Effect of morphine-diazepam on signs of anesthesia, awareness, and dreams of patients under N2O for cesarean section

Adequacy of maternal anesthesia depth with two sodium thiopental doses in elective caesarean section: a randomized clinical trial

Background

Administration of an optimal dose of anesthetic agent to ensure adequate depth of hypnosis with the lowest risk of adverse effects to the fetus is highly important in cesarean section. Sodium thiopental (STP) is still the first choice for induction of anesthesia in some countries for this obstetric surgery. We aimed to compare two doses of STP with regarding the depth of anesthesia and the condition of newborn infants.

Methods

In this clinical trial, parturient undergoing elective Caesarian section were randomized into two groups receiving either low-dose (5 mg/kg) or high-dose (7 mg/kg) STP. Muscle relaxation was provided with succinylcholine 2 mg/kg and anesthesia was maintained with O2/N2O and sevoflurane. The depth of anesthesia was evaluated using isolated forearm technique (IFT) and bispectral index (BIS) in various phases. Additionally, infants were assessed using Apgar score and neurobehavioral test.

Results

Forty parturient were evaluated in each group. BIS was significantly lower in high-dose group at skin incision to delivery and subcutaneous and skin closure. Also, significant differences were noticed in IFT over induction to incision and incision to delivery. Apgar score was significantly lower in high-dose group at 1 min after delivery. Newborn infants in low-dose group had significantly better outcomes in all three domains of the neurobehavioral test.

Conclusion

7 mg/kg STP is superior to 5 mg/kg in creating deeper hypnosis for mothers. However, it negatively impacts Apgar score and neurobehavioral test of neonates. STP seems to has dropped behind as an acceptable anesthetic in Cesarean section.

Trial registration

IRCT No: 2016082819470 N45, 13/03/2019.

Anaesthetic interventions for prevention of awareness during surgery

BACKGROUND

General anaesthesia is usually associated with unconsciousness. 'Awareness' is when patients have postoperative recall of events or experiences during surgery. 'Wakefulness' is when patients become conscious during surgery, but have no postoperative recollection of the period of consciousness.

OBJECTIVES

To evaluate the efficacy of two types of anaesthetic interventions in reducing clinically significant awareness:- anaesthetic drug regimens; and- intraoperative anaesthetic depth monitors.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, ISSUE 4 2016); PubMed from 1950 to April 2016; MEDLINE from 1950 to April 2016; and Embase from 1980 to April 2016. We contacted experts to identify additional studies. We performed a handsearch of the citations in the review. We did not search trial registries.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) of either anaesthetic regimens or anaesthetic depth monitors. We excluded volunteer studies, studies of patients prior to skin incision, intensive care unit studies, and studies that only randomized different word presentations for memory tests (not anaesthetic interventions).Anaesthetic drug regimens included studies of induction or maintenance, or both. Anaesthetic depth monitors included the Bispectral Index monitor, M-Entropy, Narcotrend monitor, cerebral function monitor, cerebral state monitor, patient state index, and lower oesophageal contractility monitor. The use of anaesthetic depth monitors allows the titration of anaesthetic drugs to maintain unconsciousness.

DATA COLLECTION AND ANALYSIS

At least two authors independently scanned abstracts, extracted data from the studies, and evaluated studies for risk of bias. We made attempts to contact all authors for additional clarification. We performed meta-analysis statistics in packages of the R language.

MAIN RESULTS

We included 160 studies with 54,109 enrolled participants; 53,713 participants started the studies and 50,034 completed the studies or data analysis (or both). We could not use 115 RCTs in meta-analytic comparisons because they had zero awareness events. We did not merge 27 of the remaining 45 studies because they had excessive clinical and methodological heterogeneity. We pooled the remaining 18 eligible RCTs in meta-analysis. There are 10 studies awaiting classification which we will process when we update the review.The meta-analyses included 18 trials with 36,034 participants. In the analysis of anaesthetic depth monitoring (either Bispectral Index or M-entropy) versus standard clinical and electronic monitoring, there were nine trials with 34,744 participants. The overall event rate was 0.5%. The effect favoured neither anaesthetic depth monitoring nor standard clinical and electronic monitoring, with little precision in the odds ratio (OR) estimate (OR 0.98, 95% confidence interval (CI) 0.59 to 1.62).In a five-study subset of Bispectral Index monitoring versus standard clinical and electronic monitoring, with 34,181 participants, 503 participants gave awareness reports to a blinded, expert panel who adjudicated or judged the outcome for each patient after reviewing the questionnaires: no awareness, possible awareness, or definite awareness. Experts judged 351 patient awareness reports to have no awareness, 87 to have possible awareness, and 65 to have definite awareness. The effect size favoured neither Bispectral Index monitoring nor standard clinical and electronic monitoring, with little precision in the OR estimate for the combination of definite and possible awareness (OR 0.96, 95% CI 0.35 to 2.65). The effect size favoured Bispectral Index monitoring for definite awareness, but with little precision in the OR estimate (OR 0.60, 95% CI 0.13 to 2.75).We performed three smaller meta-analyses of anaesthetic drugs. There were nine studies with 1290 participants. Wakefulness was reduced by ketamine and etomidate compared to thiopental. Wakefulness was more frequent than awareness. Benzodiazepines reduces awareness compared to thiopental, ketamine, and placebo., Also, higher doses of inhaled anaesthetics versus lower doses reduced the risk of awareness.We graded the quality of the evidence as low or very low in the 'Summary of findings' tables for the five comparisons.Most of the secondary outcomes in this review were not reported in the included RCTs.

AUTHORS' CONCLUSIONS

Anaesthetic depth monitors may have similar effects to standard clinical and electrical monitoring on the risk of awareness during surgery. In older studies comparing anaesthetics in a smaller portion of the patient sample, wakefulness occurred more frequently than awareness. Use of etomidate and ketamine lowered the risk of wakefulness compared to thiopental. Benzodiazepines compared to thiopental and ketamine, or higher doses of inhaled anaesthetics versus lower doses, reduced the risk of awareness.

Alerting thresholds for the prevention of intraoperative awareness with explicit recall: a secondary analysis of the Michigan Awareness Control Study

BACKGROUND

Intraoperative awareness with explicit recall is a potentially devastating complication of surgery that has been attributed to low anaesthetic concentrations in the vast majority of cases. Past studies have proposed the determination of an adequate dose for general anaesthetics that could be used to alert providers of potentially insufficient anaesthesia. However, there have been no systematic analyses of appropriate thresholds to develop population-based alerting algorithms for preventing intraoperative awareness.

OBJECTIVE

To identify a threshold for intraoperative alerting that could be applied for the prevention of awareness with explicit recall.

DESIGN

Secondary analysis of a randomised controlled trial (Michigan Awareness Control Study).

SETTING

Three hospitals at a tertiary care centre in the USA.

PATIENTS

Unselected patients presenting for surgery under general anaesthesia.

INTERVENTIONS

Alerts based on end-tidal anaesthetic concentration or bispectral index values.

MAIN OUTCOME MEASURES

Using case and outcomes data from the primary study, end-tidal anaesthetic concentration and bispectral index values were analysed using Youden's index and c-statistics derived from a receiver operating characteristic curve to determine a specific alerting threshold for the prevention of awareness.

RESULTS

No single population-based threshold that maximises sensitivity and specificity could be identified for the prevention of intraoperative awareness, using either anaesthetic concentration or bispectral index values. The c-statistic for anaesthetic concentration was 0.431 ± 0.046, and 0.491 ± 0.056 for bispectral index values.

CONCLUSION

We could not derive a single population-based alerting threshold for the prevention of intraoperative awareness using either anaesthetic concentration or bispectral index values. These data indicate a need to move towards individualised alerting strategies in the prevention of intraoperative awareness.

TRIAL REGISTRATION

Primary trial registration (Michigan Awareness Control Study) ClinicalTrials.gov identifier: NCT00689091.

Comparison between propofol and dexmedetomidine on depth of anesthesia: A prospective randomized trial

BACKGROUND AND AIMS

Intravenous agents such as propofol are commonly used to maintain adequate depth of anesthesia. Dexmedetomidine which has an anesthetic sparing effect is being considered for maintaining intraoperative depth of anesthesia. We hypothesized to compare the effect of dexmedetomidine on depth of anesthesia with propofol and evaluated whether dexmedetomidine can be used as sole anesthetic agent in maintaining depth of anesthesia.

MATERIALS AND METHODS

Sixty patients of ASA PS I, 18-65 years of age, scheduled for laparotomy under general anesthesia were randomly divided into two groups of 30 each. Group A received propofol 1 mg/kg bolus followed by infusion (50 mcg/kg/min) and Group B received dexmedetomidine 1 mcg/kg bolus followed by infusion (0.5 mcg/kg/h). Both the groups were administered standard general anesthesia with routine monitoring along with Bispectral index (BIS) and values were recorded at intervals of 10 min. In all patients Ramsay sedation score was recorded after extubation and they were assessed for recall of intraoperative events using Modified Brice questionnaire.

RESULTS

Heart rate and mean arterial pressure were less in Group B than Group A. Intraoperative BIS values were significantly lower in Group B (P < 0.0001). Although sedation score was more in Group B it did not prolong recovery. No recall was found in any patient.

CONCLUSION

Dexmedetomidine was comparable with propofol in maintaining anesthesia and it can produce better control of hemodynamics and BIS value. Thus dexmedetomidine can be used as the sole maintenance anesthetic agent.

Survey on the adequacy of depth of anaesthesia with bispectral index and isolated forearm technique in elective Caesarean section under general anaesthesia with sevoflurane

BACKGROUND

Awareness during general anaesthesia for Caesarean section (C/S), although uncommon, remains a concern for anaesthesiologists. We examined the relationship between the bispectral index (BIS) and responses to the isolated forearm technique (IFT) to evaluate the adequacy of general anaesthesia in C/S and determine a suitable cut-off point for BIS values based on IFT results.

METHODS

In 61 parturients, a standardized anaesthetic technique was applied. It included sodium thiopental and succinylcholine for induction, and O2, N2O, and sevoflurane for maintenance of anaesthesia. BIS values and IFT response were recorded at 16 predetermined events during anaesthesia.

RESULTS

Positive IFT responses were seen in 41%, 46%, and 23% of the parturients at laryngoscopy, intubation, and skin incision, respectively. BIS could not reliably differentiate between IFT responders and non-responders during these three stages. The receiver operating characteristic curve cut-off points for BIS to predict IFT responders with 100% sensitivity were 34, 37, and 27, respectively, for these stages. In all stages of the operation after skin incision, more than 90% of parturients had no IFT test response, and BIS values between 40 and 63 were associated with negative IFT results. During a structured interview within 12-24 h after the operation, no patient had evidence of explicit recall of intraoperative events.

CONCLUSIONS

The BIS is not reliable for monitoring anaesthesia depth in C/S. Lower than previously recommended values are needed to avoid IFT test responses during laryngoscopy, intubation, and skin incision.

Assessment of intraoperative awareness with explicit recall: a comparison of 2 methods

BACKGROUND

Superiority of the modified Brice interview over quality assurance techniques in detecting intraoperative awareness with explicit recall has not been demonstrated definitively.

METHODS

We studied a single patient cohort to compare the detection of definite awareness using a single modified Brice interview (postoperative day 28-30) versus quality assurance data (postoperative day 1).

RESULTS

The incidence of awareness based on the modified Brice interview was 19 per 18,847 or 0.1%. Fewer awareness cases (incidence 0.02%) were detected by the quality assurance approach (P < 0.0001).

CONCLUSION

The modified Brice interview is the preferred modality for assessing intraoperative awareness with explicit recall.

Prevention of awareness during anaesthesia

Inadequate anaesthesia may lead to awareness. A properly trained anaesthetist, administering anaesthesia according to their knowledge of pharmacology and patient and surgical characteristics, assisted by clinical signs and monitoring, can minimize this risk. Relying upon volatile-based anaesthesia delivered at a concentration of at least 0.5 MAC may be effective, but this precludes the use of total intravenous anaesthesia techniques and in any case may lead to unwanted hypotension. Equipment failure may occur. Benzodiazepines do not protect the patient from awareness. The development of electroencephalographic monitors of anaesthetic depth provides an opportunity to prevent awareness. Two large scale studies, one of which was a randomized trial, have identified a 5-fold reduction in risk of awareness when depth of anaesthesia using bispectral index monitoring was used. The incidence of awareness can be further reduced with currently available techniques used more widely.

Dreaming during anaesthesia in adult patients

Dreaming during anaesthesia is defined as any recalled experience (excluding awareness) that occurred between induction of anaesthesia and the first moment of consciousness upon emergence. Dreaming is a commonly-reported side-effect of anaesthesia. The incidence is higher in patients who are interviewed immediately after anaesthesia (approximately 22%) than in those who are interviewed later (approximately 6%). A minority of dreams, which include sensory perceptions obtained during anaesthesia, provide evidence of near-miss awareness. These patients may have risk factors for awareness and this type of dreaming may be prevented by depth of anaesthesia monitoring. Most dreaming however, occurs in younger, fitter patients, who have high home dream recall, who receive propofol-based anaesthesia and who emerge rapidly from anaesthesia. Their dreams are usually short and pleasant, are related to work, family and recreation, are not related to inadequate anaesthesia and probably occur during recovery. Dreaming is a common, fascinating, usually pleasant and harmless phenomenon.

Awareness in anaesthesia: incidence, consequences and prevention

Awareness during anaesthesia is a state of consciousness that is revealed by explicit or implicit memory of intraoperative events. Although large clinical surveys indicate an incidence of explicit awareness of < 0.3% during anaesthesia for general surgery, this adverse effect should be a great concern, because patients may be permanently disabled by the experience of being awake during surgery. Prevention of awareness during anaesthesia starts with an appropriate preoperative visit to the patient. The anaesthetic delivery machines must be properly checked before and during anaesthesia. The anaesthetic depth should be assessed by observation of movement responses, and consequently a minimum of muscle relaxants used. Because the anaesthetic depth can be controlled by determination of endtidal drug concentration, volatile inhaled anaesthesia may be associated with a lower frequency of awareness than other anaesthetic regimens.

Intravenous benzodiazepines as anaesthetic agents: pharmacokinetics and clinical consequences

Despite extensive and numerous pharmacokinetic studies on benzodiazepines, the published pharmacokinetic data do not adequately explain the clinical differences found between different benzodiazepine derivatives after intravenous administration. Especially, correlations between initial drug responses and distributional changes of the benzodiazepines are limited. However, during the elimination phase some relationships exist between the kinetic and dynamic phenomena. Age, sex, diseases and concomitantly given drugs cause clinically important alterations in the pharmacokinetics of benzodiazepines. Generally these anxiolytics and sedatives should be considered as adjuvants to general anaesthesia, but not primarily as routine induction agents. The major reasons for this limitation are a high variability in drug response, a relatively slow onset of action and long-lasting residual effects. However, benzodiazepines have many important advantages (see Table 5) when used as intravenous inducing agents of general anaesthesia.