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Preventing Perioperative Transmission of Infection: A Survey of Anesthesiology Practice

Tait, Alan R. PhD; Tuttle, Dale B. MBA

General Article

Given the societal and economic impact of perioperative infection, it is essential that anesthesiologists and other operating room personnel use appropriate precautions to reduce the potential for transmission of infectious agents to the patients under their care.This study, therefore, was designed to evaluate the degree to which anesthesiologists utilize appropriate hygienic techniques for the prevention of infection in the perioperative period. A total of 1149 questionnaires were mailed to anesthesiologists randomly selected from the membership of the American Society of Anesthesiologists (ASA). Of these, 493 (44%) were completed and returned. Forty-nine percent and 75.3% of respondents always used gloves and masks, respectively, in their everyday practice. Only 58% of respondents stated that they always washed their hands after every patient contact and 85% reported that they always used aseptic technique for placing indwelling catheters. Knowledge of universal precautions for prevention of occupational transmission of infection was associated with good hygienic practice. Twenty percent of the respondents reported frequently or always reusing syringes for more than one patient and 34.4% reported never or rarely disinfecting the septum of multidose vials prior to use. The practice of reusing syringes was significantly greater among private than university practioners (P < 0.01). On a scale of 0-10 (10 = high) anesthesiologists rated their potential for transmitting or contributing to patient infection as 4.7 +/- 0.12 (mean +/- SE). Results of this study suggest that, whereas most responding anesthesiologists exhibit appropriate infection control behaviors, there are several potentially hazardous practices that continue.

(Anesth Analg 1995;80:764-9)

Department of Anesthesiology, The University of Michigan Medical Center, Ann Arbor, Michigan (Tait), and the Department of Management, Michigan State University, East Lansing, Michigan (Tuttle).

Accepted for publication October 26, 1994.

Address correspondence and reprint requests to Alan R. Tait, PhD, Department of Anesthesiology, University of Michigan Medical Center, 1500 E. Medical Center Drive, Ann Arbor, MI 48109.

The appearance of an infectious diathesis after anesthesia and surgery is a major source of morbidity and mortality and thus is an important indicator of the quality of health care in the perioperative period. It has been estimated that 6% of hospitalized patients in the United States contract nosocomial infections annually, at a cost of approximately 5-10 billion dollars [1,2]. Patients receiving immunosuppressive drugs, allografts, or those with immunosuppressive diseases such as cancer or human immunodeficiency syndrome are particularly vulnerable to postoperative infections. Indeed, despite the advances in modern antibiotic prophylaxis and technology, one of the leading causes of morbidity and mortality in these patients is infection [3-5]. Successful control of these infections requires application of appropriate hygienic techniques and a thorough understanding of the modes of transmission. Although a cause-effect relationship between anesthetic practice and the appearance of postoperative infection is difficult to establish, the fact that anesthesiologists are often involved with techniques that violate the patient's protective barriers makes a strong argument for close attention to hygienic practice. This study was designed, therefore, to examine the degree to which anesthesiologists utilize good hygienic practices for the prevention of transmission of infectious agents to the patient.

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This study was approved by the University of Michigan's Institutional Review Board for research involving human subjects. A random sample representing approximately 4% of practicing anesthesiologists from around the United States was obtained from the membership directory of the American Society of Anesthesiologists (ASA). Subjects were selected from the directory by systematic sampling using a random start. Nonpracticing anesthesiologists, or those not directly involved with administering anesthesia were excluded from study.

Data were collected using a questionnaire designed to address two issues concerning the bidirectional transmission of infectious agents between the patient and anesthesiologist. Part one addressed issues regarding anesthesiologists' compliance with the Centers for Disease Control (CDC) guidelines for the prevention of occupational transmission of human immunodeficiency virus (HIV) and hepatitis B virus (HBV) and is the subject of another article [6]. The second issue, presented here, focused on anesthesiologists' adherence to recommended practices for the prevention of transmission of infection to the patient. Questionnaire development occurred in three stages. First a prototype questionnaire was developed and reviewed by 10 of our departmental clinical faculty members. This initial review was designed to determine the quality and appropriateness of the questions, to point out any ambiguities, and to suggest any relevant content areas that may have been over-looked. Based on this initial review, a pretest of the questionnaire was administered to 70 anesthesiologists randomly selected from four different anesthesia departments within the Detroit area. This pretest served to further determine the reliability of the questions and to determine an anticipated response rate. Based on the input from these initial tests, the final draft of the questionnaire was prepared, reviewed one last time by departmental faculty, and sent out to the population described herein. A copy of the part of the questionnaire pertinent to this study is included as an Table 5 (Appendix 1).

Table 5

Table 5

All questions were designed to be completed anonymously to reduce the potential for self-report bias. A postcard returned separately from the questionnaire confirmed participation in the survey. A second mailing was sent to those who did not respond to the initial one. Subsequently, a short questionnaire was mailed to a sample of 100 nonrespondents in an attempt to identify their demographic and attitudinal characteristics.

Categorical variables were analyzed by frequency distribution and chi squared analysis. Measures of association were computed using Pearson's product moment correlation coefficients. A P value of < 0.05 was considered statistically significant.

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A total of 1149 questionnaires were mailed, of which 17 were returned undelivered. Completed questionnaires were received from 493 anesthesiologists, indicating a response rate of 44%. Seventy-nine percent of the respondents were male, 94.2% were MD anesthesiologists, and 61.5% were in private practice. These data compare favorably with the demographics of the ASA as a whole and a sample of the nonrespondents. This suggests that our sample was representative of the ASA membership and that the nonrespondents were similar demographically. The principal reason given by the anesthesiologists who did not respond was that they were either too busy (41%) or had lost the questionnaire (33.3%). Indications that the nonrespondents were different attitudinally or behaviorly from the respondents were not evident from the small sample of polled nonrespondents.

Routine use of gloves, masks, and gowns is described in Table 1. There was no difference in the use of these items between practice types or years in practice. Questions related to the frequency of handwashing showed that the majority of respondents reported that they always washed their hands after exposure to patients who were at high risk for HIV or HBV (93.4%), HIV seropositive patients (95.2%), or after exposure to patients' body fluids (97.5%). However, only 58% admitted to always washing their hands after contact with low-risk patients. Fifty percent of respondents indicated that they always washed their hands even if they had been wearing gloves. With respect to anesthesia equipment, 88.4% of respondents indicated that they changed the disposable breathing circuit after every patient. Four percent indicated that they only changed the circuit after a high-risk patient, and 3.2% only at the end of the day. Ninety-nine percent of anesthesiologists indicated that they or a technician cleaned or disinfected their laryngoscopes after each patient use. Table 2 demonstrates the principal modes of cleaning. Sixty-four percent of the respondents indicated that disinfection was the most commonly used method of cleaning laryngoscope blades. Other cleaning techniques included combinations of soap and water, disinfectant and/or autoclaving. Table 3 summarizes some of the commonly used anesthetic practices that have been implicated in perioperative transmission of infection. Measures of association between years in practice, knowledge of universal precautions for prevention of occupational transmission of infection, and behaviors were computed using a Pearson product moment correlation. Anesthesiologists who reported having read the CDC universal precaution guidelines for the prevention of occupational transmission of HIV and HBV were more likely to have good hygienic practices. These results are presented in Table 4.

Table 1

Table 1

Table 2

Table 2

Table 3

Table 3

Table 4

Table 4

An index of patient care was created composed of factors related to the frequencies of cleaning laryngoscope blades, anesthetic machine surfaces, changing breathing circuits, use of aseptic technique, disinfecting multidose vial septums, and reuse of syringes. Using a hierarchal regression analysis which controlled for years in practice and practice type, anesthesiologists who had read the CDC guidelines for prevention of occupational transmission of infection were shown to have a significant (P < 0.01) increase in recommended patient care behaviors.

Practice type was associated with certain behaviors. Twenty-eight percent of anesthesiologists in private practice reported frequently or always reusing syringes for more than one patient compared with 7.3% in university practice (P < 0.01). In addition, private practioners were more likely to change the breathing circuit after each patient than those in university practice (94% vs 77.5%; P < 0.01).

Ninety-six percent of anesthesiologists surveyed admitted giving anesthesia while harboring a respiratory tract infection, 60.1% with a gastrointestinal infection, 22% with herpes simplex exacerbations, and 15.4% with psoriasis or dermatitis. On a scale of 0-10 (10 = high) anesthesiologists perceived their role of transmitting infection to the patient as 4.7 +/- 0.12 (mean +/- SE).

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Although transmission of infection to a healthy patient is difficult, there are certain patient populations that are readily predisposed to infection. For example, burn patients, patients who are obese, elderly, or diabetic, or those having poor nutritional status (e.g., alcoholics and drug abusers) are all at risk. Patients who smoke may also have an increased incidence of pulmonary infections [7-9]. In addition, the anesthesiologist today may be faced with an increasing number of patients with acquired or congenitally immunosuppressive diseases or who are receiving immunosuppressive treatments for transplantation or malignancy. Many of these patients may also present with unusual infections which have become opportunistic in the face of a compromised immune system. Indeed, infection is one of the leading causes of morbidity and mortality in these patients. Pneumonia, for example accounts for up to 40% of deaths among children and adults with cancer [3,4] and it has been estimated that 35% of renal transplant recipients develop pneumonia in the first year after transplantation [5].

The practice of anesthesiology has the potential for transmitting a number of infectious agents to the patient, since it often requires violation of the body's mechanical barriers. Placement of intravenous and intraarterial catheters, instrumentation of the airway, and mechanical ventilation all provide potential vehicles for transmission of infection [10]. However, although the potential for nosocomial transmission of infection in anesthesiology practice is real, there is very little data to support a cause and effect relationship. The contamination of anesthesia equipment and the potential for nosocomial transmission has long been a cause for concern. Indeed, as long ago as 1873, Skinner [11] decried the use of the same inhaler on successive patients without cleaning. However, the role of contaminated anesthesia equipment in the development of postoperative infections is controversial. Although outbreaks of Pseudomonas aeruginosa infections have been described in patients ventilated using a contaminated anesthesia machine, the use of disposable anesthestic circuits with bacterial filters has not been shown to improve the incidence of postoperative pulmonary infections [12,13]. In addition, the administration of anesthesia to patients with documented Gram-negative infections does not result in significant colonization of the anesthesia machine [14]. Blood and body fluid contamination of stopcocks, anesthesia machine working surfaces, monitor cables, drawer handles, oximeter probes, and patient anesthesia records have all been described, although their role in transmission of infection has not been established [15-17].

Although direct evidence of anesthesia-related transmission of infection is difficult to substantiate, certain anesthetic practices described in this study have been associated with infectious transmission. Use of a common syringe for the administration of drugs to more than one patient, for example, is a risky practice, even if a new sterile needle is used for each individual patient use [18]. Froggatt et al. [19] reported six patients who contracted acute HBV infections from a reused syringe that had come in contact with a contaminated stopcock from a hepatitis B carrier. More recently, a case of multiple patient-to-patient transmission of HIV in a private surgery clinic in Australia was described wherein the practice of reusing syringes from a potentially contaminated multidose local anesthetic vial was implicated [20,21]. Chant et al. [22] also reported on an investigation of possible patient-to-patient transmission of hepatitis C. In this case, transmission from the source patient to four other cases implicated either a reused syringe or contaminated anesthetic circuitry. It should be noted, however, that these modes of transmission have not been substantiated.

Recently, surveys from the CDC have implicated extrinsic contamination of propofol with cases of postoperative infection [23]. It is recommended that infusion solutions should be used on a one-time, one-patient basis. Studies show that contaminated infusions have resulted in bacterial and fungal infections when used on more than one patient [23]. The potential for transmission of nosocomial infection is further enhanced in the patient who is immunocompromised by disease or immunosuppressed by drugs. Indeed, many commonly used anesthetics are immunosuppressive and may compound the likelihood of pathogenic transmission [24-26]. Multidose vials generally contain preservatives and, therefore, can be used on more than one patient. However, care should be taken to clean the rubber septum with alcohol prior to each use. Vials that have obvious contamination should be discarded. Although transmission of infection by this route is uncommon, there have been reports of viral and bacterial infections linked to contaminated multidose vials [27,28].

Despite these examples, adherence to simple hygienic practices may be the best approach. For example, simple handwashing or the use of disposable gloves can prevent transmission of a number of pathogens [29]. Gwaltney et al. [30] showed that during experimental rhinovirus infections, transmission of the virus occurs in 73% of cases via the hands and only 8% via sneezing and coughing. In our study, although handwashing was fairly routine after high-risk exposure, only half of the respondents stated that they washed their hands after a low-risk patient.

The observation that 90% of anesthesiologists administer anesthesia while harboring an infection of the respiratory tract is perhaps not surprising, and although this does not imply that the practice results in transmission of the infection to the patient, it suggests an interesting area for future study. Similarly, anesthesiologists with active herpes simplex lesions should be reminded to wear a mask and gloves to prevent transmission to the patient during manipulation of the airway [31]. Anesthesiologists with herpetic whitlow on their hands should take care to cover the lesion with a dressing and gloves or avoid direct patient contact during exacerbations [32].

The potential biases in this study relate to self-report bias, sample representativeness, and nonresponse bias. In order to diminish the effect of a self-report bias, the questionnaire was designed to be completed anonymously, thus reducing the potential for respondents to intentionally report untrue behaviors. The demographics of the sample were very similar to those of the membership of the ASA suggesting that it was representative of anesthesiologists throughout the United States. Finally, despite the moderate response rate, analysis of a sample of the nonrespondents suggested that they were similar demographically to the respondents and had similar attitudes and behaviors. Comparisons between the demographics of the sample, the ASA, and the nonrespondents, together with tests of question reliability, are described in more detail elsewhere [6].

Although a cause-effect relationship between anesthesia practice, equipment contamination, and postoperative infection is not easy to establish, this survey suggests that there are several potentially hazardous practices that continue. However, in the absence of evidence to support anesthesiology-related transmission of infection, it may be inappropriate to label these breeches in recommended protocols as contributory or anesthesiology practice as necessarily "bad." It would seem, however, that the best approach would be to follow approved infection control guidelines where possible until evidence to the contrary is available. Certainly, it is not the purpose of this study to define the role of anesthesiology practice in the transmission of perioperative infection, but rather to describe the degree to which anesthesiologists adhere to recommended infection control guidelines. The fact that there are few documented cases of anesthesiology-related transmissions of infection should not be a cause for complacency, and every effort should be made to ensure that anesthesia personnel receive appropriate training and education regarding the implementation of universal precautions and other hygienic protocols in their clinical practice.

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