A prospective study to compare the quality of analgesia after breast cancer surgery using pectoral nerve block versus thoracic paravertebral block:

Introduction

Breast cancer is the most common cancer among women and the incidence of breast cancer continues to rise. Most women will experience acute post operative pain after breast cancer surgery. Acute post operative pain is an integral risk factor for the development of chronic pain after breast cancer surgery.

Postoperative pain is of prime concern following breast cancer surgeries. The main objective of providing post operative analgesia is to make the patient comfortable without pain, improve early ambulation, improve respiratory function and early restoration of her routine life. Thoracic paravertebral block²¹ and thoracic epidural block are widely used for anaesthesia and postoperative pain management after breast cancer surgeries. Pectoral nerve block is a newer technique reported by Blanco et al.¹ This study is designed to compare the quality of analgesia after Modified Radical Mastectomy using Pectoral nerve block and Thoracic Paravertebral block, in terms of, the time for the first request of rescue analgesic, 24 hrs analgesic requirement, Visual Analogue Score for pain at rest at 1 and 6 hours postoperatively, Hemodynamic parameters.

PECS block is performed with the patient in supine position by placing the ipsilateral upper limb in abduction, with a 50mm needle using a linear USG probe of high frequency (6-13 MHz), placed at infra clavicular region directly above first rib. In PECS 1, the drug is injected between pectoralis major and minor muscles. In PECS 2, the USG probe is moved towards the axilla till serratus anterior muscle is identified above second, third and fourth ribs and the drug is injected into the fascial plane between the pectoralis minor and serratus anterior muscle.² Thoracic Paravertebral block is performed with the patient in sitting position at the level of 4^th thoracic vertebra with a low resistant technique using an 18G Tuohy needle. The tip of the spinous process is marked on the skin. A para sagittal line is drawn 2.5cms lateral to the midline. At this point, the needle is advanced perpendicularly seeking contact with transverse process of 4^th thoracic vertebra, then sliding the needle caudally for 1-1.5cms into the paravertebral space. After negative aspiration for blood and csf, the drug is injected.

Materials and Methods

After obtaining Institutional Ethical Committee (Govt. Kilpauk Medical College) clearance, written informed consent was taken from 60 patients, aged 30 to 60 years, with carcinoma breast stage 1 & 2, scheduled for modified radical mastectomy during January 2017 to June 2017. Patients were excluded if there was involvement of the upper, outer quadrant, an allergy or sensitivity to local anaesthetics, spine or chestwall deformities or active infection at the injection site, BMI more than or equal to 35/kg/m^2, impaired ability to communicate (e.g., confusion, poor hearing or language barrier), uncontrolled diabetes mellitus, systemic hypertension, severe cardiovascular disease, patients on beta blocker therapy, pregnant patients and Lactating mothers, patients with Coagulation disorders or receiving anticoagulant therapy, sensory block on the contralateral side after paravertebral block, surgical time exceeding 2 hrs. During preoperative visit, demographic data was recorded and Visual Analogue Score (VAS of 1-10) was explained to the patients. A total of 60 patients were allocated according to computer generated sequence into two equal groups, Group 1(PECS-30) & group 2(TPB-30). Group 1 received USG guided PECS block with a high frequency linear probe, 10 ml of 0.25% bupivacaine was injected between pectoralis major & minor, 20 ml of 0.25% bupivacaine was injected between pectoralis minor & serratus anterior. Group B received a single ipsilateral paravertebral block, at T4 level with 20ml of 0.25% bupivacaine. The sensory level was tested with pin prick before induction of general anaesthesia.

Patients were premedicated with Inj. Glycopyrrolate 10mcg/kg IV, Inj. midazolam 0.01mg/kg IV, Inj. fentanyl 2mcg/kg IV. Preoxygenated with 100% oxygen for at least 3 minutes under closed circuit. Induction was done with Inj.Propofol 2mg/kg and Atracurium 0.5mg/kg. Intubated with endotracheal tube of appropriate size(7 or 7.5 mm ID) for the patient and secured in a proper manner after checking bilateral equal breath sounds. Maintenance was done with nitrous oxide and oxygen in the ratio of 2:1 and sevoflurane 1-2%. Duration of surgery of 2 hours was included in the study

At the end of surgery, patients were extubated after reversal of neuromuscular blockade by injecting neostigmine (50mcg/kg) and glycopyrrolate (10mcg/kg) and shifted to postoperative care unit. Postoperatively patients were assessed for the following

Results

A total of 60 patients were included in the study. The two groups were comparable with respect to Age and Weight.(p value > 0.05). The time for the first request of analgesic was longer in the TPB group, 141-360 minutes than in the PNB group, 121-240 minutes (p=< 0.0001) as in figure 1. 24 hours Analgesic consumption was less in the TPB group, which was about 100 mg tramadol compared to PNB group which required 300mg of tramadol. (p=< 0.0001) as shown in Figure 2. The VAS scores at rest at 1 hour and 6 hours postoperatively in TPB group was 0 and 2 while in PNB group it was 2 and 4. (p=< 0.0001) as in Figure 3 . With regards to hemodynamic parameters, the mean Heart rates before block, pre- induction, post induction & postoperative periods in TPB group were 90.23, 92.13, 96.47, 72.07 while in PNB group it was 97.07, 99.30, 101.53, 85.24 (p=<0.0001). The MAP before block, pre-induction, post- induction & postoperative periods in TPB group w ere 93.63, 92.27, 84.63, 74.47 while in P NB group it was 99.57, 99.47, 90.20, 91.10 (p=< 0.0001).

Figure 1

First rescue analgesic distribution

Figure 2

24 Hours analgesic consumption groups

Figure 3

Visual Analog Scale

Discussion

This study shows that thoracic paravertebral block is superior to pectoral nerve block, in terms of time for the request of first analgesic, 24 hours analgesic consumption, VAS scores at 1 and 6 hours at rest.

Pectoral nerve block is easy to perform, simpler and without any complications but the level of analgesia is lesser than thoracic paravertebral block. It can be performed in supine position and the patient acceptance was also better because the procedure was less invasive. No complications occurred in the pectoral nerve block group in the study. The level of analgesia was lesser because its an interfascial plane block where the drug is injected in between the muscle planes, blocking the pectoral, intercostobrachial,3,4,5,6 intercostal nerves.

With respect to thoracic paravertebral block, the analgesia can be attributed to the containment of the space, limiting anaesthetic drug diffusion and prolonged afferent blockade. The only limitation associated with this technique are the complications²⁰ associated with the block, like pneumothorax, pleural puncture and vascular puncture. These can be avoided by the use of ultrasound guided block.¹⁷ There was one patient where there was epidural spread of the drug in our study. Postoperative analgesia can be prolonged by catheter placement in the paravertebral space & using 0.0625% or 0.125% bupivacaine at a rate of 3 to 10 ml/hr. Postoperative analgesia is possible with other techniques like thoracic epidural which is associated with postural hypotension due to sympathectomy and neurological injury. Thoracic paravertebral block has a minimal risk of neurological injury and being unilateral, sympathectomy causes minimal hypotension. The postoperative pulmonary function was preserved and coughing was effective in patients who received paravertebral block. There was good hemodynamic stability and no patients developed significant hypotension, bradycardia or desaturation. It is considered one of the oldest blocks, which came to light by Hugo Sellheim in 1905. However, it went into neglect until the work by Eason and Wyatt,¹² who renewed interest, especially in thoracic paravertebral block where a single injection provides analgesia over six dermatomes.

In our study, we found thoracic paravertebral block had lower VAS scores, prolonged duration of analgesia and lesser analgesic requirements compared to pectoral nerve block. We did not encounter any complications except for epidural spread in two patients.

Results

Thoracic paravertebral block reduces postoperative pain scores, increases the time for first rescue analgesic requirement and decreases the analgesic requirement in the postoperative period compared to pectoral nerve block

Source of Funding

None.

Conflict of Interest

None.

Reference