Table of Contents  
ORIGINAL ARTICLE
Year : 2015  |  Volume : 8  |  Issue : 3  |  Page : 287-293

Bilateral single bupivacaine injection ultrasound-guided paravertebral block facilitates early extubation and reduces perioperative opioids requirements in on-pump pediatric cardiac surgery


Department of Anesthesia and Surgical Intensive Care, Faculty of Medicine, Mansoura University, Mansoura, Egypt

Date of Submission31-Jan-2015
Date of Acceptance16-Mar-2015
Date of Web Publication29-Jul-2015

Correspondence Address:
Ibrahim I Abd El Baser
Department of Anesthesia and Surgical Intensive Care, Faculty of Medicine, Mansoura University, 2 El-Gomhouria Street, Mansoura 35516
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1687-7934.159001

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  Abstract 

Background
Paravertebral block (PVB) is a simple and easy technique with low incidence of complications and contraindications. The aim of the current study is to test the hypothesis that bilateral single-dose PVB may facilitate early extubation and reduce perioperative opioid requirements in pediatric patients submitted for open heart surgery by median sternotomy.
Patients and methods
A total of 70 pediatric patients submitted for open heart surgery by median sternotomy were randomized into two groups. The control group (n = 35) received 0.4 ml/kg normal saline with fentanyl 2 mg/ml, whereas for the bupivacaine group (n = 35) 0.4 ml/kg bupivacaine 0.25% with fentanyl 2 mg/ml was injected down each side of the paravertebral space. Heart rate, mean arterial blood pressure, perioperative opioid requirements, operating room extubation, time to extubation, postextubation PaO 2 , PaCO 2 , postoperative objective pain discomfort score, ICU length of stay, and postoperative complications were recorded.
Results
Heart rate and invasive mean arterial blood pressure were significantly lower in the bupivacaine group compared with the control group, after skin incision, after sternotomy, 15 min after cardiopulmonary bypass, and after the closure of sternum. Perioperative opioid requirements were significantly lower in the bupivacaine group than in the control group. The number of extubations in operating room was significantly higher, and time to extubation was significantly lower in the bupivacaine group compared with the control group. Postoperative pain score was significantly lower at 1, 2, and 6 h, and ICU length of stay was significantly shorter in the bupivacaine group than in the control group.
Conclusion
Bilateral single bupivacaine dose PVB is a safe and effective technique that facilitates early extubation and provides good intraoperative and postoperative analgesia that results in reduced perioperative opioid requirements in pediatric patients submitted for open heart surgery by median sternotomy.

Keywords: bupivacaine, cardiopulmonary bypass, early extubation, paravertebral block, pediatric, sternotomy


How to cite this article:
El Bendary HM, Abd El Baser II. Bilateral single bupivacaine injection ultrasound-guided paravertebral block facilitates early extubation and reduces perioperative opioids requirements in on-pump pediatric cardiac surgery . Ain-Shams J Anaesthesiol 2015;8:287-93

How to cite this URL:
El Bendary HM, Abd El Baser II. Bilateral single bupivacaine injection ultrasound-guided paravertebral block facilitates early extubation and reduces perioperative opioids requirements in on-pump pediatric cardiac surgery . Ain-Shams J Anaesthesiol [serial online] 2015 [cited 2019 Sep 21];8:287-93. Available from: http://www.asja.eg.net/text.asp?2015/8/3/287/159001


  Introduction Top


Pain following cardiac surgery may be intense, originating from various sources including the incision, intraoperative tissue retraction and dissection, vascular cannulation sites, chest tubes, and stainless-steel wire sutures [1] . Regional anesthesia may attenuate adverse physiologic stress responses associated with cardiothoracic surgery, including alterations in circulatory (tachycardia, hypertension, vasoconstriction), metabolic (increased catabolism), immunologic (impaired immune response), and hemostatic (platelet activation) systems [2] . The use of regional anesthesia combined with light general anesthesia may facilitate early tracheal extubation after cardiac surgery in infants and children [3] .

Paravertebral block (PVB) is a technically simple and relatively easy technique of regional anesthesia, with low incidence of complications and contraindications. Ultrasound is becoming an alternative way to identify the paravertebral space (PVS) and perform PVB compared with traditional landmark-guided method. Ultrasound allows visualization of the PVS before PVB, defining the safe depth of needle insertion by determining the distance from the skin to transverse process and to the pleura, as well as visualizing in real time the spread of local anesthetic. The above aspects may translate into improved results, increased effectiveness of PVB, and reduced complications [4] .

Bilateral PVB has been used successfully in abdominal vascular surgery [5] , bilateral reduction mammoplasty [6] , and for laparoscopic cholecystectomy [7] .

Until now, no study has been conducted to evaluate the efficacy of bilateral PVB in pediatric open heart surgery, and thus the aim of the current study is to test the hypothesis that bilateral single bupivacaine dose injection ultrasound-guided PVB may facilitate early extubation and reduce perioperative opioid requirements in pediatric patients submitted for open heart surgery by median sternotomy.


  Patients and methods Top


After approval of the local ethics committee of our institution and obtaining informed consent from all patients' guardians, this double-blind controlled randomized study (envelop method) was conducted on 70 pediatric patients, with age ranging from 2 to 6 years of either sex. The pediatric patients were submitted for on-pump elective correction of simple congenital heart diseases by median sternotomy at Mansoura University Children Hospital from June 2014 to January 2015. Exclusion criteria included previous back injury or surgery which would preclude the performance of needle puncture, kyphoscoliosis, infection of the skin and subcutaneous tissue at the site of needle puncture, hypersensitivity to local anesthetics, presence of tumor in the paravertebral area, coagulation disorders, redo open heart surgery, endocarditis, renal, hepatic or pulmonary disease, heart failure, and moderate to severe pulmonary hypertension.

Patients were premedicated with intramuscular 0.1 mg/kg midazolam and 0.015 mg/kg atropine sulfate 15 min before induction of general anesthesia. Arterial catheter was inserted into the femoral artery under local anesthesia with complete aseptic condition, and five-lead ECG and pulse oximetry were attached to the patient.

Anesthesia was induced with sevoflurane, fentanyl (3 μg/kg intravenously), and rocuronium (0.9 mg/kg intravenously) was used to facilitate tracheal intubation. After induction, a central venous catheter was inserted into the right internal jugular vein. Anesthesia was maintained with sevoflurane (1-3%) inspired in combination with oxygen 50% in air and rocuronium (0.3 mg/kg/h) and fentanyl (1 μg/kg/h). Incremental doses of fentanyl (3-5 μg/kg) were given if systolic arterial blood pressure and/or heart rate (HR) increased by more than 20% above baseline. Neuromuscular blockade was reversed at the end of surgery if the patient was a candidate for extubation by 0.02 mg/kg atropine and 0.04 mg/kg prostigmine.

After induction of anesthesia, the patient was placed in the prone position; the puncture site was lateral to the spinous process of the third or fourth thoracic vertebrae. The PVS was identified by ultrasound using high-frequency linear probe, in plane technique, and the procedure was conducted on both sides of the spine, that is, bilateral paravertebral single injection. The patients were randomly allocated into two groups using closed envelops method.

Control group (n = 35): patients received a mixture of 0.4 ml/kg normal saline with fentanyl 2 μg/ml injected down each side of the PVS.

Bupivacaine group (n = 35): patients received a mixture of 0.4 ml/kg bupivacaine 0.25% with fentanyl 2 μg/ml injected down each side of the PVS.

All PVBs were performed by an anesthetist who was not aware of the study solutions and randomization; another anesthetist was involved in patients data collection.

In all patients, the heart was approached through a standard median sternotomy. The ascending aorta, superior vena cava, and inferior vena cava were cannulated for cardiopulmonary bypass (CPB) using a membrane oxygenator and a roller pump with an arterial line filter, after elevation of the activated clotting time above 480 s, following full patient heparinization with heparin (300-400 IU/kg). Perfusion was a nonpulsatile pump flow with an average rate around (100-150 ml/kg/min). A pH-stat carbon dioxide management strategy (blood gas measurements corrected to body temperature) was used. Moderate hemodilution and moderate systemic hypothermia (32°C) were allowed. After aortic cross-clamping, all patients received cold blood cardioplegia. The cardioplegia was delivered (20 ml/kg for the first dose and 10 ml/kg for subsequent doses) in an anterograde manner in the aortic root after cross-clamping of the aorta. Hematocrit was maintained between 25 and 30% during CPB, with addition of blood as necessary, and anesthesia was maintained by propofol infusion (200 mg diluted in 100 ml dextrose 5%) (50-200 μg/kg/min) after adding 2 mg/kg to the CPB prime. Near the end of completing the repair of cardiac defects, rewarming was started and the aortic cross-clamp was removed after removal of air bubbles from the heart. Ventilation was started when the heart started to eject blood. After fulfilling the criteria of weaning from CPB, patients were separated from the bypass and protamine was administered to reverse heparin.

Postoperative care was standardized for all patients and extubation was accomplished at the earliest clinically appropriate time. In ICU, each child enrolled in the study was followed up for 24 h postoperatively.

Recorded data

HR and invasive mean arterial blood pressure (MAP) were recorded; before induction of anesthesia (basal value), after induction of anesthesia, after skin incision, after sternotomy, 15 min after CPB, and after closure of the sternum. Total dose of intraoperative fentanyl requirements (μg/kg), aortic cross-clamping time (min), CPB time (min), lowest temperature on CPB (°C), spontaneous recovery of the heart, need for cardioversion, need of intropic support, and its dose and duration of surgery (min) were recorded.

The number of patients who were extubated in the operating room (within 15 min of the end of surgery) was recorded. Time to extubation (h) and postextubation PaO 2 , PaCO 2 were assessed every 3 h for 12 h. Postoperative pain was assessed at 1, 2, 6, 12 h after extubation, and was managed according to the objective pain discomfort score (OPDS) in children [8] .

Blood pressure:

2: >20% above the preoperative value.

1: 11-20% above the preoperative value.

0: ±10% of the preoperative value.

Crying:

2: Crying not responding to tender, loving, care.

1: Crying but responds to tender, loving, care.

0: Not crying.

Moving:

2: Thrashing.

1: Restless.

0: None.

Agitation:

2: Hysterical.

1: Mild.

0: Patient asleep or calm.

Verbal:

2: Moderate pain (localized verbally or by pointing).

1: Mild pain (can't localize).

0: Asleep or no pain.

Minimum score: 0.

Maximum score: 10.

The higher the score, the greater the pain experience for the child.

Morphine (0.05-0.1 mg/kg) intravenously was given if the pain score exceeded 4, and the total dose of morphine consumption for 12 h postoperatively and the time to the first analgesic request were recorded. ICU length of stay and postoperative complications (the need for reintubation, nausea and vomiting, pruritus, respiratory depression, and neurological deficits) were reported.

Statistical analysis

The power of this clinical trial was prospectively calculated using the G Power (USA) analysis program. Using a priory power analysis with accuracy mode calculations with OPDS as the primary variant and assuming type I error protection of 0.05 and an effect size convention of 0.8, a total sample size of 70 patients (35 patients in each group) produced a power of 95%.

The statistical analysis of data was performed by using IBM Corp., released 2013 (IBM SPSS Statistics for Windows, version 22.0; IBM Corp., Armonk, New York, USA). The distribution of data was done by mean ± SD for quantitative data, frequency, and proportion for qualitative data and median (range) for nonparametric data. The analysis of the data was performed to test statistically significant difference between groups. OPDS was analyzed by MannWhitney U-test. For quantitative date, student unpaired t-test was used to compare between two groups. χ2 -test was used for qualitative data. P is significant if less than or equal to 0.05 at confidence interval 95%.


  Results Top


The demographic data and surgical parameters were comparable in both groups [Table 1]. In the present study, the HR and the invasive MAP were significantly lower (P < 0.05) in the bupivacaine group when compared with the control group, after skin incision, after sternotomy, 15 min after CPB, and after closure of the sternum [Figure 1] and [Figure 2], respectively.

The total dose of intraoperative fentanyl was significantly lower in the bupivacaine group than in the control group [Table 2]. The operative parameters (aortic cross-clamping time, CPB time, temperature on CPB, and duration of surgery) showed nonsignificant differences between the studied groups [Table 2].
Figure 1: Heart rate (beats/min) in the studied groups. Data are expressed in mean ± SD. P is signifi cant if less than or equal to 0.05 when comparing the bupivacaine group with the control group at the time points.

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Figure 2: Mean arterial blood pressure (mmHg) in the studied groups. Data are expressed in mean ± SD. P is signifi cant if less than or equal to 0.05 when comparing the bupivacaine group with the control group at the same time po ints.

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Table 1: Patient demographic data and type of surgery in the studied groups

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Table 2: Intraoperative variables [total dose of fentanyl (¦Ìg/kg), bypass time (min), aortic cross clamp time (min), temperature on CPB (°C) and duration of surgery (min)] in the studied groups

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In this study, there were no significant differences between the two investigated groups in the criteria of weaning from CPB with regard to the spontaneous recovery of the heart, need for cardioversion, and need of intropic support and its dose.

In the current study, the number of patients who were extubated in the operating room was significantly higher (P = 0.005) in the bupivacaine group than in the control group, seven (20%) and 0 (0%), respectively [Table 3]. The mean time to extubation was significantly lower (P = 0.000) in the bupivacaine group when compared with the control group [Table 3].
Table 3: Postoperative variables in the studied groups

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In the present study, postoperative OPDS was significantly lower (P < 0.001) at 1, 2, 6 h in the bupivacaine group when compared with the control group at the same time points [Table 4].
Table 4: Postoperative objective pain discomfort score

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Time to the first analgesic request was significantly longer in the bupivacaine group when compared with the control group, a significantly longer duration of effective analgesia (OPDS <4) was encountered in the bupivacaine group (P < 0.001) [Table 3]. The total postoperative morphine consumption in the first 12 h after extubation was significantly lower in the bupivacaine group compared with the control group (P < 0.001) [Table 3].

Postextubation PaO 2 showed no significant differences between the two studied groups [Figure 3], but postextubation PaCO 2 was significantly higher (P < 0.001) at 3 h and at 6 h in the bupivacaine group when compared with the control group at the same time points [Figure 4].
Figure 3: Postextubation PaO2 in the studied groups. Data are expressed in mean ± SD. No significant differences between the studied groups.

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Figure 4: Postextubation PaCO2 in the studied groups. Data are expressed in mean ± SD. P is signifi cant if less than or equal to 0.05 when comparing the bupivacaine group with the control group at the same time points.

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As shown in [Table 3], ICU length of stay was significantly shorter in the bupivacaine group than in the control group. Nausea and vomiting were significantly more frequent (P = 0.023) in the control group than in the bupivacaine group, the incidence of pruritus was comparable in the studied groups, and no case required reintubation in ICU [Table 3].


  Discussion Top


The findings of this randomized, controlled study demonstrated that bilateral single bupivacaine dose injection ultrasound-guided PVB in combination with general anesthesia was a safe and effective technique that facilitated early extubation and provided not only good quality of analgesia, but also significantly reduced perioperative opioid consumption in addition to attenuation of intraoperative hemodynamic stress responses in on-pump pediatric cardiac surgery.

Paravertebral nerve blocks (PVBs) can provide excellent intraoperative anesthetic and postoperative analgesic conditions with less adverse effects and fewer contraindications than central neural blocks [9] . The PVB avoids the severe autonomic dysfunction seen with neuraxial techniques [10] . Thoracic PVB provides better postoperative analgesia when compared with intercostal nerve blocks, intrapleural analgesia, spinal analgesia with opiates, and intravenous opioid-based analgesia. This results in reduced postoperative pain and opioid requirement [11] .

The thoracic PVS is a wedge-shaped space that lies on sides of the vertebral column. The boundaries of the space are: posteriorly, the superior costotransverse ligament; anterolaterally, the parietal pleura; and medially, the vertebral body, the intervertebral disc, and the intervertebral foramen. It contains the fatty tissue, within which lies the intercostal (spinal) nerve, the dorsal ramus, the intercostal vessels, the rami communicantes, and the sympathetic chain. It communicates medially with the epidural space and laterally with the intercostal space [12] .

Ultrasound guidance has been successfully introduced for a large spectrum of regional anesthetic techniques, and could also be applicable for the PVB to provide direct visualization of PVS puncture, the spread of local anesthetic, and reducing the frequency of complications [13] .

The present study showed that intraoperative HR and MAP were significantly lower in the bupivacaine group than in the control group. This is in accordance with a previous study that found both HR and arterial blood pressure to be lowered after paravertebral administration of local anesthetic, probably indicating the onset of sympathetic blockade so that there was good control of the hemodynamic response to surgical stimuli [14] . In the present study, the total intraoperative fentanyl requirements were significantly lower in the bupivacaine group than in the control group, denoting the efficacy of the PVB with bupivacaine as intraoperative analgesic modality not only to produce effective analgesia intraoperatively, but also to attenuate the hemodynamic stress response.

In the current study, the number of patients who were extubated in the operating room was significantly higher in the bupivacaine group than in the control group. In addition, the time to extubation was significantly shorter in the bupivacaine than in the control group. This is in accordance with Hammer et al. [15] who reported that the use of a combination of regional (subarachnoid or epidural) plus general anesthesia in children having repair of congenital heart diseases using CPB, facilitated early extubation compared with the control group who had cardiac surgery without a regional technique. In addition, CantÓ et al. [14] found that when using bilateral continuous PVB combined with general anesthesia in on-pump cardiac surgery, the times to extubation were short, as were ICU stays. Very early extubation in children after open heart surgery does not promote cardiodepressive effects. It is a safe procedure that helps to reduce the unnecessary and prolonged mechanical ventilation of children after CPB surgery [16] .

In the current study, OPDS was significantly lower and the total postoperative morphine consumption was significantly decreased in association with longer duration of first analgesic request in the bupivacaine group compared with the control group. In agreement with these results, Vogt et al. [17] studied the effect of single-injection PVB for postoperative pain treatment after thoracoscopic surgery and they found low pain scores at rest and on coughing. In another study, Berta et al. [18] reported that single-injection PVB provided clinically relevant postoperative analgesia in children undergoing major renal surgery.

This study showed that postextubation PaCO 2 was significantly higher in the bupivacaine group than in the control group, which was self-limiting and returned to normal within 6 h. Kloth and Baum [19] reported that early extubation of children after cardiac surgery is associated with transient mild-to-moderate respiratory acidosis, which is self-limiting and requires no treatment.

In the current study, no complications of PVB were noted, except for nausea and vomiting that were significantly higher in the control group than in the bupivacaine group. In addition, pruritus occurred in both groups but was statistically nonsignificant. Batra et al. [20] reported that postoperative nausea and vomiting are significantly lower in patients given PVB compared with general anesthesia.

The current study has certain limitations, including that single-injection techniques are time limited by the duration of action of local anesthetic used. In addition, one of the potential study design drawbacks is the shorter duration of postoperative follow-up for analgesia; we recommend further study including long-time follow-up for at least 36 h postoperatively. Further studies including third group with ultrasound-guided bilateral continuous PVB are needed.


  Conclusion Top


This study confirmed the hypothesis that bilateral single bupivacaine dose injection ultrasound-guided PVB is a safe and effective technique that facilitates early extubation, and provides good intraoperative and postoperative analgesia, which results in reduced perioperative opioid requirements in pediatric patients submitted for open heart surgery by median sternotomy.


  Acknowledgements Top


Conflicts of interest

None declared.

 
  References Top

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Cantó M, Sánchez MJ, Casas MA, Bataller ML. Bilateral paravertebral blockade for conventional cardiac surgery. Anaesthesia 2003; 58:365-370.  Back to cited text no. 14
    
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Hammer GB, Ngo K, Macario A. A retrospective examination of regional plus general anesthesia in children undergoing open heart surgery. Anesth Analg 2000; 90:1020-1024.  Back to cited text no. 15
    
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Berta E, Spanhel J, Smakal O, Smolka V, Gabrhelik T, Lönnqvist PA. Single injection paravertebral block for renal surgery in children. Paediatr Anaesth 2008;18:593-597.  Back to cited text no. 18
    
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]


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