Inhaled nitrous oxide versus placebo as an analgesic and anxiolytic adjunct to peripheral intravenous cannulation

Nitrous oxide versus lidocaine versus no analgesic for in-office hysteroscopy: a randomised clinical trial

OBJECTIVE

To compare the effect of inhaled nitrous oxide (INO) on pain control during in-office hysteroscopy with 1% lidocaine paracervical infiltration and no analgesic.

DESIGN

Single-blind stratified randomised clinical trial with masked assessment by a third party.

SETTING

Department of Obstetrics and Gynaecology in a Spanish hospital.

POPULATION

Women who underwent hysteroscopy.

METHODS

Patients were stratified into three groups according to the purpose of the hysteroscopy (biopsy, polypectomy or tubal sterilisation) and then assigned to different treatment groups through a permuted-blocks randomisation within strata. Pain scale was provided by a gynaecologist totally blinded to procedures and treatments. Effects were assessed using a one-way analysis of variance following an intention-to-treat approach.

MAIN OUTCOME MEASURES

Visual analogue scale (VAS) from 0 to 100 mm.

RESULTS

A total of 314 women were included: 105 to INO, 104 to 1% lidocaine and 105 to no analgesic. Baseline characteristics were comparable. Mean VAS score after the procedure was 34.7 ± 25.8 mm, 36.1 ± 22.9 mm (P = 1.0) and 47.3 ± 28.2 mm (P = 0.001) for INO, 1% lidocaine and no analgesic, respectively. No adverse events were reported in 91 (86.7%) patients in the INO group compared with 79 (76%) in the 1%-lidocaine group (P = 0.04) and 85 (81%) in the no-analgesic group (P = 0.26).

CONCLUSION

INO was as effective as 1% lidocaine in pain control for in-office hysteroscopy and was better tolerated. The no-analgesic group presented the poorer results, so was the least recommended clinical option.

Subdermal nitrous oxide delivery increases skin microcirculation and random flap survival in rats

Random skin flaps are essential tools in reconstructive surgery. In this study, we investigated the effect of subdermal nitrous oxide (N₂O) application on random flap survival. In this experimental study, we used 21 female rats in three groups. In the N₂O and air groups, gases were administrated under the proposed dorsal flap areas daily for seven days. Following the treatment period, flaps were raised and inserted back into their place from the dorsal skin. In the control group, the flaps were elevated and inserted back to their place without any pretreatment. Calculation of necrotic flap areas, histological examination and microangiography was performed to evaluate the results 7 days after the flap surgery. The average of necrotic flap area in the N₂O, air and control group was 13.45%, 37.67% and 46.43%, respectively. (N₂O vs air p = .044; N₂O vs control p = .003). The average number of capillary formations identified in the histological analysis was 7.0 ± 1.58, 3.75 ± 2.36 and 4.4 ± 0.54 in the N₂O, air and control group, respectively. (N₂O vs air p = .017; N₂O vs control p = .037). The average number of capillary structures identified in the angiography images were 6.3 ± 1.52, 1.6 ± 1.15 and 1.3 ± 0.57 in the N₂O, air and control group, respectively. (N₂O vs air p = .04; N₂O vs control p = .02). We conclude that subdermal N₂O application increases random flap survival through an increase in the skin microcirculation and could be promising for future clinical applications.

Complications caused by nitrous oxide in dental sedation

The first clinical application of nitrous oxide (N₂O) was in 1844, by an American dentist named Horace Wells who used it to control pain during tooth extraction. Since then, N₂O has shared a 170-year history with modern dental anesthesia. N₂O, an odorless and colorless gas, is very appealing as a sedative owing to its anxiolytic, analgesic, and amnestic properties, rapid onset and recovery, and, in particular, needle-free application. Numerous studies have reported that N₂O can be used safely and effectively as a procedural sedation and analgesia (PSA) agent. However, N₂O can lead to the irreversible inactivation of vitamin B12, which is essential for humans; although rare, this can be fatal in some patients.

A 50-50% mixture of nitrous oxide-oxygen in transrectal ultrasound-guided prostate biopsy: A randomized and prospective clinical trial

Introduction

Transrectal ultrasound-guided biopsy (TUSPB) is the standard method of diagnosis for prostate cancer, and although it is well tolerated by some patients, it presents a discomfort rate of 65 to 90%, which may be associated with pain. For convenience, it is agreed that a method of analgesia and sedation is necessary. For this purpose, this study aimed to evaluate the impact of inhalation of a 50–50% N₂O-O₂ gas mixture on pain intensity in these patients.

Material and methods

Randomized, double-blinded clinical trial, conducted at Antônio Pedro University Hospital (Hospital Universitário Antônio Pedro), Niterói, RJ, Brazil, containing two groups of 42 patients: a control (C) group, which received 100% oxygen inhalation, and a nitrous oxide (NO) group, which received inhalation of the 50–50% N₂O-O₂ mixture, self-administered during TUSPB. The pain intensity and degree of satisfaction were evaluated through a visual analogue scale (VAS), as was the frequency of adverse events.

Results

Eighty-four patients were included in the study, with 42 in each group. The mean pain intensity was lower in the NO group than in the C group [2.52 (0–10) vs 5.95 (0–10), p < 0.001], and the degree of satisfaction was higher in the NO group than in the C group (8.14 vs. 4.69, p < 0.001). The adverse effects were somnolence, dizziness, nausea, vomiting, discomfort and euphoria without differences between the groups.

Conclusion

The 50–50% N₂O-O₂ mixture was effective in reducing pain intensity and increasing the degree of satisfaction in TUSPB, with tolerable side effects.

Luxations aiguës d'épaule : évaluation rétrospective aux urgences et proposition d'un protocole de sédation procédurale

Introduction : Les luxations d'épaule sont des pathologies fréquentes aux urgences, parmi les plus douloureuses et pour lesquelles il n'existe pas de recommandations spécifiques. Elles représentent 45 % de l'ensemble des luxations. L'objectif principal de cette étude était d'analyser la gestion de la douleur dans cette pathologie.

Matériel et méthodes : Nous avons conduit une étude observationnelle, monocentrique et rétrospective colligeant 238 patients ayant consulté aux urgences pour une luxation aiguë d'épaule (01/01/2012-30/04/2015). Les luxations réduites spontanément, les luxations sur prothèse et les luxations chroniques étaient exclues de l'étude.

Résultats : Les luxations aiguës d'épaule étaient majoritairement réduites aux urgences (90 %, IC95 % : [86-94]). Il s'agissait d'une pathologie hyperalgique (Echelle numérique médiane : 8/10, [EIC : 6-9]) touchant plutôt les sujets jeunes (âge médian : 48 ans, EIC : 28-73). Il existait une grande hétérogénéité dans la répartition des antalgiques utilisés, le mélange équimolaire d'oxygène et de protoxyde d'azote (MEOPA) était l'antalgique le plus prescrit (50 % (IC95 % : [42-55])), suivi par le paracétamol (25 %) et le néfopam (15 %). Dans le sous-groupe des luxations compliquées d'une fracture, le MEOPA était également le plus prescrit. La répartition des autres antalgiques était par ailleurs similaire. Enfin, la comparaison entre les deux équipes médicales (urgentiste vs orthopédiste) ne retrouvait aucune différence de prescription en dehors du midazolam davantage utilisé par les urgentistes (16 % vs 4 %, p=0,001).

Conclusion : Il existait une grande hétérogénéité des pratiques et une sous-utilisation d'antalgiques et d'hypnotiques malgré des douleurs importantes dès l'admission. Un chemin clinique visant à améliorer cette prise en charge est proposé afin d'homogénéiser les pratiques.

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.

Nitrous Oxide, From the Operating Room to the Emergency Department

Nitrous oxide is a gas inhalation agent that has a long history of administration in procedures requiring analgesia and sedation. Although use may be limited by patient condition, patient comorbidities, and appropriate scavenging equipment, nitrous is a proven and safe tool for use in many health care settings—from the dental office to the operating room to the emergency department.

Patients Presenting to the Emergency Department with Acute Pain: The Significant Role of Pain Catastrophizing and State Anxiety

OBJECTIVE

Pain is one of the most common reasons for emergency department (ED) visits. Given the significant association of psychological variables and pain experience, it is critical to examine the relation of such factors with ED pain reports. This study sought to analyze the association of reported pain intensity in ED with pain catastrophizing and state anxiety.

METHODS

One hundred participants presenting with a primary complaint of acute pain in an urban ED completed the study. The measures included a demographic survey with questions pertaining to pain intensity, type and duration of present pain, the Pain Catastrophizing Scale (PCS), and the State-Trait Anxiety Inventory-State Subscale (STAI-S).

RESULTS

Pain intensity was significantly and positively associated with pain catastrophizing and state anxiety. Follow-up PROCESS mediation analysis revealed a significant indirect effect of pain catastrophizing on the relationship between state anxiety and pain intensity.

CONCLUSIONS

The results suggest that it is important to assess the psychological distress due to anxiety and pain catastrophizing of patients presenting to EDs with acute pain. Setting-appropriate brief behavioral interventions in conjunction with pharmacological interventions could improve outcomes.

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.

Inhalation analgesia with nitrous oxide versus other analgesic techniques in hysteroscopic polypectomy: a pilot study

STUDY OBJECTIVE

To show the decrease in pain and better tolerance to inhalation analgesia with a 50% equimolar mixture of nitrogen protoxide and oxygen in hysteroscopic polypectomy compared with paracervical anesthesia and a control group.

DESIGN

One hundred six patients scheduled for office hysteroscopy and polypectomy were divided into the following 3 groups: the control group, the nitrous oxide group, and the paracervical infiltration group. Patients were assigned sequentially (Canadian Task Force classification II-1).

SETTING

The study took place in a hysteroscopy outpatient clinic under the supervision of a gynecologist and 2 nurses trained to cooperate in the trial.

PATIENTS

One hundred six women from Area III of Madrid Community, Spain, who had been diagnosed with endometrial polyps at a gynecology office and were scheduled for office hysteroscopy and polypectomy agreed to participate in the study.

INTERVENTIONS

Patients in group 1 (control group) received no treatment. Group 2 received inhaled nitrous oxide and group 3 paracervical infiltration with 1% lidocaine.

MEASUREMENTS AND MAIN RESULTS

Pain was assessed using the visual analog scale (0-10). Pain perceived by patients was lower in the nitrous Oxide group (mean: 3.55 ± 0.60, median: 3) versus the control group (mean: 5.49 ± 1.88, median: 6, p < .05) and the paracervical infiltration group (mean: 4.22 ± 1.73, median: 5). Tolerance to pain, assessed by the medical staff using qualitative variables, was bad for the control group, very good for the nitrous oxide group, and good for the paracervical infiltration group (p < .05). There were no complications in 82% of the patients in the nitrous oxide group, whereas in the paracervical infiltration group, there were complications in more than 50% of the patients. No severe complications occurred.

CONCLUSION

Nitrous oxide is a safe and effective analgesic technique for polipectomy office hysteroscopy compared with the paracervical infiltration and control groups.

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.

Applications of nitrous oxide for procedural sedation in the pediatric population

OBJECTIVE

The objective of this review was to provide a general descriptive account of the physical properties, end-organ effects, therapeutic applications, and delivery techniques of nitrous oxide (N2O) as used in the arena of procedural sedation.

DATA SOURCE

A computerized bibliographic search regarding the applications of nitrous for provision of sedation and analgesia during procedures with an emphasis on the pediatric population was performed.

RESULTS

The end-organ effects of N2O have been well described in the operating room setting. Aside from its effects on the central nervous system of sedation and analgesia, N2O may alter intracerebral dynamics and alter cerebral blood flow and intracranial pressure especially in patients with altered intracranial compliance. Effects on ventilation include a dose-related depression of ventilatory function and control of upper airway patency. These effects are generally limited in the absence of comorbid diseases and potentiated by other sedative and analgesic agents. The more clinically significant respiratory effect of N2O on ventilatory function is a dose-dependent depression of the ventilatory response to hypoxemia. Hemodynamic effects include a mild direct depressant effect on myocardial function, which in the absence of comorbid cardiac disease is generally compensated by stimulation of the sympathetic nervous system. Nitrous oxide may potentially aggravate pulmonary hypertension. Additional physiologic effects on neurologic and hematologic function may result in inactivation of the enzyme, methionine synthetase. Recent concern has also been raised regarding the potential effects of N2O on immune function and its relationship to perioperative surgical site infections. Given differences in the solubility, N2O will diffuse into and significantly expand gas-filled cavities. Chronic exposure of health care works to N2O is also a concern. Although there are limited data in the literature to clearly substantiate concerns regarding the reproductive toxicity of occupational exposure to N2O, appropriate scavenging and use of other techniques are mandatory. Nitrous oxide has been shown to be effective for a variety of minor surgical procedures such as venipuncture, intravenous cannula placement, lumbar puncture, bone marrow aspiration, laceration repair, dental care, and minor dermatologic procedures. It is generally as effective as midazolam, with several studies demonstrating it to be more effective. However, its utility is not as great in severely painful procedures such as fracture reduction. Demonstrated advantages to parenteral sedation include a more rapid onset and a shorter recovery time with the majority of patients preferring it to over other agents or agreeing to its use for subsequent procedures. The literature also suggests increased success rates with simple procedures such as intravenous cannula placement when compared with placebo. In general, life-threatening adverse events have not been reported. Most common adverse effects include dysphoria and vomiting. For more painful procedures, combination with another agent may be used, and in all cases, topical or infiltrative local anesthesia is recommended.

CONCLUSIONS

In general, N2O is a useful adjunct for procedural sedation. Given the variety of procedures performed in the pediatric patient, ongoing research is required to identify the most appropriate and effective use of this agent. This may be particularly relevant when evaluating its use for procedures associated with significant pain. In these scenarios, the combination of N2O with other agents needs to be evaluated. Given the potential for adverse effects, strict adherence to published guidelines regarding procedural sedation and monitoring is suggested.

Use of a combined oxygen/nitrous oxide/morphine chlorydrate protocol for analgesia in burned children requiring painful local care

PURPOSE

We present the results of the use of a protocol of inhalational oxygen/nitrous oxide mixtures associated with oral opioids on a prospective cohort of 33 children undergoing local care for acute but limited burned skin lesions.

METHODS

All the children were orally administered 0.4 mg/kg morphine chlorydrate, and nitrous oxide was administered as an equimolar mixture (50% N2O, 50% O2) via a face mask during the procedure. Pain and comfort of the patient were evaluated by the use of a validated behavioural score. After the end of the procedure, child and parent satisfactions were noted.

RESULTS

Mean age was 3 years 6 months (10 months-11 years). A successful detersion procedure was performed in all the cases. Behavioural score was 6 in 15 cases out of 33, comprising between 7 and 9 in 15 patients and 10 in three patients. Subjective satisfaction of pain management was noted in 16 out of 20 patients after the procedure. Subjective satisfaction of the parents was noted in all the cases.

DISCUSSION

Our study demonstrates that the use of a simple protocol of inhalational oxygen/nitrous oxide mixtures associated with oral opioids could be safe and effective. This association was well tolerated without any adverse effect.

Advances in understanding the actions of nitrous oxide

Nitrous oxide (N(2)O) has been used for well over 150 years in clinical dentistry for its analgesic and anxiolytic properties. This small and simple inorganic chemical molecule has indisputable effects of analgesia, anxiolysis, and anesthesia that are of great clinical interest. Recent studies have helped to clarify the analgesic mechanisms of N(2)O, but the mechanisms involved in its anxiolytic and anesthetic actions remain less clear. Findings to date indicate that the analgesic effect of N(2)O is opioid in nature, and, like morphine, may involve a myriad of neuromodulators in the spinal cord. The anxiolytic effect of N(2)O, on the other hand, resembles that of benzodiazepines and may be initiated at selected subunits of the gamma-aminobutyric acid type A (GABA(A)) receptor. Similarly, the anesthetic effect of N(2)O may involve actions at GABA(A) receptors and possibly at N-methyl-D-aspartate receptors as well. This article reviews the latest information on the proposed modes of action for these clinical effects of N(2)O.

Involvement of brain protein kinase C in nitrous oxide-induced antinociception in mice

Exposure of mice to the anesthetic gas nitrous oxide (N(2)O) produces a marked antinociceptive effect. Protein kinase C is a key regulatory enzyme that may be targeted by general anesthetics. However, a relationship between N(2)O-induced antinociception and protein kinase C has yet to be established. The present study was conducted to identify whether protein kinase C might influence N(2)O-induced antinociception in mice. Regular exposure (11 min) to N(2)O produced concentration-dependent antinociception in mice, as determined using the abdominal constriction test. N(2)O-induced antinociception was attenuated by i.c.v. pretreatment with phorbol 12,13-dibutyrate, a protein kinase C activator. This phorbol 12,13-dibutyrate antagonism of N(2)O-induced antinociception was reversed by i.c.v. pretreatment with calphostin C, a protein kinase C inhibitor. Long-term exposure (41 min in total, including 30 min prior to, and 11 min of analgesic testing) to 70% N(2)O produced reduced analgesic effects, compared with regular exposure to 70% N(2)O, thus indicating acute tolerance to N(2)O-induced antinociception. However, mice pretreated with calphostin C, chelerythrine, which is another protein kinase C inhibitor, and phorbol 12,13-dibutyrate, did not develop acute tolerance. Regarding activation of protein kinase C, regular exposure to 70% N(2)O did not increase protein kinase C within the membrane fraction of brain tissue, as determined by immunoblot analysis, but long-term exposure to 70% N(2)O did. The i.c.v. pretreatment with calphostin C and phorbol 12,13-dibutyrate prevented the increase in protein kinase C observed with long-term exposure to 70% N(2)O. These results suggest that brain protein kinase C negatively regulates the antinociceptive effect of N(2)O, and that activation of brain protein kinase C is related to the development of acute tolerance to N(2)O-induced antinociception in mice.

Nitrous oxide anxiolysis for elective cesarean section

STUDY OBJECTIVE

To determine if inhaled 40% nitrous oxide (N(2)O) via facemask is an effective anxiolytic in women undergoing elective cesarean section under spinal anesthesia.

STUDY DESIGN

Prospective, randomized, double-blinded study.

SETTING

Tertiary-care women's hospital.

PATIENTS

Sixty American Society of Anesthesiologists physical status I and II patients scheduled for elective cesarean section under spinal anesthesia.

INTERVENTIONS

Patients were randomized to 2 groups to receive either 100% O2 via facemask or 40% N2O in O2 via facemask.

MEASUREMENTS

Vital signs (blood pressure, heart rate, and oxygen saturation) and measured variables (visual analog scale [VAS] anxiety, VAS pain, and sedation scores) were obtained at specific periods during the procedure (preoperatively, entering the operating room, spinal injection, skin incision, uterine incision, delivery, and at the conclusion of the surgical procedure). In addition, surgical time and delivery time, mean dose and percentage of patients requiring ephedrine or phenylephrine boluses, the emesis rate, and Apgar scores were measured.

MAIN RESULTS

No differences were noted with respect to maternal mean blood pressure, heart rate, pulse-oximeter oxygen saturation, and sedation or VAS pain scores during the measured periods. No differences were noted in surgical and delivery times, mean dose, or percentage of patients who required ephedrine or phenylephrine to maintain maternal blood pressure, the emesis rate, or 1- and 5-minute Apgar scores. Mean anxiety scores for the N2O group were significantly lower at the time of spinal injection, skin incision, and uterine incision. Multivariate analysis of variance for high-anxiety patients (> or =50 VAS) revealed significantly lower VAS scores in the N2O group, compared with the O2 group again at spinal injection, skin incision, and uterine incision.

CONCLUSIONS

Inhaled 40% N2O via facemask provides effective anxiolysis in women undergoing elective cesarean section under spinal anesthesia in patients with high anxiety (> or =50 VAS) at the time of spinal injection, skin incision, and uterine incision.

Pain related to Optiva 2, Biovalve, and Venflon 2 intravenous catheters

Pain related to the insertion of intravenous catheters is a major issue for many patients. This study investigated differences in pain on insertion for three different catheters - Optiva 1, Biovalve and Venflon 2 - as assessed by 100 volunteers. Clinicians also assessed a variety of parameters related to their overall ease of use. This study demonstrates that Optiva 2 can offer significant benefits for both patient and clinician. Pain on insertion was significantly lower with Optiva 2 than with Venflon 2, but comparable with Biovalve. Ease of insertion and flashback were significantly better for Optiva 2 than for Venflon 2, but similar to Biovalve. For the parameters 'ease of catheter advancement' and 'overall ease of use', the operators rated Optiva 2 significantly better than Biovalve and Venflon 2.

Role of nitric-oxide synthase isoforms in nitrous oxide antinociception in mice

Exposure of mice to the anesthetic gas N2O evokes a prominent antinociceptive effect that is sensitive to antagonism by nonselective nitric-oxide synthase (NOS) inhibitors. The present study was conducted to identify whether a specific NOS isoform is implicated in N2O antinociception in mice. In the abdominal constriction test, exposure of mice to 25, 50, and 70% N2O resulted in a concentration-dependent antinociceptive effect that persisted for up to 6 min following removal of the mice from the N2O atmosphere into room air. This N2O antinociceptive effect was antagonized by pretreatment with S-methyl-l-thiocitrulline (SMTC) and higher doses of l-N5-(1-iminoethyl)-ornithine (l-NIO), which reportedly inhibit the neuronal and endothelial isoforms of NOS, respectively. Nevertheless, the N2O-induced antinociception was unaffected by pretreatment with low doses of either SMTC or l-NIO or by pretreatment with 2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine (AMT), which selectively inhibits inducible NOS. The s.c. pretreatment with SMTC and l-NIO reduced brain NOS activity in a dose-dependent manner, whereas AMT had no such effect. Moreover, in blood pressure experiments, SMTC increased SBP in dose-unrelated fashion, whereas l-NIO showed an appreciably weaker but dose-related increase in SBP. The i.c.v. pretreatment with SMTC also reduced N2O antinociception and brain NOS activity without increasing of SBP. These results suggest that it is the neuronal isoform of NOS that is involved in mediation of the antinociceptive effect of N2O in the mice.