| Study, Year |
Number Enrolled |
Liquid Group
(n = 522) |
Air Group
(n = 515) |
Endpoints Assessed and Additional Comments |
| Grondin, 2009 [4] |
360 |
3 ml saline
(n = 172) |
3 ml air
(n = 173) |
Additional boluses: need for physician-administered boluses; need for epidural catheter replacement assessed at 4 hours |
| Norman, 2006 [5] |
50 |
3 ml saline
(n = 25) |
3 ml air
(n = 25) |
Unblocked segments assessed by alcohol wipe; no difference in VAS pain up to 30 minutes |
| Evron, 2004 [6] |
457 |
3 ml lidocaine
(n = 185) |
3 ml air
(n = 180) |
Unblocked segments assessed by blinded anesthesiologist; no difference in VAS pain at 1 hour |
| Beilin, 2000 [7] |
217 |
2 ml saline
(n = 80) |
2 ml air
(n = 80) |
No difference in overall pain score at 15 minutes; unblocked segment assessed by alcohol wipe; need for additional medication assessed at 15 minutes after last dose of LA; catheter replacement for inadequate analgesia as defined by the study |
| Valentine, 1991 [8] |
50 |
4 ml saline
(n = 25) |
4 ml air
(n = 25) |
Unblocked segment defined as a segment sensitive to pinprick while the adjacent segments above and below were pain free |
| Sarna, 1990 [9] |
67 |
10 ml saline
(n = 35) |
10 ml air
(n = 32) |
No definition for unblocked segment |
*The patient population in all six studies consisted of patients undergoing labor analgesia. Either air or liquid was used during the loss-of-resistance technique for determining
placement of the epidural catheter. LA = local anesthetic; VAS = visual analog scale |
