The Effect of Preoperative Physical Status on Pain Management in Total Knee Arthroplasty Patients Receiving Adductor Canal Blockade

Abstract

Introduction: Managing postoperative pain can be challenging for arthroplasty surgeons. While pain control modalities, such as adductor canal blockade (ACB), have been proven effective, the multifactorial nature of pain perception may serve as an obstacle for optimizing pain control. This study assesses the effect of patient pre-operative physical status on patient perception of pain. Specifically, we compared 1) lengths of hospital stay (LOS), 2) pain levels, and 3) opioid consumption in patients receiving total knee arthroplasty (TKA) who presented with an American Society of Anesthesiologists physical status score (ASA) of 2 and 3.

Materials and methods: A single hospital, single surgeon database was reviewed for patients who had TKA between January 2015 and April 2016. Only patients with an ASA class of 2 or 3 who received ACB were analyzed. This yielded 106 patients with a mean age of 63 years, comprised of 36 men and 70 women. Patients were stratified into those with an ASA class of 2 (n= 58) and those with an ASA class of 3 (n= 48). Electronic medical records were reviewed to obtain demographic and endpoint data. Pain was quantified using Visual Analog Scale (VAS). Continuous variables were compared using the student' s t-test and analysis of variance, while categorical variables were compared using chi-square analysis.

Results: There was no significant difference found between the two groups in LOS (2.25 days vs. 2.19 days; p=0.805), VAS scores (4.95 vs. 5.75; p=0.306), and opioid consumption on day 0 (17.77 morphine eq vs. 23.49 morphine eq; p=0.233) and day 3 (9.11 morphine eq vs. 19.87 morphine eq; p=0.100). However, patients with an ASA score of 2 had a significantly lower opioid consumption on day 1 (32.20 morphine eq vs. 52.70 morphine eq; p=0.049), day 2 (19.21 morphine eq vs. 40.71 morphine eq; p=0.018), and overall (78.30 morphine eq vs. 135.77 morphine eq; p=0.024).

Conclusion: Despite the effectiveness of ACB in controlling pain, patient pre-operative status may affect perception of pain. This study demonstrates that patients with a higher ASA physical status classification consumed more opioid medication postoperatively, despite having similar pain scores and lengths of stay to those with a lower classification. Future studies should assess all ASA classifications and stratify for preoperative opioid consumption and tolerance as a possible confounder.