Epidural block for obstetrics: comparison of bolus injection of local anesthetic with gravity flow technique.
OBJECTIVE
To test the hypothesis that slow administration of local anesthetic into the epidural space by gravity flow reduces the incidence of signs and symptoms of unintended injection.


METHODS
Prospective, randomized study.


METHODS
Teaching hospital.


METHODS
600 ASA physical status l and II parturients scheduled for labor and delivery or elective cesarean section.


METHODS
After identification of the epidural space with pulsations of an air-fluid column, parturients for vaginal delivery (n = 380) were randomized to receive a test dose of 3 ml 3% 2-chloroprocaine with epinephrine 20 micrograms, two doses of 7 ml bupivacaine 0.03% with sufentanil 1 microgram/ml and epinephrine 2 micrograms/ml by either gravity flow (Group 1) given over 30 seconds or by bolus injection (Group 2) given over 5 seconds through the epidural needle; parturients for Cesarean delivery (n = 220) were randomized to receive a test dose and two doses of 6 ml lidocaine 2% with sufentanil 1 microgram/ml and epinephrine 2 micrograms/ml by either gravity flow or by bolus injection through the epidural needle. Changes in maternal heart rate (HR) and blood pressure, signs of intravascular injection, and adverse effects of epidural bupivacaine-sufentanil were recorded after each dose.


RESULTS
Gravity flow administration (Group 1) was associated with a smaller increase in mean maternal HR (p < 0.001), less hypotension (p < 0.01), sedation (p < 0.01), nausea (p = 0.01), and segmental spread (p < 0.0001) than were corresponding doses given by traditional bolus injection (Group 1) for vaginal or Cesarean deliveries. The incidence of systemic toxicity was zero of 300 (0%) with gravity flow and 4 of 300 (1.3%) by bolus injection, p = 0.12, Fisher's exact test. No patient in either group had an accidental intrathecal injection.


CONCLUSIONS
Gravity flow administration of local anesthetic-opioid solution during epidural block for obstetrics was associated with fewer signs of systemic drug absorption and cardiovascular perturbations than was the traditional bolus injection. This study supports the current opinion that slow administration of local anesthetic during epidural block contributes to fewer adverse events.
Cohen
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S
Department of Anesthesiology, Robert Wood Johnson Medical School, New Brunswick, NJ 08903, USA.
Amar
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D000767:Anesthesia, Epidural / Q000009:adverse effects; D000773:Anesthesia, Obstetrical / Q000009:adverse effects; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000009:adverse effects; D002585:Cesarean Section; D036861:Delivery, Obstetric; D004338:Drug Combinations; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D011446:Prospective Studies; D012039:Regional Blood Flow / Q000187:drug effects; D013594:Syringes
D000779:Anesthetics, Local; D004338:Drug Combinations