HFOV Case Study 3.6kg MAS Instructor Copy Color key: Black Patient case Blue RN/RCP collaboration Red MD consult Green - Critical Thinking Inquiry Green italics CT answers ABG: ph/pco2/po2/base A 35 year-old primigravida, whose pregnancy had been thus far uncomplicated, was admitted to the hospital for induction of labor at 41 weeks gestation. An ultrasonographic scan suggested the presence of oligohydramnios, and induction of labor with oxytocin was successful. Electronic fetal heart rate monitoring disclosed both late and variable decelerations. Artificial rupture of the membranes produced thick, meconium-stained amniotic fluid. An amnioinfusion was done to help relieve the fetal heart decelerations, but there was little progress and a primary cesarean section was performed. A 3.6 kg male infant was delivered. The baby was very floppy at birth and was covered by yellow-green meconium. No respiratory effort was noted. The heart rate was 70 beats/min, the baby s color was very dusky, and he had poor peripheral perfusion. The infant was intubated and suctioned with the retrieval of a significant amount of particulate meconium. Positive pressure ventilation was given. HR 130 FIO2.6 O2 Sat: 92% Umbilical ABG: 7.03/77/14 CXR: Dense, fluffy infiltrates 1 of 6
CT: CXR indicative of? Meconium Aspiration Pneumonitis RN/RCP: Asses pt, breath sounds, patent and secure airway, vital signs MD: Order for mechanical ventilation CMV: TCPL: Rate 60 IT.5 PIP 28 PEEP 6 FIO2 1.0 ABG: 7.29/55/48 CT: What is the next step? There are a couple of things to consider...surfactant and/or HFOV (Meconium contains numerous noxious chemical constituents, particularly bile salts, which have been shown to inactivate surfactant. Small clinical trials have shown a favorable benefit to both administration of surfactant and lung lavage with surfactant, but this is not yet an approved indication). HFOV might be an option at this time, although great care is necessary to avoid gas trapping and hyperinflation. MD: Decides to increase rate, increase PIP and Peep, and increase IT. TCPL: Rate 70 IT.6 PIP 30 PEEP 6 FIO2 1.0 Note the graphic monitoring: 2 of 6
CT: What abnormality is present on this waveform? Gas trapping Shortly thereafter, the patient had an acute deterioration. Another CXR was obtained. CT: Interpret this CXR Large tension Pneumothorax on right. Shift of heart and mediastinum to left MD: At bedside placing a chest tube RN/RCP: RN starting dopamine to support blood pressure. RCP assessing oxygenation status via pulse oximeter. ABG: 7.10/65/34 CT: What is the next step? Start thinking pulmonary hypertension. Perform dual site pulse oximetry. (pre and post ductal). If there is a R to L shunt through the ductus arteriosus, there will usually be a greater than 10-15% difference in SpO2 (O2 SAT) readings. Pre ductal O2 SAT: 91% Post ductal O2 SAT: 74% CT: So, what does this indicate? PPHN RN: fluid bolus is given for a mean arterial blood pressure of 39. Dopamine is increased and dobutamine is added. MD: Cardiologist is now at bedside performing an echocardiogram. Results of ECHO: PDA, and PFO, with subsequent R to L shunting. Inhaled Nitric Oxide (ino) was started at 20 ppm. There was no change in the patient s condition. Pre ductal O2 SAT: 89% Post ductal O2 SAT: 72% BP: 60/40, mean 48 Repeat CXR: no pneumothorax. Diminished lung volumes noted. 3 of 6
CT: What would you do next? Switch to HFOV. CT: What would be the appropriate settings to start with and why? MAP equal to CMV, (because of the presence of air trapping in this case, too aggressive use of MAP can further aggravate it and can result in PIE or pnemothoraces), amp to provide adequate chest wiggle (clavicle to umbilicus), Hz for patient s weight (8-10), and FIO2 1.0. CT: What are the potential complications of HFOV with this patient? Air trapping/hyperinflation/air leak/hemodynamic compromise MD: Agrees with your recommendation and asks you to place on HFOV. CT: What do you need to do before switching to HFOV? Vital sign assessment, heightened awareness of safety and stable airway, positioning and immobility, firm mattress, suction HFOV: MAP: 20 AMP: 40 Hz: 10 FIO2: 1.0 (actual read out.96 ino) CT: Now what? Assess patient and vital signs. O2 SAT should be increasing. Chest wiggle should be adequate. Blood pressure monitoring. It has been 8 minutes since the initiation of HFOV and O2 SAT is 84%. Blood pressure is adequate. What should you be thinking about? The O2 SAT is not adequate, meaning that the lung is not recruited, begin to increase MAP. Increase MAP until you see a rise in CVP or signs of decreased systemic blood flow. Look at chest wiggle, monitor tcco2 and Bp. O2 SAT: 88% tcco2: 60 Bp: 60/42 What is the next step and why? Wait one hour before obtaining CXR and ABG. Time is needed for O2 and CO2 equilibration due to the small tidal volumes and fast rates compared to CMV. ABG: 7.32/58/99 CXR: Expanded to 8 ribs, ETT at T2, no recurrence of pneumothorax CT: Response to the above information? Oxygenation is adequate at this time along with lung volume. However, PCO2 is still too high. Think about assessing chest wiggle, is it adequate? RN/RCP: Both of you are at the beside and determine that chest wiggle is indeed, from clavicles to umbilicus, maybe even slightly beyond the umbilicus. CT: Need for reassessment of CO2 removal. Because patient is 3.6 kg, we can afford to decrease the Hz to try and decrease CO2. Remembering that lowering the Hz, will also increase ventilation. Watch for hyperinflation. HFOV: MAP: 20 AMP: 40 Hz: 8 FIO2: 1.0 (actual read out.96 ino) CT: The next step? Again, wait one hour before getting the next ABG Within this next hour, you come to the bedside because the high pressure alarm is sounding and the MAP is not holding. You note that the dump valve is open to ambient air with each breath and the oscillator is stopped. 4 of 6
References RN/RCP: Note that the flexible circuit has quite a bit of water sloshing in it. You quickly drain the water back to the water trap. CT: What do you do now? Pressurize the circuit and the piston will start automatically if the problem has been solved. Piston starts and MAP is maintained. ABG: 7.37/50/103 CT: At this time, what should you be thinking and why? That the infant has responded to the above settings. Keep a close eye with assessments, watch chest tube. And think about weaning the FIO2. FIO2 should be weaned very slowly due to the PPHN factor. Start weaning by 2% increments and after each 5% change, obtain an ABG. Wean FIO2 before weaning MAP (unless grossly hyperinflated) Over the next 3 days, the patient has been able to be weaned successfully. CT: Discuss the course of weaning HFOV settings. First wean the FIO2 until you are at 40-50%, then begin to wean the MAP by 1-2cm at a time, until you reach about 10-15cm. Obtain CXRs to monitor lung volume. Wean the AMP in increments of 2-5cm at a time, until you reach 25-30cm. Don t need to adjust the Hz in the course of weaning. The patient continued to wean steadily. The ino was also weaned successfully. The baby was transitioned back to conventional ventilation. The right chest tube was subsequently removed. This case represents a common problem still seen in most tertiary neonatal intensive care units. Meconium aspiration syndrome is a condition associated with both prolonged pregnancy and fetal distress. It may result in meconium staining (meconium on the baby but not in the airway), meconium aspiration (meconium found in the airways), or meconium aspiration syndrome (meconium in the airway, respiratory distress, and a compatible chest radiograph). The latter condition may be complicated by the development of chemical or bacterial pneumonia, or, as in this case, PPHN, a severe and life-threatening condition, in which pulmonary vascular resistance fails to fall, resulting in right-to-left shunting through the PDA and PFO and severe ventilation/perfusion mismatch, resulting in profound hypoxemia. 1. Kattwinkel J (ed.). Neonatal Resuscitation, 5th edition. Elk Grove Village, IL. American Academy of Pediatrics-American Heart Association, 2006. 2. Wiswell TE. Meconium aspiration syndrome. In Donn SM and Sinha SK (eds.). Manual of Neonatal Respiratory Care, 2nd edition. Philadelphia, Mosby Elsevier, 2006, pp. 325-330. 3. Moses D, Holm B, Spitale P, et al. Inhibition of pulmonary surfactant function by meconium. Am J Obstet Gynecol 1991; 164:477-481. 4. Andersson S, Kheiter A, Merritt TA. Oxidative inactivation of surfactants. Lung 1999; 177:179-189. 5. Lotze A, Mitchell BR, Bulas DI, et al. Multicenter study of surfactant (beractant) use in the treatment of term infants with severe respiratory failure. Survanta in Term Infants Study Group. J Pediatr 1998; 132:40-47. 5 of 6
6. Wiswell TE, Knight GR, Finer NN, et al. A multicenter, randomized, controlled trial comparing Surfaxin (Lucinactant) lavage with standard care for treatment of meconium aspiration syndrome. Pediatrics 2002; 109:1081-1087. 7. Donn SM. Pressure control ventilation. In Donn SM and Sinha SK (eds.). Manual of Neonatal Respiratory Care, 2nd edition. Philadelphia, Mosby Elsevier, 2006, pp. 210-211. 8. Donn SM, Bandy KP. Volume-controlled ventilation. In In Donn SM and Sinha SK (eds.). Manual of Neonatal Respiratory Care, 2nd edition. Philadelphia, Mosby Elsevier, 2006, pp. 206-209. 9. Nelson M, Becker MA, Donn SM. Basic neonatal respiratory disorders. In Donn SM (ed.). Neonatal and Pediatric Pulmonary Graphics. Principles and Clinical Applications. Armonk, NY, Futura Publishing Co., 1998, pp. 253-277. 10. Schumacher RE, Donn SM. Persistent pulmonary hypertension of the newborn. In In Donn SM and Sinha SK (eds.): Manual of Neonatal Respiratory Care, 2nd edition. Philadelphia, Mosby Elsevier, 2006, pp. 331-336. 11. Philip AGS. Neonatology, A Practical Guide, 2nd edition. Flushing, NY, Medical Examination Publishing Co., 1980, pp. 127-130. 22. 12. Guthrie SO, Walsh WF, Auten K, Clark RH. Initial dosing of inhaled nitric oxide in infants with hypoxic respiratory failure. J Perinatol 2004; 24:290-294. 13. Donn SM. Neonatal shock and hypotension. Arch Perinatal Med 2005; 11:16-18. 14. Kinsella JP, Abman SH. Clinical approach to the use of high frequency oscillatory ventilation in neonatal respiratory failure. J Perinatol 1996; 16:S52-55. 15. Donn SM, Gates MR. Transport of ventilated babies. In In Donn SM and Sinha SK (eds.). Manual of Neonatal Respiratory Care, 2nd edition. Philadelphia, Mosby Elsevier, 2006, pp. 487-496. These case studies are for reference only. Each patient is unique and may require different care. 6 of 6