|Year : 2020 | Volume
| Issue : 3 | Page : 320-325
Analgesic efficacy of continuous subcutaneous presternal bupivacaine infusion vs ultrasound-guided bilateral pectoral nerve block in poststernotomy pain
Mofeed A Abdelmaboud
Department of Anesthesia and Intensive Care, Al-Azhar University, Cairo, Egypt
|Date of Submission||15-Nov-2019|
|Date of Decision||18-Nov-2019|
|Date of Acceptance||30-Dec-2019|
|Date of Web Publication||2-Oct-2020|
MD Mofeed A Abdelmaboud
Department of Anesthesia and Intensive Care, Al-Azhar Faculty of Medicine for Boys, Cairo 12992
Source of Support: None, Conflict of Interest: None
Background The most common cause of pain after cardiac surgery is median sternotomy. Poor postoperative (PO) pain control has serious effect on pulmonary and cardiovascular systems and induces stress and hyperglycemia. Good PO analgesia helps early recovery and discharge.
Aim The primary aim was to compare analgesic efficacy of continuous presternal bupivacaine infusion and ultrasound-guided bilateral pectoral nerve 2 block (Pec 2). The secondary aim was to evaluate their efficacy in controlling respiratory parameters, duration of PO ventilation, ICU stay, and hospital stay.
Patients and methods A total of 100 patients of American Society of Anesthesiologists status II were randomly divided into group I, which received continuous presternal bupivacaine infusion, and group II, which received ultrasound bilateral Pec 2 block. PO visual analog scale (VAS) was recorded at extubation, 3, 6, 12, 18, and 24 h. Pain severity was divided into four grades: no pain, VAS less than 4; mild, VAS 4–5; moderate, VAS 6–7; and severe, VAS greater than 7. Morphine, bupivacaine consumption (mg), and number of request of analgesia in first PO 24 h and inspiratory flow rate (IFR) (l/min) at extubation, 3, 6, 12, 18, and 24 h were recorded. Arterial blood gas parameters were recorded at extubation, 3, 6, 12, and 24 h. Duration of PO ventilation (min), ICU stay (h), and hospital stay (days) were recorded.
Results PO VAS, pain severity, IFR, and arterial oxygen tension/inspired oxygen fraction (PaO2/FIO2) were significantly higher in group II at all study times. Morphine, bupivacaine consumption, and number of request of analgesia in first PO 24 h were significantly higher in group I. Duration of PO ventilation, ICU stay, and hospital stay were significantly longer in group I.
Conclusion First, Pec 2 block was safe and effective in controlling sternotomy pain with lower VAS and pain severity, less bupivacaine, morphine consumption, and less request of PO analgesia. Second, Pec 2 block showed better IFR and PaO2/FIO2, with shorter duration of PO ventilation, ICU stay, and hospital stay.
Keywords: analgesic efficacy, bilateral pectoral nerve 2 block, continuous pre-sternal bupivacaine infusion, post-sternotomy pain, ultrasound
|How to cite this article:|
Abdelmaboud MA. Analgesic efficacy of continuous subcutaneous presternal bupivacaine infusion vs ultrasound-guided bilateral pectoral nerve block in poststernotomy pain. Sci J Al-Azhar Med Fac Girls 2020;4:320-5
|How to cite this URL:|
Abdelmaboud MA. Analgesic efficacy of continuous subcutaneous presternal bupivacaine infusion vs ultrasound-guided bilateral pectoral nerve block in poststernotomy pain. Sci J Al-Azhar Med Fac Girls [serial online] 2020 [cited 2020 Oct 31];4:320-5. Available from: http://www.sjamf.eg.net/text.asp?2020/4/3/320/296967
| Introduction|| |
Midline sternotomy for cardiac surgery can be associated with remarkable postoperative (PO) pain and discomfort .
Inadequate pain management decreases the capacity to cough with increased risk of atelectasis and delayed recovery. Effective pain control after cardiac surgery allows early weaning from ventilation with early hospital discharge . Parenteral opioids are the most commonly used analgesics in such patients which can cause undesirable adverse effects as nausea and vomiting, sedation, and respiratory depression .
Continuous bilateral subcutaneous presternal infusion of local anesthetic through multibore catheters provides a nociceptive block of the anterior branches of intercostal nerves at the lateral margins of the sternum .
Traditionally, in Pec 1 block, injection is done between pectoralis major and minor muscles, whereas in Pec 2 block in addition to Pec 1, another injection is done between pectoralis minor and serratus anterior. The technique of administering Pec 2 block after surgery without combination with Pec 1 has been named by the authors as modified Pec 2 (mPec 2) block .
Pec 1 block aims to block the medial and lateral pectoral nerves, whereas Pec 2 block aims to block the anterior divisions of the thoracic intercostal nerves from T2 to T6, long thoracic nerve, and thoracodorsal nerve. The anterior divisions of the thoracic intercostal nerves (from T2 to T6) lie at the back between the posterior intercostal membrane and the pleura and run in plane between the intercostal muscles as far as the sternum. The long thoracic nerve (or serratus anterior nerve) arises from C5 to C7 and enters the axilla behind the rest of the brachial plexus and rests on serratus anterior muscle .
| Aim|| |
The primary outcome was to compare the analgesic efficacy [PO visual analog scale (VAS), severity of pain and morphine and bupivacaine consumption] of continuous presternal bupivacaine infusion and ultrasound (US)-guided bilateral Pec 2 block in controlling poststernotomy pain. The secondary outcome was to evaluate their efficacy in controlling respiratory parameters [PO inspiratory flow rate (IFR), pH, arterial carbon dioxide tension (PaCO2), arterial oxygen tension/inspired oxygen fraction (PaO2/FIO2), PO ventilation duration, and duration of ICU and hospital stay].
Sample size justification
Med Cal version 184.108.40.206 program ‘Ostend’ Belgium was used for sample size calculation, which is a statistical calculator based on confidence interval of 95% and 80% study power with 5% α error. According to a previous study by Kumar et al. , it can be relied on in this study, and according to this value, minimal produced sample size of 93 cases was enough to find such difference. Assuming 5% dropout, the sample size was 100 cases, subdivided into two equal groups.
| Patients and methods|| |
This prospective randomized controlled study was conducted after approval from Anesthesia and Intensive Care Department, Al-Azhar Faculty of Medicine, and from Local Ethics Committee and taking informed written consent from each patient, It was done at Al-Hussein University Hospital in the period from February 2018 to July 2019.
A total of 100 patients aged 31–60 years of both sexes, with American Society of Anesthesiologists physical status II, who underwent valve surgeries either mitral valve replacement or aortic valve replacement through midline sternotomy under general anesthesia were included in this study.
Exclusion criteria included patients with hemodynamic instability, previous sternotomy, emergency surgery, pre-existing coagulopathy, preoperative poor left ventricular function (ejection fraction <40%), kidney or liver diseases, pre-existing neurological or pulmonary dysfunctions, pre-existing infection at the block site, allergy to local anesthetics, prolonged cardiopulmonary bypass (>120 min), intraoperative inotropic support (dobutamine >5 µg/kg/min or epinephrine infusion >1 µg/min), patients required intra-aortic balloon pump, and patients with prolonged PO ventilation of more than 24 h.
The preoperative routine cardiac medications were continued till the morning of surgery.
Preoperatively, patients were trained to report pain using  VAS that marked from 0 to 10, where 0 indicates no pain and 10 indicates the worst imaginable pain.
All operations were performed by the same surgical team via median sternotomy.
All patients received injection of fentanyl 3–5 μg/kg with induction of anesthesia for intraoperative analgesia.
After confirming hemodynamic stability, minimal drain output, and satisfactory blood gases and electrolytes, the patients were randomly allocated into two equal groups of 50 patients each by using computer generated randomization numbers, which were concealed in opaque envelopes that were opened after patients’ enrolment. Group I (bupivacaine infusion group) received continuous subcutaneous presternal bupivacaine infusion, whereas group II (Pec group) received US-guided bilateral Pec 2 block.
In group I, after sternal wiring, epidural catheter (Epidural Catheter 20 G; 2675–1 Nishikata, Koshi Gaya-Shi, Saitama, Japan) was positioned anterior to the sternum in the subcutaneous tissue during wound closure. The syringe pump was filled with 0.125 ml bupivacaine (Markyreneo; Depeiky for Pharmaceutical Industries, Zone 11 block 12014 Obour City). The catheter was connected to syringe pump (Injectomat Agilia Fresenius Kabi, Three Corporate Drive, Lake Zurich, Illinois, USA), and then continuous infusion of bupivacaine at a fixed rate of 5 ml/h started at skin closure. The catheter was removed after 24 h.
In group II, bilateral Pec 2 block was done after skin closure under linear US guidance (12 MHz). After complete aseptic condition, Pec 2 block was performed using a 20 G 5 cm needle, with the patient in supine position with the arm slightly abducted. The probe was placed perpendicular to the midpoint of the clavicle along its inferior border and then moved inferolaterally until the pectoralis major, the pectoralis minor, and the serratus anterior muscles were identified at the level of the third and fourth ribs ([Figure 1]). All PEC blocks were done by a single operator with previous experience in the technique (>50 times).
The needle was inserted in-plane with the US probe. A volume of 20 ml of 0.125 bupivacaine was injected in the fascial plane between pectoralis minor and serratus anterior muscle, followed by injection of 10 ml in the fascial plane between pectoralis major and minor muscles. The block was done similarly on the opposite side. Overall, 5 ml of 0.125% bupivacaine was infiltrated in the skin around the mediastinal drain. Attention was taken not to exceed the toxic dose of bupivacaine (3 mg/kg). PEC block failed in three patients, and those patients were excluded from the study and replaced by another three patients.
At the end of surgery, neuromuscular blocker was not antagonized, patients were transferred to the ICU and remained intubated and mechanically ventilated (SIMV mode, respiratory rate 14/ min, I : E ratio 1 : 3, with the lowest FIO2 that keep oxygen saturation >90%) (Drager, Infinity C 300, Drager Medical GmbH Moislinger Allee, Lubeck, Germany).
Patients were extubated once they fulfilled the extubation criteria which included adequate airway reflexes, absence of arrhythmias, hemodynamic stability, acceptable blood gases (pH >7.30, arterial carbon dioxide tension <50 mmHg, and arterial oxygen tension >60 mmHg) at FIO2 of 0.4, normothermia, and mediastinal drainage (<100 ml/h for 2 h).
VAS was assessed at extubation (V0) and then at 3, 6, 12, 18, and 24 h PO (V1, V2, V3, V4, and V5). Pain severity was divided according to VAS score into four grades: no pain (VAS <4), mild (VAS 4–5), moderate (VAS 6–7), and severe (VAS >7).
Incentive spirometry was done at similar time intervals (S0, S1, S2, S3, S4, and S5) to indicate the IFR (l/min) by assessing the number of balls raised (1 ball=600 ml, 2 balls=900 ml, and 3 balls=1200 ml).
pH, arterial carbon dioxide tension (PaCO2), and PaO2/FIO2 were recorded before induction, at extubation, and at 6, 12, and 24 h PO.
The PO ventilation duration (min) (from arrival to the ICU till extubation), ICU stay (h), and hospital stay (days) were recorded.
All patients were given PO analgesia in the form of intravenous paracetamol 1 g every 6 h. Morphine 2 mg was given intravenously if VAS score was greater than or equal to 3. The total amount of morphine (mg) given during the first PO 24 h and number of request of analgesia (morphine) in first PO 24 h were recorded.
After 24 h, intravenous paracetamol 1 g was given on patient’s request.
Total amount of bupivacaine (mg) consumption over first PO 24 h was recorded.
SPSS version 17 program (SPSS Inc., Chicago, Illinois, USA), was used to enter data and statistical analysis. Data were presented as mean±SD, number, median, and interquartile range). Comparison between the two groups was performed using unpaired Student t-tests for parametric data, Mann–Whitney test for nonparametric ordinal data, and χ2-test for data collected as number. P value less than 0.05 was considered as statistically significant.
| Results|| |
The two groups were comparable regarding demographic and surgical data ([Table 1]).
VAS in the first PO 24 h was significantly higher in group I than group II at all study times ([Table 2]).
Severity of pain was significantly higher in group I than group II at all times of examination ([Table 3]).
Total morphine and bupivacaine consumption in the first 24 h and number of request of analgesia (morphine) in first PO 24 h were significantly higher in group I than group II ([Table 4]).
|Table 4 Total morphine and bupivacaine consumption (mg) in the first postoperative 24 h and number of request of analgesia (morphine) in first postoperative 24 h|
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PO IFR (l/min) was significantly higher in group II than group I at all times of study ([Table 5]).
There were no significant differences between the two groups regarding blood pH and PaCO2, whereas PaO2/FIO2 was significantly higher in group II than group I at all PO study times ([Table 6]).
Regarding PO ventilation duration (min), ICU stay (h), and hospital stay (days), they were significantly longer in group I than group II ([Table 7]).
|Table 7 Postoperative ventilation duration (min), ICU stay (h), and hospital stay (days)|
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| Discussion|| |
The most often cause of pain after cardiac surgery is the median sternotomy . The most commonly used analgesics in such patients are the parental opioids, which can cause undesirable effects such as respiratory depression, sedation, nausea, and vomiting .
This study was designed to examine the efficacy of presternal infusion of bupivacaine 0.25% and US-guided bilateral pectoral nerve block in poststernotomy pain.
Thus study showed that PO VAS was significantly higher in bupivacaine infusion group than Pec group at all observation times, severity of pain was significantly higher in group I than group II at all times of examination, and total morphine (mg) consumption and number of request of analgesia (morphine) in first PO 24 h were significantly higher in bupivacaine infusion group than Pec group. Kumar et al.  observed that VAS scores at rest and cough were significantly lower in Pec group than control group at 0, 3, 6, 12, and 18 h from extubation (P<0.05), but at 24 h, VAS scores were comparable between the two groups. Nasr et al.  showed that there was lower PO VAS score and marked reduction in morphine requirements (mg) in bupivacaine infusion group compared with control group (8.6±0.94 vs 18.83±3.4 mg, respectively; P=0.02) and attributed such a result to placing catheters for sternal wound infusion closer to the anterior branches of the intercostal nerves that improved the analgesic efficacy. Liu et al.  demonstrated that pectoral block provided immediate and sustained pain relief with reduction of opioid requirement. Richard et al.  observed that continuous bilateral pectoral nerve 2 block may reduce pain and opioid consumption and extend duration of analgesia after median sternotomy. Chiu et al.  found that continuous presternal bupivacaine infusion provided short and long-term pain relief for thoracotomy. Eljezi et al. , Dowling et al. , and Koukis et al. ) showed a reduction in PO pain and opioid requirement after local anesthetic infusion. Magnano et al.  and Agarwal et al.  showed that local anesthetic presternal infusion after median sternotomy did not reduce PO pain, and VAS score. Magnano et al.  attributed their results to using a catheter with few holes only at the tip, which was ineffective for long median sternotomy, and the lower wound segment might be uncovered by anesthetic drug, and advised to prolong the duration of bupivacaine infusion to be more effective for delayed PO pain. Agarwal et al.  attributed the failure of their technique to earlier time of discontinuation than planned owing to wound infection.
The present study showed that total bupivacaine (mg) consumption in the first PO 24 h was significantly higher in bupivacaine infusion group (150 mg) than Pec group (43.75 mg), and it was extremely below the toxic dose of bupivacaine (3 mg/kg), especially in Pec group.
This study demonstrated that PO IFR (l/min) was significantly higher in Pec group than bupivacaine infusion group at all time of observation, and this might be owing to lesser PO pain, which facilitated expulsion of secretion and rapid pulmonary rehabilitation with shorter ventilatory duration, ICU, and hospital stay. Kumar et al.  observed that peak IFR was higher in Pecs group as compared with control group at 0, 3, 6, 12, 18, and 24 h (P<0.05).
The current study showed that there were no significant differences between the two groups regarding blood pH and PaCO2, whereas PaO2/FIO2 was significantly higher in Pec group than bupivacaine infusion group at all PO study times, which might be owing to better pain control with better respiration. Nasr et al.  observed that PaCO2 and pH were accepted in both bupivacaine infusion group and control group, with no significant differences, but PaO2/FIO2 was significantly higher in bupivacaine infusion group compared with control group (P<0.05). Eljezi et al  demonstrated no improvement in the PO respiratory functions despite improvement of analgesia in the ropivacaine infusion group and explained such result to that sternotomy pain was a minor factor in the respiratory dysfunction observed.The present study demonstrated that PO ventilation time (min), ICU stay (h), and hospital stay (days) were significantly longer in bupivacaine infusion group than Pec group. Nasr et al.  showed that there was shorter extubation time in bupivacaine infusion group (117±10 min) compared with the control group (195±19 min), but no differences in ICU or hospital stay duration. Richard et al.  observed that continuous bilateral pectoral nerve block reduced length of hospital stay. Eljezi et al. , Dowling et al. , and Koukis et al.  showed a significant decrease in hospital stay time. Magnano et al.  and Agarwal et al.  showed that local anesthetic presternal infusion after median sternotomy did not reduce extubation time.
| Conclusion|| |
First, US-guided bilateral Pec block is a safe and effective technique for controlling poststernotomy pain than continuous presternal bupivacaine infusion with lower VAS score and pain severity, less bupivacaine (mg) and morphine consumption, and less number of request of analgesia (morphine). Second, PEC block showed better IFR and PaO2/FIO2, with shorter duration of ventilation, ICU stay, and hospital stay.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]