Wie sollte man einen starken Husten behandeln?

"Ein Dogma gerät ins Wanken" überschreibt die Ärzte-Wochenzeitung Medical Tribune (Ausgabe 14.Mai 2004) einen Artikel bei dem es um die Frage geht, ob Kranke bei starkem Husten aufgefordert werden sollen viel zu trinken oder lieber nicht.
Dabei bezieht sich der Autor auf eine Untersuchung die im renommierten British Medical Journal publiziert wurde. In diesem Artikel hatten australische Forscher darauf hingewiesen, dass es bisher keine überzeugenden wissenschaftlichen Belage dafür gibt, dass eine erhöhte Flüssigkeitszufuhr tatsächlich bei jeder Art von Husten die Beschwerden lindert.
Tatsächlich gibt es sogar Hinweise darauf, dass eine erhöhte Flüssigkeitszufuhr - insbesondere bei Entzündungen der unteren Luftwege (Lungenentzündung)- schädlich sein kann und in seltenen Ausnahmefällen sogar in Verdacht geraten ist, zu tödlichen Komplikationen beigetragen zu haben.
Welche Konsequenzen sollten aus diesem neuen Gesichtspunkt gezogen werden?

Es erscheint bei der unsicheren Datenlage derzeit sinnvoll zu sein, dass Betroffene diese Problematik mit den behandelnden Ärzten zumindest diskutieren und sich selbst so lange auf eine "normale" Flüssigkeitszufuhr beschränken bis eine Lungenentzündung durch den Arzt ausgeschlossen wurde.

BMJ 2004;328:499-500 (28 February),

"Drink plenty of fluids": a systematic review of evidence for this recommendation in acute respiratory infections

Michelle P B Guppy, academic general practice registrar1, Sharon M Mickan, senior research fellow1, Chris B Del Mar, professor of general practice1

1 Centre for General Practice, Medical School, University of Queensland, Herston, 4006, Queensland, Australia

Correspondence to: C B Del Mar c.delmar@cgp.uq.edu.au


Doctors often recommend drinking extra fluids to patients with respiratory infections. Theoretical benefits for this advice are replacing insensible fluid losses from fever and respiratory tract evaporation, correcting dehydration from reduced intake, and reducing the viscosity of mucus.1 2 To many this advice is self evident and justified on the basis that even if the benefit is uncertain, or at best small, at least it is harmless.

However, there are theoretical reasons for increased fluid intake to cause harm. Antidiuretic hormone conserves fluid by stimulating water reabsorption from the renal collecting ducts. Increased antidiuretic hormone secretion has been reported in adults and children with lower respiratory tract infections of bronchitis, bronchiolitis, and pneumonia of viral and bacterial aetiology.3 4 It is uncertain if this also occurs in upper respiratory tract infections.

Several mechanisms have been proposed for this increased hormone secretion, acting through fever, hypoxia, hypercarbia, pain, emotion, or nausea. Secretion may be stimulated by a resetting of osmostat receptors to lower levels.3 Also, lung hyperinflation and pulmonary infiltrates may stimulate hormone secretion by causing a false perception of hypovolaemia by intrathoracic receptors.4 This would be in keeping with findings that antidiuretic hormone secretion in pneumonia increases proportionally with the extent of lung parenchymal involvement.3

Giving extra fluids while antidiuretic hormone secretion is increased may theoretically lead to hyponatraemia and fluid overload. Clinical symptoms of hyponatraemia are irritability, confusion, lethargy, coma, and convulsions. Fluid restriction may be appropriate management to prevent this.


Methods and results

To determine whether recommending increased fluids was beneficial or harmful, we undertook a systematic review and posed three questions:

Does recommending increased fluid intake for acute respiratory infections improve duration and severity of symptoms?

Are there adverse effects from this recommendation? Are any benefits or harm related to site (upper or lower respiratory tract) or severity of illness?

Using the Cochrane Acute Respiratory Infections Group search strategy, together with additional terms (see bmj.com for details), we did a conventional search of the Cochrane Central Register of Controlled Trials, Medline (1966-2003), Embase (1974-2003), and Current Contents (1966-2003). We examined references of relevant papers and contacted experts in the subject.

We found no randomised controlled trials comparing increased and restricted fluid regimens in patients with respiratory infections. Two prospective prevalence studies reported hyponatraemia at rates of 31% and 45% for children with moderate to severe pneumonia (see table).1 2 None of these children showed clinical signs of dehydration. Symptoms associated with hyponatraemia were not reported, but four children with a serum sodium below 125 mmol/l died during one study.


We also found several case series in which patients with respiratory infections developed hyponatraemia, of which some were symptomatic (table).5 These patients were all successfully treated with fluid restriction.


Comment

We found data to suggest that giving increased fluids to patients with respiratory infections may cause harm. To date there are no randomised controlled trials to provide definitive evidence, and these need to be done. Until we have this evidence, we should be cautious about universally recommending increased fluids to patients, especially those with infections of the lower respiratory tract.




References


1. Shann F, Germer S. Hyponatraemia associated with pneumonia or bacterial meningitis. Arch Dis Child 1985;60: 963-6.[Abstract]
2. Dhawan A, Narang A, Singhi S. Hyponatraemia and the inappropriate ADH syndrome in pneumonia. Ann Trop Paediatr 1992;12: 455-62.[ISI][Medline]
3. Dreyfuss D, Leviel F, Paillard M, Rahmani J, Coste F. Acute infectious pneumonia is accompanied by latent vasopressin-dependent impairment of renal water excretion. Am Rev Respir Dis 1988;138: 583-9.[ISI][Medline]
4. Gozal D, Colin AA, Jaffe M, Hochberg Z. Water, electrolyte, and endocrine homeostasis in infants with bronchiolitis. Pediatr Res 1990;27: 204-9.[Abstract]
5. Rivers RP, Forsling ML, Olver RP. Inappropriate secretion of antidiuretic hormone in infants with respiratory infections. Arch Dis Child 1981;56: 358-63.[Abstract]


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