End-tidal versus manually-controlled low-flow anaesthesia

Abstract

During low-flow manually-controlled anaesthesia (MCA) the anaesthetist needs constantly adjust end-tidal oxygen (EtO2) and anaesthetic concentrations (EtAA) to assure an adequate and safe anaesthesia. Recently introduced anaesthetic machines can automatically maintain those variables at target values, avoiding the burden on the anaesthetist. End-tidal-controlled anaesthesia (EtCA) and MCA provided by the same anaesthetic machine under the same fresh gas flow were compared. Eighty patients were prospectively observed: in MCA group (n = 40) target end-tidal sevoflurane (1%) and EtO2 concentrations (≥ 35%) were manually controlled by the anaesthetist. In EtCA group (n = 40) the same anaesthetic machine with an additional end-tidal control feature was used to reach the same targets, rendering automatic the achievement and maintenance of those targets. Anaesthetic machine characteristics, amount of consumed gases, oxygen and sevoflurane efficiencies, and the amount of interventions by the anaesthetist were recorded. In EtCA group EtAA was achieved later (145 s) than in MCA (71 s) and remained controlled thereafter. Even though the target expired gas fractions were achieved faster in MCA, manual adjustments were required throughout anaesthesia for both oxygen and sevoflurane. In MCA patients the number of manual adjustments to stabilize EtAA and EtO2 were 137 and 107, respectively; no adjustment was required in EtCA. Low-flow anaesthesia delivered with an anaesthetic machine able to automatically control EtAA and EtO2 provided the same clinical stability and avoided the continuous manual adjustment of delivered sevoflurane and oxygen concentrations. Hence, the anaesthetist could dedicate more time to the patient and operating room activities.

Porównanie zużycia gazów anestetycznych oraz stabilności znieczulenia przy użyciu automatycznej i ręcznej kontroli przebiegu znieczulenia

“…Moreover, the authors demonstrated no differences in the time to eye opening and extubation between automated and manual methods. Otherwise, the results published by Lucangelo et al [8] are contrary to our data. Lucangelo et al demonstrated that the required concentration of inhalational anaesthetic was achieved more rapidly in the group with manual control.…”

“…Similar results have been presented by other researchers [6][7][8][9]. In his 10-year observation, Kennedy et al [9] found that automated control of inhalational anaesthetic substantially decreased the additional burden on the anaesthetist and potentially increased the safety of anaesthetised patients.…”

“…The use of automated modules (EtC, end tidal control) reduces the consumption of anaesthetic gases and increases the stability of anaesthesia by steady changes in the flow of individual components of gas mixtures. The modules are designed to limit the number of necessary adjustments of the settings of ventilatory parameters, which potentially increases the safety of anaesthetised patients [8,9].…”

Automated control of end-tidal sevoflurane in living donor hepatectomy, a prospective, randomized, controlled study

“…New anesthetic machines; Drager Zeus, GE Aisys, and Maquet flow-I, incorporated a closed loop system, in which the target end-tidal anesthetic concentration, minimum flow rate, and target end-tidal oxygen concentration (EtO2) are set, then the machine automatically modifies inspired agent and fio2 to maintain end-tidal concentrations determined by the anesthesiologist. This is assumed to lower anesthetic gases consump-tion with more stable brain concentration resulting in less required anesthesiologist interventions to modify either inhaled anesthetic or oxygen concentrations [5][6][7].…”

“…Most of the studies that investigated EtC were conducted for relatively short period surgeries and non-homogenous patients [6,[8][9][10][11][12]. In our study, we applied EtC mode (Aisys CS2 anesthesia delivery systems, USA) during living donor right hepatectomy where the average anesthetic duration is around 6 h [7,13].…”