In the name of god

1. In the name of god Case presentation Dr.Mohammad Nemati

2. Congenital Diaphragmatic Hernia • Case : A full-term male baby was born with respiratory distress and cyanosis. Physical examination showed barrel chest and scaphoid abdomen. The breath sounds were absent in the left side of the chest; the heart sounds were best heard in the right side of the chest.

3. Labored respiration, nasal flaring, and sternal retraction were found. • The baby weighed 2,800 g. • Blood pressure was 60/30 mm Hg; heart rate, 160 beats per minute; respiration, 70 breaths per minute; and temperature, 36° C (96.8° F). • ABG : pH : 7.20 PaCO2 : 55 mm Hg PaO2 : 35 mm Hg HCO3 : 19 mEq per L.

4. Medical Disease and Differential Diagnosis

5. Differential diagnoses: • Congenital cardiopulmonary anomalies should be considered whenever cyanosis and respiratory distress are present. • A scaphoid abdomen is present due to the absence of abdominal contents. • The presence of the barrel chest, bowel sounds in the chest, and the shift of heart sounds to the right definitely suggest the diagnosis of CDH.

6. To confirm the diagnosis, a CXR should be performed to demonstrate gas-filled loops of bowel and probably the spleen or liver in the chest. • The lung on the side of the hernia is compressed into the hilum, and the mediastinum is shifted to the opposite side of the chest.

8. incidence and classification of CDH: incidence : 1 in 2,500 to 3,000 births male/female ratio is 2:1 the left diaphragm is more frequently involved than the right (5:1) • practical classification : • Absent diaphragm: Very rare • Diaphragmatic hernia: Posterolateral (Bochdalek): 80% Anterior (Morgagni): 2% Paraesophageal: 15% to 20% • Eventration.: Very rare

9. The causes of hypoxemia in patients with CDH: • Atelectasisresulting from compression of the developed lung by the herniated abdominal organs • Pulmonary hypoplasia with a decrease in the number of alveoli and bronchial generations. • The hypoplastic lung will have abnormal pulmonary vasculature resulting from a disruption of normal development of the lung tissue. • PPH, causing increased right-to-left shunting through a patent foramen ovale and ductusarteriosus.

10. The degree of pulmonary hypoplasia is related to the timing of the herniation of abdominal organs into the pleural cavity. • The earlier herniation, the more severe the pulmonary hypoplasia. • Hypoplasia of the left ventricle may also occur. • The degree of pulmonary hypoplasia determines the prognosis of CDH.

11. The severity of pulmonary hypoplasia is assessed by the intrapulmonary shunt or the alveolar–arterial difference in oxygen tension (PAO2–PaO2): • (PAO2–PaO2) >500 mm Hg when breathing 100% oxygen is predictive of nonsurvival • (PAO2–PaO2) < 400 mm Hg is predictive of survival • (PAO2–PaO2) between 400 and 500 mm Hg represents a zone of uncertain prognosis.

12. The severity of pulmonary hypoplasia may also be evaluated by cardiac catheterization and pulmonary angiogram . • Patients with severe pulmonary hypoplasia typically will have a fixed right-to-left shunting at the level of the patent ductusarteriosus or patent foramen ovale caused by pulmonary hypertension.

13. Persistent pulmonary hypertension (PPH) in CDH: • several causes of PPH in these patients: • Increased pulmonary vascular resistance and pressure result from a hypoplastic lung. • The pulmonary vasculature is abnormal, with a decrease in volume and marked increase in muscular mass in the arterioles. • Right-to-left shunting of oxygen at the patent foremen ovale and the PDA. This shunting results in varying degrees of hypoxemia, hypercarbia, and acidosis causing high pulmonary vascular resistance and pressure.

14. When pulmonary artery pressures are higher than systemic pressures, right-to-left shunting occurs across the ductus, resulting in higher PaO2 in the upper extremities than in the lower extremities. • When right ventricular failure (precipitated by pulmonary hypertension, progressive hypoxemia, and acidosis or by closure of the ductus) increases right atrial pressure to a level higher than the left atrial pressure, right-to-left atrial shunting ensues, producing further hypoxemia. Left ventricular failure from hypoxemia and acidosis induces systemic hypotension, resulting in increased ductal shunting and hypoxemia. A vicious cycle is established. Unless pulmonary artery pressure is decreased, progressive hypoxia and death may ensue.

16. Other congenital anomalies in newborns with CDH : • Cardiovascular system: 13% to 23% ASD, VSD, coarctation of aorta, and TOF • CNS:28% spina bifida, hydrocephalus • Gastrointestinal system: 20% malrotationand atresia • Genitourinary system:15% hypospadias

17. Preoperative Evaluation and Preparation

18. How would you interpret this blood gases and how would you correct them? • PH : 7.20 • Pco2 : 55 mmHg • Po2 : 35 mmHg • HCO3 : 19 mEq/liter

19. The blood gases showed mixed respiratory and metabolic acidosis and severe hypoxemia. • severe hypoxemia is caused by the pulmonary pathologies and PPH. • Hypoxemia stimulates respiratory chemoreceptors and causes hyperventilation,resulting in respiratory alkalosis initially. • However if hypoxemia is not corrected, the patient will become exhausted and CO2 retention ensues. • Meanwhile, severe pulmonary hypoplasia may cause CO2 retention, too .

20. Severe hypoxemia induces anaerobic metabolism, resulting in lactic acidosis. Systemic hypotension, cause by kinking of major blood vessels, particularly those of the liver, decreases tissue perfusion, and futher contributes to lactic acidosis. • Hypoxemia and respiratory acidosis should be treated with mechanical ventilation and oxygen therapy. • metabolic acidosis should be corrected by administration of sodium bicarbonate and improvement of circulation with fluid therapy.

21. What treatment should be given to improve respiratory status preoperatively? • Immediate intervention should include decompression of the stomach with an orogastric or nasogastric tube and administration of supplemental oxygen by mask. • PPV by mask should be avoided to prevent distention of the intrathoracic stomach, which will further compress the lung and compromise respiration.

22. If cyanosis and hypoxemia persist , awake intubation should be done to facilitate mechanical ventilation . • Positive airway pressure during mechanical ventilation should not exceed 25 to 30 cm H2O to reduce the risk of tension pneumothorax. • Although pneumothorax can happen on either side, it occurs more frequently on the contralateral side of the hernia because the pressure needed to expand the hypoplastic lung is higher than that required to rupture the normal lung.

23. Should CDH repaired urgently ? • In the past, CDH was a surgical emergency, in the belief that the herniated contents caused lung collapse and respiratory failure. • It is now clear that lung compression by the herniated viscera is a minor factor in the cardiopulmonary compromise compared with the pulmonary hypertension and hypoplasia. • The consensus today is to delay surgery and concentrate on medical stabilization. The goal of preoprative therapy is to reverse the PPH that results in right to left shunting across the PFO and the PDA

24. Improvement in the infant’s status is apparent by improved oxygenation and ventilation. • doppler echocardiography may be used to confirm the decreased pulmonary vascular resistance. • The time it takes to stabilize the condition varies from 24 to 48 hours in infants with only mild pulmonary hypertension and hypoplasia up until 7 to 10 days in neonates with severe pulmonary hypertension and hypoplasia.

25. How would you treat PPH and improve oxygenation? • continue general anesthesia in the ICU , using fentanyl 3 microgram/kg/h and pancuronium 0.1 mg/kg/h to blunt the autonomically mediated cardiovascular response(pulmonary vasoconstriction) to stimulation. • minimize endotracheal suctioning to avoid even transient hypoxemia or decrease in FiO2.

26. hyperventilate the neonate with low tidal volume and high respiratory rate 60 to 120/min to PH 7.55 to 7.60. respiratory alkalosis is the most consistently effective therapeutic modality to achieve pulmonary vasodilation. • administer pharmacologic vasodilators if the above measures fail to control pulmonary hypertension. Morphine,prednisolone ,chlorpromazine , phentolamine ,acetylecholine ,bradykinin , tolazoline,prostaglandin E1 ,prostaglandin D2 and inhaled nitricoxide have been tried with some success.

27. moderately restrict fluid to 2 to 4 ml/kg/h. • ligate the PDA to prevent shunting .this is theoretically possible , but practically has been associated with sudden right ventricular failure. • support with extracorporeal membrane oxygenation(ECMO) if pharmacologic intervention fails. ECMO has been associated with a 50% to 65% survival rate.

28. The effects of NO on pulmonary and systemic circulation? • Inhaled NO is a selective pulmonary vasodilator and has no effect on systemic circulation because it is inactivated immediately on exposure to hemoglobin.some studies show improvement in oxygenation in neonates with PPH exposed to 20 to 80 ppm NO. • NO has been reported to be ineffective before ECMO therapy in those CDH patients with pulmonary hypoplasia.after ECMO followed by surgery, NO was effective in improving oxygenation.

29. How is ECMO established? • Venovenous or venoarterial bypass is used. • Venovenousbypass is established with a single cannula through the internal jugular vein, with blood removed from and infused into the right atrium via separate ports. • Venoartrial bypass is used preferentially by some center because it provides the cardiac support that is often needed. The right atrium is cannulated via the internal jugular vein and the aortic arch through the right common carotid artery.

30. What are the advantages of ECMO ? • Diversion of as much as 80% of cardiac output from the right atrium into the extracorporeal circuit immediately reduces or eliminates right to left shunting through the foramen ovale or ductus arteriosus. • Right ventricular work is decreased because of reduced pulmonary blood flow and pressure.

31. Pulmonary vasoconstriction is reduced because hypoxemia and acidosis are corrected by ECMO. improved systemic oxygenation and reduced ductal blood flow may lead to spontaneous closure of the ductusarteriosus. • The hypoplastic lung is allowed to grow rapidly and alveolar size is increased. • The incidence of bronchopulmonary dysplasia is reduced since FiO2 and airway pressure are lowerd by ECMO.

32. The indications of ECMO : Patients with severe hypoxemia and pulmonary hypertension who do not responsd to maximal conventional respiratory and pharmacologic intervention . • However, ECMO is associated with serious complications of intracranial and pulmonary hemorrahage.

33. The contraindications of ECMO : • Gestational age < 35 weeks • Weight < 2000 gr • Preexisting intracranial hemorrhage • Congenital or neurologic abnormalities incompatible with good outcome • > 1 week of aggressive respiratory therapy • Congenital heart disease

34. The optimal time to repair CDH : • The baby is maintained on ECMO until the pulmonary hypertension is reversed and improvement in lung function is evident. • Doppler echocardiography may be used to confirm the reverse of PPH. This is usually seen within 7 to 10 days, but in some infants is not apparent for up 3 weeks. • Newborns who do not demonstrate significant improvement over this time have pulmonary hypoplasia that will not benefit from further extracorporeal life support.

35. Timing of repair of the CDH on ECMO is contraversial. • Some centers prefer early repair to allow a greater duration of postrepair ECMO, whereas many centers defer repair until the infants has demonstrate the ability to tolerate weaning from ECMO support.

36. What other measures should you take to prepare the patient for surgery? • The patients should be examined carefully for the presence and severity of associated congenital anomalies. Those patients with congenital heart disease have significantly increased mortality. • Hypothermia should be prevented and corrected, since hypothermia can increase oxygen consumption and result in further hypoxemia and acidosis. The neonate should be maintained in a neutral thermal enviroment of 30 to 40 ° C .

37. Laboratory studies should include ABG ,CBC, electrolytes, blood sugar, blood type,and crossmatch for blood products. • Venous access should be ready prior to surgery. Peripheral veins in the upper extremities are preferred because reduction of the hernia often increases abdominal pressure and partially obstructs the inferior vena cava, making lower extremity veins less reliable. Neck vein are avoided in case ECMO is required.

38. How would you premedicate this patient? • No premedication should be given to the neonate with CDH. • The newborn dose not have any anxiety ,and sedatives may just further depress the already compromised cardiopulmonary function.

39. Intraoperative Management

40. What monitors would you use for this neonate during surgery? Respiratory: • Precordial and esophageal stethoscope • Pulse oximeter, both above and below nipple for preductal and postductal oxygen saturation. • Capnometer • Inspiratory pressure gauge • Inspiratory oxygen concentration • ABG

41. Cardiovascular: • ECG • Doppler blood pressure device • Precordial stethoscope • Arterial line- right radial artery for preductal PaO2 • Central venous pressure line for evaluating volume status and right ventricular performance Thermoregulatory • Esoghageal or rectal temperature probe

42. How would you induce and maintain anesthesia? • If the neonate has not been intubated, awake intubation should be done after preoxygenation. • However, if the neonate is too vigorous for awake intubation, he can be intubated without a muscle relaxant after breathing halothane and oxygen spontaneosly. • Positive pressure ventilation should be avoided before intubation to prevent gastric distention and further compromise of respiration.

43. The choice of anesthetics depends on the severity of cardiovascular dysfunction. • Patients in shock and severe hypoxemia may tolerate only oxygen and a nondepolarizing relaxant such as pancuronium or vecuronium. • if blood pressure is adequate and stable, halothane or fentanyl in addition to a muscle relaxant, often pancuronium, may be titrated to maintain anesthesia. • fentanyl and pancuronium may be continued postoperatively to control ventilation and minimize hormonal response to stress, which may increase pulmonary hypertension.

44. NO should not be used in patient with CDH before hernia reduction and abdominal closure. • Because NO has higher diffusion capacity than nitrogen(35:1), the amount of NO diffused from blood to the gut is much more than the amount of NO diffused frome the gut to the blood. • Therefore, NO may distend the intrathoracic gut and compress the functioning lung tissue, further compromising pulmonary function.moreover, a distended gut may cause difficulty in abdominal closure and may increase abdominal pressure, compressing the inferior vena cava and resulting in hypotension.

45. Would you use 100% oxygen during anesthesia? • Selection of the appropriate inspired concentration of oxygen depends on the severity of pulmonary dysfunction. • Retrolental fibroplasis is a potential danger during neonatal anesthesia. • Current guideline suggest that infants are at risk for retrolental fibroplasia until 44 to 50 weeks of gestational age.

46. However, hypoxia cause pulmonary vasoconstriction and pulmonary hypertension wich may increase right-to-left shunting of desaturated blood at preductal or ductal level. • therefore, air or nitrogen is added to oxygen if the PaO2 on 100% oxygen is> 90 to 100 mm Hg. • PaO2 should be optimally kept at 80 to 100 mm Hg or the arterial oxygen saturation between 95% to 98%.

47. How would you ventilate the patient? • Ventilation is controlled either manually or by a respirator. Small tidal volumes should be used to keep the airway pressure below 20 to 30 cm H2O in order to prevent contralateral pneumothorax . • High respiratory rates (60 to 120 breaths/min) should be adjusted to achieve hyperventilation to PaCO2 between 25 to 30 mm Hg in order to lower pulmonary vascular resistance and minimize right-to-left shunting through the ductus arteriosus.

48. The following steps are used to maintain body temperature: • warm the operating room to 80° F( 27° C). • use radiant warming lamps and a heating blanket. • warm and humidify inspired gases. • warm transfused blood and intravenous fluid to 37 ° C.

49. The surgeon returned the intrathoracic stomach and intestine to the peritoneal cavity and the ipsilateral lung was found to be hypoplastic and collapsed. The resident anesthesiologist tried to expand the collapsed lung manually with positive airway pressure. Five minutes after the abdomen was closed, the blood pressure suddenly dropped from 70/40 to 30/20 mm Hg, the heart rate from 150 to 80/min And the pulse oximeter from 95% down to 60% saturation. What would you do immediately?

50. Any sudden deterioration in blood pressure, heart rate, oxygen saturation, or pulmonary compliance is suggestive of tension pneumothorax. • Auscultation of the chest, especially the contralateral side, should be done immediately. If absent or diminished breath sounds confirm the diagnosis, a chest tube should be inserted right away. • A large-bore intravenous catheter with needle may be inserted to release the tension pneumothorax if a chest tube is not immediately available.