Chapter 10. Continuous Peripheral Nerve Blocks: Local Anesthetic Solutions and Infusion Strategies
When making a decision for your patient regarding the effects of a continuous femoral nerve block, which has the greater influence on continuous nerve blocks?
A. Calculating the total dose delivered
B. Selecting the appropriate concentration
C. Choosing an additive to extend its duration
D. Choosing a long-acting local anesthetic
A is correct. Calculating the total dose has the greatest effect on femoral nerve block.
B is incorrect. Evidence suggests that for infusions involving the femoral nerve block, LA concentration is of minimal importance compared with the total dose.
C is incorrect. Additives have proven to extend the duration of the peripheral nerve block; however, the total dose most influences the peripheral nerve block.
D is incorrect. When choosing a long-acting agent, it is desirable for sensory and motor block to resolve quickly and predictably at the termination of infusion. It remains unknown if there is an “optimal” concentration of local anesthetic. For femoral nerve block evidence suggest total dose being of more importance.
Local anesthetics (LAs) are delivered continuously. When selecting a delivery regimen, what is your goal?
A. Decrease the total amount of LA consumption
B. Decrease additional opioid requirements
C. Decrease the disturbance of daily function such as sleep
D is correct. Adding a patient-controlled bolus, to a basal infusion, usually decreases the required basal infusion rate, the incidence of an insensate extremity, and local anesthetic consumption, the last allowing for a longer infusion duration in the ambulatory setting. At the infraclavicular location utilizing a basal infusion with bolus also has been found to decreased sleep disturbances.
A patient is having a total knee replacement. What has been shown to decrease the basal infusion rate of a continuous LA?
A. Adding opioids preoperatively
B. Giving the patient intravenous Decadron intraoperatively
C. Adding patient-controlled boluses of LA
D. Administering non-opioid-based medication preoperatively
C is correct. Adding patient-controlled boluses of LAs has been shown to decrease the basal infusion rate of continuous LA.
A is incorrect. Adding opioids preoperatively, preemptive analgesic has been proven to decrease postoperative pain.