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The use of extracorporeal carbon dioxide removal in the management of life-threatening bronchospasm due to influenza infection.

SUMMARY

We report the use of the Novalung[R] interventional Lung Assist extracorporeal carbon dioxide removal device, (Novalung GmbH, L otzenadcer 3, D-72379 Hechingen, Germany) to treat a 46-year-old female with life-threatening bronchospasm secondary to influenza infection. Despite maximal treatment she developed severe hypercapnia and acidosis. The necessity for high inflation pressures led to the development of gross surgical emphysema. Use of the interventional Lung Assist enabled a rapid correction of hypercapnoea and addosis, allowing a reduction in airway pressures, reducing further barotrauma. Subsequent resolution of the inflammatory process allowed removal of the interventional Lung Assist after 11 days. She was successfully weaned from mechanical ventilation and made a full recovery.

Key Words: complications, bronchospasm, barotrauma, asthma, carbon dioxide, extracorporeal removal

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CASE HISTORY

A 46-year-old woman was admitted to hospital with a five-day history of cough, fever and dyspnoea. She was a smoker, with a history of mild asthma for which she occasionally took a salbutamol metered dose inhaler. On admission she had bronchospasm with widespread expiratory wheeze. Chest X-ray showed hyperexpanded lung fields with no evidence of consolidation. Despite treatment with nebulised salbutamol, intravenous aminophylline, antibiotics and corticosteroids, she deteriorated and required mechanical ventilation in the critical care unit.

Despite the addition of intravenous salbutamol, magnesium, ketamine and subsequently neuromuscular paralysis, her lungs were difficult to ventilate. Peak airway pressures in excess of 40 cm[H.sub.2]O generated tidal volumes of less than 4 ml/kg. Serial alterations to rate, pressure and inspiratory/expiratory ratio were made without improvement in minute ventilation. Her [P.sub.a]C[O.sub.2] was persistently above 12 kPa resulting in a pH below 7. The [P.sub.a][O.sub.2] was maintained throughout above 12 kPa, with a maximal inspired oxygen concentration of 0.8.

During the first 24 hours of artificial ventilation she developed significant surgical emphysema affecting the head, neck and chest, with associated pneumomediastinum and pneumopericardium. Cardiovascular decompensation became evident after 24 hours of aggressive ventilation. She required cautious intravascular resuscitation with fluid and a noradrenaline infusion to maintain a mean arterial pressure above 70 mmHg. Despite these measures she developed a metabolic acidosis and continuous veno-venous haemofiltration was initiated when her base deficit fell to 6 mEq/l. In addition, Heliox (BOC Medical, Priestley Road, Worsley, Manchester M28 2UT, UK) was entrained into the inspiratory limb of the Puritan Bennett ventilator as a strategy to reduce dynamic hyperinflation and improve gaseous exchange (1,2). These interventions however, only had a limited effect on hypercapnia and pH.

After 48 hours her overall condition had deteriorated further. Having exhausted all other locally available strategies and after discussion with the regional ECMO unit (Glenfield Hospital, Leicester, UK), the interventional Lung Assist (Novalung[R] GmbH, Lotzenacker 3, D-72379 Hechingen, Germany) (iLA) was considered. A 13 French gauge femoral arterial catheter was sited into the left femoral artery and a 15 French gauge femoral venous catheter into the right femoral vein. Following systemic anticoagulation with unfractionated heparin, the iLA circuit was connected and initiated with minimal effect on mean arterial pressure.

[FIGURE 1 OMITTED]

Implementation of the iLA produced a rapid improvement in [P.sub.a]C[O.sub.2] (Figure 1). After two hours the [P.sub.a]C[O.sub.2] and pH were within normal limits and her general condition improved. In the 24 hours following institution of extracorporeal C[O.sub.2] replacement we were able to withdraw her vasopressor and discontinue haemofiltration. Twelve days after admission to critical care she had a tracheostomy performed with the iLA in situ after cessation of anticoagulation for six hours. The iLA was required for a total of 11 days and removed without complications.

Mechanical ventilation was required for a total of 19 days. She was discharged from the critical care unit after 30 days and left hospital after 44 days. The patient made a full recovery and consented to the submission of this case report.

DISCUSSION

Supportive mechanical ventilation is the cornerstone of treatment in acute lung injury. In many cases the severity of airway inflammation is such that a lung protective strategy is difficult to maintain. Aggressive ventilation with high airway pressures is sometimes necessary to maintain adequate gas exchange. Pump-driven extracorporeal membrane oxygenation (ECMO) has been developed for use in those patients with persistent hypoxaemia and/or hypercapnia unresponsive to conventional treatment (3). Early studies demonstrated an outcome benefit for children (4,5) but not for adults (6). The results of a more recent randomised multicentre trial of adult ECMO are awaited (Conventional Ventilation or ECMO for Severe Adult Respiratory Failure trial).

Conventional ECMO has inherent disadvantages. It is expensive and requires specially trained staff based in large regional centres. The need for full anticoagulation can lead to major bleeding complications and the large mechanically pumped extracorporeal circuit provokes a significant systemic inflammatory response. For these reasons ECMO is rarely used in adults. With the introduction of small, easy to use assist devices, such as the iLA, extracorporeal techniques are a viable treatment option for difficult cases in the intensive care unit.

In 1983 Ohtake et al described a method for extracorporeal gas exchange using an arteriovenous hollow fibre oxygenator (7). They called it "Pumpless arteriovenous ECMO". Such devices, however, have been renamed "Extra Corporeal C[O.sub.2] Removal" devices as they are efficient at clearing C[O.sub.2] with only a limited ability to oxygenate.

The iLA circuit has a total volume of only 250 ml and comprises a 13 to 19 French gauge arterial catheter, a single use gas exchange cartridge and a 15 to 21 French gauge venous return catheter. The cartridge consists of a hollow fibre polymethylpentene diffusion membrane network with an effective surface area of 1.3 [m.sup.2]. The network is geometrically designed to offer low resistance to blood flow. Oxygen flows as a carrier gas within the hollow fibres and C[O.sub.2] moves by selective diffusion across the concentration gradient from the blood. Polypeptides and unfractionated heparin are bonded to the membrane exposed to the circulating blood to improve biocompatibility and reduce the incidence of thrombosis. Blood flow across the device is determined by mean arterial pressure. A mean arterial pressure of 70 mmHg produces a flow rate of 1 to 1.5 1/min and eliminates 200 ml/min C[O.sub.2]. C[O.sub.2] clearance is dependent on blood flow and oxygen flow. Carrier gas flow of up to 12 l/min can be used and is usually titrated carefully to effect. Given that arterial blood perfuses the device, only in conditions of severe hypoxaemia can any significant oxygenation be achieved (8). Femoral vessels are the preferred site of cannulation, with the device placed between the legs (Figure 2).

[FIGURE 2 OMITTED]

The iLA can be rapidly implemented in the intensive unit without the need for patient transfer. It is licensed to be left in place for 29 days without maintenance. It has a small priming volume and is fully heparin bonded. Formal anticoagulation is recommended but can be interrupted to allow therapeutic interventions such as, in this case, tracheostomy. It also been used successfully without anticoagulation in a patient with intracranial haemorrhage (9). No artificial pump is used in the system, reducing mechanical damage to blood components and subsequent inflammatory response.

Arterial cannulation may lead to limb ischaemia in around 10% of cases in a reported series (8). As 20 to 25% of the effective cardiac output is passed through the circuit, its use is contraindicated in patients with cardiac insufficiency. Hypotensive patients with adequate cardiac output must be given vasopressors to achieve the required mean arterial pressure of 70 mmHg. Once established the circuit requires no maintenance other than continuous oxygen supply.

In this case the underlying pathology was an infective exacerbation of asthma caused by influenza A as diagnosed by direct immunofluorescence of bronchoalveolar lavage.

This case demonstrates that the Novalung iLA can be safely used in critical care units away from specialist centres, where it is a useful adjunct in the treatment of life-threatening hypercapnia and acidosis that is unresponsive to conventional therapies. It facilitates a protective ventilatory strategy, reducing iatrogenic lung injury, while the underlying pathological process resolves.

Accepted for publication on March 17, 2008.

REFERENCES

(1.) Shine ST, Gluck FH. The use of helium-oxygen mixtures in the support of patients with status asthmaticus and respiratory acidosis. J Asthma 1989; 26:177-180.

(2.) Kass JE, Castriotta RJ. Heliox therapy in acute severe asthma. Chest 1995; 107:757-760.

(3.) Zapol WM, Snider MT, Hill JD, Fallat RJ, Bartlett RH, Edmunds LH et al. Extracorporeal membrane oxygenation in severe acute respiratory failure. A randomised prospective study. JAMA 1979; 242:2193-2196.

(4.) Bartlett RH, Gazzaniga AB, Jefferies MR. Extracorporeal Membrane Oxygenation (ECMO) cardiopulmonary support in infancy. Trans Am Soc Artif Intern Organs 1976; 22:80-93.

(5.) Bartlett RH, Roloff DW, Custer JR, Younger JG, Hirschl RB. Extracorporeal life support: The University of Michigan experience. JAMA 2000; 283:904-908.

(6.) Morris AH, Wallace CJ, Menlove RL, Clemmer TP, Orme JF Jr, Weaver LK et al. Randomized clinical trial of pressure-controlled inverse ratio ventilation and extracorporeal C[O.sub.2] removal for adult respiratory distress syndrome. Am J Respir Crit Care Med 1994; 149:295-305.

(7.) Ohtake S, Kawashima Y, Hirose H, Matsuda H, Nakano S, Kaku K et al. Experimental evaluation of pumpless arteriovenous ECMO with polypropylene hollow fiber membrane oxygenator for partial respiratory support. Trans Am Soc Artif Intern Organs 1983; 29:237-241.

(8.) Bein T, Weber F, Philipp A, Prasser C, Pfeifer M, Schmid FX et al. A new pumpless extracorporeal interventional lung assist in critical hypoxemia/hypercapnia. Crit Care Med 2006; 34:1372-1377.

(9.) Mallick A Elliot S, McKinlay J. Extracorporeal carbon dioxide removal using the Novalung in a patient with intracranial bleeding. Anaesthesia 2007; 62:72-74.

S. TWIGG *, G. J. GIBBON [[dagger]], T. PERRIS [[double dagger]]

Department of Critical Care Medicine Gloucestershire Royal Hospital, Gloucester United Kingdom

* M.A., M.B., B.Chir., M.R.C.P, F.R.C.A., Dip.I.C.M., Consultant in Anaesthetics and Critical Care Medicine.

[[dagger]] B.Med.Sci., B.M.B.S., M.R.C.P., F.R.C.A., Specialist Registrar in Anaesthetics.

[[double dagger]] M.B., Ch.B., F.R.C.A., Consultant in Anaesthetics and Critical Care Medicine.

Address for reprints: Dr G. Gibbon, 6 Dongola Road, Bristol, BS7 9HQ, UK.
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Article Details
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Title Annotation:Case Reports
Author:Twigg, S.; Gibbon, G.J.; Perris, T.
Publication:Anaesthesia and Intensive Care
Article Type:Case study
Geographic Code:4EUUK
Date:Jul 1, 2008
Words:1737
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