Percutaneous nephrolithotomy (PCNL), is a minimally invasive procedure,but  is associated with substantial postoperative pain. Ultrasound-guided erector spinae block (ESB) is a popular, interfascial regional technique that was initially described for the management of thoracic neuropathic pain. The erector spinae fascia extends from the nuchal fascia cranially to the sacrum caudally, local anesthetic agents extend through several levels, and the

block can be effective over a large area. The present study is undertaken to ascertain analgesic efficacy of  ultrasound-guided erector spinae block (ESB) in patients undergoing PCNL.

1.      Aims & Objectives:

This study aims  to assess the analgesic efficacy of an ultrasound-guided ESB versus conventional analgesia for PCNL.

Primary objective: The primary endpoint is the postoperative pain level based on the visual analogue scale (VAS) scores of patients.

Secondary objective: The secondary end points is the analgesic consumption and additional analgesia requirements of the patients in the postoperative period.

2. Hypotheses (if applicable): ESB mechanism of analgesia is not clear yet but is being used for providing analgesia for various studies. There are no studies on ESB for PCNL surgeries.
3.  Review of literature: (within 500 words):

        i.            Ak K et al.^[1] studied 60 patients who underwent percutaneous nephrolithotomy in a randomized controlled clinical study. Patients were randomly allocated into two groups: group P had 4 ml of 0.5% levobupivacaine injected at each of the T10, T11, and T12 paravertebral spaces a standard PVB, and group C received 4 ml of 0.9% NaCl solution. All patients were given standard general anesthesia. VAS scores and total morphine consumption were lower in group P than in group C: 2.3 vs. 4.3 and 22.3 vs. 43.2 mg, respectively (p < 0.05). The level of satisfaction was higher in group P than group C. They concluded that thoracic PVB with levobupivacaine provided a good postoperative analgesia and increased patient satisfaction for those who underwent percutaneous nephrolithotomy.

      ii.            Saroa R et al.^[2] studied 30 patients undergoing PCNL who were randomized to receive single shot of 20 ml of either ropivacaine (0.2%) or levobupivacaine (0.2%) in ultrasound-guided paravertebral block (PVB) using an in-plane technique. They concluded that single-shot ultrasound-guided ipsilateral PVB at the end of the surgical procedure provides adequate and effective analgesia in the postoperative period with either of the local anesthetic.

    iii.            Jonnavithula N et al.^[3] studied 60 patients undergoing PCNL requiring nephrostomy tube who were randomised to receive either peritubal infiltration or intercostal nerve block (ICNB). At the completion of the procedure, patients in Group P received peritubal infiltration and those in Group I received ICNB at 10, 11, 12^th spaces using fluoroscopy guidance. Pain scores were lower in the group I at all points of measurement than group P. The mean time to first demand for rescue analgesia was higher in Group I (13.22 ± 4.076 h vs 7.167 ± 3.92 h P - 0.001). The number of demands and the amount of analgesics consumed were less in Group I.ICNB provided superior analgesia as evidenced by longer time to first demand of analgesic, reduced number of demands and consumption of rescue analgesic. Peritubal infiltration, although less efficacious, may be a safe and simple alternative technique.

    iv.            De Cassai A et al.^[5] performed a qualitative review of the literature on ESP block. They found that studies showed lower use of opioids and a longer time to first analgesic requirement in the ESP group. In one study, ESP block was found to be as effective as epidural analgesia. ESP block has a wide range of clinical indications. Its mechanism of action is still not thoroughly understood. Only two reports presented complications caused by the block. They concluded that although data suggests that ESP block is an easy and safe technique, more studies are needed to assess safety, complications rates and efficacy of this technique.

      v.            85 publications from 21 journals were included in the pooled review by Tsui BCH et al ^[6] which yielded 242 reported cases between 2016 and 2018. The majority of publications reported single shot techniques (80.2%), followed by intermittent boluses (12.0%) and continuous infusions (7.9%). 90.9% reported use of multimodal analgesia in addition to the ESPB and 34.7% reported sensory changes from ESPB. A reduction in opioid use was reported in 34.7% of cases. One adverse event involving a pneumothorax was reported. This was the first review providing a pooled review of ESPB characteristics. Their conclusion was ESPB appears to be a safe and effective option for multiple types thoracic, abdominal, and extremity surgeries.

4.      Materials  and Methods

Ø  Study design : Prospective clinical pilot study.

Ø  Study period :    

 i) Period which may be needed for collecting the data       Dec 2019 to June 2020

 ii) Period that may be required for analyzing the data       July 2020 to September 2020

Ø  Inclusion criteria:

o   The patients of American Society of Anaesthesiologists (ASA) Grade 1-3 aged between 18-70 years scheduled to undergo PCNL under general anaesthesia will be included in the study. 

o   Exclusion criteria: 

·         Patients with any history of drug allergy to the study drugs,

·         Psychiatric illness, substance abuse,

·         Blood pressure> 140/90mm Hg

·         Pregnancy and lactating mothers

·         Sepsis,

·         Coagulopathy,

·         Complex stones with anticipated access points >2,

·         Patients receiving opioids  

·         Any back or musculoskeletal deformity

Ø  Sample size  with proper justification: Sample size calculation: In a study by Ak K et al. the VAS scores were found to be 4.3 vs 2.3 in the control group and paravertebral group respectively. Setting α = 0.05, assuming a standard deviation of 2 points, and investigating 21 subjects for each group, one can detect a significant difference of 2 points with a power of 0.9 (two-sided hypothesis). Total of 10 patients will be enrolled in either group for the pilot study.

Ø    Detailed description of procedure:                                                                                        A prospective randomised placebo controlled study will be conducted in 20 patients of either sex undergoing PCNL surgeries. Institutional ethical clearance will be obtained and study will be registered with Clinical Trials Registry-India.

The patients satisfying the inclusion criteria will be selected from the operation register on a daily basis. They will be randomised by computer generated random number table and allotted into groups one of two groups: group E (ERB) and group C (control) by sealed envelope technique.

Group E will receive Erector spinae block postoperatively before extubation

Group C will be the control group who will receive conventional parentral analgesics

Patients will be kept fasting for 8 h and premedicated with tablet pantoprazole 40mg on the  night prior to surgery and the morning of surgery. In the operation theatre the patients will be connected to multichannel monitor for electrocardiogram, noninvasive blood pressure, arterial oxygen saturation (SpO₂) respiratory rate, and end-tidal carbon dioxide (EtCO₂) monitoring. Standard general anesthetic technique was used in all patients and maintenance of anesthesia will be achieved through administration of inhalational agent isoflurane with air in O₂ mixture and fentanyl 2mcg/kg will be given for analgesia. If the patient has tachycardia or hypertension (20% over the baseline) Fentanyl 25mcg aliquots will be administered. The total dose of fentanyl used , duration of surgery and any other intraoperative adverse events will be noted. Group C patients will be turned supine at the end of surgery and extubated.

At the end of surgery as all PCNLs are performed in prone position, unilateral ESB on the side of surgery will be performed at T10-11in group E patients level before turning them supine for extubation. Ensuring complete asepsis, ESB will be performed using 5–12 MHz linear array ultrasound transducer probe will be placed 2–3 cm laterally from the midline. After the identification of the T10 transverse process and overlying erector spinae muscles. The needle will be inserted using the in-plane technique following the same injection point in the cranial to caudal direction until the tip contacted to the T10 transverse process. When the correct needle tip position is confirmed by hydro-location with 1 ml of isotonic saline solution aliquots, the anesthesiologist will inject 25ml of 0.5% ropivacaine deep to the erector spinae muscle after negative aspiration through 22 G × 100 mm needle (Stim Sonoplex, Pajunk, Germany). Thereafter the patient will be made supine, extubated after adequate reversal, and transferred to post anesthesia care unit (PACU). The anesthesiologist performing the block and subsequently the investigator assessing the block will be blinded to the group allocation.

The patients will be observed in PACU for heart rate, hemodynamic parameters (systolic and diastolic blood pressure), SpO₂, and respiratory rate at regular intervals for one hour. Pain scores at rest and cough will be evaluated using VAS for pain (0 cm = no pain; 10 cm = worst pain imaginable). The patients will then be transferred to ward if there were no complaints and VAS is <4. The patients will be assessed at 30 minutes, 1, 2,4, 8, 12, 24, 48 and 72 hours for all the parameters, including VAS.

Postoperatively analgesis will be administered to patients with intravenous paracetamol infusion over 20 min (1000 mg) if VAS exceeds 4 and parcetamol will then be repeated every 6 hours. If VAS is >4; 30 minutes after paracetamol infusion injection tramadol 50 mg will be administered intramuscularly. Total dosages of the analgesics will be recorded, calculated, and compared in both the groups at the end of 24, 48 & 72h. Patient satisfaction data will be evaluated using a 5-point scale (1: very bad; 2: bad; 3: good; 4: very good; 5: perfect).In addition, all the patients were monitored for the complications of either the procedure (pneumothorax, accidental epidural) or drugs (bradycardia, hypotension) during the entire postoperative period.

Ø  Potential risks and benefits: Better patient comfort and postoperative analgesia.

Ø  Place of the study: Ramaiah Medical College and Hospitals, Bangalore

Ø  Biological materials required (type - blood, tissue etc and quantity) : none

Ø  Investigations: Routine investigations for the surgical procedure as per American society of Anaesthesiologists physical status classification will be prescribed. No additional investigations required.

Ø  Outcome measures: The patients will be instructed on the VAS, where 0 defines “no pain” and 10 defines “the worst pain he or she had ever experienced.” The pain level will be followed up with VAS, and the analgesic consumption will recorded during the postoperative 24 hours by a researcher who was not a member of the surgical team (at the30 minutes, 1, 2,4, 8, 12, and 24 h)

Ø  Statistical methods : Age, height, weight, duration of the operation, VAS scores, and analgesic consumption will be analyzed by using ANOVA. The χ² test will used to compare adverse events, additional analgesic requirement and patient satisfaction. A p value <0.05 will be considered significant.

5.      Ethical considerations and methods to address issues: Informed written consent will be obtained from patients included in the study.

6.      Implications of the study: New technique for postoperative analgesia following PCNL.

8.      References

1. Ak K, Gursoy S, Duger C, Isbir AC, Kaygusuz K, Ozdemir Kol I, Gokce G, Mimaroglu C. Thoracic paravertebral block for postoperative pain management in percutaneous nephrolithotomy patients: a randomized controlled clinical trial. Med Princ Pract. 2013 Mar;22(3):229-33. doi: 10.1159/000345381. Epub 2012 Dec 14. PubMed PMID: 23257888; PubMed Central PMCID: PMC5586743.

2. Saroa R, Palta S, Puri S, Kaur R, Bhalla V, Goel A. Comparative evaluation of ropivacaine and levobupivacaine for postoperative analgesia after ultrasound-guided paravertebral block in patients undergoing percutaneous nephrolithotomy. J Anaesthesiol Clin Pharmacol. 2018 Jul-Sep;34(3):347-351. doi: 10.4103/joacp.JOACP_187_17. PubMed PMID: 30386018; PubMed Central PMCID: PMC6194850.

3. Jonnavithula N, Chirra RR, Pasupuleti SL, Devraj R, Sriramoju V, Pisapati MV. A comparison of the efficacy of intercostal nerve block and peritubal infiltration of ropivacaine for post-operative analgesia following percutaneous nephrolithotomy: A prospective randomised double-blind study. Indian J Anaesth. 2017 Aug;61(8):655-660. doi: 10.4103/ija.IJA_88_17. PubMed PMID: 28890561; PubMed Central PMCID: PMC5579856.

4. Bang S. Erector spinae plane block: an innovation or a delusion? Korean J Anesthesiol. 2019 Feb;72(1):1-3. doi: 10.4097/kja.d.18.00359. Epub 2019 Jan 31. PubMed PMID: 30732436; PubMed Central PMCID: PMC6369339.

5. De Cassai A, Bonvicini D, Correale C, Sandei L, Tulgar S, Tonetti T. Erector spinae plane block: a systematic qualitative review. Minerva Anestesiol 2019;85:308-19. DOI: 10.23736/S0375-9393.18.13341-4.

6. Tsui BC, Fonseca A, Munshey F, McFadyen G, Caruso TJ. The erector spinae plane (ESP) block: A pooled review of 242 cases. J Clin Anesth 2018; 53: 29-34.