ADVERTISEMENT
Preparedness of the Cardiac Catheterization Laboratory for Severe Acute Respiratory Syndrome (SARS) and Other Epidemics
March 2005
Severe acute respiratory syndrome (SARS) is an emergent global threat caused by a novel coronavirus (SARS-CoV),1–3 which had caused outbreaks worldwide in 2003 with substantial morbidity and mortality,4–8 affecting over 8,000 patients and leading to 774 deaths.9 Meticulous infection control is required to avoid nosocomial spread of infection. Published infection control guidelines by the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC), however, have not specifically addressed infection control issues in cardiac catheterization laboratories (CCL),10,11 in which positive pressure ventilation is the norm. Two out of 90 SARS patients managed in our institution in the 2003 outbreak had cardiac catheterization performed in the course of their illness. We report the planning, implementation, and outcome of infection control measures against SARS cross-infection in the CCL setting.
Methods
Three levels of infection control measures as recommended for other infectious disease: personal protection, environmental controls, and administrative controls,12 were implemented in the CCL for the two invasive cardiac procedures.
Personal protection equipment (PPE). The application of PPE was aimed at protecting health care workers (HCW) from inhaling or contacting infective droplets. All CCL personnel practiced meticulous hand hygiene and wore full protective attire as required for standard airborne, droplet, and contact precautions: N-95 or N-100 respirators, protective eyewear, full face shields, disposable caps, gowns, surgical gloves, and shoe covers. As advanced barrier, hooded HEPA (high-efficient particulate air) powered air purifying respirators (PAPR), Air-Mate™ (3M, Minnesota; Figure 1), were worn by the operators to prepare for high-risk, aerosol-generating procedures, such as airway suctioning, endotracheal intubation, or resuscitation.
Environmental/engineering control measures. Environmental and engineering controls were aimed at reducing the viral load in the air through reduction in droplets spreading to the environment and optimization of ventilation and direction of airflow.
1. Measures to reduce droplet spread. All patients were required to wear surgical masks, caps, and gowns. Blood splashing during arterial puncture was minimized by performing the puncture under a transparent plastic sheet. Since airway management during resuscitation poses high risk for droplets spreading and disease transmission,11 resuscitation instruments, including bag-valve resuscitators and mechanical ventilators, were equipped with high-efficiency bacterial/viral filters in the exhalation circuit. Two filters were used for each ventilator: one at the exhalation outlet, and another between the expiratory tubing and the ventilator. Closed-system suction for mechanical ventilators was a standard routine in our department. To facilitate subsequent cleaning and disinfection, non-essential CCL equipment and fittings were either removed from the procedure room, or covered with large plastic sheets before the procedures. A semi-urgent case, such as our second case mentioned below, was scheduled as the last case of the day. After each procedure, all operators took showers after degowning. All soiled and exposed surfaces were thoroughly cleaned with 1,000 ppm hypochorite solution. The CCL was then closed down overnight to allow residual contaminated droplets to be removed by the ventilation system. Thorough cleaning and disinfection was repeated the next day before the CCL was opened to non-SARS cases.
2. Modification of ventilation design. The standard positive pressure ventilation system of the CCL consists of an air-handling unit (AHU) that distributes conditioned air to different functional units, including the procedure room and control room. Most of the air is recirculated to the AHU through return air grilles located at the corridor outside the procedure room. The remaining portion is extracted to the atmosphere by an independent exhaust system through exhaust grilles located at the toilets, sluices room, dark room, and so on.
2.1 Temporary modification of the ventilation system for the first patient. The first case was performed as an emergency procedure using the existing ventilation system with modifications made to airflow. To eliminate air recirculation and positive pressure in the procedure room, the AHU was stopped. Ventilation exhaust fans were installed at the side of the procedure room close to the sluice room and toilets to create airflow from the corridor to the usual independent exhaust system. This generated a slightly negative pressure ventilation system in the procedure room, and a near-unidirectional airflow pattern, which was confirmed by smoke trail test according to published guidelines.132.2. Temporary modification of the ventilation system for the second patient. Operation of the AHU was continued to supply conditioned air at approximately ten air changes per hour (ACH), but the recirculating air duct and return air grilles were sealed to prevent cross-contamination to other functional units. Negative pressure ventilation at approximately 13 ACH was achieved in the procedure room by the existing independent exhaust system, supplemented by a temporary mobile local exhaust system with HEPA filters. This ensured directional airflow from the clean to the less clean area.
Administrative control measures. Infection control policies in the hospital were promulgated, including the levels of PPE required in hospital areas with different levels of risk. Training was provided to all HCW, including CCL personnel, in infection control measures, including the correct use of PPE. A designated hospital infection control enforcement team patrolled different hospital areas to reinforce appropriate PPE use by all staff. All personnel, including those from the CCL, were instructed to report fever and respiratory symptoms and refrain from returning to work should those symptoms develop within ten days of exposure to SARS patients.11 A SARS intensive care unit was set up, which also accommodated SARS patients requiring coronary care, to reduce the size of infected hospital areas and the number of nursing staff exposed. Visitors to the hospital were not allowed in order to minimize the risk of spreading the SARS virus to the community. Our respiratory and critical care physicians developed a standardized treatment protocol to manage the condition.14 The protocol was designed to provide effective and timely treatment to reduce the risk of respiratory deterioration, which in turn would reduce hemodynamic instability and the risk of unstable cardiac status.
Results
Patient characteristics. Details of the two SARS patients who required cardiac catheterization are reported elsewhere.15,16 In brief, the first patient developed recurrent acute coronary syndrome in the second week of SARS. Urgent coronary angiography showed triple-vessel disease, and percutaneous intervention was performed. The second patient underwent diagnostic coronary angiography for recurrent chest pain associated with electrocardiographic changes of new onset precordial T-wave inversion. Coronary arteries were normal, and her symptoms were attributed to pneumomediastinum, subsequently diagnosed on high-resolution, computerized tomography of the thorax.
Issues arising from the use of PPE during cardiac catheterization. Fogging up of protective eyewear, especially airtight goggles, was a problem that could be minimized by the use of tight-fitting respirators which avoided air leaking at the nasal ridge, and prior application of anti-fog solution or warming the goggles to body temperature prior to application. Vision was unimpeded with the use of Air-mate,™ but some difficulty in communication resulted from reduced transmission of voice, and background noise from the powered air purifier.
Staff outcome. Three cardiologists, four nurses, and one laboratory assistant participated in the coronary intervention for the first patient who had acute myocardial infarction and unstable hemodynamics. Coronary angiography for the second patient involved another two cardiologists, and three nurses, as well as one laboratory assistant from the same team that treated the first patient. Thus a total of ten HCW attended the two procedures: five cardiologists, four nurses, and one laboratory assistant. Another eight HCW participated in the cleaning process. With the infection control measures implemented, none contracted the illness. Four of the ten directly involved HCW were recruited for a SARS-CoV serology surveillance program in our department, and all had negative serology.
Discussion
WHO and CDC have issued infection control guidelines for the management of SARS patients.10,11 They do not, however, cover all hospital areas. It is important for clinicians to be constantly vigilant in their daily practices, especially outside the usual ward environment. Recent reports have addressed this issue in radiology departments and operating rooms,17–20 but there are no such reports on infection control practices in the CCL.
The transmission of SARS occurs predominantly through direct contact of mucous membrane (eyes, nose or mouth) with infectious respiratory droplets or fomites.21,22 A recent study on a large community outbreak also revealed evidence of airborne transmission.23 The WHO and CDC recommend care of SARS patients using strict precautions for airborne, droplet, and contact transmission.10,11 This should be strictly adhered to in the CCL. Unlike other blood-borne viral infections such as hepatitis B and C, the risk of transmitting SARS from a blood-splashing procedure like cardiac catheterization is not defined, though low-concentration viremia has been reported to be detected up to about ten days after symptom onset in SARS patients.2,24
SARS affects both the young and old alike,1,4–8 with older patients being at risk of developing acute cardiac events in the presence of hypoxemia and stress from acute respiratory illness. In our series of 90 patients,25 13% were older than 65 years of age, and 3.3% had known coronary artery disease. One or more risk factors, including smoking, diabetes mellitus, and hypertension, were present in 20% of all patients. Acute myocardial infarction accounted for two of the four deaths among the SARS patients treated in our institution, and two of five deaths among 75 patients in another series.8 Thus cardiologists and CLL personnel must be prepared to manage SARS patients who may be complicated by acute cardiac catastrophes.
Recommended standard personal infection control measures to manage SARS include meticulous hand hygiene, N 95/99/100 or equivalent respirators, eye protection, gowns, and gloves.10,11 Advanced protection in the form of PAPR is optional and may be advisable in aerosol-generating procedures11 that carry a high risk of SARS transmission and may have been linked to hospital outbreaks.7,11,21,22 Use of bacterial/viral filters on the exhaust end of ventilation equipment, as well as closed-system suction, are recommended to minimize the risk of spreading contaminant aerosols to the environment.11,26–28
Under normal circumstances, CCL procedure rooms are designed to have positive pressure ventilation to avoid potential contamination from adjacent areas. In the management of SARS patients, high air-change (> 12 ACH), achieved through negative pressure ventilation, is recommended to minimize environmental contamination by infected droplets.10,11,29 We have demonstrated in our two cases the feasibility and safety of a temporary negative pressure system in our CCL.
Longer-term modification of the ventilation system in the CCL, to manage SARS or other infectious patients, should aim at preventing the spread of infection droplet nuclei using measures similar to existing guidelines for other infectious diseases.30 By installing an additional exhaust system in the procedure room to achieve an extraction rate of 12 ACH or more,29 airflow could be directed from the positive pressure control room to the procedure room. The pattern of air balancing between each functional CCL unit can be altered to suit different operational scenarios. During normal operation for non-SARS patients, normal positive pressure ventilation in the procedure room can be resumed by switching off the additional exhaust system. By installing adjustable airflow pattern grilles at ceiling level and an extraction system at floor level, air can be controlled so that it flows from the ceiling level downward to the operation table, and removed at low level. HEPA filters can be incorporated into the air supply and exhaust systems.
Meticulous cleansing and disinfection of the CCL after catheterization procedures for SARS patients are important components of infection control. Since contaminated surfaces can be a source of disease transmission, staff members responsible for cleansing should wear full PPE.11,22 SARS-CoV can survive outside the human body for days.21 Where operation permits, the CCL can be cleaned and then temporarily closed after a procedure involving SARS patients to allow time for the viral load to decrease before a second thorough cleansing and disinfection.
For the above infection control measures to be effective, corresponding administrative measures must be implemented in parallel. A hospital infection control plan should be in place, which includes policies on isolation of suspected and confirmed cases, restriction of visitors, and provision of a continuous supply of PPE. Training of HCW in the importance of infection control and the appropriate use of the PPE provided is essential, as infection control measures are effective only if they are fully understood.
The number of HCW exposed to SARS patients should be limited as much as possible.10,11 It was the policy in our institution that a dedicated SARS team managed the SARS patients at one time. Yet, for invasive procedures, it is also important to have adequate manpower to ensure the procedures run smoothly. We had to prepare for intra-procedural events, such as the need for resuscitation in our first patient who suffered from acute myocardial infarction and was hemodynamically unstable. We also prepared for other unexpected events, such as an operator’s impeded vision due to fogged up eyewear. As such, the number of HCW involved can be tailored according to the patient profile. For more complicated cases, such as our first patient, a larger team is needed. It would be desirable to have the same team of HCW participating in other similar procedures. Our two cases involved the same team of nurses and laboratory assistant, though for department operational reasons, two different groups of cardiologists took part in the two procedures. All of the operators in the two cases were experienced cardiologists. This ensured smoothly-run procedures, particularly when communication was hampered by the use of PPE.
Conclusions
SARS emerged as a global threat. The major worldwide outbreak in early 2003 and the subsequent re-emergence of cases31–34 should alert clinicians to prepare for possible new waves of infection. SARS patients may develop acute cardiac events necessitating cardiac catheterization. There is a need for hospital administrators, cardiologists, and other CCL personnel to reexamine their CCL set-up and to develop a contingency plan to achieve stringent infection control, and to revamp the ventilation system so as to meet the challenges of SARS, or other future epidemics.
1. Peiris JSM, Lai ST, Poon LLM, et al. Coronavirus as a possible cause of severe acute respiratory syndrome. Lancet 2003;361:1319–1325.
2. Drosten C, Gunther S, Preiser W, et al. Identification of a novel coronavirus in patients with severe acute respiratory syndrome. N Engl J Med 2003;348:1967–1976.
3. Ksiazek TG, Erdman D, Goldsmith CS, et al. A novel coronavirus associated with severe acute respiratory syndrome. N Engl J Med 2003;348:1953–1966.
4. Tsang KW, Ho PL, Ooi GC, et al. A cluster of cases of severe acute respiratory syndrome in Hong Kong. N Engl J Med 2003;348:1977–1985.
5. Poutanen SM, Low DE, Henry B, et al. Identification of severe acute respiratory syndrome in Canada. N Engl J Med 2003;348:1995–2005.
6. Booth CM, Matukas LM, Tomlinson GA, et al. Clinical features and short-term outcomes of 144 patients with SARS in the greater Toronto area. JAMA 2003;289:2801–2809.
7. Lee N, Hui D, Wu A, et al. A major outbreak of severe acute respiratory syndrome in Hong Kong. N Engl J Med 2003;348:1986–1994.
8. Peiris JSM, Chu CM, Cheng VCC, et al. Clinical progression and viral load in a community outbreak of coronavirus-associated SARS pneumonia: A prospective study. Lancet 2003;361:1767–1772.
9. WHO. Summary of probable SARS cases with onset of illness from 1 November 2002 to 31 July 2003. http://www.who.int/csr/sars/country/table2003_09_23/en/ (accessed Jan 12, 2004).
10. WHO. Hospital infection control guidance for severe acute respiratory syndrome (SARS), April 24,2003. http://www.who.int/csr/sars/infectioncontrol/en/ (accessed June 20, 2003).
11. CDC. Public health guidance for community-level preparedness and response to severe acute respiratory syndrome (SARS) version 2. Supplement I: Infection control in healthcare, home, and community settings. http://www.cdc.gov/ncidod/sars/guidance/i/ pdf/i.pdf (accessed Jan 14, 2004).
12. WHO. Guidelines for the prevention of tuberculosis in health care facilities in resource-limited settings. http://www.who.int/gtb/publications/healthcare/ PDF/WHO99-269.pdf (accessed June 20, 2003).
13. ASHRAE 1994. American Society of Heating, Refrigerating and Air-conditioning Engineers, Inc. IAQ94 Conference — Engineering Indoor Environment, 1994. pp.222
14. So LKY, Lau ACW, Yam LYC, et al. Development of a standard treatment protocol for severe acute respiratory syndrome. Lancet 2003;361:1615–1617.
15. Tsui KL, Leung TC, Yam LYC, et al. Coronary plague instability in severe acute respiratory syndrome. Int J Cardiol (in press).
16. Tse TS, Tsui KL, Yam LYC, et al. Occult pneumomediastinum in a SARS patient presenting as recurrent chest pain and acute ECG changes mimicking acute coronary syndrome. Respirology 2004;9:271–273.
17. King AD, Ching ASC, Chan PL, et al. Severe acute respiratory syndrome: Avoiding the spread of infection in a radiology department. Am J Roentenol 2003;181:25–27.
18. Ho SSY, Chan PL, Wong PK, et al. Eye of the storm: The roles of a radiology department in the outbreak of severe acute respiratory syndrome. Am J Roentgenol 2003;181:19–24.
19. Lau TN, Teo N, Tay KH, et al. Is your interventional radiology service ready for SARS?: The Singapore experience. Cardiovasc Intervent Radiol 2003;26:421–427.
20. Peng PW, Wong DT, Bevan D, Gardam M. Infection control and anesthesia: Lessons learned from the Toronto SARS outbreak. Can J Anaesth 2003;50:989–997.
21. Peiris JSM, Yuen KY, Osterhaus ADM, Stohr K. The severe acute respiratory syndrome. N Engl J Med 2003;349:2431–2441.
22. WHO. Consensus document on the epidemiology of severe acute respiratory syndrome (SARS). http://www.who.int/csr/sars/en/WHOconsensus.pdf (accessed January 5, 2004).
23. Yu ITS, Li Y, Wong TW, et al. Evidence of airborne transmission of the severe acute respiratory syndrome virus. N Engl J Med 2004;350:1731–1739.
24. WHO. Recommendations on SARS and blood safety May 15, 2003. http://www.who.int/csr/sars/guidelines/bloodsafety/en/ (accessed June 20, 2003).
25. Lau ACW, So LKY, Miu FPL, et al. Outcome of coronavirus-associated severe acute respiratory syndrome using a standard treatment protocol. Respirology 2004;9:173–183.
26. Li TST, Buckley TA, Yap FHY, Sung JJY, Joynt GM. Severe acute respiratory syndrome (SARS): Infection control. Lancet 2003;361:1386.
27. Lapinsky SE, Hawryluck L. ICU management of severe acute respiratory syndrome. Intensive Care Med 2003;29:870–875.
28. Yam LYC, Chen RC, Zhong NS. SARS: Ventilatory and intensive care. Respirology 2003;8:S31–S35.
29. CDC. Guideline for preventing the transmission of Mycobacterium tuberculosis in health care facilities, 1994. MMWR 1994;43 (No RR-13).
30. CDC. Guideline for preventing the transmission of tuberculosis in health-care settings, with special focus on HIV-related issues, 1990. MMWR 1990;39 (No. RR-17).
31. WHO. Severe acute respiratory syndrome (SARS) in Singapore – update 2, September 24, 2003. http://www.who.int/csr/don/2003_09_24/en/ (accessed April 11, 2004).
32. WHO. Severe acute respiratory syndrome (SARS) in Taiwan, China, December 17, 2003. http://www.who.int/csr/don/2003_12_17/en/ (accessed April 11, 2004).
33. WHO. New case of laboratory-confirmed SARS in Guangdong, China - update 5, January 31, 2004. http://www.who.int/csr/don/2004_01_31/en/ (accessed April 11, 2004).
34. WHO. China confirms SARS infection in another previously reported case; summary of cases to date – Update 5, April 30, 2004. http://www.who.int/csr/don/ 2004_04_30/en/ (accessed May 5, 2004).
