Spinal Versus General Anesthesia for Patients Undergoing Outpatient Total Knee Arthroplasty

A National Propensity Matched Analysis of Early Postoperative Outcomes

Mark C. Kendall; Alexander D. Cohen; Stephanie Principe-Marrero; Peter Sidhom; Patricia Apruzzese; Gildasio De Oliveira


BMC Anesthesiol. 2021;21(226) 

In This Article


The most important finding of the current investigation was the lack of a difference in early serious adverse events when spinal anesthesia and general anesthesia were used for outpatient TKA. In contrast, the composite rate of early minor adverse events and any adverse events were greater in patients receiving general anesthesia compared to spinal anesthesia for outpatient TKA. Specifically, the need of postoperative blood transfusion was greater in patients receiving general anesthesia compared to regional anesthesia. Taken together, our results suggest that spinal anesthesia provides selective clinical advantages in the early recovery period when compared to general anesthesia for patients undergoing outpatient TKA.

Previous studies have compared general anesthesia to spinal anesthesia with conflicting results in patients undergoing TKAs in the inpatient setting. For example, Warren et al. detected a decreased rate of complications in patients undergoing inpatient TKA with spinal anesthesia compared to those receiving general anesthesia.[18] In contrast, Nakamura et al. reported an increased rate of venous thromboembolism in patients receiving spinal anesthesia for TKA.[19] Nevertheless, as far as we are aware, no study has evaluated the impact between the type of anesthesia technique on patient outcomes after outpatient TKAs.

Our results are clinically important given the current shift of practice towards the performance of total knee replacement in the outpatient setting.[20] Given the current financial incentives and economic pressures to reduce costs, it is expected that the number of outpatient total knee replacement procedures are expected to grow substantially over the following years.[21] To the best of our knowledge, this is the first study to compare the safety of neuraxial versus general anesthetic techniques in the outpatient setting for total knee replacement.

Prior studies examining inpatient TKAs have resulted in conflicting results regarding the effect of spinal anesthesia in reducing transfusion rates when compared to general anesthesia. Rashiq et al. did not detect a benefit of spinal anesthesia to reduce transfusion after inpatient TKAs.[22] In contrast, Wei et al.detected a benefit of spinal anesthesia to reduce transfusion after inpatient TKAs.[23] Our results are critical since patients who have been discharged and need blood transfusions have less access to care (e.g., regular vital signs monitoring and blood tests) to recognize the need for the transfusion in the outpatient setting.

It was also interesting to note the selection process for the patients undergoing outpatient TKA who received spinal anesthesia. In the original cohort, patients in the outpatient setting who received spinal anesthesia were older and had lower BMIs than patients who received general anesthesia. We used propensity score matching to adjust for the covariate imbalances in our analysis and obtained a well-adjusted cohort (e.g., standard mean difference < 0.1 for all covariates). It is possible that clinical practitioners wanted to avoid general anesthesia in older patients due to the potential risk of postoperative delirium and/or cognitive decline.[24] Patients with greater BMI may provide challenges to the performance of spinal anesthesia and this may explain the greater choice of general anesthesia to this population.[25]

We did not detect a greater rate of readmissions and/or failure to rescue in the general anesthesia group compared to the spinal anesthesia group. This collaborates the lack of difference in serious adverse events between the study groups. In the case of blood transfusions, it is possible that patients came to the emergency room to receive a blood transfusion but were not admitted. Unfortunately, the NSQIP database does not track emergency room visits and we could not confirm or refute that assumption.

Our study can only be interpreted within the context of its limitations. With a large, multi-institutional database such as the ACS-NSQIP, there are well published limitations including the possibility of clerical error, differences in inter-rater reliability across institutions and only 30-day postoperative follow-up window. In order to avoid overfitting of our models, we did not include all variables collected at NSQIP. Lastly, due to limitations on the database, we cannot assess potential drug usage variations in the anesthesia techniques that could potentially alter the outcome. For example, it is possible that some patients in the general anesthesia group received sugammadex to reverse neuromuscular blockage while others did not receive it.