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Successful Aeromedical Transport Using Inhaled Prostacyclin for a Patient With Life-Threatening Hypoxemia^*

^* From the Respiratory Care Department (Mssrs. Reily and Tollok, and Ms. Mallitz), Hospital of the University of Pennsylvania, Philadelphia, PA; and the Departments of Anesthesia (Dr. Hanson) and Medicine (Dr. Fuchs), Pulmonary, Allergy, and Critical Care Division, University of Pennsylvania, Philadelphia, PA.

Correspondence to: Barry D. Fuchs, MD, FCCP, Medical Director, Medical Intensive Care Unit and Respiratory Care Services, Hospital of the University of Pennsylvania, University of Pennsylvania Health System, 3400 Spruce St–Founders 9.066, Philadelphia, PA 19104; e-mail: barry.fuchs{at}uphs.upenn.edu

	Abstract

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Our aim was to describe the technique and results of using inhaled prostacyclin (iPGI₂) to enable the safe interhospital helicopter transport of a patient with ARDS complicated by life-threatening hypoxemia. The case describes a 32-year-old women with ARDS complicated by life-threatening hypoxemia who was referred to our ARDS referral center for further management. Multiple attempts to place the patient on the transport ventilator failed because of severe hypoxemia. After the administration of iPGI₂, oxygen saturation improved significantly, enabling the transport to occur safely by medevac helicopter. iPGI₂ is a valuable adjunct for the medical transport team to enable the safe transport of critically ill patients with severe hypoxemia. The simple, lightweight, and portable delivery system makes it ideal for use during all forms of aeromedical transport.

Key Words: aeromedical transport • ARDS • interhospital transfer • life-threatening hypoxemia • prostacyclin • nitric oxide • pulmonary vasodilator

	Introduction

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Critically ill patients are frequently transferred to tertiary medical centers when a level of care or uniquetherapeutic modality is not available at the referring hospital. However, the risks associated with patient transport can be significant and are related to the clinical status of the patient.¹²³ Thus, prior to considering interhospital transport, it is essential to evaluate the risks for each patient to ensure that the potential clinical benefits outweigh the risks. On occasion, the transport must be cancelled when repeated attempts to move a high-risk patient from their ICU environment are met with failure, despite all efforts to stabilize the patient.

Ventilator-dependent patients with ARDS and severe hypoxemia represent a particularly difficult challenge for transport, despite the use of high levels of positive end-expiratory pressure (PEEP).⁴ These patients require more intensive monitoring and higher levels of respiratory support, including a portable or transport mechanical ventilator, high oxygen requirements, and uninterrupted PEEP therapy.⁵ Since there is little reserve in oxygenation, instability, as might occur with positional changes or inadvertent airway decompression, can be devastating. To reduce this risk and to minimize travel time, a helicopter staffed by personnel with specialized aeromedical training often is used for transport. However, in some patients the degree of hypoxemia is so severe that, in order to proceed with transport safely, unconventional therapeutic modalities to improve oxygenation have been used.⁶⁷ Extracorporeal membrane oxygenation and nitric oxide (NO) have been employed for use in transport airplanes; however, there is insufficient space in a transport helicopter to transport an adult patient and the delivery systems required with these modalities.

Prostacyclin (PGI₂) [epoprostenol, Flolan; GlaxoSmithKline; Triangle Park, NC], like NO, may be used to achieve selective pulmonary vasodilation when administered by inhalation.⁸ In contrast to NO, inhaled PGI₂ (iPGI₂) can be administered using a standard nebulizer that can easily fit into the cabin of a transport helicopter.⁹ In addition, several studies¹⁰ have demonstrated that iPGI₂ is equally as effective as NO in improving oxygenation in patients with ARDS. Since iPGI₂ can be administered through a standard nebulizer, it represents a practical option for use as an adjunctive treatment of hypoxemia in an adult patient being transported by helicopter. This report describes our first experience using iPGI₂ to facilitate the interhospital helicopter transport of a patient with life-threatening hypoxemia, secondary to ARDS, who was otherwise too ill to be transferred to our hospital by our aeromedical transport team.

	Case Report

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A 32-year-old woman who had been admitted to the hospital for menometrorrhagia underwent an uneventful dilation and curettage, and polypectomy. Her medical history was significant for polycystic ovarian syndrome, depression, chronic postnasal drip, and obesity. Shortly after undergoing surgery, while recovering from anesthesia, the patient became apneic and hypotensive. Excessive resistance to mask/bag manual ventilation was encountered, and the patient was reintubated. Bloody secretions emanating from the endotracheal tube were immediately observed. Mechanical ventilation was initiated using the assist-control mode with a tidal volume (VT) setting of 800 mL, a respiratory rate (RR) of 12 breaths/min, a fraction of inspired oxygen (FIO₂) of 1.0, and a PEEP of 10 cm H₂O, and was facilitated by heavy sedation and neuromuscular paralysis. Lung compliance was 31 mL/cm H₂O. Arterial blood gas measurements with these settings revealed a pH of 7.28, a PCO₂ of 51 mm Hg, and a PO₂ of 59 mm Hg. A chest radiograph showed the presence of bilateral pulmonary infiltrates. The patient developed fever (temperature, 102.9°F) and hypotension, for which therapy with a decongestant (Neosynephrine; Abbott Laboratories; Abbott Park, IL) at 125 µg per hour was started. Over the next 12 h, the patient continued to have difficulty with oxygenation, with a PaO₂ of 49 mm Hg, an FIO₂ of 1.0, and a PEEP of 10 cm H₂O. Lung compliance decreased from 31 to 20 mL/cm H₂O. The decision was made to transfer the patient to a tertiary referral center.

Considering the 50-mile distance to the Hospital of the University of Pennsylvania and the acuity of the patient, aeromedical transport via helicopter was chosen as the safest mode of transport. On arrival at the referring hospital, the air medical transport team (Penn Star) attempted to place the patient on a transport ventilator (model 750 portable critical care volume ventilator; Uni-Vent; West Caldwell, NJ). Numerous trials failed, with arterial oxygen saturation (SaO₂) falling to < 80%. The medical director of the aeromedical transport team was contacted, and it was decided to send a respiratory therapist with the expertise to transport the patient using iPGI₂. A pharmacist at our hospital prepared PGI₂ at a concentration of 30,000 ng/mL in a 50-mL syringe. Ventilator settings at the time were pressure-controlled ventilation with an inspiratory pressure of 30 cm H₂O, an RR of 20 breaths/min, an FIO₂ of 1.0, a PEEP of 14 cm H₂O, and an inspiratory/expiratory time ratio of 2:1. On these settings, the exhaled VT averaged 600 mL, with a minute ventilation of 12 L/min. Since the transport ventilator did not have pressure control ventilation capabilities, the patient was placed on assist-control mode with VT at 600 mL, RR at 14 breaths/min, FIO₂ of 1.0, a PEEP of 16 cm H₂O, and an inspiratory/expiratory time ratio of 1:1.

To administer the prescribed dose of 50 ng/kg/min, the respiratory therapist first diluted the PGI₂ at the bedside with the appropriate volume of normal saline solution and then placed it in the nebulizer. Therapy with iPGI₂ at a dose of 50 ng/kg/min was initiated using a mini-heart nebulizer placed at the distal end of the inspiratory limb of the ventilator circuit and set to a flow of 3 L/min, as per the recommendations of the nebulizer manufacturer. Approximately 3 min after starting iPGI₂ therapy, the SaO₂ increased from 82 to 91%. During the initial 10 min of iPGI₂ administration, the first attempt to place the patient on the transport ventilator failed, however, the second attempt, which was performed shortly thereafter, was successful. The patient then was monitored for an additional 25 min prior to transport, during which time the SaO₂ consistently remained at > 90%. The patient then was transported to the helicopter pad by ground ambulance and subsequently was brought to the Hospital of the University of Pennsylvania via a medevac helicopter. Throughout the transport, the SaO₂ of the patient remained at well > 90%, and eventually increased to 100% when she received 100% oxygen on arrival at our hospital. The transport took place without incident, and the patient arrived safely at our facility, 2 h and 15 min following the initiation of iPGI₂ therapy. The patient continued to receive iPGI₂ for 3 days and then was weaned successfully. The patient was extubated within 2 days and was discharged from the hospital 1 week later.

	Discussion

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Although the treatment of ARDS is largely supportive, severely ill patients’ likely derive benefit by transfer to tertiary care centers with specialized experience in ARDS care. Even with careful consideration of the risks involved, on occasion, attempts to transfer a patient are met with failure despite all efforts to maintain the same degree of ICU support. In our case, after several attempts, this young patient with ARDS could not be transported safely by the medivac team using conventional methods. It was only after the initiation of iPGI₂ therapy that the patient rapidly stabilized to allow the transport to occur. During the 2 h of administration of iPGI₂, SaO₂ rose to high 90% values, enabling the transport to be completed without incident. The ease of access to PGI₂, the minimal equipment and space required for drug delivery, and the simplicity of the method for drug administration were all important factors that enabled the rapid and successful deployment of this therapy, without much planning or education. To our knowledge, this is the first case report to describe the use of iPGI₂ in the treatment of a patient with life-threatening hypoxemia during aeromedical transport, to enable the patient to be transferred safely to a tertiary referral center.

Although NO would likely have improved oxygenation in our patient, similar to iPGI₂, NO was not a viable option in this clinical situation due to the space constraints in the helicopter cabin, since the size of the NO delivery system currently available in the United States is prohibitive.¹¹ The decision to use iPGI₂, and the ability to administer it "on the fly" as an immediate solution to the critical situation faced by the transport team in this case, were logical extensions of our current hospital guideline for the appropriate indications for iPGI₂ in critically ill adult hospitalized patients. Physicians in our health system were involved early on in the investigational use of NO. As a result, intensivists and surgeons were so comfortable using NO and impressed with its therapeutic effects, that NO was tested routinely in a variety of clinical situations both in the ICU and the operating room. Consequently, when the US Food and Drug Administration approved NO for use in patients, utilization continued unabated despite its high cost (estimated annual expense, $650,000). In an effort to control these costs, we implemented a drug substitution program using iPGI₂ to replace NO. The methodology that we used for drug preparation and administration has recently been published.⁹ iPGI₂ was chosen because its therapeutic efficacy was similar to that for NO for the treatment of hypoxemia and pulmonary hypertension, and because of its similar safety profile.⁸¹⁰ The intensivists and surgeons in our institution have fully adopted this practice change and have not prescribed NO in the last 12 months. Thus, when presented with the patient described in this case, our physicians and respiratory therapists were comfortable exporting the procedure for administrating iPGI₂ to the referring hospital and adapting it for use in the transport helicopter, to enable and ensure the safe transport of this critically ill patient to our hospital.

In summary, this case demonstrates that inhaled PGI₂ can be employed relatively easily and safely during helicopter transport for patients with severe hypoxemia (or pulmonary hypertension) who may otherwise not be considered safe for transport to a referring hospital.

	Footnotes

 
Abbreviations: FIO₂ = fraction of inspired oxygen; iPGI₂ = inhaled prostacyclin; NO = nitric oxide; PEEP = positive end-expiratory pressure; PGI₂ = prostacyclin; RR = respiratory rate; SaO₂ = arterial oxygen saturation; VT = tidal volume

Received for publication October 17, 2003. Accepted for publication December 18, 2003.

	References

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This Article Abstract Full Text (PDF) Free Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Add to My Personal Article Archive Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Reily, D. J. Articles by Fuchs, B. D. Search for Related Content PubMed PubMed Citation Articles by Reily, D. J. Articles by Fuchs, B. D.