Paravertebral blocks for post-operative analgesia for robotic-assisted partial nephrectomy: a retrospective review

Introduction

Minimally invasive surgical approaches are increasing in popularity for the management of renal cell carcinomas and other renal pathologies. With the advent of robotic techniques and improved outcomes for patient recovery, so too has emerged an interest in regional anesthesia for managing post-operative pain in this patient population (1,2). While the benefit of regional anesthetic blocks in open nephrectomies is well described (3), their use in minimally invasive urologic procedures like robotic-assisted partial nephrectomy (RAPN) is not well established.

A thoracic paravertebral block (PVB) is a regional anesthetic technique which involves deposition of a local anesthetic around the branching spinal nerve root as it leaves the vertebral foramen within the paravertebral space to provide unilateral sensory, motor, and sympathetic blockade of the thoracic and/or abdominal dermatomes of interest. To provide analgesic coverage of a surgical field, multiple small volume injections are performed at several spinal levels to achieve blockade of adjacent dermatomes corresponding to location of the expected surgical incision. PVBs are well established to demonstrate profound postoperative analgesia in thoracic and abdominal surgeries with significant reduction in postoperative nausea, hospital stay, postoperative pain, time to ambulation, and greater reported postoperative patient satisfaction (4). Furthermore, use of PVBs in other renal surgeries including percutaneous nephrolithotomy and open nephrectomy or pyeloplasty have demonstrated reduced 24-hour postoperative opioid consumption and pain scores (5). Although serious adverse effects associated with a PVB are rare, they include pneumothorax, vascular puncture, nerve injury, local anesthetic toxicity and allergic reactions, and aberrant spread of local anesthetic to the epidural or intrathecal space resulting in hypotension and/or unintended bilateral blockade.

This study sought to understand if PVB was associated with differences in perioperative pain outcomes [including post-anesthesia care unit (PACU) length of stay, postoperative opiate consumption, and reported postoperative pain scores] for patients undergoing RAPN. We present this article in accordance with the STROBE reporting checklist (available at https://tau.amegroups.com/article/view/10.21037/tau-2025-1-430/rc).

Methods

The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the institutional review board of Mayo Clinic (IRB# 22-010493) and individual consent for this retrospective analysis was waived. All patients who underwent elective RAPN by a single surgeon at Mayo Clinic between November 2018 to April 2022 were considered for this study. During this period, in the surgical and anesthetic interest of expanding opiate-sparing techniques to urologic surgical patients at our institution, all patients undergoing RAPN at our institution were planned to receive a preoperative PVB unless contraindicated or refused. The period chosen was to obtain an adequate cohort of patients to be able to compare the impact of the block. Patients who required conversion to an open procedure, who were on opioid analgesics preoperatively, or who received patient-controlled analgesia post-operatively were excluded from our study.

The PVBs were performed in the preoperative area prior to transport to the operating room via a landmark technique or ultrasound technique. Choice of technique was at the discretion of the regional anesthesiologist performing the block (6). To perform the landmark-based thoracic PVB, the patient was placed in a seated position. The superior edge of the spinous process was identified by palpation at the desired thoracic level and the needle insertion point was marked 2.5 cm lateral from the midline. After skin infiltration with lidocaine, a 22-gauge Tuohy needle was inserted perpendicular to the skin and advanced 2–5 cm until contact was made with the corresponding thoracic transverse process. Once bone was contacted and depth of that contact point was noted, the needle was withdrawn into the subcutaneous tissue and redirected caudally. The needle was then advanced slowly to a depth of 1.0–1.5 cm beyond the contact depth, sliding underneath the transverse process and through the superior costotransverse ligament to enter the paravertebral space. Local anesthetic was deposited, and the needle was withdrawn. If performed using an ultrasound guided technique, a high-frequency linear transducer (10–5 MHz) was utilized to ensure accurate needle location and visualization of real-time local anesthetic distribution. This process was repeated for each thoracic dermatome of interest based on the anticipated location of the surgical incisions, most often unilateral T9–10, T10–11, and T11–12 interspaces to target respective dermatomes of the operative side. Five milliliters of ropivacaine 0.5% was used at each level for all PVBs in this study for a total of fifteen milliliters of 0.5% ropivacaine per patient. The decision to decline to perform a PVB was at the discretion of the anesthesia team and determined based on preoperative contraindications (i.e., patient refusal, coagulopathy/use of anticoagulants, presence of unfavorable anatomy of paravertebral space like presence of thoracic spinal hardware) which would preclude safe performance of the block.

RAPN was performed utilizing the four-arm technique as previously described (7). Air Seal (Con Med, Buenos Aires, Argentina) was used for insufflation. Insufflation was set to 15 mmHg for all cases. The renal hilum was clamped and the tumor cut free from the kidney followed by standard cortical renography. Specimen extraction site was completed with a subcostal incision in the upper quadrant mid clavicular line in all cases (right side or left side). Patients did not undergo a bowel preparation for surgery. The intraoperative anesthetic management was at the discretion of the in-room anesthesiologist in both groups, as there is no standardized intraoperative protocol for patients undergoing RAPN at our institution. In the PACU, pain was managed with intravenous opioids under the management of the in-room anesthesiologist, and on the hospital floor ward with oral opioids with intravenous opioids only used as needed for breakthrough pain. The patients are not given any standard non-opioid regiment, e.g., acetaminophen, non-steroidal anti-inflammatories (NSAIDs). All patients were provided similar, although not standardized, access to scaled doses of opiate and non-opiate analgesic medications titrated by nursing staff according to patient-reported pain scores. Pain scores were measured on a standard 0–10 pain scale.

Information was collected from the electronic medical record regarding baseline patient characteristics [age, sex, body mass index (BMI), American Society of Anesthesiologists (ASA) score, anesthesia type, intravenous fluids (IVF) administered] and outcomes [morphine equivalents (intraoperative, PACU, and floor), PACU pain scores (first, minimum, maximum, average), hospital floor ward pain scores (minimum, maximum, average), PACU length of stay (minutes), and hospital length of stay (days)]. Primary outcomes included patient-reported post-operative pain scores (in the PACU and surgical floor) based on a verbal numerical rating scale from 0 to 10, as well as opioid use measured in morphine equivalents measured at both locations. Secondary outcomes focused on PACU and total hospital length of stay.

Statistical analysis

Continuous variables were summarized using the sample median and range. Categorical variables were summarized with number and percentage of patients. Comparisons of baseline patient characteristics between PVB and non-PVB groups were made using a Wilcoxon rank sum test (continuous and ordinal variables) or Fisher’s exact test (categorical variables).

Comparisons of outcomes between the PVB and non-PVB groups were made using unadjusted and multivariable regression models appropriate for the potential skewed nature of the given outcome variable (continuous, ordinal, or count). Specifically, continuous outcome variables (morphine equivalents, average pain scores, and PACU length of stay) were compared between PVB and non-PVB groups using linear regression models; regression coefficients (referred to as β) and 95% confidence intervals (CIs) were estimated. Ordinal outcome variables (first, minimum, and maximum pain scores) were compared between PVB and non-PVB groups using proportional odds logistic regression models; odds ratios (ORs) and 95% CIs were estimated. The count outcome variable (hospital length of stay) was compared between PVB and non-PVB groups using a negative binomial regression model; multiplicative effects on the mean and 95% CIs were estimated. Multivariable models were adjusted for age, sex, BMI, ASA score, maintenance anesthesia type, and IVF administered.

No adjustment for multiple testing was made in these exploratory analyses, and P values less than 0.05 were considered as statistically significant. All statistical tests were two-sided. Statistical analyses were performed using R Statistical Software (version 4.1.2; R Foundation for Statistical Computing, Vienna, Austria).

Results

A total of 200 patients were included in this study (Figure 1). A comparison of baseline patient characteristics between PVB and non-PVB groups is provided in Table 1. Characteristics were similar between groups with the exception of BMI, which was slightly higher in the PVB patient cohort (median: 30.6 vs. 29.3 kg/m², P=0.02).

Figure 1 Patient cohort. RAPN, robotic-assisted partial nephrectomy.

Outcomes were compared between PVB and non-PVB groups in Table 2. In multivariable analysis adjusting for age, sex, BMI, ASA score, anesthesia type, and IVF administered, in comparison to non-PVB patients, there was significantly lower PACU morphine equivalents (β: −2.43, P=0.006, Figure 2), a significantly higher hospital floor ward maximum pain score (OR: 2.41, P=0.001, Figure 3), and a significantly lower PACU length of stay (β: −16.95, P=0.002, Figure 4) for PVB patients. Additionally, though not quite statistically significant, there were higher hospital floor ward morphine equivalents (β: 7.00, P=0.06) and a lower PACU maximum pain score (OR: 0.60, P=0.06) for the PVB group compared to the non-PVB group. There were no other notable differences in outcomes between the two groups. There were no noted complications of the PVBs performed in any patients.

Figure 2 Boxplot of morphine equivalents (in milligrams) for the non-PVB and PVB groups. PACU, post-anesthesia care unit; PVB, paravertebral block.

Figure 3 Boxplot of hospital floor ward maximum pain score (on a 0–10 scale) for non-PVB and PVB groups. PVB, paravertebral block.

Figure 4 Boxplot of PACU length of stay (minutes) for non-PVB and PVB groups. PACU, post-anesthesia care unit; PVB, paravertebral block.

Discussion

When analyzing the primary outcome, the data demonstrates no clinically impactful differences in analgesia in the non-PVB group versus the PVB group. We did not feel the statistically significant decrease in median morphine equivalence in the PACU in the PVB group was clinically significant and was countered by increased morphine equivalents administered upon patient transfer to the hospital floor ward. Regardless of the opioid doses administered, it should be noted that there is no statistically significant differences in average pain scores at any time point measured. Lai et al. performed a randomized controlled trial of RAPN patients with each group receiving a quadratus lumborum block versus no block. While it demonstrated reduced opioid requirements in the first 6 hours post block, there was no difference in the 12–24 hours post-block period (8). This observation most likely derived from the effect of the block duration, similar to the nonsignificant difference in morphine equivalents administered on the floor demonstrated in this study.

The reasons for our findings are multifocal. Despite the use of minimally invasive surgical approaches, there is a significant element of visceral pain after laparoscopic surgery. This is confirmed in a study by Covotta et al. in which RAPN patients were randomized to receive a transversus abdominus plane (TAP) block versus no block (9). They assessed several pain factors including measurements of somatic and visceral pain. While the TAP block group had improved somatic pain assessments, there was no difference in visceral pain assessments in either group. This is not surprising as TAP blocks target nerves in a location distal to the branch point of visceral afferent neurons thus offer limited coverage of visceral pain. In contrast, PVBs target nerves prior to this branch point, anesthetizing both somatic and visceral afferents. While renal innervation and incisional somatic innervation arises discretely from T9–T12 thoracic paravertebral ganglia, innervation of the parietal peritoneum and visceral submesothelium arises more broadly from somatic and visceral afferents as cranial as T4 and as caudal as L3 (10). If some component of the visceral pain experienced by the patient after RAPN arises from innervation outside the levels targeted by the PVBs, like potentially that from peritoneal irritation from trocar insertion or diffuse peritoneal traction from gas insufflation, visceral pain may still contribute to the patient’s subjective experience of post-operative pain.

In addition, the lack of a standardized protocol for perioperative management makes it difficult to assess the impact of the block on postoperative pain. Enhanced Recovery After Surgery protocols including regional techniques have been demonstrated to be effective in patients undergoing robotic urologic surgery (11,12). This raises the question if there was a consistent use of known effective adjuvants like NSAIDs, acetaminophen, steroids, muscle relaxants, as well other opioid sparing techniques, the block may have been more effective as part of a comprehensive pain plan versus an isolated perioperative intervention. Early effective analgesia by the regional block may contribute to faster PACU discharge thus less opportunity to receive PACU morphine equivalents. However, resolution of the block in a previously comfortable patient with no concomitant systemic analgesia renders the patient vulnerable to uncontrolled gaps in analgesia coverage.

Several limitations of this study are important to acknowledge. The first category of limitations involves study design. The retrospective design introduces biases into the data collection. While all patients were considered for a regional technique, for those who did not receive one, it was not noted as to why one was not performed. Patient contraindications to a neuraxial nerve block (including coagulopathy, thrombocytopenia, thoracic spinal hardware) or patient declination of the block may be confounding variables in our results. As the in-room anesthesiology provider managed the postoperative pain in the PACU, the management could be impacted by the knowledge of a preoperative block. Other confounding variables such as case complexity, intraoperative blood loss, and tumor characteristics were not accounted for and may contribute to variability in expected post-operative pain.

As the sample size is small, the power to detect associations with outcomes is limited. Therefore, the possibility of a type II error (i.e., a false-negative finding) is important to consider, and one cannot conclude that no true association exists simply due to the occurrence of a non-significant P value in this study. While there was only one surgeon performing the surgery, which allowed for consistency of incision size, and location, and overall technique, there was parity in regional block technique with the study not controlling for individuals doing ultrasound-guided block versus landmark-guided block. While there is no strong data showing one block technique over the other, it is unclear whether the blocks were checked postoperatively to confirm adequate function. At our center, the PVB is successfully used for a variety of other surgical populations, so it is difficult to quantify if the technique of block would impact analgesia across many patients.

Finally, while this analysis examines pain scores and opiate use in relation to PVB for RAPN, there may be other benefits of PVB on postoperative outcomes including reduction of nausea and vomiting, reduction of delirium, or change in pulmonary outcomes. This study did not address these potential patient benefits. This is a worthwhile avenue for future research on the impact of PVBs for this surgical patient population.

As we look to advance regional anesthesia in robotic urologic study, there are several avenues to be considered. Firstly, as mentioned previously, confirmation of block efficacy preoperatively and block administration as part of standardized protocol may have improved outcomes. In addition, the single-injection PVB may not be the best option for this type of surgery as it may require a longer duration of action. Therefore, consideration of continuous regional catheter placement with use of a pain pump, or longer acting local anesthetics with adjuvants may be another means to improve postoperative analgesia. Finally, it may be that a combination of regional techniques is necessary to provide adequate analgesic coverage and duration for the patient undergoing robotic partial nephrectomy (13,14). A 2025 meta-analysis comparing various regional block techniques including quadratus lumborum, TAP, and thoracic paravertebral and epidural blocks for laparoscopic nephrectomies highlighted the difficulty addressing both visceral and somatic pain in a single safe, easy regional technique for a meaningful period of time; it remains elusive and unclear (15).

Conclusions

In this retrospective review of a single surgeon series, the addition of PVB for patients undergoing RAPN resulted in a small, but statistically significant, reduction in PACU morphine equivalents but provided minimal benefit on floor maximum pain score and floor morphine equivalents. There was no significant change in intraoperative morphine equivalents or total hospital length of stay. As a result, our institution no longer routinely performs single-injection PVBs for RAPN. Further studies are indicated before clearly recommending the routine use of PVBs for post-operative RAPN analgesia.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://tau.amegroups.com/article/view/10.21037/tau-2025-1-430/rc

Data Sharing Statement: Available at https://tau.amegroups.com/article/view/10.21037/tau-2025-1-430/dss

Peer Review File: Available at https://tau.amegroups.com/article/view/10.21037/tau-2025-1-430/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tau.amegroups.com/article/view/10.21037/tau-2025-1-430/coif). D.T.T. reports receiving honoraria from the Southeastern Section of the American Urological Association for lectures, presentations, manuscript writing and/or educational events; and has a leadership role in the Judy Nicholson Foundation for kidney cancer research. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the institutional review board of Mayo Clinic (IRB# 22-010493) and individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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