Sevoflurane in low-flow anesthesia using "equilibration point"

Minimal fixed flow anesthesia for off-pump coronary artery bypass surgery: A parallel randomized trail

Objectives

The aim of the present study was to test a safety of a fixed minimal (0.5 l/min) fresh gas flow (FGF) anesthesia as a method ensuring adequate oxygenation during off-pump coronary artery bypass grafting operations.

Design

A randomized, prospective study.

Setting

Single-center clinical hospital affiliated with a university.

Participants

208 patients underwent off-pump coronary artery bypass surgery.

Interventions

All patients received endotracheal inhalational anesthesia with fixed minimal FGF. Half of them were anesthetized by sevoflurane and another half by isoflurane. The fresh (carrier) gas was pure oxygen in the control groups and a mixture of medical air and oxygen (FiO2 0.8) in the trial groups.

Measurements and main results

In the control groups inhaled oxygen concentration changed minimally during the operation. In the trial groups in 28.8 % of cases inhaled oxygen concentration dropped below preliminary margin (0.4). Body surface area (BSA) (B = 38.7; p = 0.002) and patient's age (B = -0.47; p = 0.004) were retained into final logistic regression model as independent predictors. We divided BSA into subcategories and analyzed data by survival cox regression with Forward LR method. Patients with BSA>2.3 (Exp.B = 183) and BSA [2.2-2.3] (Exp.B = 59) had high chance to get less than 0.4 of inhaled oxygen concentration compared to the patients with BSA <2.0 (p < 0.001).Exp(B) or OR for the patients' age as independent predictor tested in multiple logistic regression was 0.628 In other words, for every year less the patient had 1/0.628 = 1.6 times more chance to reach the preliminary low margin (0.4) of oxygenation.

Conclusions

Fixed minimal FGF 0.5 l/min with FiO2 0.8 may not be sufficient for the younger patients with BSA >2.0 to maintain inhaled oxygen concentration above 0.4. Using pure oxygen as a carrier gas during fixed minimal flow long term anesthesia is much safer and more reliable.

Combined femoral-obturator-sciatic nerve block has superior postoperative pain score and earlier ambulation as compared to spinal anaesthesia for arthroscopic anterior cruciate ligament reconstruction

PURPOSE

Peripheral nerve blocks can be a suitable alternative to central neuraxial blockage, as the sole anaesthetic agent for better early postoperative outcomes, decreased hospital stay and earlier mobilisation after anterior cruciate ligament reconstruction (ACLR) surgery. The purpose of this study was to compare consciousness during the procedure, pain during early postoperative period (< 7 days), and perioperative outcomes following ACLR using combined sciatic, femoral, and obturator nerve blocks compared to the spinal anaesthesia.

METHODS

This was a prospective case-control study including patients between 18 and 55 years of age, with anterior cruciate ligament (ACL) injury confirmed clinically and radiologically and undergoing ACLR. Patients were allocated in the two groups alternatively, group 1 included patients who received combined nerve blocks, and group 2 included patients who received spinal anaesthesia for the surgery. The sensory effect, motor effect, adequacy of anaesthesia, perioperative analgesic use, duration of stay, postoperative pain (visual analogue scale 0-10 cm) and functional outcomes were noted.

RESULTS

There were 60 patients in each group. A total of seven patients in group 1 (11%) and two patients in group 2 (3%) needed conversion to general anaesthesia (n.s.). In group 1, out of 53 patients who underwent surgery, 26 patients had no perception of surgery in the joint, 17 patients had perception of manipulation of the knee joint, 4 patients had sense of touch, and 6 patients had sensation of pain in the knee (VAS scale less than 3). In group 2, out of 58 patients, 42 patients had no perception of surgery, 12 had a perception of manipulation of the knee joint, 2 had sense of touch, and 2 had sensation of pain in the knee. Blockage of sensory effect was significantly better in group 2 (p = 0.0001). However, the motor effect was comparable between the two groups (n.s.). Group 1 had significantly better pain scores 6, 12, and 18 h after the surgery. Moreover, patients in group 1 also had faster ambulation (mean difference of 5.5 h, p = 0.0001) and reduced hospital stay (mean difference of 8.4 h, p = 0.0001).

CONCLUSION

Combined sciatic, femoral, and adductor canal block is an effective sole anaesthetic modality for ACLR. The sensory effect was inferior when compared to spinal anaesthesia but sufficient for the procedure without the need for supplementation with any other anaesthetic modality. Patients receiving this combined nerve block had lesser early postoperative pain scores, earlier ambulation, and shorter hospital stay as compared to the spinal anaesthesia.

LEVEL OF EVIDENCE

Level 3.

The effect of different flow levels and concentrations of sevoflurane during the wash-in phase on volatile agent consumption: a randomized controlled trial

PURPOSE

The standard procedure for low-flow anesthesia usually incorporates a high fresh gas flow (FGF) of 4-6 L/minute during the wash-in phase. However, the administration of a high FGF (4-6 L/min) increases the inhaled anesthetic agent consumption. This study was designed to compare the sevoflurane consumption at 2 rates of flow and vaporizer concentration during the wash-in period.

METHODS

Patients were randomly enrolled into high FGF (HFGF) (n = 30) and low FGF (LFGF) (n = 30) groups. During the wash-in, the HFGF group received 4 L/minute FGF with a sevoflurane vaporizer setting of 2.5%, and the LFGF group received 1 L/minute FGF with a vaporizer setting of 8%. Once the wash-in was complete, anesthesia maintenance was performed with 0.5 L/min FGF with a vaporizer setting of 2.5-4.5% in both groups. The patient demographic data, bispectral index values, hemodynamic variables, wash-in time, sevoflurane consumption during the wash-in phase, and total sevoflurane consumption were analyzed.

RESULTS

The median sevoflurane consumption in the wash-in phase was 8.2 mL (7.1-9.3) in the HFGF group and 2.7 mL (2.2-3.1) in the LFGF group (p = 0.001). The mean total sevoflurane consumption was 17.41 ± 3.58 mL in the patients who received HFGF and 14.93 ± 3.57 mL in the LFGF group (p = 0.001). The mean wash-in completion time was 12.49 ± 2.79 min in the HFGF group and 3.35 ± 0.67 min in the LFGF group (p = 0.001).

CONCLUSIONS

The anesthetic agent consumption during the wash-in phase was approximately 3 times lower with the administration of sevoflurane at 1 L/minute FGF than the use of 4 L/minute FGF.

The effect of low flow anesthesia on hemodynamic and peripheral oxygenation parameters in obesity surgery

Objectives:

To investigate the effects of low-flow anesthesia on hemodynamic parameters and recovery from anesthesia in obese individuals undergoing laparoscopic surgery.

Methods:

This randomized-controlled and prospective study included 44 obese patients who underwent laparoscopic sleeve gastrectomy operation. The patients were randomly allocated into 2 groups as low-flow and high-flow anesthesia. Further, the groups compared in terms of hemodynamic parameters, anesthesia recovery times, operation times, and arterial blood gas parameters.

Results:

The groups were similar with respect to demographic data. Heart rate, peripheral oxygen saturation, arterial blood pressure measurements, end-tidal, and CO₂, lactate levels measurements were similar in both groups during the entire procedure. There was also no statistically significant difference in terms of arterial blood gas parameters or anesthesia recovery periods.

Conclusion:

Low-flow anesthesia in laparoscopic obesity surgery seems to be safer compared to high-flow anesthesia in terms of the adequacy of tissue perfusion, depth of anesthesia, and postoperative recovery.

A randomised prospective comparison of equilibration point and changing gas composition during low-flow anaesthesia with sevoflurane vs desflurane

Background and Aims:

Safety and economy are the main concerns while using low- flow anaesthesia with newer inhalational agents. The main objective of this study was to use and compare 'equilibration time' of sevoflurane and desflurane after change-over from high-to-low flow anaesthesia.

Methods:

This prospective study included consenting adult patients between 18–70 years undergoing elective surgery under general anaesthesia. Patients were randomised initially to receive high-flow anaesthesia with 1.3 MAC of either desflurane or sevoflurane with nitrous oxide. After equilibration point, low-flow anaesthesia was initiated. Heart rate, non-invasive blood pressure, pulse oximeter, 5 electrode ECG and gas monitoring was done. Statistical analysis was done with the help of Med CalC version 12.5.0.0 (student version) and IBM SPSS Version 20.0.

Results:

Mean equilibration time in sevoflurane group was higher (4.59 ± 0.77 minutes) than desflurane group (3.78 ± 0.56 minutes, P < 0.001). Inspired concentrations of both inhalational agents varied from their vaporiser settings over 2 hours, more so with sevoflurane than desflurane. Inspired oxygen concentration (FiO2) remained above 30% during anaesthesia in both groups with stable haemodynamics.

Conclusion:

Change-over from high-to-low flow anaesthesia is faster in desflurane. With fresh gas flow (FGF) of 1 L with 50% oxygen and dial concentration of 1–1.5% of sevoflurane and 3.8–4.4% of desflurane, the risk of hypoxia is minimal. The disparity between the set and delivered concentrations is more (20%) in sevoflurane than desflurane (12%).