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Chapter: Clinical Anesthesiology: Anesthetic Equipment & Monitors : The Operating Room Environment

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Environmental Factors in the Operating Room

The temperature in most operating rooms seems uncomfortably cold to many conscious patients and, at times, to anesthesiologists.

Environmental Factors in the Operating Room

TEMPERATURE

The temperature in most operating rooms seems uncomfortably cold to many conscious patients and, at times, to anesthesiologists. However, scrub nurses and surgeons stand in surgical garb for hours under hot operating room lights. As a general principle, the comfort of operating room personnel must be reconciled with patient care. Hypothermia has been associated with an increased incidence of wound infection, greater intraoperative blood loss (impaired coagulation assessed by thromboelastography), and prolonged hospitalization .

HUMIDITY

In past decades, static discharges were a feared source of ignition in an operating room filled with flammable anesthetic vapors. Now humidity con-trol is more relevant to infection control practices. Optimally humidity levels in the operating room should be maintained between 50% and 55%. Below this range the dry air facilitates airborne motil-ity of particulate matter, which can be a vector for infection. At high humidity, dampness can affect the integrity of barrier devices such as sterile cloth drapes and pan liners.

VENTILATION

A high rate of operating room airflow decreases contamination of the surgical site. These flow rates, usually achieved by blending up to 80% recircu-lated air with fresh air, are engineered in a manner to decrease turbulent flow and be unidirectional. Although recirculation conserves energy costs associated with heating and air conditioning, it is unsuitable for WAGD. Therefore, a separate anes-thetic gas scavenging system must always supple-ment operating room ventilation. The operating room should maintain a slightly positive pressure to drive away gases that escape scavenging and should be designed so fresh air is introduced through or near the ceiling and air return is handled at or near floor level. Ventilation considerations must address air quality and volume changes. The National Fire Protection Agency (NFPA) recommends 25 air vol-ume exchanges per hour to decrease risk of stag-nation and bacterial growth. Air quality should be maintained by adequate air filtration using a 90% filter, defined simply as one that filters out 90% of particles presented. High-efficiency par-ticulate filters (HEPA) are frequently used but are not required by engineering or infection control standards.

NOISE

Multiple studies have demonstrated that expo-sure to noise can have a detrimental effect on mul-tiple human cognitive functions and may result in hearing impairment with prolonged exposure.Operating room noise has been measured at 70–80 decibels (dB) with frequent sound peaks exceeding 80 dB. As a reference, if your speaking voice has to be raised above conversational level, then ambient noise is approximated at 80 dB. Noise levels in the operating room approach the time-weighted aver-age (TWA) for which the Occupational Safety and Health Administration (OSHA) requires hearing protection. Orthopedic air chisels and neurosurgical drills can approach the noise levels of 125 dB, the level at which most human subjects begin to experi-ence pain.

IONIZING RADIATION

Radiation is an energy form that is found in spe-cific beams. For the anesthesia provider radiation is usually a component of either diagnostic imaging or radiation therapy. Examples include fluoroscopy, linear accelerators, computed tomography, directed beam therapy, proton therapy, and diagnostic radiographs. Human effects of radiation are mea-sured by units of absorbed doses such as the gray (Gy) and rads or equivalent dose units such as the Sievert (Sv) and Roentgen equivalent in man (REM). Radiation-sensitive organs such as eyes, thyroid, and gonads must be protected, as well as blood, bone marrow, and fetus. Radiation levels must be monitored if individuals are exposed to greater than 40 REM. The most common method of measurement is by film badge. Lifetime exposure can be tabulated by a required database of film badge wearers.A basic principle of radiation safety is to keep exposure “as low as reasonably practical”(ALARP). The principles of ALARP are protection from radiation exposure by the use of time, dis-tance, and shielding. The length of time of exposure is usually not an issue for simple radiographs such as chest films but can be significant in fluoroscopic procedures such as those commonly performed during interventional radiology, c-arm use, and in the diagnostic gastroenterology lab. Exposure can be reduced to the provider by increasing the dis-tance between the beam and the provider. Radiation exposure over distance follows the inverse square law. To illustrate, intensity is represented as 1/d2(where d= distance) so that 100 mRADs at 1 inch will be 0.01 mRADs at 100 inches. Shielding is the most reliable form of radiation protection; typical personal shielding is in the form of leaded apron and glasses. Physical shields are usually incorporated into radiological suites and can be as simple as a wall to stand behind or a rolling leaded shield to place between the beam and the provider. Although most modern facilities are designed in a very safe manner, providers can still be exposed to scattered radiation as atomic particles are bounced off shielding. For this reason radiation protection should be donned whenever ionizing radiation is used.

 

As use of reliable shielding has increased, the incidence of radiation-associated diseases of sen-sitive organs has decreased, with the exception of radiation-induced cataracts. Because protec-tive eyewear has not been consistently used to the same degree as other types of personal protection, radiation-induced cataracts are increasing among employees working in interventional radiology suites. Anesthesia providers who work in these environments should consider the use of leaded goggles or glasses to decrease the risk of such problems.

 

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