Hypotension following spinal anesthesia in obstetric patients is commonplace. Spinal anesthesia induces a sympathectomy, leading to vasodilation, increased venous capacitance, and decreased venous return. High levels of sympathetic blockade can decrease maternal cardiac output although with lesser height and degrees of sympathetic blockade a compensatory increase in cardiac output may be seen secondary to reductions in cardiac afterload. Risk factors associated with spinal-induced hypotension include: increasing age, pre-existing hypertension, higher infant birth weight and obesity. Many studies have been carried out to determine the role of ephedrine and phenylephrine during spinal anesthesia for cesarean section. Chronic hypotension, especially if accompanied by decreased cardiac output, may reduce placental perfusion and impair fetal oxygenation. Drawbacks to ephedrine include variable efficacy at prophylaxis of hypotension secondary to spinal anesthesia in low doses or in doses normally used in the clinical setting.

The prevention and management of postdural puncture headache (PDPH) in the obstetric patient continues to challenge the anesthesiologist. This chapter discusses the clinical management of PDPH in obstetric patients and suggests recommendations based on current, relevant evidence. The presence of focal neurological signs may point toward other neurological problems and prompt further investigations and assessments. The low cerebrospinal fluid (CSF) volume causes a drop in subarachnoid pressure. The incidence of PDPH in obstetric patients is relatively high due to the effects of gender and young adult age. It is also related to the size and design of the needle used and the experience of the anesthesiologist carrying out the procedure. Larger randomized controlled trials may help provide insight into the optimal use of the epidural blood patch (EBP) and other treatments. Such trials will be difficult to perform due to the low incidence of accidental dural puncture (ADP) and PDPH.

Pre-eclampsia is a multisystem disorder unique to human pregnancy. Over the years, advances in the understanding of the pathophysiology and hemodynamics of the disease have greatly impacted its obstetrical and medical management. Considerable research into the pathophysiology of pre-eclampsia is ongoing and many areas are still debated. Increased heart rate, cardiac output, stroke volume, and left ventricular end-diastolic volume accommodates the growing metabolic needs of the pregnancy. Decreased total peripheral vascular resistance as a consequence of the presence of the low-resistance placental circulation is a physiological characteristic of a normal pregnancy. Current general consensus suggests a combined approach using clinical measurements and serum markers of placental abnormality appropriate for gestational age. Aspirin has been the most widely studied drug therapy in the prevention of pre-eclampsia. Spinal anesthesia is an acceptable option for women with severe pre-eclampsia, especially as an alternative to general anesthesia in emergency cesarean section.

This chapter reviews the use of regional anesthesia techniques in obese patients. The most extensive experience with regional anesthetic techniques in obese patients is with neuraxial anesthesia. Obese patients require less local anesthetic than their normal counterparts to achieve a similar sensory level. For a lumbar approach for either an epidural or spinal anesthetic, a cooperative patient can be asked to identify the "midpoint of your body". The incidence of complications with epidural anesthesia increases with increasing weight. As with epidural anesthesia, obesity is an important factor influencing spinal anesthesia. Neuraxial anesthesia is often used in combination with general anesthesia during surgery to reduce the amount of inhalational and intravenous agents. All peripheral nerve blocks were performed using a nerve stimulator technique. Overweight and obese patients should not be excluded from undergoing regional anesthesia in the ambulatory setting.