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  3. Controversies in Obstetric Anesthesia and Analgesia
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    • Publisher:
      Cambridge University Press
      Publication date:
      December 2011
      November 2011
      ISBN:
      9780511734847
      9780521171830
      DOI:
      https://doi.org/10.1017/CBO9780511734847
      Dimensions:
      Weight & Pages:
      Dimensions:
      (234 x 156 mm)
      Weight & Pages:
      0.48kg, 280 Pages
      • Subjects:
      Anesthesia, Intensive Care, Pain Management, Obstetrics and Gynecology, Reproductive Medicine, Medicine
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    • Selected: Digital
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    Subjects:
    Anesthesia, Intensive Care, Pain Management, Obstetrics and Gynecology, Reproductive Medicine, Medicine
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    Book description

    The provision of anesthesia during childbirth still generates considerable debate; opinions vary widely within the obstetric anesthesia community over issues such as the effect of anesthetic drugs on the fetal brain and the choice between different epidural techniques. Controversies in Obstetric Anesthesia and Analgesia debates these and other clinical management controversies encountered in daily practice, providing practical advice on how to manage each clinical problem. This concise, practical text is designed to provide rapid access to key information on both diagnosis and treatment, presenting each side of the debate in a clear discussion. Key references and suggestions for further reading are also provided. Written by a team of international practitioners working with and caring for high risk obstetric patients, Controversies in Obstetric Anesthesia and Analgesia is an invaluable resource for trainees and practitioners in anesthesia, obstetrics and critical care medicine.

    Reviews

    'We highly recommend this book. It has a permanent home in our hospital’s obstetric anesthesia workroom … this book is current, concise, and well-organized, and is a welcome addition to our practice.'

    Source: Anesthesiology

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    Contents

    Contents
    • Chapter 6 - Ultrasound guidance for epidural anesthesia
      pp 86-99
    • View abstract

      Summary

      The most commonly abused drugs include opioids, amphetamines, marijuana, ketamine and other hallucinogens, caffeine, solvents, tobacco, alcohol, and cocaine. Maternal drug abuse can have significant economic implications and also implications for being involved in criminal activities. Mothers who abuse drugs are 80% more likely to require the involvement of the anesthesiologist for analgesia and anesthesia in labor. Recognition of substance abuse is important due to the potential consequences for fetal death, premature labor and withdrawal symptoms in both the mother and baby. Venous access may be notoriously difficult and there are high prevalences of transmittable viral diseases, such as hepatitis viruses and human immunodeficiency virus (HIV), in populations who self-inject drugs of abuse. Chronic alcohol ingestion, acute intoxication, and withdrawal can all pose a challenge to the anesthesiologist. Gamma-hydroxybutyrate (GHB) has a short half life and the absence of toxic metabolites reduces its detectability.
    • Chapter 7 - Combined spinal–epidural anesthesia and continuous spinal anesthesia
      pp 100-112
    • View abstract

      Summary

      Maternal cardiac disease complicates up to 4% of pregnancies and is a major cause of maternal death. The anesthetic management of affected obstetric patients can be challenging and requires a thorough understanding of the cardiac pathophysiology and the physiological effects of pregnancy. The normal physiological changes of pregnancy result in a hyperdynamic cardiovascular system. These changes may significantly compromise the parturient with cardiac disease and affect anesthetic management for labor and delivery. Obstetric patients with cardiac disease require an early anesthesia consultation to allow appropriate anesthetic management to be determined. Vaginal delivery with a shortened second stage is usually preferred although there are some important exceptions. Cesarean delivery may be indicated in some patients with cardiac disease. Congenital heart disease (CHD) leads the cardiac causes of maternal morbidity and mortality. Postpartum monitoring should occur in a high dependency unit.
    • Chapter 8 - Coagulation and regional anesthesia
      pp 113-121
    • View abstract

      Summary

      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.
    • Chapter 9 - Air vs. normal saline for the loss of resistance technique during epidural insertion
      pp 122-130
    • View abstract

      Summary

      The International Postpartum Hemorrhage Collaborative Group has observed an increasing trend in postpartum hemorrhage (PPH) and its severity in a number of high-resource countries including the UK, Australia, Canada, and the United States. Antenatal optimization of hematinic status may avoid the need for transfusion should a hemorrhage occur. This is particularly important for women with identified risk factors or who refuse blood. Early recognition of physiological derangement is vital and modified obstetric early warning systems, tracking changes in maternal physiology, have been introduced. The physiological changes of pregnancy initially buffer the effects of hemorrhage, so early signs such as tachycardia, decreased urine output and tachypnoea should be sought. The aim is to resuscitate the patient by stopping the bleeding and restoring a circulating blood volume with oxygen-carrying potential. Placenta accreta is most commonly associated with a combination of a low-lying placenta and uterine trauma from an earlier cesarean section (CS).
    • Chapter 10 - Ambulatory and patient-controlled epidural analgesia
      pp 131-139
    • View abstract

      Summary

      Over the last decade there has been an explosion of literature published on the neuroapoptosis induced by anesthetic drugs in animals and the potential impact this may have on fetuses, neonates, and infants. The period of brain growth when synaptic differentiation occurs, also called synaptogenesis, occurs from the sixth month of gestation to 24 months after birth in humans. The teratogenicity of a substance is multifactorial and includes species susceptibility, dose, duration and timing of exposure, and genetic predisposition. Anesthetics have been shown to cause apoptosis in numerous cell types as well as cause neurotoxicity in a concentration- and time-dependent manner in in-vitro and in-vivo models, and mechanisms have been proposed based on the receptor activity of the anesthetic agents. In an extensive review on the effects of general anesthetics on developing brain structure and neurocognitive function, the evidence for individual anesthetic agents causing neurodegeneration and functional impairment was discussed.
    • Chapter 11 - Hypotension following spinal anesthesia
      pp 140-153
    • View abstract

      Summary

      This chapter presents evidence supporting the use of ultrasound to take the epidural catheterization and spinal injections away from being blind techniques, therefore aiming to help reduce the incidence of the potentially serious complications resulting from Central neuraxial blockade (CNB). CNB remains the gold standard technique of providing both analgesia and anesthesia in the obstetric population, a fact which is unlikely to change in the near future. Creating an ultrasound image is done in three steps: producing a sound wave, receiving the echoes and interpreting those echoes. Most diagnostic ultrasound transducers use artificial polycrystalline ferroelectric materials such as lead zirconate titanate. There is very little published data regarding the use of ultrasound for real-time visualization of epidural puncture for neuraxial blockade. Overall, the use of ultrasound in all aspects of regional anesthesia allows continual development and improvement of current techniques.
    • Chapter 12 - Prevention and management of postdural puncture headache
      pp 154-163
    • View abstract

      Summary

      Neuraxial analgesia techniques are commonly performed to relieve pain during labor and to provide analgesia during cesarean section. When combined spinal-epidural (CSE) is used for labor analgesia it provides a faster onset with minimal motor block. This chapter describes the history and use of CSE techniques in laboring patients and for cesarean section. It discusses the advantages and disadvantages of these techniques compared to traditional spinal and epidural techniques. The chapter outlines the use of continuous spinal anesthesia (CSA) in obstetric patients. The catheter appears to be at least as effective as with the epidural technique; however, CSE has a higher rate of complications (e.g. nerve damage, infection) and side effects (e.g. pruritus, fetal heart rate (FHR) abnormalities) compared to epidural analgesia. The theoretical advantages of hemodynamic stability and prolonged block can be easily achieved with other techniques such as CSE at much lower complication rates.
    • Chapter 13 - Epidurals and outcome
      pp 164-175
    • View abstract

      Summary

      This chapter provides an overview of the normal changes in coagulation associated with pregnancy. It discusses the most common challenges experienced by anesthesiologists in the coagulopathic pregnant woman. The result is a hypercoagulable state that maintains placental function during pregnancy and protects the parturient from hemorrhagic complications during delivery but increases the risk of thromboembolism. The risks of neuraxial anesthesia in the coagulopathic parturient must be weighed against the risks of the alternatives and the gravity of the situation. Normal pregnancy imparts an increased tendency toward thrombus formation, extension, and stability. Epidural or spinal hematoma are rare and devastating complications of neuraxial anesthesia in parturients. Their occurrence is almost invariably associated with clinical coagulopathy or the use of anticoagulants. Decisions regarding the most appropriate anesthetic management for obstetric patients can be difficult and fraught with pitfalls.
    • Chapter 14 - Epidural and intrathecal opiates and outcome
      pp 176-185
    • View abstract

      Summary

      The two most commonly used techniques in clinical use are the loss of resistance to air and to normal saline. The term loss of resistance refers to the subjective feel of a change in resistance while the epidural needle penetrates the interspinous ligament, the ligamentum flavum, and subsequently into the epidural space. This chapter evaluates whether, during the loss of resistance technique, air or saline used during epidural anesthesia influences either the efficacy of regional blockade or the incidence of complications such as accidental dural puncture rate and postdural puncture headache (PDPH). There are few prospective, controlled, randomized double-blind trials comparing the complications of air vs. saline in identifying the epidural space. Using saline as part of a loss of resistance technique to identify the epidural space is probably the most widely accepted practice worldwide among anesthesiologists.
    • Chapter 15 - Remifentanil infusions and patient-controlled analgesia
      pp 186-195
    • View abstract

      Summary

      Epidurals are the most effective form of analgesia for the laboring parturient; however, pain relief has come with potential risks. Ongoing maintenance of analgesia may be with any number of techniques, which include but are not limited to continuous infusions, patient-controlled epidural analgesia (PCEA), and programmed intermittent epidural boluses. Ambulatory epidurals promote the retention of urinary function and reduce the risk of urinary catheterization during labor. PCEA has proven to be both safe and effective. The most consistent benefit appears to be decreased motor block with ropivacaine. Whether initiated or not with a combined spinal-epidural (CSE), ongoing analgesia with low-dose infusions or PCEAs confers these same benefits. Evidence suggests PCEA protocols that use a low-dose background infusion in combination with larger boluses with longer lockout intervals may be superior.
    • Chapter 16 - Nitrous oxide
      pp 196-206
    • View abstract

      Summary

      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.
    • Chapter 17 - Fasting and aspiration prophylaxis in labor and for cesarean section
      pp 207-214
    • View abstract

      Summary

      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.
    • Chapter 18 - Controversies surrounding airway management and cesarean delivery
      pp 215-228
    • View abstract

      Summary

      Epidurals are the most effective mode of analgesia for labor pain. Neurological complications, although rare, remain one of the most important causes of anxiety in the parturient and it is important to provide reassurance while providing accurate data for informed consent. Central nervous system (CNS) lesions secondary to epidural analgesia are very rare. They can be classified into four etiologies: traumatic, ischemic, infective, or chemical, or can sometimes be a combination thereof. High-quality evidence supports that there is no causal relationship between epidural labor analgesia and the development of new chronic back pain. High-dose epidural fentanyl may be associated with an adverse effect on breastfeeding. Women who labor with epidural analgesia experience an increase in temperature, which is associated with administration of antibiotics to both mother and babies, increased neonatal sepsis workups, as well as possibly increased operative deliveries.
    • Chapter 19 - Oxygen supplementation for cesarean section
      pp 229-237
    • View abstract

      Summary

      Neuraxial opioids are an essential component of the pharmacologic options available for use in present-day obstetrical anesthesia practice. By producing an analgesic action in the absence of associated motor block or reduction in sympathetic tone, neuraxial opiates are an ideal component of the list of analgesic medications available for use by the obstetrical anesthesiologist. Morphine is a hydrophilic opioid, among the first to be used for postsurgical analgesia when administered by epidural or intrathecal route. The lipid solubility of hydromorphone is between that of lipid soluble fentanyl and hydrophilic morphine. Fentanyl is a highly lipid soluble opioid with a resulting rapid onset and short duration of action. The beneficial effects of neuraxial opioid administration are associated with potential complications or side effects, both in the mother and in the fetus. Hydrophilic drugs are primarily used as part of a multimodal analgesia plan for postoperative pain management following cesarean section.
    • Chapter 20 - Oxytocin use and dosage during cesarean section
      pp 238-245
    • View abstract

      Summary

      Remifentanil's safety profile in neonates combined with rapid onset and offset means that it offers potential not only as a labor analgesic, when administered as patient-controlled analgesia (PCA), but also as an adjunct to general anesthesia, particularly in high-risk obstetric patients. An ideal intravenous opiate should have an onset and offset that can match the time course of uterine contractions, while preserving uterine contractility and a reassuring cardiotocograph (CTG). The analgesia experienced should be considered worthwhile and there should be minimal maternal and neonatal effects, allowing administration up to and during delivery. Remifentanil can offer sedation and analgesia for the anxious patient without the risk of persistent opioid effects. Systemic opioids are the mainstay of managing discomfort during epidural anesthesia for cesarean section. High doses of remifentanil with general anesthesia have unpredictable neonatal effects, making attendance by a physician trained in neonatal resuscitation mandatory.
    • Chapter 21 - Analgesia post cesarean section
      pp 246-257
    • View abstract

      Summary

      Nitrous oxide in modern anesthetic practice is used as a carrier gas for more potent volatile anesthetics during general anesthesia and as an analgesic during labor and childbirth. Nitrous oxide is easily administered to parturients using a facemask or mouthpiece and a tank or wall supply of N2O/O2 mixture. The primary controversies surrounding the use of nitrous oxide in labor analgesia consider efficacy, side effects, and safety. Possible side effects of nitrous oxide range from the unpleasant (nausea) to the potentially catastrophic (uterine atony). Most studies that have examined the efficacy of nitrous oxide in obstetric anesthesia practice have also documented side effects. There are several controversial safety issues surrounding the use of nitrous oxide in the labor and delivery suite. The potential exists for environmental contamination with resultant occupational exposure by healthcare workers and others.

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