Please select the eligibility criteria that correspond to the clinical trial below.
Title: The Time Required to Remain Sitting After Spinal Anesthesia for 50% of Patients to Not Experience Hypotension
Brief Summary: Hypotension is extremely common after induction of spinal anesthesia for cesarean delivery. Anesthetic blockade of the sympathetic outflow of the spinal cord causes vasodilation, and is one cause of this hypotension. The higher the spread of the blockade will result in a higher incidence of hypotension. Injected hyperbaric medication has about 15 minutes to spread within the intrathecal space before it will be taken up by the nerve roots. The time that a patient remains in one position after medication injection will affect the spread of the resultant anesthetic block. A patient who is left sitting for a longer period of time after injection of hyperbaric medication will have a lower level of block than someone who is placed supine immediately. In this study, the investigators wish to use up down sequential analysis to determine the time period a patient should remain seated after intrathecal injection of hyperbaric bupivacaine that will result in a 50% rate of hypotension.


Options:
A: Inclusion Criteria:

* Healthy pregnant women
* Over 18 years old
* ASA 1-2
* Undergoing elective caesarean section
* Height over 160 cm or under 180 cm

Exclusion Criteria:

* Allergic reactions to ephedrine or phenylephrine
* High blood levels of bilirubin
* HELPP syndrome
* Preeclampsia (pregnancy-induced hypertension)
* Non singleton pregnancies
B: Inclusion Criteria:

* Patients 18 years or older, presenting for scheduled cesarean delivery to the C7 birthing centre.

Exclusion Criteria:

* Unable to communicate in English or French
* Multiple gestations
* Patients with hypertension
* Patients with contraindications to any drug or techniques used in the study
* BMI \> 35
C: Inclusion criteria:

* Ability to speak and understand English
* Term (37-42 weeks' gestation)
* Cephalic presentation
* Singleton pregnancy
* ASA 3 or less
* No pregnancy-induced hypertension
* No chronic hypertension
* BMI \<40
* No evidence of pre-epidural fetal heart rate abnormality
* No IUGR or low AFI. ASA 1-3 women who request epidural analgesia Informed consent signed upon admission to L\&D

Exclusion Criteria:

* ASA 4 women, BMI \> 39
* Contraindication to epidural analgesia
* Twin pregnancy
* Preterm labor
* Severe preeclampsia
* Decision to perform CS prior to epidural insertion
* Unable to read or speak English
* Unable or unwilling to sign the IFC
D: Inclusion Criteria:

* Elective Caesarean section
* Consent to be in the study
* Age 18-45
* ASA 1 or 2

Exclusion Criteria:

* Patient refusal
* Patients with known allergy to ondansetron will be excluded
* Contraindications to spinal anesthetic

  * Known Coagulopathy (acquired e.g. anticoagulation or existing such as liver disease; using patient history, physical examination to determine bleeding risks, a platelet count under 100 or a PT INR over 1.4)
  * Severely altered anatomy (e.g. post surgical changes)
  * Existing neurological deficits (Women with a history of migraine or tension headache will be allowed to enroll. More severe conditions with daily life limiting symptoms will be excluded. Examples include epilepsy, pseudotumor cerebri, prior stroke with persistent neurologic deficits, or any motor or sensory neuropathy with existing deficits)
  * Skin infection overlying site

Answer: B