Investigators will assess if perineural dexamethasone can increase the duration of an ulnar nerve block when controlling for systemic effects in healthy volunteers.
Healthy volunteers will have bilateral ulnar nerve blocks performed with bupivacaine on two different days with a minimum of 14 days wash-out. On one day, the participants will also receive dexamethasone in one arm and placebo in the other. On the other day, the participants will also receive placebo in one arm and lidocaine in the other. By this using this design, the investigators will be able to assess if perineural dexamethasone can increase the duration of an ulnar nerve block when controlling for the systemic effects. Furthermore, to ensure blinding, the investigators have also incorporated the lidocaine group which also allows for the assessment of the effects of adding lidocaine to a peripheral nerve block with bupivacaine. The order of which the participant will receive dexamethasone and lidocaine will be random. It will also be random in which arm the participant receives dexamethasone and lidocaine.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
QUADRUPLE
Enrollment
16
Zealand University Hospital
Køge, Zealand Region of Denmark, Denmark
Duration of the sensory nerve block, assessed by temperature discrimination (cold swab)
The investigators will stimulate the skin with an alcohol swab and ask the participant if it is cold or warm. The duration of the sensory block will be defined as the time to the alcohol swab feels cold again. The investigators will assess temperature discrimination every 30 minutes.
Time frame: 24 hours
Duration of the sensory nerve block, assessed by mechanical discrimination (pinprick)
The investigators will stimulate the skin with a needle. The duration of the sensory block will be defined as the time to the needle feels sharp again. The investigators will assess mechanical discrimination every 30 minutes.
Time frame: 24 hours
Duration of analgesia, assessed by pain during tonic heat stimulation (heated thermode)
The investigators will stimulate the participants' skin for 30 seconds with a thermode heated to 45 degrees Celsius. The participants rate the pain elicited on the Visual Analogue Scale using a ruler indicating "no pain" at zero millimetre on one end and "worst perceivable pain" at 100 millimetres at the opposite end. The duration of the sensory block will be defined as the time to the tonic heat stimulation elicits a painful response of Visual Analogue Scale above '0'. The investigators will assess pain every 30 minutes.
Time frame: 24 hours
Duration of the motor block, assessed by fifth finger abduction
The hand is placed facing with the volar side upwards. The hand is constricted so that only the fifth finger can abduct. The motor block is assessed using a Modified Bromage Scale. The duration of motor block is the time from block performance until Bromage grade '4' is reached or the participant indicates a feeling of normal strength in the finger.
Time frame: 24 hours
Onset of the sensory nerve block, assessed by temperature discrimination (cold swab)
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Dexamethasone will be added perineurally to an ulnar nerve block with bupivacaine, some will be reabsorbed and distributed systemically. Thereby, the investigators control for the systemic effects of adding perineural dexamethasone to an ulnar nerve block.
The investigators will stimulate the skin with an alcohol swab and ask the participant if it is cold or warm. The onset of the sensory block will be defined as the time to the alcohol swab no longer feels cold. The investigators will assess the onset by temperature discrimination every 5 minutes.
Time frame: 24 hours