1. Electrolyte, calcium, and magnesium levels. 2. Blood gas levels may reveal acidosis or hypoxia. 3. Drug levels to evaluate for toxicity. a. Digoxin. Normal serum levels are 0.5-2.0 ng/mL (sometimes up to 4 ng/mL). Elevated levels of digoxin alone are not diagnostic of toxicity; clinical and ECG findings consistent with toxicity are also needed, and many neonates have naturally occurring substances that interfere with the radioimmunoassay test for digoxin. b. Quinidine. Normal serum levels are 3-7 mg/mL. Toxicity is associated with levels >7 mg/ mL. c. Theophylline. Normal levels are 4-12 ug/mL. Toxicity is associated with levels >15-20 ug/ mL. C. Radiologic and other studies 1. ECG. Full ECG evaluation should be performed in all infants who have an abnormal ECG tracing that lasts >15 s or is not related to a benign condition. Diagnostic features of the common arrhythmias are listed next. a. SVT (see Figure 30-1 A) i. A ventricular rate of 180-300 beats/min. ii. No change in heart rate with activity or crying. iii. An abnormal P wave or PR interval. iv. A fixed R-R interval. b. Atrial flutter i. The atrial rate is 220-400 beats/min. ii. A sawtooth configuration seen best in leads V 1 -V 3 , but often difficult to identify when a 2:1 block or rapid ventricular rate is present. iii. The QRS complex is usually normal. c. Atrial fibrillation i. Irregular atrial waves that vary in size and shape from beat to beat. ii. The atrial rate is 350-600 beats/min. iii. The QRS complex is normal, but ventricular response is irregular. d. Wolff-Parkinson-White syndrome (see Figure 30-1 B) i. A short PR interval. ii. A widened QRS complex. iii. Presence of a delta wave. e. Ventricular tachycardia i. Ventricular premature beats at a rate of 120-200 beats/min. ii. A widened QRS complex. f. Ectopic beats i. An abnormal P wave. ii. A widened QRS complex. g. AV block i. First-degree block (a) A prolonged PR interval (normal range, 0.08-0.12 s). (b) Normal sinus rhythm. (c) A normal QRS complex. ii. Second-degree block (a) Mobitz type I • A prolonged PR interval with a dropped ventricular beat. • A normal QRS complex. (b) Mobitz type II. A constant PR interval with dropped ventricular beats. iii. Third-degree block (a) A regular atrial beat. (b) A slower ventricular rate. (c) Independent atrial and ventricular beats. (d) The atrial rate increases with crying and level of activity. The ventricular rate usually stays the same. h. Hyperkalemia i. Tall, tented T waves. ii. A widened QRS complex. iii. A flat and wide P wave. iv. Ventricular fibrillation and late asystole. i. Hypokalemia i. Prolonged QT and PR intervals. ii. A depressed ST segment. iii. A flat T wave. j. Hypocalcemia. A prolonged QT interval. k. Hypercalcemia. A shortened QT interval. l. Hypomagnesemia. Same as for hyperkalemia. m. Hyponatremia i. A short QT interval. ii. Increased duration of the QRS complex. n. Hypernatremia i. A prolonged QT interval. ii. Decreased duration of the QRS complex. o. Metabolic acidosis i. Prolonged PR and QRS intervals. ii. Increased amplitude of the P wave. iii. Tall, peaked T waves. p. Metabolic alkalosis. An inverted T wave. q. Digoxin i. Therapeutic levels: A prolonged PR interval and a short QT interval. ii. Toxic levels: Most common are sinoatrial block, second-degree AV block, and multiple ectopic beats; also seen are AV block and bradycardia. r. Quinidine i. Therapeutic levels: prolonged PR and QT intervals, a decreased amplitude of P wave, and a widened QRS complex. ii. Toxic levels: a prolonged PR interval, a prolonged QRS complex, AV block, and multifocal ventricular premature beats. s. Theophylline i. Therapeutic levels: no effect. ii. Toxic levels: tachycardia and conduction abnormality. 2. Chest x-ray studies should be obtained in all infants with suspected heart failure or air leak. V. Plan A. General management. First, decide whether the arrhythmia is benign or pathologic, as noted previously. If it is pathologic, full ECG evaluation must be performed. Any acid-base disorder, hypoxia, or electrolyte abnormality needs to be corrected. B. Specific management 1. Heart rate abnormalities a. Tachycardia i. Benign. No treatment is necessary because the tachycardia is usually secondary to a self- limited event. ii. Medications. With certain medications, such as theophylline, you can order a serum drug level to determine whether it is in the toxic range. If it is, lowering the dosage may restore normal rhythm. Otherwise, a decision must be made to accept the tachycardia, if the medication is needed, or to discontinue the drug. iii. Pathologic conditions. The underlying disease should be treated. b. Bradycardia i. Benign. No treatment is usually necessary. ii. Drug-related. Check the serum drug level if possible, and then consider lowering the dosage or discontinuing the drug unless it is necessary. iii. Pathologic (a) Treat the underlying disease. (b) In severe hypotension or cardiac arrest, check the airway and initiate breathing and cardiac compressions. (c) Administer atropine, epinephrine, or isoproterenol to restore normal rhythm. (For dosages, see Chapter 80.) 2. Arrhythmias. For dosages of drugs mentioned next and for other pharmacologic information, see Chapter 80; for the technique of cardioversion, see section VI. a. Benign. Only observation (no other treatment) is indicated. b. Pathologic. Treat any underlying acid-base disorders, hypoxia, or electrolyte abnormalities. i. SVT (a) If the infant's condition is critical, electrical cardioversion is indicated, with digoxin started for maintenance therapy. (b) If the infant's condition is stable, vagal stimulation (an ice-cold washcloth applied to the infant's face for a few seconds) can be tried. Adenosine (100 ug/kg), by quick push into a central vein, will convert SVT to sinus rhythm. It may be necessary to double the dose (200 ug/kg). The maximum dose is 300 ug/kg. Never use verapamil in infants. Digoxin should be started as a maintenance drug. Another drug that may be used instead of or in addition to digoxin is propranolol. SVT refractory to digoxin and propranolol may be treated with flecainide or amiodarone. ii. Atrial flutter (a) If the infant's condition is critical (severe congestive heart failure or unstable hemodynamic state), perform electrical cardioversion, with digoxin started for maintenance therapy. (b) If the infant is stable, start digoxin, which slows the ventricular rate. A combination of digoxin and propranolol may be used instead of digoxin alone. iii. Recurrent atrial flutter. Management is the same as that for atrial flutter. iv. Atrial fibrillation. Management is the same as that for atrial flutter. v. Wolff-Parkinson-White syndrome. Treat any symptomatic arrhythmias that may occur. (It is accompanied by a high incidence of SVT.) vi. Ventricular tachycardia. Perform electrical cardioversion (except in digitalis toxicity), with lidocaine started for maintenance therapy. Although lidocaine is the drug of choice, other drugs that may be used are procainamide or phenytoin. 3. Ectopic beats a. Asymptomatic. No treatment is necessary. b. Symptomatic. With underlying heart disease with ectopic beats that are compromising cardiac output, suppress with phenytoin, propranolol, or quinidine. 4. AV block a. First-degree. No specific treatment is usually necessary. b. Second-degree. Treat the underlying cause. c. Third-degree (complete). If the infant is asymptomatic, only observation is necessary. Occasionally, the rate is low enough that transvenous pacing is necessary on an urgent basis, with the need for subsequent permanent pacing. Generally, if the rate is ≥70 beats/min, no problems develop. If the rate is <50 beats/min, the patient usually needs a pacemaker. Between 50 and 70 beats/min is the gray zone. Check the mother for antinuclear antibodies because there is an association with complete heart block. 5. Arrhythmias secondary to an extracardiac cause a. Pathologic conditions. Treat the underlying disease. b. Digoxin toxicity. Check the PR interval before each dose, obtain a stat serum digoxin level, and hold the dose. Consider digoxin immune Fab (Digibind) (see Chapter 80). c. Quinidine toxicity. Discontinue medication. d. Theophylline toxicity. Reduce the dosage or discontinue medication. 6. Electrolyte abnormalities a. Check serum electrolyte levels with repeat determinations. b. Treat electrolyte abnormalities accordingly (see Chapter 7). VI. Technique of cardioversion. Place the paddles at the apex (left lower chest in the fifth intercostal space in the anterior axillary line) and the base of the heart (right of the midline below the clavicle). Place a saline-soaked gauze pad beneath each paddle to ensure good electrical conduction. The dose is 1-4 J/kg, which should be increased 50-100% each time an electrical charge is delivered. When cardioversion is used for infants with ventricular fibrillation, the synchronization switch should be off. REFERENCES Flanagan M et al: Cardiac disease. In Avery GB et al (eds): Neonatology, 5th ed. Lippincott, Williams & Wilkins, l999. Garson A: Medicolegal problems in the management of cardiac arrhythmias in children. Pediatrics 1987;79:84. Lerman B, Belardinelli L: Cardiac electrophysiology of adenosine. Circulation 1991;8:1499. Nagashima M et al: Cardiac arrhythmias in healthy children revealed by 24-hour ambulatory ECG monitoring. Pediatr Cardiol 1987;8:103. Southall R, Johnson B: Frequency and outcome of disorders of cardiac rhythm and conduction in a population of newborn infants. Pediatrics 1981;68:58. CHAPTER 31. Bloody Stool PROBLEM OUTLINE I. Problem. A newborn infant has passed a bloody stool. II. Immediate questions A. Is it grossly bloody? This finding is usually an ominous sign; an exception is bloody stool as a result of swallowed maternal blood, which is a benign condition. A grossly bloody stool usually occurs in infants with a lesion in the ileum or the colon or with massive upper gastrointestinal tract bleeding. Necrotizing enterocolitis (NEC) is the most common cause of bloody stool in premature infants and should be strongly suspected in the differential diagnosis. B. Is the stool otherwise normal in color but with streaks of blood? This description is more characteristic of a lesion in the anal canal, such as anal fissure. Anal fissure is the most common cause of bleeding in well infants. C. Is the stool positive only for occult blood? Occult blood often signifies that the blood is from the upper gastrointestinal tract (proximal to the ligament of Treitz). Nasogastric trauma and swallowed maternal blood are common causes. Microscopic blood as an isolated finding is usually not significant. Remember that the Hematest or guaiac tests are very sensitive and can be positive with repeated rectal temperatures. D. Was the infant given vitamin K at birth? Hemorrhagic disease of the newborn may present with bloody stools, as may any coagulopathy. III. Differential diagnosis A. Occult blood only, no visible blood 1. Swallowing of maternal blood (accounts for 30% of bleeding) during delivery or breast- feeding (secondary to cracked nipples) may be the cause. Swallowed blood usually appears in the stool on the second or third day of life. 2. Nasogastric tube trauma. 3. NEC. 4. Formula intolerance. Milk protein sensitivity is secondary to cow's milk or soybean formula, and symptoms of blood in the stool usually occur in the second or third week of life. 5. Gastritis or stress ulcer (common cause and can be secondary to certain medications). Stress ulcers may occur in the stomach or the duodenum and are associated with prolonged, severe illness. Steroid therapy, especially prolonged, is associated with ulcers. Hemorrhagic gastritis can occur from tolazoline and theophylline therapy. 6. Unknown cause. B. Streaks of visible blood in the stool 1. Anal fissure. 2. Rectal trauma. This is often secondary to temperature probes. C. Grossly bloody stool 1. NEC. 2. Disseminated intravascular coagulation. There is usually bleeding from other sites. This can be secondary from an infection. 3. Hemorrhagic disease of the newborn. This entity occurs from vitamin K deficiency and can be prevented if it is administered at birth. Bloody stools typically appear on the second or third day of life. 4. Bleeding diathesis. Platelet abnormalities and clotting factor deficiencies can cause bloody stools. 5. Other surgical diseases, such as malrotation with midgut volvulus, Meckel's diverticulum, Hirschsprung's enterocolitis, intestinal duplications, incarcerated inguinal hernia, and intussusception (rare in the neonatal period). 6. Colitis. This can be secondary to a. Intestinal infections, causing colitis with bleeding such as Shigella, Salmonella, Campylobacter, Yersinia, and enteropathogenic strains of Escherichia coli. b. Dietary/formula intolerance factors, including allergy and dietary protein-induced colitis. 7. Severe liver disease. 8. Other infections, such as cytomegalovirus, toxoplasmosis, syphilis, and bacterial sepsis. IV. Data base. The age of the infant is important. If the infant is <7 days old, swallowing of maternal blood is a possible cause; in older infants, this is an unlikely cause. A. Physical examination 1. Examination of peripheral perfusion. Evaluate the infant's peripheral perfusion. An infant with NEC can be poorly perfused and may appear to be in early or impending shock. Bruising may suggest a coagulopathy. 2. Abdominal examination. Check for bowel sounds and tenderness. If the abdomen is soft and nontender and there is no erythema, a major intra-abdominal process is unlikely. If the abdomen is distended, rigid, or tender, an intra-abdominal pathologic process is likely. Abdominal distention is the most common sign of NEC. Abdominal distention may also suggest intussusception or midgut volvulus. If there are red streaks and erythema on the abdominal wall, suspect NEC with peritonitis. 3. Anal examination. If the infant's condition is stable, perform a visual examination of the anus to check for anal fissure or tear. B. Laboratory studies 1. Fecal occult blood testing (guaiac or Hemoccult test): to test for the presence of blood. 2. Hematocrit and hemoglobin: to document the amount of blood loss. If a large amount of blood is lost acutely, it takes time for this to be evident on hemoglobin or hematocrit results. 3. Apt test: to differentiate maternal from fetal blood if swallowed maternal blood is suspected. The test is performed as follows: Mix equal parts of the bloody material with water and centrifuge it. Add 1 part of 0.25 mol sodium hydroxide to 5 parts of the pink supernatant. If the fluid remains pink, the blood is fetal in origin because hemoglobin F stays pink. Hemoglobin A from maternal blood is hydrolyzed and changes color from pink to yellow-brown. However, a negative test does not rule out swallowed maternal blood. 4. Stool culture. Certain pathogens cause bloody stools, but they are rare in the neonatal nursery. 5. Coagulation studies. Coagulation studies should be performed to rule out disseminated intravascular coagulation or a bleeding disorder. The usual studies are partial thromboplastin time, prothrombin time, fibrinogen level, and platelet count. Thrombocytopenia can also be seen with cow's milk protein allergy. 6. If NEC is suspected, the following studies should be performed: a. Complete blood cell count with differential. This test is done to establish an inflammatory response and to check for thrombocytopenia and anemia. b. Serum potassium levels. Hyperkalemia secondary to hemolysis may occur. c. Serum sodium levels. Hyponatremia can be seen secondary to third spacing of fluids. d. Blood gas levels. Blood gases should be measured to rule out metabolic acidosis, which is often associated with sepsis or NEC. C. Radiologic and other studies. A plain x-ray film of the abdomen is useful if NEC or a surgical abdomen is suspected. Look for an abnormal gas pattern, a thickened bowel wall, pneumatosis intestinalis, or perforation. Pneumatosis can appear as a "soap bubble" area (see Figure 9-16, p. 118). If a suspicious area appears on the abdominal x-ray film in the right upper quadrant, it is usually not stool. With perforation, one can see the "football sign" on an anteroposterior (AP) film. This is an overall lucency of the abdomen secondary to free intraperitoneal air. Because of the abnormal interface between free air and the peritoneum, the shape resembles a football. A left lateral decubitus view of the abdomen may show free air if perforation has occurred and it cannot be seen on a routine AP film. Surgical conditions usually show signs of intestinal obstruction. [...]... 2 5-2 6 weeks 1 0-5 0 14   GA 2 3-2 4 weeks 5 0-9 0 1 2-2 1   GA >97 50  BW . 5-1 5 5-1 7 0. 5-6 BW <1000 g  7-1 9 8-2 5 4- 1 2 BW <75 0-8 00 g  3-1 9 3-3 7 4- 1 5 Severe perinatal depression 3 5-6 0 2-3 0 2-3 0 Increased Severe hypoxic-ischemic encephalopathy 6 0-7 0. impairment (%) None <1 0. 2-0 .4 1-3 0. 5-2 Prematurity a GA >30 weeks <5    GA 2 7-3 0 weeks 5-1 0    GA 2 5-2 6 weeks 1 0-5 0 14   GA 2 3-2 4 weeks 5 0-9 0 1 2-2 1   GA <23. on the infant (one preductal-right hand; one postductal-left hand or either foot). If the simultaneous difference is >1 0-1 5%, then the shunt is significant. 4. Complete blood cell count