Nitrous oxide: a valuable alternative for pain relief and sedation during routine colonoscopy. Patient-administered nitrous oxide/oxygen inhalation provides effective sedation and analgesia for colonoscopy. Nitrous oxide for colonoscopy: a randomized controlled study. Immediate recovery of psychomotor function after patient-administered nitrous oxide/oxygen inhalation for colonoscopy. Nitrous oxide for colonoscopy discomfort: a randomized double-blind study. A double-blind, randomized controlled trial on the use of a 50:50 mixture of nitrous oxide/oxygen in pain relief during suction evacuation for the first trimester pregnancy termination.
Patient-administered nitrous oxide in 50% oxygen has lately come into use as an alternative to combined opioid and benzodiazepine medication for colonoscopic procedures. A randomized study was carried out comparing intramuscular pethidine hydrochloride 1 mg/kg with inhalation of Medimix (a mixture of nitrous oxide in oxygen 50%) for relief of pain and anxiety during colonoscopy.
                Thirty-eight patients (19 in the pethidine group and 19 in the nitrous oxide group) were studied. The following parameters were measured: blood pressure, pulse rate, and arterial oxygen saturation. At the end of the colonoscopy and before the patients left the ward, pain, nausea, and general well-being were evaluated by the patients using a visual analogue scale. The colonoscopy time, investigation conditions and the total length of hospital stay were registered.
                Colonoscopy time and the colonoscopists' opinions concerning the investigation conditions did not differ between the groups. Pain relief and patient evaluation of the total procedure were also equal between the patient groups. However, there was less nausea among the Medimix patients. Three patients in the pethidine group had oxygen saturations below 92%. There was no desaturation during and five minutes after colonoscopy in the Medimix group. Patients in the Medimix group left the hospital on average 34 minutes earlier than patients in the pethidine group.
                We conclude that the use of nitrous oxide (Medimix) as an analgesic is as good as pethidine for colonoscopy. Medimix has clear advantages compared to pethidine in terms of reducing nausea and shortening the hospital stay. In a double-blind, randomized, placebo-controlled study of patients undergoing colonoscopy, sedation with an inhaled mixture of nitrous oxide/oxygen was compared with conventional intravenous sedation (pethidine 50 mg, midazolam 2.5 mg). In the patients studied, no significant differences were noted in number of pain episodes, need for additional intravenous sedation, or patient pain scores between the group receiving the nitrous oxide/oxygen mixture (n = 30) and those managed with conventional benzodiazepine/opiate injection (n = 29). Both methods were significantly more effective than placebo (n = 30). Six patients in the benzodiazepine/opiate group had oxygen desaturation, whereas none did in the nitrous oxide/oxygen group. Duration of stay after the procedure was significantly shorter in the gas inhalation group than in those receiving conventional intravenous sedation. Except for patients with severe chronic obstructive pulmonary disease, nitrous oxide/oxygen inhalation is a safe and acceptable alternative method of sedation and analgesia during colonoscopy. Intravenous sedation/analgesia for colonoscopy is accompanied with certain risks and postprocedure drowsiness. We sought to determine whether inhaled nitrous oxide (Entonox: 50% nitrous oxide, 50% oxygen) provides adequate analgesia for colonoscopy and the impact of this agent on recovery.
                All patients undergoing outpatient colonoscopy were considered for the study (n = 248) except those with previous colonic resection. Data for patients unsuitable for randomization (n = 58) and those who declined to participate (n = 88) were also analyzed.
                One hundred two patients were randomized to receive inhaled Entonox alone (n = 56) or intravenous midazolam and meperidine (n = 46). Forty-nine (88%) patients randomized to Entonox underwent complete colonoscopy without conversion to intravenous medications. Entonox patients reported more pain (p < 0.0001), tolerated colonoscopy less well (p < 0.0001), were less satisfied (p = 0.01), and less willing to undergo colonoscopy again under the same circumstances (p = 0.04). Of patients receiving intravenous medication, 91% found colonoscopy less unpleasant and 9% as unpleasant as anticipated; this compares with 52% and 21% Entonox patients, respectively, and an additional 27% Entonox patients who found colonoscopy more unpleasant than anticipated. Recovery was faster among Entonox patients (median 30 versus 60 minutes, p < 0.0001).
                Entonox is less effective than midazolam with meperidine for colonoscopy but is acceptable in many patients and allows faster recovery. Previous studies have shown that patients inhaling-self-administered nitrous oxide/oxygen as a sedative/analgesic medication for colonoscopy were ready to leave the endoscopy unit on average sooner than those given conventional intravenous premedication. The aim of this study was to define the time course of recovery after nitrous oxide/oxygen sedation or intravenous opiate/benzodiazepine premedication for colonoscopy.
                Consecutive colonoscopy patients were randomized to receive either a 50% nitrous oxide/oxygen mixture (n = 12), or pethidine 25-50 mg and midazolam 2.5 mg (n = 15), or no sedation (n = 10). Psychomotor function was assessed by multiple-choice reaction time, hand-eye co-ordination, and letter deletion tests before and at 15-minute intervals after colonoscopy, with the assessment carried out by an observer blinded to the sedation regime.
                The mean duration and tolerance of the procedure were similar in the three study groups. Patients receiving nitrous oxide/oxygen mixture were judged (by clinical observation) to recover more quickly than those given conventional sedation (median 8 min, range 3- 25 min, vs. median 16 min, range 3-50 min). Recovery, as judged by a return to baseline in psychomotor function tests, was complete within 30 minutes in all patients receiving the nitrous oxide/oxygen mixture, compared to 50 minutes in those given conventional intravenous sedation.
                The rapid recovery observed with nitrous oxide/oxygen sedation for colonoscopy suggests that it is safe for patients to travel unescorted after the procedure. Driving may also be safe soon after nitrous oxide/oxygen sedation, but this requires further clarification. The possibility of reducing recovery time after colonoscopy was studied using patient-administered nitrous oxide and comparing it with our standard treatment of ketobemidone plus midazolam. Fifty consecutive colonoscopy patients were randomized to receive either (i) intravenous ketobemidone hydrochloride 2.5 mg, midazolam 2.5 mg, and breathing air from a face mask with a demand valve (KHM) or (ii) intravenous saline and a breathing mixture of even parts of oxygen and nitrous oxide (Entonox) from the same valve setup. Patient discomfort during colonoscopy was assessed using visual analogue scales. All patients were allowed to stay for recovery as long as they wanted, and the time was measured. Modified recollection tests were performed prior to colonoscopy and when the patients left the Endoscopy Unit, in order to study the degree of mental impairment induced by the procedure and the medication. All patients had complete colonoscopies of the same duration in both groups. Discomfort during colonoscopy was rated the same in both groups (2p = 0.6413). Both groups of patients scored identically in the precolonoscopy recollection test. Most patients had a lower score after colonoscopy, but Entonox-treated patients scored significantly better than those with KHM (2p = 0.0250). Patients treated with Entonox opted to leave the Unit directly after the procedure (median 0 minutes; interquartile range 0-5 minutes) compared to 38 minutes for those with KHM (interquartile range 10-75 min), 2p < 0.001. It seems from our data that nitrous oxide gives pain relief equal to that in our standard treatment.(ABSTRACT TRUNCATED AT 250 WORDS) This prospective study assessed the role of a 50:50 mixture of nitrous oxide (N2O) and oxygen for pain relief during the termination of first trimester pregnancies by suction evacuation under conscious sedation.
                Ninety women undergoing suction evacuation up to 12 weeks of gestation were randomized by a computer-generated randomization list and allocated using sealed envelopes to receive the N2O/O2 mixture or air during the operation. Pain scores during and after suction evacuation, post-operative side effects and satisfaction level were compared.
                No statistically significant differences in pain scores, post-operative side effects and satisfaction levels were found between the two groups.
                N2O/O2 did not reduce the pain level during suction evacuation for the first trimester pregnancy termination under conscious sedation.
Nitrous oxide is as efficient and safer than various pain relief methods used during colonoscopy procedures, but further trials are necessary.