Effect of Liposomal Bupivacaine (Exparel) on Length of Stay in Total Knee Replacement Surgery

Abstract

Specific Aims Specific Aim #1: The primary outcomes of this study are to measure the length of stay (LOS), opioid use per 24 hour inpatient time period, and over all opioid rate in total knee replacement (TKA) patients who receive liposomal bupivacaine as compared to standard post-operative pain management protocol. Specific Aim #2: The second aim of this study is to analyze 30 day admissions between the two groups. Methods A Retrospective chart review was used to compare LOS and 24, 48, and 72 hour opioid use between the treatment group, liposomal bupivacaine and the control group consisting of Tucson Medical Center pain management protocol in patients who received a single TKR. Opioid use will be measured by postop 24-hour time intervals: 0-24, 25-48, and 49-72 hrs. All doses of opioids will be converted to oral morphine milligram equivalents (MME) using Tucson Medical Centers Equianalgesic dosing protocol. Non-normal continuous data was analyzed using the Wilcoxon Rank Sum test, normally distributed continuous data was analyzed using an independent t-test and categorical data was analyzed using a 𝜒2 test with the significance level set at 𝑎= 0.05. Main Results: The treatment group had a mean age of 70.7 (years) (SD=8.6), 25 females (50%), 31 right TKR (62%), and 34 surgeries performed by Dr Cohen (68%). The control group consisted of a mean age of 72 (years) (SD=9.4), 32 females (64%), 29 right TKR (58%), and 25 (50%) surgeries performed by Dr Cohen. (table 1) The treatment group had a mean LOS of 47.63 hrs (SD=18.8) vs 64.65 hrs (SD=23.0) (P<0.0001). in the control group. The average 0-24 opioid morphine milligram equivalents for the treatment group was 62.96 mg (SD=31.9) vs 99.00 mg (SD=60.3) (P=<0.001) in the control group . The average 25-48 opioid morphine milligram equivalents for the treatment group was 43.04 mg (SD=35.8) vs 73.04 mg (SD=46.2)(P=<0.001) in the control group . The average 25-48 opioid morphine milligram equivalents for the treatment group was 73.04 mg (SD=38.3) vs 51.06 mg (SD=39.1) (P=0.06) in the control group .

Conclusions: Liposomal Bupivacaine was associated with a statically significant shortening of length of stay (47.63 hrs vs 64.65 hrs, P<0.0001) Liposomal Bupivacaine was associated with a statically significant lowering of opioid use over the first 24 and 48 hour inpatient stay (62.96 mg vs 99.0 mg, P=<0.001) Both Liposomal Bupivacaine and control groups had a non-significant difference in opioid use over 49-72 hour inpatient stay (43.3 mg vs 73.04 mg, P=0.06) There were a total of three readmissions, one in the liposomal bupivacaine group and two in the control group a non-significant difference (73.04 mg vs 51.06 mg , P=0.56) Liposomal bupivacaine group was associated with a statically significant lowering of rate (mg/hour) of opioid use over the entire length of stay (2.24 mg/hr vs 3.06 mg/hr, P=0.002)