The primary goal is to evaluate ropivacaine blood concentrations during and after local anaesthetic (ropivacaine) infiltration - the Caledonian technique - for total knee replacement surgery. The investigators plan to measure these levels by testing blood samples taken over a timed period. This will allow us to confirm whether the current regimen of local anaesthetic use is within safe limits.
Local anaesthetic (LA) toxicity may occur when the blood levels of a drug become particularly high. There is a need to confirm that the technique is safe to use. In addition, journal case reports may only describe serious side-effects of toxicity such as abnormal heart rhythms whilst more subtle clinical signs are rarely reported. The investigators would like to study whether or not toxic levels may be approached in some patients or whether more subtle toxicity symptoms and signs are missed. For example, irregular heartbeat, low blood pressure or confusion/agitation. Therefore, the investigators intend to study ropivacaine blood levels in patients receiving a total hip replacement in the Golden Jubilee National Hospital. A series of timed samples will be taken during the perioperative period. The anaesthesia and surgery will be performed as routine and no new treatment will be involved. Patient demographics, ropivacaine blood levels and clinical observations following LA administration will be collected.
Study Type
OBSERVATIONAL
Enrollment
30
Golden Jubilee National Hospital
Clydebank, West Dunbartonshire, United Kingdom
Plasma levels of ropivacaine
Plasma levels of ropivacaine will be analysed to determine total and free levels. These will be taken following tourniquet release at the following time points: 5, 10, 15, 20, 25, 30 minutes then 1, 4, 12 and 24 hours. Note: Each patient will also have a baseline blood sample taken.
Time frame: Start of surgery until 24 hours postoperatively
Vital signs of heart rate and blood pressure
Vital signs will be recorded (at each time point) when blood samples are taken.
Time frame: Start of surgery until 24 hours postoperatively
Continuous 24 hour electrocardiograph monitoring
Electrocardiograph data will be reported using analysis software to provide a summary of heart rhythm over the study period. Both minor abnormalities (ectopic beats) and major abnormalities (loss of sinus rhythm, heart block) will be detected and reported.
Time frame: First 24 hours after surgery
Symptoms of local anaesthetic toxicity
Patients will be specifically questioned (at each time point) on whether they have any of the following symptoms: Perioral tingling, dizziness, blurred vision, nausea
Time frame: Start of surgery until 24 hours postoperatively
Signs of local anaesthetic toxicity
Patients will be specifically assessed (at each time point) for the following signs: Confusion/agitation, (loss of consciousness, seizure activity, cardiac arrest)
Time frame: Start of surgery until 24 hours postoperatively
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