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The Impact of Hospital-Acquired Bloodstream Infections.

Nosocomial nosocomial /noso·co·mi·al/ (nos?o-ko´me-il) pertaining to or originating in a hospital.

1. Of or relating to a hospital.

 bloodstream blood·stream
The flow of blood through the circulatory system of an organism.


the blood flowing through the circulatory system in the living body.
 infections are a leading cause of death in the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. . If we assume a nosocomial infection Nosocomial infection
An infection that can be acquired in a hospital. ABPA is a nosocomial infection.

Mentioned in: Allergic Bronchopulmonary Aspergillosis, Hospital-Acquired Infections, Pseudomonas Infections

 rate of 5%, of which 10% are bloodstream infections, and an attributable mortality rate of 15%, bloodstream infections would represent the eighth leading cause of death in the United States. Because most risk factors for dying after bacteremia bacteremia: see septicemia.

Presence of bacteria in the blood. Short-term bacteremia follows dental or surgical procedures, especially if local infection or very high-risk surgery releases bacteria from isolated sites.
 or fungemia may not be changeable, prevention efforts must focus on new infection-control technology and techniques.

Vital statistics outlining the major causes of death in a population are an important measure of public health. Ranking disease agents according to according to
1. As stated or indicated by; on the authority of: according to historians.

2. In keeping with: according to instructions.

 the number of deaths they cause can be used for strategic planning Strategic planning is an organization's process of defining its strategy, or direction, and making decisions on allocating its resources to pursue this strategy, including its capital and people.  and public health resource allocation resource allocation Managed care The constellation of activities and decisions which form the basis for prioritizing health care needs . In the United States, vital statistics support efforts to control coronary artery disease coronary artery disease, condition that results when the coronary arteries are narrowed or occluded, most commonly by atherosclerotic deposits of fibrous and fatty tissue. , cancer, cerebrovascular diseases cerebrovascular disease Neurology Any vascular disease affecting cerebral arteries–eg ASHD, diabetic vasculopathy, HTN, which may cause a CVA or TIA with neurologic sequelae–speech, vision, movement of variable duration. , and infections (Table 1) (1). A listing of causes of death, however, provides little insight on how the diseases were acquired or managed or how they might have been prevented. Infections acquired in the hospital are an important cause of death, especially those involving the bloodstream or lung (2).
Table 1. Deaths and death rates in the United States, 1997 (1)

                               No. of            death
                               deaths             rate         % of all
Cause of death             (x [10.sup.3])   (per [10.sup.5])    deaths

Heart disease                  725.8             271.2           31.4
Malignancies                   537.4             200.8           23.2
Cerebrovascular disease        159.9              59.7            6.9
Pneumonia and influenza         88.4              33.0            3.8
Septicemia                      22.6               8.4            0.97

Address for correspondence: Richard P. Wenzel, Department of
Internal Medicine, Medical College of Virginia, Virginia Commonwealth
University, Richmond, Virginia, USA: fax: 804-828-8100; email:

If hospital infection and death occur at high rates, we can examine the process of institutional care: access to infection control personnel, systems for prevention and early recognition, and early and appropriate therapy. With improved care, improved outcome could be anticipated. We explore the impact of hospital-acquired infections Hospital-Acquired Infections Definition

A hospital-acquired infection is usually one that first appears three days after a patient is admitted to a hospital or other health care facility.
, with a focus on bloodstream infections.

Baseline Data

Population-based surveillance studies of nosocomial infections Nosocomial infections
Infections that were not present before the patient came to a hospital, but were acquired by a patient while in the hospital.

Mentioned in: Enterobacterial Infections, Staphylococcal Infections
 in U.S. hospitals indicate a 5% attack rate or incidence of 5 infections per 1,000 patient-days (3-5). With the advent of managed care and incentives for outpatient care, hospitals have a concentrated population of seriously ill A patient is seriously ill when his or her illness is of such severity that there is cause for immediate concern but there is no imminent danger to life. See also very seriously ill.  patients, so rates of nosocomial infections are probably correspondingly higher (6). For many larger institutions, the nosocomial infection rate may be closer to 10%.

If 35 million patients are admitted each year to the approximately 7,000 acute-care institutions in the United States, the number of nosocomial infections--assuming overall attack rates of 2.5%, 5%, or 10%--would be 875,000, 1.75 million, or 3.5 million, respectively. If 10% of all hospital-acquired infections involve the bloodstream, 87,500, 175,000, or 350,000 patients acquire these life-threatening infections each year.

Crude and Attributable Mortality Rates

The overall or crude rate of death does not distinguish the contribution of the patients' underlying diseases from the contribution of bloodstream infections. Recent data from the Surveillance and Control of Pathogens of Epidemiologic Importance [SCOPE] surveillance system of nosocomial bloodstream infections in U.S. hospitals identified a crude mortality rate of 27% (7), with great variation by pathogen Pathogen

Any agent capable of causing disease. The term pathogen is usually restricted to living agents, which include viruses, rickettsia, bacteria, fungi, yeasts, protozoa, helminths, and certain insect larval stages.
 (Figure 1).
Figure 1. Variation in mortality rate by organism causing nosocomial
bloodstream infection (7). The leading four organisms and crude
mortality rate are illustrated.

CNS                   A 32
n=3,908               B 21
S. aureus             A 16
n=1,928               B 25
Enterococcus          A 11
n=1,354               B 32
Candida               A  8
n=934                 B 40

A Proportion

B Crude mortality

Note: Table made from a bar graph.

The direct contribution of nosocomial infection, after the contribution of the underlying illnesses is accounted for, is the attributable mortality rate (8). For example, if a crude mortality rate for nosocomial candidemia of 40% is assumed (as in the SCOPE surveillance system [7]) and three-eighths of the deaths are directly due to the underlying diseases (15% of the 40%), the mortality rate attributable to candidemia would be 25% (40%-15%). Thus, candidemia would contribute five-eighths (25% of the 40%) of the crude mortality rate.

Number of Deaths from Nosocomial Infections

Several assumptions may be examined simultaneously regarding the attack rate and both crude and attributable mortality rate estimates (Figure 2). By doing so, deaths directly attributable to nosocomial bloodstream infections can be calculated, with a range of very conservative to more liberal estimates based on available data. For example, with a hospital infection rate of 5%, of which 10% are bloodstream infections, and an attributable mortality rate of 15%, 26,250 deaths can be directly linked to nosocomial bloodstream infections. However, if a 20% attributable mortality rate is assumed, the number of deaths is from 17,500 (with a 2.5% nosocomial infection rate) to 70,000 (with a 10% total nosocomial infection rate).


With various assumptions about total nosocomial infection rates and attributable mortality rate, the ranking of nosocomial bloodstream infections among leading causes of death can be estimated (Figure 3). This ranking reflects the total number of deaths compared with the reported numbers of leading causes of death in the United States (1). From the above estimates, if nosocomial bloodstream infections alone were counted, they would represent the fourth to thirteenth cause of death in the United States.


The impact of nosocomial bloodstream infections can also be examined in terms of years of life lost. SCOPE (M. Edmond, pers.comm.) indicates that the median age of patients dying of nosocomial bloodstream infections is 57 years. If these patients are 60 years of age, without bloodstream infection they would have lived to age 70. This assumption is reasonable since only attributable deaths are included in the calculations (Figure 4). As an example, if the attributable mortality rate is 20% and the total nosocomial infection rate is 5%, the total number of years of life lost in the United States would be 350,000 annually. If the attributable mortality rate were only 10%, the number of years of life lost annually would be 87,500 to 350,000, depending on the total infection rate.



The arguments above justify a major effort with substantial resources for preventing and controlling serious hospital-acquired infections. We suggest a quality assessment approach for hospital-based programs of infection control: structure, process, and outcome. The Study of the Efficacy of Nosocomial Infection Control (SENIC), published in 1985, showed that both structure (expertise) and process (surveillance, feedback and protocols) predicted lower infection rates (9). A subsequent analysis suggested that infection control

programs represented one of the most cost effective of current public health efforts (10).

Access to improved infection-control technology is one of the promises at the dawn of the 21st century. Another is improved handwashing compliance associated with more attractive and accessible products. Two recent factors influencing infection control are use of antibiotic-bonded vascular catheters and access to alcohol hand-cleansing materials that improve handwashing compliance. In a multicenter study reported by Darouiche and colleagues, bloodstream infections were significantly reduced when patients received catheters bonded with rifampin rifampin (rĭfăm`pĭn), antibiotic used in the treatment of tuberculosis. It is also used to eliminate the meningococcus microorganism from carriers and to treat leprosy, or Hansen's disease.  and minocycline (11). Estimates of nosocomial bloodstream infections from the SCOPE database indicate that 70% occur in patients with central venous catheters central venous catheter
A catheter passed through a peripheral vein and ending in the thoracic vena cava; it is used to measure venous pressure or to infuse concentrated solutions.
 (12). Furthermore, the study by Darouiche et al. showed that 90% of central venous venous /ve·nous/ (ve´nus) pertaining to the veins.

Of, relating to, or contained in the veins.


pertaining to the veins.
 catheter-associated infections could be prevented by antibiotic-bonded catheters. Assuming 200,000 total nosocomial bloodstream infections of which 35% are attributable to central venous catheters and assuming that 45% could be prevented with a catheter bonded with minocycline and rifampin, the number of lives saved according to varying attributable mortality rate estimates would be 4,745 to 9,450 (Table 2).
Table 2. Central venous catheter technology and nosocomial
bloodstream infections and deaths

               CVC(a)-related     No. of deaths
Attributable    deaths from      remaining if new
mortality       bloodstream      catheters prevent     No. of
rate (%)        infections(b)      45% of deaths     lives saved

15                 10,500              5,755            4,745
20                 14,000              7,700            6,300
25                 17,500              9,625            7,875
30                 21,000             11,550            9,450

(a) CVC = Central venous catheter.

(b) Assumptions in this analysis: 200,000 bloodstream infections/
year, 35% attributed to CVCs, 45% prevented with antibiotic-bonded
catheters. Previous studies showed 175,000-350,000 nosocomial
bloodstream infections/year, 70% of which were related to central
venous catheters; 90% of central venous catheter-related bloodstream
infections prevented with antibiotic bonded catheters (11).

In a study of handwashing compliance by Bishoff and colleagues, handwashing frequency in a medical intensive-care unit (ICU ICU intensive care unit.

intensive care unit


see intensive care unit.

) increased with access to an alcohol-based product (13). Previously, Doebbeling and colleagues showed that medicated medicated /med·i·cat·ed/ (med´i-kat?id) imbued with a medicinal substance.


contains a medicinal substance.
 soap solutions were more popular than alcohol preparations and thus were associated with reduced infection in intensive care units (14). The study by Doebbeling et al. showed that a 28% increase in handwashing frequency (with a higher volume of use of antiseptic antiseptic, agent that kills or inhibits the growth of microorganisms on the external surfaces of the body. Antiseptics should generally be distinguished from drugs such as antibiotics that destroy microorganisms internally, and from disinfectants, which destroy  soap) resulted in a substantial reduction in the rate of nosocomial bloodstream infections of 56/10,000 ICU admissions, by 45% for the attack rate and by 22% when incidence density was calculated (Table 3). In SCOPE, 49.4% of all nosocomial bloodstream infections occurred in intensive-care units. However, if 25%-50% of all bloodstream infections occur in intensive-care units and a 25% increase in handwashing would prevent 25% of bloodstream infections in ICUs, the number of lives sawed would be 469 to 1,874, depending on assumptions of attributable death rate (Table 3). The emerging concept is that increased handwashing frequency will result in an improved outcome. Perhaps most striking is that in this selected comparison of the impact of changes in technology with changes in behavior, the former will likely be 5 to l0 times more effective, but at substantially increased cost. Neither, however, is mutually exclusive Adj. 1. mutually exclusive - unable to be both true at the same time

incompatible - not compatible; "incompatible personalities"; "incompatible colors"
, and both need to be in place.
Table 3. Handwashing and nosocomial bloodstream infections and deaths

                                No. of lives      No. of lives
Attributable                    saves if 25%      saved if 50%
mortality       Expected       of BSI(a) occur    of BSI occur
rate (%)         deaths          in ICUs(b)          in ICUs

15                1,875              469                938
20                2,500              625              1,250
25                3,125              781              1,562
30                3,750              937              1,874

(a) BSI = Bloodstream infections; ICU = Intensive-care unit.

(b) Assumptions in this analysis: 50,000 (25%) or 100,000 (50%) of
BSI occur in ICUs, and a 25% increase in handwashing prevented 25%
of BSIs. Known (14): In ICUs, a 28% increase in handwashing was
related to a reduction of risk of BSI of 56/10,000 ICU admissions,
a reduced attack rate of 45%, and a reduced incidence density
rate of 22%.

In summary, vital statistics list the major causes of death yet give little insight into environmental risk factors for disease or outcomes. Estimates of hospital-acquired bloodstream infections derived from the attributable mortality rate show the impact of the specific environment where many life-threatening infections occur. By modifying the institutional environment to improve hospital care and infection control, the outcomes for patients will greatly improve. Technological advances will likely have a greater impact on health than theoretical advances in behavior, such as improved handwashing frequency.


(1.) National Center for Health Statistics National Center for Health Statistics (NCHS) is part of the Centers for Disease Control and Prevention (CDC), which is part of the United States Department of Health and Human Services.

NCHS is the United States' principal health statistics agency.
. Vital statistics of the United States. U.S. Census Bureau Noun 1. Census Bureau - the bureau of the Commerce Department responsible for taking the census; provides demographic information and analyses about the population of the United States
Bureau of the Census
. Statistical abstract of the United States The Statistical Abstract of the United States is a publication of the United States Census Bureau, an agency of the United States Department of Commerce. Published annually since 1878, the statistics describe social and economic conditions in the United States. : 1999 Washington D.C. (119th edition), p.99.

(2.) Wenzel RP. The mortality of hospital-acquired bloodstream infections: need for a new vital statistic? Int J Epidemiol 1988;17:225-7.

(3.) Broderick A, Mori M, Nettleman MD, Streed SA, Wenzel RP. Nosocomial infections: validation of surveillance and computer modeling to identify patients at risk. Am J Epidemiol 1990;131:734-42.

(4.) Morrison AJ Jr, Kaiser DL, Wenzel RP. A measurement of the efficacy of nosocomial infection control using the 95 percent confidence interval confidence interval,
n a statistical device used to determine the range within which an acceptable datum would fall. Confidence intervals are usually expressed in percentages, typically 95% or 99%.
 for infection rates. Am J Epidemiol 1987;126:292-7.

(5.) Wenzel RP, Osterman CA, Townsend TR, Veazey JM Jr, Servis KH, Miller LS, et al. Development of a statewide program for surveillance and reporting of hospital-acquired infections. J Infect infect /in·fect/ (in-fekt´)
1. to invade and produce infection in.

2. to transmit a pathogen or disease to.

 Dis 1979;140:741-6.

(6.) Pittet D, Wenzel RP. Nosocomial bloodstream infection: secular trends secular trend

The relatively consistent movement of a variable over a long period. A stock in a secular uptrend is an indicator that the security has experienced an extended period of rising prices.
 in rates and mortality in a tertiary health care tertiary health care (ter´shēer´ē),
n a specialized, highly technical level of health care that includes diagnosis and treatment of disease and disability in sophisticated large research and teaching
 center. Arch Intern intern /in·tern/ (in´tern) a medical graduate serving in a hospital preparatory to being licensed to practice medicine.

in·tern or in·terne
 Med 1995;155:1177-84.

(7.) Edmond MB, Wallace SE, McClish DK, Pfaller MA, Jones RN, Wenzel RP. Nosocomial bloodstream infections in United States hospitals: a three-year analysis. Clin Infect Dis 1999;29:239-44.

(8.) Wenzel RP. Attributable mortality: the promise of better antimicrobial antimicrobial /an·ti·mi·cro·bi·al/ (-mi-kro´be-al)
1. killing microorganisms or suppressing their multiplication or growth.

2. an agent with such effects.
 therapy. J Infect Dis 1998;178:917-9.

(9.) Haley RW, Culver cul·ver  
A dove or pigeon.

[Middle English, from Old English culufre, from Vulgar Latin *columbra, from Latin columbula, diminutive of columba, dove.]
 DH, White ,JW, Morgan WM, Emori TG, Munn VP, et al. The efficacy of infection surveillance and control programs in preventing nosocomial infections in US hospitals. Am J Epidemiol 1985;121:182-205.

(10.) Wenzel RP. The economics of nosocomial infection. J Hosp Infect 1995;31:79-87.

(11.) Darouiche RO, Raad II, Heard SO, Thornby JI, Wenker OC, Gabrielli A, et al. A comparison of two antimicrobial-impregnated central venous catheters. N Engl J Med 1999;340:1-8.

(12.) Wenzel RP, Edmond MB. The evolving technology of venous access Venous Access Definition

Venous access introduces a needle into a vein, usually for the purpose of withdrawing blood or administering medication.
. N Engl J Med 1999;340:48-9.

(13.) Bischoff WE, Reynolds TM, Sessler CN, Edmond MB, Wenzel RP. Handwashing compliance by health care workers: the impact of introducing an accessible, alcohol-based hand disinfectant disinfectant, agent that destroys disease-causing microorganisms and their spores. Disinfectants, or germicides, are sometimes considered to be substances applied to inanimate bodies, whereas antiseptics, not so potent, are agents that kill microbes on living things. . Arch Intern Med 2000;160:1017-21.

(14.) Doebbeling BN, Stanley GL, Sheetz CT, Pfaller MA, Houston AK, Annis L, et al. Comparative efficacy of alternative handwashing agents in reducing nosocomial infections in intensive care units. N Engl J Med 1992;327:88-9;].

Dr. Wenzel is professor and chair of the department of internal medicine, Medical College of Virginia History
The school was founded in 1838 as the Medical Department of Hampden-Sydney College. It received an independent charter from the General Assembly in 1854 and became the Medical College of Virginia, and shortly thereafter transferred all its property to the Commonwealth
, Virginia Commonwealth University Formed by a merger between the Richmond Professional Institute and the Medical College of Virginia in 1968, VCU has a medical school that is home to the nation's oldest organ transplant program. , Richmond, VA.

Dr. Edmond is associate professor and associate chair for education in the department of internal medicine, Medical College of Virginia, Virginia Commonwealth University. He is also hospital epidemiologist at the Medical College of Virginia Hospital.
COPYRIGHT 2001 U.S. National Center for Infectious Diseases
No portion of this article can be reproduced without the express written permission from the copyright holder.
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Author:Edmond, Michael B.
Publication:Emerging Infectious Diseases
Article Type:Statistical Data Included
Geographic Code:1USA
Date:Mar 1, 2001
Previous Article:Infection Control and Changing Health-Care Delivery Systems.
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