Anesth Analg 2007; 105:1848-1851
© 2007 International Anesthesia Research Society
doi: 10.1213/01.ane.0000286135.21333.fd
ANALGESIA
Thoracic Paravertebral Block for Breast Cancer Surgery: A Randomized Double-Blind Study
Jytte F. Moller, MD, PhD*,
Lone Nikolajsen, MD, PhD* ,
Svein Aage Rodt, MD, PhD*,
Hanne Ronning, MD , and
Palle S. Carlsson, MD, PhD*
From the *Department of Anesthesiology; Danish Pain Research Center; and Department of Abdominal Surgery, Aarhus University Hospital, Denmark.
Address correspondence to Lone Nikolajsen, MD, PhD, Danish Pain Research Center, Aarhus University Hospital, Norrebrogade 44, Bldg. 1 A, 8000 Aarhus C, Denmark. Address e-mail to nikolajsen{at}dadlnet.dk.
Abstract
BACKGROUND: We examined in this randomized, double-blind study whether a multilevel paravertebral block performed before general anesthesia with propofol and a laryngeal mask enhances postoperative analgesia after breast cancer surgery.
METHODS: Eighty-eight patients were randomized to receive paravertebral injections with either ropivacaine 0.5% (30 mL) or an equivalent amount of isotonic saline. Nine patients were excluded after randomization, thus 79 patients remained for evaluation (ropivacaine, n = 38; placebo, n = 41). Variables of efficacy were the amount of fentanyl delivered by the patient-controlled analgesia device in the postanesthesia care unit (PACU), postoperative pain measured on a numeric rating scale at regular intervals from the day of surgery and until the second postoperative day.
RESULTS: The median consumption of fentanyl in the PACU was less in the ropivacaine group compared with the placebo group (0 µg [range: 0–250 µg] versus 100 µg [range: 0–800 µg], P = 0.001). Also, fewer patients in the ropivacaine group reported pain  3 on the numbers rating scale in the PACU (13 vs 31, P < 0.0001). No statistical difference in pain scores or consumption of analgesics could be demonstrated after discharge from the PACU.
CONCLUSIONS: A multilevel paravertebral block provides good analgesia for breast surgery, but the duration of analgesia is briefer than described in previous studies.
Previous studies have shown that paravertebral block (PVB) has the potential to reduce pain and side effects after breast surgery when used in addition to general anesthesia or sedation (1–10). However, except for one study (9), none of the studies were placebo-controlled, which may have caused an overestimation of the positive effects. Likewise, in the study by Kairaluoma et al. (9) (which included a placebo injection group), 60 patients were randomized to receive a single injection of bupivacaine (0.3 mL/kg) or saline (2 mL) at T3 administered by an anesthesiologist who was aware of the treatment allocation. Moreover, one single-injection PVB may not be sufficient to cover all relevant dermatomes. A recent study showed that 97% of patients had adequate loss of sensation with four injections compared with only 11% for single injections (11).
The purpose of the present randomized, double-blind study was to examine whether a multilevel-injection PVB from level C7 through T5 before general anesthesia with the use of propofol and a laryngeal mask enhances postoperative analgesia after breast cancer surgery in a clinical setting.
METHODS
The trial was approved by the local Ethics Committee and was conducted in accordance with the Helsinki Declaration II. Eighty-eight patients scheduled to undergo elective breast tumor resection or mastectomy with radioisotope-guided (sentinel) lymph node biopsy at the Department of Surgery, Aarhus University Hospital, were enrolled after written informed consent was obtained. The enrollment period began on May 25, 2005 and lasted until September 1, 2006. Primary exclusion criteria were inability to provide informed consent, pregnancy or breast-feeding, severe obesity (body mass index >35 kg/m2), coagulation disorders or treatment with anticoagulants, allergy to local anesthetics, severe spine or chest wall deformity, and infection at the thoracic injection site. A secondary exclusion criterion was surgical complications requiring reoperation during the study period. At the preoperative visit, patients were instructed in the use of a numerical rating scale (NRS; 0–10; 0 = no pain, 10 = worst possible pain) and the use of a patient-controlled analgesia (PCA) device (Deltec-Cadd, Astra Tech A/S, Denmark).
Patients were randomly assigned to two equal groups in block sizes of eight patients using sequentially numbered, opaque sealed envelopes. A nurse who was not otherwise involved in the study prepared and released the blinded study medication to the operating room immediately before surgery. The treatment group received paravertebral injections with 0.5% ropivacaine (30 mL) whereas the placebo group received an equivalent volume of isotonic saline. All patients received acetaminophen 1 g perorally (PO) 1–2 h before surgery. After standard monitoring (electrocardiography, noninvasive arterial blood pressure, and pulse oximetry), patients were sedated by midazolam 1–2 mg IV and fentanyl 50–100 µg IV. Paravertebral injections were performed with the patient in the sitting position. The skin and the subcutaneous tissue were anesthesized with 5 mL lidocaine (10 mg/mL), injected 2.5 cm from the midline over the transverse processes from level C7 through T5 on the side of planned block. A 20-gauge Tuohy needle was inserted until the tip of the needle touched the transverse process. The needle was redirected caudally to slide under the transverse process, and advanced into the paravertebral space. After negative aspiration, 5 mL of the study solution was slowly injected. Two senior consultants performed the PVBs to minimize variation in the technique. As the block was performed immediately before surgery, an evaluation of the block quality was not performed.
The patients received a standardized anesthestic technique consisting of propofol (2–3 mg/kg) and fentanyl (50–100 µg) for induction. After loss of eyelash reflex, a laryngeal mask was inserted, and the patients’ lungs were ventilated with 40% oxygen in air. Anesthesia was maintained with propofol, and boluses of fentanyl IV were given at the discretion of the anesthetic nurse if the heart rate or mean arterial blood pressure increased more than 20% from baseline.
Analgesic treatment in the postanesthesia care unit (PACU) consisted of on-demand fentanyl IV by PCA in doses of 50 µg with a 10-min dosing interval (six loading doses per hour). Droperidol 0.625 mg IV and ondansetron 1 mg IV were used to treat postoperative nausea and vomiting (PONV).
In the surgical ward, all patients were given acetaminophen 1 g PO four times daily. Ibuprofen (400–600 mg) PO was used for less severe moderate pain (NRS >3 and <5) and immediate-release oxycodone (5–10 mg) PO was used for pain treatment if the pain at rest was 5–7 on the NRS or if the patient did not tolerate ibuprofen. IV morphine (0.05–0.1 mg/kg) was used for the treatment of severe pain (>7 on the NRS). Ondansetron 1 mg IV and metoclopramide 10 mg IV were used for PONV.
The pain intensity (NRS, 0–10) in the PACU was assessed by the staff at arrival, after 30, 60, 90, and 120 min, and at discharge. Nausea (none, slight, moderate, and severe) and vomiting (yes/no) were recorded after 30, 60, and 90 min. In the surgical ward, the patients themselves recorded the pain intensity at rest and during a standardized movement (folding hands and moving both arms to an angle of 90° to the body) at 10:00 pm on the day of surgery, at 8:00 am, 3:00 pm, and 10:00 pm on the first postoperative day, and at 8:00 am on the second postoperative day. In the morning on the first and second postoperative day, patients recorded the occurrence of PONV in the previous period and whether pain had disturbed their sleep during the night. On the second postoperative day, pain during the paravertebral injections (NRS, 0–10) and back soreness located to the injection sites (present: yes/no) were described. The nurse anesthetist (immediately after anesthesia) and the patient (on the day of discharge) recorded their opinion on whether active treatment (ropivacaine) or placebo (saline) had been administered.
The primary outcome measure was consumption of fentanyl IV in the PACU. A sample size estimate indicated that 38 patients per group would give a power of 90% at a level of 0.05 to detect a difference of 75 µg fentanyl, assuming a variance of 100 µg. To allow for incomplete data collection and exclusion of patients, 88 patients were included in the study. Secondary outcomes were the number of patients in each treatment group with significant postoperative pain (3 on the NRS) and PONV (present/absent). Data were analyzed using the Mann–Whitney rank sum test for unpaired data (presented as medians and ranges). For data concerning the number of patients with pain 3 on the NRS, the analysis was performed on the original categories, not on the presented compressed data. For data on intensity of pain in the PACU, an average value of six pain scores was calculated, giving one value per patient.  2 Test was used for comparison of proportions. A P value <0.05 was considered statistically significant.
RESULTS
One hundred ninety-four patients were assessed for eligibility. Thirty-six patients met the exclusion criteria and 70 declined participation. Eighty-eight patients were randomized to paravertebral injections with ropivacaine (n = 44) or placebo (n = 44). Nine patients were excluded from the study, thus data from 79 patients (ropivacaine, n = 38; placebo, n = 41) remained for analysis (Fig. 1). Significantly more patients in the placebo group underwent simple mastectomy (Table 1).
The median consumption of fentanyl IV was significantly less in the ropivacaine group compared with the control group, both during anesthesia (P < 0.0001) and in the PACU (P = 0.001) (Fig. 2). The mean infusion rate of propofol during anesthesia was 101.6 µg · kg–1 · min–1 (median, range: 75.0–171.6 µg · kg–1 · min–1) versus 119.2 µg · kg–1 · min–1 (median, range: 88.3–184.6 µg · kg–1 · min–1), (ropivacaine versus placebo, P = 0.04). Thirty-three patients did not receive PCA fentanyl IV in the PACU (ropivacaine, n = 23; placebo, n = 10 [P = 0.001]).
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Figure 2. Results are shown as box plots with medians represented by horizontal lines with the 75th percentiles at the top and the 25th percentiles at the bottom (90% percentiles are given as whiskers [the upper whisker is missing for the first bar as the 75th and 90% percentiles are identical]). *P < 0.0001. **P = 0.001. SYMBOL = ropivacaine;  = saline. PACU = postanesthesia care unit.
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The number of patients who reported pain 3 on the NRS was significantly lower in the ropivacaine group during their stay in the PACU (P < 0.0001) (Table 2). In general, the intensity of postoperative pain was low. The median intensity of pain in the PACU was 1 (range: 0–4.6) versus 2.3 (range: 0–7) (ropivacaine versus placebo, P < 0.0001).
During the whole study period, only very few patients experienced nausea or required opioids after PACU discharge. Pain intensity during the paravertebral injections was 0.5 (0–10) (NRS, 0–10 median [range]) (Table 3). Twenty-five patients experienced slight back soreness located to the injection sites after the PVB. Forty-six of 65 nurse anesthetists correctly identified the given treatment, 13 gave wrong answers, and six did not know. Twenty-five of 78 patients correctly identified the given treatment, 21 gave wrong answers, and 32 did not know.
No complications related to the PVB were identified during the present study.
DISCUSSION
In this prospective, randomized, double-blind, placebo- controlled study of a preoperative multilevel PVB for breast cancer surgery, a significant decrease in intraoperative use of fentanyl and propofol was observed. We also found less consumption of PCA fentanyl IV in the PACU as well as a significant decrease in the number of patients who reported 3 on the NRS in the PACU. The pain-reducing effect of the PVB did not significantly outlast the stay in the PACU. Thus, the duration of analgesic effect after PVB was shorter in this study than described in the majority of other studies on analgesia after breast cancer surgery (1–4,7–10). The difference may be attributable to several factors, including study design, technique, and study drug.
Many of the previous studies on PVB in breast surgery suffer from methodological errors: the study design is retrospective, samples are small, and randomization and blinding are either absent or inappropriate. Only one study was placebo-controlled (9). Kairaluoma et al. (9) used a single-level injection at T3 using bupivacaine (0.3 mL/kg) (n = 30) or saline (2 mL) (n = 30). Patients who received bupivacaine needed less IV opioid medication in the PACU and had less pain at rest after 24 h. The use of a much lower injected volume in the placebo group may have unblinded patients to the given treatment. In an observer-blinded study, Pusch et al. (3) randomized 86 patients to receive either a single injection of bupivacaine 0.3 mL/kg at T4 or general anesthesia. Pain during movement was lower in the PVB Group 1, 6, and 24 h after surgery. Similar results were obtained in a randomized study by Klein et al. (4) using a multilevel injection PVB at T1–7. Naja et al. (7) randomized 60 patients to receive either a PVB at T1–5 using a nerve-stimulator guided technique or general anesthesia. Pain scores both at rest and during movement and consumption of analgesics were significantly lower in the PVB group during the first three postoperative days. The study was not blinded.
In respect to the technique itself, there are several approaches to achieve the block. Both single (3,9,12) and multilevel (1,2,4,6,7) paravertebral injections have been reported to provide good analgesia. We used a multilevel injection PVB which has been shown to produce a more reliable sensory block than a single-injection technique (11).
Drugs used for PVB include bupivacaine, ropivacaine, and levobupivacaine with or without epinephrine. Hura et al. (12) recently randomized 70 patients scheduled for mastectomy to receive a single injection of ropivacaine 0.5% or bupivacaine 0.5% at the T4 level. Repeated assessments of the sensory blockade were performed at frequent intervals. Both drugs provided good analgesia, but ropivacaine was characterized by a more rapid onset, a larger initial spread, and a longer duration of the blockade. In the present study, ropivacaine 0.5% was used, thus selection of local anesthetic did not likely affect our results.
The present study has certain limitations. Despite randomization, significantly more patients in the placebo group underwent simple mastectomy. It can be argued that these patients suffered from less postoperative pain but, in general, the pain intensity was low in all patients. Outcome measures were based on the time of day rather than the time after PVB because the patients underwent at very different times of the day, making it difficult to use time after PVB, especially in patients who were scheduled for surgery in the afternoon. The blinded conditions did not allow us to perform a clinical assessment of the sensory blockade. However, the nurses could reliably guess the group assignment in 70% of cases.
In conclusion, a multilevel PVB with ropivacaine provides good analgesia for breast surgery, but the effect is of short duration.
Footnotes
Accepted for publication August 3, 2007.
Reprints will not be available from the author.
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