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.

Intensive Care Med (2006) 32:1336–1343

Central venous oxygen saturation (ScvO2) in initial resuscitation is included in the Surviving Sepsis Campaign guidelines. ScvO2 monitoring has also been suggested to be comparable to mixed venous oxygen saturation (SvO2) for clinical purposes. The aim of our study was to assess the correlation and agreement of ScvO2 and SvO2 and compare ScvO2?SvO2 difference to lactate, oxygen-derived and hemodynamic parameters in early septic shock in ICU after initial resuscitation.

Design and setting
Prospective clinical study with 16 patients with septic shock at two university hospital ICUs. A dose of norepinephrine over 0.1ug/kg/min was required for inclusion.

Measurements and results
Five paired ScvO2 and SvO2 samples at 6-h intervals, altogether 72 samples, were collected during 24 h. The mean SvO2 was below the mean ScvO2 at all time points. Bias of difference was 4.2% and 95% limits of agreement ranged from 8.1% to 16.5%. The difference correlated significantly to CI and DO2.

Conclusion
The difference between paired ScvO2 and SvO2 varies highly. Therefore, SvO2 may not be estimated on the basis of ScvO2 in treatment of septic shock after resuscitation period in ICU.

Cardiovascular risk prediction using clinical risk factors is integral to both the European and the American algorithms for preoperative cardiac risk assessment and perioperative management for non-cardiac surgery. We have reviewed these risk factors and their ability to guide clinical decision making. We examine their limitations and attempt to identify factors which may improve their performance when used for clinical risk stratification. To improve the performance of the clinical risk factors, it is necessary to create uniformity in the definitions of both cardiovascular outcomes and the clinical risk factors. The risk factors selected should reflect the degree of organ dysfunction rather than a historical diagnosis. Parsimonious model design should be applied, making use of a minimal number of continuous variables rather than creating overfitted models. The inclusion of age in the model may assist partly in controlling for the duration of risk factor exposure. Risk assignment should occur throughout the perioperative period and the risk factors chosen for model inclusion should vary depending on when the assignment occurs (before operation, intraoperatively, or after operation).

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.

Br. J. Anaesth. 2011;107:180-185

In order to improve the consistency of anaesthetic risk scoring, we have developed an automated method for the calculation of ASA (cASA) scores using decision logic programming. We investigated whether ASA scoring by anaesthetic caregivers could be matched or closely approximated by a cASA.

Methods
We used a web-based preoperative assessment system to present a structured questionnaire comprising 22 questions. These were designed to score and identify conditions that are known, from the literature and expert opinion, to be risk factors. The answers from 14 349 cases were processed using decision logic to provide a variety of risk scores including a computed overall anaesthetic risk (cASA), which was then compared with the ASA score estimated by anaesthesia caregivers (eASA).

Results
We found a close agreement between the two measures in almost all cases. In 159 cases (1.1%), there was an underestimation of cASA, in comparison with the eASA, which appeared to be a result predominantly of incorrect or incomplete answers, or an overestimation of the ASA score by the human classifier (43%).

Conclusion
We showed that ASA scores estimated by a heterogeneous group of anaesthesia caregivers (anaesthetists, anaesthesia trainees, and physician assistants) could be mimicked by the cASA computed by our preoperative assessment system.

Critical Care 2010;14:325

The electronic version of this article is the complete one and can be found online at: http://ccforum.com/content/14/5/325
The present review of fluid therapy studies using balanced solutions versus isotonic saline fluids (both crystalloids and colloids) aims to address recent controversy in this topic. The change to the acid-base equilibrium based on fluid selection is described. Key terms such as dilutional-hyperchloraemic acidosis (correctly used instead of dilutional acidosis or hyperchloraemic metabolic acidosis to account for both the Henderson-Hasselbalch and Stewart equations), isotonic saline and balanced solutions are defined. The review concludes that dilutional-hyperchloraemic acidosis is a side effect, mainly observed after the administration of large volumes of isotonic saline as a crystalloid. Its effect is moderate and relatively transient, and is minimised by limiting crystalloid administration through the use of colloids (in any carrier). Convincing evidence for clinically relevant adverse effects of dilutional-hyperchloraemic acidosis on renal function, coagulation, blood loss, the need for transfusion, gastrointestinal function or mortality cannot be found. In view of the long-term use of isotonic saline either as a crystalloid or as a colloid carrier, the paucity of data documenting detrimental effects of dilutional-hyperchloraemic acidosis and the limited published information on the effects of balanced solutions on outcome, we cannot currently recommend changing fluid therapy to the use of a balanced colloid preparation.

Best Practice & Research Clinical Anaesthesiology 2009;23:225-236

Haemostatic alterations associated with the use of fluids are related to non-specific dilutional effects and colloid-specific effects, such as acquired von Willebrand syndrome, inhibition of platelet function and fibrin polymerization. Judging by currently available evidence, dextran, hetastarch and pentastarch have a more pronounced impact than tetrastarch, gelatin and albumin. In patients with hypocoagulability, tetrastarch appears to be a suitable volume expander due to its high safety index and volume efficacy. Gelatins have lower inhibitory effects on clot strength compared with tetrastarch, but their volume efficacy is also lower. Dextrans are potent anticoagulants with a high risk for adverse reactions. Albumin has negligible effects on haemostasis, but low volume efficacy and costs limit the use of a blood product as a routine volume replacement fluid. To avoid potential acidosis-induced changes in haemostasis, plasma-adapted carrier solutions may be used instead of saline-based solutions.Haemostatic alterations associated with the use of fluids are related to non-specific dilutional effects and colloid-specific effects, such as acquired von Willebrand syndrome, inhibition of platelet function and fibrin polymerization. Judging by currently available evidence, dextran, hetastarch and pentastarch have a more pronounced impact than tetrastarch, gelatin and albumin. In patients with hypocoagulability, tetrastarch appears to be a suitable volume expander due to its high safety index and volume efficacy. Gelatins have lower inhibitory effects on clot strength compared with tetrastarch, but their volume efficacy is also lower. Dextrans are potent anticoagulants with a high risk for adverse reactions. Albumin has negligible effects on haemostasis, but low volume efficacy and costs limit the use of a blood product as a routine volume replacement fluid. To avoid potential acidosis-induced changes in haemostasis, plasma-adapted carrier solutions may be used instead of saline-based solutions.

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;113:766-776

Qualitative arterial waveform analysis has been in existence for millennia; quantitative arterial waveform analysis techniques, which can be traced back to Euler’s work in the 18th century, have not been widely used by anesthesiologists and other clinicians. This is likely attributable, in part, to the widespread use of the sphygmomanometer, which allows the practitioner to assess arterial blood pressure without having to develop a sense for the higher-order characteristics of the arterial waveform. The 20-year delay in the development of devices that measure these traits is a testament to the primitiveness of our appreciation for this information. The shape of the peripheral arterial pressure waveform may indeed contain information useful to the anesthesiologist and intensivist. The maximal slope of the peripheral arterial pressure tracing seems to be related to left ventricular contractility, although the relationship may be confounded by other hemodynamic variables. The area under the peripheral arterial pressure tracing is related to stroke volume when loading conditions are stable; this finding has been used in the development of several continuous cardiac output monitors. Pulse wave velocity may be related to vascular impedance and could potentially improve the accuracy of waveform-based stroke volume estimates. Estimates of central arterial pressures (e.g., aortic) can be produced from peripheral (e.g., brachial, radial) tracings using a Generalized Transfer Function, and are incorporated into the algorithms of several continuous cardiac output monitors.