the obese parturient

1. THE OBESE PARTURIENT HARRY SINGH, MD DEPT. OF ANESTHESIOLOGY UTMB

3. DEFINITIONS AND INCIDENCE Normal BMI: 25 Overweight �up to 20% more than ideal body weight or BMI 25-29 Obesity : BMI > 30 Morbid Obesity : twice the ideal body weight or BMI > 40 Recent data from National Center for Health Statistics suggests 54% Americans overweight and 21% obese 6%-10% parturients morbidly obese

4. TYPES OF OBESITY Android Obesity: Truncal distribution of fat Associated with high incidence of cardiovascular disorders Gynecoid Obesity: Fat distributed to thighs and buttocks Associated with pregnancy

5. PATHOPHYSIOLOGIC CHANGES PULMONARY: ? O2 consumption and ? CO2 production: Secondary to metabolic activity of adipose tissue ? Minute Ventilation Reduced chest wall compliance (Restrictive defect) ? Functional Residual Capacity and Residual Volume FRC may be less than closing capacity?airway closure during tidal ventilation?V/Q mismatch and shunting Accentuated in supine, trendelenberg or lithotomy position

6. EFFECT OF POSITION ON LUNG VOLUMES

7. PICKWICKIAN SYNDROME or OHS 8% of obese patients Alveolar hypoventilation, somnolence and morbid obesity ? Soft tissue mass of oropharynx ?Intermittent obstruction of airway during sleep Hypoxemia, hypercarbia Polycythemia, pulmonary hypertension and right ventricular failure Pulmonary embolism and pneumonia

8. PATHOPHYSIOLOGIC CHANGES CARDIOVASCULAR: ? Blood Volume and ?Cardiac Output (? Stroke volume) Blood flow through adipose tissue-2 -3 ml/min/100 g Morbid obesity: 50% mild HTN, 5-10% severe HTN Doubling of incidence of CAD ? Afterload and preload (?BP and ?Blood Volume) ? Left ventricular end diastolic pressure and LV hypertrophy More vulnerable to pulmonary hypertension Airway obstruction or hypoxemia? ? PAP or PAOP

9. PATHOPHYSIOLOGIC CHANGES ENDOCRINE AND METABOLIC: ? Incidence of adult onset diabetes Impaired glucose tolerance Resistance to insulin Hypertrophy of Islets of Langerhans High serum triglycerides High serum cholesterol ? Incidence of IHD

10. PATHOPHYSIOLOGIC CHANGES GASTROINTESTINAL: ? Intragastric and intrabdominal pressures ? Lower esophageal sphincter tone ? Hiatus Hernia Strong correlation between BMI and reflux symptoms (Odds ratio 6.3 for women with BMI>35) 80% obese patients have gastric pH < 2.5 86% obese patients have gastric volume>25mL 75% patients at risk of aspiration pneumonitis Combination of pregnancy and obesity increases the risk of aspiration pneumonitis

11. CHANGES IN THE AIRWAY Short neck, ? chin to chest distance Limited flexion of cervical spine Nonexistent atlantooccipital gap Limited atlantooccipital extension and bowing of cervical spine and forward displacement of larynx Adiposity of the face, shoulders, neck and breasts Narrow pharyngeal opening due to enlarged tongue and fleshy pharyngeal and supralaryngeal tissues ? Incidence of failed or difficult intubation 33% incidence of difficult intubation in obese parturients Percutaneous cricothyrotomy may be difficult due to difficulty to palpate landmarks

12. MATERNAL MORTALITY Obesity risk factor in 12 of 15 anesthesia related deaths in Michigan between 1972 to 1984: Failed intubation leading cause of death 4 of 7 maternal deaths in Chicago Maternity Hospital in women > 200 lbs 12% of all maternal deaths in obese women between 1963 and 1997 in Minnesota: Pulmonary embolus leading cause of death Anesthesia, surgery and pregnancy additively increase the mortality and morbidity in these patients.

13. MATERNAL COMPLICATIONS 47% of obese parturients have antenatal disease Gestational diabetes (Odds ratio: 4.00) Gestational hypertension (Odds ratio: 3.20) Preeclampsia (Odds ratio:8.20) Incidence of cesarean delivery (Odds ratio:2.69) Shoulder dystocia (Odds ratio:3.14): most common indication for emergency CS in these patients In one study of 117 patients, 62% CS rate in women > 300 lbs Another study of 107 patients found 58% CS rate in women 200-504 lbs Blood loss >1000 ml for cesarean delivery Prolonged duration of surgery Increased incidence of postpartum hemorrhage

14. OBSTETRIC COMPLICATIONS Fetal macrosomia (Odds ratio:3.82): Maternal obesity, diabetes and increased gestational age contributory factors Meconium aspiration (Odds ratio:2.85) Late decelerations (Odds ratio:2.52) Prolonged gestation Dysfunctional labor patterns Twins/breech presentation Fetal umbilical cord accidents Increased incidence of induction of labor due to prolonged gestation High incidence of failed inductions Increased incidence of FTP and prolonged second stage of labor

15. PERINATAL OUTCOME Birth asphyxia and trauma due to shoulder dystocia Instrumental delivery (Odds ratio:1.34) Neonatal death (Odds ratio:3.41) Intrauterine fetal demise (Odds ratio:2.79) Higher pregnancy weight associated with increased risk of late fetal death Increased neural tube defects and other congenital malformations Neonatal hypoglycemia more frequent Increased frequency of neonatal intensive care admissions

16. EPIDURAL ANALGESIA (KEY POINTS) Early insertion of epidural desirable in obese parturients undergoing trial of labor Landmarks invariably difficult to palpate May consider ultrasound guidance for midline bony structures with assistance from obstetrician Small directional errors exaggerated with increasing depth of epidural space Patient can help guide to the midline by telling if she senses pressure from needle advancement to right or left Have extra long needles available if necessary Non functioning epidural should be replaced immediately Catheter should be inserted at least 5 cm in epidural space as risk of catheter displacement high in obese parturients

17. EPIDURAL ANALGESIA (KEY POINTS) Higher incidence of failed epidural, unilateral block and more attempts to identify the space in morbidly obese 94% of obese parturients (>300 lbs) achieved successful analgesia in one study Catheter had to be replaced once in 46% of these patients Two or more times in 21% of these patients May consider a planned wet tap with your epidural needle If one occurs unexpectedly, consider converting to a continuous spinal with dilute local anesthetic and opioid for labor analgesia (usually 2ml/hr of 0.125% bupivacaine with fentanyl optimal) More concentrated local anesthetic for cesarean delivery (1-2 ml of 0.75% bupivacaine with fentanyl and durmaorph) Postdural puncture headache rare in morbidly obese patients

18. EPIDURAL ANALGESIA (KEY POINTS) Lateral sitting or semi recumbent position to minimize airway closure and aortocaval compression O2 administration throughout labor to prevent hypoxemia Epidural decreases O2 consumption and improves oxygenation and prevents increases in cardiac output by inhibiting catecholamine release during labor Optimal titration of local anesthetic can prevent hypotension and excess motor block Epidural advantageous due to frequent need for operative vaginal or cesarean delivery in these patients Can also be used for postoperative pain management CSE not the technique of choice for labor analgesia in obese parturients due to delayed assessment of functionality of the epidural

19. SPINAL ANESTHESIA (KEY POINTS) Negative correlation between the degree of obesity and dose requirement of local anesthetic Higher block may be due to decreased CSF volume (engorged epidural venous plexus), exaggerated curvature of lumbar spine, pelvic fat and hormonal changes of pregnancy High incidence of hypotension following spinal due to higher and variable extension of autonomic blockade in obese patients High block may exaggerate hypoxemia in these patients Single shot spinal disadvantageous due to prolonged surgery in these patients Continuous spinal with epidural catheter may be advantageous in patients for emergent/urgent CS with anticipated difficult airway CSE technique of choice for scheduled/elective CS CSE set with Gertie Marx spinal needle (12.4 cm) may be necessary for some these patients

20. GENERAL ANESTHESIA (KEY POINTS) Increased incidence of complications with GETA The operating room should be prepared with a bed of appropriate width and strength, and wider arm supports and pads Most operating room beds only rated for weights up to 300 lbs The patient should be interviewed early in course of labor or preferably during antepartum visit Consider additional tests during preop visit like CXR, EKG and PFT with ABGs Thorough airway evaluation mandatory Considerable proportion of maternal mortality associated with GETA during cesarean delivery GETA should only be confined to cases where it is indispensable to save mother or fetus Safety of mother of paramount importance and overrides fetal considerations

21. GENERAL ANESTHESIA(KEY POINTS) Consider multimodal aspiration prophylaxis Difficult mask ventilation, laryngoscopy and intubation should be anticipated; however, obesity alone doesn�t predict difficult airway 13% obese patients pose difficulty with intubation 30% obese parturients pose difficulty with intubation Landmarks for block obscure, therefore, consider topical anesthesia of airway with 4% lidocaine Direct laryngoscopy following topical anesthesia can be considered for anticipated difficult airway Obesity+MP IV: Consider fiberoptic intubation Positioning for airway important: the head, neck and shoulder should be raised, there should be straight line between sternal notch and the external auditory meatus and patient should be in reverse trendelenberg position

22. GENERAL ANESTHESIA (KEY POINTS) Rapid sequence induction should not be performed in obese parturients with anticipated difficult airway Patient should be fully denitrogenated with 100% O2 for 3-5 min before rapid sequence induction Additional experienced hands must be available for assistance during administration of GETA Have ancillary airway equipment such as fiberoptic bronchoscope, short handle laryngoscope and an assortment of laryngeal mask airways available Higher FiO2, tidal volumes and PEEP may be required to maintain adequate SaO2 Effect of muscle relaxant during surgery may be overestimated, whereas, reversal effect may be underestimated

23. GENERAL ANESTHESIA (KEY POINTS) Drug doses may be based on actual or ideal body weight Highly lipophilic drugs (barbiturates, benzodiazepines) have considerably increased volume of distribution with higher doses and longer elimination half-lives Non-lipophilic or weakly lipophilic drugs administered based on lean body mass Emergence faster after desflurane than sevoflurane or isoflurane anesthesia and their O2 saturations higher with desflurane in PACU Extubate conservatively and in reverse trendelenburg position The incidence of dangerous postextubation obstruction is �5% in patients with OSA, so extubate with oral or nasal airway in place. If concerned about possible re-intubation, extubate over an airway exchanger

24. POSTOPERATIVE MANAGEMENT Patient should be kept in semi-recumbent or reverse trendelenberg position Continue monitoring for hypoxia and hypoventilation and consider CPAP mask if OSA a problem A monitored or step down bed may be more appropriate location for recovery in the L&D Hospitalization often prolonged Wound dehiscence and infection more common Increased incidence of postoperative pulmonary complications including hypoxemia, atelectasis and pneumonia Vertical abdominal incision more likely to cause hypoxemia Increased risk of deep venous thrombosis and pulmonary thromboembolism-consider anticoagulation soon after surgery with LMWH or unfractionated heparin Adequate postoperative analgesia essential to promote early ambulation and to decrease risk of pulmonary complications

25. CONCLUSIONS Obesity increases the risk of anesthesia related maternal mortality. Airway complications represent the most common cause of anesthesia-related maternal mortality Unlike most parturients, associated co-morbidities complicate management of morbidly obese parturients The obese parturient is at increased risk for fetal macrosomia, shoulder dystocia and cesarean section Early administration of epidural is advisable in obese parturients undergoing trial of labor; a non-functioning epidural should be replaced immediately The anesthetic management requires patience, planning and close collaboration amongst involved physicians

26. SUGGESTED READINGS D�Angelo R, Dewan DD. Obesity in Principles and Practice of Anesthesia, Editor David H Chestnut, Elsevier Mosby, PA. Hawkins JL. Labor and Delivery Management of the Morbidly Obese Parturient. 2005 IARS Meeting Review Course Lectures. Endler GC, Mariona FG, Solok RJ, Stevenson LB. Anesthesia related maternal mortality in Michigan. Am J Obstet Gynecol 1988; 159:187-93.

27. HAVE A GOOD DAY!