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Department of Anesthesiology, St. Luke’s-Roosevelt Hospital Center, College of Physicians and Surgeons of Columbia University, New York, New York
Address correspondence to Admir Hadzic, PhD, MD, Department of Anesthesiology, Travers 701, St. Luke’s-Roosevelt Hospital Center, 1111 Amsterdam Ave., New York, NY 10025. Address e-mail to ah149{at}columbia.edu.
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Introduction |
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Methods |
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PNBs
Patients assigned to receive PNBs were given combined lumbar plexus and sciatic blocks (5). All blocks were performed in the operating room (OR). At the anesthesiologist’s discretion, patients could receive midazolam (2–6 mg) and alfentanil (250–750 µg) by IV injection, in divided doses, before PNBs. Supplemental oxygen (5 L/min) was administered by facemask throughout the procedure. PNBs were performed using a 21-gauge, 100-mm Stimuplex block needle (B. Braun Medical Inc., Bethlehem, PA) and a nerve stimulator (Tracer III; Life-Tech Inc., Houston, TX). A posterior approach to lumbar plexus block was performed with the patient in the lateral decubitus position and after a quadriceps muscle response had been obtained with a current of 0.5–1.0 mA, 30 mL of 2-chloroprocaine (3%) mixed with bicarbonate (1 mEq per 10 mL) and epinephrine (1:300,000) was injected. With the patient in the same position, the classical posterior approach to sciatic block was performed after a twitch of hamstrings, soleus, foot, or toes, had been elicited using a current of 0.2–0.5 mA, and 20 mL of 2-chloroprocaine (3%) with bicarbonate (1 mEq per 10 mL) was injected. After PNBs, surgeons infiltrated the site of the arthroscope’s placement with 5 mL of 1% lidocaine and were allowed to proceed immediately with preparation and surgery without waiting to document full onset of surgical anesthesia. During the procedure, all patients received an IV infusion of propofol.
By protocol, no other intraoperative sedatives or opioids were allowed. Patients with inadequate surgical anesthesia upon incision, or those requiring supplemental opioids, were given GA using propofol for induction, followed by placement of a laryngeal mask airway (LMA). All PNB procedures were performed by senior residents or regional anesthesia fellows under the supervision of an attending anesthesiologist with experience in regional anesthesia. At the conclusion of the procedure and after wound dressing application, the propofol infusion was stopped, and the patient was taken to a Phase I postanesthesia care unit (PACU).
GA
Patients assigned to receive GA were given preoperative dolasetron (12.5 mg) by IV injection, midazolam (1–2 mg), and fentanyl (50–100 µg). After induction of GA with propofol (1.5–2.0 mg/kg), a LMA was inserted, and anesthesia was maintained with desflurane in a mixture of 50:50 nitrous oxide in oxygen. The concentration of desflurane was maintained between 3% and 6%, as monitored by mass spectrometry (Capnomac UltimaTM; Datex-Ohmeda, Helsinki, Finland). By design, fentanyl was the only opioid allowed intraoperatively, and its administration was left to the discretion of the anesthesia team caring for the patient. Muscle relaxants and reversal drugs were not allowed. Surgeons were asked to begin surgical preparation of the limb as soon as the LMA was placed. At the end of the surgical procedure, the surgeons injected 20 mL of bupivacaine (0.25%) into the knee joint. The inhaled anesthetics were discontinued upon conclusion of surgery and before the wound dressing and/or cast application.
Recovery
At the conclusion of the procedure, patients were taken to the Phase I PACU, where nurses (unaware of the study and the anesthetic technique used) evaluated the patient using a modified Aldrete score and made a decision regarding the patient’s eligibility to bypass Phase I PACU. Only patients with an Aldrete score of 
9 and not requiring treatment of pain with IV morphine sulfate, as indicated by a visual analog score (VAS) of <3 (range, 1–10), were eligible to bypass Phase I PACU. Once in Phase II PACU, patients were similarly assessed by the same personnel at 15-min intervals to determine whether they met discharge criteria. There was no minimal time requirement for patients to remain in the Phase II PACU. Rather, for home readiness, patients were required to meet a score of >9 on the postanesthesia discharge scoring system.
Home readiness and the decision to discharge were made by the Phase II PACU nursing personnel, who were unaware of the purpose of the study. Voiding was not required before discharge (6).
If patients complained of postoperative pain, medications were offered according to the following protocol. In Phase I PACU, morphine sulfate (1–2 mg) was administered by IV injection every 5–10 min until the patient was comfortable (VAS score 
2). The pain management protocol in Phase II PACU and at home consisted of acetaminophen (325 mg) with codeine (30 mg) every 4 h as needed. Patients who had severe nausea (VAS >5) or vomiting were given IV ondansetron 8 mg.
The quantity of analgesics used during the pre-, intra-, and postoperative phases was noted. Adverse events such as nausea, vomiting, hypotension (mean arterial blood pressure <30% of preoperative), bradycardia (heart rate <60 bpm), respiratory depression (respiratory rate <10 breaths/min), hypoxia (O2 saturation <90), apnea, or dizziness were noted. Relevant time intervals, such as OR time, recovery time, and time-to-discharge-home were recorded using data from the automated record-keeping system (7). Data also were collected on the number of patients eligible to bypass Phase I PACU. Pain scores were determined using a VAS on arrival to Phase I PACU and at the time of discharge. Before discharge, patients also were asked to subjectively rate their energy levels (as self-reported on a VAS). After discharge home, a research assistant, blinded to the type of anesthetic used, collected data, via telephone interviews with the patients, on highest pain VAS scores and daily requirement for pain tablets at 24, 48, and 72 h after surgery. Data on any complications (prolonged numbness, radiating pain in the distribution of the lumbar or sciatic plexuses, motor weakness), satisfaction with anesthesia, and willingness to have the same anesthesia for their consecutive surgeries were collected 2 wk after surgery.
Sample size estimates were based on time to home readiness and discharge (in minutes), because these variables were of primary interest for this study. It was estimated that a sample size of 18 per group would provide 80% power to detect a clinically meaningful difference of 90 min (within-group standard deviation, 60 min) at 
= 0.001. The probability of a type-I error was set low to accommodate the multiple comparisons that were planned, particularly for the targeted time measures (e.g., time to ambulation, time to fluid and solid intake). Furthermore, sample size was increased to 25 per group, as an additional assurance that would not be inflated when demographic and postoperative data were analyzed.
Discrete categoric data are presented as n (%); continuous data as mean ± sd. Differences in demographic, surgical, anesthetic, and postoperative data were tested by independent Student’s t-test (continuous data) or by 
2 (categoric data) and Fisher’s exact test (when appropriate). For descriptive purposes, P value differences <0.05 are noted in the Tables. All analyses were conducted using the Statistical Package for the Social Sciences (SPSS for Windows, version 11.0.1, 2001; SPSS, Chicago, IL).
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Results |
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Total OR time did not differ significantly between the 2 groups, although mean anesthetic induction time was longer (7 min) in patients given PNBs as compared with those given GA (Table 1). Patients undergoing PNB received 4.5 ± 1.5 mg of midazolam and 510 ± 240 µg of alfentanil for block induction, followed by a median dose of 189 mg (range, 0–706 mg) of propofol during surgery, whereas the patients undergoing GA received 2.5 ± 1.2 mg of midazolam and 140 ± 82 µg of fentanyl intraoperatively.
Seventy-two percent of patients receiving PNB met criteria enabling them to bypass Phase I PACU compared with only 24% of those receiving GA (P < 0.002). It should be noted that none of the PNBs patients met the modified Aldrete score of 10 because of the residual lower extremity blockade. Mean stay in the Phase I PACU for those who required admission was 107 ± 37 min. Mean Phase I PACU stay among these patients did not differ by type of anesthesia administered (105 ± 40 versus 115 ± 27 min for PNB and GA). Time to meet criteria for discharge home (home readiness) and time to actual discharge were significantly shorter for patients given PNBs than for patients given GA (Table 2). As expected, time to meet criteria for home readiness was significantly shorter for patients who bypassed the Phase I PACU than for those who were admitted (138 ± 80 versus 195 ± 86 min, P = 0.02); subsequently, their time to actual discharge from the hospital was also significantly shorter (168 ± 84 versus 218 ± 89 min, P < 0.05). Home readiness was significantly longer for patients who required pain medication in the Phase I PACU than for those who did not (226 versus 149 min, P = 0.006).
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Four patients (16%) given PNB required pain medication upon arrival to the Phase I PACU, whereas 8 (32%) given GA required pain medication. Nausea ratings in the Phase I PACU, at discharge, and at home, were individually categorized as 0 (no nausea), 1–2 (mild), 3–5 (moderate), or 5+ (severe), and were summed into a single nausea score. Information on nausea at discharge was available for 48 patients (96%). Among these, 36 (75%) indicated that they had at least 1 episode of nausea at discharge. The occurrence of nausea was significantly associated with the type of anesthesia (Fisher exact P value = 0.03). Eleven patients with nausea (31%) had been given medication for pain in the Phase I PACU. The majority of patients given PNB (88%) reported no nausea or mild nausea (Table 2).
After discharge home, most patients (70%) reported having moderate pain at 24 h postoperatively and required 3–7 pain tablets in the first 24 h.
There was no significant difference in severity of the postoperative pain, consumption of oral analgesics, or satisfaction with anesthesia technique.
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Discussion |
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It has been suggested that PNBs provide effective anesthesia and excellent postoperative analgesia but require more preoperative time. Some commonly voiced disadvantages of PNBs include the additional time required to perform the blocks and the potential that, although patients receiving blocks may have superior pain relief in the immediate postoperative period, they may ultimately have more pain when the blocks wear off. Neither of these assertions proved true in the current study. Although some additional time was required to perform PNBs as compared with induction of GA and securing the airway, total OR time was similar, even though the blocks were performed in the OR. This undoubtedly is attributable to the combination of our staff’s experience in using PNBs for knee arthroscopy, a fast-acting local anesthetic, and the fact that surgeons could proceed with surgical preparation without having to wait to document the onset of full surgical anesthesia. Conceivably, inducing blocks preoperatively in the holding area rather than in the OR would further decrease OR time, although this may not be feasible when chloroprocaine is used as the local anesthetic because of its short duration of action. In addition, time from the end of surgical dressing until exit from the OR (emergence time) is likely faster after PNB, which would effectively offset the additional induction time needed to place the block in the OR.
Our study agrees with the only two other prospective, randomized studies comparing PNBs with GA for outpatient knee arthroscopy. Patel et al. (10) found that PNBs were preferable to GA and resulted in faster home-discharge. Unfortunately, that study did not specify information about the GA technique used. Additionally, since the study’s publication in 1985, there have been numerous improvements to GA techniques and introduction of the LMA, which have led to inhaled anesthetics with more favorable recovery profiles. Jankowski et al. (4), in a more-recent study, found that the use of a psoas compartment blockade decreased overall resource use (by avoiding PACU admission) and resulted in better patient satisfaction than GA did. In their study, there was no significant difference in time-to-home discharge among PNB, spinal, and GA. However, it is possible that this lack of significance was because these authors used a longer-acting local anesthetic (mepivacaine) than in our study (chloroprocaine), which precluded patients from ambulating until the PNB wore off. In addition, voiding was required in all patients in this study. Regardless, more recent data suggest that short-acting spinal anesthetics (such as chloroprocaine) might be a good choice in outpatient surgery (11).
Similarly to the finding in a study by McCartney et al. (12), the analgesic benefits of PNBs in our study were limited to the immediate postoperative period. Although the choice to use a longer-acting local anesthetic in PNBs would have undoubtedly resulted in a longer duration of analgesia, we believed that the relatively minor degree of surgical trauma did not warrant the use of a long-acting local anesthetic and the consequent prolonged motor blockade of the lumbar plexus. In addition, in this study, a true multimodal approach to postoperative pain management was not used. A coadministration of oral opioids, nonsteroidal antiinflammatory drugs, and cyclooxygenase inhibitors, may have influenced the results (13). However, any beneficial effects of such therapy likely would have been conferred to both groups. Finally, it is likely that the patients in the PNB group would also have received additional analgesic benefit if they were also given the intraarticular injection of local anesthetic the GA patients received.
It could be argued that a different choice of GA (e.g., total IV anesthesia) and awareness monitoring might have favorably influenced the recovery profile after GA (14,15). For instance, Ben-David et al. (16) demonstrated that both local anesthesia supplemented by a titrated IV propofol infusion and minidose lidocaine-fentanyl spinal anesthesia for outpatient knee arthroscopy provide high patient satisfaction with equally rapid recovery and discharge. However, the duration of surgery in the study by Ben-David et al. was significantly shorter than in our study (approximately 24 versus 65 minutes, respectively). This may be because our inclusion criteria (surgeries >45 minutes in duration) excluded minor interventions and short diagnostic knee arthroscopy. For that reason, their findings may not be applicable to the conditions of our study. The GA protocol used in this study in conjunction with the LMA is often accepted as a conventional model for GA in patients undergoing ambulatory surgery. For instance, a systematic analysis of the literature comparing postoperative recovery after propofol, isoflurane, desflurane, and sevoflurane-based anesthesia in adults demonstrated that early recovery was faster in the desflurane and sevoflurane groups (17). However, the incidence of nausea and vomiting were less frequent with propofol (17). Additionally, our data may not be reproducible in institutions without expertise in PNBs comparable to that of our faculty. Indeed, the training and practice of PNBs significantly varies from institution to institution and in-depth training is a prerequisite for both the success and safety of PNBs (18).
Despite significant pharmacologic advances over the past decade, nausea and vomiting remain some of the most common and unpleasant experiences associated with GA in ambulatory surgery. In our study, patients having PNBs had significantly less frequent nausea and vomiting than did patients having GA (12% versus 62%), despite prophylactic administration of dolasetron in the GA group (19). It is possible, however, that administration of dolasetron as a sole prophylactic antiemetic was inadequate to prevent nausea and vomiting in the group having GA. For instance, Tang et al. (20) showed that triple antiemetic prophylaxis in patients having desflurane GA was effective in producing an equivalent uncomplicated discharge compared with a propofol GA. In addition, despite the use of a LMA, as many as 60% of the patients who received GA developed sore throat.
In summary, PNBs may offer advantages over GA in outpatients having knee arthroscopy. Under the conditions of our study, patients who received PNBs had less postoperative pain and nausea in the immediate postoperative period and were able to ambulate, eat, drink, and meet home readiness criteria earlier than patients who received GA.
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Footnotes |
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Accepted for publication November 1, 2004.
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