Inhaled patient-administered nitrous oxide/oxygen mixture does not impair driving ability when used as analgesia during screening flexible sigmoidoscopy

Is whole-colon investigation by colonoscopy, computerised tomography colonography or barium enema necessary for all patients with colorectal cancer symptoms, and for which patients would flexible sigmoidoscopy suffice? A retrospective cohort study

BACKGROUND

For patients referred to hospital with suspected colorectal cancer (CRC), it is current standard clinical practice to conduct an examination of the whole colon and rectum. However, studies have shown that an examination of the distal colorectum using flexible sigmoidoscopy (FS) can be a safe and clinically effective investigation for some patients. These findings require validation in a multicentre study.

OBJECTIVES

To investigate the links between patient symptoms at presentation and CRC risk by subsite, and to provide evidence of whether or not FS is an effective alternative to whole-colon investigation (WCI) in patients whose symptoms do not suggest proximal or obstructive disease.

DESIGN

A multicentre retrospective study using data collected prospectively from two randomised controlled trials. Additional data were collected from trial diagnostic procedure reports and hospital records. CRC diagnoses within 3 years of referral were sourced from hospital records and national cancer registries via the Health and Social Care Information Centre.

SETTING

Participants were recruited to the two randomised controlled trials from 21 NHS hospitals in England between 2004 and 2007.

PARTICIPANTS

Men and women aged ≥ 55 years referred to secondary care for the investigation of symptoms suggestive of CRC.

MAIN OUTCOME MEASURE

Diagnostic yield of CRC at distal (to the splenic flexure) and proximal subsites by symptoms/clinical signs at presentation.

RESULTS

The data set for analysis comprised 7380 patients, of whom 59% were women (median age 69 years, interquartile range 62-76 years). Change in bowel habit (CIBH) was the most frequently presenting symptom (73%), followed by rectal bleeding (38%) and abdominal pain (29%); 26% of patients had anaemia. CRC was diagnosed in 551 patients (7.5%): 424 (77%) patients with distal CRC, 122 (22%) patients with cancer proximal to the descending colon and five patients with both proximal and distal CRC. Proximal cancer was diagnosed in 96 out of 2021 (4.8%) patients with anaemia and/or an abdominal mass. The yield of proximal cancer in patients without anaemia or an abdominal mass who presented with rectal bleeding with or without a CIBH or with a CIBH to looser and/or more frequent stools as a single symptom was low (0.5%). These low-risk groups for proximal cancer accounted for 41% (3032/7380) of the cohort; only three proximal cancers were diagnosed in 814 low-risk patients examined by FS (diagnostic yield 0.4%).

LIMITATIONS

A limitation to this study is that changes to practice since the trial ended, such as new referral guidelines and improvements in endoscopy quality, potentially weaken the generalisability of our findings.

CONCLUSIONS

Symptom profiles can be used to determine whether or not WCI is necessary. Most proximal cancers were diagnosed in patients who presented with anaemia and/or an abdominal mass. In patients without anaemia or an abdominal mass, proximal cancer diagnoses were rare in those with rectal bleeding with or without a CIBH or with a CIBH to looser and/or more frequent stools as a single symptom. FS alone should be a safe and clinically effective investigation in these patients. A cost-effectiveness analysis of symptom-based tailoring of diagnostic investigations for CRC is recommended.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN95152621.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 21, No. 66. See the NIHR Journals Library website for further project information.

Clinical comparative study on Nitrous Oxide inhalation versus intravenous propofol and Midazolam sedation in Transnasal Gastroscopy

Objective:

To investigate the Clinical practice value of nitrous oxide inhalation and intravenous propofol and midazolam sedation in transnasal gastroscopy.

Method:

From December 2012 to April 2014, two hundred patients receiving painless transnasal gastroscopy on a voluntary basis were selected in Endoscopy center, The First People’s Hospital of GuiYang. Patients were divided into two groups: Group-1 consisted of one hundred patients sedated by nitrous oxide inhalation and Group-2 consisted of one hundred patients sedated by intravenous propofol and midazolam. Patients were then examined by transnasal gastroscopy. Patient blood pressure, heart rate, pulse rate and oxygen saturation before, during and after gastroscopy were recorded for both groups. The duration of the gastroscopy and the time of awakening were also recorded. After examination, the patients were asked to assess the level of discomfort experiences during the gastroscopy procedure.

Results:

All patients successfully underwent the transnasal gastroscopy. There were 57 males and 43 females in the nitrous oxide inhalation group with an average age of 43.11±8.27 years. The average duration of examination and time of awaking in the nitrous oxide inhalation group was of 152.7±9.80 secs and 50±7.89 secs respectively. For the intravenous propofol and midazolam sedation group, there were 53 males and 47 females with an average age of 41.26±7.98 years. The average duration of examination and time of awaking in the intravenous propofol and midazolam sedation group was of 149.07±10.25 seconds and 390±20.89^# seconds respectively. The two groups showed no significant difference in the duration of examination. There was no difference in the age or sex. The former had a less significant impact on heart rate, oxygen saturation and blood pressure, while the intravenous propofol and midazolam sedation decreased blood pressure dramatically and this effect persisted after examination.

Conclusion:

Nitrous oxide inhalation has higher safety and tolerance with a brighter application prospect for transnasal gastroscopy.

Colonoscopy quality with Entonox®vs intravenous conscious sedation: 18608 colonoscopy retrospective study

AIM

To compare colonoscopy quality with nitrous oxide gas (Entonox®) against intravenous conscious sedation using midazolam plus opioid.

METHODS

A retrospective analysis was performed on a prospectively held database of 18608 colonoscopies carried out in Lothian health board hospitals between July 2013 and January 2016. The quality of colonoscopies performed with Entonox was compared to intravenous conscious sedation (abbreviated in this article as IVM). Furthermore, the quality of colonoscopies performed with an unmedicated group was compared to IVM. The study used the following key markers of colonoscopy quality: (1) patient comfort scores; (2) caecal intubation rates (CIRs); and (3) polyp detection rates (PDRs). We used binary logistic regression to model the data.

RESULTS

There was no difference in the rate of moderate-to-extreme discomfort between the Entonox and IVM groups (17.9% vs 18.8%; OR = 1.06, 95%CI: 0.95-1.18, P = 0.27). Patients in the unmedicated group were less likely to experience moderate-to-extreme discomfort than those in the IVM group (11.4% vs 18.8%; OR = 0.71, 95%CI: 0.60-0.83, P < 0.001). There was no difference in caecal intubation between the Entonox and IVM groups (94.4% vs 93.7%; OR = 1.08, 95%CI: 0.92-1.28, P = 0.34). There was no difference in caecal intubation between the unmedicated and IVM groups (94.2% vs 93.7%; OR = 0.98, 95%CI: 0.79-1.22, P = 0.87). Polyp detection in the Entonox group was not different from IVM group (35.0% vs 33.1%; OR = 1.01, 95%CI: 0.93-1.10, P = 0.79). Polyp detection in the unmedicated group was not significantly different from the IVM group (37.4% vs 33.1%; OR = 0.97, 95%CI: 0.87-1.08, P = 0.60).

CONCLUSION

The use of Entonox was not associated with lower colonoscopy quality when compared to intravenous conscious sedation using midazolam plus opioid.

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.

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.

Entonox® inhalation to reduce pain in common diagnostic and therapeutic outpatient urological procedures: a review of the evidence

INTRODUCTION

Entonox(®) (50% nitrous oxide and 50% oxygen; BOC Healthcare, Manchester, UK) is an analgesic and anxiolytic agent that is used to successfully reduce pain and anxiety during dental, paediatric and emergency department procedures. In this article we review the application and efficacy of Entonox(®) in painful local anaesthesia urological procedures by performing a systematic review of the literature.

METHODS

A MEDLINE(®) search was performed using the terms 'nitrous oxide', 'Entonox', 'prostate biopsy', 'flexible cystoscopy' and 'extracorporeal shock wave lithotripsy'. English language publications of randomised studies were identified and reviewed.

RESULTS

The search yielded five randomised studies that investigated the clinical efficacy of Entonox(®) as an analgesic for day case urological procedures. Three randomised controlled trials (RCTs) investigated Entonox(®) in transrectal ultrasonography guided prostate biopsy. All three reported significant reductions in pain score in the Entonox(®) versus control groups. One RCT reported significant reduction in pain during male flexible cystoscopy in the Entonox(®) group compared with the control group. One RCT, which examined the use of Entonox(®) during extracorporeal shock wave lithotripsy, found its use significantly decreased the pain score compared with the control group and this was comparable to intravenous pethidine.

CONCLUSIONS

Evidence from varied adult and paediatric procedures has shown Entonox(®) to be an effective, safe and patient acceptable form of analgesia. All published studies of its use in urological day case procedures have found it to significantly reduce procedural pain. There is huge potential to use this cheap, safe, effective analgesic in our current practice.

Nitrous oxide for analgesia in colonoscopy without sedation

BACKGROUND

Colonoscopy is associated with pain and discomfort, and intravenous analgesics and sedatives are widely used. There are several disadvantages regarding this practice, including risk of complications, resources demanded, and amnesia after sedation. In spite of promising results in previous studies, nitrous oxide is rarely used at endoscopy centers around the world.

OBJECTIVE

To investigate the efficiency of nitrous oxide versus placebo as an analgesic during colonoscopy without sedation.

DESIGN

A double-blind, randomized, placebo-controlled trial.

SETTING

The endoscopy unit at Oslo University Hospital Rikshospitalet, Oslo, Norway, between June 2006 and May 2008.

PATIENTS

This study involved patients undergoing elective colonoscopy.

INTERVENTION

Patients inhaled nitrous oxide or placebo on demand.

MAIN OUTCOME MEASUREMENTS

The participants filled in a questionnaire regarding their experiences with the examination. Pain was graded from 1 (no pain) to 4 (severe pain).

RESULTS

We recruited 199 patients. We randomized 97 patients to the nitrous oxide group and 102 to the control group. The groups were comparable regarding demographic factors. Median patient-reported pain was 2 in both the nitrous oxide group and the control group (interquartile range 2-3 in both groups). Additional sedatives and analgesics were given equally often and in similar doses in both groups. No side effects related to administration of nitrous oxide were reported.

LIMITATIONS

The questionnaire was returned by 76% of the patients. The study gas was given on demand, not continuously.

CONCLUSION

Nitrous oxide given intermittently is not an effective substitution for intravenous on-demand sedation and analgesics in the setting of colonoscopy without sedation.

Nitrous oxide for colonoscopy

BACKGROUND

Colonoscopy is the gold standard investigation for large bowel disease. With the increase in demand, pressure is on clinics to shorten lengths of time per procedure in addition to maintaining high levels of patient safety. Analgesia has always been the mainstay of adequate pain relief, but it leads to prolonged recovery and lengths of hospital stay, in addition to increased risk of cardio-respiratory side effects. N2O/O2 mixtures have been used for its effective analgesic effect and short half life and provides an alternative method of sedation for colonoscopy procedures.

OBJECTIVES

The primary objective was to compare the overall effectiveness of nitrous oxide mixtures to other types of pain relief used during colonoscopy procedures to provide adequate pain/discomfort relief.The secondary objective was to compare between nitrous oxide and other types of pain relief with respect to hospitalisation/recovery time, side effects, patients and endoscopists satisfaction, and colonoscopy completion rates.

SEARCH STRATEGY

The following electronic databases were searched: Cochrane Central Register of Controlled Trials (CENTRAL) on The Cochrane Library, MEDLINE (1966- present), EMBASE (1980 - present), and the Internet (Google Scholar).

SELECTION CRITERIA

Randomised controlled trials which compared nitrous oxide to placebo or active comparators for patients undergoing elective colonoscopic procedures. Patients with known underlying causes of pain/discomfort were excluded. 

DATA COLLECTION AND ANALYSIS

Seven randomised trials were included. Each trial compared a nitrous oxide/oxygen mixture to a placebo or sedation +- other analgesic drugs on patients undergoing elective colonoscopic procedures. The results of these studies were analysed and discussed.

MAIN RESULTS

There were a total of 547 patients included.There were 257 patients randomised to receive the N2O/O2 mixture (7 studies), while 225 patients received some form of sedation with or without other analgesia (6 studies), and 65 patients received a placebo (3 studies).Four studies showed that N2O/O2 is as good in controlling pain/discomfort as conventional methods, while one showed sedation was better and another study showed N2O/O2 was better.Six of the studies showed that N2O/O2 groups had quicker recovery times and shorter lengths of hospital stays while one study showed that there was no difference between the two groups.Two studies showed that N2O/O2 was safer while one reported that sedation was safer.

AUTHORS' CONCLUSIONS

Nitrous oxide is as efficient and safer than various pain relief methods used during colonoscopy procedures, but further trials are necessary.

Systematic review: the use of nitrous oxide gas for lower gastrointestinal endoscopy

BACKGROUND

Nitrous oxide gas (N(2)O) has been proposed as an alternative to intravenous (i.v.) analgesia in patients undergoing lower gastrointestinal endoscopy.

AIM

To perform a systematic review of randomized studies where N(2)O was compared against control in patients undergoing either flexible sigmoidoscopy or colonoscopy.

METHODS

Electronic databases were searched; reference lists were checked and letters were sent to authors requesting data. Methodological quality was assessed. Data were tabulated on the duration and difficulty of the procedure, quality of sedation and speed of patient recovery.

RESULTS

A total of 11 studies were identified containing 623 patients. No differences were seen between groups for duration, difficulty of procedure or complications. Patient-reported pain was similar for N(2)O when undergoing flexible sigmoidoscopy vs. no sedation and when undergoing colonoscopy vs. i.v. sedation. Differences in delivery of N(2)O were identified. In all studies, N(2)O was associated with a more rapid recovery than i.v. sedation.

CONCLUSION

For patients undergoing colonoscopy, N(2)O provides comparable analgesia to i.v. sedation. The rapid psychomotor recovery with N(2)O enables quicker patient discharge and removes the need for a patient to be chaperoned. Benefit was not seen from N(2)O in patients undergoing flexible sigmoidoscopy possibly because it was delivered on demand rather than continuously.

Randomized clinical trial of Entonox versus midazolam-fentanyl sedation for colonoscopy

BACKGROUND

Intravenous sedation for colonoscopy is associated with cardiorespiratory complications and delayed recovery. The aim of this randomized clinical trial was to compare the efficacy of Entonox (50 per cent nitrous oxide and 50 per cent oxygen) and intravenous sedation using midazolam-fentanyl for colonoscopy.

METHODS

Some 131 patients undergoing elective colonoscopy were included. Patients completed a Hospital Anxiety and Depression questionnaire, letter cancellation tests and pain scores on a 100-mm visual analogue scale before, immediately after the procedure and at discharge. They also completed a satisfaction survey at discharge and 24 h after the procedure.

RESULTS

Sixty-five patients were randomized to receive Entonox and 66 to midazolam-fentanyl. Completion rates were similar (94 versus 92 per cent respectively; P = 0.513). Patients receiving Entonox had a shorter time to discharge. They reported significantly less pain (mean score 16.7 versus 40.1; P < 0.001), and showed better recovery of psychomotor function immediately after the procedure and at discharge. Patient satisfaction was higher among patients who received Entonox (median score 96 versus 89; P = 0.001).

CONCLUSION

Entonox provides better pain relief and faster recovery than midazolam-fentanyl and so is more effective for colonoscopy.

Nitrous oxide for applying local anesthesia in nasal operations: a randomized placebo-controlled single-blinded study

CONCLUSIONS

In our study setting nitrous oxide (N(2)O) did not show any clinical benefit in discomfort experienced when applying local anesthesia for nasal operations. Further studies with longer inhalation times are needed to elucidate the role of N(2)O in application of local anesthesia in nasal surgery.

OBJECTIVES

N(2)O inhalation reduces the discomfort experienced in various medical procedures. The objective of this study was to assess the suitability of N(2)O inhalation before application of local anesthesia for nasal procedures in outpatient surgery.

PATIENTS AND METHODS

This was a prospective, randomized, single-blinded, placebo-controlled study at the Helsinki University Central Hospital, Finland. Ninety patients were randomly divided into three groups. Group A inhaled 10 breaths of 50% N(2)O/50% O(2) through a nasal mask with a Porter 2000 MXR scavenging system before application of local nasal anesthesia, group B inhaled room air through the same mask and group C received only local anesthesia. A visual analog scale was used to assess pain, nausea, and discomfort related to the application of nasal anesthesia.

RESULTS

The N(2)O inhalation was easy to perform and well tolerated. The N(2)O inhalation before applying local anesthesia for nasal operations did not show any significant additional benefit in reducing pain or discomfort.

Nitrous oxide inhalation for transoesophageal echocardiography: an alternative to benzodiazepine sedation?

AIMS

Transoesophageal echocardiography (TEE) is usually performed using benzodiazepine sedation, which is a limiting factor for elderly patients or those with respiratory insufficiency. Kalinox, an equimolar mixture of nitrous oxide and oxygen, with no depressive respiratory action and fast reversible effects, seems ideally suited for performing TEE but has never been evaluated. The aim of the present study was to evaluate the TEE feasibility and efficiency using Kalinox compared with the standard care using benzodiazepine.

METHODS AND RESULTS

We prospectively enrolled 80 consecutive patients referred for TEE. In the 35 first patients, TEE was performed using intravenous benzodiazepine (Midazolam) and in the 45 last patients using Kalinox (nasal delivery). Pain and tolerance induced by the examination were evaluated on a 0-10 scale. Remembrance of the examination by the patient and quality of the TEE by the operator were also evaluated. All TEEs were performed by the same experienced operator. TEE duration was not different (6 +/- 3 vs. 7 +/- 4 min, respectively, P = 0.57). Patients in the Kalinox group felt TEE to be more difficult (P = 0.005) and remembered the procedure more clearly (P < 0.0001) but pain experience was not different (7 vs. 9% had a pain score >or=5, respectively, P = 0.75). Percentage of patients who agreed to have a second TEE if necessary was slightly lower (77 vs. 94%, respectively, P = 0.04). The operator judged TEE quality satisfactory in similar proportions (76 vs. 68%, respectively, P = 0.44).

CONCLUSION

These preliminary results show that TEE using Kalinox is feasible, provides similar pain relief despite more discomfort for the patient, and acceptable conditions for the operator. Thus, Kalinox use could be considered as an alternative to benzodiazepine sedation for patients intolerant to benzodiazepines such as elderly or respiratory-insufficient patients.

Nitrous oxide inhalation to improve patient acceptance and reduce procedure related pain of flexible cystoscopy for men younger than 55 years

PURPOSE

Flexible cystoscopy in men younger than 55 years is painful despite the current best standard anesthesia (20 ml 2% lidocaine gel 15 minutes before endoscopy). The anesthetic value of lidocaine gel is debated and led us to seek an alternative. Nitrous oxide is a well established analgesic and anxiolytic agent, and it significantly reduces pain associated with transrectal ultrasound guided prostate biopsy. We studied its use in flexible cystoscopy in men younger than 55 years.

MATERIALS AND METHODS

A total of 61 patients were prospectively randomized to receive air (31) or Entonox (30). Both groups had 3 minutes of gas via a breath activated facemask (either Entonox or air) before endoscopy. The gel control group was comprised of 8 patients who underwent cystoscopy after instillation of lidocaine gel. The air and Entonox groups had lidocaine gel as per best standard. Vital signs were recorded before, during and after cystoscopy. Patients completed a visual analog score for gel insertion and cystoscopy.

RESULTS

There were no statistically significant differences between the groups in terms of baseline characteristics. Pain scores for cystoscopy (p<0.001) and intraoperative pulse rate (p=0.008) were significantly less with Entonox. Side effects were transient and seen more often with Entonox (p<0.05). More of the air group would require more analgesia (p=0.001) or a general anesthetic (p=0.011) if undergoing repeat cystoscopy.

CONCLUSIONS

Nitrous oxide inhalation significantly reduces cystoscopy related pain without significant complications. We propose that Entonox should be the anesthetic agent of choice for men younger than 55 years.

Inhaled nitrous oxide (Entonox) as a short acting sedative during bone marrow examination

Bone marrow aspiration and biopsy is a procedure of central importance in the diagnosis of haematological disease and is one that can be safely performed in the outpatient clinic using only local anaesthesia. We evaluated the role of inhaled nitrous oxide (Entonox) as an adjuvant to local anaesthesia (LA) in patients requiring bone examination. We prospectively studied the role of Entonox in patients attending our outpatient department who required bone marrow examination. All patients received LA with injected 2% lignocaine but patients were then assigned to either LA alone or LA plus inhaled Entonox. Following the procedure patients were given a questionnaire and asked to score the discomfort associated with the procedure. Twenty-eight of 85 patients (33%) who received LA alone scored their pain as 3 (severe) compared with seven of 51 patients (14%) who received LA plus Entonox, P = 0.013. No adverse events were associated with Entonox use. Forty-three of the 51 patients who received Entonox stated that they would prefer to use this method of anaesthesia again. We conclude that inhaled Entonox is a useful adjuvant to local anaesthesia for patients undergoing bone marrow examination.

Selecting patients for flexible sigmoidoscopy. Determinants of incomplete depth of insertion

BACKGROUND

Flexible sigmoidoscopy (FS) is an effective method to prevent and reduce mortality from colorectal carcinoma (CRC). Incomplete depth of insertion (IDI) during FS may result in missed polyps and carcinomas. To determine whether it is possible to predict IDI, the authors analyzed factors that affected the depth of insertion in FS.

METHODS

For the current study, FS results were recorded prospectively over a 5-year period. A questionnaire was administered to the patient by the investigator prior to FS to collect data, including age, gender, weight, comorbid illnesses, history of prior abdominal and pelvic surgeries, family history of colon carcinoma or polyps, and prior FS or colonoscopies. The depth of insertion of the flexible sigmoidoscope from the anal verge, which was defined as the reading on the outside of the instrument at its maximal insertion, was measured in centimeters. IDI was defined as a depth of insertion < 50 cm. Classification and regression tree analysis was used to develop a model that included variables predictive of IDI.

RESULTS

The best classification tree included gender, age < 69 years (in women), and a history of hysterectomy. Men had a < 5% risk of an IDI and women age < 69 years without a hysterectomy fared as well (6.6%). Older women and younger women who underwent hysterectomy had higher rates of IDI (29.2% and 22.3%, respectively.)

CONCLUSIONS

The authors developed a model based on age, gender, and hysterectomy status that, after further validation, may be useful for predicting which patients likely will have an incomplete examination. In those patients who have a high probability of IDI, the choice can be made to offer colonoscopy or perform FS under sedation, with analgesia, or with the help of distraction techniques.

Entonox analgesia for prostatic biopsy

We performed a prospective randomised double-blind study to evaluate the efficacy of Entonox (nitrous oxide) as an analgesic for trans-rectal ultrasound (TRUS) and prostate biopsy. A total of 50 patients breathed either Entonox or air during sextant prostatic biopsies all of which were performed by the same surgeon. The degree of pain experienced was recorded on a 100 mm visual analogue pain scale. A total of 17 further patients were excluded from the study because they wished to drive home after TRUS. Most patients breathing air experienced moderate pain (median pain score 34), whereas those breathing Entonox experienced minimal pain (median pain score 11). Two patients who used Entonox and one breathing air experienced severe pain. We conclude that patients undergoing prostate biopsy without analgesia experience moderate pain and this can be reduced significantly by using Entonox.

Nitrous Oxide Sedation Reduces Discomfort Caused by Atrial Defibrillation Shocks

An implantable cardioverter defibrillator with atrial therapies (ICD-ATs) is an effective therapy to manage atrial tacharrhythmias. Acceptance of this therapy is limited by atrial shock related anxiety and discomfort. Inhaled nitrous oxide (N2O) is a potent sedative-analgesic-anxiolytic agent that may mitigate shock discomfort and anxiety and improve patient ICD-AT acceptance. ICD-AT patients with more than one ambulatory atrial shock within 12 months were enrolled and grouped by ICD-AT shock method; awake (n = 9) or asleep (n = 4) when ambulatory ICD-AT shock is delivered. A baseline questionnaire assessed the most recent ambulatory ICD-AT shock (3 +/- 3 months). A 65% N2O/35% O2 mixture was inhaled for 4 minutes followed by an ICD-AT test shock (18 +/- 8 J). The test shock mimicked the awake shock method. The test shock experience during N2O was evaluated via questionnaire immediately following and 24 hours after the shock. Shock related anxiety, intensity, pain, and discomfort were assessed using a ten-point rank scale. Baseline test shock scores were similar between the shock method groups. In the awake shock method group, N2O greatly reduced preshock anxiety by 48% (6.4 +/- 2.4 to 3.3 +/- 2.0, or), and shock related intensity (5.9 +/- 3.1 to 3.3 +/- 2.5), pain (5.0 +/- 2.6 to 2.0 +/- 2.1), and discomfort (5.6 +/- 2.4 to 1.3 +/- 1.4) from baseline values by 45%, 60%, and 78% (P < 0.05), respectively. The asleep shock method group reported no changes in shock related anxiety, intensity, pain, or discomfort. Atrial shock concern, assessed via a five-point rank scale (5 = extreme concern) was improved by N2O but only in the awake group (3.1 +/- 1.0 baseline to 1.6 +/- 0.5 N2O, P = 0.008). There were no adverse events with N2O and patients fully recovered within 5 minutes after N2O. In conclusion, 65% N2O greatly reduced shock related pain and discomfort, and significantly reduced atrial shock concern but only in the awake shock method group. The benefits of N2O therapy may expand the use and acceptability of ICD-AT therapy into a larger atrial fibrillation cohort.

Nitrous Oxide vs Periprostatic Nerve Block With 1% Lidocaine During Transrectal Ultrasound Guided Biopsy of the Prostate: A Prospective, Randomized, Controlled Trial

PURPOSE

We compared the efficacy of Entonox (BOC Gases, Manchester, United Kingdom), a mixture of 50% nitrous oxide and oxygen, with periprostatic infiltration of 1% lidocaine to provide analgesia during transrectal ultrasound (TRUS) guided biopsy of the prostate.

MATERIALS AND METHODS

The study included 235 consecutive men undergoing TRUS guided biopsy of the prostate for elevated prostate specific antigen or abnormal digital rectal examination. Patients were randomized to 3 groups, including group 1-84 controls who did not receive any form of analgesia prior to the procedure, group 2-75 who received periprostatic infiltration with 10 ml 1% lidocaine with biopsies performed 5 minutes after infiltration and group 3-76 who received Entonox for 2 minutes through a breath activated device prior to the procedure and thereafter according to patient preference. All patients were asked to indicate the level of pain experienced before and after the procedure on a 10 cm, nonnumerical, horizontal visual analog score. Results were analyzed using 1-way ANOVA.

RESULTS

Mean patient age was 68.8, 64.9 and 65.2 years, and mean visual analog score was 2.9, 1.6 and 2.2 in groups 1 to 3, respectively. Patients in groups 2 (1% lidocaine infiltration) and 3 (Entonox) experienced significantly less pain during the procedure compared with group 1 controls (p <0.001 and 0.028, respectively). There was no statistical difference in pain scores between groups 2 and 3 (p = 0.08).

CONCLUSIONS

Inhalation of Entonox or periprostatic infiltration with 1% lidocaine can be used for analgesia during TRUS guided biopsy of the prostate since each provides significant and similar pain relief.

Electroacupuncture analgesia for colonoscopy. a prospective, randomized, placebo-controlled study

OBJECTIVE

A study was undertaken to compare the effectiveness of acupuncture in reducing patient's discomfort and anxiety during colonoscopy with a standard sedation protocol.

METHODS

Thirty patients scheduled to undergo colonoscopy were randomly assigned to receive acupuncture, sham, or no acupuncture. A verbal rating scale was used to measure patient's pain when the endoscope reached four scheduled positions. Midazolam was administered at baseline and again anytime patients complained of "severe" pain. The amount of midazolam administered was recorded. A verbal rating scale was used to assess patient's satisfaction with the level of sedation achieved.

RESULTS

Pain level was lower, although not significantly, in the acupuncture group. Midazolam boluses were required in three patients with acupuncture (30%), eight in the sham group (80%), and nine in the control group (90%) (p = 0.01). Six patients in the acupuncture group (60%) reported optimum acceptance of colonoscopy compared with only one in the sham group (10%) and none in the control group (0%) (p = 0.016). Satisfaction scores, assessed 24-72 h after colonoscopy, were extremely high (median score 90 of 100) in the three groups.

CONCLUSIONS

Acupuncture may decrease the demand for sedative drugs during colonoscopy by reducing discomfort and anxiety of the patient and the well-known adverse effects of pharmacologic sedation.