The aim of this trial is to investigate if dexmedetomidine prolongs the duration of an ulnar nerve block. By using healthy volunteers the investigators can perform bilateral ulnar nerve blocks and thereby control for a systemic effect to clarify if the effect is actually peripheral or systemic. The investigators hypothesis is that dexmedetomidine as an adjunct to a local anaesthetic prolongs the duration of a peripheral nerve block by a peripheral mechanism.
Background: Efficient pain management promoting mobilization and convalescence is essential in an ideal perioperative course. Regional nerve blocks are a central element in postoperative regimes for many patients and it is therefore important that these nerve blocks are both long lasting and efficient. This trial will investigate whether it is possible to optimize the postoperative pain management when adding dexmedetomidine to the local anaesthetic ropivacaine in peripheral nerve blocks. The prolonging effect of using dexmedetomidine as adjunct in peripheral nerve blocks have been investigated in several studies. However, it remains uncertain whether the effect is mediated by a systemic-, a peripheral- or a combined systemic/peripheral mechanism. In this trial the adjuvating effect of dexmedetomidine will be investigated using an ulnar nerve block. Method: The participants will attend two trial days. On one trial day the volunteers will receive bilateral ulnar nerve blocks. In one arm they will receive the local anaesthetic ropivacaine 4ml 5mg/ml and placebo (saline) and in the other arm ropivacaine 4ml 5mg/ml and dexmedetomidine 100μg. The dexmedetomidine administered perineurally is absorbed and redistributed and will influence the two nerve blocks equally systemically. On the other trial day the participants will receive ropivacaine 4ml 5mg/ml and placebo (saline) and in the other arm ropivacaine 4ml 7.5mg/ml and placebo (saline). The allocation is blinded to volunteer and investigator. In this setup we therefore have a perineural- and a systemic dexmedetomidine group and also a placebo group , and a group testing if higher doses of local anesthetics will prolong the duration of a nerve block. The duration of the nerve block will be measured by 3 different tests: pinprick, temperature test (alcohol) and Pain during tonic heat stimulation. All tests are validated within pain research.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
QUADRUPLE
Enrollment
22
Dexmedetomidine is added perineurally on one side and will influence the nerve block perineurally on this side. Dexmedetomidine is also absorbed and redistributed systemically and will influence the opposite ulnar nerve block systemically.
Ropivacaine is used in 5mg/ml in the perineural, systemic and placebo nerve blocks.
In the high dose ropivacaine group a ropivacaine concentration of 7.5mg/ml is used.
Department of Anesthesiology Zealand University Hospital
Køge, Denmark
RECRUITINGDifference in duration of sensory nerve block assessed by mechanical discrimination (pinprick) between perineural dexmedetomidine and placebo
Duration of sensory nerve block measured by mechanical discrimination (pinprick) defined as time from block performance (removal of the needle) until the needle feels sharp again.
Time frame: 0-36 hours
Difference in duration of sensory nerve block assessed by mechanical discrimination (pinprick) between systemic dexmedetomidine and placebo
Duration of sensory nerve block measured by mechanical discrimination (pinprick) defined as time from block performance (removal of the needle) until the needle feels sharp again.
Time frame: 0-36 hours
Difference in duration of sensory nerve block assessed by mechanical discrimination (pinprick) between systemic dexmedetomidine and perineural dexmedetomidine
Duration of sensory nerve block measured by mechanical discrimination (pinprick) defined as time from block performance (removal of the needle) until the needle feels sharp again.
Time frame: 0-36 hours
Difference in duration of sensory nerve block assessed by mechanical discrimination (pinprick) between high dose ropivacaine and placebo
Duration of sensory nerve block measured by mechanical discrimination (pinprick) defined as time from block performance (removal of the needle) until the needle feels sharp again.
Time frame: 0-36 hours
Difference in duration of sensory nerve block assessed by temperature discrimination between perineural dexmedetomidine and placebo
Duration of sensory nerve block measured by temperature discrimination defined as time from block performance (removal of the needle) until the stimulation with an alcohol swab feels cold again.
Time frame: 0-36 hours
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Dexmedetomidine administered perineurally on one side is absorbed and redistributed systemically and will influence the opposite ulnar nerve block systemically.
placebo (saline) is administered perineurally in all but the perineural group.
Difference in duration of sensory nerve block assessed by temperature discrimination between systemic dexmedetomidine and placebo
Duration of sensory nerve block measured by temperature discrimination defined as time from block performance (removal of the needle) until the stimulation with an alcohol swab feels cold again.
Time frame: 0-36 hours
Difference in duration of sensory nerve block assessed by temperature discrimination between systemic dexmedetomidine and perineural dexmedetomidine
Duration of sensory nerve block measured by temperature discrimination defined as time from block performance (removal of the needle) until the stimulation with an alcohol swab feels cold again.
Time frame: 0-36 hours
Difference in duration of sensory nerve block assessed by temperature discrimination between high dose ropivacaine and placebo
Duration of sensory nerve block measured by temperature discrimination defined as time from block performance (removal of the needle) until the stimulation with an alcohol swab feels cold again.
Time frame: 0-36 hours
Difference in duration of sensory nerve block assessed by pain during tonic heat stimulation between perineural dexmedetomidine and placebo
Duration of sensory nerve block measured by pain during tonic heat stimulation defined as time from block performance (removal of the needle) until a thermode heated to 45C for 30 seconds elicits a painful response again (VAS\>0)
Time frame: 0-36 hours
Difference in duration of sensory nerve block assessed by pain during tonic heat stimulation between systemic dexmedetomidine and placebo
Duration of sensory nerve block measured by pain during tonic heat stimulation defined as time from block performance (removal of the needle) until a thermode heated to 45C for 30 seconds elicits a painful response again (VAS\>0)
Time frame: 0-36 hours
Difference in duration of sensory nerve block assessed by pain during tonic heat stimulation between perineural dexmedetomidine and systemic dexmedetomidine
Duration of sensory nerve block measured by pain during tonic heat stimulation defined as time from block performance (removal of the needle) until a thermode heated to 45C for 30 seconds elicits a painful response again (VAS\>0)
Time frame: 0-36 hours
Difference in duration of sensory nerve block assessed by pain during tonic heat stimulation between high dose ropivacaine and placebo
Duration of sensory nerve block measured by pain during tonic heat stimulation defined as time from block performance (removal of the needle) until a thermode heated to 45C for 30 seconds elicits a painful response again (VAS\>0)
Time frame: 0-36 hours
Difference in duration of motor nerve block assessed by maximum voluntary isometric contraction between perineural dexmedetomidine and placebo
Duration of motor nerve block measured by maximum voluntary isometric contraction is defined as time from block performance (removal of the needle) until fifth finger abduction maximal voluntary isometric contraction (MVIC) \> 75% of baseline value, or the participant indicates return of normal motor funktion.
Time frame: 0-36 hours
Difference in duration of motor nerve block assessed by maximum voluntary isometric contraction between systemic dexmedetomidine and placebo
Duration of motor nerve block measured by maximum voluntary isometric contraction is defined as time from block performance (removal of the needle) until fifth finger abduction maximal voluntary isometric contraction (MVIC) \> 75% of baseline value, or the participant indicates return of normal motor funktion.
Time frame: 0-36 hours
Difference in duration of motor nerve block assessed by maximum voluntary isometric contraction between systemic dexmedetomidine and perineural dexmedetomidine
Duration of motor nerve block meassured by maximum voluntary isometric contraction is defined as time from block performance (removal of the needle) until fifth finger abduction maximal voluntary isometric contraction (MVIC) \> 75% of baseline value, or the participant indicates return of normal motor funktion.
Time frame: 0-36 hours
Difference in duration of motor nerve block assessed by maximum voluntary isometric contraction between high dose ropivacaine and placebo
Duration of motor nerve block measured by maximum voluntary isometric contraction is defined as time from block performance (removal of the needle) until fifth finger abduction maximal voluntary isometric contraction (MVIC) \> 75% of baseline value, or the participant indicates return of normal motor funktion.
Time frame: 0-36 hours
Difference in onset of sensory nerve block assessed by mechanical discrimination (pinprick) between perineural dexmedetomidine and placebo
Onset of sensory nerve block assessed by mechanical discrimination (pinprick) is defined as time from block performance (removal of the needle) until the needle stops feeling sharp.
Time frame: 0-36 hours
Difference in onset of sensory nerve block assessed by mechanical discrimination (pinprick) between systemic dexmedetomidine and placebo
Onset of sensory nerve block assessed by mechanical discrimination (pinprick) is defined as time from block performance (removal of the needle) until the needle stops feeling sharp.
Time frame: 0-36 hours
Difference in onset of sensory nerve block assessed by mechanical discrimination (pinprick) between perineural dexmedetomidine and systemic dexmedetomidine
Onset of sensory nerve block assessed by mechanical discrimination (pinprick) is defined as time from block performance (removal of the needle) until the needle stops feeling sharp.
Time frame: 0-36 hours
Difference in onset of sensory nerve block assessed by mechanical discrimination (pinprick) between high dose ropivacaine and placebo
Onset of sensory nerve block assessed by mechanical discrimination (pinprick) is defined as time from block performance (removal of the needle) until the needle stops feeling sharp.
Time frame: 0-36 hours