CRNA Certified Registered Nurse Anesthetist Principles 4: OB anesthesia Exam Review

CRNA Certified Registered Nurse Anesthetist Principles 4: OB anesthesia Exam Review CRNA Certified Registered Nurse Anesthetist Principles 4: OB anesthesia Exam Review How should you look at the full stomach status of a parturient?** @ 12 weeks always considered full stomach What are the top 2 causes of maternal mortality? 1. Hemorrhage 2. Pre-eclampsia Why is there an overall decrease in maternal mortality from anesthesia (1.2% of live births)** 1. greater use of regional anesthesia for labor and C/S 2. most deahts occur during or after C/S Where is adverse outcomes greater in anesthesia mortality? Emergent C/S What is the #1 thing you can be sued for in OB? Maternal nerve damage (local anesthetics cause nerve damage) When does an increase in maternal intravascular fluid volume begin? First trimester How much does plasma volume & erythrocyte volume increase?** Plasma volume - 45% Erythrocyte - 20 % (plasma volume increase more than RBC = appear to be anemic) Why does anemia result in pregnancy?** Increase in plasma volume relative to RBC volume: 31/9-36.5% At term what is the average expansion of intravascular volume? 1500 ml What is the purpose of an increased intravascular fluid volume in pregnancy? Offsets average blood loss with delivery How can you increase cardiac output? Increase Stroke Volume Increase HR What is the increased CO in pregnancy primarily due to?** increased SV (preload) How much does CO increase by the tenth week of pregnancy? 10% In the third trimester how much has CO increased 40% above normal How much does labor increase CO? 30% above pre-labor value When is the largest increase in CO seen in pregnancy?** Immediately after delivery (as much as 80% above pre-labor value) When does CO return back to normal?** 14 days after delivery During pregnancy does SVR increase or decrease? Decreases 15% to offset increase in CO/IVF What is the effect of a decrease in SVR during pregnancy? Arterial BP remains normal to decrease during a normal pregnancy (uncomplicated) Which BP will decrease more during pregnancy systolic or diastolic Diastolic - 10-20 mmHg (systolic and diastolic both decrease, but diastolic more) What CV changes in pregnancy increase and by how much?** Blood volume: 35% Plasma Volume: 45% Cardiac output: 40-50% Stroke Volume: 30% Heart Rate: 15-25% What CV changes in pregnancy decrease and by how much?** Peripheral resistance (SVR): 15-20% What happens to CVP in pregnancy?** No change CV changes pregnancy Table CV changes and AneSthetic Significance Table Why is a maternal BP of 90-95mmHg a concern while administering regional anesthesia?** May be associated with decrease in uterine blood flow Why do supine parturients with T4 sympathectomy develop significant hypotension? Aortocaval compression! Hemodynamic changes in pregnancy by trimester table What happens to minute ventilation in pregnancy?** Increased 50% Why does MV increase in pregnancy? Increased progesterone in first trimester then throughout pregnancy (Increase TV 40% & RR 15%) What happens to resting PaCO2 in pregnancy? decreases What happens to arterial ph during pregnancy and why?** Remains near normal due to INCREASED RENAL EXCRETION OF BICARB (remember resting PaCO2 decreases) What happens to FRC during pregnancy?** decreases 20% at term When does FRC begin to change in pregnancy? around the third month due to an enlarged uterus displaces diaphragm cephalad Why is a decrease in FRC relevant in anesthesia?** Induction, emergence * changes in depth are more RAPID in parturients What law of physics describes FRC Boyles Law - Pressure and volume are indirect - measured indirectly through body plysmography What happens to lung compliance during pregnancy? Does not change What happens to airway resistance during pregnancy? DECREASES because progesterone induces bronchiolar smooth muscle relaxation What happens to dead space during pregnancy? Does not change What happens to total lung capacity during pregnancy? Unchanged or decrease 5% depends on source What happens to the upper airway in pregnancy?** Capillary engorgement mucosal lining** Weight gain, short neck, large breasts Due to capillary engorgement what are the implications for anesthesia on airway management?* 1. Selected a smaller cuffed tracheal tube (6.0-7.0)** 2. gentle instrumentation 3. avoid nasal airways 4. difficulty inserting laryngoscope What happens to MAC during pregnancy?** Decreases 40% What does a decrease in FRC cause in the pregnant? Faster inhalation induction How does increased MV affect induction in parturient speeds inhalation induction What happens to your oxygen reserve with decreased FRC? It decresases How does oxygen consumption change in pregnancy? Increases by 33% What happens to arterial oxygenation early in gestation PaO2 >100 mmHg (hyperventilation) Later in gestation what happens to PaO@? normal/decreased due to airway closure Induction of anesthesia may be associated with marked _________________ in PaO2 decreases What is the treatment of a decrease in PaO2 before induction?** Preoxygenation What parameters of the respiratory system increase during pregnancy 1. O2 Consumption: 20-50% 2. Minute ventilation: 50% 3. Tidal Volume: 40% 4. Respiratory Rate: 15% 5. PaO2: 10% What parameters of the respiratory system decrease during pregnancy 1. FRC: 20% 2. PaCO2: 15% 3. HCO3: 15% Respiratory volumes in pregnancy summary picture How much does serum bicarbonate decrease in pregnancy?** 4mEq/L What happens to expiratory reserve volume, residual volume and functional residual capacity in pregnancy?** All decrease by 20% Respiratory Anesthetic Significance Summary Increase in progesterone levels do what to the nervous system and MAC requirements in pregnancy? Sedative effects Mac requirements decreased for volatile anethetics What happens to the size of the epidural space in pregnancy?** Decreased What happens to the size of epidural space in pregnancy?** Decreased What happens to the volume in CSF and dose requirements of local anesthetics in pregnancy?** Decreased volume CSF (30-80) Decrease dose requirements of local anesthetics Does a decrease in plasma cholinesterase activity prolong succs? NO! What are 2 changes in the hepatic system during pregnancy?** 1. Plasma cholinesterase: decrease 25%, 10th wk- 6 wk postpartum 2.* Plasma coagulation factors are increased: hyper coagulable state* What clotting factor is increased the most in pregnancy? Factor 8 What 2 hematologic changes decrease in pregnancy? 1. Hbg decreases 20% 2. Platelets decrease 10-20% What hematologic factor increases in pregnancy? 1. Clotting factors: 50-500% What renal system increases in pregnancy? GFR increases 50% What happens to gastric fluid volume and ph in pregnancy?** UNCHANGED What causes an increased risk of aspiration in the pregnant?** Incompetence of the LES = gastric fluid reflux and esophagitis Why would you give sodium citrate to a laboring patient? Increases gastric pH Why would you give metoclopramide to a laboring patient? Decreases gastric volume How long does and H2 blocker increase gastric pH 30 minutes Describe placental circulation 1. Two umbilical arteries: deliver fetal blood to placenta 2. One umbilical vein: deliver nutrient rich, waste free blood to the fetus What is the job of the uterine arteries Delivers maternal blood to the placneta What is responsible for delivering fetal blood to the placenta? 2 umbilical ARTERIES What is responsible for delivering nutrient-rich, waste free blood to the fetus? One umbilical VEIN What will decrease uterine arterial pressure?** 1. supine position (aortocaval compression) 2. hemoorrage/hypovolemia 3. drug induced hypotension Is uterine blood flow auto regulated?** NO!! What is uterine blood flow directly proportional to the mean perfusion pressure across the uterus What is uterine blood flow inversely proportional to? uterine vascular resistance Uterine blood flow = (Uterine arterial-Uterine venous pressure)/Uterine vascular resistance What SBP do you want to maintain to maintain uterine blood flow?** SBP >98 mmHg What are causes of increased uterine vascular resistance?** 1. Maternal stress or pain = endogenous catecholamine release 2. uterine contractions through increased uterine venous pressure What is supine hypotension syndrome caused by?** aortocaval compression: gravid uterus compresses the IVC in supine position or abdominal aorta What happens in aortocaval compression to CO and BP? Decreased CO Decreased systemic BP (Venous return decreases from IVC compression) What happens to urteroplacental blood flow during supine hypotension syndrome Decreases (Arterial flow decreased from aortic compression) What positioning will relieve aortocaval compression? 1. Full Left or Right lateral 2. elevating mothers right hip 10-15 cm completely relieves in 58% of term parturients What is the treatment for hypotension due to aortocaval compression?** 1. Lateral positioning 2. Left uterine displacement What is currently the drug of choice for treatment of hypotension in the parturient?** Ephedrine (neosynephrine might be drug of choice now though) Why is ephedrine the drug of choice for treatment of hypotension in parturient? Not associated with significant decreases in uterine blood flow despite drug-induced increases in maternal arterial blood pressure What 3 things tell you about the progress of labor? 1. increasing cervical dilation 2. effacement of cervix 3. descent of fetal presenting part through the vagina with time (+4 = crowning) What nerves should be blocked in the first stage of labor? T10-L1 (epidural works well) During stage 2 of labor what may you need to do? Increase dose of epidural (worry about affecting motor but need to numb sciatic nerves) What signals the first stage of labor? Regular contractions How is pain carried during the first stage of labor and what dermatome levels? Visceral afferent fibers T10-L1 What begins the second stage of labor? complete dilation of the cervix and ends with the delivery; of the infant What fibers provide pain during the second stage of labor and what dermatome level is it? Somatic afferent = stretching of birth canal, vulva, perineum S2, S3, S4 When is the third stage of labor? Delivery of baby to placenta is expelled What causes the pain in the first stage of labor:? Uterine contractions Dilation of cervix What type of fibers cause pain during the stretching of the vagina and perineum by descent of the fetus Somatic What are the benefits of regional anesthesia in L&D Decreased risk of fetal drug depression Decreased risk of maternal aspiration Should not influence progress of labor Should not diminish the parturient ability to bear down during the second stage of labor What is the goal of lumbar epidural anesthesia during the first stage of labor?** To achieve segmental bands of analgesia T10-L1 during the first stage of labor What is the goal of lumbar epidural anesthesia during the second stage of labor? Ability to extend block to include S2-S4 segments Once an epidural catheter is placed this is your test dose to make sure you are not intrathecal or intravascular ** 3-5 ml of 1.5% lidocaine with 1:200,000 epi If you are intrathecal or intravascular how much will your heart rate increase after the test dose? 30 beats 20% within 30-60 sec How often are maternal BP/HR monitored when they have an epidural? Q3-5 min for 15-20 minutes Then every 15 minutes thereafter What are 2 local anesthetics used in an epidural Ropivicaine (Naropin) 2% plain Bupivicaine (Marcaine, Sensorcaine, Exparel) 5-10 ml (0.0625-0.125% with 2 mcg of fentanyl per ml and 1:200,000 epi) What is the benefit of using bupivicaine with fentanyl and epi in an epidural Motor sparing block Long duration of action How can you avoid hypotension in an epidural? 1. adequate volume expansion 2. proper positioning How long should you wait after giving an epidural test dose to see changes?** 5 minutes What are the advantages of a combined spinal and epidural? 1. Reliablity 2. Rapid onset of analgesia 3. Very effective when administering late, rapidly progressing labor 4. minimal motor blcokade (may permit ambulation in early labor) What are the disadvantages of combined spinal epidural?** 1. more invasive 2. increased incidence of PDPH When will you administer a spinal during labor and delivery? Immediately prior to vaginal delivery (produces rapid onset of analgesia and skeletal muscle relaxation) What gauge spinal needle is used to decrease the risk of PDPH? 25-27 gauge What stage of labor can you do a paracervical block?** First stage only What is a paracervical block?** LA is injected in the submucosa of the fonix of the vagina lateral to the cervix What is the risk of a paracervical block** High incidence of fetal bradycardia When would you give a pudendal nerve block?** 2nd stage of labor Where are the pudendal nerves?** Lower sacral nerve S2-S4 What areas do the lower sacral nerve roots of S2-S4 provide sensation to?** 1. vaginal vault 2. perineum 3. rectum 4. Parts of bladder What are the indications for a C/S 1. fetal distress 2. cephalopelvic disproportion 3. malpresentations 4. failure of labor to progress This type of deceleration is slowing of the FHR that begins with the onset of uterine contractions and is usually caused by head compression Early decelerations What type of decelerations are not indicative of fetal distress? Early decelerations This type of deceleration is slowing of the FHR that beings 10-30 seconds after the onset of the uterine contraction and reflects hypoxia associated with fetal distress Late decelerations These are deceleration patterns are variable in magnitude, duration, and time of onset, caused by umbilical cord compressions, unless prolonged beyond 30-60 seconds associated with fetal bradycardia for 30 minutes, they are usually benign Variable decelerations What sensory level of anesthesia do you want for C/S T4 What is the benefit of a lumbar epidural for C/S? Sensory level more likely to be controlled Maternal hypotension less likely May be redosed if needed PDPH does not occur When do you use GA for C/S emergency Use RSI with cricoid For GA with C/S when do you extubate? when patient is fully awake mac <0.1 Steps of GA for C/S ** 1. thiopental (3mg/kg) or propofol 1-2mg/kg 2. succinylcholine 1-2 mg/kg 3. maintenance with 50% nitrous and 0.5 MAC of volatile 4. extubate with patient awake 5. antiobiotic to OB operating room ** 6. Oxytocin 10-40 units IV infusion after placenta delivery**( NEVER IV PUSH PUT IN 500 CC BAG) What is the typical blood loss in C/s? 750-1000 ml What are the normal fetal positions for delivery Occiput Transverse Occiput Anterior What is the problem with persistent occiput posterior presentation? Prolonged and painful labor Severe back pain = pressure on sacral never by occiput This position is associated with increased maternal and neonatal morbidity Breech What is the method of choice for anesthesia in a multiple gestation vaginal delivery? Continuous epidural What is the danger of increased CO during pregnancy and heart disease May result in CHF in parturients with co-existing heart disease What can help minimize the adverse effects of increased cardiac output? Continuous lumbar epidural When does pre-eclamsia normally manifest?** 20th week What are the characteristics of pre-eclampsia?** 1. Hypertension (>140/90 mmHg) 2. Proteinuria (more than 5 g/day (or 0.05 hard to tell in notes) 3. Generalized edema 4. Headache What is a severe form of pre-eclampsia characterized by hemolysis, elevated liver enzymes, and low platelet count HELLP When does pre-eclampsia usually end? within 48 hours following delivery When do you get eclampsia When seizures are superimposed on pre-eclampsia How often does eclampsia develop 5% of parturients who develop pre-eclamsia What is the mortality rate with eclampsia 10% What is the definitive treatment of eclampsia? Delivery of fetus & Placenta Magnesium and antihypertensive (prior to delivery) What is a tocolytic agent?** Magnesium 1. decreases irritability of the central nervous system 2. inhibits release of acetylcholine from motor nerve terminals 3. relaxes uterine and vascular smooth muscle increasing uterine blood flow What is the therapeutic range for magnesium? 4-6 mEq/L How will you know that your Mag is too high Loss of tendon reflexes At what BP would you administer an antihypertensive and what are the most commonly administered ones? Diastolic >110 mmHg Hydralazine Labetaolol Can you give someone with pre-eclamsia an epidural? YES - do coagulation studies first though What are the major causes of hemorrhage in the third trimester?** Placenta Previa abrupto placentae What is uncontrolled hemorrhage that occurs during labor? Uterine rupture Why might postpartum hemorrhage occur 1. retained placenta 2. uterine atony 3. lacerations involving the cervix and/or vagina What is it called when you have abnormally low implantation of the placenta in the uterus? Placenta previa What is the cardinal symptom of placenta previa?** Painless vaginal bleeding that manifest around the 32nd week of gestation (Neonates are likely to be acidotic and hypovolemic) What are the 3 locations of placenta previa? 1. marginal 2. complete 3. low-lying What are the classification of Accretas? Accreta - chorionic villi attach to the myometrium Increta - chorionic villi invade into the myometrium.: Percreta - chorionic villi invade through the myometrium, Increased risk of heavy bleeding. The need for transfusion of blood products is frequent, and hysterectomy is sometimes required to control life-threatening hemorrhage. This is the separation of a normally implanted placenta after 20 weeks gestation? Abruptio placentae If you have severe and painful hemorrhage with abrupt placentae what needs to happen? Emergent C/S with GA What are the possible causes of uterine rupture 1. separation of a previous C/S healed incision 2. rapid spontaneous delivery 3. excessive oxytocin stimulation Are most of uterine ruptures attributed to a certain cause? NO - more than 80% are spontaneous and without an obvious explanation How often is retaining a placenta? 1% - usually necessitates manual exploration of the uterus When can uterine atony occur? immediately after delivery or within several hours What is the most common cause of postpartum hemorrhage?** Uterine Atony What is the common accompaniment of uterine atony? Retained placenta How do you treat uterine atony? Synthetic oxytocins (oxytocin, Methylergonovine, Prostaglandins) Parameters that normally decrease during pregnancy summary Plt count, Pulmonary vascular resistance, Peripheral vascular resistance, hemoglobin content mg/dl, systolic BP, functional residual capacity