Abstract
The same doses of anesthesia may yield varying depths of anesthesia in different patients. Clinical studies have revealed a possible causal relationship between deep anesthesia and negative short- and long-term patient outcomes. However, a reliable index and method of the clinical monitoring of deep anesthesia and detecting latency remain lacking. As burst-suppression is a characteristic phenomenon of deep anesthesia, the present study investigated the relationship between burst-suppression latency (BSL) and the subsequent burst-suppression ratio (BSR) to find an improved detection for the onset of intraoperative deep anesthesia. The mice were divided young, adult and old group treated with 1.0% or 1.5% isoflurane anesthesia alone for 2 h. In addition, the adult mice were pretreated with intraperitoneal injection of ketamine, dexmedetomidine, midazolam or propofol before they were anesthetized by 1.0% isoflurane for 2 h. Continuous frontal, parietal and occipital electroencephalogram (EEG) were acquired during anesthesia. The time from the onset of anesthesia to the first occurrence of burst-suppression was defined as BSL, while BSR was calculated as percentage of burst-suppression time that was spent in suppression periods. Under 1.0% isoflurane anesthesia, we found a negative correlation between BSL and BSR for EEG recordings obtained from the parietal lobes of young mice, from the parietal and occipital lobes of adult mice, and the occipital lobes of old mice. Under 1.5% isoflurane anesthesia, only the BSL calculated from EEG data obtained from the occipital lobe was negatively correlated with BSR in all mice. Furthermore, in adult mice receiving 1.0% isoflurane anesthesia, the co-administration of ketamine and midazolam, but not dexmedetomidine and propofol, significantly decreased BSL and increased BSR. Together, these data suggest that BSL can detect burst-suppression and predict the subsequent BSR under isoflurane anesthesia used alone or in combination with anesthetics or adjuvant drugs. Furthermore, the consistent negative correlation between BSL and BSR calculated from occipital EEG recordings recommends it as the optimal position for monitoring burst-suppression.
Highlights
Drug-induced general anesthesia is characterized by unconsciousness, amnesia, analgesia, and the relative stability of the autonomic, cardiovascular, respiratory, and thermoregulatory systems (Brown et al, 2010; Nicolaou et al, 2012)
Under 1.0 and 1.5% isoflurane anesthesia, the mice were divided into three groups including young, adult and old group and the EEG were recorded for 2 h respectively; The adult mice were pretreated with intraperitoneal injection of sub-anesthetic dose of ketamine (25 mg/kg) (Kamiyama et al, 2011), lower doses of dexmedetomidine (15 μg/kg) (Zhang et al, 2015), midazolam (0.5 mg/kg) (Baptista et al, 2009) or propofol (Kimura-Kuroiwa et al, 2012) before they were anesthetized by 1.0% isoflurane for 2 h
We studied the correlation between burst-suppression latency (BSL) and burst-suppression ratio (BSR) when adult mice were subjected to 1.0% isoflurane anesthesia with a coadministration of anesthetics or adjuvant drugs
Summary
Drug-induced general anesthesia is characterized by unconsciousness, amnesia, analgesia, and the relative stability of the autonomic, cardiovascular, respiratory, and thermoregulatory systems (Brown et al, 2010; Nicolaou et al, 2012). A scalp electroencephalogram (EEG) obtained during the onset of general anesthesia is associated with the progressive increase of low-frequency and high-amplitude activity (Kiersey et al, 1951; Akeju et al, 2016). The EEG may present a peculiar pattern of activity known as burst-suppression: highvoltage brain activity (bursts) alternates with periods of isoelectric quiescence (suppressions) (Lewis et al, 2013). Burst-suppression ratio (BSR) is commonly used as an important part of anesthesia depth monitoring, previous reports have shown that the BSR negatively correlates with the bispectral index The BSR has been demonstrated to be a reliable parameter in the assessment of the depth-of-anesthesia and deep anesthesia
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