Spinal Anesthesia and Maternal Hypotension

Spinal anesthesia (SA) is often used during childbirth for Cesarean sections (C-sections) or to minimize pain during vaginal delivery. One common side effect of spinal anesthesia is maternal hypotension, or low blood pressure (sometimes this is also referred to as a hypotensive crisis). Maternal hypotension may cause nausea and vomiting in the mother, and can seriously harm the baby. It can also lead to stillbirth and serious birth injuries.


Incidence of maternal hypotension after spinal anesthesia

Hypotension commonly occurs as a complication of spinal anesthesia (1, 2). One study on 511 mothers who received spinal anesthesia for a C-section found that 20% had mild hypotension, 35% had moderate hypotension, and 40% had severe hypotension (1).

Why does spinal anesthesia cause maternal hypotension?

Women who have received spinal anesthesia often lie in the supine position (flat on their backs), which can create pressure-related issues affecting various veins (3).

The height of the block, the mother’s position, and prophylactic measures taken may all influence the severity of maternal hypotension. Hypotension is more frequent when mothers are placed in the tilted supine position than when they are in the left lateral position (3, 4, 5).

Who is most at risk for developing maternal hypotension under spinal anesthesia?

Women are more likely to experience maternal hypotension as a side effect of spinal anesthesia if they have the following risk factors:

  • Advanced maternal age (over 35)
  • Body mass index (BMI)  ≥25 kg/m2
  • 11-20 kg weight gain
  • Gravidity ≥4 (Gravidity refers to the number of times a woman has previously been pregnant. A similar measure is parity, which refers to the number of times she has previously given birth)
  • History of hypotension
  • Baseline systolic blood pressure (SBP) < 120 mmHg
  • Baseline heart rate >100 beats/min
  • Fluid preloading  ≥1000 ml
  • Adding sufentanil to bupivacaine
  • Sensory block height >T4 in anaesthesia-related modelling (P < 0.05) (1)

For more information on these risk factors, please click here.

Why is maternal low blood pressure dangerous?

Prolonged maternal hypotension frequently causes nausea and vomiting in the mother, and can also be harmful to the fetus. Even brief episodes of maternal hypotension can result in fetal acidosis, lower Apgar scores (6), and hypoxic-ischemic encephalopathy (HIE).

Hypotension during pregnancy is associated with an increased risk of stillbirth (7), as well as pregnancy complications such as preterm birth, intrauterine growth restriction (IUGR), meconium stained  fluid, and postpartum hemorrhage (8). The lower the blood pressure, the higher the risk of poor pregnancy outcome.

The negative effects on fetuses are likely due to poor placental perfusion (9). Supporting this idea is the observation that diastolic hypotension and low mean arterial pressure (MAP) seem to be more likely to result in poor pregnancy outcome than is systolic hypotension (10). Diastolic hypotension refers to low pressure in the blood vessels when the heart rests between beats. Systolic hypotension is low pressure in the blood vessels while the heart is beating (11). MAP calculates overall blood flow to various organs (12).  

What can be done to prevent maternal hypotension and associated birth injuries?

If a mother has spinal anesthesia, her doctor must be vigilant for signs of hypotension. If promptly addressed, hypotension can often be improved by repositioning the mother or using a vasopressor. Physicians must also record the baby’s heart rate with a fetal monitor up until the point of abdominal prepping for C-section. In some cases, monitoring may also be required after preparation for surgery. A fetal heart rate monitor can show signs of fetal distress, which are indications that a baby is being deprived of oxygen. A baby in distress is in need of immediate medical attention and delivery. If medical professionals do not respond appropriately to signs of fetal distress, the outcomes can be serious and permanent. The baby may develop lifelong conditions such as hypoxic-ischemic encephalopathy (HIE), cerebral palsy (CP), seizure disorders, and developmental disabilities.

Legal help for medical malpractice and birth injuriesBirth Injury Law | Reiter & Walsh, PC

If your child has been diagnosed with a birth injury as the result of anesthesia misuse or lack of safety precautions taken by medical professionals, we encourage you to reach out to Reiter & Walsh ABC Law Centers.

Birth injury is a challenging area of law to pursue due to the complex nature of the medical records. The award-winning attorneys at Reiter & Walsh have decades of joint experience with birth injury cases. To find out if you have a case, contact our firm to speak with one of our lawyers. We have numerous multi-million dollar verdicts and settlements that attest to our success, and no fees are ever paid to our firm until we win your case. We give personal attention to each child and family we help, and are available 24/7 to speak with you.

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Related Reading

Anesthesia Errors and Birth Injuries

New FDA Guidelines Regarding Anesthesia and Sedation Drugs Prompt Debate

Preeclampsia (Maternal High Blood Pressure)

Sources

  1. Indian J Anaesth: Maternal and anaesthesia-related risk factors and incidence of spinal anaesthesia-induced hypotension in elective caesarean section: A multinomial logistic regression
  2. Anesth Analg: The effect of posture and baricity on the spread of intrathecal bupivacaine for elective cesarean delivery
  3. Med Sci Monit: Maternal Position and Development of Hypotension in Patients Undergoing Cesarean Section under Combined Spinal-Epidural Anesthesia of Intrathecal Hyperbaric Ropivacaine
  4. Anaesthesia: Left lateral vs. supine, wedged position for development of block after combined spinal-epidural anaesthesia for Caesarean section
  5. Anaesthesia: Hypotension following combined spinal-epidural anaesthesia for Caesarean section. Left lateral position vs. tilted supine position.
  6. Anaesthesia: Anaesthesia for Caesarean section and neonatal acid-base status: a meta-analysis
  7. JAMA: Hypertension-hypotension in pregnancy. Correlation with fetal outcome.
  8. Zbl Gynakol: Hypotonia in pregnancy (article in German; as cited within Warland, Jane. “Low Blood Pressure.” BMC Pregnancy and Childbirth 12.Suppl 1 (2012): A9. PMC. Web. 20 Feb. 2018.)
  9. Am J Epidemiol: Low blood pressure during pregnanacy and poor perinatal outcomes: an obstetric paradox
  10. Proceedings of the Stillbirth Summit 2011: Low blood pressure
  11. CDC: Measuring Blood Pressure
  12. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition: Chapter 16: Blood Pressure