fnlmsiueand MtirdCzwNursing(l994) 10, 121-126 63 Longman Group Ltd 1994

Knowledge of immunology is essential to plan effective nursing for immunocompromised patients

Caroline C. S. Johnson

INTRODUCTION

A patient with a compromised immune system

presents a major challenge to nurses. An under-

standing of the underlying cause of the patient’s

compromised state, the treatments indicated, and

the increased risk of infection which is inherent

in the condition, is vital. Nurses caring for these

patients must have the ability to identify the

patients at high risk of infection, be able to insti-

tute appropriate preventative measures, carry out proper assessment, and provide support and care

to the patients.

This is a vast subject. In order, therefore, to

bring it within the scope of this paper it is con-

fined within the parameters of intensive care. It is

essential that nurses caring for this group of patients should have a knowledge of immunolo-

gy. So a description of the workings of a normal

immune system precedes statement of the princi- ples of caring for these patients within an inten-

sive therapy unit (ITU) , followed by guidance on

assessment and management of patients at risk.

THE NORMAL IMMUNE SYSTEM

‘An understanding of the normal immune mech-

anisms is necessary in order to appreciate fully the

Caroline Johnson RGN, Diploma in Professional Studies, Charge Nurse, ITU, Western General Hospital, Edinburgh, UK

(Requests for offprints to CJ) Manuscript accepted 21 Feborary 1994

immune dysfunctions’, states Pratt (1986, p 23).

The immune system is responsible for helping to

maintain homeostasis, while protecting the body

from potentially damaging invading microorgan-

isms, for example bacteria, viruses, fungi and par- asites.

Before considering situations in which host

defence mechanisms have been ‘compromised’,

it is necessary to know something of the way in

which a normal individual resists infection by

microorganisms. There are two types of immune

response which work at the same time to combat

at invading ‘foreigner’. These two responses are

called:

1. The non-specific immune response

2. The specific immune response.

Non-specific immune response

Non-specific immunity, sometimes called innate,

is present from birth and directed to all foreign

material (Dawson 1988).

The first line of defence which an invading

microorganism meets is the physical barrier pro-

vided by the intact skin and mucous membranes.

Any breaches of these defences, for example pen- etration of intact skin and by-passing of the mucous embranes, exposes the host to infection.

Mucous membranes line the body cavities which open to the exterior, that is the digestive, respiratory, urinary and reproductive tracts. Their

defences consist of, for example, stickiness due to mucus which traps microorganisms, and the action of cilia; the cilia of the epithelium in the upper respiratory tract, for instance, move in such

121

122 INTENSIVE AND CRITICAL CARE NURSING

a manner that they pass inhaled dust and microbes which have become trapped’fn mucus towards the throat (Tortora & Anagnostakos

1987). There are several other ‘flushing action’ factors

which help to protect the epithelial surfaces of

the skin and mucous membranes and prevent colonisation of microbes, for instance the lacrimal apparatus and saliva. Certain chemical

factors, too, produce a degree of resistance of skin and mucous membranes to microbial invasion. Sebum secreted from the sebaceous glands forms a protective film over the skin and inhibits growth

of certain bacteria, and the high acidity of gastric juice will destroy bacteria and bacterial toxins.

The body also produces certain antimicrobial substances; among these are interferon and the complement system. Interferon is a protein man- ufactured by cells which are infected by a virus. It

disseminates to nearby infected cells, thereby pro-

tecting non-infected cells against attack by the virus. ‘Interferon appears to be the body’s first line of defence against infection by many differ- ent viruses’ state Tortora and Anagnostakos

(1987, p 539). The complement system is activat- ed by components of the bacterium’s cell wall and

can bring about destruction by cell lysis, or by

stimulating phagocytosis by other cell types. Another non-specific response of the body is

called phagocytosis, in which microorganisms, other cells or foreign particles are engulfed by phagocytes. The two main phagocytes involved are microphages and macrophages. Microphages,

or granular/polymorphonuclear lymphocytes, are found principally in the blood originating in

the bone marrow. There are three types of microphages, all containing slightly different chemicals: neutrophils, which have the most prominent phagocytic activity, eosinophils, which have some phagocytic capacity, and basophils, which have a debatable phagocytic role.

When an infection occurs, monocytes migrate to the infected area. The monocytes enlarge dur- ing this migration to form actively phagocytic cells called macrophages. Since these cells leave the blood to go to the infected area, they are called wandering macrophages. Some macrophages enter certain tissues and organs of the body and stay there. These fixed macrophages can be found

in the liver, lungs, brain, spleen, lymph nodes and bone marrow.

Other non-specific mechanisms are inflamma- tion and pyrexia. Inflammation increases the sup ply of chemicals such as complement by vasodila-

tion, and attracts phagocytes by chemotaxis. Complement (enzymatic proteins in normal

serum) combines with the antigen-antibody com-

plex to produce cell destruction (lysis) when the antigen is an intact cell. Pyrexia inhibits microbial growths and certain temperature-sensitive

pathogens. It speeds up the body’s reaction, which aids repair.

The specific immune response

There are two main mechanisms involved in spe- cific immunity. The first is the formation of spe- cially sensitised lymphocytes called T cells, which

have the capacity to attach to the foreign material

and destroy it. This is known as cell-mediated

immunity, and is effective against fungi, parasites, intracellular viral infections, cancer cells and for- eign tissue transplants. In the other mechanism, B cells produce circulating antibodies which are capable of attacking an invading agent. This is

known as humoral immunity and is particularly effective against bacterial and viral infections. These two components are a product of lymphoid tissue. Lymph tissue is strategically placed in the body to intercept an invading agent before it can spread too extensively into the general circula-

tion. The responses of T cells and B cells rely on the

ability of the cells to recognise specific antigens. In order for T cells and B cells to perform their vital function in immunity, macrophages must also participate. The macrophages process and present antigens to T cells and B cells. This is thought to occur when the macrophages phago- cytise the antigens. The partially digested antigen is then displayed on the surface of the macrophages for the T cells and B cells to recog- nise. During presentation of the antigen, macrophages secrete Interleukin 1, a powerful protein which induces proliferation of T cells and B cells. Once the cells become active they, in turn, induce macrophages to help in antigen destruc- tion.

INTENSIVE AND CRITICAL CARE NURSING 123

T cells and cell-mediated immunity

T cells are developed in the thymus and are capa-

ble of responding to a specific antigen. Most T

cells are inactive at any given time. When activat-

ed, T cells increase in size, differentiate and divide, each differentiated cell giving rise to a

clone. Several subpopulations of cells within the

clone can be recognised: Killer cells, Helper cells

and Memory cells.

Biller cells leave lymphoid tissue and migrate to

the site of invasion, where they attach to the

invading cell and secrete lymphotoxins which

destroy the antigen directly. Lymphotoxins also

produce holes in the plasma membrane of the

invading cells, resulting in their lysis. Killer cells

also secrete lymphokines which recruit additional

lymphocytes, attract macrophages and intensify

phagocytosis by macrophages. Also secreted is

Interferon, which exerts inhibition of viral repli-

cation and enhances the killing action of Killer

cells themselves. Killer cells are especially effec-

tive against slowly developing bacterial diseases

such as tuberculosis, brucellosis, some fungi,

transplanted cells and cancer cells.

Helper T cells cooperate with B cells to help

increase antibody production. Memory T cells

recognise the original invading antigen, should it

appear at a later date.

B cells and humoral immunity

B cells are derived from the bone marrow. When

stimulated by an antigen, the B cells change into

antibody-secreting plasma cells. Antibodies are

immunoglobulin (Ig) protein molecules and,

although there are five types of immunoglobu-

lins, only three are concerned in the response to

infection (IgM, IgG, IgA). Antibodies are power-

ful defence mechanisms against viruses, since

they neutralise viral infectivity. They are also important in combating bacterial infection princi- pally by the following actions:

1.

2.

3.

Neutralisation of toxins Promotion of phagocytosis by antibody coat- ing the bacteria Bacterial lysis (certain Gram negative bacilli are lysed in the presence of antibody and complement).

PRINCIPLES OF CARE

The care of a critically ill patient with a compro- mised immune system demands the highest stan-

dard of nursing skills; and, of course, identifying

and assessing patients at risk is a vital part of the

nurse’s role.

Immunodeficiency has become an increasingly

important problem for those involved in critical

care (Veale 1990). But what is an immunocom-

promised patient? Hotter (1990, p 194) states that

‘immunocompromise is a state in which one is at

increased risk of infection by an ineffective host

defense’. Blackwell and Weir (1981, p 79) state

that ‘any patient who has had his normal defenses

disrupted can be considered compromised and practical care must be taken to prevent infections

which in many cases can be fatal’. A patient

requiring intensive care can be defined as ‘one

who requires support of a vital function until the

disease process is arrested or ameliorated; such

patients are likely to have poor resistance to infec-

tion, sometimes due to immunosuppressive thera-

py or steroid therapy, or due to depression of the

immunological response’ (Ayliffe et al 1992,

p 295).

There are many diseases and therapeutic agents which cause disturbances of normal defence

mechanisms. Sometimes these are transient due

to viral infections or treatment, but sometimes

they are acquired from birth. Illness from any

cause associated with a lowering of natural resis-

tance; invasive procedures whereby the superft-

cial barriers are bypassed; the use of broad spec-

trum antibiotics causing changes in bacterial

flora; drugs, in particular steroids, cytotoxic drugs, and suppressive agents, all interefere with

the resistant mechanisms of the body, making

patients more susceptible to infection. Mild states of immune dysfunction are common, but owing to the extensive use of chemotherapy and the spread of HIV infection, severe states are becom- ing more common.

Patients in ITUs usually have a severe illness or

have had major surgery. Extremes of age and the general nutritional state of a person are also con- tributing factors which expose patients to the risk of ‘opportunistic’ organisms. Protein and calorie

124 INTENSIVE AND CRITICAL. CARE NURSING

malnutrition affects nearly every component of the defence system, including bactericidal killing by phagocytes and antibody production.

Patients are also exposed to greater hazards of contamination and cross-infection than most patients in ordinary wards. Sleigh and Timbury (1981, p 305) feel that ‘management of these patients often creates unnatural portals of entry for microorganisms by breaching the normal non-specific defense mechanisms’.

‘Opportunistic’ organisms include viruses, bac- teria, fungi and parasites and may be endoge- nous, for example Haemophilus injluenzae and pneumococci. These are normally of low pathogenicity in the upper respiratory tract but, when mucosal lining is damaged, will invade and cause infection in the lower respiratory tract. These organisms may also be exogenous,that is passed from staff, other patients or from the hos- pital environment. As Tinker and Porter (1980, p 116) state: ‘direct transmission of bacteria from the source to the host is most commonly via the hands of attending staff.

It is felt by many authors that nursing interven- tions for patients with compromised immune sys- tems should be directed towards prevention, early detection and treatment of infection (Gurevich 8~ Tafuro 1985, Reheis 1985, Miller et al 1986, Parapia 8c Collinson 1989, Lush & Wood 1989, Hotter 1990). ‘Caring for a patient with deficits of either external or internal defense mechanisms requires special preventative measures if infection is to be avoided’ (Gurevich & Tafuro 1985, p 257).

Assessing patients at risk

A thorough assessment of each immunocompro- mised patient is essential. A nurse’s observation skills are invaluable in detecting signs of an early infection and thus lessening the risk of a patient developing a life-threatening septicaemia.

Infection in an immunocompromised patient rarely presents in a typical fashion. As Cohen (1988, p 2322) states: ‘The classical signs of infec- tion reflect the host’s immune response to the pathogen and are often substantially modified in the compromised host, for example, a thin serous exudate may suffice for pus’. The absence of gran-

ulocytes means that the body cannot institute an inflammatory response when infection is present, and the usual signs of pain, erythema and swelling may be diminished or absent altogether. Certain steroid therapy may mask the elevation of temper- ature and, therefore, even small fluctuations in temperature should be regarded as suspicious and should be investigated.

Any invasive device which the patient may have, for example nutrition lines, intravenous/intra- arterial catheters, endotracheal/tracheostomy tubes, and urinary catheters, should always be considered as a possible focus of infection, as they facilitate entry of bacteria into the body. Any site of invasive cannulation is equivalent to an open wound and should, therefore, be covered with a sterile dressing. The use of such devices may be a major hazard to the patient already compromised by other drugs or procedures. ‘In the case of inva- sive procedures, it is vital that nurses look critical- ly at standards of care’ (Sedgwick 1990, p 627). Each nurse must assess the risks to patients and improve their chances of remaining infection- free by inspecting all body sites which carry a high potential risk of infection. A scoring system for the risk groups of patients could be an invaluable tool, but unfortunately, there is little in the litera- ture on such systems.

The oral mucosa is a frequent port of entry for infectious agents, and fastidious oral hygiene is necessary to minimise the opportunity of infec- tion (Greifzu et al 1990). The mouth should be inspected for strong, unpleasant odours, cracks, dryness, sores on lips, bleeding gums, mouth ulcers and candida albicans, a yeast-like fungus which commonly begins in the mouth but can quickly spread to the oesophagus or into the lungs. Such an infection can be extremely uncom- fortable and should be treated promptly to pre- vent systemic spread. Many patients benefit from prophylactic anti-fungal therapy to prevent such infections occurring. Herpes simplex shows itself as fluid-filled vesicles or painful open areas on the lips or mouth. The nurse should send a specimen from suspicious lesions to the laboratory for cul- ture and report signs immediately. There are many opportunities throughout the day for a nurse to observe those sites vulnerable to infec- tion from endogenous flora.

INTENSIVE AND CRITICAL CARE NURSING 125

Regular bacteriological surveillance is essential.

The collection of specimens from vulnerable

sites, for example tracheal secretions, urine, swabs

from discharging wounds and drain sites, enables

the microbiologist to identify the causative organ-

ism in an infection and then to determine the

best treatment. Clinical signs, too, such as unex- plained leucocytosis, leucopenia, thrombocytope-

nia, trachycardia, hypotension, all warrant atten-

tion.

Many problems which occur as a result of artifi-

cial ventilation can be prevented by good manage-

ment. Gram-negative organisms, for example

pseudomonas and klebisella, multiply rapidly in

moist environments unless prevented. As the

oropharynx is readily colonised by these organ-

isms, equipment such as endotracheal/tra-

cheostomy tubes, which bypass the respiratory

tract defence mechanisms, allow these organisms

direct access to the lower respiratory tract.

Preservation of skin integrity and avoidance of

skin trauma is imperative. Turning and reposi-

tioning of a dependent patient relieves pressure

on bony prominences. The patient’s skin should

be assessed using a suitable scoring device, for

example the Norton score or Water-low score sys-

tem (Dealey 1989). Intramuscular injections

should be avoided in neutropenic and thrombo-

cytopenic patients. Enemas, rectal medications

and rectal temperatures should also be avoided as

intestinal mucosa, already damaged by the under-

lying disease, can be easily traumatised.

Nurses must have high standards of hygiene in

order to prevent contact spread of infection.

Infection control measures within ITUs are

designed to protect patients from both endoge-

nous and exogenous sources of infection. Good

infection control begins with good hand-washing,

which is the single most effective method of

reducing cross-infection. The importance of this

measure is well-known and cannot be too highly stressed, and yet a discrepancy exists between the-

ory and practice (Tinker & Porter 1980, Williams & Buckles 1988, Campbell 1988, Ilott 1990). Hand-washing should be carried out before and after direct contact with a patient; before any inva-

the patient and the health-care system’ (Haller &

Rush 1992, p 61).

Unit policies on infection control must be

strictly adhered to if nurses are to reduce the risk of patients becoming infected from an exogenous

source. Sedgwick (1990, p 630) suggests that

nurses must assess their care by establishing some form of audit; one suggestion is ‘to use a system of

process surveillance which incorporates observa-

tion and the evaluation of practice which provides

the opportunity to evaluate and review the stan-

dards which have been set’.

The measures for infection control are not

expensive, but ‘they do, however, require cooper-

ation from all who come in contact with the

patient’ (Gurevich & Tafuro 1985, p 257).

CONCLUSION

Nurses must have a knowledge of immunology in

order to recognise the important role which they

have in caring effectively for patients with a com-

promised immune system. Failure to identify

these patients at risk may lead to life-threatening infections. It is essential that unit policies on

infection control measures are strictly adhered to,

so as to prevent contamination and cross-infec-

tion. There is a great need to devise a scoring sys-

tem for these ‘at risk’ patients, in order to initiate

prompt and appropriate management. Nurses who care for these patients within spe-

cialised units should share their knowledge with

new and inexperienced staff, thus helping them to gain insight and better understanding in the

care required for these patients.

By initiating and assisting in interventions

directed towards prevention and early detection

and treatment of infection, nurses have the

opportunity of making an invaluable contribution

to the safety and comfort of patients with a com- promised immune system.

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