Nitrous oxide: effective analgesic for vascular and interventional procedures

Effect of nitrous oxide in reducing pain of propofol injection in adult patients

In a randomized, double-blind, prospective trial we compared the efficacy of pre-treatment with nitrous oxide (with or without premixed lignocaine in propofol) for the prevention of propofol-induced pain. Ninety consecutive patients were recruited in the study and divided into three groups of 30 each, who received either 50% nitrous oxide in oxygen along with lignocaine 40 mg mixed in 1% propofol 20 ml (Group NL), 50% nitrous oxide in oxygen without lignocaine in propofol (Group N), and 50% oxygen in air with lignocaine mixed in propofol 40 mg (Group L). Pain scores were graded on a four point verbal rating scale (0-3). Eighty-nine patients completed the study while one patient developed excitement, agitation and tremor during nitrous oxide in oxygen inhalation. Eleven patients (36.7%) complained of pain in the group L compared to 7 (23.3%), and 1 (3.3%), in groups N and NL respectively [group NL vs group L (P < 0.001) and group NL vs N (P < 0.001)]. There was no statistical difference observed between group N and group L. Inhalation of 50% nitrous oxide reduces pain on propofol injection. The combination of 50% nitrous oxide and lignocaine mixed with propofol was the most effective treatment.

Sedation and analgesia in adult patients: evaluation of a staged-dose system based on body weight for use in abdominal interventional radiology

PURPOSE

To evaluate the safety and effectiveness of a systematic protocol for sedation and analgesia in interventional radiology.

MATERIALS AND METHODS

Ninety-one adult patients underwent 113 abdominal interventional procedures. Fentanyl citrate and midazolam hydrochloride were administered in one to five steps (A, B, C, D, E) until the patient was drowsy and tranquil at the effective loading dose (ELD). Doses per step were as follows: A, fentanyl 1 microg per kilogram of body weight; B, midazolam 0.010-0.035 mg/kg; C, repeat dose in A; D, repeat half the dose in B; and E, midazolam 1-2-mg boluses (maximum, 0.15 mg/kg).

RESULTS

The ELD was reached in no procedure after step A, in 70 after B, in 23 after C, and in 18 after D. Step E was needed in two procedures. The mean maximum pain score (scale of 0 to 10) was 3.4; pain scores in 85 (75%) procedures were 4 or less (discomforting). Severe pain occurred in seven (6%) procedures. Hypoxia (oxygen saturation < 90%) occurred in 11 (22%) procedures performed in patients breathing room air and four (6%) performed in those breathing supplemental oxygen (P: =.04). All patients responded to supplemental oxygen.

CONCLUSION

This stepwise "ABCDE protocol" allows safe and effective sedation of patients. It is easy to use and may be useful in training radiology residents, staff, and nurses in the techniques of sedation and analgesia. Supplemental oxygen should be used routinely.

Nitrous oxide analgesia in a pediatric emergency department

Nitrous oxide (N2O) has been shown to be an effective analgesic in adult medical outpatients, yet no prospective studies of its use in the pediatric medical outpatient exist. Thirty-four children requiring laceration repair were randomly assigned to one of two treatment groups: 30% N2O/70% O2 or a placebo, 100% O2. Pain behavior, using the observer-scored Children's Hospital of Eastern Ontario Pain Scale, was assessed by double-blind techniques, before and during the laceration repair. Less pain behavior was seen in children less than 8 years old who received the N2O mixture than in those receiving the placebo. In patients 8 or more years old who received N2O, there was a significant improvement in the second evaluation as compared with those receiving only O2 during the procedure (P less than .05). There also was a smaller increase in pain behavior, from the first to the second evaluation, in those receiving N2O (P less than .05). No side effects were encountered. The authors conclude that continuous N2O inhalation is an effective and painless analgesic in children for outpatient procedures. More effective analgesia will likely occur with 40% to 50% N2O, although these concentrations remain to be studied in pediatric outpatients.