Comparison of relative potency of intrathecal bupivacaine for motor block in pregnant versus non-pregnant women

The impact of gestational age and fetal weight on the risk of failure of spinal anesthesia for cesarean delivery

“…Previous studies [2][3][4] reported that pregnant women require less local anesthetic than nonpregnant women and suggested that this is related to the physiological and hormonal changes in pregnancy. Uterine enlargement and inferior vena cava obstruction result in distention of the epidural veins leading to a decrease in volume of both subarachnoid and epidural spaces.…”

“…[2][3][4] The physiologic changes of pregnancy such as changes in spinal curvature, 5 decreased cerebrospinal fluid (CSF) volume caused by the distention of epidural veins as a result of inferior vena cava obstruction by the gravid uterus, 6 and enhanced sensitivity of neural tissue to local anesthetics may play a role in these observations. 7,8 While many studies have examined the difference between pregnant and non-pregnant women in the relative spread of spinal block for surgical anesthesia, [2][3][4] there are limited data reviewing adequate spinal dosing for preterm (<37 weeks of gestation) versus term (≥37 weeks of gestation) patients. A previous study 9 demonstrated that hyperbaric bupivacaine 11.25 mg provided adequate spinal block to T4 for women at term but failed to provide the same level in 84% of preterm women undergoing cesarean delivery.…”

Strength and sensation after epidural ropivacaine in men and women

“…Pain thresholds are higher in men than women [1,[16][17][18][19], and the median effective anaesthetic dose of caudal ropivacaine is less for men (0.296%) than women (0.389%) [2]. The neuraxial distribution and clinical effects of local anaesthetics are influenced by dose, volume, concentration and potency, as well as a patient's age, height, posture, pregnancy status and atherosclerosis [3,[20][21][22][23][24][25][26][27][28][29][30]. However, weight, height and BMI do not influence the extent of sensory analgesia after the subarachnoid injection of bupivacaine [26,27].…”

Bupivacaine Pharmacokinetics in Pregnant Women

“…The potency of bupivacaine for motor block in pregnant versus non-pregnant women was 1.14 times higher (95% CI 1.05-1.24). This is because the supine position can increase the dissemination of the injected drugs due to the increase in intra-abdominal pressure, in addition to the increase in blood flow in the vasculature in the epidural veins, which distends and compresses the intraspinal space decreasing the volume of the spinal fluid cerebral [18].…”