To assess the efficacy of addition of transversus abdominis plane block by continuous infusion of bupivacaine via surgically placed catheter in decreasing the overall use of patient controlled morphine in patients undergoing open nephrectomy- a prospective randomized double blinded study
Background: Transversus abdominis plane (TAP) block is a novel analgesic technique. We analyzed the efficacy of TAP block with bupivacaine, in patients undergoing open nephrectomy in a single-center, prospective, randomized, double blinded trial.
Methods: Twenty patients undergoing open nephrectomy in the lateral decubitus position and having flank incision were included in the study. The participants were divided into two groups: Group A received 0.9 (!!!!unit missing) NaCl through TAP catheter with patient controlled analgesia (PCA) morphine; Group B received 0.2% bupivacaine through TAP catheter along with PCA morphine. Each patient was assessed post-operatively for Numerical rated scale (NRS), sedation score and amount of morphine delivered through PCA pump at 2, 4, 6, 8, 12, 18, 24, 36 and 48 h.
Results: There was no significant difference in the amount of morphine consumed between the control group and bupivacaine group (p > 0.05). None of the patients had sedation score of 4 or above, but sedation scores were usually significantly lower in bupivacaine group (0–6 h). NRS score was lower in bupivacaine group, and significantly higher duration of stay (p = 0.035) was seen in bupivacaine group (5.50 days) compared with the control group (4 days).
Conclusion: TAP block is as efficacious as PCA morphine in upper abdominal surgery. TAP block can be used as an analgesic for parietal pain along with supplementation of opioids for visceral pain when neuraxial block is contraindicated.
Managing post-operative pain is a major concern due to multiple factors such as type, approach and length of surgery, patients’ intrinsic response to the pain and the pharmacologic method adopted.1 Post-operative analgesia have been used in certain types of surgery to decrease post-operative stress response and morbidity, reduce the pain intensity and side effects from analgesics, thus improving the surgical outcome and patient recovery.2
Sympatholytics, local anesthetics, ketamine, steroids, non-steroidal anti-inflammatory drugs and non-pharmacological techniques have been employed to manage post-operative pain.3 Thus, the focus is to minimize post-operative side effects such as nausea and vomiting drowsiness and respiratory depression, thus assisting in early discharge of patients.
The transversus abdominis plane (TAP) block is a novel analgesic technique widely used in the clinical practice for both lower and upper abdominal incisions. The technique involves blocking the sensory nerve supply of a section of the lower abdomen by introducing a local anesthetic. The efficacy of TAP blocks has been reported in various surgeries such as hysterectomy,4 caesarean section5 and appendectomy.6 A study by Milan et al.7 reported that subcostal TAP block was effective in reducing morphine consumption at more than 24 h after liver transplant. Several studies4,8,9,10 have also highlighted that TAP block is an effective method to decrease post-operative pain and side effects of opioids during 24 h post-surgery, up to 48 h occasionally. However, general applicability of this technique is not recommended to due to insufficient information.11.12
Kidney, being a retroperitoneal organ, has a standard surgical approach requiring a flank incision rather than a midline incision, as the latter is transperitoneal and the exposure may be insufficient. However, this surgery is very painful and requires multimodal analgesia for relief to the patient. TAP block has been proven very effective in providing analgesia in such surgeries.8,10,13 In the present study, we analyzed the efficacy of TAP block, using bupivacaine, in patients undergoing open nephrectomy in a single-center, prospective, randomized, double blinded trial.
MATERIALS AND METHODS
Study design and setting
A prospective, randomised, controlled, double blinded study was conducted in the urology operating rooms and wards at the Christian Medical College, Vellore. The study was approved by the Institutional Review Board and Ethics Committee of Christian Medical College, Vellore and was internally funded by Fluid Research Grant of Christian Medical College, Vellore (!!! Please mention Grant Number…else in separate section after ref as per journal guidelines).
Patients were recruited for the study from December 2012 to August 2013 and were selected on the day prior to the surgery. Patients coming for laparotomy for nephrectomy or pyeloplasty were recruited for this study. Patients of age >18 years and undergoing open nephrectomy in the lateral decubitus position and having flank incision were included in the study, whereas patients refusing to participate or those with renal donor nephrectomy, coagulation disorders, history of drug abuse, emergency surgery, pregnancy, critical illness, infected kidney, renal impairment (creatinine > 1.5 mg/dL) or Sepsis were excluded. The participants were divided into two groups: Group A received 0.9 (!!!!unit missing) NaCl through TAP catheter with patient controlled analgesia (PCA) morphine; Group B received 0.2% bupivacaine through TAP catheter along with PCA morphine. The study and its method were explained by the principal investigator to the participants, and written informed consent was obtained. On the day before the surgery, the participant was educated in the use of the Patient Controlled Analgesia (PCA) and also familiarized with 10-point Numerical rated scale (NRS). A score of ‘0’ was assigned for no pain and ’10’ for the worst imaginable pain.
On the day of surgery patients were pre-medicated with diazepam and metoclopramide. Briefly, anaesthesia was induced with propofol (2–3 mg/kg), fentanyl (2 mg/kg) and vecuronium (0.15 mg/kg). Intra-operatively, total fentanyl and morphine used were 4–5 mcg/kg and 0.15 mg/kg, respectively. Intravenous paracetamol (1 g) was given to all patients before skin incision.
After nephrectomy, the surgeons dissected a plane between internal oblique and TA muscle on the upper part of the wound. The muscle layers were then closed in layers. After the peritoneum and TA muscle were closed, an 18 G epidural catheter was inserted inside the upper side of the wound along the length of the wound. The other end of the catheter was brought out away from the incision site and secured on to skin with 3.0 silk. A snap connector was attached to the open end of the catheter to which a flushed bacterial filter was connected. The internal oblique and external oblique were closed and following which subcutaneous tissue and skin were closed. Then, 20 ml of the study drug was injected over 10 min and infusion was started at 5 ml/h. Another intravenous access with a 22G insyte exclusively for PCA morphine was then started. The PCA pump was set up to deliver 1 mg of morphine during activation and lock out time was set at 10 min. There was no background infusion kept. Patient was then transferred to the post anaesthesia care unit for monitoring of vital signs and shifted to ward when patient fulfilled discharge criteria.
Measurement of Study Outcomes
In the post-operative ward, NRS, sedation score and amount of morphine delivered through PCA pump was recorded at 2, 4, 6, 8, 12, 18, 24, 36 and 48 h. Supplemental oxygen via Hudson mask was administered in the ward during the immediate postoperative period for first few hours. Routine postoperative measures to were given to the patient to prevent postoperative pulmonary complications such as incentive spirometry and chest physiotherapy. Signs of bupivacaine and morphine toxicity was observed for and Editor1
The ‘Effect size’ was 2, and the ‘Power’ of the study was 90% with a ‘Significance’ level of 5%. The sample size was thus calculated using the formula:
n = 2 Z1-?/2 + Z1-?/22 * ?2 / S2.
Z1-? = 5% error.
Z1-? = power 90%.
To detect the effect size of 2, a sample size of 50 (n=25 in each arm) was needed with a power of 90% and error of 5%. A total of 52 patients were randomized to group A and group B. Of the total number, 20 patients did not proceed to open laparotomy, 5 patients withdrew from the study on the day of the surgery, 1 patient had bowel perforation during surgery, 2 had pleural injury and 2 patients refused surgery. Two more patients were further excluded in the mid-postoperative period due to sepsis related hypotension and post operative bleeding and the other patient had accidental dislodgement of catheter.
The results are expressed as mean+/- standard deviation (SD). Statistical tests used repeated measures of ANOVA. Students T tests were used for NRS, sedation score and morphine consumption. Categorical data were analysed using Chi-square test or Fisher’s exact test. Mann-Whitney U-test was used for comparing age, BMI, weight, length of stay and duration of surgery. P < 0.05 was considered significant. Statistical analyses were performed with SPSS!!!!!! version 18.0(U.S.A.)!!!!!! RESULTS Demographics Table 1 summarises the patients' demographic information. Both the groups included 10 participants each and no significant difference was seen between the groups in terms of age, gender, height, weight or BMI. Seven out of 10 patients in GROUP A were within normal range BMI of 18.5–25 kg/m2. One patient was underweight (BMI < 18.5) and three were overweight (BMI > 25). In GROUP B four out of eleven were within normal limits of BMI (between 18.5 and 25). One patient was severely underweight (BMI < 15), two were underweight (BMI 15–18.5), three were overweight (BMI 25–30) and one was obese (BMI 30–35) (Figure 2 or 1!!!). Overall, majority of participants (n = 14) belonged to ASA 1 category, of which 11 (CHECK GP A HAS TOTAL 10 ONLY) were in group A and 4 in Group B. Of the 6 participants which belonged to ASA 2 category, all belonged to Group B (Figure 3), (CHECK IF IT CAN BE PLACED HERE, MEANING OF ARS 2 ) of which 3 had diabetes, 1 had hypertension, 1 had hypertension and hypothyroidism, and 1 had hypertension and diabetes. The length of incision was statistically insignificant between the groups (Group A, 11.50 ± 1.5; Group B, 11.75 ± 2.88; p = 0.709) (Table 2). Rib excision may be necessary to obtain access to the kidney. There was an unequal distribution of patients with rib excision between the groups. The control arm had only 1 patient with rib excision while the study arm had 6 patients with rib excision. This was statistically significant difference (p value 0.015). Vitals Comparison Before And After Drug Instillation Table 4 shows the mean vitals before and after drug instillation. Heart rate, systolic blood pressure and diastolic blood pressure were separately noted before the drug instillation. After 20 min of drug instillation vitals were again recorded. In group A, the mean heart rates pre- and post drug instillation were 93.50±5.46 and 90.90± 5.26, respectively, whereas in group B were 90.20± 5.55 and 95±5.63, respectively. The difference in mean heart rates pre- and post drug instillation was insignificant in the groups (Group A, p = 0.168' Group B, p = 0.443). The mean systolic blood pressure in group A pre- and post-drug instillation was 117.70 ± 12.19 and 123.90± 12.28, respectively, whereas in Group B, it was 122.50 ±11.78 and 115.50 ± 11.42, respectively. The difference for Group A and B was statistically insignificant (p = 0.198 and p = 0.82, respectively). The mean diastolic blood pressure in Group A pre- and post-drug instillation was 73.70 ± 8.93and 71.90 ±9.11, whereas in Group B it was 82.00± 11.62 and 76.70 ± 12.26. No significant difference was seen in the groups (P = 0.198 and 0.82, respectively). Furthermore, no significant difference was seen i the duration of surgery between the groups (P = 0.702). Also, the mean amount of fentanyl used in both groups (148 ± 41.04 and 168 ±50.55) and mean amount of morphine used in both groups (7.90 ± 1.91and 7.60 ± 2.04) did not vary significantly. NUMERIC RATED SCALE DURING FIRST AND SECOND POSTOPERATIVE DAY: Table 5 shows the comparison of NRS at different time periods between Group A and Group B following surgery. The highest NRS recorded was at second hour in bupivacaine group is 3.90. Though not statistically significant, pain score in saline Group was higher most of the time. But in both groups the mean NRS was never high. Table 6 shows the comparison of sedation score in Saline group and Bupivacaine group. In bupivacaine group the graph showed a linear trend with a sedation score of two till first six hours. This implies patient was co- operative, conscious and oriented. The difference in Ramsay sedation scores was significant between the 8 to 12th hour postoperatively, where the bupivacaine group was more sedated. There was no incidence of respiratory depression and none of the patient required re- intubation. Additionally, it was seen that mean amount of morphine consumed during 1st and 2nd post operative day increased in both groups. the maximum mean recorded at 36th hour in bupivacaine group. Although there was an increase in morphine consumption during 48 hours of postoperative period, the pain score was low. Also, a significant difference in duration of stay was seen in both the groups (P = 0.035). Overall, post operative nausea and vomiting was experienced by 2 patients n Saline group and none in bupivacaine group (p = 0.474). DISCUSSION The present study was aimed at assessing the efficacy of TAP block with of bupivacaine in patients undergoing open nephrectomy. A study by Hosgood et al.14 reported that use of bupivacaine-TAP block in patients undergoing laparoscopic nephrectomy reduced early morphine requirements but not the overall morphine requirement. Interestingly, in our study, we did not find and difference in the amount of morphine consumed between the control group and bupivacaine group. PCA morphine is reportedly the best form of post-operative analgesia;15 therefore, we offered this to both the groups. Although it has been reportedly associated with respiratory depression,16 it was not seen any group; however, similar post-operative nausea and vomiting was observed in both the groups. None of the patients had sedation score of 4 or above, but sedation scores were usually significantly lower (0–6 h) in bupivacaine group with patients feeling more alert compared with control group The duration of surgery, length of incision and pre and post drug vitals were similar in both groups. The bupivacaine group had 6 patients with rib excision, whereas the saline group had 1 patient. Though not statistically significant, in both the groups, morphine usage increased towards the end of 1st post operative day; however, NRS score was lower in bupivacaine group, suggesting that TAP offered better pain relief after rib excision and crushing of the intercostal nerve. There was no break through pain and hence rescue analgesia was never given at any point of time. Some studies have reported that TAP blocks decrease the number post operative days.17,18 However, we observed significantly higher duration of stay (p = 0.035) in bupivacaine group (5.50 days) compared with the control group (4 days), which could be attributed to the more number of patients with rib excision in bupivacaine group requiring prolonged opioid before discharge. The study had a few limitations. First, the number of patients was very less; hence a study with larger patient numbers is recommended. Second, since multiholed TAP catheters were not available, epidural catheters were used in the study. Third, data regarding patient satisfaction and NRS during cough/exercise was not recorded, and plasma levels of bupivacaine, morphine-6-glucoronide and morphine-3-glucoronide were not quantified. CONCLUSION The present study showed that TAP block is as efficacious as PCA morphine in upper abdominal surgery. 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