Abstract
Pregnancy commonly results in musculoskeletal complaints. Although these complaints typically are benign and self-limited, symptoms may be disabling in some women. In addition, preexisting musculoskeletal disorders interact with pregnancy to a variable extent. These interactions range from an ameliorating effect of pregnancy on the course of the disease (e.g., rheumatoid arthritis) to the potential for significant and possibly life-threatening deterioration in maternal condition (e.g., uncorrected severe thoracic scoliosis). The purpose of this chapter is to discuss the most common musculoskeletal disorders encountered in pregnant women and their implications for obstetric and anesthesia providers.
Keywords
Lumbopelvic pain of pregnancy, Adult tethered cord syndrome, Scoliosis, Rheumatoid arthritis, Spinal dysraphism, Osteogenesis imperfecta, Achondroplasia
Chapter Outline
Lumbopelvic Pain of Pregnancy, 1139
Chronic Low Back Pain, 1140
Postpartum Backache, 1141
Scoliosis, 1141
Scoliosis Associated with Neuromuscular Disease, 1143
Interaction with Pregnancy, 1143
Surgical Management, 1144
Obstetric Management, 1144
Anesthetic Management, 1145
Chronic Inflammatory Arthritides, 1147
Spinal Dysraphism, 1151
Tethered Cord Syndrome and Arnold-Chiari Malformation, 1152
Obstetric Management, 1152
Anesthetic Management, 1152
Achondroplasia, 1154
Osteogenesis Imperfecta, 1154
Pregnancy commonly results in musculoskeletal complaints. Although these complaints typically are benign and self-limited, symptoms may be disabling in some women. In addition, preexisting musculoskeletal disorders interact with pregnancy to a variable extent. These interactions range from an ameliorating effect of pregnancy on the course of the disease (e.g., rheumatoid arthritis) to the potential for significant and possibly life-threatening deterioration in maternal condition (e.g., uncorrected severe thoracic scoliosis). The purpose of this chapter is to discuss the most common musculoskeletal disorders encountered in pregnant women and their implications for obstetric and anesthesia providers.
Lumbopelvic Pain of Pregnancy
Lumbopelvic pain is the most common musculoskeletal complaint during pregnancy; it comprises two distinct areas of discomfort: (1) the lumbar spine area (low back pain) and (2) the posterior pelvic girdle area (from the sacroiliac joints radiating down into the posterior thighs), which has been termed pelvic girdle pain. Pregnancy-related lumbopelvic pain occurs at some time during gestation in more than 50% of pregnant women and impairs at least one normal activity of daily life, including sleep; the prevalence ranges from 25% to 70%. It is the most common reason for sick leave during pregnancy. Women who complain primarily of pelvic girdle pain report more disability during pregnancy than those with isolated lumbar pain. Severe pelvic girdle pain is seen in less than 0.5% of women; however, differentiation between pelvic girdle pain and low back pain is important because the management differs and the disability of pelvic girdle pain is more likely to extend into the postpartum period for up to 1 to 2 years. There are indices developed specifically for the pregnant woman to assist in diagnosis and determining the degree of disability; the Pregnancy Mobility Index and Overall Complaints Index are examples. Risk factors for pregnancy-related lumbopelvic pain include a history of low back pain, young age, hypermobile joints, low socioeconomic class, multiparity, and spondylolisthesis; the strongest factors are prior history of lumbopelvic pain, previous non–pregnancy-related low back pain, and strenuous work. In addition, there are psychological determinants affecting the development of lumbopelvic pain. Women who score high on the stress and fear domains are more likely to have significant lumbopelvic pain. Women who have high pain scores on pain threshold testing are also more likely to develop lumbopelvic pain.
The etiology includes hormonal and mechanical factors. The corpus luteum synthesizes and releases relaxin, and maternal blood concentrations of this peptide hormone increase 10-fold during gestation. Relaxin induces ligamentous softening and peripheral and pelvic joint laxity, which cause instability of the symphysis pubis and sacroiliac joints; the extent of instability and disability may be related to the maternal concentration of relaxin. There is a correlation between serum levels of relaxin and the occurrence of back pain during pregnancy; women with incapacitating symptoms have the greatest serum concentrations of relaxin.
Mechanical changes have a later onset than hormonal changes. Women with pelvic girdle pain have increased pelvic joint motion, which increases sheer forces across the joints and likely results in pain. In all pregnant women, uterine enlargement results in a forward rotation of the sacrum and an increase in the lumbar lordotic curve, which tends to close the lumbar interlaminar space (see Fig. 2.10 ). This change exaggerates the mechanical load borne by both the facet joints and the posterior aspect of the intervertebral discs. These mechanical changes also may compromise nerve root foramina. Sciatica occurs in 1% of pregnant women, and most cases occur late in pregnancy. Sciatica is distinguished from pelvic girdle pain by its extension to the ankle or involvement of the foot, and it may be associated with neurologic changes. Disc herniation and sacral stress fractures are rare in pregnancy but do occur. Incapacitating pain that radiates below the knee, typically accompanied by progressive neurologic deficits or bowel and bladder dysfunction, distinguishes disc herniation from the more common and benign pregnancy related-lumbopelvic pain.
In summary, hormonal changes cause sacroiliac joint dysfunction, which is responsible for the lumbopelvic pain that occurs early in pregnancy. Mechanical changes are primarily responsible for the pain that manifests during late gestation, although symphysis pubis and sacroiliac joint instability may also continue to cause pain. Disc herniation is uncommon and is characterized by the presence of neurologic findings.
Obstetric Management
Treatment is conservative in the absence of neurologic compromise. The many studies now published on various treatment modalities for lumbopelvic pain have discordant results. Moderate quality evidence from single studies supports the use of structured exercise programs, acetaminophen administration, osteomanipulative therapy, pelvic belts, and acupuncture in the treatment of lumbopelvic pain. However, a 2015 systematic review revealed overall low-quality evidence supporting exercise therapy for low back pain and no effect on pelvic girdle pain. If nonrandomized controlled studies are included in the analysis, the evidence suggests combining modalities is the most effective strategy. Patients with severe neurologic signs or symptoms of disc herniation should be assessed by a consultant neurosurgeon or neurologist who can provide recommendations for intrapartum and postpartum care. In a woman with severe symptoms, the obstetrician may choose to perform elective assisted vaginal delivery to decrease maternal work and back stress during the second stage of labor; however, this strategy does not protect against having postpartum pelvic girdle pain. Because the disability associated with lumbopelvic pain, especially pelvic girdle pain, can impair the woman’s ability to function postpartum, it is important to diagnose pregnancy-related lumbopelvic pain and treat it appropriately.
Anesthetic Management
No evidence suggests that epidural or spinal anesthesia is contraindicated in patients with pregnancy-related lumbopelvic pain. The anesthesia provider may administer neuraxial anesthesia, even to patients with sciatica. However, neurologic signs and symptoms should be first identified, delineated, and recorded. It seems prudent to administer a dilute solution of local anesthetic, with or without an opioid, to minimize motor block associated with epidural analgesia during labor to reduce any further stress on relaxed sacroiliac joints. Women with lumbopelvic pain may be reluctant to have neuraxial anesthesia because of concern that it may aggravate symptoms. The literature does not support this fear, and reassurance may be required.
Careful attention to the positioning of the patient with back complaints is critical. The patient must not be placed in a position that she could not tolerate before the administration of neuraxial anesthesia. The lithotomy position puts significant stress on the lower back and should be avoided whenever possible. If it is used, care must be taken to raise and lower both legs simultaneously to prevent injury to the lumbar spine and to avoid extremes when positioning the legs. Finally, caregivers should avoid rotational movements of the spine during transfer of the patient between the bed and the operating table.
Chronic Low Back Pain
Approximately 50% of pregnant women with a previous history of back pain or those with chronic low back pain experience a recurrence or exacerbation of their symptoms during pregnancy. Neuraxial anesthesia may be more likely to fail in patients with chronic low back pain and in those who have had back surgery, although newer data are conflicting. Benzon et al. reported a delayed onset of epidural anesthesia in patients with back pain or sciatica; the affected roots were blocked 10 to 70 minutes later than the contralateral roots at the same level. The delay in block onset most likely results from the inability of the local anesthetic agent to diffuse into the area of the injured root. Luyendijk and van Voorthuisen evaluated 600 epidurograms and confirmed that contrast material failed to reach the nerve root in 33% of patients with uncomplicated disc prolapse and did not move beyond the affected disc space in 5% of cases. This may be caused by epidural space scarring and adhesions that may develop during healing after disc injury. Prolapse of an intervertebral disc may result in relative or total obstruction of the flow of local anesthetic agent within the epidural space.
Sharrock et al. reported a 91.2% success rate of epidural anesthesia in nonobstetric patients with a history of limited spine surgery, as compared with a 98.7% success rate in patients without back surgery. The greater failure rate was postulated to be secondary to the distortion of surface anatomy and the tethering of the dura to the ligamentum flavum by scar formation, which renders the epidural space discontinuous or obliterated. Support for this hypothesis is provided by LaRocca and Macnab’s description of the postlaminectomy membrane. They noted the postlaminectomy formation of organized fibrous tissue surrounding the dura and, at times, binding of the nerves to the posterior aspect of the disc and adjacent vertebral body. The fibrous response was proportional to the extent of surgical trauma and was more marked with greater operative exposures. Postlaminectomy spinal stenosis also may lead to attenuation or obliteration of the epidural space, and the most common site of obstructive stenosis is immediately above the fusion mass.
In contrast, Bauchat et al., in a prospective observational, case-controlled study of 42 women with a history of discectomy and 42 matched control women studied between 2007 and 2010, found no difference in the total bupivacaine consumption (primary outcome), duration of the neuraxial procedure, or need for epidural catheter replacement between the postlaminectomy parturients and the control parturients after combined spinal-epidural (CSE) or epidural labor analgesia. The only difference between groups was the need to attempt more than one interspace more often in the postlaminectomy group. A possible explanation for the difference in the Bauchat et al. study to former studies is that surgical techniques have changed in the past half century, and newer techniques may cause less trauma and scarring in the epidural space.
Obstetric Management
It is not uncommon for obstetricians to offer pregnant women who have had persistent chronic low back pain the option of cesarean delivery to decrease the potential for further back injury during labor. There are no data to either encourage or discourage this option.
Anesthetic Management
The anesthesia provider may offer epidural or spinal anesthesia to patients with previous lumbar spine pathology or surgery after an appropriate history and screening examination to identify any neurologic deficits. A decreased incidence of successful epidural anesthesia is possible, especially in patients who have had extensive surgery. Nonetheless, the experienced anesthesia provider will likely administer epidural anesthesia successfully in most patients. Subarachnoid anesthesia is likely to be more reliable than epidural anesthesia in this patient population.
Postpartum Backache
Postpartum backache is a common complaint worldwide, occurring in at least 25% of women, with 5% to 7% of women seeking medical help. Evidence emerged in the early 1990s implicating epidural labor analgesia as the cause for postpartum backache. These original investigations were based on postal surveys, notably provided to women up to 9 years after childbirth. These studies were followed by several prospective studies to eliminate the potential for reporting bias that may confound retrospective surveys.
Macarthur et al. prospectively studied the association between epidural analgesia and early, new-onset postpartum backache in 329 women. In patients who labored without epidural analgesia, the incidence of postpartum backache was 43% at 1 day, 23% at 7 days, and 7% at 6 weeks. The incidence of symptoms in patients who had received epidural analgesia was greater on the first postpartum day (53%), but this increase did not persist. At 1 year postpartum, 12% of the patients had back pain (9.9% in the epidural group and 13.8% in the control group). Howell et al. performed a randomized controlled trial comparing epidural with nonepidural labor analgesia in 369 nulliparous women. There was no difference in the incidence or characteristics of postpartum backache at 3 and 12 months postpartum. In a follow-up study, there was no difference between the two groups in the incidence of back pain, disability, or movement restriction more than 2 years after delivery.
Both transient and persistent postpartum backaches are common, but there is little evidence that they are related to the provision of epidural analgesia during labor. Similarly, no evidence suggests that denying a parturient epidural analgesia results in a lower incidence of back problems during the postpartum period. Factors associated with persistent postpartum backache include the presence of back pain before pregnancy, the presence of pregnancy-related lumbopelvic pain, cesarean delivery, and performance of physically demanding work. Some evidence supports the use of osteopathic manipulation to help relieve postpartum backache.
Scoliosis
Scoliosis is a lateral deviation in the vertical axis of the spine. The severity of scoliosis is determined by measurement of the angle of the spinal curve, the Cobb angle, which is expressed in degrees ( Fig. 47.1 ). The prevalence of minor curves is 4 per 1000 in the North American population; larger curves occur less frequently, predominantly in females. Severe scoliosis is relatively rare in pregnant women, occurring in 0.03% to 0.07% of pregnancies. Although women with moderate to severe scoliosis constitute a small population of obstetric patients, pregnancy in this population is common. Most cases of scoliosis are idiopathic, although some are associated with other conditions, most commonly neuromuscular disorders ( Box 47.1 ).
Congenital (Vertebral) Anomalies
- •
Hemivertebra
- •
Spinal dysraphism
Neurologic Disorders
- •
Cerebral palsy
- •
Polio
- •
Neurofibromatosis
Myopathic Disorders
- •
Myotonic dystrophy
- •
Muscular dystrophy
Connective Tissue Disorders
- •
Marfan syndrome
- •
Rheumatoid disease
Osteochondrodystrophies
- •
Achondroplasia/hypochondroplasia
- •
Osteogenesis imperfecta
Infection
- •
Tuberculosis
Previous Trauma
Scoliotic curves can be divided into structural and nonstructural varieties. Nonstructural curves are those seen with postural scoliosis, sciatica, and leg-length discrepancies. They do not affect the mobility of the spine and are nonprogressive. Structural curves are seen in patients with idiopathic scoliosis and with scoliosis resulting from the conditions listed in Box 47.1 . Structural curves lead to reduced spinal mobility, and affected patients typically have a fixed prominence (rib hump) on the convex side of the curve. A rotatory component is associated with the structural scoliotic curve. The axial rotation of the vertebral body is such that the spinous processes rotate away from the convexity of the curve toward the midline of the patient ( Figs. 47.2 and 47.3 ). Deformation of the vertebral bodies results in shorter, thinner pedicles and laminae, and a more narrow vertebral canal on the concave side. Vertebral deformation is unusual in patients with a Cobb angle less than 40 degrees.
Scoliosis interferes with the formation, growth, and development of the lungs; the occurrence of scoliosis before lung maturity may reduce the number of alveoli that ultimately form. The pulmonary vasculature develops in parallel with the alveoli; early-onset scoliosis and severe scoliosis may result in greater pulmonary vascular resistance and eventually lead to pulmonary hypertension. Musculoskeletal deformities also affect the mechanical function of the lungs; anatomic findings in scoliosis that are most commonly associated with respiratory compromise include the presence of a thoracic curve, thoracic lordosis, and a rib cage deformity. The most common pulmonary function abnormality is a restrictive pattern with decreases in vital capacity, total lung capacity, and lung compliance. This pattern occurs in all patients with a thoracic curve greater than 65 degrees. The functional residual capacity is reduced, and airways may close during normal tidal breathing. If the functional residual capacity is reduced to the extent that it falls below the closing capacity, atelectasis may occur in basal alveoli. The most common blood gas abnormality is an increased alveolar-to-arterial oxygen gradient, with reduced Pa o 2 and a normal Pa co 2 . It results from both venoarterial shunting and altered regional perfusion. Venous admixture may lead to arterial hypoxemia. The natural history of severe, progressive scoliosis includes early death from cardiopulmonary failure.
Permanent changes of the pulmonary vasculature are common in patients with a curve greater than 65 degrees. Pulmonary hypertension (a resting mean pulmonary artery pressure exceeding 25 mm Hg) occurs in many patients with severe deformity long before the onset of right-sided heart failure and is largely attributable to increases in vascular resistance resulting from chronic alveolar hypoxia, hypoxic pulmonary vasoconstriction, and anatomic changes in the vascular bed. Fixed pulmonary hypertension carries a grave prognosis in pregnancy and may prompt a recommendation to avoid or terminate pregnancy (see Chapter 41 ).
Scoliosis Associated with Neuromuscular Disease
When scoliosis develops secondary to a neurologic or myopathic disorder, abnormal respiratory function results not only from the skeletal deformity but also from abnormalities in the central control of respiration and the supraspinal innervation of the respiratory muscles, as well as from the loss of muscle function caused by the underlying disorder. Respiratory function may be further compromised by (1) impairment of the defense mechanisms of the airways caused by loss of control of the pharynx and the larynx, (2) an ineffective cough mechanism, and (3) infrequent or reduced large breaths. Recurrent aspiration pneumonitis may result from compromised protective airway reflexes. In general, the prognosis of scoliosis caused by neuromuscular disease is poorer than that of idiopathic scoliosis and is determined predominantly by progression of the primary disorder. Affected patients typically develop irreversible respiratory failure at a younger age, and pulmonary hypertension is common; pregnancy is uncommon in this population.
Interaction with Pregnancy
Pregnancy may exacerbate both the severity of the spinal curvature and cardiopulmonary abnormalities in women with uncorrected scoliosis. Progression of a curve, defined as an increase in the Cobb angle of 5 degrees or more over subsequent assessments, is more likely during periods of rapid growth and in patients with larger curves at the time of diagnosis. Curves that are less than 25 degrees or curves that have been stable before pregnancy typically do not progress during pregnancy. In contrast, more severe curves and those that have not stabilized may worsen. Some investigators have described a correlation between the severity of the curve and maternal morbidity and mortality. However, it is likely that the severity of functional cardiopulmonary impairment before pregnancy is a better predictor of maternal outcome than the severity of the curve. Patients with a severe curve (i.e., Cobb angle greater than 60 degrees) but good cardiopulmonary function tolerate pregnancy well, whereas in those with significant cardiopulmonary compromise, and especially in those with pulmonary hypertension, maternal mortality is high.
The physiologic changes of pregnancy include decreases in both functional residual and closing capacities and increases in minute ventilation and oxygen demand. The thoracic cage normally increases in circumference during pregnancy as a result of increases in both anteroposterior and transverse diameters. If the chest cage is relatively fixed by scoliosis, the diaphragm is responsible for all increments in minute ventilation. As the enlarging uterus causes elevation of the diaphragm, diaphragmatic activity is restricted and further decreases in residual and closing capacities may occur, which may result in both greater ventilation-perfusion mismatch and decreased arterial oxygen content. The antepartum onset of new symptoms of respiratory compromise or the exacerbation of preexisting symptomatology is associated with higher maternal morbidity and a greater likelihood that assisted ventilation will be required after cesarean delivery. In a retrospective review from Canada of 12 women (15 pregnancies) with restrictive lung disease (defined as forced vital capacity less than 70%), Lapinsky et al. found 20% had deterioration in pulmonary function during the pregnancy. Seven women had an initial forced vital capacity of less than 1 L; four of these women had underlying kyphoscoliosis.
Dyspnea on exertion is uncommon in patients with scoliosis who have curves less than 70 degrees, but it becomes more common as the deformity exceeds 100 degrees. In younger patients with a curve less than 70 degrees, exercise capacity is more likely to be impaired because of the lack of regular aerobic exercise and subsequent deconditioning rather than intrinsic ventilatory impairment. Dyspnea is common in many pregnant women; two features help distinguish physiologic from pathologic dyspnea. Physiologic dyspnea tends to occur earlier in pregnancy and often plateaus or even improves as term approaches. The pathologic dyspnea of cardiopulmonary decompensation more often begins in the second half of pregnancy and is progressive, often becoming most severe as gestation advances and the physiologic loading is maximal. Second, physiologic dyspnea is rarely extreme, and patients can maintain most daily activities. Dyspnea that is extreme or has a limiting effect on normal activity may signal maternal cardiorespiratory decompensation. Dyspnea at rest is also rare in the absence of cardiopulmonary dysfunction, as is dyspnea that is acute in onset or progressive and intractable.
Minute ventilation typically increases by 45% during pregnancy. Minute ventilation of the unmedicated parturient increases by a further 70% to 140% in the first stage of labor and by 120% to 200% in the second stage. Oxygen consumption increases above prelabor values by 40% in the first stage and 75% in the second stage (see Chapter 2 ). These levels may be unattainable by the scoliotic parturient with restrictive lung disease, and respiratory failure and hypoxemia may result during labor.
Pregnant women with pulmonary hypertension have a limited ability to increase cardiac output. During normal pregnancy, cardiac output increases 40% to 50% above nonpregnant measurements; during labor and delivery, even greater increases are observed. These increases are achieved with both larger stroke volume and a higher heart rate. These demands may put an excessive burden on the cardiovascular system in parturients who had marginal cardiac reserve before pregnancy. If the right ventricle fails in the presence of pulmonary hypertension, left ventricular filling will decrease and low-output failure and sudden death may occur.
Surgical Management
During spinal fusion and instrumentation, the spinal musculature is reflected off the vertebrae over the course of the curve and the spinous processes and interspinous ligaments are removed. The spine is subsequently extended, correcting the curve. The vertebrae are decorticated throughout the extent of the planned fusion, instrumentation is placed, and bone graft material from the ileum is placed over the decorticated vertebrae. A number of techniques for fusion have been described, but all involve both spinal instrumentation and extensive bone grafting in the axial spine.
Obstetric Management
Pregnant women with corrected scoliosis tolerate pregnancy, labor, and delivery well. In the absence of major lumbosacral deformity, there is little alteration of the pelvic cavity, and malpresentation is not more common than in women without scoliosis. Uterine function is normal, and labor is not prolonged. Spontaneous vaginal delivery is anticipated, and cesarean delivery should be reserved for obstetric indications.
The literature is conflicting as to whether the cesarean delivery rate is greater in women with scoliosis with or without surgery. In a retrospective study from Israel, 98 women with idiopathic scoliosis out of a cohort of more than 220,000 were reviewed for birth outcomes. Women with scoliosis (corrected or uncorrected) were not found to have an increased risk for cesarean delivery. Conversely, Chopra et al. reviewed pregnancy outcomes in 22 women with kyphoscoliosis (59% idiopathic) with a total of 34 pregnancies. In this study, 60% of women had severe restrictive lung disease, only one had surgical correction, and the cesarean delivery rate was greater than 75%. The difference in outcomes may be influenced by the severity and etiology of the scoliosis in the populations reviewed or differences in the local practice patterns for managing these patients.
Pelvic abnormalities are more common when scoliosis is associated with neuromuscular disorders and in patients with a severe, uncorrected curve. In addition, abdominal and pelvic muscle weakness predisposes parturients to problems with expulsion of the infant during the second stage of labor and may necessitate instrumental vaginal delivery. The need for instrumental or cesarean delivery is likely related to the severity of skeletal deformity, the resulting maternal compromise, and cephalopelvic disproportion.
In the second stage of labor, the diaphragm has a nonrespiratory function. With expulsive efforts, maximal isometric contractions may be sustained for 20 seconds or more, and diaphragmatic fatigue has been demonstrated even in normal, laboring women. In parturients whose diaphragmatic function is compromised by neuromuscular disease or severe scoliosis, the potential for fatigue and failure is greater; expulsive forces are decreased, the second stage may be prolonged, and a trial of labor may fail, necessitating instrumental or cesarean delivery. In addition, women with severe cardiopulmonary disease (especially those with gestational decompensation) may require urgent or emergency cesarean delivery because of maternal compromise or nonreassuring fetal status.
Anesthetic Management
Pregnant women who have thoracolumbar scoliosis with a Cobb angle greater than 30 degrees or who have undergone spinal instrumentation and fusion for scoliosis should be referred to an anesthesia provider for antepartum consultation. The anesthesia provider should (1) determine the etiology of the scoliosis, as well as the severity and stability of the curve; (2) obtain a history of maternal musculoskeletal and cardiopulmonary symptoms; and (3) review prior obstetric and anesthetic experiences. For patients with scoliosis secondary to neuromuscular disorders, the anesthesia provider should also become familiar with anesthetic considerations specific to the underlying disorders.
Women with suspected or evident pulmonary compromise should undergo evaluation by a pulmonologist, and pulmonary function studies and arterial blood gas measurements should be obtained. These patients must be reevaluated periodically to ensure that they are tolerating the increasing physiologic demands of pregnancy. Echocardiography is useful to assess right-sided heart function in patients with one or more of the following: (1) a curve of 60 degrees or more, (2) hypoxemia on arterial blood gas measurement, (3) moderate or greater reductions in predicted lung volumes or flows, (4) pulmonary hypertension, and/or (5) evidence of decompensating cardiopulmonary status. Radiographic studies performed before pregnancy and operative notes describing spinal surgical procedures should be reviewed before neuraxial anesthesia is initiated in any patient with significant scoliosis or previous spinal surgery. The anesthesia provider should also examine the spine and note the surface landmarks and interspaces that are least affected by the deformity. Modes of analgesia and anesthesia for labor and delivery can be discussed during antepartum consultation.
Invasive hemodynamic monitoring is rarely indicated during labor and delivery. Pulmonary function studies that suggest significant respiratory compromise or clinical evidence of impending respiratory failure warrant placement of an arterial catheter and serial assessment of blood gas measurements. Echocardiographic demonstration of significant right-sided heart dysfunction may warrant invasive or noninvasive cardiac function monitoring.
The anesthesia provider may offer neuraxial analgesia for labor and delivery to patients with severe thoracolumbar scoliosis. Identification of the epidural space is more difficult in such patients, and the anesthesia provider should anticipate a greater incidence of complications. It is useful to remember the presence of the vertebral rotation during the performance of neuraxial anesthesia in a patient with a significant lumbar curve, which results in the spinous processes (which often may be structurally deformed) rotating into the concavity of the curve. Therefore, the midline of the epidural space is deviated toward the convexity of the curve relative to the spinous process palpable at the skin level (see Figs. 47.2 and 47.4 ). The extent of lateral deviation is determined largely by the severity of the deformity. One method of placing an epidural or spinal needle is to direct the needle from a palpated spinous process toward the convexity of the curve, often at a significant angle. The experienced anesthesia provider can track the resistance of both the interspinous ligament and the ligamentum flavum to maintain the correct course into the epidural space. The extent of the local anatomic distortion is the limiting factor, and the selection of spaces that are least involved with the curve is advised. Huang suggested a modified paramedian approach based on work by Boon et al. in cadavers. The needle is placed lateral to the spinous process on the convex side of the curve (taking advantage of the wider interlaminar spaces on that side) and aimed directly perpendicular to the skin. The intent is to find lamina with the needle tip and then “walk up or down” the lamina to enter the epidural space ( Fig. 47.4 ).
