The effect of heat-moisture exchanger and closed-circuit technique on airway climate during desflurane anesthesia

The Effect of Sevoflurane Low-Flow Anesthesia on Preserving Patient Core Temperature

<b><i>Introduction:</i></b> Low-flow anesthesia (LFA) reduces the fresh gas flow (FGF) entering the anesthesia circuit and saves on the volatile agent used. In this study, the effect of LFA with sevoflurane on core temperature and the incidence of perioperative hypothermia were investigated. <b><i>Methods:</i></b> According to the FGF applied, patients were classified into three groups: LFA (1 L/min), medium-flow anesthesia (MFA = 2 L/min), and high-flow anesthesia (HFA = 4 L/min). Patients’ demographic data and the initial (T1) and final (T2) core temperatures during the operation were compared. <b><i>Results:</i></b> A total of 160 patients were included in the study. The T2 value of the HFA group was significantly lower than the LFA group (<i>p</i> = 0.028). Different flow values were found to have a significant effect on temperature change (<i>F</i> = 21.630, <i>p</i> &#x3c; 0.001, partial eta squared = 0.216). There was a significant difference between the mean temperatures measured at two different times (<i>F</i> = 301.064, <i>p</i> &#x3c; 0.001, partial eta squared = 0.657). The overall incidence of hypothermia was 32.5%, with 52 patients. Hypothermia (<i>T</i>²&#x3c;36°C) incidences were not different between the LFA group and the MFA and HFA groups (<i>p</i> = 0.682). However, perioperative core temperature loss was significantly lower in the LFA group (<i>p</i> = 0.001). <b><i>Conclusions:</i></b> LFA using sevoflurane was not sufficient alone to significantly reduce the incidence of hypothermia. However, we have demonstrated that it may also have a beneficial effect on reducing perioperative temperature loss.

Comparison of the temperature and humidity in the anesthetic breathing circuit among different anesthetic workstations: Updated guidelines for reporting parallel group randomized trials

BACKGROUND

For patients undergoing general anesthesia, adequate warming and humidification of the inspired gases is very important. The aim of this study was to evaluate the differences in the heat and moisture content of the inspired gases with low-flow anesthesia using 4 different anesthesia machines.

METHODS

The patients were divided into 11 groups according to the anesthesia machine used (Ohmeda, Excel; Avance; Dräger, Cato; and Primus) and the fresh gas flow (FGF) rate (0.5, 1, and 4 L/min). The temperature and absolute humidity of the inspired gas in the inspiratory limbs were measured at 5, 10, 15, 30, 45, 60, 75, 90, 105, and 120 minutes in 9 patients scheduled for total thyroidectomy or cervical spine operation in each group.

RESULTS

The anesthesia machines of Excel, Avance, Cato, and Primus did not show statistically significant changes in the inspired gas temperatures over time within each group with various FGFs. They, however, showed statistically significant changes in the absolute humidity of the inspired gas over time within each group with low FGF anesthesia (P < .05). The anesthesia machines of Cato and Primus showed statistically significant changes in the absolute humidity of the inspired gas over time within each group with an FGF of 4 L/min (P < .05). However, even with low-flow anesthesia, the temperatures and absolute humidities of the inspired gas for all anesthesia machines were lower than the recommended values.

CONCLUSION

There were statistical differences in the provision of humidity among different anesthesia workstations. The Cato and Primus workstations were superior to Excel and Avance. However, even these were unsatisfactory in humans. Therefore, additional devices that provide inspired gases with adequate heat and humidity are needed for those undergoing general anesthetic procedures.

The effect of the humidifier on sore throat and cough after thyroidectomy

BACKGROUND

This study was performed to determine the effects of a humidifier with heated wire circuits on the incidence and severity of postoperative sore throat (POST) and cough after thyroidectomy.

METHODS

A total of 61 patients scheduled for elective thyroid surgery under general anesthesia were included in this prospective study. We randomized the patients in to two groups, "without active warming and humidification" (Group C) and "using a heated humidifier" (Group H). The patients were interviewed to obtain the POST and cough scores at 1, 6, 24 and 48 hours after thyroidectomy.

RESULTS

The incidence of POST was significantly lower in Group H compared to Group C at 6 hours (57% vs 84%, P = 0.041), 24 hours (37% vs 65%, P = 0.045), and 48 hours (10% vs 52%, P = 0.001). Also the incidence of cough was significantly lower in Group H at 6 hours (27% vs 71%, P = 0.001), 24 hours (13% vs 45%, P = 0.015), and 48 hours (7% vs 32%, P = 0.028). The severity of POST was significantly lower in Group H at all times. In addition, the severity of cough was lower in Group H at other times except at 1 hour.

CONCLUSIONS

This result suggests that an active humidification of inspired gases may have the appreciable effect on reducing the incidence and severity of sore throat and cough after thyroid surgery using the endotracheal tube.