Noninvasive Ventilation in Cystic Fibrosis: Clinical Indications and Outcomes in a Large UK Adult Cystic Fibrosis Center

BACKGROUND

Noninvasive ventilation (NIV) is routinely used to treat patients with cystic fibrosis and respiratory failure. However, evidence on its use is limited, with no data on its role in disease progression and outcomes. The aim of this study was to assess the indications of NIV use and to describe the outcomes associated with NIV in adults with cystic fibrosis in a large adult tertiary center.

METHODS

A retrospective analysis of data captured prospectively on the unit electronic patient records was performed. All patients with cystic fibrosis who received NIV over a 10-y period were included in the study. A priori, 2 groups were identified based on length of follow-up, with 2 subgroups identified based on duration of NIV treatment.

RESULTS

NIV was initiated on 64 occasions. The duration of follow-up was categorized as > 6 months or < 6 months in 31 (48.4%) and 33 (51.6%) occasions, respectively. The most common indications for starting NIV were chronic (48.5%) and acute (32.8%) hypercapnic respiratory failure. Among those with a follow-up > 6 months, subjects who stopped using NIV early showed a steady median (interquartile range) decline in FEV₁ (pre-NIV: -0.04 [-0.35 to 0.03] L/y vs post-NIV: -0.07 [-0.35 to 0.01] L/y, P = .51), while among those who continued using it had an improvement in the rate of decline (pre-NIV: -0.25 [-0.52 to -0.02] L/y vs post-NIV: -0.07 [-0.13 to 0.16] L/y, P = .006). No differences in intravenous antibiotic requirement or pulmonary exacerbations were noted with the use of NIV. Pneumothorax and massive hemoptysis occurred independently in 4 cases.

CONCLUSIONS

NIV is being used in cystic fibrosis as adjunct therapy for the management of advanced lung disease in a similar fashion to other chronic respiratory conditions. Adherence to NIV treatment can stabilize lung function but does not reduce pulmonary exacerbations or intravenous antibiotic requirement.

Neuralgic amyotrophy presenting to an accident and emergency department

Two patients with neuralgic amyotrophy (Parsonage-Turner syndrome) are described. Problems arising from the shoulder girdle commonly present to accident and emergency (A&E) departments. Neuralgic amyotrophy is an infrequent neuromuscular disorder which predominantly affects the shoulder girdle. Characterised by severe pain followed by muscle weakness, atrophy, and variable sensory deficits, the diagnosis is based on history and physical findings and is confirmed by electromyography. The prognosis is excellent and treatment is supportive using analgesia and physiotherapy.

Recurrent noncardiac pulmonary edema accompanying pregnancy-induced hypertension

Severe pulmonary edema occurred in a patient during the third trimester of two consecutive pregnancies, 17 months apart. Noncardiac origin of the pulmonary edema was demonstrated by normal pulmonary capillary wedge pressures, normal roentgenographic cardiac dimensions with absence of effusions, normal echocardiographic ejection fraction, and elevated thermodilution cardiac outputs; moderate reduction in serum albumin levels may have contributed. In the setting of pregnancy-induced hypertension, the development of ARDS on each occasion suggests a pathophysiologic link.

Hepatitis B prevalence in an unregistered prenatal population. Implications for neonatal therapy

STUDY OBJECTIVE

To evaluate the risk and associated cofactors for hepatitis B infection in inner-city pregnant women not registered for prenatal care.

DESIGN

Fifteen-month survey of 208 patients not registered for prenatal care, compared with 1555 women registered for prenatal care during the same period.

SETTING

An urban university hospital prenatal clinic and labor unit.

RESULTS

Unregistered patients had a significantly higher rate of hepatitis B surface antigen positivity than patients who had registered with the clinic (6.7% vs 0.8%; P less than .0001). Unregistered patients with positive results of urine drug screening (46%) had a relative risk for seropositivity of 29.2%, compared with registered patients who did not have histories of illicit drug use (95% confidence interval, 25.9% to 32.4%), while registered patients with past histories of drug use had a relative risk of 6.7%, compared with the reference group that did not have histories of drug use (95% confidence interval, 1.8% to 24.0%).

CONCLUSIONS

Among inner-city pregnant women not registered for prenatal care, a positive result of urine drug screening is a rapidly available marker for increased risk of hepatitis B surface antigen positivity. Infants born to unregistered women with positive results of urine drug screening before maternal hepatitis B surface antigen results are available may warrant empiric initiation of hepatitis B virus-specific prophylaxis.

Effects of fetal anemia on PO2 difference between uterine venous and umbilical venous blood

In the fetus, the functional equivalent of the alveolar-arterial blood PO2 difference is the uterine venous-umbilical venous blood PO2 difference. Generally, factors that affect one of the venous blood PO2s produce equivalent effects on the other. We previously showed that fetal anemia produces increases in umbilical venous blood PO2. To determine whether this increase was associated either with equivalent increases in uterine venous blood PO2 or with reductions in the uterine venous-umbilical venous PO2 difference, we studied eight chronically catheterized pregnant sheep and fetal lambs. Measurements of O2 gas tensions and O2 saturations, uterine and umbilical blood flows, and uterine, fetal, and placental O2 consumptions were made in animals with normal fetal hematocrits and during reductions in fetal hematocrit of 35% (moderate fetal anemia) or 60% (severe fetal anemia). Fetal anemia produced reductions in the uterine venous-umbilical venous blood PO2 difference; in some cases the PO2 difference was less than 2 mmHg (compared with normal values of 20 mmHg). The development of both moderate and severe fetal anemia had no effect on uterine and umbilical blood flows or placental O2 consumption but did reduce total uterine and fetal O2 consumption. These data indicate that fetal anemia induces changes in placental gas transport. These changes may be due to improvements in gas diffusion, reductions in perfusion mismatching, or reductions in vascular shunting. Our data further indicate that placental O2 consumption rate, which is high in normal pregnant sheep, plays no role in the maintenance of the uterine venous-umbilical venous blood PO2 difference in pregnant sheep.

Pregnancy and liver transplantation

To define the risks and outcomes associated with pregnancy and liver transplantation, we reviewed our experience in managing eight pregnant women who had undergone orthotopic liver transplantation. Seven patients conceived after transplantation; the interval from transplantation to conception ranged from 3 weeks to 24 months. One patient received an allograft at 26 weeks' gestation for hepatic failure secondary to acute fulminant hepatitis B. Of the seven patients who conceived after transplantation, six had live births and one electively terminated her pregnancy. Five patients developed worsening hypertension and/or preeclampsia. Three patients developed severe preeclampsia and required delivery. One patient suffered acute allograft rejection during pregnancy which was successfully treated with corticosteroids. Two patients had persistent elevation of serum transaminases and two had severe anemia. The mean gestational age at delivery was 32.8 weeks. Of the six live births to women who conceived after transplantation, five infants survived and are well and one infant died. There were no congenital anomalies. All mothers are alive at this time. Pregnancy in recipients of hepatic allografts is associated with good perinatal outcome, but there is an increased risk of preeclampsia, worsening hypertension, and preterm delivery. Pregnancy does not appear to have a deleterious effect on hepatic graft function or survival. Joint management of these patients by a transplant specialist and a perinatologist is essential.

Pharmacokinetics of ritodrine administered intravenously: recommendations for changes in the current regimen

We define the pharmacokinetics of ritodrine in 13 pregnant women who received the drug intravenously. With constant infusion of 50 micrograms/minute, steady state ritodrine concentrations reached 28 +/- 11 ng/ml (SD) with a range of 15 to 45 ng/ml. This wide variation is a result of differences in plasma clearance, which ranged from 1.0 to 3.3 L/min, mean 1.94 +/- 0.71 L/min. The apparent volume of distribution was 6.95 +/- 3.54 L/kg, indicating that ritodrine is extensively bound to extravascular tissue. When an infusion of ritodrine is stopped, plasma concentrations fall rapidly initially with a distribution half-life of 5.9 +/- 6.0 minutes. After the initial rapid fall, plasma concentrations decrease more slowly with a mean disposition half-life of 156 +/- 51 minutes. On the basis of the pharmacokinetic parameters defined, we recommend that the current infusion regimen for ritodrine be changed. The infusion rate of ritodrine should start at 50 micrograms/minute rather than 100 micrograms/minute. The maximal infusion rate of 350 micrograms/minute should be increased and once labor is inhibited, the infusion rate should be reduced.

Placental abruption in the preterm gestation: an association with chorioamnionitis

Thirty-seven women with acute severe preterm placental abruption were compared with a control group of 51 women requiring preterm delivery for a medical complication of pregnancy. Histologic chorioamnionitis and funisitis were present significantly more often in patients with abruption than in control patients (41 versus 4%; P less than .0001). No patient in either group had clinical evidence of chorioamnionitis. We conclude that a significant association exists between preterm placental abruption and histologic chorioamnionitis.

Effects of reductions in hemoglobin-oxygen affinity and hematocrit level on oxygen consumption and acid-base state in fetal lambs

To determine whether the high oxygen affinity of fetal blood, compared with that of the adult, is advantageous to the fetus during fetal anemia we studied 16 chronically catheterized fetal lambs. Half of the lambs had hemoglobin-oxygen affinity reduced acutely by isovolemic exchange transfusion with fresh adult whole blood; the other half served as controls. In both groups of fetuses, we measured fetal oxygen delivery, oxygen consumption, and acid-base state at normal fetal hematocrit levels and during reductions in the hematocrit level of 30% (moderate anemia) and 60% (severe anemia) produced by isovolemic exchange transfusions with plasma. At normal fetal hematocrit levels, reductions in hemoglobin-oxygen affinity had no effect on fetal oxygen consumption or acid-base state. During moderate anemia, fetal oxygen delivery decreased in both series of fetuses, but oxygen consumption and base excess fell only in those fetuses whose circulations contained adult hemoglobin. During severe anemia, oxygen consumption and base excess decreased in both groups of fetuses, although these changes were more pronounced in fetuses with adult hemoglobin than in those with fetal hemoglobin. Our data indicate that, even though a high hemoglobin-oxygen affinity may not be essential to a healthy fetus, it is critical for normal metabolism in a fetus subjected to a hypoxic stress such as anemia.