Comparative study between ultrasound-guided lumbar paravertebral block and lumbar epidural block with ropivacaine for postoperative pain relief in patient undergoing total hip replacement surgery: A prospective randomised, double-blind study

THR (total hip replacement) is mostly performed in geriatrics [1]. This patient population has additional comorbidities. Therefore, it is important to choose an effective intraoperative anaesthetic and analgesic regimen with minimal side effects to optimise functional recovery [2]. Lumbar paravertebral block produces unilateral, segmental, somatic, and sympathetic nerve blockage, which provides effective analgesia. Ultrasound-guided regional anaesthesia (UGRA).

Increases the safety and consistency of paravertebral blocks. The primary aim of this study was to compare the VAS (visual analogue scale) score of the ultrasound-guided lumbar paravertebral and epidural block when using ropivacaine (0.25%) with fentanyl as an adjuvant for postoperative pain in the treatment of THR. Secondary objectives were to compare the rescue analgesia, haemodynamic stability, and duration of hospital stay.

This is prospective, randomised, and double-blind study which was conducted in the Department of Anaesthesia at BHU from February 2019 to February 2020. After receiving approval from the institutional ethics committee and written informed consent from the patients, 60 patients who required unilateral THR were randomised and divided into two groups: Group A and Group B with 30 patients in each group. For group allocation, the sealed envelope technique was used. Included patients were between 50 and 70 years old and were ASA (American Society of Anaesthesiologists) grades I and II. Patients with vertebral deformity; history of allergies to local anaesthetic agent, opioids, and non-steroidal anti-inflammatory drugs; infection at the puncture site of proposed block; deranged coagulation and bleeding parameters (INR>1.5); and patients taking chronic analgesic/ anticoagulant therapy or patients presenting with cognitive impairment were excluded from the study. Study subjects were evaluated during pre-anaesthetic check-up and baseline investigations. The patients were instructed on the use of a 1–10 visual analogue scale (VAS) for pain scores at the preoperative visit. Patient were fasted and premedicated as per hospital protocol. A peripheral intravenous line was secured with 18-gauge cannula, and adequate preloading was done. Monitors were attached for monitoring baseline haemodynamic parameters. Under all aseptic precautions, in Group A, the epidural block was performed in lateral/ sitting position, and in group B, ultrasound-guided lumbar paravertebral block was performed in lateral position with the operative side up. This was followed by a standard spinal anaesthetic of 0.5% hyperbaric bupivacaine with 25 mcg of fentanyl in both the groups. In the postoperative period, both groups had a catheter attached to a LV5 pump containing ropivacaine 0.25% plus fentanyl 2 mcg/ml with a total volume of 250 ml. The rate of infusion in both groups was 5 ml/hr. Blocks were performed by the anaesthesiologist, who was not involved in the study. Similarly, observations in postoperative period were taken by an anaesthesiologist who was not participating in the study.

The sample size for the study was calculated using sealed envelope online software. A pilot study was carried out keeping duration of analgesia as primary parameter. The sample size was based on presumption that there would be minimum expected difference of 25% in the duration of analgesia the two groups. For the result to be statistically significant with α=0.05 and β=0.80.

The demographic profiles and ASA statuses of the patients in Groups A and B were comparable at baseline with no statical difference (Table 1). Figure 2 shows the comparison of VAS score in Groups A and B. Until 12 hours after the procedure, neither group of patients complained of any pain. After 12 hours, Group B had a VAS score of >4, and this difference in pain score—with a p-value 0.086 at 24 hours and 0.067 at 48 hours— was not statically significant. The demand for rescue analgesia in both groups is compared in Table 2. Out of 30 patients in Group A, only 5 patients (16.7%) required rescue analgesic, which is comparable to Group B in which 8 (26%) patients required rescue analgesia. Table 3 compares the mean duration of hospital stay in the groups. In Group A, the duration of hospital stay was 7.50 days compared to 6.47 days in Group B. This difference in duration was statistically significant with a p-value=0.000. Figure 3 compares the mean arterial pressure. It was comparable at baseline in both groups, but there was a statistically significant fall in mean arterial pressure from baseline in both groups at 30 minutes (p=0.000 ), 1 hour (p=0.010), and 4 hours (p=0.028).

Figure 1

Figure 2

Figure 3

Adequate analgesia adds to the success of THR as postoperative early mobilisation can be achieved in the absence of pain. Inadequate analgesia may limit early mobilisation, impede the physical therapy, and delay discharge [3]. In our study, the continuous epidural and paravertebral blocks controlled the postoperative pain in comparable manner. When VAS scores were compared, both methods were found to be effective in controlling postoperative pain without any significant difference. Observations in our study were similar to a study conducted by PJ Matthews, in which no significant difference in analgesia by VAS score after 24 hours was observed [4].

Perttunen et al. [5] demonstrated good postoperative pain relief at rest in paravertebral and extradural groups 1 hour after surgery and found comparable segmental analgesia in both groups up to 20 hours. The rescue analgesia was provided via an injection of diclofenac 1 mg/kg IM, and there was no significant difference in the number of doses that either group required. However, the first analgesic requirement occurred earlier in the paravertebral group at 8–10 hours versus 8–12 hours in the epidural group. This contrasts with our study in which pain relief was comparable in both groups, and rescue analgesia was supplemented with an injection of paracetamol 1 gm intravenous. The first analgesic requirement was earlier in paravertebral block at 12–16 hours versus 16–18 hours in the epidural group.

Our findings corroborate the findings of previous studies by Türker et al. [6] In their study, they found no statistically significant difference in VAS pain scores and the consumption of rescue analgesia after surgery in either group.

Duarte et al. in 2009 (n=104) [7] and Singelyn et al. in 2005 (n= 64) [8] studied the difference in the length of hospital stay for patients who received neuraxial block or peripheral nerve block. They did not find any difference in the length of hospital stay with a mean duration of 0.19 days, 95% CI/0.39-0.77days, whereas in our study there was a decrease in the length of hospital stay in the paravertebral group (6.47 days) compared to the epidural group (7.50 days), which is statistically significant (p-0.000). Lumbar paravertebral block provides early mobility, thereby reducing the duration of hospital stay.

In our study, we found a significant fall in mean arterial pressure from baseline at 30 minutes, 1 hour, and 4 hours in the epidural group when compared to the paravertebral group but this difference was not significant. The paravertebral block predominantly provides unilateral sympathetic blockade, whereas epidural block is usually bilateral with a greater drug spread. This difference is probably the reason for the difference in the incidence of hypotension in the groups. Trials conducted by Aksoy et al. in 2014 [9]. Bhatia et al. in 2008, [10] Singelyn et al. in 2005 [8]. Türker et al. in 2003 [6] reported on hypotension.

Paravertebral block provided comparable analgesia, reduced the duration of hospital stay, and provided better haemodynamic stability. Continuous paravertebral block can be used as an alternative to continuous epidural block.

Key Messages: early mobilisation with better haemodynamic stability is achieved with paravertebral block.