Recently we set up new ventilator guidelines based on the recommendations of the hospitals we send our kids to (see this post). One of the recommendations was not to over oxygenate neonates. That not only can too much oxygen cause morbidity in neonates, it can cause long term complications in term infants too.
The old wisdom we had to change was that any neonate who had a heart rate of less than 100 should receive positive pressure breaths with 100% FiO2 in order to stimulate breathing.
Why was it believed that 100% oxygen was needed? Well, allow me to walk you through the anatomy of an infant's circulation before and after birth:
1. Before birth, all oxygen to the baby comes from the placenta via the umbilical vein, and most oxygenated blood takes the path of least resistance across the ductus arteriosis. Resistance is high in the lungs due to constricted arterioles and fluid filled alveoli.
2. After birth there are several major changes that take place
- The cord is clamped, which causes constricting of cord vessels
- The baby's systemic blood pressure increases immediately
- The baby is forced to take a breath to get oxygen
- In a matter of seconds after oxygen enters the lungs the pulmonary vessels relax
- and the Ductus Arteriosis constricts
- This makes the lungs the route of least resistance for blood from the right side of the heart
- thus causing oxygenated blood to be sent to the system
- Fluid in lungs is absorbed by the body and gradually replaced by oxygen
Back in the 1970s there was a lot of litigation where the parents of children who either died or had complications due to anoxic brain injuries that occurred at birth, and that is why the Neonatal Resuscitation Program (NRP) was started. This was an opportunity for experts at larger institutions to share their wisdom with all hospital workers throughout the U.S.
The #1 sign of low oxygen to the tissues in newborn infants is a drop in heart rate. Thus, a heart rate of less than 100 is the first sign that action needs to be taken -- per the NRP guidelines. Most of these children respond well to positive pressure breaths. Some, however, continue to need additional support, such as intubation, epinephrine, glucose or fluid depending on the determined cause.
However, based on the fact that oxygen in the lungs results in a relaxation of the pulmonary vasculature, it was believed, inaccurately it now turns out, that 100% oxygen would help trigger that first breath. However, recent studies show us the following:
1. A growing # of literature show you don't need 100% oxygen when ventilating neonates
2. New studies show that high levels of oxygen, even in otherwise healthy term babies, can be detrimental to the health and long term health of newborns
3. Several studies have linked 100% oxygen even for as little as one minute to:
- Cellular death
- Delayed development of oxygen sensing tissue
- Oxygen radical disease of neonate
- Retnopathy of Prematurity
- Chronic lung disease
5.. Benefits of lowering oxygen sats (SpO2):
- Increased neurological function
- Decreased retnopathy of prematurity
- Decreased chronic lung disease
- Increased weight gain
- Decreased infection
- Decreased ventilator days
- Decreased oxygen days
- Decreased length of stay
7. These studies have scientists now thinking it is not oxygen that stimulates that first breath, but heat, positive pressure breaths, and stimulation by either suctioning, rubbing the baby with a warm blanket, tapping the soles of the feet, etc.
8. Some institutions are currently doing studies using 21% FiO2 during positive pressure breaths . I believe the Spectrum Health in Grand Rapids is currently undergoing one such study.
9. Some studies are being done to determine if there are ways to keep the SpO2 of a newborn baby at less than 60% to allow for the best growing environment for premature organs. These organs are not meant to be exposed to an over oxygenated environment, and should not be exposed to too much oxygen.
10. For term babies, the reason you don't want to over oxygenate is because new studies show that too much oxygen can cause an increase of free radicals which may not cause immediate problems, but may increase the risk of various cancers.
11. It may take up to 10 minutes for a newborn baby's sat to get up to 90%. In the first few minutes an SpO2 of 70-80% is normal and acceptable. Therefore it's not a good idea to shock a baby with 100% FiO2.
12. According to Roy Ramirez, "Oxygen Management of the Very Low Birth Weight Infant" (RT Magazine, Roy Ramirez, February, 2010), "Gladstone et al showed a correlation between oxygen use and an increase in protein-bound carbonyl in lung fluid, which is a marker for oxidative injury.
13. Likewise, According to Ramirez, "Munkeby et al demonstrated that oxygen at high concentrations, even for short periods of time, can produce a significant increase in inflammatory markers.
14. Also Accoridng to Ramirez, "Some infants could be predisposed to chronic lung disease as demonstrated in a study by Tsao et al, which showed a direct correlation in placenta growth factor (P1GF) levels in cord blood at birth and risk for pramature infants to develop chronic lung disease, also known as bronchopulmonary dysplasia).
15. Ramirez also notes an infant in utero lives in an SpO2 environment of about 60%, and this can drop to 30% during labor. So it is acceptable to allow the SpO2 to slowly increase to the recommended level (see below) over a 10 minute period. This is one of the main reasons why shocking the baby with 100% FiO2 can be detrimental to the infant, and can actually have the opposite effect as desired.
Based on studies, the following are now the new recommendations:
1. Many institutions, including the Neonatal Resuscitation Program, now recommend you no longer ventilate at 100% oxygen. While it used to be believed that every baby who needs positive pressure ventilation should get 100% FiO2, this is no longer deemed acceptable due to recent study results.
2. A new recommendation is that oxygen should be considered a drug, and each patient should get a different dose based on need.
3. The new recommended starting FiO2 is 40%, which is to be adjusted to maintain target sats (see below)
4. Since it is no longer believed oxygen stimulates that first breath, and considering the dangers of oxygen, some hospitals have gone to 21% FiO2 already. I imagine this will be the recommended FiO2 for the NRP program of the future.
5. It is essential that you pay attention so sats (see below) Do not leave any baby at 100%.
6. The only exception is for PPHN (Persistent Pulmonary Hypertention of the newborn). If you suspect PPHN, make sure you give 100% FiO2 or at least try to keep sats 95-99%.
7. With a baby less than 30 weeks the SpO2 should be kept at less than 90%. The concern is early eye development. Plus scientists are not sure if its organs should be rapidly exposed to too much oxygen, when in utero they were developing in an environment where the SpO2 was less than 60%.
8. It is okay to use room air. If you only have room air, use room air. This is acceptable per the Neonatal Resuscitation Program.
9. It is recommended that all OB departments have an oxygen blender.
10. It is recommended that all tails be taken off Ambu-bags so that 100% is never given just in case you have to use them (Ideally, however, you should use a T-piece resuscitator like a Neo-puff which has a blender built in).
11. If you see low sats try to fix the problem before reaching for oxygen. Don't treat the number or the symptom. Treat the patient.
12. If baby spontaneously breathing and continues to be labored, consider CPAP even if you don't have a doctor's order. According to Neonatal Resuscitation Program, CPAP is considered good practice. You may use Neo-puff to administer CPAP by holding the mask over the neonates mouth and nose.
According to Spectum Health in Grand Rapids, the following are the new target SpO2s you should reach for:
- Less than 30 weeks gestation: SpO2 of 85%
- 30-34 weeks gestation: SpO2 of 88%
- 35-39 weeks gestation: SpO2 of 91%
- 40 weeks gestation or greater: SpO2 of 94%
- Achieve sat gradually
- Decrease FiO2 as sats rise greater than 95%
- If heart rate not rising, check for correct ventilation
- Do not chase saturations, as fluctuations in sats are normal (better to bounce low than high)
- In other words: don't stare at the sat monitor