Impact of Interscalene Nerve Block on Cerebral Perfusion During Surgery in the Beachchair Position
Beachchair position is used by many orthopaedic surgeons for shoulder surgery. Most patients undergoing surgery in this position have no complications. However, reported cases of postoperative neurological deficits have highlighted the risk of cerebral and spinal cord ischemia. The etiology of such complications remains unclear. The most plausible explanation for these events would be intraoperative hypotension followed by cerebral hypoperfusion.
General anesthesia is commonly used for shoulder surgery in conjunction with interscalene brachial plexus blockade. During the block, local anesthetic's spread is frequently observed leading to a block of sympathetic fibres. Since all nerves located in the head and neck area go through the stellate ganglion, its block will cause a sympathetic denervation and a decrease of the peripheral vascular resistance, thus increasing the circulation in cerebral blood vessels. In normal situations, there is a vasoconstriction of the cerebral blood vessels in response to a sympathetic stimulation and a vasodilation if sympathetic fibres are blocked.
Transcranial Doppler (TCD) is a non-invasive examination that provides a reliable evaluation of intracranial blood flow in real-time. It can help to detect sudden changes in perfusion and identify potential embolic events. Some studies using TCD have shown an increased ipsilateral cerebral blood flow (CBF) secondary to a reduced vascular tone associated with a stellate ganglion block. Others have shown a reduction of contralateral CBF that could theoretically increase the risk of ischemia in the affected area.
This study will assess the role of interscalene nerve blockade in the protection of cerebral ischemia and preservation of cerebral autoregulation. This study will also aim to identify changes in contralateral CBF.
The investigators hypothesize that:
- Interscalene nerve block will increase CBF
- Interscalene nerve block will not decrease contralateral CBF
- Cerebral autoregulation will be preserved under general anesthesia in conjunction with an interscalene nerve block in this setting.
Procedure: Interscalene nerve block
Procedure: Simulated interscalene nerve block
|Study Design:||Allocation: Randomized
Endpoint Classification: Safety/Efficacy Study
Intervention Model: Parallel Assignment
Masking: Single Blind (Outcomes Assessor)
Primary Purpose: Prevention
|Official Title:||Impact of Interscalene Nerve Block on Cerebral Perfusion During Surgery in the Beachchair Position Under General Anesthesia|
- Cerebral blood flow in the median cerebral artery [ Time Frame: From arrival in the operating theatre until the end of surgery. Patients will be followed for an average of 3 hours. ] [ Designated as safety issue: Yes ]Cerebral blood flow will be assessed using the transcranial Doppler. Because the bones of the skull block the transmission of ultrasound, region with thinner walls must be used for analyzing. For this reason, recording will be performed in the temporal region above the zygomatic arch.
- Arterial blood pressure [ Time Frame: From arrival in the operating theatre until the end of surgery. Patients will be followed for an average of 3 hours. ] [ Designated as safety issue: Yes ]Arterial blood pressure will be measured during each TCD.
- Body temperature [ Time Frame: From induction of anesthesia until the end of surgery. Patients will be followed for an average of 2 hours. ] [ Designated as safety issue: Yes ]Body temperature will be recorded at every TCD performed following induction of general anesthesia.
- End-tidal carbon dioxide [ Time Frame: From induction of anesthesia until the end of surgery. Patients will be followed for an average of 2 hours. ] [ Designated as safety issue: Yes ]End-tidal carbon dioxide will be recorded at every TCD performed following induction of general anesthesia.
- Minimum alveolar concentration (MAC) of Desflurane [ Time Frame: From induction of anesthesia until the end of surgery. Patients will be followed for an average of 2 hours. ] [ Designated as safety issue: Yes ]Minimum alveolar concentration of Desflurane will be recorded at every TCD performed following induction of general anesthesia.
|Study Start Date:||February 2014|
|Estimated Study Completion Date:||July 2014|
|Estimated Primary Completion Date:||July 2014 (Final data collection date for primary outcome measure)|
Placebo Comparator: Simulated interscalene nerve block.
No block will be performed. The anesthesiologist will only disinfect the skin and apply an opaque dressing on the area where the interscalene block would have been done.
|Procedure: Simulated interscalene nerve block|
Experimental: Interscalene nerve block
The anesthesiologist will perform the interscalene nerve block before induction of anesthesia. Standard non-invasive monitoring will be used. The location of the brachial plexus will be identified using ultrasound guidance and its position will be confirmed using a neurostimulator. A standardized mixture of bupivacaine, lidocaine and epinephrine will be injected. An opaque dressing will be applied at the injection site.
|Procedure: Interscalene nerve block|
Prior to surgery, each patient will undergo a baseline bilateral TCD examination in supine position. If the Doppler's results are satisfactory, the patient will then be randomized and proceed to the next step. In case of inadequate results, the patient's participation to the study will be terminated.
The interscalene nerve block will be performed or simulated according to randomization. In the interscalene nerve block group, the attending anaesthesiologist will assess the success of the block and record the presence or absence of Horner's syndrome. The transcranial Doppler operator will be blinded to these observations. Following a real or simulated interscalene block, the patient will undergo a second bilateral TCD in supine position before induction of anesthesia.
The anesthetic technique and monitoring will be standardized. After the induction of anesthesia, a bilateral TCD will be performed with the patient in supine position. Another examination will be performed under general anesthesia immediately after and 30 minutes following the installation of the patient in the beachchair position. A last TCD will be performed after a reduction of end-tidal carbon dioxide at 30 mm Hg.
For each examination, the arterial blood pressure must be stabilized for at least 5 minutes before the Doppler can be initiated. Arterial blood pressure will be measured during each examination. Type, duration of surgery and beachchair position will be recorded. Vasopressor therapy will be noted. Body temperature, end-tidal carbon dioxide and minimum alveolar concentration of desflurane will be collected during each examination performed under general anesthesia.
|Contact: Sébastien Garneau, MD, FRCPC||514-890-8000 ext email@example.com|
|Contact: François Girard, MD, FRCPC||514-890-8000 ext firstname.lastname@example.org|
|Centre Hospitalier de l'Université de Montréal (CHUM)||Recruiting|
|Montreal, Quebec, Canada, H2L 4M1|
|Contact: Sébastien Garneau, MD, FRCPC 514-890-8000 ext 26876 email@example.com|
|Contact: Monique Ruel, RN, CCRP 514-890-8000 ext 24542 firstname.lastname@example.org|
|Sub-Investigator: François Girard, MD, FRCPC|
|Sub-Investigator: Luis Herrera, MD|
|Sub-Investigator: Céline Odier, MD, FRCPC|
|Principal Investigator:||Sébastien Garneau, MD, FRCPC||Centre hospitalier de l'Université de Montréal (CHUM)|