Comparison of Anesthetic Techniques

Introduction - What are Peripheral Nerve Blocks?

• Injection of anesthetic drugs directly into nerve
• Commonly employed in extremity (limb) surgeries

Why are nerve blocks of interest?

• Can be used in lieu of opioid drugs, which carry risk of substance abuse
• An additional tool, or a even a substitute for general anesthesia
• Often essential for orthopedic surgeries

Context of Medical Study - Source of Dataset

• A study published in Regional Anesthesia & Pain Medicine, examined two methods of administration of 2 drugs used to achieve peripheral nerve blocks
• Combined versus sequential administration of Mepivacaine and Ropivacaine
• Mixing drugs can diminish their individual effectiveness, does injecting them in sequence help overcome this?

Variables and Outcomes

103 patients undergoing upper extremity procedures were randomly assigned to a treatment group; combined (1), sequential (2)

Main outcomes observed:

• Time to onset of sensory block
• Time to onset of motor block (paralysis)
• Duration of analgesia, how long before a post-operative pain drug was given?
• Maximum reported verbal pain score (vps)

Inital Distribution Comparisons

Testing for a difference?

Permutation tests and bootstrap confidence intervals for difference of means.

diff_mean_null_os <- samp |> 
  specify(onset_sensory ~ group) |>
  hypothesize(null = "independence") |>  
  generate(reps = 1000, type = "permute")|>
  calculate(stat = "diff in means", order = c("1", "2"))

diff_mean_ci_os <- samp |> 
  specify(onset_sensory ~ group) |>
  generate(reps = 1000, type = "bootstrap")|>
  calculate(stat = "diff in means", order = c("1", "2"))

Where was there an effect?

• Time to Onset of Motor Block:

• p-value = 0.024

Where was there an effect?

• Time to Onset of Motor Block:

• 0 not contained within Confidence Interval

What does this reveal?

• For primary outcomes, different methods of administration only affected time to onset of motor block.
• Sequential administration is not a viable way to overcome effect attenuation that results from combined injection.
• Combined injection has an advantage: Faster complete-motor blocks

Other Relationships?

• What predicts verbal pain score?

Logistic regression for High (>5) versus low (<5) VPS

log_mod_full3 <- glm(data=vps_train, vps_ind ~ age  
+ midazolam  + onset_first_sensory + vps_movement + 
opioid_total, family = binomial())
summary(log_mod_full3)

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