LINEBURG


<< . .

 19
( 87)



. . >>

and acute fatty liver of pregnancy.129,130 The reader is referred to a syndrome seems to occur after maternal intravascular exposure to
review of the subject for more details.131 fetal tissue during normal labor, vaginal delivery, or C/S, and
should be designated in a more descriptive manner as anaphylac-
toid syndrome of pregnancy. Early recognition, invasive monitor-
Sickle-cell embolism
ing, and aggressive management should improve the outcome.
More than one third of pregnancies in women with sickle-cell
syndromes terminate in abortion, stillbirth, or neonatal death.132
Cystic fibrosis
Maternal mortality due to sickle-cell anemia is $1%, mainly due
to pulmonary embolism and infection.132 In sickle-cell disease
Epidemiology
erythrocytes undergo sickling when deoxygenated (see Chapter
17). The sickled cells are elongated and crescent shaped and have Cystic fibrosis (CF) is a lethal genetic disorder with an estimated
a tendency to form aggregates. The sickling mainly depends on incidence of 1 in 3300 for Caucasians, 1 in 8500 for Hispanics,
the presence of abnormal hemoglobin (HbS), which is a hemo- 1 in 15 000 for African Americans, and 1 in 32 000 for Asian
Americans.135 In the past, CF was seen rarely during pregnancy
globin variant (valine replaces glutamic acid in the sixth position
of the beta-chain). Increased sickling occurs when more than 50% but dramatic advances in the management of CF have improved
of hemoglobin is HbS. Other factors that affect sickling include life expectancy and quality of life, so that more women with CF
vascular stasis, hypothermia, hypovolemia, and acidosis. are now becoming pregnant. The number of pregnancies
The sickle cells aggregate in the circulation, which can lead to reported to a national CF registry between 1986 and 1990,
doubled from 52 to 111.136
pulmonary vascular obstruction and pulmonary infarction.
Common with other embolic disorders, patients with sickle-cell
embolism present with respiratory distress, chest pain, hypox-
Pathophysiology
emia, V/Q mismatch, and pulmonary hypertension. Anesthetic
management includes maintenance of oxygenation, avoidance of Cystic fibrosis is inherited in an autosomal recessive pattern.
dehydration, acidosis, and vascular stasis.133 Avoidance of aorto- The gene responsible for CF is located on the long arm of
caval compression is essential even in patients with sickle-cell chromosome 7 that encodes an epithelial cell membrane protein
trait. One patient died from a massive sickle-cell embolus follow- known as the cystic fibrosis transmembrane regulator
(CFTR).137,138 This is a complex chloride channel found in all
ing release of aortocaval compression during C/S at the time of
delivery.134 exocrine tissues.139
Mutation of the CFTR gene causes a defect in the CFTR. This
results in altered epithelial cell membrane transport of elec-
Infectious embolism
trolytes in all organs that express CFTR. These include the
Infectious emboli may complicate infection anywhere in the respiratory, gastrointestinal, and reproductive tracts; the pan-
body. Even a minor infection may produce a major embolic creas; and the liver. Defective epithelial transport of electrolytes
event. The most common foci are the pelvis, the tricuspid and produces abnormal secretions that result in a multisystem dis-
pulmonic valves, the abdomen, the veins of the extremities, and order that particularly affects the respiratory and gastrointestinal
systems.139
the skin and subcutaneous tissue. Gram-positive, gram-negative,
More than 1000 mutations have been discovered.140 The most
and anaerobic organisms may be involved and produce some-
what different signs and symptoms. In order for treatment to be common mutation results in deletion of phenylalanine at posi-
successful, the source of infection must be removed. tion 508 (ÁF508) of the CFTR. Homozygosity for ÁF508 manifests
in one of the most severe forms of CF.141 Phenotypic expression of
CF, however, is variable.142
Summary
Pulmonary embolism should be suspected in a pregnant women
Clinical features
presenting with acute cardiopulmonary decompensation. With
an increased incidence of DVT in pregnant women, anesthesiol- Cystic fibrosis commonly presents as a respiratory disease.
ogists need to be aware that these patients are prone to PTE. The Abnormal mucous secretions within the respiratory system result
entrainment of small quantities of air into the vascular compart- in increased adhesiveness of, and difficulty in clearing, secretions,
ment is a relatively common occurrence, but only larger volumes which then cause small airways obstruction. Chronic airway
of air with sufficiently rapid intravascular entrainment produces obstruction and mucus retention lead to airway colonization
clinically detectable effects. Patients undergoing C/S under re- and chronic infection, the most common pathogen being
gional anesthesia, with their uterus exteriorized and who develop Pseudomonas aeruginosa. The chronic inflammation that ensues
hemorrhagic hypovolemia are at a high risk of VAE. Amniotic causes progressive tissue damage and subsequent fibrosis,
fluid embolism is usually heralded by a sudden onset of O2 bronchiectasis, and distal hyperinflation. This, together with



89
1 Cardiovascular and respiratory disorders


Figure 4.7 Cardiorespiratory
Abnormal secretion
effects of cystic fibrosis.


Small airway obstruction Mucus retention



Airway colonization



Chronic infection and inflammation



HEMOPTYSIS Bronchiectasis Fibrosis Hyperinflation PNEUMOTHORAX


Ventilation-perfusion mismatching



PROGRESSIVE RESPIRATORY FAILURE



CHRONIC HYPOXEMIA



PULMONARY HYPERTENSION



COR PULMONALE


small airway obstruction, gives rise to V/Q mismatching, which insufficiency, and a family history of CF. Laboratory measure-
can lead to hypoxemia (see Figure 4.7). ments of sweat chloride concentrations greater than 60 mEq/l
Respiratory manifestations of CF usually start with a recurrent assist with the diagnosis. DNA testing to isolate the specific
cough that gradually becomes persistent and productive. Over time gene mutation confirms the diagnosis.
airway hyperactivity becomes a common finding and pulmonary
function testing reveals an obstructive pattern. With advanced dis-
Treatment
ease progressive respiratory failure occurs. Lung hyperinflation
predisposes to spontaneous pneumothorax and bronchiectasis Respiratory management of CF is primarily symptomatic, with
postural drainage for patients with copious mucus production,145
causes hemoptysis, which can be massive. Pulmonary hyperten-
sion secondary to chronic hypoxemia and subsequent RV dysfunc- and bronchodilators for those with a reversible component of
airway obstruction.146 Mild infectious exacerbations may be trea-
tion (cor pulmonale) appear as late sequelae (see Figure 4.1).
Exocrine gland dysfunction involving the pancreas is common ted with oral antibiotics. Inhaled tobramycin and colistin have
and leads to maldigestion, malabsorption, and insulin-depen- been used to manage respiratory infections with Pseudomonas
aeruginosa,147 and may be added to oral antibiotic treatment of
dent diabetes mellitus. Subacute intestinal obstruction can also
occur.143,144 In late disease, biliary cirrhosis and portal hyperten- milder infectious exacerbations. However, a severe acute respira-
sion may occur, with abnormalities of hepatic function, hypoal- tory infection warrants immediate hospitalization and aggressive
therapy with i.v. antibiotics.148 It is common practice to admin-
buminemia, and jaundice.
Abnormal cervical mucous production leads to female subfer- ister antibiotics continuously in order to prevent recurrence, but
tility. In the male, obstructive azoospermia involving the vas there are insufficient data to support this practice. Patients with
deferens is a frequent cause of infertility. chronic hypoxemia and cor pulmonale may benefit from contin-
uous O2 therapy.
Other forms of therapy include inhaled recombinant human
Diagnosis
deoxyribonucleases to reduce sputum viscosity,149,150 lung trans-
plantation (for patients with end-stage disease),151,152,153 and
The clinical diagnosis of CF is based on the presence of chronic
gene therapy.154 Current approaches to gene therapy include
obstructive lung disease before age 20, exocrine pancreatic



90
Chapter 4


the transfer of the normal CFTR gene to airway epithelium using
viral or nonviral carriers.154,155,156
Table 4.12 Intrapartum and regional anesthetic management
Maintenance of adequate nutritional intake is important in the
for parturient with cystic fibrosis
management of patients with CF. Pancreatic insufficiency
requires replacement therapy with lipase, protease, and amylase Discuss with multidisciplinary team (includes obstetric and nursing
enzymes to prevent malabsorption. teams)
Ensure good intravenous access
Continue all cystic fibrosis medications
Cystic fibrosis and pregnancy
Continue active physiotherapy
Effect of pregnancy on cystic fibrosis In patients with diabetes mellitus, check blood glucose regularly and
157
A 1980 report by Cohen and colleagues found that 18% of maintain tight control
pregnant women with CF died within two years of delivery. Avoid dehydration
More recent reports indicate that pregnancy does not affect Monitor SaO2 and administer humidified oxygen as indicated
CF. McMullen and colleagues found that, over the same time Establish labor epidural analgesia early, using a weak bupivacaine
period, women with CF who became pregnant experienced solution with opioid supplementation, and dose slowly and
similar respiratory and health trends as nonpregnant CF incrementally aiming for a T8 upper sensory level
women. However, pregnant women used a greater number of Employ elective assisted delivery to minimize cardiorespiratory stress
therapies and received more intense monitoring of their Use epidural anesthesia for cesarean section, if possible, and dose
health.158 Geddes emphasized that lung function appears to be slowly and incrementally aiming for a T6 upper sensory level
the most significant determining factor of outcome in pregnant
women with CF.159 FEV1 decreases similarly in both nonpreg-
Intrapartum management
nant CF women and pregnant CF women.158
General principles of management
Effect of cystic fibrosis on pregnancy Discussion among the pulmonologist, obstetrician, and anesthe-
siologist allows early formulation of a labor and delivery plan that
Preterm labor is markedly increased (as high as 45%) in mothers
with CF,159,160,161,162 possibly due to poor maternal nutrition and is based on the severity of the disease, obstetric indications, and
the patient™s wishes. Preanesthetic assessment of the patient
chronic hypoxemia. Preterm labor most commonly occurs in
mothers with severe disease. Edenborough and colleagues163,164 should be made at an early stage. The parturient should be care-
fully assessed with particular reference to her pulmonary condi-
reported a substantial risk of preterm delivery in women with a
tion, nutritional status, and diagnostic investigations. Options for
prepregnancy FEV1 of less than 60% of predicted. Because of the
labor analgesia and C/S should be addressed early.
increased rate of preterm delivery, the perinatal mortality rate is
also high.164 Continuous SaO2 monitoring should be established, and humid-
ified O2 administered if the SaO2 falls below 94%. Direct arterial
pressure monitoring is useful if cardiorespiratory function deteri-
Antepartum management
orates. Cor pulmonale can be confirmed by echocardiography.
Central venous pressure plus pulmonary artery monitoring is indi-
Patients should be reviewed throughout pregnancy by a multi-
cated when pulmonary hypertension or heart failure is suspected.
disciplinary team, which includes the pulmonologist, obstetri-
Other factors to consider during the peripartum period include
cian, physiotherapist, nutritionist, and anesthesiologist.
maintenance of hydration, continuation of CF medications, and
Involvement of an anesthesiologist should not be confined
monitoring insulin requirements in those women with diabetes
to the peripartum period. Regular assessment of the cardio-
mellitus.
respiratory system detects deterioration resulting from the
Valsalva maneuvers in the second stage risk a pneumothorax in
changing demands of pregnancy. Good bronchial toilet, early
women with CF, so assisted delivery reduces the cardiorespiratory
involvement of physiotherapy, maintenance of CF medica-
demands of delivery and the risk of pneumothorax. Deterioration
tions, and vigorous treatment of respiratory infections are
in maternal or fetal status may require rapid delivery by C/S.
mandatory.
It is important to assess and maintain optimal nutritional sta-
Anesthetic management during labor
tus during pregnancy, which may necessitate enteral feeding.
Considerations regarding anesthetic management center on
Pancreatic function should be evaluated, pancreatic enzyme sup-
maintaining optimal cardiorespiratory function. Adequate pain
plementation maintained, and diabetes mellitus closely con-
relief during labor prevents hyperventilation associated with
trolled. One study has shown that pregnant CF women have
labor pain. Hyperventilation increases work of breathing and
decreased insulin sensitivity and a predisposition to early devel-
opment of diabetes and poor weight gain.165 may cause decompensation in women with severe pulmonary
dysfunction.
Venous access may be difficult if there have been multi-
Nitrous oxide for analgesia is not recommended given the
ple admissions to hospital for parenteral therapy, and a long-
increased risk of barotrauma due to air trapping. Parenteral
term subcutaneous infusion device may be helpful (see
opioid analgesia may worsen pulmonary function by depressing
Table 4.12).



91
1 Cardiovascular and respiratory disorders


respiratory drive and inhibiting cough. Intrathecal opioids have thoracic motor block, which may impair ventilation and the abil-
been used for first stage of labor,166 but patients should be mon- ity to cough, must be avoided. This can be achieved by using a
itored for respiratory depression. Pain in the second stage can be continuous catheter technique to titrate epidural or spinal agents,
more difficult to control and may require the use of local anes- and by slow, incremental administration of local anesthetic solu-
thetic nerve blocks. tion. It is prudent to aim for an upper sensory level of T6 to lessen
Continuous lumbar epidural analgesia can provide excellent the risk of respiratory embarrassment. Using this approach the
pain relief and has been used in women with CF.167,168,169 A successful administration of epidural anesthesia in a parturient
with CF has been reported.170 Some patients may not tolerate
high thoracic motor block, which may impair the parturient™s
ability to cough and eliminate thick secretions, must be avoided. lying flat, in which case regional anesthesia is best avoided.
Use of dilute solutions of bupivacaine with opioid supplementa- Single-shot spinal anesthesia produces a dense motor and sen-
tion, and slow, incremental administration will keep the upper sory block that is difficult to control and is of very rapid onset. In
sensory level below T8. When there is evidence of heart failure, the patient with more severe respiratory disease, this sudden high
fluids should be administered carefully with CVP/PCWP block may precipitate a respiratory crisis. For these reasons this
monitoring. technique is not recommended. A CSE technique with a low
intrathecal dose may be a suitable alternative.
Anesthetic management for cesarean section Following C/S, these patients require close attention to ensure
In parturients with CF, no differences in outcome have been stability of hemodynamic and pulmonary function. An early
documented between general and regional anesthesia for C/S. return to full mobility should be encouraged and adequate pain
The choice between general or regional techniques should be relief is important in achieving this. Postoperative analgesia
made on the basis of individual circumstances, taking into can be achieved with parenteral or neuraxial techniques in
account the risks and benefits of each technique. When there is conjunction with NSAID therapy. Clinical respiratory status
evidence of heart failure, fluid administration should be titrated must be monitored regularly to detect opioid-induced respiratory
against the central venous pressure. depression.
Endotracheal intubation with GA may provoke bronchospasm,
and positive pressure ventilation may lead to barotrauma. If GA is
Summary
elected, the following should be considered: (1) the patient
should receive 100% O2 prior to intubation for a longer period of Cystic fibrosis is a rare inherited disorder, which can coexist with
time to produce effective denitrogenation; (2) employ techniques pregnancy. Abnormal mucous secretions within the respiratory
to reduce the risk of bronchospasm during endotracheal intuba- system may lead to difficulty in clearing secretions and small
tion; (3) humidify anesthetic gases to prevent inspissation of airways obstruction. Respiratory management of CF includes
mucus; (4) use positive-pressure ventilation with adequate tidal postural drainage and bronchodilators. Recent reports indicate
volumes and frequent suctioning to minimize the risk of atelec- that pregnancy per se does not affect CF; however, the incidence
tasis and collapse; (5) adjust ventilator settings to allow an appro- of preterm labor is increased in mothers with CF. Women with CF
priately long expiratory phase to prevent air trapping and reduce should be managed by a multidisciplinary team, and a plan for
the risk of barotrauma; (6) maintain oxygenation with an ade- labor and delivery should be based on the severity of the disease.
quate inspired O2 concentration and avoid nitrous oxide because Continuous lumbar epidural analgesia has been used success-
of the risk of air trapping (see Table 4.13). fully in women with CF and no differences in outcome have been
Regional anesthesia offers the advantage of avoiding endotra- documented between general and regional anesthesia for C/S.
cheal intubation with its associated risks. However, a high The choice between general or regional techniques should be
made on an individual basis, taking into account the risks and
benefits of both techniques.
Table 4.13 General anesthetic management for parturient
with cystic fibrosis
Pneumothorax
Preoxygenate with 100% for a longer period of time to produce
Introduction
effective denitrogenation
Humidify anesthetic gases to prevent inspissation of mucus
Pneumothorax is rare in pregnancy and about 50% of cases are
Employ techniques to reduce the risk of bronchospasm during
secondary to identifiable risk factors (see Table 4.14). Primary
endotracheal intubation
pneumothorax (PP) occurs in the absence of an identifiable risk
Institute positive pressure ventilation with adequate tidal volumes and
factor. However, PP may occur in women with unrecognized lung
frequent suctioning to minimize the risk of atelectasis and collapse
disease, as evidenced by CT studies. In these patients, pneu-
Adjust ventilator settings to allow for an appropriately long expiratory
mothorax probably results from rupture of subpleural blebs,171
phase to prevent air trapping and reduce the risk of barotrauma
especially with the increased respiratory demands of pregnancy.
Maintain oxygenation with an adequate inspired oxygen
Pneumothorax can occur at any time during pregnancy, although
concentration
half occur during the first and second trimesters while the
Avoid nitrous oxide because of the possibility of air trapping
remainder occur during the third trimester.172



92
Chapter 4


discharged from hospital. If a leak persists despite aspiration, tube
Table 4.14 Causes of secondary pneumothorax thoracostomy should be performed. Women with failed tube thor-
acostomy, or those with recurrent PP following successful aspiration
Respiratory tract infection
or tube thoracostomy, should receive definitive treatment using
Asthma
thoracoscopy, bleb resection, and pleurodesis (see Figure 4.8).
Prior history of pneumothorax
Thoracoscopy is effective in the prevention of recurrence.176
Cocaine abuse
For patients with stable secondary pneumothorax >15%, initial
Hyperemesis gravidarum
treatment consists of tube thoracostomy since aspiration is less
Histoplasmosis
likely to be successful. Definitive therapy using thoracoscopy
Tuberculosis
with bleb resection and pleurodesis is then performed to prevent
Lymphangiomyomatosis
recurrence. Thoracoscopy with bleb resection and pleurodesis is
Alpha1 antitrypsin deficiency
also indicated for failed tube thoracostomy.
Chest trauma
Thoracotomy with bleb resection and pleurodesis has been the
Iatrogenic
traditional approach to definitive treatment; however, thoracot-
omy confers maternal and fetal risks of major surgery, significant
Clinical features
postoperative pain, prolonged recovery,176 and greater mortality.
Patients usually complain of a sudden onset dyspnea and pleur- Consequently, thoracoscopy is increasingly replacing thoracot-
itic chest pain. The severity of symptoms is primarily related to omy for definitive treatment, and has successfully been used in
pregnant patients with pneumothorax.177,178
the volume of air in the pleural space, with dyspnea being more
prominent if the pneumothorax is large. A large pneumothorax is For persistent or recurrent pneumothorax during pregnancy,
associated with tachypnea, tachycardia, ipsilateral diminished some have advocated conservative management using long-term
breath sounds with hyperresonant percussion, and hypoxemia. chest drainage, while delaying definitive treatment until after
delivery.179 However, long-term chest drainage predisposes to
When hypotension is present, tension pneumothorax must be
considered. Reliance on classic clinical findings, however, may empyema, pain, and immobility.
lead to misdiagnosis. Chest pain and dyspnea may be attributed
erroneously to other causes.
Intrapartum management of pneumothorax
Definitive diagnosis is by chest x-ray. The fetus is not at sub-
stantial risk from radiation when a chest x-ray is performed with Oxygen consumption is increased 50% during labor. If a parturi-
the maternal abdomen shielded. The estimated dose of radiation ent presents with pneumothorax during the intrapartum period,
to the uterus in this setting is 1 mrad per examination. the additional respiratory stress can readily lead to hypoxemia
and risk fetal compromise. Therefore, O2 is administered while O2
saturation is continuously monitored, and treatment of the acute
Acute management of pneumothorax
episode is as described earlier.
Maternal O2 consumption is increased 20% during pregnancy. Epidural analgesia is highly recommended at an early stage in
Any additional respiratory stress may rapidly induce hypoxemia, labor because it dramatically reduces maternal O2 demand and
which can jeopardize the fetus.173 Therefore, all pregnant patients can be used for C/S if the need arises. For a vaginal delivery, an
with pneumothorax should be hospitalized regardless of the size elective assisted delivery is recommended. One wants to avoid
of the pneumothorax, and oxygen administered while continu- having the woman push, because increased intrathoracic pressure
ously monitoring O2 saturation. from expulsive efforts can aggravate the pneumothorax. For C/S,
Treatment criteria for the management of pneumothorax in regional anesthesia is highly desirable and GA should be avoided, if
pregnant patients are similar to those for nonpregnant patients. possible. When GA is unavoidable, increased minute volumes may
For unstable patients, (e.g. women with tension pneumothorax be required to maintain adequate ventilation in the presence of a
and hemodynamic compromise), immediate tube thoracostomy continued leak when a thoracotomy tube is present. Airway pres-
is necessary (see Figure 4.8). Needle aspiration may precede sures should be kept as low as possible to minimize air leak, and
tube thoracostomy as a life-saving measure.174 A stable pneu- nitrous oxide should be avoided.
mothorax, which occupies less than 15% of the hemithorax, can Labor epidural analgesia and assisted delivery are recom-
be managed with observation and administration of supplemen- mended for patients with an antepartum history of pneu-
tal O2 (see Figure 4.8). The rate of air reabsorption is markedly mothorax who have not received definitive surgical therapy,
increased with supplemental O2. since expulsive efforts during the second stage of labor can lead
to recurrence.178,179 In such patients, regional anesthesia is
For patients with stable PP greater than 15%, catheter aspiration
will suffice since both aspiration and tube thoracostomy have been recommended for C/S. If GA is unavoidable, similar precautions
associated with similar rates of success and recurrence (see are taken as previously outlined.
Figure 4.8).174,175 Catheter aspiration is typically accomplished by Patients with definitive surgical therapy during pregnancy
passing an 8-French catheter into the pleural space over an may be allowed to attempt spontaneous vaginal delivery. Again,
18-gauge needle. Following an adequate period of observation and regional anesthesia for C/S is preferable in these women,
radiographic confirmation of lung expansion the patient can be although, if required, GA can be administered safely.



93
1 Cardiovascular and respiratory disorders


Thoracoscopy to

<< . .

 19
( 87)



. . >>

Copyright Design by: Sunlight webdesign