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Paravertebral Blockade for Day-Case Breast Augmentation

A Randomized Clinical Trial

Gardiner, Sarah, BMBS*; Rudkin, Glenda, MBBS, FANZCA; Cooter, Rodney, MBBS, MD, FRACS; Field, John, PhD, AStat§; Bond, Malcolm, PhD||

doi: 10.1213/ANE.0b013e318264ba33
Ambulatory Anesthesiology
Free
SDC

BACKGROUND: Bilateral breast augmentation is an increasingly popular day-case procedure. Local infiltration with sedation is routinely used for its ease of application compared with the more complex and potentially riskier paravertebral blockade (PVB). We hypothesized that ropivacaine injected by experienced anesthesia providers into the paravertebral space as a PVB was more effective than ropivacaine injected by the operating surgeon (plastic surgeon) directly into the zone of surgical dissection.

METHODS: Forty female patients who were ASA physical status I or II and undergoing bilateral subpectoral cosmetic breast augmentation were recruited for participation in a prospective, randomized, single-blind study. Patients were randomized to 1 of 2 groups: ropivacaine via PVB, or surgical infiltration of ropivacaine. In both groups, the surgeon was asked to infiltrate the appropriate area with either saline (PVB group) or ropivacaine (local infiltration group). Both groups were sedated with propofol, titrated to effect. The plastic surgeon was blinded to the solution injected. Data collected included demographic characteristics, intraoperative cooperation scores, recovery room postoperative nausea and vomiting, analgesia use, and visual analog scale pain scores. All patients were asked to complete a preoperative anxiety and quality of recovery questionnaire and to record their pain scores and analgesia requirements on discharge. The outcome measures were (i) intraoperative patient cooperation as assessed by the plastic surgeon, (ii) propofol requirement, (iii) postoperative pain, and (iv) quality of recovery.

RESULTS: Forty patients completed the study. PVB improved intraoperative cooperation (significance of difference P < 0.001, WMWodds = 6.69 with 95% 1-sided confidence interval CI ≥2.85), reduced propofol requirement (significance of difference P = 0.005, WMWodds = 0.35, CI <0.69), and decreased average postoperative pain in the home environment (significance of difference P = 0.007, WMWodds = 0.38, CI <0.73). There were no PVB complications. Only patients from the surgical infiltration group required rescue analgesics (30%, significance of difference = 0.01).

CONCLUSIONS: In a limited number of patients, we found that PVB is superior to direct surgical infiltration of ropivacaine for bilateral breast augmentation in same-day surgery. These advantages need to be balanced against the potential risks of PVB, especially in an office setting.

Published ahead of print September 13, 2012

From the *Flinders University School of Medicine, Adelaide; Specialist Anaesthetic Services, Adelaide; Waverley House Plastic Surgery Centre, Adelaide; §John Field Consulting Pty. Ltd., Adelaide; and ||Department of General Practice, Flinders University, Adelaide, Australia.

Accepted for publication May 30, 2012.

Published ahead of print September 13, 2012

Funding: There was no additional funding required; all costs were consistent with standard clinical care.

The authors declare no conflicts of interest.

Sarah Gardiner, BMBS, is currently affiliated with the Plastic Surgery Department, The Queen Elizabeth Hospital, Adelaide, SA, Australia.

Reprints will not be available from the authors.

Address correspondence to Sarah Gardiner, BMBS, Waverley House Plastic Surgery Centre, 360 South Terrace, Adelaide, SA 5000, Australia. Address e-mail to sarah.gardiner@health.sa.gov.au.

Cosmetic bilateral breast augmentation is an increasingly popular procedure. In the United Kingdom, a 275% increase from 2002 to 2007a has been reported and 2009 figures from America show a 208% increase over the last 12 years.b With this increase in bilateral breast augmentation has come a concomitant demand for same-day surgery. The challenge is to provide safe, effective anesthesia with sedation, accommodate day-case time constraints, and deliver a cost-effective outcome. The anesthesia provider using local anesthesia with sedation encounters many complexities: anxious patients, surgeons who require a still patient, and system demands for a short recovery period with minimal complications.

Various anesthetic techniques other than general anesthesia have improved patient outcomes; these include reduced postoperative nausea and vomiting (PONV), improved postoperative pain control, reduced opioid use, and improved recovery of function.1–3 These techniques, when used in combination with sedation anesthesia rather than general anesthesia, can minimize postoperative complications.1,4,5 Local anesthesia infiltration,6 intercostal block,3 and paravertebral block1 have all been used in the challenging day-case setting.

Bilateral breast augmentation has been safely performed in ambulatory surgery facilities. We have previously shown that paravertebral blockade (PVB) with sedation provides good surgical anesthesia, reliable and complete pain relief, and minimal PONV.4 Surgically infiltrated local anesthetic has also been used in combination with general anesthesia or sedation for surgery.6 Surgical infiltration can have improved benefits in recovery time and a reduction in PONV.6 Regional anesthetic techniques such as PVB have potentially significant risks including pneumothorax, intravascular injection of local anesthetic, pleural puncture, and local anesthetic toxicity because of its fast uptake.7 Additionally, the success of the PVB is largely dependent on the skill level of the anesthesiologist performing the block.4 Conversely, surgical infiltration is an easier technique to perform and may avoid the difficulties associated with PVB while still providing good anesthesia intraoperatively and in the early postoperative period.8 Whereas it is well established that surgical infiltration has proven efficacy in postoperative pain relief in other clinical settings,9 its effectiveness in bilateral breast augmentation in a day-case setting remains controversial.

Although there are risks associated with PVB, there may be potential advantages. Therefore, the primary aim of this study was to investigate whether there are significant differences in clinical outcomes between ropivacaine administered as PVB anesthesia and direct surgical site injection with ropivacaine, in patients undergoing surgery under sedation.

Our hypothesis was that, compared with surgically infiltrated ropivacaine, the use of PVB as the ropivacaine injection technique under sedation will result in (i) better intraoperative patient cooperation, requiring less sedation; (ii) reduced pain scores and less PONV, both initially and at home; and (iii) improved quality of recovery.

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METHODS

Forty patients were recruited (20 in each group) for a prospective, randomized, single-blind study. The sample size was based on a study power of 80% and α value of 0.05 (1-tailed), with the ability to detect a “large” effect size.10 That is, the study was powered only to detect a substantial group difference, in favor of PVB. The study was approved by the Ethics Committee of St. Andrew’s Hospital (Adelaide, South Australia).

Female patients ASA I or II (classified as physical status according to the ASA) undergoing subpectoral bilateral cosmetic breast augmentation, defined as elective cosmetic surgery, were eligible for participation. Exclusion criteria included coagulopathy, infection at an injection site, prior pathology/bilateral mastectomy, prepectoral implant procedure, neurological disease, poor respiratory reserve, general anesthesia choice or requirement, allergy to local anesthetic, prior spinal surgery in the region of the block, or significant thoracic scoliosis or kyphosis.

Patients were recruited on the day of surgery by a coinvestigator. After obtaining written consent, the patients were randomized via a sealed nontransparent envelope to receive either surgical infiltration of ropivacaine or PVB with ropivacaine from a computer-generated randomization table. Patients were asked to complete a 20-point-scale questionnaire (Appendix 1) on preoperative anxiety status.11

Appendix 1

Appendix 1

Demographic characteristics including age (years), weight (kilograms), height (meters), smoking history (yes/no), and nausea and/or vomiting history (yes/no including history of motion sickness and previous anesthesia reaction) were requested.

The PVB and intraoperative anesthesia were performed by the same anesthesiologist for each procedure. The patient was sedated with IV midazolam. PVB was performed with the patient in a sitting position and using a 22-gauge Tuohy needle and loss-of-resistance technique.12 The single injection technique was used to minimize risk of pleural puncture while still providing multiple-level anesthesia from T2-6 dermatomes with a bilateral T4 PVB.4 Once the transverse process of vertebra T4 was contacted, the needle was angled in a slightly cephalad direction and advanced to the end point described as loss of resistance (approximately 1 cm beyond the transverse process). After identification of the T4 paravertebral space, 3 mg·kg−1 of 0.75% ropivacaine (with 1:400,000 adrenaline) was diluted with saline to a total of 40 mL, and 20 mL of the final solution was injected bilaterally. After block administration, each patient was assessed for spread by cold sensation testing of the anterior chest dermatomes.

All patients were given IV Hartmann fluid (1 L) and supplemental oxygen via a Hudson mask. Standard sedation with IV midazolam (3.5–4 mg, range varied according to body mass index and previous drug use) and intraoperative fentanyl (100 µg) were given with a propofol infusion (10 mg·mL−1). Propofol was titrated for patient comfort and light sleep using a variable infusion rate (TOP 5300 infusion pump) with total propofol dose summated. No other intraoperative sedatives or opioids were administered, unless the combined opinion of the surgeon and anesthesiologist dictated otherwise for patient safety and comfort. Patients were monitored (arterial blood pressure, heart rate, pulse oximeter saturation, electrocardiogram) throughout the procedure.

All patients were appropriately draped and positioned supine, with both arms restrained in padded gutter arm boards at 70° shoulder abduction. Skin incisions were anesthetized with local anesthetic (lidocaine 2% with standardized 1:80,000 adrenaline) by the same surgeon, 6.6 mL per side (this equated to 3 ampules of 2.2 mL each of pre-prepared dental cartridge local anesthetic). Pre-prepared 20-mL syringe aliquots were administered to the surgical field of all patients. The syringes contained either ropivacaine (in the surgical infiltration group) or saline (in the PVB group). This ensured blinding of the surgeon to the anesthetic technique and maintained objectivity for completion of the Surgical Patient Cooperation Scale (Appendix 2), which ranged from 1 (no cooperation, procedure abandoned) to 5 (full cooperation).13 The implant pocket was dissected with a dual plane technique (subpectoral and partial prepectoral dissections). Textured cohesive gel, mostly anatomical, implants were used; implant weight was recorded in grams. At the completion of surgery, propofol sedation was discontinued and 2 surgical drain tubes were inserted into the operative site. The patient was then transferred to a recliner chair in the recovery room.

Appendix 2

Appendix 2

Recovery room arrival time was noted, together with patient’s pain score as described on the Visual Analog Scale (VAS) 0 to 10 ruler. Episodes of nausea and/or vomiting (yes or no), request for antiemetics, additional analgesia or need for vasopressors, along with VAS pain scores were noted at 30-minute intervals until discharge. Antiemetic management included tropisetron (2 mg IV) and, failing improvement, dexamethasone (8 mg IV) then droperidol (0.6 mg IV). Analgesic requirements were met with oral dextropropoxyphene unless pain scores were >5 on the VAS, and then opioids were administered (oral oxycodone or IV fentanyl).

At the completion of the surgical procedure, the surgeon completed the Surgical Patient Cooperation Scale. The recovery room nurse determined appropriateness for discharge based on the Modified Post Anaesthesia Discharge Scoring System (PADSS) (≥9 on the scoring system).14

On discharge, patients were given charts to record their VAS pain score and oral analgesia (dextropropoxyphene) requirements 4 times daily for the next 3 days, and a quality of recovery score (Appendix 3) to complete on the third day postoperatively. Our staff telephoned patients day 1 postoperatively. Additionally, patients were asked to contact the clinic by phone, which was available 24 hours, if any concerns arose. On the fifth day postoperatively, patients were followed up in the surgical center for drain removal and wound check. The quality of recovery score was developed to elicit a patient-oriented outcome after inpatient anesthesia and surgery.15 Patients reported on 12 areas such as postoperative pain, nausea, general bodily functions, medical follow-up and support, and physical and psychosocial recovery.15

Appendix 3

Appendix 3

All analyses were conducted using the R statistical language.c Count data were reported as n (%), whereas continuous and ordinal data were summarized as mean (SD) for baseline data and median (interquartile range) for outcome data. The analysis was by intention-to-treat and involved all patients who were randomly assigned. Count data were analyzed using Fisher exact test, baseline continuous data with Welch t test, and outcome ordinal and continuous data with Wilcoxon-Mann-Whitney (WMW) tests. For these variables, WMWoddsd and 95% confidence intervals (CIs) were calculated using an R macro (R. G. O’Brien, personal communication, 2012). All tests and CIs for outcome variables were 1-sided. Spearman correlations and bootstrapped CIs were calculated for outcome data.

For any outcome variable Y, WMWodds compares odds of YPVB with those of YSI with precision given by the 95% CI. For example, if WMWodds is <1, then patients with PVB are more likely to have lower values than patients with surgical infiltration. Accordingly, if WMWodds is >1, patients with PVB are more likely to have higher values than patients with surgical infiltration. A CI containing 1 is evidence that there is no significant difference.

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RESULTS

Patient recruitment commenced in September 2006 and concluded in September 2009. The 40 patients, all ASA physical status I or II, were randomly assigned to the 2 anesthesia groups. No refusals to participate were received after randomization and all patients completed the study requirements. There was no significant difference between the 2 groups’ baseline characteristics (Table 1).

Table 1

Table 1

All patients received fentanyl (100 µg) and midazolam (average dose 3 mg with a range of 3.0–3.5 mg). PVB success was confirmed in all patients with bilateral cold sensation testing. One patient broke the sedation protocol, as a result of poor cooperation and movement on the operating table, so a joint decision by the anesthesiologist and surgeon was made to administer an additional 23 mL of surgical infiltration to achieve safe operating conditions. This patient was in the surgical infiltration group. No complications occurred intraoperatively in the PVB group. The surgical infiltration group required significantly higher doses of propofol (mg·kg·min−1) and had lower intraoperative cooperation scores (Table 2a). The dose variables are all highly correlated, and highly negatively correlated with intraoperative cooperation (Table 2b).

Table 2b

Table 2b

Table 2a

Table 2a

All patients proceeded to the recovery room at the completion of their surgery for monitoring and provision, as required, of antiemetics and analgesia (Table 3a). Both average and maximum pain were highly correlated, and recovery time was correlated positively with each of these (Table 3b). Anesthesia-related complications in the PVB group included 1 case of bradycardia (defined as heart rate <40 beats·min−1) and 3 cases of hypotension (arterial blood pressure <20 mm Hg below admission). Only 1 patient required ephedrine for hypotension. The surgical infiltration group had 1 patient with both bradycardia and hypotension, which did not require a vasopressor drug. A breach of protocol occurred with 1 patient (surgical infiltration group) who required local anesthetic administered into the surgical drains bilaterally for uncontrollable pain.

Table 3a

Table 3a

Table 3b

Table 3b

There was no difference in the maximum and average pain scores recorded in the recovery room. However, the same findings were not consistent with maximum and average pain scores recorded at home (Table 4). Furthermore, the PVB group had better quality of recovery scores. We had no hospital inpatient admissions or readmissions for uncontrolled pain. One patient (surgical infiltration group) with a history of chronic back pain required a doctor’s home visit and an opioid was prescribed. Additionally, another surgical infiltration group patient required opioid at home; this patient broke the recovery room protocol with local anesthetic administration into both surgical drains, as described above.

Table 4a

Table 4a

Table 4b

Table 4b

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DISCUSSION

In the day-case setting with patients having IV sedation, both surgical infiltration and PVB have some benefit.9

This study showed that ropivacaine delivered by an anesthesiologist as a PVB provides some clinical advantages compared with ropivacaine delivered by a plastic surgeon as a direct wound infiltrate. Specifically, less propofol was required to sedate the PVB group, and improved intraoperative surgical conditions were recorded. In the recovery room, requirements for opioids were less in the PVB group. The PVB group also had less pain after discharge and a superior quality of recovery score. Intraoperative cooperation was significantly better in the PVB group (median 5) compared with the surgical infiltration group (median 3). Additionally, we found that the less-cooperative surgical infiltration group needed higher doses of propofol (mg·kg·min−1). The measure of intraoperative cooperation between the 2 groups may have been better measured with a VAS. Poor intraoperative cooperation in 1 patient (surgical infiltration group) required additional local anesthetic to achieve safe operating conditions; on reflection, this patient had a higher than mean preoperative anxiety score, thereby correlating with a poorer intraoperative cooperation. This was the only breach of the intraoperative protocol.

In this study, increased accuracy of propofol dosing would have been achieved if titrated against cerebral function rather than using a subjective analysis of effective sedation. The other limitation of this study is the requirement for a single-blinded trial; a double-blind design could have been more powerful. Also, the measure of intraoperative cooperation of the 2 groups may have been better measured with a visual analysis scale (VAS 0–10).

Postoperative pain scores were satisfactory for all patients in this study: the average pain score in both the recovery room and home environments for both groups was <5 on the VAS. However, 6 of the surgical infiltration group patients required escape opioid analgesia (VAS >5 and not controlled with dextropropoxyphene) in the recovery room; this was significantly more than the PVB group. One patient in this surgical infiltration group, with a history of chronic back pain, required a doctor’s home visit and additional escape opioid analgesia. Although postoperative breast surgery pain is usually most severe in the first 48 hours,16 we found that significantly lower pain scores were recorded at home with the PVB group in this time period. This finding is in contrast to Moller et al.17 who found that reduced pain levels did not carry through to the home environment. However, their series related to breast tumor resection, axillary dissection, or mastectomy, not bilateral breast augmentation, which may be potentially less painful over time.

Moller et al.17 recorded reduced opioid use and lower postoperative pain scores in the postoperative anesthesia care unit, consistent with our findings. Both of these findings add to the body of literature describing PVB as an effective analgesia technique17,18 with reduced levels of PONV,4,18 opioid use,4,19 and opioid-related side effects.4 Indeed, a recent meta-analysis shows that PVB is a feasible and effective method for improved postoperative analgesia, specifically after breast surgery.20 Furthermore, Dabbagh and Elyasi19 highlight the importance of effectively blocking pain pathways to reduce the acute (surgical) stress response. A reduced stress response may have contributed to the significantly better quality of recovery in the PVB group.

The performance of bilateral PVBs in day-surgery patients is controversial, despite 12 published studies (538 patients) reviewed with no reports of systemic toxicity and the incidence of pneumothorax and hypotension being low.21 Because the risks of PVB may be quite significant even though their incidence may be low, some may argue that even incidences of 1:1000 may be too high for ambulatory surgery. Thus, direct surgical infiltration has its protagonists who cite similar benefits with effective postoperative pain control2,6,22 and reduced opioid use.6,22 Sidiropoulou et al.8 suggest that surgical infiltration, as well as providing effective postoperative pain control when compared with PVB (both groups under general anesthesia), has the additional benefit of being a relatively easy technique to perform, thus making it a superior option. We have shown in this randomized, single-blind, prospective trial that PVB is a superior anesthetic technique for intraoperative cooperation, reduced sedation requirement, and better pain control in the postoperative period with improved quality of recovery. It has few contraindications and is associated with a low overall incidence of complications.4,23

Additional benefit was found with earlier discharge times. This may translate into reduced cost associated with extended stays. With careful patient selection based on previous recommendations4 and consideration of preoperative anxiety levels, PVB in the day-case setting is an effective, reliable anesthetic technique with clinical benefits that must be weighed against rare but significant risks.

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DISCLOSURES

Name: Sarah Gardiner, BMBS.

Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.

Attestation: Sarah Gardiner has seen the original study data, reviewed the analysis of the data, approved the final manuscript, and is the author responsible for archiving the study files.

Name: Glenda Rudkin, MBBS, FANZCA.

Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.

Attestation: Glenda Rudkin has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: Rodney Cooter, MBBS, MD, FRACS.

Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.

Attestation: Rodney Cooter has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: John Field, PhD, AStat.

Contribution: This author helped analyze the data and write the manuscript.

Attestation: John Field has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: Malcolm Bond, PhD.

Contribution: This author helped design the study and analyze the data.

Attestation: Malcolm Bond has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

This manuscript was handled by: Peter S. A. Glass, MB, ChB.

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ACKNOWLEDGMENTS

The researchers acknowledge the substantial contributions made by the staff at Waverley House Plastic Surgery Centre.

a British Association for Aesthetic Plastic Surgeons. Available at: http://www.baaps.org.uk/about-us/press-releases/404-surgeons-reveal-uks-largest-ever-breast-augmentation-survey. Accessed April 10, 2010.
Cited Here...

b The American Society for Aesthetic Plastic Surgery, Cosmetic Surgery National Data Bank Statistics. Available at: http://www.surgery.org/sites/default/files/2009stats.pdf. Accessed April 10, 2010.
Cited Here...

c R Development Core Team (2011). R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria. ISBN: 3-900051-07-0. Available at: http://www.R-project.org/.
Cited Here...

d O’Brien RG, Castelloe J. 2006. Exploiting the Link Between the Wilcoxon-Mann-Whitney Test and a Simple Odds Statistic. Available at: http://www.bio.ri.ccf.org/robrien/WMWodds/. Accessed March 2, 2012.
Cited Here...

e Osborne GA, Rudkin GE, Jarvis DA, Young IG, Barlow J, Leppard PI. Intra-operative patient-controlled sedation and patient attitude to control. Anaesthesia 1994;49:287–92.

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REFERENCES

1. Hadzic A, Kerimoglu B, Loreio D, Karaca PE, Claudio RE, Yufa M, Wedderburn R, Santos AC, Thys DM. Paravertebral blocks provide superior same-day recovery over general anaesthesia for patients undergoing inguinal hernia repair. Anesth Analg. 2006;102:1076–81
2. Pacik PT, Nelson CE, Werner C. Pain control in augmentation mammaplasty using indwelling catheters in 687 consecutive patients: data analysis. Aesthet Surg J. 2008;28:631–41
3. Huang TT, Parks DH, Lewis SR. Outpatient breast surgery under intercostal block anaesthesia. Plast Reconstr Surg. 1979;63:299–303
4. Cooter RD, Rudkin GE, Gardiner SE. Day case breast augmentation under paravertebral block: a prospective study of 100 consecutive patients. Aesthetic Plast Surg. 2007;31:666–73
5. Klein SM, Bergh A, Steele SM, Georgiade GS, Greengrass RA. Thoracic paravertebral block for breast surgery. Anesth Analg. 2000;90:1402–5
6. Jabs D, Richards BG, Richards FD. Quantitative effects of tumescent infiltration and bupivacaine injection in decreasing postoperative pain in submuscular breast augmentation. Aesthet Surg J. 2008;28:528–33
7. Naja Z, Lönnqvist PA. Somatic paravertebral nerve blockade: incidence of failed block and complications. Anaesthesia. 2001;56:1184–8
8. Sidiropoulou T, Buonomo O, Fabbi E, Silvi MB, Kostopanagiotou G, Sabato AF, Dauri M. A prospective comparison of continuous wound infiltration with ropivacaine versus single-injection paravertebral block after modified radical mastectomy. Anesth Analg. 2008;106:997–1001
9. Schug SA, Chong C. Pain management after ambulatory surgery. Curr Opin Anaesthesiol. 2009;22:738–43
10. Welkowitz J, Ewen RB, Cohen J Introductory Statistics for the Behavioral Sciences. 19823rd ed New York Academic Press
11. Spielberger CD Manual for the State-Trait Anxiety Inventory (Form Y). 1983 Palo Alto, CA Consulting Psychologists Press
12. Eason MJ, Wyatt R. Paravertebral thoracic block: a reappraisal. Anaesthesia. 1979;34:638–42
13. Osborne GA, Rudkin GE, Jarvis DA, Young IG, Barlow J, Leppard PI. Intra-operative patient-controlled sedation and patient attitude to control. Anaesthesia. 1994;49:287–92
14. Chung F. Discharge criteria: a new trend. Can J Anaesth. 1995;42:1056–8
15. Myles PS, Hunt JO, Nightingale CE, Fletcher H, Beh T, Tanil D, Nagy A, Rubinstein A, Ponsford JL. Development and psychometric testing of a quality of recovery score after general anesthesia and surgery in adults. Anesth Analg. 1998;88:83–90
16. Shapiro FE. Anesthesia for outpatient cosmetic surgery. Curr Opin Anaesthesiol. 2008;21:704–10
17. Moller JF, Nikolajsen L, Rodt SA, Ronning H, Carlsson PS. Thoracic paravertebral block for breast cancer surgery: a randomized double-blind study. Anesth Analg. 2007;105:1848–51
18. Thavaneswaran P, Rudkin GE, Cooter RD, Moyes DG, Perera CL, Maddern GJ. Brief reports: paravertebral block for anesthesia—a systemic review Anesth Analg. 2010;110:1740–4
19. Dabbagh A, Elyasi H. The role of paravertebral block in decreasing postoperative pain in elective breast surgeries. Med Sci Monit. 2007;13:464–7
20. Schnabel A, Reichl SU, Kranke P, Pogatzki-Zahn EM, Zahn PK. Efficacy and safety of paravertebral blocks in breast surgery: a meta-analysis of randomized controlled trials. Br J Anaesth. 2010;105:842–52
21. Richardson J, Lönnqvist PA, Naja Z. Bilateral thoracic paravertebral block: potential and practice. Br J Anaesth. 2011;106:164–71
22. Culliford AT IV, Spector JA, Flores RL, Louie O, Choi M, Karp NS. Intraoperative Sensorcaine significantly improves postoperative pain management in outpatient reduction mammaplasty. Plast Reconstr Surg. 2007;120:840–4
23. Karmakar MK. Thoracic paravertebral block. Anesthesiology. 2001;95:771–80
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