Anesthetic recovery profiles of intrathecal ropivacaine and bupivacaine in ASA I–II patients undergoing outpatient total hip arthroplasty

Abstract

Background

Spinal anesthesia is commonly used in outpatient total hip arthroplasty (THA). Optimizing the duration of sensory and motor blocks is critical for early postoperative recovery.

Objective

This study aimed to compare the duration of motor block and post-anesthesia care unit (PACU) stay between intrathecal bupivacaine and ropivacaine in patients undergoing outpatient THA.

Methods

A total of 220 ASA I–II patients scheduled for outpatient THA were retrospectively analyzed. Of these, 110 patients received 12–14 mg of intrathecal bupivacaine, and 110 patients received 14–16 mg of intrathecal ropivacaine. The primary outcomes were the duration of motor block and the length of PACU stay, and secondary outcomes included time to discharge and postoperative complications.

Results

The mean (SD) dose of spinal anesthetic was 14.9 (0.7) mg in the ropivacaine group and 12.6 (0.8) mg in the bupivacaine group. Ropivacaine was associated with a significantly shorter duration of motor block (mean difference 44.9 min; 95% CI 33.2–56.6; P < 0.001), PACU stay (median difference 12.3 min; 95% CI 2.1–22.6; P = 0.019), and time to first postoperative void (mean difference 0.6 h; 95% CI 0.1–1.0; P = 0.009). Ropivacaine provided more predictable motor block duration than bupivacaine (P < 0.001), with similar variability in PACU time. No significant between-group differences were observed in discharge time or postoperative complications.

Conclusion

Intrathecal ropivacaine provides a shorter motor block duration and faster early recovery compared with bupivacaine in outpatient THA, without increasing postoperative complications, but confirmation in a well-designed prospective study is warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-026-03967-w.

Introduction

Spinal anesthesia is widely used for total hip arthroplasty (THA) because of its rapid onset, reliable sensory and motor block, and low risk of systemic toxicity. In the outpatient setting, where early mobilization and same-day discharge are key goals, the choice of local anesthetic may substantially influence recovery time and overall outcomes. Bupivacaine and ropivacaine are long-acting amide anesthetics commonly used for spinal anesthesia, but they differ in their pharmacodynamic profiles [1–3].

Bupivacaine has traditionally been favored for major orthopedic procedures because of its potent and long-lasting effects. In contrast, ropivacaine has gained increasing use in ambulatory surgery due to a shorter and less intense motor block, lower cardiotoxic potential, and more rapid functional recovery [4, 5]. These pharmacologic differences may be particularly relevant in fast-track pathways, where early ambulation is emphasized to facilitate same-day discharge and reduce postoperative complications [6].

The present study aimed to compare intrathecal bupivacaine and ropivacaine in outpatient THA, focusing on recovery-related outcomes including motor block duration, length of stay in the post-anesthesia care unit (PACU), and discharge readiness in ASA I–II patients.

Methods

Study design and population

This retrospective observational study included adult ASA I–II patients who underwent elective outpatient THA under spinal anesthesia at Turku University Hospital between 17th Aug 2023 and 20th December 2024. The study was conducted and reported in accordance with the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines.

Eligible patients were adults scheduled for elective primary THA under spinal anesthesia with planned same-day discharge. Inclusion criteria required age 18–79 years, ASA physical status I–II, adequate physical and psychological capacity, and fulfillment of predefined day-case criteria, including reliable communication, availability of adult support overnight after discharge, and residence within a reasonable distance from the hospital. Patients with significant cardiovascular or cerebrovascular disease, conditions affecting consciousness, untreated obstructive or central sleep apnea, heart failure, insulin-dependent diabetes, cognitive impairment, history of substance abuse, chronic high-dose opioid use, ongoing antithrombotic therapy, coagulation disorders, previous venous thromboembolism, or substantial mobility impairment were excluded. Eligible patients were consecutively identified from institutional anesthesia and surgical records. To achieve the predefined statistical power based on the a priori sample size calculation, eligible patients were retrospectively reviewed until the required sample size was reached for both groups. Thus, the equal group sizes reflected the predefined sampling strategy rather than randomization.

Following its introduction in March 2024, intrathecal ropivacaine was implemented after a short, predefined transition period during which its use was familiarized within routine clinical practice. After this period, ropivacaine was adopted as the primary intrathecal anesthetic and gradually replaced bupivacaine in routine use. Group allocation therefore reflected a temporal shift in anesthetic management rather than selective assignment. No other intended changes to perioperative protocols were implemented during the study period, apart from the local anesthetic used for spinal anesthesia.

Data acquisition

Data were retrospectively retrieved from electronic anesthesia and surgical records in accordance with institutional data protection regulations. No interventions were performed, and all analyses were observational. In addition to addressing the current clinical research question, this dataset contributed to the validation of a new data retrieval pipeline as part of a broader project developing machine learning models for optimizing spinal anesthesia. The results are intended to support, rather than replace, clinical decision-making by anesthesiologists.

Ethics and funding

The study protocol was approved by the Institutional Research Committee of the Hospital District of Southwest Finland (Ref. T1354/2024-2) and conducted under a research permit allowing secondary use of patient data. Informed consent to participate was waived by the Institutional Research Committee of the Hospital District of Southwest Finland due to the register-based nature of the study.

This work was supported by Finnish governmental research funding for university-level health research received by Turku University Hospital (#30139) and Sakari Alhopuro Foundation.

Anesthetic technique

All patients received standardized spinal anesthesia with a 27G Quincke or pencil-point needle at the L3–L4 or L4–L5 interspace, administered by anesthesiologists specialized in regional anesthesia. Patients were allocated into two groups according to the anesthetic administered: the bupivacaine group, which received 12–14 mg of isobaric bupivacaine 5 mg/ml, and the ropivacaine group, which received 14–16 mg of isobaric ropivacaine 5 mg/ml. The dose ranges reflect institutional guidelines and have been calibrated for optimal throughput. Supplemental sedation with midazolam and/or propofol was provided at the discretion of the attending anesthesiologist. No intrathecal opioids or other adjuvants were administered. Spinal anesthesia was considered adequate when cold sensation was lost above the iliac crest, corresponding to the L1 dermatome.

Surgical technique

The THA procedure was performed per routine via posterior or anterolateral (modified Hardinge) approach. All procedures were performed by seven orthopedic surgeons, each conducting over 100 hip arthroplasties annually. Contemporary cemented or uncemented femoral components were used in combination with cementless acetabular components. Surgical procedures were classified according to NOMESCO codes as hybrid fixation (NFB40, NFB41) or cementless fixation (NFB30). All patients received local infiltration analgesia (LIA) block with 100 mL of ropivacaine 2 mg/ml, 5 mL of epinephrine 0.1 mg/ml and 1 ml of ketorolac 30 mg/ml. Blood loss was measured intraoperatively by assessing the volume of blood in suction bottles and the weight of surgical swabs.

Management of postoperative pain

If the patient requested additional medication for pain caused by the spinal needle, position, or tourniquet, intravenous fentanyl 50 µg was given and repeated as necessary during the surgery. In the PACU, patients received 1000 mg of oral paracetamol, 500/20 mg of oral naproxen/esomeprazole, and 5–10 mg of oral oxycodone. Intravenous oxycodone (0.03–0.05 mg kg − 1) was given if patients reported moderate or intense pain (NRS > 3) after oral oxycodone administration and the dose was repeated after 15 min until the NRS score was ≤ 3. The postoperative multimodal analgesia regimen in the ward consisted of oral paracetamol 1000 mg every 8 h and oral naproxen/esomeprazole 500/20 mg twice a day. Oral oxycodone was used if the patient reported moderate to intense pain (NRS > 3) after these medications.

Outcomes

The primary outcomes were the duration the duration of motor block defined as the time from intrathecal injection to the return of lower-limb motor function, and the length of stay in the PACU. Motor function in the PACU was assessed by nurse anesthetists at 15-minute intervals. The return of motor function was defined as the first moment the patient was able to flex the knee on either side, and this timestamp was used as the endpoint for spinal anesthesia.

Secondary outcomes included time to hospital discharge (from the end of surgery to hospital discharge), postoperative opioid consumption in the PACU and during the first 6 postoperative hours standardized to intravenous oxycodone, time to first voluntary voiding, and postoperative complications within 6 postoperative hours. Postoperative nausea and vomiting (PONV), dizziness, excessive pain, and prolonged numbness were classified as complications if, based on the medical record entries, they impaired mobilization or prevented same-day discharge. The number of patients who were unable to be discharged on the day of surgery was also evaluated.

Data analysis

The sample size was calculated to detect a 20% difference in spinal motor block duration between groups (mean 140 ± 45 min), providing 90% power at α = 0.05, which required 55 patients per group. Because PACU stay was also a co-primary outcome with greater variability, the sample size was increased to approximately 110 patients per group to ensure adequate power and reliability across both endpoints.

Continuous variables were analyzed using the student’s t-test, Mann–Whitney U test, or Kruskal–Wallis test, as appropriate. Categorical variables were compared using the Chi-square or Fisher’s exact test. A two-tailed P value < 0.05 was considered statistically significant. Multivariable linear regression analyses were performed for motor block duration, PACU stay, time to urination, and time to discharge to adjust for potential confounders (age, sex, BMI, and height). Differences in variability between the two groups for the primary outcomes were assessed using Levene’s test for equality of variances, applying the Brown–Forsythe modification to account for non-normality. A two-sided significance level of α = 0.05 was used.

Results

A total of 220 patients undergoing ambulatory hip arthroplasty were included in the final analysis after screening for eligibility and exclusion of patients not meeting the inclusion criteria, as detailed in the flow chart presented in Supplemental Fig. 1.

Of these, 110 patients received 12–14 mg of intrathecal bupivacaine and 110 received 14–16 mg of intrathecal ropivacaine. Baseline characteristics, including age, sex, body mass index (BMI), and ASA classification (I–II), were comparable between the two groups (Table 1).

Table 1.

Patient characteristics

	ALL (n = 220)	BUPIVACAINE (n = 110)	ROPIVACAINE (n = 110)	P -value
Age (years)¹	64.9 (8.2; 39–79)	64.3 (9.1; 39–78)	65.4 (7.3; 44–79)	0.32
Women3	123 / 56	58 / 53	65 / 59	0.41
BMI2	27.7 (3.9)	28.0 (3.5)	27.5 (4.3)	0.34
Dose of spinal anesthetic (mg)2	-	12.6 (0.8)	14.9 (0.7)	-
Duration of surgery (min)2	55 (14)	57 (16)	54 (11)	0.10
Smoker3	19 / 8.6	11 / 10.0	8 / 7.3	0.63
Arterial hypertension3	87 / 39.5	43 / 39.1	44 / 40.0	1.00
Dyslipidemia3	61 / 27.7	29 / 26.4	32 / 29.1	0.76
Hypothyreosis3	23 / 10.5	10 / 9.1	13 / 11.8	0.66
Non-insulin dependent diabetes3	16 / 7.3	7 / 6.4	9 / 8.2	0.80
Obstructive sleep apnea3	18 / 8.2	8 / 7.3	10 / 9.1	0.81

Values are: ¹Mean (standard deviation and range), ²Mean (standard deviation), ³Number and percentage

The mean (SD) duration of motor blockade after induction of spinal anesthesia was significantly shorter in the ropivacaine group than in the bupivacaine group (mean difference 44.9 min; 95% CI 33.2–56.6 min, P < 0.001) (Fig. 1). Similarly, the median (IQR) PACU stay was shorter in the ropivacaine group compared with the bupivacaine group (median difference 12.3 min; 95% CI 2.1–22.6 min, P = 0.019) (Fig. 2). Motor block duration showed lower variability in the ropivacaine group than in the bupivacaine group (SD 31.66 vs. 53.62; F(1, 218) = 20.16; p < 0.001). Variability in PACU time was similar between the groups (SD 35.87 vs. 40.32; F(1, 218) = 0.04; P = 0.84).

Fig. 1.

Distribution of motor block duration in patients Receiving Ropivacaine (ROPI) or Bupivacaine (BUPI). Box plots indicate the median and interquartile range. Individual data points represent all observed values

Fig. 2.

Distribution of Post-anesthesia Care Unit (PACU) stay in patients Receiving ropivacaine (ROPI) or Bupivacaine (BUPI). Box plots indicate the median and interquartile range. Individual data points represent all observed values

The mean (SD) time to voluntary voiding was significantly shorter in the ropivacaine group than in the bupivacaine group (mean difference 0.6 h; 95% CI 0.1–1.0 h, p = 0.009). However, the total time to hospital discharge did not differ significantly between the groups, with a median (IQR) of 6.9 h (6.0-7.9) in the ropivacaine group and 6.9 h (5.7–8.2) in the bupivacaine group (p = 0.81). Furthermore, the incidence of postoperative complications within the first 6 postoperative hours, including orthostatic intolerance, urinary retention, PONV, and motor weakness attributable to spinal anesthesia, as well as the number of patients who were unable to be discharged on the day of surgery were comparable between the two groups (Table 2).

Table 2.

Study outcomes

	ALL (n = 220)	BUPIVACAINE (n = 110)	ROPIVACAINE (n = 110)	P -value
Duration of spinal anesthesia (min)¹	153 (49)	175 (54)	131 (32)	< 0.001
PACU time (min)²	72 (56–95)	78 (63–101)	66 (55–93)	0.019
Time to micturition (h)¹	5.1 (1.5)	5.4 (1.6)	4.9 (1.4)	0.009
Time to discharge (h)²	6.9 (6.0–8.0)	6.9 (5.7–8.2)	6.9 (6.0-7.9)	0.81
PONV³	21 / 9.5	8 / 7.2	13 / 11.8	0.49
Prolonged motor weakness³	16 / 7.2	10 / 9.1	6 / 5.5	0.31
Postoperative dizziness³	9 / 4.0	6 / 5.5	3 / 2.7	0.33
Oxycodone consumption in PACU (mg)²	5 (0–10)	5 (0–10)	5 (0–9)	0.32
Total 6 h postoperative oxycodone consumption (mg)²	10 (5–15)	10 (5–15)	10 (5–15)	0.60
Highest NRS at postoperative ward²	1 (0–3)	1 (0–3)	0 (0–3)	0.24
Failure to achieve same-day discharge3	27 / 11.8	15 / 13.6	12 / 10.9	0.45

Values are: ¹Mean (standard deviation), ²Median (IQR), ³Number and percentage

In multivariable analyses adjusting for age, sex, BMI, and height, the results remained materially unchanged. Ropivacaine was independently associated with a shorter duration of motor block (P < 0.001), shorter PACU stay (P = 0.021) and shorter time to voluntary voiding (P = 0.007), while no significant differences were observed in time to discharge or postoperative complications (Supplemental Table 1). Among covariates, male sex was associated with a longer time to voluntary voiding.

There was no difference in the amount of postoperative oxycodone consumption in PACU (P = 0.32) or within 6 postoperative hours (P = 0.60) between the groups (Table 2).

Discussion

Our findings confirm that both intrathecal bupivacaine and ropivacaine are effective local anesthetics for spinal anesthesia in outpatient hip arthroplasty, although their recovery profiles differ. Ropivacaine produced a significantly shorter motor blockade than bupivacaine, consistent with earlier reports of its comparatively weaker motor-blocking properties [4, 7]. Ropivacaine was associated with more rapid motor block regression and a modest reduction in PACU stay (approximately 12 min), which may support early mobilization and discharge in ambulatory settings. The consistency of findings after multivariable adjustment supports the robustness of the observed associations. While this did not translate into earlier hospital discharge or improved postoperative outcomes, it may still offer potential advantages for perioperative workflow and patient throughput, particularly within the PACU phase.

The mean dose of ropivacaine was approximately 16% higher than that of bupivacaine, meaning the groups were not strictly dose-equated. Previous literature suggests that intrathecal ropivacaine may require approximately 15–30% higher doses than bupivacaine to achieve comparable clinical effects [7–10], and this should be considered when interpreting differences in recovery profiles between the two agents.

Motor block duration exhibited significantly lower variability in the ropivacaine group, indicating a more predictable recovery trajectory. This characteristic, consistently noted in outpatient surgical contexts, supports earlier mobilization and may reduce PACU workload and postoperative monitoring requirements [11]. Although ropivacaine resulted in faster motor block regression, no significant difference was observed in overall hospital discharge times between groups. This retrospective study was conducted during a period of transition in anesthetic practice, and postoperative workflows on the ward were still adapting to same-day discharge protocols. Consequently, factors beyond motor recovery, such as ward routines and discharge assessments, may have contributed to the similar discharge timings. It should also be noted that only recorded hospital discharge times were available for analysis.

In this cohort, the doses were determined by experienced anesthesiologists to achieve adequate sensory block to the L1 dermatome. Approximately half of patients received spinal anesthesia in a separate preparation area before transfer to the operating room, requiring a block sufficient to cover positioning, surgical preparation, and the procedure itself. The doses of intrathecal ropivacaine and bupivacaine used in this study reflect current routine practice in our institution and are consistent with dosing commonly reported in Nordic centers [12]. Although lower doses of spinal local anesthetics have been described in some units [12], particularly within ultra–fast-track protocols, a very short-acting block is not always necessarily advantageous, as patients often experience the highest pain intensity immediately after surgery.

Postoperative opioid consumption was comparable between the two groups, indicating that both anesthetic agents provided adequate anesthesia at their respective doses [13]. Sensory block regression was not systematically recorded. Recovery was assessed using the NRS at 15–30 min intervals in routine practice, but these observations were not standardized and did not allow detailed between-group comparison. Postoperative opioid use and discharge timing were similar, suggesting no clinically meaningful differences in sensory recovery. However, these indirect measures cannot replace systematic assessment.

The study was not powered to compare postoperative complications; however, no significant differences were observed in the incidence of hypotension, urinary retention, or PONV. These findings are consistent with previous research demonstrating similar safety profiles for intrathecal bupivacaine and ropivacaine [3, 14, 15]. The overall rate of PONV was relatively low (7.2% vs. 11.8%) compared with the approximately 30% reported in general surgical populations [16], although current consensus guidelines emphasize the importance of targeted preoperative risk assessment and prophylaxis, particularly within enhanced recovery pathways. Previous research has identified common causes of delayed same-day discharge, including postoperative dizziness, prolonged spinal anesthesia, and PONV [17]. Additionally, care setting, staff attitudes, and discharge destination may influence discharge timing [18, 19]. Although no differences were observed in discharge readiness or complication rates, the more rapid motor block regression associated with ropivacaine may improve patient flow and operational efficiency in high-throughput ambulatory surgical centers.

A key limitation of this retrospective study is the non-randomized, time-dependent allocation of patients, as intrathecal ropivacaine was gradually introduced during the study period. This design introduces a risk of temporal confounding, with observed differences potentially reflecting changes over time rather than anesthetic effects alone. Although no other intended changes to perioperative protocols were implemented, unmeasured temporal factors cannot be excluded, and causal inferences cannot be definitively established. The standardized use of LIA in all patients represents a uniform co-intervention that may have attenuated between-group differences in early recovery and limited isolation of the independent effects of the intrathecal anesthetics; however, this also reflects contemporary routine practice and reduces variability related to postoperative analgesia.

While the exclusion of patients undergoing primary general anesthesia and the lack of long-term follow-up may limit generalizability, the relatively large sample size (220 patients), well-defined inclusion criteria, and use of clinically relevant outcomes, such as motor block duration and PACU stay, enhance the reliability and clinical relevance of the findings. As the vast majority of hip arthroplasties in Finland are performed in public hospitals, the study setting reflects routine clinical practice, supporting applicability to real-world orthopedic anesthesia. By providing a direct comparison between intrathecal bupivacaine and ropivacaine in ambulatory hip arthroplasty, an area that remains relatively underexplored, this study offers valuable, practice-oriented insights for anesthetic choice in outpatient surgery.

Since no adjuvants were used in this study, the findings primarily reflect the intrinsic properties of bupivacaine and ropivacaine. Future studies may consider the impact of adjuvants, such as opioids or α2-adrenergic agonists (e.g., clonidine or dexmedetomidine), on recovery profiles and opioid consumption. A prospective randomized controlled trial (RCT) design would provide a more robust framework for assessing these anesthetics, ensuring stronger evidence while minimizing biases associated with retrospective study designs.

Conclusion

Our findings support the growing evidence that ropivacaine is well suited for outpatient hip arthroplasty, where rapid recovery and early ambulation are critical. Ropivacaine was associated with faster recovery and lower variability in motor block duration, indicating a more predictable profile. While bupivacaine remains effective, this more consistent recovery may favor ropivacaine for same-day discharge. Future prospective studies should assess long-term outcomes, including patient satisfaction, quality of life, and cost-effectiveness, to further refine spinal anesthesia protocols for ambulatory arthroplasty.

Abbreviations

ASA

American society of anesthesiologists physical status classification

BMI

Body mass index

NRS

Numerical rating scale of pain

THA

Total hip arthroplasty

PACU

Post-anesthesia care unit

PONV

Postoperative nausea and vomiting

Authors’ contributions

P.U. and M.R. conceived and designed the study and contributed to all aspects of the work. Data collection was performed by M.R., P.U., M.T., O.K., M.Hem., and M.Hel. Manuscript drafting and revision were carried out by M.R., P.U., M.T., M.Hem., and M.Hel. All authors reviewed and approved the final manuscript.

Funding

This study was funded by Finnish governmental research funding for university-level health research (#30139) and Sakari Alhopuro Foundation (#20250221) received by P.U.

Data availability

The data used in this study were obtained under the Finnish Act on the Secondary Use of Health and Social Data (552/2019). Due to legal restrictions, the authors are not permitted to share the data.

Declarations

Ethics approval and consent to participate

The study protocol was approved by the Institutional Research Committee of the Hospital District of Southwest Finland (Ref. T1354/2024-2) and conducted in accordance with the Declaration of Helsinki (2013). Informed consent to participate was waived by the Institutional Research Committee due to the register-based nature of the study.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.