European Journal of Cardiovascular Medicine

There is no universally accepted definition of low-flow anaesthesia, although it implies a lower carrier gas flow than is attainable with a non-absorber breathing system. Low‑flow anaesthesia is defined as an inhalation anaesthetic technique in which the rebreathing fraction at least amounts to 50%, where at least 50% of the exhaled gas mixture is returned to the patient after CO2 removal in the next inspiration, which can be achieved when FG flow (FGF) is reduced to at least 2 L/min or less.

Desflurane is highly fluorinated methyl ethyl ether (1,2,2,2-tetrafluoroethyl difluoromethyl ether). Desflurane, due to its higher cost and lower potency compared to other inhalational agents, increases the direct cost of providing anaesthesia care. However, due to early recovery from anaesthesia, particularly in elderly and obese patients, the use of desflurane could contribute to early recovery, mobilisation, and a reduction in morbidity and indirect costs. Using the opioid adjuvants, nitrous oxide, and low flow anaesthesia could reduce desflurane consumption and its associated cost and environmental impact. (1, 2)

Cardiovascular effects of desflurane are mediated by direct and indirect mechanisms. Similar to other inhalational drugs, desflurane causes a dose-dependent decrease in systemic vascular resistance and arterial blood pressure via inhibiting the Sympathetic system.  (1, 3)

Laparoscopic procedures offer significant advantages to the patient, including reduced incision size and stress, decreased postoperative pain, accelerated healing rates, and a lower incidence of postoperative wound infections. All of these factors contribute to a shorter hospital stay and a decrease in perioperative morbidity. (4)

This study was undertaken to assess the hemodynamic parameters i.e. pulse rate and mean arterial pressure during induction and maintenance of low flow anaesthesia using desflurane as inhalational anaesthetic agent in major surgical procedures

This study was a prospective observational study was carried out prospectively in Department of Anesthesiology in a tertiary care hospital after getting approval from ethical committee of institution during period 1-1-2023 to 31-12-2024.

Inclusion criteria:

Adult patients of age 18-65 years, ASA grade 1 or 2, and General surgery and Otorhinolaryngology patients posted for various surgical procedures under general anaesthesia.

Exclusion criteria: Patients unwilling, ASA Grade 3 and 4, those with mental incapacity or language barrier, BMI over 35, active cancer, coagulation disorders, severe heart failure.

Sample size: A total of 140 Patients were studied, divided into 2 groups alternatively with 70 patients in each group based on surgery i.e., laparoscopic (n = 70) or non-laparoscopic (n = 70).

Standard protocol of anaesthesia induction, maintenance and monitoring were followed in all patients. Patients were pre medicated with Intravenous (IV) Glycopyrrolate 0.2mg, Midazolam 0.3mg/kg, and Fentanyl 2mcg/kg.   Patients were preoxygenated with 100% oxygen using dual limb closed circuit till end-tidal oxygen concentration reaches 90%. Anaesthesia induction by administering intravenous (IV) Propofol 2 mg/kg, and Rocuronium 1 mg/kg. Patient were hand ventilated with help of a facemask using FGF of oxygen 6 L/min for 60 seconds. Trachea was then intubated. Desflurane was set at 6% on vaporizer dial. Once the ratio of expired (Fe) to inspired (Fi) Desflurane concentration became 0.8, high FGF was reduced to the Low FGF mixture, i.e., 1 L/min of oxygen.

Microsoft excel was used for statistics and Continuous and categorical variables are expressed as mean ± standard deviation. Differences in subject characteristics between Laparoscopic and Non-Laparoscopic surgeries were analyzed using the t-test for continuous variables and the Chi-squared test/Fisher’s exact test for categorical variables. Linear regression used for analysing association between variables.

One forty adult patients were studied. No patient was excluded. Patients were divided into 2 groups based on the type of surgery (non-laparoscopic vs Laparoscopic) and were compared and there was no statistically significant difference is noted with respect to age, gender and Weight as shown in table 1.

While studying the haemodynamic parameters, it was found that there was no significant difference in Pulse rate between Laparoscopic and Non-laparoscopic group as shown in table 2; while there was significant difference in Mean arterial pressure between Laparoscopic and Non-laparoscopic group, but the difference is not clinically relevant and is within normal range.

TABLE 1 showing age and gender and weight-wise distribution of patients in 2 groups

          Test applied: Chi-square test.

TABLE 2 showing comparison of Mean (SD) Heart rate changes between Laparoscopic and Non-laparoscopic group.

applied-student unpaired t-test

TABLE 3 showing comparison of Mean (SD) Mean arterial Blood Pressure changes between Laparoscopic and Non-laparoscopic group.

applied-student unpaired t-test

A total number of 140 patients with age group 18 – 65 years were selected for the study. Age distribution is comparable in both laparoscopic and non-laparoscopic surgeries by 36.21 ± 12.86 and 38.94 ± 13.43 (p = 0.145) respectively and most patients in age groups of 21-30 (50/140) followed by 31-40 (38/140) and both groups are comparable by proportion of populations by specific age groups (X2 = 6.51 and p = 0.251)

This is similar to the age distribution in a study by Shelgaonkar VC et al with age distribution in laparoscopic and non-laparoscopic surgeries with 31.92 ± 14.11 and 36.2 ± 11.33 respectively (5). But lesser than the age group in a study by Horwitz M et al (46 ± 12) (6). Patients with age >65 years were not included in the study as elderly patients may be at increased risk for hemodynamic changes during the perioperative period. Age-related changes in cardiovascular function, including decreased cardiac output, decreased peripheral vasomotor tone, and decreased baroreceptor sensitivity, can contribute to hemodynamic instability in the elderly. (7)

Patients were divided based on the planned surgery into two groups, Non-Laparoscopic surgery group (n = 70) and Laparoscopic surgery group (n = 70).

Patients were induced by administration of intravenous (IV) Propofol 2mg/kg and Rocuronium 1mg/kg. Patients were then ventilated with with help of a facemak using FGF of 6L/min for 60 seconds and trachea was then intubated. Only 100% oxygen was used till intubation and desflurane or any other inhalational agent is used before intubation since there is potential danger for laryngospasm and increased secretions with Desflurane use. (8)

The depth of anaesthesia for induction is ensured both clinically and achieving BIS values between 40 – 60, though both methods are similar in outcome, (9) clinical assessment is better than BIS guided monitoring due to a shortcoming in BIS algorithm which limits the estimation of fentanyl induced potentiation of propofol sedation effect. Due to the use of 100% O2 as the carrier gas in this study, any potential paradoxical effects of N2O on BIS were avoided. (10)

Maintenance of Anaesthesia: Expiratory desflurane concentration is 80% of Inspiratory concentrations at equilibration point or 0 min (Inspiratory desflurane concentration at equilibration point is 5.7 + 0.2 while expiratory  4.52 + 0.2) since this study employed the equilibration method shifting from high flow to low flow anaesthesia the mean expiratory concentration gradually approaches towards inspiratory desflurane concentration (5.78 + 0.3 inspiratory and 5.17 + 0.3 expiratory desflurane concentrations at 170 min).

Hemodynamic monitoring: Pulse rate and Mean arterial blood pressure are monitored during the preoperative period till the complete recovery from anaesthesia. There is no clinically significant difference in pulse rate throughout the surgery between non-laparoscopic and laparoscopic surgeries respectively at 5min 80.91+10.43, 80.68+11.03 and at 70.94+10.62, 70.51+13.31 at 30 min (Table 2).

 The Mean arterial blood pressure was comparable at equilibration in both non-laparoscopic and laparoscopic groups 110.97 +6.85, 110.57+6.15 respectively but significantly increased in laparoscopic group after pneumoperitoneum (96.71+6.71, 102.2+5.94 at 30 min p = <0.001)(Table 3) which could be attributable to increased arterial CO2 tension and physiologic effects of laparoscopic surgeries). (11)

In a study by Tanrivedi et al., the Mean Arterial Pressure and Heart Rate of the Low flow and high flow groups did not differ significantly (12). Pulse rate does not differ significantly between laparoscopic and non-laparoscopic groups in this study (Table 2), whereas mean arterial pressure is significantly higher in laparoscopic than non-laparoscopic procedures, especially after CO2 insufflation (Table 3), but the difference is not clinically significant and is within 20% of baseline values. Thus, it is evident that low flow anaesthesia with desflurane is safe for administration in both laparoscopic and non-laparoscopic surgeries and found to be rapid in equilibration and recovery with no hemodynamic instability and risk of hypoxia.

We conclude that Desflurane with low flow anaesthesia technique is safe and hemodynamically stable and can be recommended for use in patients undergoing general anaesthesia for various procedures under both laparoscopic and non-laparoscopic surgeries.

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