Comparison of the effects of acetazolamide and aminophylline on apnea incidence and on ventilatory response to CO2 in preterm infants

Drug effects on ventilatory control and upper airway physiology related to sleep apnea

Understanding the inter-relationship between pharmacological agents, ventilatory control, upper airway physiology and their consequent effects on sleep-disordered breathing may provide new directions for targeted drug therapy. Where available, this review focuses on human studies that contain both drug effects on sleep-disordered breathing and measures of ventilatory control or upper airway physiology. Many of the existing studies are limited in sample size or comprehensive methodology. At times, the presence of paradoxical findings highlights the complexity of drug therapy for OSA. The existing studies also highlight the importance of considering inter-individual pharmacokinetics and underlying causes of sleep apnea in interpreting drug effects on sleep-disordered breathing. Practical ways to assess an individual's ventilatory control and how it interacts with upper airway physiology is required for future targeted pharmacotherapy in sleep apnea.

Acetazolamide treatment for infantile central sleep apnea

Central sleep apnea is a common respiratory pattern in healthy neonates. Nevertheless, frequent central sleep apnea associated with drops in oxygen saturation may contribute to infantile morbidity. Recently, low-dose acetazolamide was shown to reduce symptomatic central sleep apnea in adults. We treated 12 infants, median conceptional age 42 weeks (range, 40-44 weeks), with central sleep apnea. In all cases, the central apnea index was >40/h total sleeping time (apnea > or = 3 sec). The cumulative duration of drops in oxygen saturation below 90% was more than 3 min/h total sleeping time. All individuals received acetazolamide 7 mg/kg/day (orally, divided in three doses) for 11 weeks. Polysomnography was begun 10 hours before the first dose and continued for 10 hours after the third dose. Polysomnography was repeated after 6 weeks of treatment and 1 week after acetazolamide therapy was discontinued. Comparison of the respiratory patterns before and after treatment (10-hour recording after the third dose) showed a decrease in the median central apnea index from 74/h (range, 42-152/h) to 13/h (range, 6-49/h). The median of the cumulative duration of drops in oxygen saturation below 90% decreased from 3.6 min/h (range, 3.1-9.2 min/h) to 0.07 min/h (range, 0-0.5 min/h). Basal oxygen saturation increased from 95 (92-97%) to 98% (96-99%). This improvement was maintained in the final polysomnography (12 weeks after therapy was begun and 1 week after completion of the 11-week course). No adverse effects were noted. We conclude that low-dose acetazolamide treatment may be useful for the treatment of central infantile sleep apnea associated with hypoxemia.

Diuretic therapy for newborn infants with posthemorrhagic ventricular dilatation

BACKGROUND

Intraventricular hemorrhage remains a serious complication of premature birth and post hemorrhagic hydrocephalus still has no satisfactory treatment. Acetazolamide and furosemide, which both reduce the production of cerebrospinal fluid, have been suggested as non-invasive therapies to reduce hydrocephalus and the need for ventriculo-peritoneal (V-P) shunting.

OBJECTIVES

The aim of this review was to determine whether the use of acetazolamide and furosemide improves outcome, especially shunt dependence, in infants developing post-hemorrhagic ventricular dilatation.

SEARCH STRATEGY

The standard search strategy of the Cochrane Collaboration was used.

SELECTION CRITERIA

Randomised, or quasi-randomised trials, of acetazolamide and/or furosemide compared with standard therapy in infants with IVH or post-hemorrhagic ventricular dilatation

DATA COLLECTION AND ANALYSIS

Data were extracted independently by each author and were analysed by the standard methods of the Cochrane Collaboration using relative risk (RR) and risk difference (RD), a fixed effect model and sensitivity analyses where appropriate.

MAIN RESULTS

There were two eligible trials: one randomized 16 infants and the other, 177. Neither showed a decreased risk for V-P shunt or for V-P shunt or death associated with acetazolamide and furosemide therapy. The larger trial showed that acetazolamide and furosemide treatment resulted in a borderline increase in the risk for motor impairment at one year (RR 1.27, CI 1.02 to 1.58; RD 0.16, CI 0.02 to 0.31), but did not significantly affect the risk for the combined outcome of delay, disability or motor impairment among survivors, or the risk of the combined outcome of death, delay, disability or impairment at one year. The larger trial showed that diuretic treatment increased the risk for nephrocalcinosis (RR 5.31, CI 1.90 to 14.84; RD 0.19, CI 0.09 to 0.29); meta-analysis confirmed this result.

REVIEWER'S CONCLUSIONS

Acetazolamide and furosemide therapy is neither effective nor safe in treating post hemorrhagic ventricular dilatation. Acetazolamide and furosemide cannot be recommended as therapy for post hemorrhagic hydrocephalus.

Aminophylline modulation of the mouse respiratory network changes during postnatal maturation

Aminophylline is a respiratory stimulant commonly used for the treatment of central apnea. Experiences from clinical practice, however, revealed that aminophylline is not reliably effective in preterm infants, whereas it is normally effective in infants and mature patients. In an established animal model for postnatal development of respiratory control mechanisms, we therefore examined the hypothesis that the clinical observations reflect a developmental change in the sensitivity of the central respiratory network to methylxanthines. The medullary respiratory network was isolated at different postnatal ages (postnatal days 1-13; P1-P13) in a transverse mouse brain stem slice preparation. This preparation contains the pre-Bötzinger complex (PBC), a region that is critical for generation of respiratory rhythm. Spontaneous rhythmic respiratory activity was recorded from the hypoglossal (XII) rootlets and from neurons in the PBC by using the whole cell patch clamp technique. Bath-applied aminophylline [20 microM] increased the frequency (+41%) in neonatal animals (P1-P6) without affecting the amplitude of respiratory burst activity in XII rootlets. The same concentration of aminophylline did not have any significant effect on the frequency of respiratory XII bursts but increased the amplitude (+31%) in juvenile animals (P7-P13). In the same age group, aminophylline also augmented the amplitude and the duration of respiratory synaptic drive currents in respiratory PBC neurons. The data demonstrate that augmentation of the respiratory output is due to direct enhancement of central respiratory network activity and increase of synaptic drive of hypoglossal motoneurons in juvenile, but not neonatal, animals. This indicates a developmental change in the efficacy of aminophylline to reinforce central respiratory network activity. Therefore, we believe that the variable success in treating respiratory disturbances in premature infants reflects maturational changes in the expression of receptors and/or intracellular signal pathways in the central respiratory network.

Risks and benefits of therapies for apnoea in premature infants

Apnoea in infants can result from a wide range of causes, and requires thorough evaluation before deciding on appropriate treatment. Continuous monitoring of premature infants with apnoea is mandatory in order to define the pathophysiology and type of apnoea; selection of treatment involves careful assessment of aetiology, as well as efficacy and tolerability in each individual case. The objective of treatment is to prevent the deleterious consequences of apnoeas that last >20 seconds and/or are associated with bradycardia, cyanosis or pallor, and occur more often than once an hour over a 12-hour period. Apnoea management involves both pharmacological and nonpharmacological treatment. We suggest methylxanthines as first-line therapy for idiopathic apnoeas; evidence suggests that caffeine is better tolerated and as efficacious as theophylline (since it is particularly efficacious against the 'central' component of idiopathic apnoea of prematurity). If treatment fails, additional measures such as doxapram may be appropriate when hypoventilation is present, or nasal continuous positive airway pressure when upper airway instability or obstructive apnoeas are predominant. Apnoea prophylaxis is an additional reason to advocate prenatal maturation with betamethasone. Weaning from treatment is attempted 4 to 5 days after complete resolution of apnoea, beginning with the last treatment introduced. Monitoring should be maintained for 4 to 5 days to detect any relapse of recurrent and severe apnoeas, which would lead to the resumption of the most recently withdrawn treatment.