Exposure of intensive-care staff to nitric oxide and nitrogen dioxide

Nitric oxide and nursing: a review

AIMS AND OBJECTIVES

This paper, therefore, aimed to review published literature in this area of pharmacological exploitation, to look at the therapeutic applications and clinical relevance and, by so doing, provide an accessible source for nurses to gain insight into the role of nitric oxide in the clinical setting.

BACKGROUND

Nitric oxide is a chemical mediator fundamental in the maintenance of adequate tissue perfusion and effective cardiovascular function; a major endogenous regulator of vascular tone. The use of nitrates are well established as pharmacological agents but it is only recently that it has been recognized that they act as a source of nitric oxide. Although widely addressed within the medical literature, there appears to be a paucity of nursing literature that explores either its physiological action, or its relevance to nursing practice.

CONCLUSIONS

This literature review provides an overview of the use of nitric oxide and its implications for nursing practice and patient outcomes.

RELEVANCE TO CLINICAL PRACTICE

Knowledge of nitric oxide and its action is pertinent to nurses across diverse specialities. It helps in understanding the principles of many nitrogen-derived medications which nurses administer to their patients on a daily basis. In terms of oral medication, this is demonstrated by greater insights into the action of nitrates, the appreciation of surprising developments in medications such as sildenafil and the development of new drug opportunities such as nitric oxide-non-steroidal anti-inflammatory drugs. Equally, the use of inhaled nitric oxide therapy in adult and neonatal critical care units appears to be an increasingly valuable source of treatment. A particular research challenge is found in the attempt at nitric oxide inhibition in the management of septic shock. The authors argue that understanding such esoteric areas of therapeutic developments is increasingly to be part of the repertoire of knowledge and skills for nurses in the 21st century.

Exposure of Intensive Care Unit Nurses to Nitric Oxide and Nitrogen Dioxide During Therapeutic Use of Inhaled Nitric Oxide in Adults With Acute Respiratory Distress Syndrome

• Background Although low concentrations of inhaled nitric oxide may by therapeutic, both nitric oxide and its oxidation product nitrogen dioxide are potentially toxic. The threshold limits for time-weighted average concentrations of nitric oxide and nitrogen dioxide issued by the American Conference of Governmental Industrial Hygienists are 25 and 3 ppm, respectively. The concentrations of these gases in the breathing space of hospital personnel during administration of nitric oxide to adult patients have not been reported.

• Methods Air was sampled from the breathing zone of intensive care unit nurses via collar-mounted tubes during the nurses’ routine duties attending patients who were receiving inhaled nitric oxide at 5 or 20 ppm. The exhaust ports of the mechanical ventilators were left open to the room. Nitric oxide and nitrogen dioxide were chemically assayed as nitrite from sorbent tubes by using spectrophotometry. Ambient nitric oxide levels were measured at sequential distances from the ventilator by using chemiluminescence.

• Results The time-weighted average concentrations of inspired gas for nurses during inhaled nitric oxide treatment were 0.45 ppm or less for nitric oxide and less than 0.29 ppm for nitrogen dioxide. Nitric oxide levels at the ventilator during delivery at 20 ppm were 9.2 ppm, but dropped off markedly beyond 0.6 m (2 ft), to a mean of about 30 ppb.

• Conclusion Inhaled nitric oxide therapy at doses up to 20 ppm does not appear to pose a risk of excessive occupational exposure to nitric oxide or nitrogen dioxide to nurses during routine delivery of critical care.

An evaluation of nitric oxide and nitrogen dioxide absorbers and filters

The absorbance of NO (5-90 ppm) and NO2 (0.5-4 ppm) by a number of absorbers and filters was assessed via bench testing. All absorbers (Sodasorb, Purafil CP, Purafil Select, Sofnolime, Sofnofil and 50/50 mix of Sofnolime/Sofnofil) except Sodasorb absorbed NO almost completely. Only Sofnolime absorbed NO2 completely while Sodasorb and the Sofnolime/Sofnofil 50/50 mix had absorbances between 47% and 90%. The absorbance of four filters (ILF100, ILF150, ILF200 and HgCONO) as well as Sofnolime and the Sofnolime/Sofnofil 50/50 mix was tested in the expiratory port of a Servo 900C ventilator All absorbers and filters produced a change in ventilator pressures. The HgCONO filter Sofnolime and the Sofnolime/Sofnofil 50/50 mix all absorbed NO. At 80 ppm NO, the HgCONO filter had 100% absorbance for four hours while Sofnolime's absorbance was significantly reduced after one hour. All filters and absorbers tested on the ventilator except the Sofnolime/Sofnofil 50/50 mix and the ILF150 filter absorbed NO2 completely for a period ranging from 90 minutes to four hours. We recommend the HgCONO filter and Sofnolime to absorb both NO and NO2. If absorption of NO2 only is required we recommend the HgCONO, ILF100 or ILF200 filters or the Sofnolime absorber.

Inhaled nitric oxide: technical aspects of administration and monitoring

OBJECTIVES

Clinical applications of inhaled nitric oxide (NO) therapy resulted in the development of delivery systems and monitoring devices applicable to routine clinical care. This article presents the various components necessary for an adequate clinical use of inhaled NO, and discusses the NO gas mixture cylinders, inhaled NO delivery techniques and specifications, monitoring devices, and ending with an exhaustive description of the scavengers of nitrogen oxides (NOx).

DATA SOURCES

Computerized search (CURRENT CONTENTS, MEDLINE) of published original research and review articles (approximately 200), conference abstracts and compendiums up to May 1997 (approximately 50), personal files, and contact with expert informants.

STUDY SELECTION

Technical, experimental, and clinical reports were selected from the recent English, French, German, and Spanish literature, if pertinent to the administration or monitoring of inhaled NO.

DATA EXTRACTION

The authors extracted all applicable data.

DATA SYNTHESIS

The production of NO gas mixture cylinders must be certified with respect to gas purity, stability, and concentration (limits between 100 and 1000 ppm), guaranteed calibration, and specific color. An ideal inhaled NO delivery device requires a synchronized delivery, a minimal production of nitrogen dioxide (NO2), and should be simple to use (verification, calibration, convenient flushing, cylinder change possible while in use and a simple alarm setting) with full information (high and low alarms and available precision monitoring of NO, NO2, and O2). Emergency and transport systems must be readily available. The choice of the monitoring device (chemiluminescence or electrochemistry) should be made based on the knowledge of their strength and weakness for a particular clinical application. Finally, scavengers of NOx should be used with caution until specific filters are proven safe and effective.

CONCLUSIONS

The great expectancies generated by inhaled NO action have led researchers to design personal inhaled NO delivery systems, but only with mitigated results. At present, medical companies are finding a financial interest in designing a delivery system which will suit the needs of clinicians and this, along with official governmental approval, will only then permit the use of inhaled NO safely and on a larger scale.