Effect of nitrous oxide on propofol requirement during target-controlled infusion for oocyte retrieval

Pain Management during Ultrasound Guided Transvaginal Oocyte Retrieval - A Narrative Review

Transvaginal oocyte retrieval (TVOR), done for the purpose of assisted reproduction can instigate enormous pain and therefore requires adequate analgesia with the least adverse effects. As the procedure involves retrieving oocytes for in vitro fertilisation, the effect of the anaesthetic drugs on the oocyte quality should also be considered. This review focuses on the various modes of anaesthesia and the anaesthetic drugs which can be administered safely to provide effective analgesia in normal and in special conditions such as women with pre-existing comorbidities. Medline, Embase, PubMed and Cochrane electronic databases were searched according to modified Preferred Reporting Items for Systemic Reviews and Meta-Analyses guidelines. According to this review, conscious sedation appears to be the most preferred mode of anaesthesia in women undergoing TVOR owing to fewer adverse effects, faster recovery, better patient and specialist comfort and the least effect on oocyte quality and embryo development. Combining it with paracervical block resulted in lesser consumption of the anaesthetic drug, which may have a beneficial effect on the oocyte quality.

Anesthesia and analgesia for transvaginal oocyte retrieval. Should we recommend or avoid any anesthetic drug or technique?

PURPOSE OF REVIEW

The objective of this review is to analyze and summarize the current anesthetic methods used to alleviate pain and discomfort during transvaginal oocyte retrieval procedures (TORP), to try to reach practical recommendations, based on the evidence, which will translate into daily practice, the knowledge on the anesthetic management of patients scheduled for TORP.

RECENT FINDINGS

There is no strong evidence to recommend the avoidance of any technique or drug for TORP, including nitrous oxide or halogenated agents. Women should be offered any available technique. The evidence available up to date is not convincing enough to recommend avoiding any anesthetic technique in terms of pregnancy and birth rates.

SUMMARY

TORP is painful for women and different techniques may be used for pain relief in day case surgery. The other important outcome to consider is the pregnancy rate, and any anesthetic technique or drug which would improve this pregnancy rate should be recommended. Conscious sedation and general anesthesia proved to be well tolerated for woman and the oocytes, despite the use of propofol, opioids, benzodiacepines, nitrous oxide, or other drugs. Spinal anesthesia and paracervical block are also acceptable options, and can be combined with conscious sedation. Nevertheless, more studies are needed to find out the ideal drug or technique combination for the woman and the oocyte.

Efficacy of bispectral index monitoring for prevention of anestheticawareness and complications during oocyte pick-up procedure

Background/aim: This study was planned by considering that the use of bispectral index (BIS) monitoring ensures sufficient depth of anesthesia and avoids anesthetic awareness and patient movement in the oocyte pick-up (OPU) procedure.Materials and methods: Ninety-eight patients undergoing OPU were randomly divided into 2 groups as the control group (n = 48) and BIS group (n = 50). After propofol and remifentanil induction, the control group was given additional propofol according to reaction response, while the BIS group was given propofol at BIS values of 60 and above with the aim that BIS values be 40?60. Total procedure time, recovery time, patient movement, additional propofol consumption, total number of oocytes, and awareness during anesthesia were recorded. Results: Demographic data were similar in the two groups (P > 0.05 for all). The recovery time in the BIS group was significantly shorter compared to the control group (P < 0.001) while additional propofol consumption was found to be significantly lower (P < 0.001). Baseline BIS values fell compared to all other times after induction significantly (P < 0.001). No patient had anesthesia awareness.Conclusion: During the OPU procedure BIS monitoring is considered to prevent anesthesia awareness, intraoperative movement, and complications caused by insufficient anesthetic use as it ensures optimal doses of anesthetic agents used and early recovery.

Nitrous oxide-based vs. nitrous oxide-free general anaesthesia and accidental awareness in surgical patients: an abridged Cochrane systematic review

Accidental awareness during general anaesthesia can arise from a failure to deliver sufficient anaesthetic agent, or from a patient's resistance to an expected sufficient dose of such an agent. Awareness is 'explicit' if the patient is subsequently able to recall the event. We conducted a systematic review into the effect of nitrous oxide used as part of a general anaesthetic on the risk of accidental awareness in people over the age of five years undergoing general anaesthesia for surgery. We included 15 randomised controlled trials, 14 of which, representing a total of 3439 participants, were included in our primary analysis of the frequency of accidental awareness events. The awareness incidence rate was rare within these studies, and all were considered underpowered with respect to this outcome. The risk of bias across all studies was judged to be high, and 76% of studies failed adequately to conceal participant allocation. We considered the available evidence to be of very poor quality. There were a total of three accidental awareness events reported in two studies, one of which reported that the awareness was the result of a kink in a propofol intravenous line. There were insufficient data to conduct a meta- or sub-group analysis and there was insufficient evidence to draw outcome-related conclusions. We can, however, recommend that future studies focus on potentially high-risk groups such as obstetric or cardiac surgery patients, or those receiving neuromuscular blocking drugs or total intravenous anaesthesia.

Nitrous oxide-based versus nitrous oxide-free general anaesthesia and accidental awareness during general anaesthesia in surgical patients

BACKGROUND

Accidental awareness during general anaesthesia (AAGA) is when a patient unintentionally becomes conscious during a procedure performed with general anaesthesia and subsequently has explicit recall of this event. Incidence estimates for AAGA vary, with the most common estimate being one to two cases per 1000 general anaesthetics. Evidence linking nitrous oxide use and an increased risk of AAGA has come from observational studies data but the literature is contradictory, with some studies finding a protective effect of nitrous oxide.

OBJECTIVES

To assess the effect of general anaesthesia including nitrous oxide on the risk of AAGA in patients aged five years and over.

SEARCH METHODS

We searched the following databases: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and trial registers ((www.clinicaltrials.gov), the WHO International Clinical Trials Registry Platform (www.who.int/ictrp/network/en/) and Current Controlled Trials (www.isrctn.com/)) for eligible studies on December 9 2015. In addition, we conducted forward and backward citation searching using key identified papers.

SELECTION CRITERIA

We considered all randomized controlled trials (RCTs), including quasi-randomized studies and cluster-randomized studies, of participants aged five years or older receiving general anaesthesia for any type of surgery.We included trials in which participants receiving general anaesthesia that included nitrous oxide for maintenance at a concentration of at least 30% were compared with participants receiving no nitrous oxide during general anaesthesia. The intervention group must have received nitrous oxide in conjunction with an additional anaesthetic. We excluded studies where the depth of anaesthesia differed between the study arms. For inclusion in the review, studies needed to state in their methods that they planned to assess AAGA. We defined this as when a patient becomes conscious during a procedure performed with general anaesthesia and subsequently has explicit recall of this event.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane to identify studies. We extracted data and conducted 'Risk of bias' assessment using the Covidence database.

MAIN RESULTS

We included 15 studies. The total number of participants included in the analyses was 3520. Most studies were small with fewer than 120 participants, although two larger studies with 2012 and 671 participants were included. There was considerable variation in many of the study characteristics, including the anaesthetics used. The concentrations of nitrous oxide varied between 50% and 70%, and half of the studies used clinical signs and haemodynamic changes to monitor depth of anaesthesia.As it was not possible to blind the anaesthetist to the anaesthetic used, we rated all studies at high risk of performance bias and we therefore downgraded the quality of evidence by one level for risk of bias using the GRADE approach. Other types of bias were generally low, or were rated unclear due to missing information.No studies were designed to measure AAGA as the primary outcome, and were therefore statistically underpowered to answer this review question. Despite the inclusion of 3520 participants, only three awareness events were reported by two studies. In one study the event was due to technical failure. Due to the rarity of the events, we did not consider it appropriate to pool the data, and we therefore downgraded the quality of evidence by a further level for imprecision using GRADE.

AUTHORS' CONCLUSIONS

It is not possible to draw any conclusions from this review. The included studies were mainly small (fewer than 120 participants) and there were limited estimates of effect, with only two studies reporting any events. We cannot therefore determine whether the use of nitrous oxide in general anaesthesia increases, decreases or has no effect on the risk of accidental awareness.

Does Spinal Analgesia have Advantage over General Anesthesia for Achieving Success in In-Vitro Fertilization?

OBJECTIVE

Because of high psychological burden and considerable costs of in-vitro fertilization, it is greatly important to identify all factors that may influence its results. In this study, general anesthesia and spinal analgesia used for oocyte retrieval were compared in terms of success in treating infertility among couples who had undergone in-vitro fertilization at an infertility center in Tehran, Iran.

METHODS

This cohort study that was based on analysis of patient records at Mirza Kochak Khan Hospital, Tehran University of Medical Sciences, in 2008-2009. In this study, the status of chemical pregnancy among those who experienced general anesthesia or spinal anesthesia for in-vitro fertilization for the first time were compared, and the possible effects of clinical and laboratory factors using logistic regression models were considered.

RESULTS

Considering the number of transferred embryos, underlying cause of infertility and fetus grade, it was found that practicing spinal anesthesia is significantly related to increased chance of chemical pregnancy (adjusted Odds Ratio=2.07; 95% CI: 1.02,4.20; p=0.043).

CONCLUSION

According to analysis of recorded data in an infertility treatment center in Iran, it is recommended to use spinal anesthesia instead of general anesthesia for oocyte retrieval to achieve successful in-vitro fertilization outcome. This can be studied and investigated further via a proper multicentric study in the country.

A comparison of three different target-controlled remifentanil infusion rates during target-controlled propofol infusion for oocyte retrieval

OBJECTIVE

To evaluate the effects of three different target-controlled remifentanil infusion rates during target-controlled propofol infusion on hemodynamic parameters, pain, sedation, and recovery score during oocyte retrieval.

METHODS

Sixty-nine women were scheduled for oocyte retrieval. Target-controlled propofol infusion at an effect-site concentration of 1.5 μg/mL was instituted. The patients were randomly allocated to receive remifentanil at an effect-site concentration of either 1.5 (group I, n = 23), 2 (group II, n = 23) or 2.5 ng/mL (group III, n = 23). Hemodynamic variables, sedation, pain, the Aldrete recovery score, and side effects were recorded.

RESULTS

Hemodynamic variables, sedation and pain scores and the number of patients with the maximum Aldrete recovery score 10 min after the procedure were comparable among the groups. The number of patients in group III with the maximum Aldrete recovery score 5 min after the procedure was significantly lower than that in groups I and II. One patient in group II and one patient in group III suffered from nausea.

CONCLUSION

Similar pain-free conscious sedation conditions without significant changes in hemodynamic parameters were provided by all three protocols. However, target controlled infusion of remifentanil at 1.5 or 2 ng/mL proved superior at providing early recovery compared to 2.5 ng/mL.