ANESTHESIA AND THE PARTURIENT

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ANESTHESIAAND THE PARTURIENT

• DENNIS STEVENS CRNA, MSN, ARNP
• FEBRUARY 2006
• FLORIDA INTERNATIONAL UNIVERSITY
• PRINCIPLES ANESTHESIOLOGY NURSING II
• NGR 6093

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ANESTHESIAAND THE PARTURIENT

• Original lecture by
• DENNIS STEVENS CRNA, MSN, ARNP
• Modified and presented by
• VICENTE GONZALEZ CRNA, MS

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OBJECTIVES

• Explain major indications for cesarean section.
• Discuss considerations for administration of
  general and regional anesthesia in the
  parturient.
• Describe necessary preparations for induction of
  general anesthesia in the obstetric population.
• List significant criteria necessary for safe
  emergence and extubation following a cesarean
  section.
• Discuss relevant considerations in obese
  parturients that will influence the
  administration of anesthesia.

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REFERENCES

• Chestnut, D. H. (1999). Obstetric Anesthesia (2nd
  ed.).
• St. Louis, MO Mosby.
• Morgan, G.E., Mikhail, M.S., Murray, M.J.
  (2002). Clinical Anesthesiology (3rd ed.). New
  York, NY McGraw-Hill.

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ANESTHESIA FOR CESAREAN SECTION

• GENERAL ANESTHESIA
• Usually indicated for emergent procedure
• Airway must be evaluated
• Administer a nonparticulate antacid
• Rapid sequence induction with preoxygenation and
  cricoid pressure
• Extubation when patient awake and airway reflexes
  returned
• Typical EBL 750 1000 ml

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INTRODUCTION

• General anesthesia may be necessary for cesarean
  section in selected cases
• Approximately 15 of cesarean sections are
  performed under general anesthesia
• If endotracheal intubation fails, the life of the
  mother takes priority over delivery of the fetus
• With failed intubation, in absence of fetal
  distress, the patient should be awakened and
  regional anesthesia attempted or awake fiberoptic
  intubation performed. In the presence of fetal
  distress, if ventilation with cricoid pressure is
  possible, delivery of fetus may be attempted

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INDICATIONS AND CONSIDERATIONSFOR GENERAL
ANESTHESIA

• General anesthesia is not routinely used for
  elective cesarean section. Typically reserved for
  obstetrical emergencies
• Major indications for cesarean section
• Labor unsafe for mother and fetus
• Dystocia
• Immediate or emergent delivery necessary
• Indications for general anesthesia
• Contraindications to regional anesthesia
• Fetal distress
• Failed regional block
• Patient refusal

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INDICATIONS AND CONSIDERATIONSFOR GENERAL
ANESTHESIA

• When time is a limiting factor, general
  anesthesia is sometimes necessary because it
  offers speed of induction, reliability,
  controllability, and avoidance of sympathectomy
  induced hypotension
• Problems associated with general anesthesia
  principally involve failed intubation and
  aspiration. Physiologic changes of pregnancy
  increase the incidence of failed intubations and
  aspiration

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PREPARATION FOR GENERAL ANESTHESIA

• Airway evaluation
• Vital to identify patients with problematic
  airways early
• Physical factors and physiologic changes of
  pregnancy may complicate endotracheal intubation
• Aspiration prophylaxis
• Experienced personnel and backup plans
• Fetal considerations

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CONDUCT OF GENERAL ANESTHESIA

• Basic preparation
• Positioning and monitoring
• Maternal preoxygenation
• Induction
• Rapid sequence with cricoid pressure
• Intubate with 6.0-7.0 cuffed endotracheal tube
• Maintenance
• Emergence
• Patient extubated awake with airway reflexes
  intact
• If patient unstable, endotracheal tube remains in
  place

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THE OBESE PARTURIENT

• Considerations
• BMI wt (kg) / ht (m)2
• Morbid obesity defined as body weight more than
  twice the ideal weight, or BMI greater than 35
• The obese parturient is at greater risk for
  medical diseases
• Cardiovascular system
• Respiratory system
• Endocrine and metabolic system
• Gastrointestinal system

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THE OBESE PARTURIENT

• In the obese parturient with a difficult airway,
  every effort should be made to initiate an early
  regional anesthetic
• Cesarean section rate is significantly higher
• Anxiolytic drugs and opioids ought to be
  administered with great caution in the morbidly
  obese parturient
• Airway considerations
• Limited flexion and mouth opening
• Narrowed view of pharyngeal opening
• Higher incidence of failed intubation
• Proper positioning of the head and neck may
  facilitate endotracheal intubation

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OPTIMAL POSITIONINGFOR OBESE PARTURIENTS

• Proper positioning may facilitate endotracheal
  intubation elevation of shoulders, flexion of
  the cervical spine, and extension of
  atlanto-occipital joint.

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REGIONAL ANESTHESIAFOR LABOR AND DELIVERY

• OVERVIEW
• Regional techniques decrease likelihood of fetal
  drug depression and maternal pulmonary aspiration
• Should not influence the progress of labor or
  ability to bear down during the second stage of
  labor

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REGIONAL ANESTHESIAFOR LABOR AND DELIVERY

• LUMBAR EPIDURAL ANESTHESIA
• Advantages of continuous epidural analgesia
• Confirm placement of epidural catheter once
  placed
• Bupivacaine often selected
• Maternal blood pressure and heart rate monitored
  frequently
• AVOID HYPOTENSION!

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REGIONAL ANESTHESIAFOR LABOR AND DELIVERY

• SPINAL ANESTHESIA
• Administered immediately prior to vaginal
  delivery
• 25 27 gauge spinal needle selected
• COMBINED SPINAL EPIDURAL
• Advantages and disadvantages
• PUDENDAL NERVE BLOCK
• Usually performed by obstetrician

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ANESTHESIA FOR CESAREAN SECTION

• INDICATIONS
• Multiple factors
• Fetal distress
• Cephalopelvic disproportion
• Malpresentations
• Failure of labor to progress
• SPINAL ANESTHESIA
• Sensory level of T4 is desirable
• Minimize maternal hypotension
• Administer oxygen to improve fetal oxygenation

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ABNORMAL PRESENTATIONS AND MULTIPLE BIRTHS

• ABNORMAL PRESENTATIONS
• 90 of deliveries are cephalic presentation in
  either occiput transverse or occiput anterior
  position
• Persistent occiput posterior
• Breech presentation
• MULTIPLE GESTATIONS
• Consider prematurity and breech presentation
• Usually cesarean section

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ANESTHESIA FOR CESAREAN SECTION

• LUMBAR EPIDURAL ANESTHESIA
• Alternative regional anesthetic technique
• Sensory level more likely to be controlled
• Maternal hypotension less likely
• May be redosed if needed
• Postdural puncture headache does not occur

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MEDICOLEGAL ISSUESIN OBSTETRIC ANESTHESIA

• Risk-management strategies must be practiced to
  minimize both patient dissatisfaction and legal
  consequences in the event of unanticipated
  adverse outcome
• Every anesthesia care provider has a duty to
  provide professional services that are consistent
  with a minimum level of competence
• Based upon practitioner's qualifications, level
  of expertise, and the circumstances of the
  particular case

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ESTABLISHING MEDICAL MALPRACTICE

• Duty must be shown that a duty to provide care
  existed
• Breach must be shown that the health care
  provider failed to meet their duty to provide
  reasonable care
• Injury must be shown that the patient
  experienced an injury that resulted in damages
• Proximate cause must be shown that the
  negligence of the health care provider
  proximately caused the patients injury

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POTENTIAL RISK MANAGEMENTPROBLEM AREAS

• OB anesthesia often is an unpredictable,
  difficult, and high-stress environment
• Typical OB service is less familiar and more
  chaotic
• Anesthesia services may be urgently requested in
  a situation where there is little information
  available about the patient and the patient is
  unable or unwilling to answer questions
• Laboring women typically are not sedated and calm
  when regional anesthesia is requested
• Care may need to be provided for multiple
  patients
• Presence of patients support person during
  anesthesia care

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ANESTHESIA-RELATED INJURIES

• Maternal death
• Neonatal brain damage
• Headache
• Maternal nerve damage
• Pain during anesthesia
• Back pain
• Maternal brain damage
• Emotional distress
• Neonatal death
• Aspiration pneumonitis

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KEY POINTS

• Honest, caring, and comprehensive discussion with
  the patient before the administration of
  anesthesia
• Obtain informed consent
• Clearly document refusal of care
• Critical events involving the respiratory system
  were the most common precipitating events leading
  to adverse outcome
• Maternal closed-case files include a higher
  proportion of relatively minor injuries
• Careful use of an epidural test dose appear to
  have reduced the incidence of maternal
  convulsions

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THE DIFFICULT AIRWAY RISK

• Incidence of failed intubation is significantly
  higher in the obstetric population
• Correlation exists between the difficulty in
  maintaining an airway and
• Use of physical force
• Number of attempts at endotracheal intubation
• Incidence of complications
• Airway assessment
• Physiologic and anatomic changes associated with
  pregnancy

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THE DIFFICULT AIRWAY PROPHYLAXIS

• Regional anesthesia versus general anesthesia
• Preparation for general anesthesia
• Airway supplies
• Positioning
• Preoxygenation
• Aspiration prophylaxis
• Failed regional anesthesia

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THE DIFFICULT AIRWAY MANAGEMENT

• Regional anesthesia
• Local anesthesia
• Awake intubation followed by general anesthesia
• Direct laryngoscopy
• Blind nasal intubation
• Fiberoptic laryngoscopy
• Retrograde intubation
• Various laryngoscopes and intubating stylets

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THE UNRECOGNIZED DIFFICULT AIRWAY

• After induction of anesthesia, if a patient can
  not be intubated or ventilated by mask, an
  alternative means of maintaining ventilation and
  oxygenation must be selected
• Laryngeal mask airway (LMA)
• Institution of transtracheal jet ventilation
  (TTJV)
• Combitube
• Establishment of surgical airway

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INTRODUCTION

• All patients in the OB unit potentially require
  anesthesia
• All OB patients are considered to have a full
  stomach
• Contributing factors exist that increase the risk
  of pulmonary aspiration
• Small amount of clear fluid permissible during
  labor
• Minimum NPO status for elective c-section is 6
  hours
• Pulmonary aspiration is largely preventable,
  anesthetist can take measures to minimize the
  occurrence of this condition
• Contributes significantly to MM in OB patient
• Leading cause of maternal death under general
  anesthesia

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INCIDENCE

• Incidence of pulmonary aspiration in the general
  population undergoing elective surgery is
  12131 to 13216
• Occurs more frequently in patients having
  emergency surgery 1895
• Incidence of pulmonary aspiration in OB patient
  presenting for c-section under general anesthesia
  is 1661
• There has been a progressive decline in the rate
  of pulmonary aspiration as a cause of maternal
  death

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PREDISPOSING FACTORS

• Three components must be present together
  presence of an at risk stomach, reflux of
  gastric contents into oropharnyx, and inhalation
  of these contents into lungs
• As pregnancy progresses intragastric pressure is
  increased and lower esophageal sphincter pressure
  is decreased
• Gastric emptying is delayed in pregnancy
• Mendelsons syndrome increased risk for
  aspiration pneumonitis
• Term parturient at higher risk for difficult
  intubation

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PATHOPHYSIOLOGY

• Injury due to pulmonary aspiration is dependent
  on pH of gastric contents and presence of solids
  or liquids
• Histologic findings show damage to alveolar and
  endothelial cells
• Differentiation between aspiration of solids and
  liquids
• Hypoxia occurs rapidly after aspiration of
  gastric contents and is related to the degree of
  lung damage
• Pulmonary aspiration causes an acute chemical
  pneumonitis
• Pulmonary compliance is eventually reduced

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CLINICAL PRESENTATION

• Aspiration likely to occur in an unfasted
  parturient having emergency c-section under
  general anesthesia
• Risk is increased in association with difficult
  intubation, eclamptic patient, or obtunded
  patient
• Gastric contents may be seen in airway during
  intubation, most frequently a presumptive
  diagnosis is made
• Aspiration of large particulate matter may lead
  to partial or complete airway obstruction
• Shock complicates the course in 20-30 of
  patients

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CLINICAL PRESENTATION

• Initial chest x-ray findings are extremely
  variable and noncharacteristic. Infiltrates are
  mainly seen
• Immediately, chest films may not reveal any
  abnormalities, but all show some abnormality
  within 24-36 hours
• Majority of patients show rapid clinical
  improvement and recovery
• 10-15 rapidly deteriorate and die within 24
  hours due to respiratory failure. Remainder
  develop various complications
• Hospitalization is prolonged by an average of
  8-21 days

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PREVENTION

• Strategies applied to reduce the at risk
  stomach contents
• Emptying stomach contents with nasogastric tube
• Medication administration
• Antacids
• H2 Receptor Blockers
• Metoclopramide
• Omeprazole
• Strategies to prevent regurgitation
• Strategies to protect the airway

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MANAGEMENT

• Suction
• Bronchoscopy
• Improving lung function
• Ventilation
• Fluid therapy
• Steroid administration
• Antibiotic administration

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SUMMARY

• Pulmonary aspiration is a potential threat to
  every parturient
• Failed intubation and aspiration continue to
  cause morbidity and mortality
• Aspiration most often occurs during emergency
  cesarean section under general anesthesia in
  which difficult or failed intubation is
  encountered
• Measures for preventing aspiration focus on
  reducing the use of general anesthesia,
  administration of a clear antacid, and
  restricting oral intake during labor

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POSTPARTUM HEADACHE

• Differential diagnosis of postpartum headache
• Nonspecific headache
• Migraine
• Hypertension
• Brain tumor
• Subdural hematoma/ subarachnoid hemorrhage
• Pseudotumor cerebri/ benign intracranial
  hypertension
• Sinusitis
• Meningitis
• Pneumocephalus
• Caffeine withdrawal

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POSTDURAL PUNCTURE HEADACHE

• Postdural puncture headache (PDPH) during the
  postpartum period almost always is a complication
  of anesthesia
• Any breach of the dura may result in a PDPH
• Hallmark of PDPH is its association with body
  position
• Pain is aggravated by sitting or standing and
  relieved or lessened by lying down flat
• Headache is bilateral, frontal or retro-orbital,
  occipital and extending into the neck
• May be throbbing or constant and associated with
  photophobia and nausea

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POSTDURAL PUNCTURE HEADACHE

• PDPH is believed to result from decreased
  intracranial pressure as CSF leaks from the dural
  defect at a greater rate than it is being
  produced
• Leakage of CSF produces decreased ICP, traction
  on pain-sensitive intracranial structures, and
  cerebral vasodilation
• Incidence is related to needle size, needle type,
  and patient population
• Conservative treatment involves
• Recumbent positioning
• Analgesics
• IV or oral fluid administration
• Caffeine

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POSTDURAL PUNCTURE HEADACHE

• Epidural blood patch
• Inject 15-20 mL of autologous blood into the
  epidural space at, or one interspace below, the
  level of dural puncture
• Believed to stop further leakage of CSF by either
  mass effect or coagulation
• Effects may be immediate or may take several
  hours
• Approximately 90 of patients will respond to a
  single blood patch, and 90 of initial
  non-responders will get relief from a second
  injection
• Epidural blood patch either offered when PDPH
  apparent, or following a trail of conservative
  therapy (12-24 hrs)