Lower Extremity Blocks Flashcards
Advantages to lower extremity regional anesthesia?
Avoid general anesthesia, hemodynamic stability, may allow patient to participate during the surgery, earlier discharge, post operative analgesia, can leave airway patent to communicate with them, cardiac or pulmonary disease (COPD), avoids use of opiates, N/V, post op sedation, preemptive analgesia
Contraindications to regional anesthesia
Patient refusal, inability for patient cooperation, coagulopathy (depends on their INR, risk vs. benefit) spinals are absolute for coagulopathy
Risks of peripheral nerve blocks
LA toxicity (calculate their ideal body weight), allergic response (esters break down to PABS), transient nerve damage, uncomfortable patient positioning, incomplete blocks
Neuropharmacology of LA
Two classes: Esters and Amides
Esters: metabolized by plasma cholinesterase’s, greater potential for allergic reactions, PABA, Chloroprocaine
Amides: Lidocaine, metabolized by hepatic processes
Neuropharmacology of LA: Toxicity
Systemic absorption can result in CNS and cardiac toxicity
Depends on site of injection, total dose, use of eli
What is the rate of absorption from max to minimum
Intercostals, caudal, epidural, brachial plexus, sciatic, lumbar plexus, femoral “I can eat big plates of spaghetti like fettuccini.
S/S of CNS toxicity
Tongue numbness, lightheadedness, dizziness, tinnitus, disorientation, visual disturbances, seizures leading to CNS depression, respiratory depression, respiratory arrest, CV instability. Metallic taste in mouth, want to do blocks while they are awake,
- CNS toxicity
- Respiratory depression
- Cardiac toxicity
How do you prevent toxicity?
Vigilant monitoring, limit dose accordingly, aspirate before you inject!, inject small volumes (5ml at a time)
General principles
addition of epinephrine prolongs duration of action, use of low concentrations of local anesthetic permit injection of large volumes, used as an alternative or in conduction with general anesthesia. Lower concentration= higher volumes
How do you decide between regional or general anesthesia?
Patient preference, coexisting medical conditions, surgical considerations (positioning, use of tourniquets), surgeon preference, skill of anesthesia provider, do they have cardiac or COPD? Does surgeon need vasodilation for vascular cases? need continued pain management?
What equipment is needed?
Peripheral nerve stimulator or ultrasound, disposable kits, insulated needles, syringes, prep solution, local anesthetic, sterile gloves, monitoring
- insulated needle
What are the techniques to located the nerve?
Ultrasound (new gold standard), paresthesias, nerve stimulator technique, you need to know anatomic relationship of nerves to muscles, bones or arteries
Sciatic nerve block indications:
Surgeries for foot and lower extremity, on the posterior aspect of your leg distal to the knee.
Describe the sciatic nerve
Large nerve, ventral branches of the lumbar plexus, L4-S3
Anatomy: gluteus maximus muscle, gluteus medius, greater trochanter, ischial tuberosity, posterior femoral cutaneous, sciatic nerve.
Landmarks for a sciatic nerve block?
Draw a line from the greater trochanter to posterior superior iliac spine, then a line from the greater trochanter to the sacral hiatus. 5 cm down from first line
With the nerve stimulator, now do you know you’re in the right spot for sciatic nerve block?
Dorsiflexion or eversion of the foot indications common peroneal branch, plantar flexion is tibial branch.
Should just see twitching of toes
What is the volume for a sciatic nerve block?
20-30 ml
What are complications of sciatic nerve block?
Block failure (rare b/c its so large), hematoma
Describe the femoral nerve
Largest branch of the lumbar plexus, emerges through the psoas and descends into the groove between psoas and illiacus, passes UNDER inguinal ligament. Breaks into many branches that supply the muscles of ANTERIOR thigh, knee and hip. Sensory and motor nerve.
What does a femoral nerve block result in?
Sensory effects include anesthesia to anterior portion of the thigh, knee and small area of medial foot.
Motor effects results in inability to abduct the leg or extend the lower leg. *Excellent adjunct for postoperative pain relief
Landmarks for the femoral nerve block?
Inguinal ligament and the femoral artery, insert needle LATERAL to femoral artery
How much do you inject for femoral nerve block?
25-35 ml
Complications of femoral nerve block?
Intravascular injection, hematoma, direct nerve injury (pt should not complain of sharp pain)
What are the indications of femoral blocks?
Surgeries of the anterior thigh and knee
