الفهرس 
Physiological Changes during PregnancyOnly 14 pages are availabe for public view
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Abstract
Pregnancy results in a number of significant physiologic changes that require adjustment in anesthesia techniques for safe and effective management of the parturient undergoing cesarean delivery.
Many of the physiological changes of pregnancy are due to hormonal influence and may occur early in pregnancy. Significant changes in minute ventilation and functional residual capacity may predispose the mother to an anesthetic overdose. Also increased oxygen consumption and the decreased reserve may result in rapid falls in arterial oxygen tension despite careful maternal positioning and preoxygenation.
Similarly, the hypotensive syndrome associated with the supine position begins to manifest itself early in the third trimester and may lead to decrease in cardiac output, blood pressure and uterine blood flow.
Also, a wider dermatomal spread of sensory anesthesia was observed in parturients following the use of epidural anesthesia as compared with their nonpregnant counterparts of the same age group as epidural space volume reduced by an engorged epidural venous plexus because of aortocaval compression by the large gravid uterus.
Regional techniques have become now the most frequently administered anesthetics for cesarean section delivery. Advances in regional anesthesia and its widespread routine use have resulted in significantly enhanced maternal safety compared with that with systemic anesthesia.
In clinical practice, (Local anesthetics) LA combined with opioids is the most commonly used epidural solution. The advantages of adding epinephrine are controversial and other drugs such as clonidine are far from being the standard in obstetric analgesic practice.
Hypotension may occur as a complication of epidural or spinal regional block for caesarean section. Untreated hypotension may have important clinical sequelae for the mother and her fetus. Although prevention and treatment of hypotension are different:
1. Patient positioning and physical methods
2. Modifications of regional technique
3. Vasopressors
4. Intravenous fluids
Colloid and crystalloid fluids have different pharmacological properties, according to these properties we can chose suitable fluid, amount taken and timing of given.
However, combinations of therapies may be more effective. For example, use of a phenylephrine infusion with concurrent cohydration has been shown to be effective for preventing hypotension in >90% of cases.