Year : 2009 | Volume
| Issue : 1 | Page : 20-24
Use of continuous subglottic suction in established ventilator associated pneumonia
Ahmed A Alsaddique
King Fahad Cardiac Center, College of Medicine, King Saud University, P.O.Box 7805, Riyadh, 11472, Saudi Arabia
Ahmed A Alsaddique
King Fahad Cardiac Center, College of Medicine, King Saud University, P.O.Box 7805, Riyadh, 11472
Source of Support: None, Conflict of Interest: None
|Date of Web Publication||18-Jul-2009|
| Abstract|| |
Background. Pneumonia is the most common nosocomial infection in intensive care units. Most of ICUacquired pneumonias occur during mechanical ventilation; about half of them develop in the first four days after intubation. Ventilator-associated pneumonia (VAP) can be a lethal complication as it carries a mortality that may approach 50%.
Methods. Continuous subglottic suction was utilized in seventeen post cardiac surgery patients with established VAP as part of the management protocol. These patients were compared with a group of 12 patients who did not have continuous subglottic suction part of their management.
Results. Institution of continuous subglottic suction in patients with established ventilator associated pneumonia is of value in reducing the number of ventilator dependent days. It also decreases the likelihood of further deterioration in the pulmonary function and reduces the need for antimicrobial agents.
Conclusion. Continuous subglottic suction is beneficial in case of established VAP. It prevents further soilage of the airways, speeds up convalescence and shortens the ICU stay. Ideally, it should be instituted early on in case of prolonged mechanical ventilation as one of the effective measures for the prevention of this kind of pneumonia.
Keywords: Continuous subglottic suction; Ventilator associated pneumonia
|How to cite this article:|
Alsaddique AA. Use of continuous subglottic suction in established ventilator associated pneumonia. Saudi J Anaesth 2009;3:20-4
|How to cite this URL:|
Alsaddique AA. Use of continuous subglottic suction in established ventilator associated pneumonia. Saudi J Anaesth [serial online] 2009 [cited 2020 Apr 1];3:20-4. Available from: http://www.saudija.org/text.asp?2009/3/1/20/51830
| Introduction|| |
VAP that occurs within 48 to 72 hours after tracheal intubation is usually termed early-onset pneumonia; it often results from aspiration, which complicates the intubation process . VAP that occurs after this period is considered late-onset pneumonia. Earlyonset ventilator-associated pneumonia is most often due to antibiotic sensitive bacteria (e.g., oxacillinsensitive Staphylococcus aureus, Haemophilus influenzae d Streptococcus pneumoniae eas late-onset ventilator-associated pneumonia is frequently caused by antibiotic-resistant pathogens (e.g., oxacillin-resistant staph. aureus, pseudomonas aeruginosa, acinetobacter species, and enterobacter species ). Continuous subglottic suctioning is accomplished with a special endotracheal tube with a suction port in the dorsal lumen that resides just above the inflated balloon and permits aspiration of secretions in the subglottic space ,. This prevents pooling of these secretions, which could lead to aspiration. Research has shown that the organisms present in these secretions are the same as those found causing pneumonia in ventilated patients. The premise is that these secretions are aspirated by the ventilated patient causing the pneumonia. The Hi Lo Evac tube is one such a special endotracheal tube. This port can be attached to continuous suction or have intermittent suction applied via a syringe to remove secretions that accumulate above the cuff. The Hi Lo Evac tube (Hi-Lo Evac; Mallinckrodt; Athlone, Ireland) allows these secretions to be removed from the subglottic space, decreasing the possibility of them being aspirated and causing the pneumonia.
| Material and Methods|| |
With institutional review board approval, we retrospectively analyzed database and medical records of postoperative cardiac surgical patients of King Fahad Cardiac Center. The aim was to look into immunocompetent patients who required prolonged mechanical ventilation and were unstable to undergo re-intubation with the Hi-Low Evac endotracheal tube. A total of 17 patients were indentified. When it became feasible to switch to the Hi-Low Evac system they already had an established late onset VAP. Continuous subglottic suction was added to the standard management protocol (group I). This group was compared to a cohort of 12 immunocompetent patients with identical demographics and a comparable mean EuroSCORE who developed VAP under similar set of circumstances but did not have the Hi-Low Evac endotracheal tube and continuous subglottic suction as a part of the management protocol (group II).
Establishing the Diagnosis of VAP
VAP was diagnosed in patients who received mechanical ventilation for >48 hours. It was suspected when the presence of new and/or progressive pulmonary infiltrates was detected on a chest radiograph. In addition to two or more of the following criteria: fever (temperature > 38.5°C or hypothermia temperature < 36°C); leukocytosis (>_12 X 10 9 cells/L); purulent tracheobronchial secretions; or a reduction in the Pao 2 /fraction of inspired oxygen ratio >15% according to Centers for Disease Control and Prevention definitions . Patients with a clinical pulmonary infection score  > 6 were also considered to have pneumonia. The isolation of one or more pathogenic microorganisms in significant bacterial counts was required to confirm the diagnosis of VAP. We considered as nonpathogenic the isolation (at any concentration) of the following microorganisms, unless proven otherwise: viridians-group streptococci; coagulasenegative staphylococcus; Neisseria More Details spp; corynebacterium spp; and candida spp. Sampling of the lower respiratory tract in cases of suspected VAP was performed either by endotracheal aspiration (ETA) and/or telescopic brush sampling of respiratory secretions. For ETA, we obtained undiluted tracheal secretions. When aspiration was unproductive, we irrigated with 5 mL of Ringer lactate solution. Secretions obtained by ETA were trapped in a Lukens specimen container (Sherwood Medical; Tullamore, Ireland).
Quantitative cultures were performed on the screened specimens. For quantitative cultures of tracheal aspirates, the threshold growth for the diagnosis of pneumonia is 10 5 to 10 6 colony-forming units (CFU) per mL (the lower threshold is sometimes used for patients who are on antibiotic therapy when the cultures are performed)
Samples were considered to be positive for VAP when bacterial counts >10 4 cfu/mL for each microorganism were obtained by ETA, and > 10 3 cfu/mL obtained by telescopic brushing. All microorganisms were identified using standard methods, and antimicrobial susceptibility was determined according to Clinical and Laboratory Standards Institute recommendations. The tracheal aspirates were microscopically screened to include only specimens originating from the lower respiratory tract. The presence of macrophages, regardless of the number, indicated that the specimen is from the lower respiratory tract and these specimens were used. In addition, the presence of more than 25 neutrophils per low power field (x 100) was taken as evidence of infection. The presence of more than 25 squamous epithelial cells per low power field X 100 was reason to suspect that the specimen is contaminated with mouth secretions and the specimen was therefore discarded.
The quantitative variables are given as the mean and standard deviation (SD). Continuous variables were compared using the t test for normally distributed variables The Fisher exact test was used to compare nominal variables. The level of significance was set at p < 0.025 for all the tests. The statistical analysis was performed using a statistical software package (SPSS, version 12.0; SPSS Inc; Chicago, IL).
| Results|| |
17 immunocompetent patients who had cardiac surgical procedures were identified. Nine patients had undergone coronary artery bypass grafting for the second time and 5 patients for the first time. These patients were both diabetic and hypertensive. Two patients had mitral valve re replacements. One had Bentall procedure with borderline preoperative renal function. These patients had their procedures under conventional cardiopulmonary bypass. The predominant isolated organisms were staphylococcus aureus, pseudomonas aeruginosa, and other gram-negative aerobic bacilli. There were eleven males and six females; the mean age was 61.18 + 11.7 yr. We observed that the severity of VAP varied with the clinical and hemodynamic stability of the patients. The clinical pulmonary infection score (CPIS) in these patients was higher than 6. The score results plus the endotracheal aspirate non-quantitative culture of the aspirate results were used to make the diagnosis of VAP. Group II that served as a control is a cohort of 12 patients (6 males) with almost similar characteristics of preoperative functional class, demographics, and co-morbid conditions. The only difference was that VAP in their case was managed using the conventional endotracheal tube instead of the Hi Lo Evac tube. The clinical course and outcome of both groups were compared. The need to change the antibiotics and to use different protocols was much less in group I and so was the duration of antibiotic therapy. Mean number of days on the ventilator was 7.5 + 1.9 days for group I and 11.7 + 2.4 days for group II (P< 0.0001). The mean ICU stays for group I is 8.7 + 3.3 days while that of group II is 13.3 + 2.9 days (P= 0.001). In group I, 5 patients could not be weaned and eventually succumbed to the different complications resulting in mortality rate of 29.4%. In group II, 6 patients suffered a similar fate leading to a mortality rate of 50% in the group.
| Discussion|| |
The endotracheal tube plays a role in the pathogenesis of VAP by the elimination of natural defense mechanisms, thereby allowing the entry of bacteria by the aspiration of subglottic secretions or the formation of biofilm on the endotracheal tube. Collection of secretions in the subglottic space in ventilated patients is a predisposing factor for VAP. The usual endotracheal tube allows intermittent aspiration through the lumen of secretions that are beyond the tracheal cuff. The Hi-Lo tube permits the continuous aspiration of secretions in the subglottic space. The definition of pneumonia proposed by the Center for Disease Control (CDC) requires the presence of a new infiltrate on chest roentgenogram. This is in addition to the clinical criteria for pneumonia namely, fever, leukocytosis, purulent sputum. In the ICU setting these findings are the indications to proceed with more evaluation in order to diagnose the problem. Aspiration of pathogenic organisms from the oropharynx is believed to be the predisposing event in most cases of hospital ICU acquired pneumonia. The frequent passage of suction catheters through the endotracheal tubes can introduce these organisms into the airways. Pneumonia accounts for one third of all pulmonary infiltrates in ICU patients. The other possible causes of pulmonary infiltrates in the ICU patients include pulmonary edema, acute respiratory distress syndrome (ARDS) and even atelectasis. ARDS remains the most common non-infectious cause of pulmonary infiltrate in the ICU (7). The usual clinical criteria for pneumonia cannot be used as evidence for diagnosis but are indications to proceed with more evaluation of the pulmonary problem with cultures of specimens obtained from the respiratory tract. The diagnosis of ICU- acquired pneumonia is not an easy one to make. There is no gold standard method for identifying parenchymal lung infections in ICU patients. The protocol that we follow takes many factors in consideration to diagnose VAP. Features suggestive of VAP include the presence of a core temperature exceeding 38.3 C , leukocytosis of more than 10,000 per mm 3 , or leucopenia of less than 4,000 per mm 3 , purulent tracheal secretions, and the presence of a new and/or persistent radiographic infiltrate. However, taken separately these parameters have limited diagnostic value. Pugin and colleagues combined body temperature, white blood cells count, volume, and appearance of tracheal secretions, oxygenation arterial and inspired Oxygen (PaO2/FiO2), chest X-ray, and tracheal aspirate cultures into a clinical pulmonary infection score (CPIS) as a diagnostic tool for pneumonia. It is an algorithm that relies on easily available clinical, radiographic, and microbiological criteria was once hailed as the best guide for both diagnosing and management for VAP (8). Subsequent experience with the scoring system proved that it has to be interpreted in the context of both clinical and laboratory features to be of value. When compared to quantitative cultures of bronchoalveolar lavage fluid, the CPIS has a low sensitivity and specificity for diagnosing VAP with considerable inter-observer variability. The consensus now is that CPIS has low diagnostic accuracy; however, incorporating gram stains results into the score may help clinical decision making in patients with clinically suspected pneumonia (9). Another issue about VAP is the decision whether to start antibiotics and which one to use is often a matter of speculation, as it is unclear under these circumstances if the pneumonia is actually present. Pneumonia is the most common nosocomial infection in the ICU. Over 90% of these pneumonias occur during mechanical ventilation and 50% of VAP occur in the first 4 days after institution of mechanical ventilation (10). The frequently isolated pathogens are staphylococcus aureus, Pseudomonas aeruginosa d other gram negative aerobic bacilli. Aspiration from the oropharynx is the most likely factor in the pathogenesis of VAP. The organisms that colonize the oropharynx in hospitalized patients are mostly enteric-gram bacilli and staphylococcus aureus.
Interventions that have not been shown to be effective include routine changes of the ventilator circuit tubing, chest physiotherapy, and closed suction catheters.
All have class I data to support their nonuse as measures to prevent VAP. Kinetic beds are also not effective in preventing VAP, although class II data support this conclusion. The use of closed suction catheter systems does not decrease the incidence of VAP, but does reduce the cost of care over singleuse catheters and decreases the risk of cross contamination. The diagnostic evaluation of a suspected VAP includes cultures from the respiratory tract through endotracheal or tracheostomy tubes and of pleural fluid if present. Cultures of tracheal aspirates have a high sensitivity > 90% and a low specificity 15 to 40% for diagnosing VAP . Bronchoalveolar lavage (BAL) is performed by wedging the fibreoptic bronchoscope in a distal airway and carryout a lavage using normal saline. The recommended amount for the lavage is at least 120 ml. A total of six lavages using 20 ml of normal saline in each one of them are usually done. Either quantitative or qualitative cultures of the fluid can be done after discarding the first lavage fluid. Quantitative cultures of the tracheal aspirates are preferred over the qualitative ones, as they have higher specificity and are more likely to identify pneumonia and the causative organisms. The Canadian study on diagnosing VAP revealed that the two diagnostic strategies for VAP bronchoalveolar lavage with quantitative culture of the BAL fluid and endotracheal aspiration with non quantitative culture of the aspirate are associated with similar clinical outcomes and similar overall use of antibiotics . In reviewing the data of both groups, distinct advantage for the Hi Lo Evac tube and continuous subglottic suction is evident in both the number of days on the ventilator and the ICU stay. The mortality is also lower in the group that had continuous subglottic suction.
In conclusion, numerous interventions have been tried to prevent the development of VAP Simple steps should not be overlooked, and many are helpful in controlling any type of nosocomial infection. These include a formal infection control program, hand washing between patient contacts, and avoiding unnecessary or prolonged intubation. Specific respiratory interventions include continuous subglottic suctioning, oral intubation, scheduled drainage of condensate from ventilator circuits, and adequate endotracheal cuff pressure. Continuous subglottic suction has an established place in the prevention of VAP. We feel that its use can be extended to established cases of VAP as part of the management strategy for these patients.
Acknowledgement. The author wishes to thank Dr. Tarig Al-khuwaitir, Medical Director, King Saud Medical Complex Riyadh, for his critique of the manuscript. A clinician par excellence whose approach to complex medical problems reflects an unusual depth of knowledge.
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