Nitrous oxide anxiolysis for elective cesarean section

Relationship between COMT Gene Polymorphism, Anxiety, and Pain Perception during Labour

BACKGROUND

The COMT gene polymorphism is associated with neurological and psychiatric disorders and pain perception. The present study investigates the existence of anxiety and pain perception in relation to the COMT (catechol-O-methyltransferase) gene polymorphism in labouring women (during "natural" childbirth) with or without inhaled analgesia.

METHODS

A total of 181 women who chose vaginal birth were enrolled in this study. To present the difference in pain perception, the parturients were divided into one group (n = 90) that chose labour analgesia with inhaled nitrous oxide (50% nitrous oxide and 50% oxygen) and one group (n = 91) without analgesia. The blood samples were taken during the pregnancy as a part of routine pregnancy controls in the hospital. The COMT gene polymorphism was detected with the PCR technique. The pain perception of parturients was self-evaluated two times according to the VAS (Visual Analogue Scale), and anxiety as a personality trait was determined with the STAI-T (State Trait Anxiety Inventory). Pain perception as well as anxiety were compared according to COMT genotypes.

RESULTS

In the 181 pregnant women, there were 40 women (22%) of wild homozygotes (GG) of COMT, 95 women (53%) of mutant heterozygotes (GA), and 46 women (25%) of mutant homozygotes (AA). A negative association of pain perception with the GA (mutant heterozygote) polymorphism of the COMT gene versus the wild-type (GG polymorphism) was observed. The GA polymorphism of the COMT gene was associated with 0.46 units lower pain perception compared to the wild type (GG). The anxiety trait score in group AA was lower than in groups GA and GG. The difference reached statistical significance only when comparing AA versus GA (p > 0.042). Analgesic efficacy of nitrous oxide was noticed in 22% of labouring women who reported moderate pain (VAS score 4-7).

CONCLUSIONS

The COMT gene polymorphism was associated with pain perception and anxiety among parturients. The COMT gene polymorphism GA was associated with negative pain perception among labouring women. Nitrous oxide showed statistical significance in anxiolytic efficacy during labour in women with mild anxiety as a personality trait. Anxiolytic efficacy of nitrous oxide has shown better efficacy in parturients with the COMT gene polymorphism AA.

European Society of Anaesthesiology Task Force on Nitrous Oxide: a narrative review of its role in clinical practice

Nitrous oxide (N₂O) is one of the oldest drugs still in use in medicine. Despite its superior pharmacokinetic properties, controversy remains over its continued use in clinical practice, reflecting in part significant improvements in the pharmacology of other anaesthetic agents and developing awareness of its shortcomings. This narrative review describes current knowledge regarding the clinical use of N₂O based on a systematic and critical analysis of the available scientific literature. The pharmacological properties of N₂O are reviewed in detail along with current evidence for the indications and contraindications of this drug in specific settings, both in perioperative care and in procedural sedation. Novel potential applications for N₂O for the prevention or treatment of chronic pain and depression are also discussed. In view of the available evidence, we recommend that the supply of N₂O in hospitals be maintained while encouraging its economic delivery using modern low flow delivery systems. Future research into its potential novel applications in prevention or treatment of chronic conditions should be pursued to better identify its role place in the developing era of precision medicine.

Nitrous Oxide Utility in Labor and Birth: A Multipurpose Modality

The use of nitrous oxide (N2O) for labor and birth has very recently emerged as a viable modality in the United States, despite a long history of use in Canada and Europe. Usually associated with dental procedures, there are significant differences between dental and parturition utility, efficacy, and staff exposure. In addition to using it for pain relief and anxiolysis, those centers utilizing it have noted it to be multipurpose and useful for such situations as: external cephalic version, manual removal of placenta, intravenous starts, during placement of urinary catheters and intracervical Foley bulbs. Nitrous oxide has proven to be especially helpful for repair of lacerations under local anesthesia and is a multiuse modality that should be available to women in all birth settings. This article explores the history of N2O use, provides a comparison of obstetrical use to use in the dental industry, examines the contraindications to, and implications for usage, and discusses logistical points of consideration for clinicians working with women using N2O for labor and birth.

Predictors for Moderate to Severe Acute Postoperative Pain after Cesarean Section

Background. Moderate to severe postoperative pain affects performance of daily activities and it contributes to persistent postoperative pain. In patients submitted to cesarean section, this pain can also interfere with women's ability to care for their babies, to effectively breastfeed, and to satisfactorily interact with their children. Factors influencing the pain perception during the immediate postoperative period have not been widely pursued. Objective. To investigate the incidence and predicting factors of postoperative pain after cesarean section. Methods. A prospective longitudinal study with 1,062 women submitted to cesarean section. We collected sociodemographic, clinical, surgical, and health behavior data. We used the 11-point Numerical Pain and the Hospital Anxiety and Depression Scales. We performed logistic analysis to identify predictors of moderate to severe postoperative pain. Results. The incidence of moderate-severe postoperative pain was 78.4% (CI: 95%: 75.9%–80.8%). The preoperative anxiety (OR = 1.60; CI 95%: 1.22–2.30) and intrathecal morphine with fentanyl (OR = 0,23; CI 95%: 0.08–0.66) were significantly associated with moderate-severe postoperative pain report. Conclusion. The preoperative anxiety increases the risk of moderate-severe postoperative pain in women submitted to cesarean section. The intrathecal morphine with fentanyl added to bupivacaine was a protective factor against this pain.

Preoperative anxiety in patients selecting either general or regional anesthesia for elective cesarean section

Background and Aims:

We aimed to measure the frequency of preoperative anxiety in patients undergoing elective cesarean section (CS) and its impact on patients decision regarding the choice of anesthesia.

Material and Methods:

This cross-sectional study included 154 consecutive patients, who were scheduled for elective CS. Visual analog scale (VAS) for anxiety was the study tool, and VAS ≥50 was considered as significant anxiety. Enrolled patients were interviewed by the primary investigator the day before the surgery and their VAS score and choice of anesthesia technique either general anesthesia (GA) or regional anesthesia (RA) were recorded. Additional data included demographics, parity, educational status, previous anesthesia experience and source of information.

Results:

Preoperative anxiety (VAS ≥ 50) was seen in 72.7% of patients, which was significantly higher (P < 0.005) in patients selecting GA (97.18%, n = 71/154) as compared to those selecting RA (51.81%, n = 83/154) for elective CS. Statistically significant association of anxiety (P < 0.005) was seen with age <25 years, nulli and primiparous, higher education status, previous anesthesia experience and source of information from nonanesthetist.

Conclusion:

Patients scheduled for elective CS were found to have high frequency of anxiety (72.7%), and GA was observed to be the choice of anesthesia technique in anxious patients.

Nitrous oxide analgesia for bone marrow aspiration and biopsy - A randomized, controlled and patient blinded study

Background and aims Bone marrow aspiration and/or biopsy (BMAB), performed under local anaesthesia in adults, is a common and often painful procedure. Anxiety is known to intensify pain during the procedure. Nitrous oxide (N2O), known for its sedative and analgesic benefit in various short medical procedures and labour pain, could be advantageous also for pain relief during bone marrow examination. N2O acts rapidly and is eliminated in a couple of minutes once the inhalation is stopped, and occasional side effects (e.g. dizziness and nausea) are mild. The aim of this study was to compare the analgesic effects of inhaled 50% mixture of nitrous oxide and oxygen to 50% oxygen during bone marrow examination. Methods In this randomized, controlled, patient and observer blinded study patients received either 50% mixture of nitrous oxide and oxygen or 50% mixture of oxygen in air during bone marrow examination, in addition to local analgesia. Both patient groups comprised 35 adult patients. Pre-procedural anxiety and procedural pain were rated on the Numeral Rating Scale (NRS 0‒10). Cognitive function was measured before and 30 min after the procedure. Possible side effects were recorded. A telephone interview was performed 24 h later. Results There were no statistically significant differences in pain scores of the procedural steps (median NRS ranging 3.0‒4.0) between the study groups. High pain scores of 8‒10 comprised 0% vs. 8.6% of the scores during infiltration, 2.9% vs. 5.7% during puncture, 11.4% vs. 14.3% during aspiration and 2.9% vs. 2.9% during biopsy in N2O and 50% O2 groups, respectively (NS). Pre-procedural anxiety (median NRS 3.5 in both groups), measured in the outpatient clinic just prior to procedure, correlated with pain intensity during bone marrow aspiration (P = 0.045). There were no significant differences between side effects. During the BMAB four patients (3 in N2O group, 1 in 50% O2 group) reported dizziness and one patient in the N2O group reported nausea. Gas inhalation did not affect the cognitive function of the participants. In both groups the majority (>80%) of the patients was satisfied with the inhalation technique. During the 24 h interview, most of the participants were pain free and they did not report any serious adverse effects. Conclusions In spite of similar moderate to strong procedural pain in both groups and no benefit of N2O, most patients were satisfied with the inhalational techniques. We assume that the bedside presence of an anaesthesiologist and the distraction caused by the inhalational arrangements introduced positive context-sensitive therapeutic effect independent of the gas used. Pre-procedural anxiety predicted pain associated with bone marrow aspiration. Implications Inhaled 50% nitrous oxide was not an effective analgesic during bone marrow examination in our unselected outpatient population. Further studies should concentrate on its use with patients predicted to be at increased risk of suffering intense pain during the procedure, such as very anxious patients or those who have a painful history of previous bone marrow examinations.

Nitrous oxide effect on relieving anxiety and pain in parturients under spinal anesthesia for caesarean section

Background:

Anxiety is an unpleasant experience that may have adverse effects on the process of anesthesia, cesarean delivery, recovery period and postoperative pain. Anxiety can also affect maternal satisfaction of the medical cares that provided by the medical team.

Objectives:

To compare the effects of inhalational 50% nitrous oxide (N₂O) with oxygen on reducing anxiety and pain in parturients who have undergone caesarean section under spinal anesthesia.

Patients and Methods:

In this double-blind clinical trial, 56 primigravid parturients were randomly assigned into two groups according to the operating list schedule. The experimental group received inhalational 50% N₂O three minutes before spinal anesthesia to the end of delivery. The control group received only oxygen. Flow meters were covered by a dark shield and monitored by an experienced nurse anesthetist. Pain and anxiety of patients were measured using visual analogue scale (VAS) by another nurse who was neither involved in the anesthetic process nor aware of the participants' allocation and inhalation agents. Data regarding sedation level, ephedrine use, nausea, vomiting, and neonate Apgar score were recorded as well.

Results:

Overall mean ± SD of anxiety VAS scores was 1.77 ± 1.5 in the experimental group and 3.12 ± 1.73 in the control groups (P = 0.003). The mean ± SD of pain VAS scores of the experimental and control groups were 0.82 ± 1.5 and 1.64 ± 1.45, respectively (P = 0.042). No significant differences were seen regarding blood oxygen saturation, neonate Apgar scores, total used ephedrine, operation time, delivery time, nausea, and vomiting between the two studied groups.

Conclusions:

Inhalation of 50% N₂O can significantly decrease anxiety (without clinically significant side effects) compared with O₂ inhalation in parturients who have undergone caesarean section under spinal anesthesia.