Br. J. Anaesth. (2011) 107 (2): 123-126.

In 1996, we published an editorial ‘Ketamine, mechanism(s) of action and unusual clinical uses’ in the British Journal of Anaesthesia. In that editorial, we described the pharmacology of ketamine including bronchodilator, anti-shock, and neuroprotective actions along with some unusual clinical applications. The editorial has been cited more than 130 times in total with around 10 citations every year, which implies that ketamine is still of interest to a wide audience. However, as ketamine anaesthesia is associated with cardiovascular hyperdynamics and disturbing emergence reactions, this agent is often avoided, despite the ease with which these adverse reactions can be prevented by pre-administration, co-administration of sedatives, or both such as benzodiazepines, propofol, dexmedetomidine, or droperidol.
In the past 15 yr, ketamine has been reported to possess several new clinically beneficial properties such as potentiation of opioid analgesia, prevention of opioid-induced acute tolerance and spinal ischaemia, anti-inflammatory actions, preventive effects on recall and awareness during general anaesthesia, and anti-tumour actions. In this ‘update’ editorial, we have focused on these potential clinical advantages of ketamine.

Anesth Analg 2002;95:1788-1792

Perturbation of respiratory mechanics produced by general anesthesia and surgery is more pronounced in morbidly obese (MO) patients. Because general anesthesia induces pulmonary atelectasis in nonobese patients, we hypothesized that atelectasis formation would be particularly significant in MO patients. We investigated the importance and resorption of atelectasis after general anesthesia in MO and nonobese patients. Twenty MO patients were anesthetized for laparoscopic gastroplasty and 10 nonobese patients for laparoscopic cholecystectomy. We assessed pulmonary atelectasis by computed tomography at three different periods: before the induction of general anesthesia, immediately after tracheal extubation, and 24 h later. Already before the induction of anesthesia, MO patients had more atelectasis, expressed in the percentage of the total lung area, than nonobese patients (2.1% versus 1.0%, respectively; P < 0.01). After tracheal extubation, atelectasis had increased in both groups but remained significantly more so in the MO group (7.6% for MO patients versus 2.8% for the nonobese; P < 0.05). Twenty-four hours later, the amount of atelectasis remained unchanged in the MO patients, but we observed a complete resorption in nonobese patients (9.7% versus 1.9%, respectively; P < 0.01). General anesthesia in MO patients generated much more atelectasis than in nonobese patients. Moreover, atelectasis remained unchanged for at least 24 h in MO patients, whereas atelectasis disappeared in the nonobese.

Implications
We compared the resolution over time of pulmonary atelectasis after a laparoscopic procedure by performing computed tomography scans in two different groups of patients: 1 group had 10 nonobese patients, and in the other group there were 20 morbidly obese patients.

Carotid endarterectomy surgery can be performed under regional anaesthesia alone or under general anaesthesia. However, there are several types of regional block available and reported complication rates after superficial cervical plexus blocks are significantly lower than deep blocks. It is not known if subcutaneous and intermediate blocks are equally effective, although anatomical evidence suggests that the latter (where the injectate diffuses below the deep cervical fascia) might provide superior quality of intraoperative anaesthesia.

Methods
Forty-four patients were randomized to receive either subcutaneous or intermediate cervical plexus blocks for carotid endarterectomy. The primary endpoint was supplemental lidocaine requirement during surgery. Secondary outcome measures included: total amount of fentanyl administered during surgery, recall of pain scores during surgery, complications, and patient and surgeon satisfaction.

Results
There was no statistically significant difference for median (range) lidocaine supplementation between the subcutaneous and intermediate groups 65 (20–170) mg vs 85 (30–345) mg, respectively; P=0.31. There were no statistical differences in the secondary outcome measures and no major complications during the study.

Conclusions
Intermediate and subcutaneous cervical plexus blocks are equally effective for carotid endarterectomy. This study adds to the body of evidence supporting the safe use of superficial blocks for this type of surgery.

Br. J. Anaesth 2011;107:164-170

There is some evidence that epidural analgesia (EDA) reduces tumour recurrence after breast and prostatic cancer surgery. We assessed whether EDA reduces long-term mortality after colorectal cancer surgery.

Methods
All patients having colorectal cancer surgery between January 2004 and January 2008 at Linköping and Örebro were included. Exclusion criteria were: emergency operations, laparoscopic-assisted colorectal resection, and stage 4 cancer. Statistical information was obtained from the Swedish National Register for Deaths. Patients were analysed in two groups: EDA group or patient-controlled analgesia (PCA group) as the primary method of analgesia.

Results
A total of 655 patients could be included. All-cause mortality for colorectal cancer (stages 1–3) was 22.7% (colon: 20%, rectal: 26%) after 1–5 yr of surgery. Multivariate regression analysis identified the following statistically significant factors for death after colon cancer (P<0.05): age (>72 yr) and cancer stage 3 (compared with stage 1). A similar model for rectal cancer found that age (>72 yr) and the use of PCA rather than EDA and cancer stages 2 and 3 (compared with stage 1) were associated with a higher risk for death. No significant risk of death was found for colon cancer when comparing EDA with PCA (P=0.23), but a significantly increased risk of death was seen after rectal cancer when PCA was used compared with EDA (P=0.049) [hazards ratio: 0.52 (0.27–1.00)].

Conclusions
We found a reduction in all-cause mortality after rectal but not colon cancer in patients having EDA compared with PCA technique.

Anesth Analg January 2005 100:59-65;

One of the most controversial issues in pediatric anesthesia has revolved around the decision to proceed with anesthesia and surgery for the child who presents with an upper respiratory tract infection (URI). In the past, doctrine dictated that children with URIs have their surgery postponed until the child was symptom free. This practice was based on the empirically supported premise that anesthesia increased the risk of serious complications and complicated the child’s postoperative course. Although recent clinical data confirm that some children with URIs are at increased risk of perioperative complications, these complications can, for the most part, be anticipated, recognized, and treated. Although the child with a URI still presents a challenge, anesthesiologists are now in a better position to make informed decisions regarding the assessment and management of these children, such that blanket cancellation has now become a thing of the past.

Anesth Analg 2009;109:607-615

Apart from being antiemetic, glucocorticoids have an analgesic property. The optimal dose of dexamethasone in the management of pain after surgery has not been established. In this placebo-controlled, dose-finding study, we evaluated the analgesic effect of three doses of dexamethasone after laparoscopic hysterectomy.

Methods
We randomized 129 women scheduled for laparoscopic hysterectomy to receive placebo, dexamethasone 5 mg (D5), 10 mg (D10), or 15 mg (D15) IV before the induction of anesthesia. The patients were anesthetized with propofol and remifentanil in a standardized manner. Until the first postoperative morning, postoperative pain was managed with IV oxycodone using patient-controlled analgesia. The visual analog scale scores for pain and side effects, and the amounts of the analgesics were recorded for 3 days after surgery.

Results
The total dose of oxycodone (0–24 h after surgery) was smaller in the D15 (0.34 mg/kg [0.11–0.87]) group than in the placebo group (0.55 mg/kg [0.19–1.13]) (P = 0.003). The doses of oxycodone during Hours 0–2 after surgery were smaller in the D10 (0.17 mg/kg [0.03–0.36]) and D15 (0.17 mg/kg [0.03–0.35]) groups than in the placebo (0.26 mg/kg [0.10–0.48]) (P = 0.001, D10 versus placebo; P < 0.001, D15 versus placebo) group. During Hours 2–24 after surgery, however, the doses of oxycodone were equal in the placebo, D5, D10, and D15 groups (0.31 mg/kg [0.03–0.78], 0.22 mg/kg [0.03–0.92], 0.24 mg/kg [0.05–0.87], and 0.20 mg/kg [0–0.65], respectively). The visual analog scale scores for pain at rest, in motion, or at cough did not differ in the study groups. The incidence of dizziness was lower in the D15 group than in the placebo group (P = 0.001), the D5 group (P = 0.006), and the D10 group (P = 0.030) during the first 24 h after surgery. During the later course of recovery, the incidence of dizziness did not differ among the four study groups.

Conclusions
IV dexamethasone 15 mg before induction of anesthesia decreases the oxycodone consumption during the first 24 h after laparoscopic hysterectomy. During first 2 h after surgery, dexamethasone 10 mg reduces the oxycodone consumption as effectively as the 15 mg dose.

Anesth Analg 2009;109:114-118

Pulse wave analysis (PWA) allows cardiac output (CO) measurement after calibration by transpulmonary thermodilution. A PWA system that does not require previous calibration, the FloTrac/Vigileo (FTV), has been recently developed. We compared determinations of CO made with the FTV to simultaneous measurements using transesophageal echocardiography (TEE).

Methods
Ten ASA I-II patients scheduled for laparoscopic colorectal surgery were studied. A radial 20-gauge cannula was inserted and connected to a hemodynamic monitor and a FTV system for PWA and determination of CO (COPWA). TEE CO (COTEE) was determined as previously described. Measurements were made after intubation, 5 min after establishing the lithotomy position, 5 min after establishing pneumoperitoneum, every 30 min, or each time mean arterial blood pressure decreased below basal values. Statistical analysis was made with the Bland and Altman method.

Results
Eighty-eight measurements were compared. The COTEE values ranged from 3.23 to 12 Lt/min (mean 6.21 ± 1.85). Values for COPWA ranged from 2.9 to 8.5 Lt/min (mean 4.84 ± 1.14). Bias was 1.17 and limits of agreement −2.02 and 4.37. The percentage error between all COTEE and COPWA measurements was 40% (27%-50%) mean (range).

Conclusions
During laparoscopic colon surgery, clinically important differences were observed between CO determinations made with TEE and FTV.

Anesth Analg 2004;98:1044-1049

In this study, we evaluated the preemptive effect of a small dose of ketamine on postoperative wound pain. In a randomized, double-blinded, controlled trial, we compared the analgesic requirement in patients receiving preincision ketamine with ketamine after skin closure or placebo after gynecologic laparoscopic surgery. One-hundred-thirty-five patients were randomly assigned to receive preincision or postoperative ketamine 0.15 mg/kg or saline IV. Anesthetic technique was standardized. Patients were interviewed regularly up to 4 wk after surgery. Pain score, morphine consumption, side effects, and quality of recovery score were recorded. Patients receiving preincision ketamine had a lower pain score in the first 6 h after operation compared with the postoperative (P = 0.001) or placebo groups (P < 0.001). The mean (95% confidence intervals) time to first request for analgesia in the preincision group, 1.8 h (1.4–2.1), was longer than the postoperative group, 1.2 h (0.9–1.5; P < 0.001), or the placebo group, 0.7 h (0.4–0.9; P < 0.001). The mean ± sd morphine consumption in the preincision group, 1.5 ± 2.0 mg, was less than that in the postoperative group, 2.9 ± 3.1 mg (P = 0.04) and the placebo group, 3.4 ± 2.7 mg (P = 0.003). There was no significant difference among groups with respect to hemodynamic variables or side effects. No patient complained of hallucinations or nightmares. We conclude that a small dose of ketamine is not only safe, but it also provides preemptive analgesia in patients undergoing gynecologic laparoscopic surgery.

Implications
In women undergoing laparoscopic gynecologic surgery, a small preoperative dose of ketamine (0.15 mg/kg) produced preemptive analgesia. There were no significant hemodynamic and psychological side effects with this dose.

Anesth Analg 2000;91:403-407 

We tested the hypothesis that local anesthetics instilled at the end of laparoscopic gynecologic procedures are able to prevent postoperative pain at wake-up and during the first 24 h. A total of 180 patients were randomly assigned into three groups to receive an intraperitoneal instillation of 20 mL of either bupivacaine 0.5% (Group B), ropivacaine 0.75% (Group R) or saline (Group S) at the end of surgery. All patients received analgesia with acetaminophen and ketoprofen IV infusions. Pain was assessed by using a 0–10 graded numerical scale (NS) every 5 min in the postanesthesia care unit and IV morphine was administered if NS was >4. Assessment of pain was continued every 4 h on the ward, and subcutaneous morphine was injected if needed to keep the NS score < 4. Postoperative nausea and vomiting (PONV) was rated on a 4-point scale. The morphine consumption at wake-up and over the first 24 h was significantly lower (P < 0.05) in Group B (mean, 0.92 mg at wake-up; 3.08 mg over 24 h) and in Group R (mean, 0.25 mg at wake-up; 0.69 mg over 24 h), than in Group S (mean, 4.18 mg at wake-up; 12.93 mg over 24 h). The morphine-sparing effect of ropivacaine was significantly greater than that of bupivacaine. Both local anesthetics were effective in the prevention of PONV. We concluded that local anesthetics should be instilled in all gynecologic patients at the end of all laparoscopic procedures.

Implications
Local anesthetic instillation (ropivacaine rather than bupivacaine) at the end of laparoscopy prevents postoperative pain and dramatically decreases the need for morphine. This technique, compared with placebo, is safe, improves patient comfort, shortens the stay in the postoperative care unit and decreases nursing care in the ward.

Anesth  Analg 2011;113:1218-1225

Postoperative pain can delay functional recovery after outpatient surgery. Multimodal analgesia can improve pain and possibly improve quality of recovery. In this study, we evaluated the dose-dependent effects of a preoperative transversus abdominis plane (TAP) block on patient recovery using the Quality of Recovery 40 (QoR-40) questionnaire after ambulatory gynecological laparoscopic surgery. Global QoR-40 scores range from 40 to 200, representing very poor to outstanding quality of recovery, respectively.

Methods
Healthy women undergoing outpatient gynecological laparoscopy were randomly allocated to receive a preoperative TAP block using saline, ropivacaine 0.25%, or ropivacaine 0.5%. Needle placement for the TAP blocks was performed using ultrasound guidance and 15 mL of the study solution was injected bilaterally by a blinded investigator. QoR-40 score and analgesic use were assessed 24 hours postoperatively. The primary outcome was global QoR-40 score at 24 hours after surgery. Data were analyzed using the Kruskal-Wallis test. Post hoc pairwise comparisons were made using the Dunn test with P values and 95% confidence intervals Bonferroni corrected for 6 comparisons.

Results
Seventy-five subjects were enrolled and 70 subjects completed the study. The median (range) for the QoR-40 score after the TAP block was 157 (127–193), 173 (133–195), and 172 (130–196) for the saline group and 0.25% and 0.5% ropivacaine groups, respectively. The median difference (99.2% confidence interval) in QoR-40 score for 0.5% bupivacaine (16 [1–30], P = 0.03) and 0.25% bupivacaine (17 [2–31], P = 0.01) was more than saline but not significantly different between ropivacaine groups (−1 [−16 to 12], P = 1.0). Increased global QoR-40 scores correlated with decreased area under the pain score time curve during postanesthesia recovery room stay (ρ = −0.56, 99.2% upper confidence limit [UCL] = −0.28), 24-hour opioid consumption (ρ = −0.61, 99.2% UCL = −0.34), pain score (0–10 scale) at 24 hours (ρ = −0.53, 99.2% UCL = −0.25), and time to discharge readiness (ρ = −0.65, 99.2% UCL = −0.42). The aforementioned variables were lower in the TAP block groups receiving ropivacaine compared with saline.

Conclusions
The TAP block is an effective adjunct in a multimodal analgesic strategy for ambulatory laparoscopic procedures. TAP blocks with ropivacaine 0.25% and 0.5% reduced pain, decreased opioid consumption, and provided earlier discharge readiness that was associated with better quality of recovery.

Anesth  Analg 2011;113:1266-1271

Studies evaluating intraperitoneal local anesthetic instillation for pain relief after laparoscopic procedures have reported conflicting results. In this randomized, double-blind study we assessed the effects of intraperitoneal local anesthetic nebulization on pain relief after laparoscopic cholecystectomy.

Methods
Patients undergoing elective laparoscopic cholecystectomy were randomly assigned to receive either instillation of ropivacaine 0.5%, 20 mL after induction of the pneumoperitoneum, or nebulization of ropivacaine 1%, 3 mL before and after surgery. Anesthetic and surgical techniques were standardized. Degree of pain at rest and on deep breathing, incidence of shoulder pain, morphine consumption, unassisted walking time, and postoperative nausea and vomiting were evaluated at 6, 24, and 48 hours after surgery.

Results
Of the 60 patients included, 3 exclusions occurred for conversion to open surgery. There were no differences between groups in pain scores or in morphine consumption. No patients in the nebulization group presented significant shoulder pain in comparison with with 83% of patients in the instillation group (absolute risk reduction −83, 95% CI −97 to −70, P < 0.001). Nineteen (70%) patients receiving nebulization walked without assistance within 12 hours after surgery in comparison with 14 (47%) patients receiving instillation (absolute risk reduction −24, 95% CI −48 to 1, P = 0.04). One (3%) patient in the instillation group vomited in comparison with 6 (22%) patients in the nebulization group (absolute risk reduction −19%, 95% CI −36 to −2, P = 0.03).

Conclusions
Intraperitoneal ropivacaine nebulization was associated with reduced shoulder pain and unassisted walking time but with an increased incidence of postoperative vomiting after laparoscopic cholecystectomy.

 Anesth Analg 2005;100:340-347

Conflicting results have been published about the effects of carbon dioxide (CO2) pneumoperitoneum on splanchnic and liver perfusion. Several experimental studies described a pressure-related reduction in hepatic blood flow, whereas other investigators reported an increase as long as the intraabdominal pressure (IAP) remained less than 16 mm Hg. Our goal in the present study was to investigate the effects of insufflated CO2 on hepatic blood flow during laparoscopic surgery in healthy adults. Blood flow in the right and middle hepatic veins was assessed in 24 patients undergoing laparoscopic surgery by use of transesophageal Doppler echocardiography. Hepatic venous blood flow was recorded before and after 5, 10, 20, 30, and 40 min of pneumoperitoneum, as well as 1 and 5 min after deflation. Twelve patients undergoing conventional hernia repair served as the control group. The induction of pneumoperitoneum produced a significant increase in blood flow of the right and middle hepatic veins. Five minutes after insufflation of CO2 the median right hepatic blood flow index increased from 196 mL/min/m2 (95% confidence interval (CI), 140–261 mL/min/m2) to 392 mL/min/m2 (CI, 263–551 mL/min/m2) (P < 0.05) and persisted during maintenance of pneumoperitoneum. In the middle hepatic vein the blood flow index increased from 105 mL/min/m2 (CI, 71–136 mL/min/m2) to 159 mL/min/m2 (CI, 103–236 mL/min/m2) 20 min after insufflation of CO2. After deflation blood flow returned to baseline values in both hepatic veins. Conversely, in the control group hepatic blood flow remained unchanged over the entire study period. We conclude that induction of CO2 pneumoperitoneum with an IAP of 12 mm Hg is associated with an increase in hepatic perfusion in healthy adults.

Implications
Blood flow in the right and middle hepatic veins was studied by use of transesophageal echocardiography in 24 patients undergoing laparoscopic surgery. CO2 pneumoperitoneum induced a significant increase in hepatic venous blood flow. This finding is in contrast to results of experimental studies suggesting that CO2 pneumoperitoneum may be harmful to liver function as a result of impaired perfusion.

Anesth Analg 2006;103:856-858

Laparoscopic surgery represents a significant advance in surgical technique, but a number of physiologic sequelae result from positioning and insufflation. These physiologic changes may be more significant in patients with complex congenital heart disease. We present the anesthetic management of a patient with Fontan physiology who successfully underwent two separate laparoscopic procedures.

Anesth Analg September 2008 107:818-823

Whether nitrous oxide (N2O) increases the incidence of postoperative nausea and vomiting (PONV) after laparoscopic gynecologic surgery is still controversial, which may be due to the administration of different concentrations of inspired N2O. We investigated whether N2O results in a dose–response increase in PONV.

Methods
Patients undergoing gynecologic laparoscopic surgery were randomized to receive 30% oxygen with air (G0, n = 46), 50% N2O with oxygen (G50, n = 46), or 70% N2O with oxygen (G70, n = 45). A standardized general anesthetic was used with no PONV prophylaxis. Known risk factors for PONV were controlled. Metoclopramide was used as a rescue antiemetic. The incidence of nausea, vomiting, use of rescue antiemetic, and pain visual analog scale (VAS) score was measured at 2 and 24 h postoperatively.

Results
Patient demographics were comparable, and there were no differences among groups regarding factors that may influence PONV. The incidence of PONV at 24 h was 33% (15 of 46) in the G0 group, 46% (21 of 46) in the G50 group, and 62% (28 of 45) in the G70 group (P = 0.018). Subgroup analysis revealed a difference between G0 versus G70 groups (P = 0.018), but no significant difference between G0 versus G50 groups and G50 versus G70 groups. The incidence of nausea showed a similar difference (G0 = 26%, G50 = 35%, and G70 = 56%; P = 0.012), but the incidence of vomiting was not different among the groups although there was a trend (G0 = 28%, G50 = 35%, and G70 = 42%; P = 0.377). The severity of nausea (measured by VAS 100 mm) was significantly increased with increasing N2O concentration (G0 = 10.9, G50 = 12.7, and G70 = 20.5; P = 0.027). The highest VAS score during 24 h was used for the analysis. There was no difference in the use of a rescue antiemetic among groups. Pain VAS scores and opioids consumption were not different among groups (at 2 and 24 h after surgery).

Conclusions
N2O increases the incidence of postoperative nausea after gynecologic laparoscopic surgery. This preliminary finding indicates that N2O may increase PONV in a dose-dependent fashion. A study with a sample size of >400 patients in each group would be necessary to demonstrate a statistically significant difference among each of these three groups. We do not recommend using a high concentration of N2O in this clinical setting.

Implications
We demonstrate that nitrous oxide (N2O) increases the incidence of postoperative nausea and vomiting (PONV) after laparoscopic gynecologic surgery. The preliminary findings indicate that N2O may increase PONV in a dose-dependent fashion. A high concentration of N2O in this clinical setting is not recommended.

Anesth Analg 2011;113:784-790

Bilateral total knee arthroplasty (BTKA) performed during the same hospitalization carries increased risk for morbidity and mortality compared with the unilateral approach. However, no evidence-based stratifications to identify patients at risk for major morbidity and mortality are available. Our objective was to determine the incidence and patient-related risk factors for major morbidity and mortality among patients undergoing BTKA.

Methods
Nationwide Inpatient Survey data collected for the years 1998 to 2007 were analyzed and cases of elective BTKA procedures were included. Patient demographics, including comorbidities, were analyzed and frequencies of mortality and major complications were computed. Subsequently, a multivariate analysis was conducted to determine independent risk factors for major morbidity and mortality.

Results
Included were 42,003 database entries, representing an estimated 206,573 elective BTKAs. The incidence of major in-hospital complications and mortality was 9.5%. Risk factors for adverse outcome included advanced age (odds ratios [ORs] for age groups 65–74 and >75 years were 1.88 [confidence interval, CI: 1.72, 2.05] and 2.66 [CI: 2.42, 2.92], respectively, compared with the 45–65 years group), male gender (OR: 1.54 [CI: 1.44, 1.66]), and a number of comorbidities. The presence of congestive heart failure (OR: 5.55 [CI: 4.81, 6.39]) and pulmonary hypertension (OR: 4.10 [CI: 2.72, 6.10]) were the most significant risk factors associated with increased odds for adverse outcome.

Conclusions
We identified patient-related risk factors for major morbidity and mortality in patients undergoing BTKA. Our data can be used to aid in the selection of patients for this procedure.

Anesth Analg 2011;113:926-933

Local infiltration analgesia (LIA)—using a combination of local anesthetics, nonsteroidal anti-inflammatory drugs, and epinephrine, injected periarticularly during surgery—has become popular in postoperative pain management after total knee arthroplasty (TKA). We compared intrathecal morphine with LIA after TKA.

Methods
In this double-blind study, 50 patients scheduled to undergo TKA under spinal anesthesia were randomized into 2 groups: group M, 0.1 mg morphine was injected intrathecally together with the spinal anesthetic and in group L, LIA using ropivacaine, ketorolac, and epinephrine was infiltrated in the knee during the operation, and 2 bolus injections of the same mixture were given via an intraarticular catheter postoperatively. Postoperative pain, rescue analgesic requirements, mobilization, and home readiness were recorded. Patient-assessed health quality was recorded using the Oxford Knee Score and EQ-5D during 3 months follow-up. The primary endpoint was IV morphine consumption the first 48 postoperative hours.

Results
Mean morphine consumption was significantly lower in group L than in group M during the first 48 postoperative hours: 26 ± 15 vs 54 ± 29 mg, i.e., a mean difference for each 24-hour period of 14.2 (95% confidence interval [CI] 7.6 to 20.9) mg. Pain scores at rest and on movement were lower during the first 48 hours in group L than in group M (P < 0.001). Pain score was also lower when walking in group L than in group M at 24 hours and 48 hours postoperatively (P < 0.001). In group L, more patients were able to climb stairs at 24 hours: 50% (11 of 22) versus 4% (1 of 23), i.e., a difference of 46% (95% CI 23.5 to 68.5) and at 48 hours: 70% (16 of 23) versus 22% (5 of 23), i.e., a difference of 48% (95% CI 23 to 73). Median (range) time to fulfillment of discharge criteria was shorter in group L than in group M, 51 (24–166) hours versus 72 (51–170) hours. The difference was 23 (95% CI 18 to 42) hours (P = 0.001). Length of hospital stay was also shorter in group L than in group M: median (range) 3 (2–17) versus 4 (2–14) days (P = 0.029). Patient satisfaction was greater in group L than in group M (P = 0.001), but no differences were found in knee function, side effects, or in patient-related outcomes, Oxford Knee score, or EQ-5D.

Conclusions
LIA technique provided better postoperative analgesia and earlier mobilization, resulting in shorter hospital stay, than did intrathecal morphine after TKA.

Anesth Analg 1998;86:598-612

We performed meta-analyses of randomized, control trials to assess the effects of seven analgesic therapies on postoperative pulmonary function after a variety of procedures: epidural opioid, epidural local anesthetic, epidural opioid with local anesthetic, thoracic versus lumbar epidural opioid, intercostal nerve block, wound infiltration with local anesthetic, and intrapleural local anesthetic. Measures of forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), vital capacity (VC), peak expiratory flow rate (PEFR), PaO2, and incidence of atelectasis, pulmonary infection, and pulmonary complications overall were analyzed. Compared with systemic opioids, epidural opioids decreased the incidence of atelectasis (risk ratio [RR] 0.53, 95% confidence interval [CI] 0.33-0.85) and had a weak tendency to reduce the incidence of pulmonary infections (RR 0.53, 95% CI 0.18-1.53) and pulmonary complications overall (RR 0.51, 95% CI 0.20-1.33). Epidural local anesthetics increased PaO2 (difference 4.56 mm Hg, 95% CI 0.058-9.075) and decreased the incidence of pulmonary infections (RR 0.36, 95% CI 0.21-0.65) and pulmonary complications overall (RR 0.58, 95% CI 0.42-0.80) compared with systemic opioids. Intercostal nerve blockade tends to improve pulmonary outcome measures (incidence of atelectasis: RR 0.65, 95% CI 0.27-1.57, incidence of pulmonary complications overall: RR 0.47, 95% CI 0.18-1.22), but these differences did not achieve statistical significance. There were no clinically or statistically significant differences in the surrogate measures of pulmonary function (FEV1, FVC, and PEFR). These analyses support the utility of epidural analgesia for reducing postoperative pulmonary morbidity but do not support the use of surrogate measures of pulmonary outcome as predictors or determinants of pulmonary morbidity in postoperative patients.

Implications
When individual trials are unable to produce significant results, it is often because of insufficient patient numbers. It may be impossible for a single institution to study enough patients. Meta-analysis is a useful tool for combining the data from multiple trials to increase the patient numbers. These meta-analyses confirm that postoperative epidural pain control can significantly decrease the incidence of pulmonary morbidity.

Anesth Analg 2011;112:387-393

There is a plausible pathophysiologic rationale for increased long-term cardiovascular morbidity and mortality in patients receiving significant exposure to nitrous oxide. However, this relationship has not been established clinically. The ENIGMA trial randomized 2050 patients having noncardiac surgery lasting more than 2 hours to nitrous oxide–based or nitrous oxide–free anesthesia. We conducted a follow-up study of the ENIGMA patients to evaluate the risk of cardiovascular events in the longer term.

Methods
The trial case report forms and medical records of all study patients were reviewed. The date and cause of death and occurrence of myocardial infarction or stroke were recorded. A telephone interview was then conducted with all surviving patients. The primary endpoint of the study was survival.

Results
The median follow-up time was 3.5 (range: 0 to 5.7) years. Three hundred eighty patients (19%) had died since the index surgery, 91 (4.5%) were recorded as having myocardial infarction, and 44 (2.2%) had a stroke during the entire follow-up period. Nitrous oxide did not significantly increase the risk of death [hazard ratio = 0.98 (95% confidence interval, CI: 0.80 to 1.20; P = 0.82)]. The adjusted odds ratio for myocardial infarction in patients administered nitrous oxide was 1.59 (95% CI: 1.01 to 2.51; P = 0.04) and for stroke was 1.01 (95% CI: 0.55 to 1.87; P = 0.97).

Conclusions
The administration of nitrous oxide was associated with increased long-term risk of myocardial infarction, but not of death or stroke in patients enrolled in the ENIGMA trial. The exact relationship between nitrous oxide administration and serious long-term adverse outcomes will require confirmation by an appropriately designed large randomized controlled trial.

Anaesthesia 2010;65:974–976

In January 2010, the Association of Anaesthetists of Great Britain and Ireland published its safety guideline Pre-operative Assessment and Patient Preparation – The Role of the Anaesthetist 2. The opening line of the section on tests and investigations states that ‘Routine pre-operative investigations are expensive, labour intensive and of questionable value, especially as they may contribute to morbidity or cause additional delays due to spurious results’. Citing Clinical Guidelines 3, published in 2004 by the National Institute for Clinical Excellence (NICE), the authors go on to recommend that routine tests should indeed be undertaken in a number of specific patient groups before most types of surgery, including many procedures that are typically performed on a day-case basis. In the prevailing economic climate, can continued expenditure on tests of questionable value be justified, and is there sufficient evidence to consider abandoning routine pre-operative testing altogether?

Anaesthesia 2011;66:243-246