Nitrous oxide midazolam

A 61-year-old woman undergoing mitral valve surgery received fentanyl, midazolam, nitrous oxide, and propofol infusion 3 mg/kg/hour during a 5-hour anesthetic. She developed lactic acidosis soon after the completion of surgery and required reintubation and ventilation. The peak lactate concentration, which occurred 1 day later, was 14.3 mmol/1. There was also mild disturbance of liver function. She eventually recovered. 

Midazolam (Versed), a short-acting benzodiazepine CNS depressant, is used as a preanesthetic drug to relieve anxiety for induction of anesthesia for conscious sedation before minor procedures, such as endoscopic procedures and to supplement nitrous oxide and oxygen for short surgical procedures. When the drug is used for induction anesthesia, the patient gradually loses consciousness during a period of 1 to 2 minutes. 

Severe withdrawal symptoms, including insomnia, irritability, agitation, withdrawal seizures, and delirium, have been described in both mice and humans chronically exposed to the anesthetics nitrous oxide, ether, and isoflurane (Arnold et al. 1993 Delteil et al. 1974 Deniker et al. 1972 Harper et al. 1980 Smith et al. 1979 Tobias 2000). These symptoms were controlled with the administration of y-aminobutyric acid (GABA)-ergic agents such as pentobarbital, midazolam, and diazepam (Arnold et al. 1993 Hughes et al. 1993). 

Thompson JM, Neave N, Moss MC, Scholey AB, Wesnes K and Girdler NM (1999). Cognitive properties of sedation agents Comparison of the effects of nitrous oxide and midazolam on memory and mood. British Dental Journal, 187, 557-562. 

Recovery is sufficiently rapid with most intravenous drugs to permit their use for short ambulatory (outpatient) surgical procedures. In the case of propofol, recovery times are similar to those seen with sevoflurane and desflurane. Although most intravenous anesthetics lack antinociceptive (analgesic) properties, their potency is adequate for short superficial surgical procedures when combined with nitrous oxide or local anesthetics, or both. Adjunctive use of potent opioids (eg, fentanyl, sufentanil or remifentanil see Chapter 31) contributes to improved cardiovascular stability, enhanced sedation, and perioperative analgesia. However, opioid compounds also enhance the ventilatory depressant effects of the intravenous agents and increase postoperative emesis. Benzodiazepines (eg, midazolam, diazepam) have a slower onset and slower recovery than the barbiturates or propofol and are rarely used for induction of anesthesia. However, preanesthetic administration of benzodiazepines (eg, midazolam) can be used to provide anxiolysis, sedation, and amnesia when used as part of an inhalational, intravenous, or balanced anesthetic technique. 

In 113 patients undergoing general anesthesia, intravenous midazolam 15 mg slowed recovery of the twitch height after vecuronium and atracurium compared with diazepam. The recovery index was not altered (162). However, in another study in 20 patients, midazolam 0.3 mg/kg did not affect the duration of blockade, recovery time, intensity of fasciculations, or adequacy of relaxation for tracheal intubation produced by suxamethonium 1 mg/kg, nor the duration of blockade and adequacy of relaxation for tracheal intubation produced by pancuronium 0.025 mg/kg in incremental doses until 99% depression of muscle-twitch tension was obtained (161). Furthermore, in 60 patients undergoing maintenance anesthesia randomly assigned to one of six regimens (etomidate, fentanyl, midazolam, propofol, thiopental plus nitrous oxide, or isoflurane plus nitrous oxide), midazolam did not alter rocuronium dosage requirements (165). 

A 2-year-old girl with a past history of asthma, developmental delay, short neck, and lumbar lordosis, but no known genetic defect or syndrome underwent anesthesia with midazolam and paracetamol premedication, halothane and nitrous oxide induction, and isoflurane plus nitrous oxide for maintenance of anesthesia. Difficulty with mouth opening was noted and endotracheal intubation was difficult. Limb rigidity developed rapidly. Thiopental and cisatracurium were given and the muscle rigidity abated over the next 10 minutes. 

Litman RS, Berkowitz RJ, Ward DS. Levels of consciousness and ventilatory parameters in young children during sedation with oral midazolam and nitrous oxide. Arch Pediatr Adolesc Med 1996 150(7) 671-5. 

Fentanyl, ketamine, midazolam, propofol, thiopental Enflurane, desflurane, halothane, isoflurane, nitrous oxide, sevoflurane... 

Respiratory An audit of a case register of a large pediatric emergency department has shown that of 2002 patients receiving pediatric procedural sedation (60% male, median age 6 years), 81% received nitrous oxide and 1% received nitrous oxide + midazolam [18 ]. There were serious adverse events in... 

Zier JL, Rivard PF, Krach LE, Wendorf HR. Effectiveness of sedation using nitrous oxide compared with enteral midazolam for botulinum toxin A injections in children. Dev Med Child Neurol 2008 50 (11) 854-8. 

Absence of cooperation can sometimes compromise the quality of study. Medications are usually not used for US scanning, but light sedation (equi-molecular mixture of nitrous oxide and oxygen, midazolam, hydroxyzine) could be considered in some circumstances, such as Doppler recordings. For further information on sedation, refer to VCU and CT sections in the same chapter. 

In many cases, no sedation is required except that provided by sterile Xylocaine (lidocaine) jelly that lubricates the catheter in boys. A quick examination performed by an experienced radiologist should not be painful. Postprocedural minor discomfort can occur, and it seems less worrisome when announced. Improvement by hydration and local care is the rule. In some children, major anxiety can be present. Inhalation of an equimolecular mixture of nitrous oxide and oxygen (Entonox) in fasting children can be helpful (Schmit and Sfez 1997). In uncooperative children who are too young to breathe gas, rectal midazolam can occasionally be used (Hypnovel 0.3 mg/kg, maximal dose 5 mg). For safety, sedation procedures should preferably be organized in collaboration with the department of anesthesiology. 

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