↪️Despite decreased requirements during pregnancy ,spinal anesthesia requirements return to non pregnant levels by 12-36 hours postpartum. Abouleish et al found that patients required 30% more bupivacaine, to achieve a T4 level for post partum tubal ligation , upto 24 hours after delivery. Rapid decline in plasma progesterone levels, after delivery of placenta is one factor, which contributes to this.
↪️Cardiac output rises immediately after delivery because of autotransfusion of 500 to 750 ml of blood from the uterus. Patients with pulmonary hypertension and stenotic valvular lesions are at a particular risk at this time.
↪️Cardiac output returns to slightly above prepregnancy values about 2 to 4 weeks after delivery.
↪️FRC and residual volume rapidly return to normal.
↪️Many of the pulmonary changes caused by mechanical compression by the gravid uterus resolve quickly. Alveolar ventilation returns to baseline by 4 weeks postpartum, and there is a rise in maternal PCO 2 as the progesterone levels decrease.
↪️The dilutional anemia of pregnancy resolves, and the hematocrit returns to normal within 4 weeks secondary to a postpartum diuresis.
↪️Serum creatinine, glomerular filtration rate, and BUN return to normal levels in less than 3 weeks.
↪️Mechanical effects of the gravid uterus on the gastrointestinal system resolve about 2 to 3 days after delivery; however, gastric emptying may be delayed for several weeks as serum progesterone levels slowly decrease.
Reference:
Shnider and Levinson's anesthesia for obstetrics, Maya Suresh; Sol M Shnider; Gershon Levinson, 2013,English : 5th
Ana M. Lobo, Andrea J. Fuller,Marina Shindell, Chapter 59, Anesthesia Secrets, 4/e
