Efficiency of CONTRAfluran™ in reducing sevoflurane pollution from maintenance anaesthesia in minimal flow end-tidal control mode for laparoscopic surgery.

BACKGROUND: Recommendations exist that aim to mitigate the substantial ecological impact of anaesthesia. One option is to use anaesthetic gas capturing technology at anaesthesia workstation exhausts to harvest and recycle volatile agents. However, the efficiency of such technology is mainly unverified in vivo. METHODS: The efficiency of CONTRAfluran™ in capturing sevoflurane from an anaesthesia workstation exhaust (when set to minimal flow and end-tidal control mode) was evaluated in 70 adult patients scheduled for general or bariatric laparoscopic surgery. The weight of the sevoflurane vaporiser and CONTRAfluran canister was measured before and after each case, to calculate total sevoflurane consumption and retention. Retention was measured after the minimal flow maintenance phase and after the high flow washout phase. The total retention efficiency was the fraction of all consumed sevoflurane captured by the CONTRAfluran canister. The primary objective was to examine the retention efficiency of CONTRAfluran in a clinical surgical setting, where all feasible strategies to minimise sevoflurane consumption and optimise the efficacy of CONTRAfluran were utilised. The secondary objective was to analyse the correlation between mass transfer and the duration of the case. RESULTS: Mean (SD) volume of sevoflurane captured using CONTRAfluran was 4.82 (1.41) ml, representing 45% (95%CI 42-48%) of all sevoflurane administered. The highest amount of retention was found during the washout phase. Retention efficiency did not correlate with the duration of the case. CONCLUSIONS: Over half of the sevoflurane administered was not captured by the CONTRAfluran canister when minimal flow techniques were used, likely due to residual accumulation of sevoflurane in the patient after tracheal extubation or, to a lesser extent, due to ventilation system leakage. However, as every prevented emission is commendable, CONTRAfluran may be a potentially valuable tool for reducing the environmental footprint of sevoflurane-based anaesthesia.

Sevoflurane consumption pattern by individual anaesthesiologists varies widely despite using the same high-end workstations in the same hospital.

Volatile anaesthetics are potent greenhouse gasses but contemporary workstations enable considerable savings while improving patient safety. Institutions may provide this technology to reduce the ecological footprint but proper training and motivation is required to maximize their ecologic and financial benefit. This study aims to compare the sevoflurane consumption of 22 anaesthesiologists in a medium sized hospital 4 years after flow-i workstations (Getinge, Sweden) entered into service, in three airway approaches: intubated patients, laryngeal mask ventilation, and mask anaesthesia. Typical sevoflurane consumption for each anaesthesiologist was defined as the mean cumulative consumption in the chronologically first 50 cases meeting the inclusion criteria for each airway group in 2019. The potential savings, if everyone were to adopt the approach of the more economical anaesthesiologists (15th percentile), was calculated. The CO2 equivalent emissions were calculated using a GWP20 of 702 and a GWP100 of 195. The median [range] consumption after 45 min was 10.9 [7.5-18.4] ml in intubated patients and 9.0 [7.4-15.3] ml in patients with laryngeal mask, and 9.9 [3.4-20.9] ml after 8 min with mask ventilation. This corresponds to a double to six fold consumption between the least and most wasteful approach. The typical CO2 equivalent emissions (GWP20) per anaesthesiologist varied between 8.0 and 19.6 kg/45 min in intubated airways, between 7.9 and 16.3 kg/45 min in LMA, and between 3.6 and 22.3 kg/8 min in mask ventilation. Despite using the same workstations in the same hospital, the typical sevoflurane consumption differed dramatically between 22 anaesthesiologists. In addition to providing advanced workstations, proper education is required to achieve the behavior change needed to reduce the pollution and financial waste associated with volatile anaesthetics.

Minimizing sevoflurane wastage by sensible use of automated gas control technology in the flow-i workstation: an economic and ecological assessment.

Both ecological and economic considerations dictate minimising wastage of volatile anaesthetics. To reconcile apparent opposing stakes between ecological/economical concerns and stability of anaesthetic delivery, new workstations feature automated software that continually optimizes the FGF to reliably obtain the requested gas mixture with minimal volatile anaesthetic waste. The aim of this study is to analyse the kinetics and consumption pattern of different approaches of sevoflurane delivery with the same 2% end-tidal goal in all patients. The consumption patterns of sevoflurane of a Flow-i were retrospectively studied in cases with a target end-tidal sevoflurane concentration (Etsevo) of 2%. For each setting, 25 cases were included in the analysis. In Automatic Gas Control (AGC) regulation with software version V4.04, a speed setting 6 was observed; in AGC software version V4.07, speed settings 2, 4, 6 and 8 were observed, as well as a group where a minimal FGF was manually pursued and a group with a fixed 2 L/min FGF. In 45 min, an average of 14.5 mL was consumed in the 2L-FGF group, 5.0 mL in the minimal-manual group, 7.1 mL in the AGC4.04 group and 6.3 mL in the AGC4.07 group. Faster speed AGC-settings resulted in higher consumption, from 6.0 mL in speed 2 to 7.3 mL in speed 8. The Etsevo target was acquired fastest in the 2L-FGF group and the Etsevo was more stable in the AGC groups and the 2L-FGF groups. In all AGC groups, the consumption in the first 8 min was significantly higher than in the minimal flow group, but then decreased to a comparable rate. The more recent AGC4.07 algorithm was more efficient than the older AGC4.04 algorithm. This study indicates that the AGC technology permits very significant economic and ecological benefits, combined with excellent stability and convenience, over conventional FGF settings and should be favoured. While manually regulated minimal flow is still slightly more economical compared to the automated algorithm, this comes with a cost of lower precision of the Etsevo. Further optimization of the AGC algorithms, particularly in the early wash-in period seems feasible. In AGC mode, lower speed settings result in significantly lower consumption of sevoflurane. Routine clinical practice using what historically is called "low flow anaesthesia" (e.g. 2 L/min FGF) should be abandoned, and all anaesthesia machines should be upgraded as soon as possible with automatic delivery technology to minimize atmospheric pollution with volatile anaesthetics.

Improved haemodynamic stability and cerebral tissue oxygenation after induction of anaesthesia with sufentanil compared to remifentanil: a randomised controlled trial.

BACKGROUND: Balanced anaesthesia with propofol and remifentanil, compared to sufentanil, often decreases mean arterial pressure (MAP), heart rate (HR) and cardiac index (CI), raising concerns on tissue-oxygenation. This distinct haemodynamic suppression might be attenuated by atropine. This double blinded RCT, investigates if induction with propofol-sufentanil results in higher CI and tissue-oxygenation than with propofol-remifentanil and if atropine has more pronounced beneficial effects on CI and tissue-oxygenation in a remifentanil-based anaesthesia. METHODS: In seventy patients scheduled for coronary bypass grafting (CABG), anaesthesia was induced and maintained with propofol target controlled infusion (TCI) with a target effect-site concentration (Cet) of 2.0 µg ml- 1 and either sufentanil (TCI Cet 0.48 ng ml- 1) or remifentanil (TCI Cet 8 ng ml- 1). If HR dropped below 60 bpm, methylatropine (1 mg) was administered intravenously. Relative changes (∆) in MAP, HR, stroke volume (SV), CI and cerebral (SctO2) and peripheral (SptO2) tissue-oxygenation during induction of anaesthesia and after atropine administration were analysed. RESULTS: The sufentanil group compared to the remifentanil group showed significantly less decrease in MAP (∆ = - 23 ± 13 vs. -36 ± 13 mmHg), HR (∆ = - 5 ± 7 vs. -10 ± 10 bpm), SV (∆ = - 23 ± 18 vs. -35 ± 19 ml) and CI (∆ = - 0.8 (- 1.5 to - 0.5) vs. -1.5 (- 2.0 to - 1.1) l min- 1 m- 2), while SctO2 (∆ = 9 ± 5 vs. 6 ± 4%) showed more increase with no difference in ∆SptO2 (∆ = 8 ± 7 vs. 8 ± 8%). Atropine caused higher ∆HR (13 (9 to 19) vs. 10 ± 6 bpm) and ∆CI (0.4 ± 0.4 vs. 0.2 ± 0.3 l min- 1 m- 2) in sufentanil vs. remifentanil-based anaesthesia, with no difference in ∆MAP, ∆SV and ∆SctO2 and ∆SptO2. CONCLUSION: Induction of anaesthesia with propofol and sufentanil results in improved haemodynamic stability and higher SctO2 compared to propofol and remifentanil in patients having CABG. Administration of atropine might be useful to counteract or prevent the haemodynamic suppression associated with these opioids. TRIAL REGISTRATION: Clinicaltrials.gov on June 7, 2013 (trial ID: NCT01871935 ).

A neuro-anatomically grounded scheme for LIA gives superior analgesia and comfort levels compared to epidural analgesia until seven days after total knee arthroplasty.

LIA is an emerging alternative for patient-con- trolled epidural analgesia(PCEA) after total knee arthroplasty(TKA). LIA allows faster mobilisation, eliminates the risks of epidural catheters, and can hasten patient turnover. Conversely, PCEA provides reliable pain relief in the first days after this type of surgery. The purpose of this study was to evaluate the quality of antinociception, postoperative nausea & vomiting (PONV), and general comfort until 7 days postoperatively. 40 patients received PCEA and 41 received LIA. Patients were retrospectively asked for pain scores at the day of surgery(=D0), D2, and D7, PONV, and general comfort scores. Patients in the LIA group reported equal pain scores at D0, significantly better PONV scores and pain scores at D2 and D7. In addition to faster mobilisation and elimination of the risks and burden of an epidural catheter and PCEA, LIA delivers equal to better analgesia, and better PONV and general comfort scores.

Articulated Instruments and 3D Visualization: A Synergy? Evaluation of Execution Time, Errors, and Visual Fatigue.

Objective. The introduction of advanced endoscopic systems, such as the Storz Image1S and the Olympus Endoeye, heralds a new era of 3-dimensional (3D) visualization. The aim of this report is to provide a comprehensive overview of the neurophysiology of 3D view, its relevance in videoscopy, and to quantify the benefit of the new 3D technologies for both rigid and articulated instruments. Method. Sixteen medical students without any laparoscopic experience were trained each for a total of 27 hours. Proficiency scores were determined for rigid and articulated instruments under 2D and 3D visualization conditions. Results. A reduction in execution time of 14%, 28%, and 36% was seen for the rigid instruments, the da Vinci, and Steerable instruments, respectively. A reduction in errors of 84%, 92%, and 87% was seen for the rigid instruments, the da Vinci, and Steerable instruments, respectively. Conclusion. 3D visualization greatly augments endoscopic procedures. The advanced endoscopic systems employed in the recent study caused no visual fatigue or discomfort. The benefit of 3D was most distinct with articulated instruments.

Prophylactic atropine administration attenuates the negative haemodynamic effects of induction of anaesthesia with propofol and high-dose remifentanil: A randomised controlled trial.

BACKGROUND: Induction of anaesthesia with propofol and remifentanil often induces unwanted bradycardia and hypotension, raising concerns regarding tissue oxygenation. The electrophysiological cardiac effects of remifentanil can be reversed by atropine. OBJECTIVE: To investigate if prophylactic administration of atropine can attenuate the negative haemodynamic effects of propofol and a high dose of remifentanil during induction of anaesthesia. DESIGN: A double-blind, randomised controlled trial. SETTING: Single-centre, University Medical Center Groningen, The Netherlands. PATIENTS: Sixty euvolaemic patients scheduled for surgery under general anaesthesia. INTERVENTIONS: Anaesthesia was induced and maintained with a target-controlled infusion of propofol with a target effect-site concentration (Ce) of 2.5 µg ml, remifentanil (target-controlled infusion), (Ce 8 ng ml) and cis-atracurium. Methylatropine (500 µg) or 0.9% saline was administered at immediately before induction of anaesthesia. MAIN OUTCOME MEASURES: The changes (Δ) in mean arterial pressure (MAP), heart rate (HR), cardiac index (CI), rate pressure product, cerebral tissue oxygenation and peripheral tissue oxygenation between induction of anaesthesia (T0) and 10 min later (T10). RESULTS: Atropine significantly attenuated the changes in the outcome measures between T0 and T10. Median (inter-quartile range) changes were MAP, Δ = -24 (-40 to -21) vs. Δ = -37 mmHg (-41 to -31) (P = 0.02); HR, Δ = 0 ±â€Š13 vs. -19 ±â€Š11 bpm (P < 0.01); CI, Δ = -0.4 ±â€Š0.7 vs. -0.9 ±â€Š0.6l min m (P < 0.01) and rate pressure product, Δ = -3241 (-5015 to -613) vs. Δ = -5712 mmHg min (-6715 to -3917) (P < 0.01). Cerebral tissue oxygenation and peripheral tissue oxygenation did not change in either group. Maximum HR after atropine was 102 (86 to 116) vs. 85 bpm (76 to 95). CONCLUSION: Administration of atropine, before induction of anaesthesia with propofol and high-dose remifentanil, can significantly reduce the decreases in HR, MAP and CI. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT01871922.

Comparisons of Electroencephalographically Derived Measures of Hypnosis and Antinociception in Response to Standardized Stimuli During Target-Controlled Propofol-Remifentanil Anesthesia.

BACKGROUND: Current electroencephalogram (EEG)-derived measures provide information on cortical activity and hypnosis but are less accurate regarding subcortical activity, which is expected to vary with the degree of antinociception. Recently, the neurophysiologically based EEG measures of cortical input (CI) and cortical state (CS) have been shown to be prospective indicators of analgesia/antinociception and hypnosis, respectively. In this study, we compared CI and an alternate measure of CS, the composite cortical state (CCS), with the Bispectral Index (BIS) and another recently developed measure of antinociception, the composite variability index (CVI). CVI is an EEG-derived measure based on a weighted combination of BIS and estimated electromyographic activity. By assessing the relationship between these indices for equivalent levels of hypnosis (as quantified using the BIS) and the nociceptive-antinociceptive balance (as determined by the predicted effect-site concentration of remifentanil), we sought to evaluate whether combining hypnotic and analgesic measures could better predict movement in response to a noxious stimulus than when used alone. METHODS: Time series of BIS and CVI indices and the raw EEG from a previously published study were reanalyzed. In our current study, the data from 80 patients, each randomly allocated to a target hypnotic level (BIS 50 or BIS 70) and a target remifentanil level (Remi-0, -2, -4 or -6 ng/mL), were included in the analysis. CCS, CI, BIS, and CVI were calculated or quantified at baseline and at a number of intervals after the application of the Observer's Assessment of Alertness/Sedation scale and a subsequent tetanic stimulus. The dependency of the putative measures of antinociception CI and CVI on effect-site concentration of remifentanil was then quantified, together with their relationship to the hypnotic measures CCS and BIS. Finally, statistical clustering methods were used to evaluate the extent to which simple combinations of antinociceptive and hypnotic measures could better detect and predict response to stimulation. RESULTS: Before stimulation, both CI and CVI differentiated patients who received remifentanil from those who were randomly allocated to the Remi-0 group (CI: Cohen's d = 0.65, 95% confidence interval, 0.48-0.83; CVI: Cohen's d = 0.72, 95% confidence interval, 0.56-0.88). Strong correlations between BIS and CCS were found (at different periods: 0.55 < R2 < 0.68, P < 0.001). Application of the Observer's Assessment of Alertness/Sedation stimulus was associated with changes in CI and CCS, whereas, subsequent to the application of both stimuli, changes in all measures were seen. Pairwise combinations of CI and CCS showed higher sensitivity in detecting response to stimulation than CVI and BIS combined (sensitivity [99% confidence interval], 75.8% [52.7%-98.8%] vs 42% [15.4%-68.5%], P = 0.006), with specificity for CI and CCS approaching significance (52% [34.7%-69.3%] vs 24% [9.1%-38.9%], P = 0.0159). CONCLUSIONS: Combining electroencephalographically derived hypnotic and analgesic quantifiers may enable better prediction of patients who are likely to respond to tetanic stimulation.

The use of the trendelenburg position in the surgical treatment of extreme cerebellar slump.

BACKGROUND: State-of-the-art treatment for Chiari Malformation I (CM-I) consists of decompression by posterior fossa craniectomy. A rare but severe complication that develops over months to years after this procedure is cerebellar slump. Treatment options for this condition are limited. We present a new and promising approach to treat this rare condition. METHODS: The patients were placed in the Trendelenburg position to facilitate ascent of the cerebellum. After almost complete dissolution of neurologic symptoms, surgical reconstruction was performed by tonsillar resection and the creation of a new structural support using a bone graft. RESULTS: Both patients experienced good clinical and morphological outcomes immediately after surgery, and for two years thereafter. CONCLUSIONS: Neurological symptoms related to cerebellar or brainstem slump can be adequately reversed by placing the patient in the Trendelenburg position. After uneventful gravitational reversal of the slump, safe surgical reconstruction of the cerebellar support can be performed to securely preserve the anatomical reversal.

Noninvasive pulse pressure variation and stroke volume variation to predict fluid responsiveness at multiple thresholds: a prospective observational study.

BACKGROUND: Pulse pressure variation (PPV) and stroke volume variation (SVV) are dynamic preload variables that can be measured noninvasively to assess fluid responsiveness (FR) in anesthetized patients with mechanical ventilation. Few studies have examined the effectiveness of predicting FR according to the definition of FR, and assessment of inconclusive values of PPV and SVV around the cut-off value (the "grey zone") might improve individual FR prediction. We explored the ability of noninvasive volume clamp derived measurements of PPV and SVV to predict FR using the grey zone approach, and we assessed the influence of multiple thresholds on the predictive ability of the numerical definition of FR. METHODS: Ninety patients undergoing general surgery were included in this prospective observational study and received a 500 mL fluid bolus as deemed clinically required by the attending anesthesiologist. A minimal relative increase in stroke volume index (↑SVI) was used to define FR with different thresholds from 10-25%. The PPV, SVV, and SVI were measured using the Nexfin® device that employs noninvasive volume clamp plethysmography. RESULTS: The area under the receiver operator characteristic curve gradually increased for PPV / SVV with higher threshold values (from 0.818 / 0.760 at 10% ↑SVI to 0.928 / 0.944 at 25% ↑SVI). The grey zone limits of both PPV and SVV changed from 9-16% (PPV) and 5-13% (SVV) at the 10% ↑SVI threshold to 18-21% (PPV) and 14-16% (SVV) at the 25% ↑SVI threshold. CONCLUSION: Noninvasive PPV and SVV measurements allow an acceptable FR prediction, although the reliability of both variables is dependent on the intended increase in SVI, which improves substantially with concomitant smaller grey zones at higher ↑SVI thresholds.

Differential effects of phenylephrine and norepinephrine on peripheral tissue oxygenation during general anaesthesia: A randomised controlled trial.

BACKGROUND: Phenylephrine and norepinephrine are two vasopressors commonly used to counteract anaesthesia-induced hypotension. Their dissimilar working mechanisms may differentially affect the macro and microcirculation, and ultimately tissue oxygenation. OBJECTIVES: We investigated the differential effect of phenylephrine and norepinephrine on the heart rate (HR), stroke volume (SV), cardiac index (CI), cerebral tissue oxygenation (SctO2) and peripheral tissue oxygenation (SptO2), and rate-pressure product (RPP). DESIGN: A randomised controlled study. SETTING: Single-centre, University Medical Center Groningen, The Netherlands. PATIENTS: Sixty normovolaemic patients under balanced propofol/remifentanil anaesthesia. INTERVENTIONS: If the mean arterial pressure (MAP) dropped below 80% of the awake state value, phenylephrine (100 µg + 0.5 µg kg(-1) min(-1)) or norepinephrine (10 µg + 0.05 µg kg(-1) min(-1)) was administered in a randomised fashion. MAIN OUTCOME MEASURES: MAP, HR, SV, CI, SctO2, SptO2 and rate-pressure product (RPP) analysed from 30 s before drug administration until 240 s thereafter. RESULTS: Phenylephrine and norepinephrine caused an equivalent increase in MAP [Δ = 13 (8 to 22) and Δ = 13 (9 to 19) mmHg, respectively] and SV [Δ = 6 ± 6 and Δ = 5 ± 7 ml, respectively], combined with a significant equivalent decrease in HR (both Δ = -8 ± 6 bpm), CI (both Δ = -0.2 ± 0.3 l min(-1) m(-2)) and SctO2 and an unchanged RPP (Δ = 345 ± 876 and Δ = 537 ± 1076 mmHg min(-1)). However, SptO2 was slightly but statistically significantly (P < 0.05) decreased after norepinephrine [Δ  = -3 (-6 to 0)%] but not after phenylephrine administration [Δ = 0 (-1 to 1)%]. In both groups, SptO2 after vasopressor was still higher than the awake value. CONCLUSION: In normovolaemic patients under balanced propofol/remifentanil anaesthesia, phenylephrine and norepinephrine produced similar clinical effects when used to counteract anaesthesia-induced hypotension. After norepinephrine, a fall in peripheral tissue oxygenation was statistically significant, but its magnitude was not clinically relevant.

Accuracy of the composite variability index as a measure of the balance between nociception and antinociception during anesthesia.

BACKGROUND: The Composite Variability Index (CVI), derived from the electroencephalogram, was developed to assess the antinociception-nociception balance, whereas the Bispectral Index (BIS) was developed to assess the hypnotic state during anesthesia. We studied the relationships between these indices, level of hypnosis (BIS level), and antinociception (predicted remifentanil effect-site concentrations, CeREMI) before and after stimulation. Also, we measured their association with movement in response to a noxious stimulus. METHODS: We randomized 120 patients to one of 12 groups targeting different hypnotic levels (BIS 70, 50, and 30) and various CeREMI (0, 2, 4, or 6 ng/mL). At pseudo-steady state, baseline values were observed, and a series of stimuli were applied. Changes in BIS, CVI, heart rate (HR), and mean arterial blood pressure (MAP) between baseline and response period were analyzed in relation to level of hypnosis, antinociception, and somatic response to the stimuli. RESULTS: CVI and BIS more accurately correlate with somatic response to an Observer Assessment of Alertness and Sedation-noxious stimulation than HR, MAP, CeREMI, and propofol effect-site concentration (Tukey post hoc tests P < 0.01). Change in CVI is more adequate to monitor response to stimulation than changes in BIS, HR, or MAP (as described by the Mathews Correlation Coefficient with significance level set at P < 0.001). In contrast, none of the candidate analgesic state indices was uniquely related to a specific opioid concentration and is extensively influenced by the hypnotic state as measured by BIS. CONCLUSIONS: CVI appears to correlate with somatic responses to noxious stimuli. However, unstimulated CVI depends more on hypnotic drug effect than on opioid concentration.

Tissue oxygenation as a target for goal-directed therapy in high-risk surgery: a pilot study.

BACKGROUND: Tissue hypoperfusion occurs frequently during surgery and may contribute to postoperative organ dysfunction. There is a need for perioperative treatment protocols aiming at improving tissue oxygenation (StO2). We hypothesised that intra-operative optimisation of StO2 improves tissue perfusion and thus reduces postoperative complications. Furthermore, we evaluated the feasibility of the optimisation algorithm used. METHODS: We randomized 50 high-risk patients, all >65 years with ASA physical status III, who underwent major abdominal surgery under standardized balanced general anesthesia combined with epidural analgesia. Throughout surgery StO2 was monitored at the thenar eminence using near-infrared spectroscopy. All patients were treated according to a standard care algorithm. In addition, patients in the intervention group were treated with dobutamine if necessary to keep or raise StO2 ≥ 80%. Data were recorded continuously and complications were recorded during hospital stay with a maximum of 28 days. RESULTS: The number of complications was not significantly different between groups (11 vs 20; p = 0.23). Eleven patients in the intervention group had no complication, versus 7 in the control group. There was no significant difference between groups in length of stay in ICU or in hospital. Only ten patients in the intervention group received dobutamine. Administration of dobutamine resulted in a moderate 6 [-3 to 10] % increase of StO2. The overall protocol adherence was 94%. CONCLUSIONS: No statistically significant difference in outcome was realized through intraoperative optimization of StO2 values in this pilot study. The protocol used may be considered feasible for clinical practice. Further research is obligatory to define both the optimal StO2 threshold and intervention to treat tissue hypoperfusion. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01342900. Registered 21 April 2011.