Hyperventilation and Hypocarbia

Baby Suffers Periventricular Leukomalacia (PVL) and Brain Injury Due to Hyperventilation and Resulting Hypocarbia.

Babies born prematurely at less than 34 weeks gestation frequently require a breathing machine to assist with respirations. The more premature the baby, the more likely the need for mechanical ventilation. However, with intubation and mechanical ventilation come risks to the baby if the ventilator settings are not properly managed by physicians and respiratory therapists responsible for monitoring the effects of the ventilation on the baby's blood gases. If the respirator is set at too high a rate, it can blow off too much carbon dioxide from the baby's lungs resulting in low carbon dioxide (CO2) levels in the baby's blood. If the CO2 level gets too low, it can cause constriction of the blood vessels in the baby's brain and resulting white matter damage. This damage may be described by the physicians as Periventricular Leukomalacia or PVL. If severe, such an injury could lead to a diagnosis of Cerebral Palsy, which may have devastating consequences for the baby and the baby's family.

If your baby has been diagnosed with Cerebral Palsy as a result of Periventricular Leukomalacia and if your baby was premature and required mechanical ventilation or resuscitation to help them breath, you should contact a medical malpractice attorney with expertise in handling these types of cases. It constitutes medical malpractice or medical negligence for a doctor, nurse of respiratory therapist to not adequately monitor a baby who is on a ventilator and to fail to correct abnormal carbon dioxide levels (hypocarbia or hypocapnia) when they occur.

Case Report of Baby Suffering Periventricular Leukomalacia and Cerebral Palsy:

(The following is an example of an actual case handled by the medical malpractice attorneys at Hixson & Brown).

The medical malpractice lawyers at Hixson & Brown represented a Baby born at a Level II Hospital in Iowa. The Baby was one of two twins who were born prematurely at 31 completed weeks of gestation. The Baby was initially healthy with Apgar scores of 7 and 9 at 1 and 5 minutes, respectively. Within approximately 10 minutes of life the Baby developed respiratory distress syndrome and was intubated and placed on a respirator to assist with breathing. There were no signs that Baby was suffering from any kind of infectious process, and a blood culture drawn on the first day of life grew no bacteria. Baby's first day of life was without complications and a review of the records did not reveal any evidence of prior brain injury or any other neurological injury or compromise.

As will be discussed in more detail below the Baby's clinical condition worsened significantly on day of life #2 and ultimately he was transferred to a tertiary care center (Level III Hospital) for specialty care and treatment. While at the Level III Hospital, an ultrasound of Baby's head showed multiple periventricular cysts. A follow up brain CT revealed extensive Periventricular Leukomalacia. Periventricular Leukomalacia is a known sequelae of hypoxia (lack of oxygen) and ischemia to the premature brain. Thus, the medical malpractice attorney's at Hixson & Brown knew that the analysis of the medical records needed to focus on whether there was evidence of post-natal hypoxic/ischemic events documented in the medical records to identify a cause for Baby's PVL and resulting Cerebral Palsy.

Applicable Medical Literature Surrounding Hypocarbia and Relation to Periventricular Leukomalacia

When the medical malpractice lawyers reviewed the medical record it clearly showed that the Baby had profound hypocarbia that went undetected and untreated in the early morning hours of the 2 nd day of life. The medical literature supported a link between hypocarbia (hypocapnia) and Periventricular Leukomalacia.

In particular, Shankaran, et al., in a prospective study, evaluated the roles of cumulative exposure to hypocarbia or hyperoxia to PVL - " Cumulative Index of Exposure to Hypocarbia and Hyperoxia as Risk Factors for Periventricular Leukomalacia in Low Birth Weight Infants, Pediatrics (2006); Vol. 118, No. 4, pp. 1654-1659. In this article, hypocarbia was defined as a PaCO2 < 35 mmHg and the cumulative index of exposure was calculated as (35 minus PaCO2) multiplied by time interval in hours. The purpose was to identify the length of time that an infant was subjected to hypocarbia as well as the severity of the hypocarbia. The association between the cumulative exposure to hypocarbia and PVL was then analyzed. "Among infants with no hypocarbia (n = 289), the rate of PVL was 1.4%. Id. at 1656. However, when the cumulative index of exposure surpassed 96 mmHg hours, the incidence of PVL rose to 7.4%. Other medical literature supported the fact that even one arterial CO2 reading below 20 mmHg was significantly associated with the development of Periventricular Leukomalacia and Cerebral Palsy.

Standard of Care in 2003 re: Hypocarbia.

The medical malpractice attorneys at Hixson & Brown retained numerous experts to assist them in preparation for presenting this case to a jury at trial. Based on the deposition testimony of these experts and on well established medical literature at the time as well as the known association between hypocarbia and PVL in premature infants, the medical malpractice lawyers were able to show that the standard of care in 2003 required medical care providers to take precautions to prevent and/or immediately treat hypocarbia (hypocapnia) in preterm infants on mechanical ventilation. The attorneys argued that a failure to do so was a beach in the standard of care or negligence.

Facts Applicable to Whether or not a Breach in the Standard of Care Occurred

Based on the facts of the case the medical malpractice lawyers at Hixson & Brown were able to show that the Baby suffered a prolonged period of hypocarbia or hyperventilation. Blood gases were performed on Baby at 12:40 AM and revealed a PCO2 of 19 mm Hg (normal is >35 mmHg). At the time of this blood gas result the Baby was being treated with mechanical ventilation with a rate of 45 BPM and a Peak Pressure/PEEP setting of 28/4. At this time medical care providers should have been aware that the Baby was Hypercarbia and at increased risk for PVL due to vasoconstriction and decreased cerebral blood flow.

However, there was no documentation in the medical record revealing that the physician, nurse or respiratory therapist understood the significance of the hypocarbia being caused by the over ventilation of the Baby. Repeat blood gases in the early morning hours of the 2 nd day of life revealed the following low CO2 values:

1:20 AM: PCO2: 21 mmHg

2:27 AM: PCO2: 28 mmHg

6:50 AM: PCO2: 21 mmHg

Although the Baby remained Hypercarbia due to hyperventilation throughout the night, there was no mention of it by the physician, the nurse or the respiratory therapist. During this entire time, the Baby's ventilator rate remained at 45 BPM with a Peak Pressure/PEEP maintained at 28/4. There was no attempt to treat the Baby's hypocarbia and it appears that it went unnoticed. The medical experts hired by the medical malpractice attorneys at Hixson & Brown testified that this was a breach in the standard of care and medical malpractice.

It was important to note in the case the medical record revealed on day of life #1 that one of the Baby's physicians had previously ordered that the Baby's CO2 level was to be maintained between 50-60 mmHg. This aim of permissive hypercarbia was reasonable given Baby's prematurity and clinical picture. However, once Baby's carbon dioxide level (CO2) dropped to 19 mmHg at 12:40 AM on the 2 nd day of life, the standard of care required the nursing staff and/or the respiratory therapist caring for the Baby to specifically report the hypocarbia to the physician and to document the report. The failure to do so was negligence or medical malpractice. Additionally, if the hypocarbia was reported to the physician or if he was otherwise aware of it during the early morning hours of the 2 nd day of life, the standard of care required him to order a reduction in the ventilator rate and or a reduction in the Peak Pressure in an attempt to correct the low CO2 level. The doctors failure to do so was a breach in the standard of care and was medical malpractice.

Later in the morning on 2 nd day of life, a different physician came on duty. At 7:30 AM the nurse notes that the blood gases of 6:50 AM (PCO2 of 21 mmHg) was reported to this physician. Subsequently, at 7:50 AM (20 minutes later), the Baby's vent rate was reduced from 45 BPM to 35 BPM and his Peak Pressure/Peep from 28/4 to 22/4. This immediate reaction to the hypocarbia by this physician was appropriate and met the standard of care. Unfortunately, by that time the Baby had suffered from hypocarbia for more than 7 hours before the physician recognized the problem and acted to correct it. Subsequent reductions in the Baby's ventilator settings continued until 2:15 PM on the 2 nd day of life when Baby's PCO2 was 39 mmHg and, by definition, no longer Hypercarbia.

Although it was never quite clear what the nurses or the doctor specifically knew in the early morning hours of the 2 nd day of life, what is clear is that the Baby was Hypercarbia and at increased risk for PVL. The medical experts hired by the medical malpractice lawyer at Hixson & Brown testified that this was a breach in the standard of care and medical malpractice.

Hypocarbia as a Cause For Baby's Periventricular Leukomalacia and Cerebral Palsy

Based on the medical literature, Baby's risk of Periventricular Leukomalacia as a result of the hyperventilation and low carbon dioxide level could be calculated. The medical experts hired by the medical malpractice attorney's testified that the cumulative exposure to hypocarbia (hypocapnia) was an independent risk factor for PVL. In applying the methodology set out by Shankaran, et al., the cumulative index of exposure to hypocarbia for the Baby was calculated as follows:

Time Interval PCO2 Level CIE Calculation Cumulative CIE Calculation

0040 – 0120 hrs

(.667 hr)

19 mmHg(35-19) x .667 = 10.6710.67 mm Hg ∙ h

0120 – 0227 hrs

(1.117 hrs)

21 mmHg(35-21) x 1.117 = 15.6426.31 mm Hg ∙ h

0227 – 0650

(4.333 hrs)

28 mmHg(35-28) x 4.333 = 30.3356.64 mm Hg ∙ h

0650 – 0815

(1.417 hrs)

21 mmHg(35- 21) x 1.417 = 19.8476.48 mm Hg ∙ h

0815 – 0930

(1.25 hrs)

20 mmHg(35- 20) x 1.25 = 18.7595.23 mm Hg ∙ h

0930 – 1045

(1.25 hrs)

24 mmHg(35- 24) x 1.25 = 13.75108.98 mm Hg ∙ h

1045 – 1230

(1.75 hrs)

28 mmHg(35- 28) x 1.75 = 12.25121.23 mm Hg ∙ h

1230 – 1415

(1.75 hrs)

32 mmHg(35- 32) x 1.75 = 5.25126.48 mm Hg ∙ h

As pointed out by Shankaran, et al., a Cumulative Index of Exposure (CIE) in the highest quartile and exceeding 96 mmHg caused the incidence of PVL to rise from 1.4% in infants with no hypocarbia, to 7.4% in infants with a CIE greater than 96 mmHg. The Baby's CIE to hypocarbia of 126.48 mmHg showed an independent risk factor for PVL and, that more likely than not, the medical malpractice of hyperventilating the Baby and causing hypocarbia played a primary causative role in the development of PVL and resulting Cerebral Palsy. The medical experts hired by the medical malpractice lawyers at Hixson & Brown testified that if the medical care providers had appropriately and timely recognized and treated the Baby's hypocarbia, the Baby would not have developed severe cystic periventricular leukomalacia and within a reasonable degree of medical certainty would not have suffered the profound brain injury and Cerebral Palsy that the Baby would suffer from for an entire lifetime.

If you have a premature baby who suffers from Cerebral Palsy or Periventricular Leukomalacia (PVL), you should obtain a copy of the medical record to see if there was a significant period of hypocarbia during mechanical ventilation. You should also contact a lawyer or attorney who has expertise handling these types of medical malpractice cases.