opioid
Anesthesia, General
Anxiety
Conscious Sedation
Dexmedetomidine*
Diskectomy
Diskectomy, Percutaneous
Eye Movements
Fires
Humans
Hypnosis*
Hypnotics and Sedatives
Hypothalamus, Anterior
Ketamine
Ketorolac
Locus Coeruleus
Midazolam
Pons
Prone Position*
Propofol
Respiratory Insufficiency
Spine*
Surgical Procedures, Minimally Invasive
Adrenergic alpha-2 Receptor Agonists
Analgesics
Analgesics, Opioid
Dexmedetomidine
Hypnotics and Sedatives
Ketamine
Ketorolac
Midazolam
Propofol

Figure

• 

  Fig. 1 Sedative and hypnotic mechanism of dexmedetomidine-related endogenous sleep pathways. If the arousal-promoting neurotransmitters - including histamine, as well as 5-hydroxytryptamine (5-HT), orexin (ORX, hypocretin), norepinephrine (NE), and acetylcholine (Ach) - are released from the tuberomammillary nucleus (TMN), dorsal raphe nucleus (DRN), perifornical area (PFA), locus coeruleus (LC), and laterodorsal tegmental nuclei (LDTN) and pedunculopontine tegmental nuclei (PPTN), respectively, into the cortex, wakefulness is promoted. When the wakeful state is converted to the NREM sleep state, the most characteristic feature of neurotransmitters in the brain is an increased release of galanin (GAL) and gamma-aminobutyric acid (GABA) into the TMN, LC, DRN, PFA, and LDTN/PPTN from the ventrolateral preoptic nucleus (VLPO). And other notable neurotransmitter changes are a decreased release of ORX from the PFA into the TMN and VLPO and a decreased release of histamine from the TMN into the VLPO and PFA. The release of all 5 arousal-promoting neurotransmitters decreases in the cortex as well.

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