Novel H1N1 influenza infection in intensive care unit

Dear Editor, I read the recent report on novel H1N1 influenza infection by Chacko et al.,[1] with great interest. Chacko et al. concluded, “2009 H1N1 infection caused severe disease in relatively young patients without significant co-morbidities, characterized by severe hypoxemia and the requirement for prolonged mechanical ventilation” and “extra-pulmonary organ failure included circulatory and renal failure”.[1] The data from this work are similar to a recent report from Spain.[2] I would like to add some discussions on this work. First, there is no doubt that the novel H1N1 influenza can cause severe disease in healthy subjects. However, based on this work, it might not be possible to note that all patients have no co-morbidities since there are no data on health status of all cases prior to the present illness. The cause of detected prolonged mechanical ventilation should be discussed. The presented data that the affected cases had to be on ventilator for a week or more is not different from the cases with classical H1N1 influenza virus infection.[3] This might be due to no significant difference in pathogenesis between classical and novel H1N1 influenza infections. Finally, the extrapulmonary organ failure is important. Although it is not common, it is detectable.[4] However, based on personal experience, it can be said that the heart failure is extremely rare.[5]


Novel H1N1 influenza infection in intensive care unit
Dear Editor, I read the recent report on novel H1N1 influenza infection by Chacko et al., [1] with great interest. Chacko et al. concluded, "2009 H1N1 infection caused severe disease in relatively young patients without significant co-morbidities, characterized by severe hypoxemia and the requirement for prolonged mechanical ventilation" and "extra-pulmonary organ failure included circulatory and renal failure". [1] The data from this work are similar to a recent report from Spain. [2] I would like to add some discussions on this work. First, there is no doubt that the novel H1N1 influenza can cause severe disease in healthy subjects. However, based on this work, it might not be possible to note that all patients have no co-morbidities since there are no data on health status of all cases prior to the present illness. The cause of detected prolonged mechanical ventilation should be discussed. The presented data that the affected cases had to be on ventilator for a week or more is not different from the cases with classical H1N1 influenza virus infection. [3] This might be due to no significant difference in pathogenesis between classical and novel H1N1 influenza infections. Finally, the extrapulmonary organ failure is important. Although it is not common, it is detectable. [4] However, based on personal experience, it can be said that the heart failure is extremely rare. [5] Dear Editor, We thank the author for showing interest in our case series of patients admitted to our multidisciplinary intensive care unit last year during the first wave of the 2009 H1N1 pandemic. [1] There are many studies, including ours, which have clearly shown that the 2009 H1N1 infection tends be more common in the previously well, relatively younger subgroup of patients. [2][3][4][5] Contrary to what the author suggests, many of our patients had underlying risk factors, although they belonged to the relatively younger age group. The median age in our series was 35 years (IQR 28.2-42.8). We sought for and identified risk factors in 64.1% of our patients -these included obesity, pregnancy, hypertension, diabetes, asthma, chronic obstructive pulmonary disease, renal failure and immunosuppression.
Prolonged ventilatory support is often required for respiratory failure from 2009 H1N1 infection. The median duration of ventilator support in our series was 10 days with an IQR of 4-22 days, which is similar to previous experience. [4,6] It is clear that severe 2009 H1N1 infection can test intensive care resources in a country like ours with serious limitation of facilities in the public sector, where the large majority of such patients are likely to be cared for.

The lung bears the brunt of the disease in 2009
Right subclavian artery cannulation: Is chest roentgenogram sufficient to diagnose the complication?
Dear Editor, I read with interest the letter to the editor, "Finding on a chest radiograph: A dangerous complication of subclavian vein cannulation" by Srinivasan and Kumar. [1] The inference of the authors seems to be simple, and is based on the prior, yet limited, reports of the radiographic findings of inadvertent subclavian artery cannulation and interpretation of the anatomy of the great vessels of body. [2,3] However, a closer look reveals the omission of many simple and easily available methods that should have been used to further confirm the diagnosis before abruptly removing the catheter in the hemodynamically unstable patient.
Ultrasound-guided insertion of central venous cannulation and trans-thoracic or trans-esophageal Doppler, when available, are the most reliable techniques to diagnose subclavian artery cannulation. However, these may not be readily available and need expertise. Pressure tracings using pressure transducer can also differentiate between venous or arterial cannulation. [3] However, when not available, various alternate bedside techniques should be used in addition to chest roentgenogram for confirming the subclavian artery malpositioning of central venous catheter.
Absence of free flow of intravenous fluid may be possible even if the catheter tip is in the lumen of subclavian vein with the tip abutting walls of the vein. Further, pulsatile movements of the fluid column (at a rate similar to the patient's heart rate) should appear if the catheter is in artery, at least when the pulse pressure is 40 mmHg, i.e. ≈55 cm of water (as the patient's blood pressure was 80/40 mmHg). Blood gas analysis of the samples aspirated from the central venous catheter lumen and from the peripheral artery (e.g. radial artery) can be compared in such confusing situations. This method could be a safe, easy and reliable method to diagnose an inadvertent arterial cannulation, especially in intensive care unit settings. www.ijccm.org H1N1 infection. The author suggests that myocardial dysfunction may be a relatively rare manifestation of 2009 H1N1 infection. However, extrapulmonary organ failure including shock is a common feature of severe 2009 H1N1 infection in the intensive care unit. [4] A significant number (58.1%) of our patients required vasopressor support -it is quite possible that the relatively high dose of analgesic and sedative drugs that we employed to facilitate mechanical ventilation could have substantially contributed to this. We did not subject our patients to systematic echocardiographic studies; however, there is evidence to suggest that subclinical cardiac dysfunction, as estimated by doppler echocardiography, may be common in these patients. [7] Rapidly progressive, fulminant myocaridits has also been reported following 2009 H1N1 infection. [8]