Special Topics in Obstetrics PDF

39 Special Topics in Obstetrics CHAPTER OUTLINE „ Intrapartum Fetal Monitoring ▶ Endotoxic Shock ▶ Mechanism of Acquired ▶ Methods of Fetal Monitoring „ Acute Kidney Injury (AKI) Coagulopathy „ Nonreassuring...

39 Special Topics in Obstetrics CHAPTER OUTLINE „ Intrapartum Fetal Monitoring ▶ Endotoxic Shock ▶ Mechanism of Acquired ▶ Methods of Fetal Monitoring „ Acute Kidney Injury (AKI) Coagulopathy „ Nonreassuring Fetal Status (NRFS) ▶ Causes of Acute Kidney Injury ▶ Investigations ▶ Management of Nonreassuring (AKI) ▶ Treatment Fetal Status (NRFS) ▶ Management of AKI in „ High-risk Pregnancy „ Shock in Obstetrics Obstetrics (Prerenal) ▶ Screening of High-risk Cases ▶ Pathophysiology of Shock „ Blood Coagulation Disorders in ▶ Initial Screening ▶ General Changes in Shock Obstetrics ▶ Management of High-risk Cases (with Special Reference to ▶ Normal Blood Coagulation „ Immunology in Obstetrics Hypovolemic Shock) ▶ Physiological Changes in „ Critical Care in Obstetrics ▶ Changes in Endotoxic Shock Pregnancy ▶ Objective Parameters (Selected) ▶ Classification of Shock ▶ Pathological Conditions of for Admission of a Patient „ Management of Shock Acquired Coagulopathy (Nonpregnant) in an ICU ▶ Hemorrhagic Shock INTRAPARTUM FETAL MONITORING METHODS OF FETAL MONITORING By definition, intrapartum fetal monitoring (IFM) A. Clinical B. Biophysical C. Biochemical means simply to watch the fetal condition during CLINICAL: To note the FHR—Intermittent auscultation labor. Goal of IFM is to detect hypoxia in labor and to of FHR using an ordinary stethoscope or a fetoscope initiate management depending upon the severity of or a handheld Doppler can be done to note its rate and hypoxia. Severe hypoxia in labor when associated with rhythm. FHR should be recorded at every 30 minutes metabolic acidosis can cause fetal organ damage or fetal interval initially followed by 15 min intervals in the death. first stage and at about 5 min intervals in the second In between contractions the intraluminal pressure stage. The auscultation should be made for 60 sec par- within the spiral artery (85 mm Hg) is higher than the ticularly before and immediately following a uterine intramyometrial pressure (10 mm Hg) to maintain contraction. the uteroplacental blood flow. During peak uterine Normal fetal heart rate is at an average of 140 beats contractions, myometrial pressure (120 mm Hg) exceeds the arterial pressure (90 mm Hg) causing per minute (bpm) in between contractions with a vari- temporary halting of O2 delivery to the fetus through the ation between 100 and 160 per min (FIGO : 110–150 placenta. Depending upon the intensity and duration of bpm). There may be slowing of FHR during a contrac- contraction, fetal hypoxia may develop. tion (vagal stimulation) which, however, comes back to normal when the contraction passes off. Even in a normal labor, the baby is subjected to stress due to: Limitations 1. Uterine contractions temporarily curtailing the utero- 1. As it is a periodic observation, any transient significant placental circulation. abnormality in between observations is likely to be 2. Cord compression with contractions can cause intermit- overlooked; tent interruption of blood flow and may cause hypoxia. 2. Inherent human error; A healthy fetus can withstand the stress of labor within 3. Difficult, at times, to count the FHR during uterine physiological limits. But in a compromised fetus and/or in contractions or in case of obesity or hydramnios. a pathological state of labor, the fetal distress may appear abruptly. The term ‘Fetal distress’ has been abandoned Evidences of distress in favor of more appropriate term ‘Nonreassuring fetal 1. An increase in FHR to over 160/min or a decrease in rate status’. to less than 100/min (Box 39.1);  Chapter 39 Special Topics in Obstetrics 567 Box 39.1: Causes of Fetal Tachycardia and Bradycardia Causes of Fetal Tachycardia (FHR >160 bpm) Causes of Fetal Bradycardia (FHR 5–25 None or early Present Normal: All four features are Reassuring only egyndegention reassuring Non- 161–180 60 Suspicious: One nonreassuring and bpm, recovering >60 secs OR late Absence of the rest are reassuring decelerations accelerations „Present up to 30 minutes „Occurring ≥50% of contractions with an otherwise Abnormal >180 or 30 min with >50% nonreassuring OR one or more of contractions OR abnormal categories „Bradycardia or a single prolonged deceleration lasting ≥3 minutes  568 Textbook of Obstetrics t Interpretation of the CTG should always be made in the context of clinical picture. Baseline FHR is the mean level of FHR excluding accelerations and decelerations. It is expressed in beats per minute (bpm). Normal baseline FHR is 100–160 bpm. E Baseline variability is the oscillation of baseline FHR excluding the accelerations and decelerations. Variability is the reflex of normal cardiac behavior in response to sympathetic and parasympathetic nerve input. How- ever, parasympathetic (vagus) has the dominant role in modulating variability. Baseline variability may be (A) Absent (B) Minimal (25 bpm) Fig. 39.1: Scalp electrodes Reduced baseline variability is observed in many 1st conditions (Box 39.3). 150pmshouldonly Groused Category I: Normal (baseline rate 110–160 bpm; FHR Acceleration: Transient increase in FHR by 15 variability – moderate; no late or variable deceleration; bpm or more lasting for at least 15 seconds. Prolonged early deceleration ±; acceleration ± acceleration lasts >2 min but 10 min, it is a baseline change. Acceleration denotes Category II: Indeterminate—all tracings not categorized an intact neurohormonal and cardiovascular activity as category I or III. and therefore, a healthy fetus (Fig. 39.3). Category III: Abnormal (either absent baseline FHR Deceleration: Transient decrease in FHR below the variability and any of the following: recurrent late/vari- baseline by 15 bpm or more and lasting ≥15 seconds able decelerations, bradycardia or sinusoidal pattern). (Fig. 39.2). Advantages of EFM over clinical monitoring  Accurate monitoring of uterine contractions.  Significant improvement of perinatal mortality. Can detect hypoxia early and can explain the mecha- nism of hypoxia and its specific treatment.  Improvement of intrapartum fetal death by threefold.  It is an important record for medicolegal purpose (see p. 596). Drawbacks: „ Interpretation is affected by intra- and interobserver error; „ Due to error of interpretation, cesarean section rate (63%) and operative vaginal delivery (15%) are high; „ Instruments are expensive and trained personnel are Fig. 39.2: Graphic representation showing various types of required to interpret a trace; decelerations in relation to uterine contractions „ Mother has to be confined in bed. INTERPRETATION OF A CARDIOTOCOGRAPHY (CTG) iii t Accelerations and normal baseline variability (5–25 bpm) denote a healthy fetus. t Absence of accelerations is of unknown significance. t Absence of accelerations, reduced baseline variability of 90 minutes denotes a hypoxic fetus. mthhlh.EE t Decreased baseline variability may be due to fetal sleep, infection, hypoxia, anomalies or due to maternal medications. seepantectionimpo t Repeated late decelerations increase the risk of low Apgar score and hypoxemia. t Reduced baseline variability, with late or variable deceleration lasting ≥ 3 minutes, increases the risk of hypoxia. Fig. 39.3: Reactive trace with acceleration  onlyearlydeceleration In Chapter 39 Special Topics in Obstetrics 569 Three basic types of deceleration are observed and are it suggests fetal hypoxia/acidosis. It is thought to called early, late and variable (Fig. 39.2). indicate cord compression and may disappear with coincides.net siitonsv „ Early deceleration (Type I Dips), uniform, repetitive the change in position of the patient. It is the most periodic slowing of FHR and, in most cases, the onset, common type. Accelerations often precede and follow nadir and recovery of deceleration coincides with the the deceleration. It is called shoulders. beginning, peak and ending of uterine contraction Prolonged deceleration is the abrupt decrease in FHR ompnession respectively. It is due to head compression (vagal nerve (>15 bpm) to levels below the baseline and it lasts >3 min activation) (Fig. 39.2). It is usually benign in nature. „ Late deceleration (Type II Dips), uniform, U shaped 0 baseline change. 0 but 10 min, it is a with reduced variability within the deceleration segment Lag period: It is the time taken for the FHR to reach the nadir (the lowest point of the FHR dip) from the and with repetitive periodic slowing of FHR. It begins >20 sec. after the onset of the uterine contraction. Usually, 0 apex of the preceding uterine contraction (Fig. 39.2). In the onset, nadir and recovery of the deceleration occur deceleration lag period is > 30 seconds. after the start, peak and end of the uterine contraction Sinusoidal pattern: It resembles a sine wave. It has respectively. Nadir occurs 20 seconds after the peak a stable baseline FHR with fixed or absent baseline vari- a of the contraction (acme) and FHR returns to normal ability lasting >30 min. Accelerations are absent. It is after the contraction is over. It suggests uteroplacental often associated with fetal anemia, fetomaternal hemor- insufficiency (Fig. 39.4) and fetal hypoxia (50%). rhage, vasa previa, fetal hypoxia (acidosis). It may occur when narcotics are given to mother (Fig. 39.5). Such FHR „ Causes of late deceleration: i. Placental pathology (postmaturity, hypertension, a showing ‘sawtoothed’ pattern are called pseudosinusoi- dal as the fetus is well-oxygenated. diabetes, placental abruption); C. Induced fetal stimulation and FHR accelerations: ii. Excessive uterine contractions; Any FHR acceleration spontaneous or induced, indicates iii. Injudicious use of oxytocin; the absence of fetal acidosis. iv. Regional anesthesia (spinal or epidural). Vibroacoustic stimulation (VAS) of the fetus is done using an electronic larynx placed on the maternal I „ Variable deceleration: It is the intermittent periodic slowing (variable) of FHR (V shaped) with rapid onset abdomen. Presence of FHR accelerations indicates normal blood pH. and recovery (Fig. 39.2). Decelerations are variable in Fetal scalp stimulation by pinching with an Allis all respect of size, shape, depth, duration and timing forceps or by gentle digital stroke is done before to the uterine contractions. When it is ‘U’ shaped scalp blood pH test. Presence of FHR accelerations is 50 with reduced variability and/or duration ≥ 3 minutes, associated with normal scalp blood pH. Fio Admission CTG is a CTG trace done for a woman on admission in the labor ward. Admission CTG is poor in predicting fetal compromises in labor. Routine admission CTG testing is not recommended in low-risk women. Fig. 39.4: Persistent late deceleration with loss of variability Box: 39.3: Factors to Cause FHR Changes Factors to Cause Diminished Fetal Heart Variability Factors (Maternal/Fetal) to Alter FHR Not Related to Oxygenation „ Maternal Medications „ Fetal Conditions Factor (s) Alteration in FHR t Pethidine t Prematurity Infections Tachycardia, ↓Variability t Tranquilizers t Sleep cycle Prematurity Tachycardia, ↓Variability t Corticosteroids t Anemia Fetal anemia Sinusoidal pattern, tachycardia t Atropine t Metabolic acidemia Fetal sleep ↓Variability, ↓Accelerations t General anesthesia t Congenital malformations Heart block ↓Variability, bradycardia 570 Textbook of Obstetrics ii. Maternal infection (HIV, hepatitis or herpes simplex virus), iii. Fetal coagulation disorders, iv. Prematurity (7.25). epidural analgesia) with immediate infusion of 1 liter These patients need to be evaluated (continuous or of crystalloid (Ringer’s solution). intermittent) as required to exclude acidosis. Labor „ Stoppage of oxytocin to improve fetal oxygenation. progress is to be monitored also. A decline in pH on Fetal hypoxia may be due to strong and sustained successive pH estimations that points towards the uterine contractions. With reassuring FHR and in likelihood of acidosis before the cervix is fully dilated absence of fetal acidemia, oxytocin may be restarted. is an indication for delivery. It is preferably done by „ Tocolytic (Injection terbutaline 0.25 mg SC) is given cesarean section. when uterus is hypertonus and there is nonreassuring B. Persistence of nonreassuring pattern or presence of FHR. Tocolytics increase oxygen to the fetus. unusual or confusing pattern: these patients need „ To avoid sustained pushing in the second stage of labor. immediate delivery.