Table 3.
Characteristics of the five neonatal rodent studies included in the systematic review.
| References | Species, Strain, and Age | Intervention of interest (group size) | Outcome measures (identification of effect) |
|---|---|---|---|
| (21) | Mouse, various, strains, fetal pups embryonic day 14–20 (see note), postnatal day (PND) 1–7, PND 8–14 | 1. CO2 20% VDR 2. Na pentobarb IP, 800 mg/kg (PND 8–14 only) 3. Halothane 5%/O2 0.4 L/min (PND 1–7 n = 11, PND 8–14 n = 15) |
LORR: pentobarb faster than CO2 in both PND 1–7 and 8–14 pups Cardiac arrest: CO2 faster than pentobarb (evaluated only in PND 8–14 pups) Note: fetal mice (embryonic day 14–20) were also evaluated. Dams were euthanized with the three agents listed or via cervical dislocation with or without halothane anesthesia. For all methods, fetal pups were still alive at 20 min post-euthanasia/exposure of the dam. |
| (49) | Mice, various (including CD1, C57BL/6J, 129S2), ED 16 | 1. Cervical dislocation of dam 2. CO2 exposure of dam (details not specified) 3. Na pentobarb IP, 120 mg/kg to dam 4. Na pentobarb intraplacental, 600 mg/kg (n = 9) |
Dam treatments—time to fetus death: pentobarb = CO2, sodium pentobarbital < cervical dislocation; no difference between dam strain Fetal treatment—time to fetal death: pentobarb intraplacental < pentobarb IP to dam = CO2 dam < cervical dislocation of dam; B6 = 129S2, B6 < CD1 |
| (50) | Mice, various strains, PND 0–10 | 1. Plastic bag pre-filled with 100% CO2 (n = 5–10 per run, n = 2,355 total) | Time to death: 60 min for pups PND 0–6, 20 min for PND 7–10, recovery of pups after prolonged exposures common |
| (51) | Rat, SD and F344, PND 0–10 | 1. Plastic bag pre-filled with 100% CO2 (n = 10 per run, n = 791 total) | Time to death: 35 min for pups PND 0, 5 min for pups PND 10, recovery of pups after prolonged exposures common |
| (52) | Mice, C57BL/6 and CD1, PND 1–2 | 1. Plastic bags placed 0.5 mL isoflurane-soaked cotton into bag and resealed (n = 3–18, 76 total) | LORR 2 min, exposed for 30 min and then following 30–120 min post-exposure period 18/76 pups recovered |
IP, intraperitoneal; LORR, time to loss of righting reflex; pentobarb, pentobarbital; PND, postnatal day; VDR, volume displacement rate.