Patients receiving the TAP block with bupivacaine required less tramadol (presented as mean [SD], 156.5 [185.4] vs. 471.4 [372.2] mg; P=0.001) and ondansetron 3.7 ± 4.2 vs. 7.1 ± 4.6mg (P=0.012) compared to the control group during their hospital stay. There were no differences in the amount of paracetamol, codeine or cyclizine required in either of the groups (P=0.561, 0.561, 0.827; respectively).
The average length of postoperative stay was 3.7 (1.8) vs. 3.1 (1.1) days in the bupivacaine and control groups (P=0.242). There was no significant difference in the time to the re-introduction of fluids (TAP block with bupivacaine 1.1 ± 0.28 vs. control 1.1 ± 0.2 days; P=0.671), however solid foods were introduced earlier in the TAP block with bupivacaine group compared to the control (1.5 ± 0.51 vs. 1.8 ± 0.5 days; respectively, P=0.037).
Timed Up and Go
Pre-assessment levels of the timed up & go were similar in both groups (P = 0.524). On day 1 postsurgery the time taken to complete the task was significantly longer in both groups. Seven out of 24 patients receiving bupivacaine and 8 out of 22 in the control group felt unable to perform the assessment on day 1 (P=0.837). On day 3, patients in both groups performed the task quicker compared to day 1 but the time was significantly prolonged compared to the pre operative duration (P=0.002, 0.003). One patient in the bupivacaine group was unable to complete the assessment on day 3. However, all patients in the control group were able to perform the task (P=1.00; Figure 2A).
The preoperative grip strength assessed using the dominant hand was similar between groups (P=0.417). Levels fell significantly in both groups on day 1 after surgery and to a numerically lower level in the control group compared to those receiving bupivacaine (P=0.058). Levels recovered on day 3 postsurgery and were comparable to preoperative levels in both groups (P>0.05). All patients were able to perform the assessment on the scheduled days (Figure 2B).
This randomized, double-blind, placebo-controlled trial in patients undergoing laparoscopic nephrectomy demonstrated that a TAP block with bupivacaine reduced early morphine requirements. Interestingly, there was no difference in the total amount of morphine required, but patients reported less postoperative pain and required less oral analgesics during their hospital stay.
There is a growing body of evidence in favor of TAP blocks in reducing postoperative pain for various types of surgery (6–8, 11, 12). Nonetheless, the results are inconsistent. A randomised controlled trial by McDonnell et al found that TAP blocks reduced morphine requirements by more than 70% for up to 36 hours and patients had lower visual analogue pain scores for 48 hours after caesarean section. (13) Belavy et al, also found that TAP blocks reduced postoperative analgesic requirements however, the results were less pronounced with no differences in the post operative pain scores. (8) In contrast, Costello et al. (14) found that TAP blocks did not have any beneficial effect after caesarean sections. However, TAP blocks were used in conjunction with long-acting intrathecal opioids, which are extremely effective and likely to reduce the need for morphine after surgery. Two other studies using intrathecal opioids have also reported these findings. (9, 15).
The TAP block procedure used in this study involved a single injection of local anesthetic, which may have potential disadvantages. Bupivacaine has a relatively short duration of action, lasting 6 to 8 hr, and its effectiveness can be dependent on the type of surgery (16). The results from this trial showed that patients receiving a TAP block with bupivacaine required 42% less morphine in the first 6 hr after surgery compared with patients receiving the placebo control. Thereafter, morphine requirements were similar. The duration of action of bupivacaine using this technique is unknown, and the poor vascularization in this region may prolong the effect or may indeed be dependent on the amount and concentration of local anesthetic agent used. Higher concentrations have been used (13); however, there is a risk of toxicity because the local anesthetic may spill over into the adjacent muscle, resulting in high systemic concentrations. Therefore, some caution must be taken (18).
Bupivacaine TAP blocks showed no advantage for patients in terms of nausea and vomiting scores, postoperative recovery, or in the length of hospital stay. Surprisingly, sedation scores were lower in the control group, with more patients feeling more alert on postoperative day 2 compared with the patients receiving a TAP block with bupivacaine. Nonetheless and perhaps most importantly, patients receiving a bupivacaine TAP block had lower visual analog pain scores for 2 days after surgery and experienced less pain at rest and on movement. Furthermore, patients required less tramadol and antiemetics during their hospital stay. Although there was no reduction in the total morphine requirement, the perceived reduction in pain is an important outcome and likely to be of benefit. Pain is influenced by many factors, and studies have shown that a higher use of PCA can be influenced by anxiety and the anticipation of pain (19, 20).
Preemptive analgesia is an effective and standard way of targeting postoperative pain. A recent study by Amr et al (21) in patients undergoing a hysterectomy found that TAP blocks administered before surgery reduced pain and analgesic requirements compared with TAP blocks placed at the end of the surgery. A potential disadvantage of preemptive TAP blocks is that some of their postoperative effect may be lost if surgery is prolonged. The effects of TAP blocks can be prolonged by continuous infusion of the local anesthetic agent by means of an implanted TAP catheter, and this may be more beneficial. A recent study demonstrated that patients undergoing open donor nephrectomy with a flank incision required significantly less morphine and had lower pain scores up to 48 hr after surgery when local anesthetic was continually infused through catheters placed in the TAP for 48 hr after surgery (22). Continuous administration of local anesthetic has also been beneficial in kidney transplant recipients (23). Nonetheless, more evidence is needed to establish the efficacy of this approach. There have also been reports of using an intra-abdominal approach to administering the TAP blocks under direct vision during surgery (24). This has been described as a more simple method that improves accuracy and reduces the risk of damaging the viscera.
The number of patients in the study was informed by a realistic power calculation. Furthermore, it must be taken into consideration that, although the TAP blocks were administered under ultrasound guidance by an experienced consultant anesthetist, in some cases, they may not have been effective. Pinprick sensation can be used to assess sensory blockage and the effectiveness of the TAP block. However, this was avoided in the present trial because blinding could not have been maintained. Complications are also possible, including infection or hematoma at the administration site, nerve damage, transient femoral nerve palsy, and even the potential to damage underlying organs (17, 25). Nonetheless, there were no complications associated with the TAP block procedure in this present study.
In conclusion, the addition of a preemptive bupivacaine-based TAP block in laparoscopic LDN is of benefit in reducing postoperative pain and early postoperative morphine requirements. Future studies should aim to extend the effects of the TAP blocks by investigating the use of TAP catheters to provide continual infusions to optimize the delivery of local anesthetic and prolong the effect.
MATERIALS AND METHODS
Local ethics committee and research and development approval was obtained (clinical trial registration [SRCTN14709684]). A computer-generated sequence of random numbers was used to create an opaque sealed envelope system for a consecutive series of 50 patients randomized in a 1:1 ratio to either TAP blocking with bupivacaine local anesthetic (bupivacaine) or the saline placebo (control). Written consent was obtained the day before surgery. The trial pharmacist opened the opaque randomization envelope and labeled the assigned prefilled syringes (0.375% bupivacaine or normal saline [0.9% sodium chloride]; Bath ASU, Wiltshire, UK) with the trial number and a patient name/number. These syringes were delivered to the consultant anesthetist who was blinded to the treatment group. All members of the nursing, medical, and surgical team apart from the trial administrator/coordinator and the pharmacist were also blinded to the treatment allocation. Patients aged 18 years or over with an American Society of Anaesthesiology (ASA) grade 1 or 2 that had completed the full work-up for laparoscopic donor nephrectomy, including an assessment by the Human Tissue Authority (HTA) and had given written, signed informed consent were eligible for the trial. Patients with a history of relevant drug allergy or who where receiving medical therapies considered to result in tolerance to opioids were excluded from the trial.
All general anesthetics were performed by a member of the consultant anesthetic staff using a standardized technique. In brief, anesthesia was induced with propofol 2.5 to 3 mg/kg and fentanyl 1 to 2 μg/kg and maintained with isofluorane and 50% oxygen in air. Muscle relaxation was achieved with atracurium 1 mg/kg. Intravenous fluids were administered to maintain systolic blood pressure above 100 mmHg.
Tap Block Procedure
All TAP blocks were be performed by a consultant anesthetist experienced in anesthetizing donor nephrectomy patients. All TAP block needles were placed under ultrasound control. After skin preparation with antiseptic, a blunt regional anesthesia needle (22 gauge) was introduced through the skin just cephalad to the anterior superior iliac spine of the pelvis. The needle was introduced until resistance was encountered, indicating that the needle tip was at the external oblique muscle. Gentle advancement of the needle resulted in a “pop” sensation as the needle entered the plane between the external and internal oblique fascial layers. Further gentle advancement of the needle resulted in a second pop, indicating that the needle tip entered the transversus abdominis fascial plane. These maneuvers were performed under direct ultrasound control, which allowed careful delineation of the three lateral muscle layers and ensured that the anesthesia needle was in the correct plane. After careful aspiration to exclude vascular puncture, 20 mL of solution (either 0.375% bupivacaine or 0.9% saline) was injected through the needle into the transversus abdominis plane. The same procedure was then repeated on the contralateral side, again using 20 mL of test solution.
All operations were performed by the same transplant surgical team, the port placement and surgery was standardised and patients received post operative care by the same nursing team on the Transplant ward. In brief, four laparoscopic ports were used: two 12-mm ports placed near to the umbilicus and in an iliac fossa and two 5 mm ports placed in the epigastrium and flank. The ureter and renal vessels were dissected, and then, all of the lateral and posterior attachments of the kidney were divided until the kidney was free on its vascular pedicle. A 6-cm suprapubic retrieval incision was made through a transverse skin incision with division of the abdominal muscles in the midline. An Endocatch II (Covidien; Mansfield, MA) retrieval system was introduced through this retrieval incision. The ureter and renal vessels were secured with clips or staples and then divided. The kidney was captured in the Endocatch bag and removed through the suprapubic retrieval incision. The lengths of wound incisions were recorded.
As prophylaxis against venous thromboembolism, all donors wore TED stockings, and subcutaneous Dalteparin 2500 IU was administered once per day until fully mobile. Donors were allowed to begin mobilization on the first postoperative day and were allowed to start eating and drinking at their own discretion.
All patients received postoperative pain relief using a PCAS delivering 1-mg boluses of morphine with a 5-min lock-out period. Opiate analgesia was discontinued at the discretion of the patient and then replaced by oral analgesia with tramadol (50–100 mg orally up to four times per day) or paracetamol (1 g orally up to four times per day).
The primary endpoint was postoperative morphine requirement and pain scores. Postoperative analgesic use was recorded by the nursing staff and pain team using the standard PCAS form. Daily postoperative pain levels were recorded using visual analog and verbal response scales (0, no pain at rest or movement; 1, no pain at rest and slight pain at movement; 2, intermittent pain at rest and moderate pain on movement; 3, continuous pain at rest and severe pain on movement).
The secondary outcome measures included daily postoperative nausea and vomiting recorded using visual analog and verbal response scales. (0, no nausea and vomiting at rest or movement; 1, no nausea and vomiting at rest and slight nausea and vomiting at movement; 2, intermittent nausea and vomiting at rest and moderate nausea and vomiting on movement; 3, continuous nausea and vomiting at rest and severe nausea and vomiting on movement).
Daily postoperative sedation was recorded and scored as the following: (0, none, patient is alert; 1, mild, awake but drowsy; 2, moderate, asleep but rousable; 3, severe, unrousable).
Adverse events caused by the TAP block procedure including evidence of inflammation or infection at the administration sites or adverse effects of the local anesthetic agent or saline were recorded.
As an assessment of recovery, patients were asked to complete the timed up and go. They were timed as they rose from a chair, walked 3 meters, turned, walked back, and sat down. This was measured before surgery and on postoperative days 1 and 3. A hydraulic hand dynamometer was used to measure grip strength (kg). The scores of 3 successive trials using the dominant hand were measured before surgery and on day 1 and 3 after surgery.
Sample size was estimated on the basis of 24-hr postoperative morphine requirements in a previous series of patients undergoing LDN. This pilot data showed that the normal 24-hr morphine requirement was 37 (11) mg (mean [SD]). For the purposes of sample size calculation, we considered that a clinically important reduction in morphine consumption would be a 50% absolute reduction. Using this data, it was calculated that 20 patients per group would be required for an experimental design incorporating two equal sized groups using α=0.05 and β=0.1, thus giving a power of 90%. To minimize any effect of data loss, 25 patients per group were recruited into the study.
The data were collected prospectively and stored on a computerized database. Comparisons of outcome were made on an intention-to-treat basis. Data are presented as mean (SD). Continuous variables were compared using the unpaired t test with Welch correction.
Categorical variables were compared by means of Fisher exact test. Statistical analysis was performed using Instat and Prism 5 Software (GraphPad Software, San Diego, CA). P<0·050 was considered statistically significant.
The authors thank the University Hospitals of Leicester Pharmacy department for their assistance in this trial.
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Keywords:© 2012 Lippincott Williams & Wilkins, Inc.
Transversus abdominis plane block; Placebo control; Live-donor nephrectomy