Analgesia, pruritus, and ventilation exhibit a dose-response relationship in parturients receiving intrathecal fentanyl during labor.

UNLABELLED: Several studies have characterized the 50% and 95% effective doses (ED50 and ED95, respectively) of intrathecal sufentanil for labor analgesia. Few have investigated these same criteria for the less expensive alternative, fentanyl. In addition, the ventilatory effects of intrathecal fentanyl at clinically relevant doses are unclear. We performed this study to establish the dose-response relationship of intrathecal fentanyl for both analgesia and ventilatory depression. Ninety parturients in active early labor (< or = 5 cm dilation) received intrathecal fentanyl 5, 7.5, 10, 15, 20, or 25 micrograms in a double-blinded, randomized fashion (n = 15 patients in each group). Parturients were monitored for degree of pain (measured using a 100-mm visual analog pain scale), blood pressure, arterial oxygen saturation (SaO2), respiratory rate, ETCO2, and fetal heart rate 0, 1, 5, 10, 15, 20, 25, and 30 min after the administration of intrathecal fentanyl. An absolute visual analog pain scale score < or = 25 mm was defined a priori as analgesic success. The percentage of parturients who achieved analgesic success was used to construct quantal dose-response curves, from which the ED50 and ED95 values were derived for the total population (mixed parity) and the nulliparous and multiparous subpopulations separately. Overall ED50 and ED95 values (95% CI) were 5.5 (3.4-7.2) and 17.4 (13.8-27.1) micrograms, respectively. Nulliparous values were lower (5.3 and 15.9 micrograms, respectively) than multiparous values (6.9 and 26.0 micrograms, respectively) but were within the 95% CIs of the total population. Pruritus incidence in parturients with analgesic success displayed a dose-response relationship identical to that seen for analgesia. ETCO2 displayed a dose-related increase, particularly at doses > or = 15 micrograms, without concomitant changes in respiratory rate or SaO2, which suggests a decrease in tidal volume. Even in the absence of overt signs or symptoms of somnolence, intrathecal fentanyl at doses within the effective analgesic range induced a change in ventilation that may last longer than the 30-min period we studied. IMPLICATIONS: Intrathecal fentanyl induces rapid and satisfying dose-dependent analgesia in early labor; however, it also produces dose-related decreases in ventilation in the absence of overt somnolence.

Recall of risks following labor epidural analgesia.

STUDY OBJECTIVE: To ascertain patients' recall of the risks of labor epidural analgesia from a discussion of informed consent during active labor. DESIGN: Survey analysis following an intervention. SETTING: Labor and delivery unit of a tertiary-care teaching hospital. PATIENTS: 101 ASA physical status I and II parturients in active labor. INTERVENTIONS: Patients were given a standardized discussion of the risks of labor epidural analgesia. MEASUREMENTS AND MAIN RESULTS: Within 24 hours of the informed consent discussion, patients were first asked to recall risks, and then asked to identify risks from a true and false list. Patients recalled 2.0 +/- 1.3 risks (mean +/- SD), with 12% recalling at least four risks, 37% recalling at least three risks, 66% recalling at least two risks, and 87% recalling at least one risk. There was no difference in level of recall between primiparas and multiparas, or in patients with mild and moderate pain scores versus those patients with severe pain scores. CONCLUSIONS: Recall of risks by parturients is similar to the recall of risks by other patients, and it does not appear to be affected by parity or the reported level of pain.

Sevoflurane and the 885A field anesthesia machine: clinical report.

The Ohmeda 885A field anesthesia machine is equipped with a non-agent-specific, universal vaporizer that can be used with most volatile anesthetic agents. On a recent humanitarian medical mission to Honduras, the 885A was used to administer general anesthesia to 26 patients utilizing sevoflurane, a new inhalational anesthetic with a variety of clinical benefits, including less airway irritability, making it ideal for inhalation inductions. Flow rates for delivery of anesthetic agent were calculated by using the enflurane portion of the Verni-Trol flow calculator wheel, because sevoflurane and enflurane have similar vapor pressures. Calculated anesthetic concentrations were compared with measured concentrations using linear regression analysis and found to have a Pearson product moment of 0.995. We find that the use of sevoflurane in the 885A is an excellent alternative to other inhalational anesthetic agents and may have applications for use during both military conflicts and peacetime missions in remote areas.