Anesthesia for Obstetrics

Miller Anesthesia, Chapter 57

1. List the changes that occur in these maternal respiratory parameters at term:

• Total Lung Capacity
• Vital Capacity
• Inspiratory Capacity
• Expiratory Reserve Volume
• Residual Volume
• Functional Residual Capacity
• Closing Volume
• Minute Ventilation
• Oxygen Consumption

2. You are providing anesthesia for emergent ORIF of a femoral fracture resulting from an MVA. Your patient is a 23 year-old gravida 1 para 0000 female in her late 34th week of gestation. The patient has been thoroughly evaluated and has no other injuries. You are monitoring fetal heart tones and all is going well. To closely monitor the patient's blood pressure and respiratory function, your colleagues in the ER have placed an A-line. The following initial ABG obtained after induction to assess positive pressure ventilation: pH = 7.39, PCO2 = 29, PO2 = 420, HCO3 = 21 on an FIO2 of 60%. Should this ABG concern you or reassure you? Will you change the patient's minute ventilation? Are there any significant risks associated with hypocarbia in this otherwise healthy, young woman?

3. You are anesthetizing a 26 year old 110 kg gravida 1 para 0000 female for cesarean section for fetal distress. Describe your anesthetic plan-what will you do, step by step, and why?

4. After preoxygenation and surgical prep, you induce the patient in #3. As your assistant holds cricoid pressure you attempt to intubate. It takes several seconds to place the laryngoscope because of the obstruction produced by the patient's chest wall. As you begin to search for the epiglottis and cords, you hear the pulse oximeter tone start to sag. You are sure that no more that 20-30 seconds have passed. Why is the patient inclined to desaturate so quickly? Why is she hard to intubate? Assuming you cannot (heaven help us all) intubate, what will be your next move?

5. List the cardiovascular changes that occur during pregnancy, labor and delivery, and post partum:

6. You are asked to provide labor analgesia for a 16 year-old primip who has been in labor for 15 hours (active labor for approximately 3 hours) and who is to receive pitocin augmentation. Despite the patient's wailing insistence that you should "get the @##@%@$^!*&^ thing in," you do a brief preop evaluation and obtain informed consent (sort of). During that time you give a 1000 cc IV infusion of LR. All goes well with epidural placement once you manage to convince the patient that she must remain very still during needle placement ant introduction of the catheter. After securing the catheter and negative test dose, you position the patient supine with the head of the bed at ~20 degrees with the hope of obtaining optimal spread of the anesthetic agent. As you begin to inject an initial bolus of 0.25% bupivacaine (4cc), the patient's blood pressure drops to 80/40, fetal heart tones fall below 100, and the patient becomes somewhat obtunded. What will you do first to treat this problem? Next? After that? What is the most likely cause of the problem?

7. True or false? Because of decreased hemoglobin levels, oxygen transport to important organs decreases during pregnancy.

8. Pregnant women at term are Hyper- or Hypo-coagulable? List typical blood losses for normal vaginal delivery and C-section.

9. True or false? In pregnancy, hepatic blood flow is reduced; however, levels of plasmacholinesterase remain high and there is no reason to alter succinylcholine dosing for rapid sequence induction.

10. You are asked to provide anesthesia for ORIF of an open tib-fib fracture in a 21 year-old multip at 34 weeks gestation. She categorically refuses regional anesthesia. She has been NPO for 10 hours. Will you perform a rapid sequence induction. Why/Why not?

11. A 26 year old primip who is a national level distance runner steps in a hole while training and suffers an anterior cruciate tear. She presents in her 13 week of gestation for arthroscopy and ACL reconstruction. She requests a spinal anesthetic. Will you alter your usual dose of local anesthetic for this spinal? Why/Why not?

12. During your preop evaluation of the patient in #11, you note that a zealous intern has obtained extensive lab work, including coags, CBC and a complete set of electrolytes. You notice that the patient's BUN and creatinine are slightly higher than the lab's upper limits of normal. Is this a matter for concern?

13. Which of the following vasopressors does not decrease uterine blood flow?

• Phenylephrine
• Methoxamine
• Epinephrine
• Mephentermine
• Ephedrine

14. To provide analgesia for the late stages of labor and delivery, you have administered a "sitting dose" of local anesthetic to a patient with an epidural. Anticipating a relatively timely delivery, you discontinue the epidural infusion you have been running during the earlier portion of her labor. Roughly 40 minutes of active pushing ensues and you are summoned because the patient is complaining of pain with contractions. She denies perineal pain, despite the fact that the baby's caput is visible at the introitus during contractions. What spinal segments are no longer adequately blocked if the patient is having pain with contractions? What segments must still be adequately blocked if she has no perineal pain?

15. You are asked to provide anesthesia for an urgent C-section for a patient originally admitted for preterm labor. The parturient has been hospitalized for nearly 10 days on MgSO4. Because of the urgency of the situation, you elect to perform a general anesthetic with a rapid sequence induction. The surgical procedure goes very well, and the patient is delivered of a 3200 gm infant 5 minutes after skin incision and 40 seconds after uterine incision. The infant appears normal in all regards except that is quite "floppy" and remains so even at more than 5 minutes post partum. The medical student assisting the neonatologist wonders aloud if the succinylcholine you used could have caused this problem? What is your response? As closure of the mother's surgical wounds proceeds, the surgeons ask for additional relaxation. How will you comply with this request?

16. True or false? Neonates have reduced hepatic enzyme activity and a significantly limited ability to metabolize local anesthetics and other agents.

17. You are obtaining informed consent from a patient for placement of a labor epidural. As you complete your review of the risks and benefits of the procedure, the expectant mother asks whether the procedure represents any risk to her baby. What do you tell her?

18. What advantages/disadvantages for the parturient and fetus might be associated with the following medications:

• Diazepam:
• Midazolam:
• Meperidine:
• Fentanyl:

19. You are called for an emergent C-section for a patient with an abruption. When you arrive the parturient has a BP of 80/40, a heart rate of 140, and is arousable but confused. Fetal heart tones are depressed. The obstetrician is deeply concerned about the fetus and is insisting that you induce anesthesia immediately. You are also very concerned about both your patients. Describe your anesthetic plan.

20. You are asked to provide anesthesia for an urgent C-section in a patient with severe preeclampsia. Her blood pressures have been 170's/110's. She has been oliguric for the past 5 hours. Recent lab work shows significant proteinuria and hemoglobinuria. Platelet count is 55,000. LFT's are elevated. Describe your primary concerns and anesthetic plans for this patient.

21. Shortly after induction of anesthesia for the patient in #20, her blood pressure drops to 90/50. How will you treat this (if at all)?

22. True or false? Anesthetic agents present significant risks for patients undergoing surgery during the first trimester of pregnancy.