Cesarean Section (Pre-term/IUGR)

Summary

  • Dose: Low birth weight (as often seen in pre-term parturients and IUGR) increases local anaesthetic requirements above that seen in term pregnancies. Refer to the table below for recommended doses of 0.5% hyperbaric bupivacaine. Combine with 15 mcg fentanyl and 100 mcg morphine.

  • Position: Sitting or lateral, immediately supine.

  • Expectation: Surgical block for up to 90 minutes post-spinal.

Recommended Dose of 0.5% Hyperbaric Bupivacaine


Gestation Age (Weeks) Birthweight @ 50th Centile (g) [female-male] [1] Dose of 0.5% hyperbaric bupivacaine (ml)
40
 3480-3620 2.2
38 3200-3300
36 2710-2820 2.4
34 2240-2340
32 1780-1880 2.6
30 1400-1498
28 1090-1165 2.8
26 840-900
24 641-684 3.0
Made with HTML Tables

Evidence

  • In a study by James et al. 2.25 ml 0.5% hyperbaric bupivacaine (without opioid) produced a block to pinprick at T4 in 100% of parturients at term (~38/40) but only 16% of pre-term parturients (~32/40) [2]. They also found a better correlation between fundal height and block height (c.f. gestational age and block height).

  • Adesope et al. reported an increase in failure rates for spinal anaesthesia with 0.5% heavy bupivacaine in pre-term patients [3]. Notably, they stated that, “when adjusting for potential confounders, low birth weight had a larger effect size than gestational age.”

References

  1. Dobbins et al. Australian national birthweight percentiles by sex and gestational age 1998-2007. MJA 2012;197:291-294.

  2. James et al. Combined spinal-extradural anaesthesia for pre-term and term Cesarean section: is there a difference in local anesthetic requirements. BJA 1997;78:498-501.

  3. Adesope et al. The impact of gestational age and fetal weight on the risk of failure of spinal anaesthesia for cesarean delivery. IJOA 2016;26:8-14.