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Critical Care Outreach Nurse
This essay is potentially so vast in scope that I have made a tactical decision to tackle it by looking at:-
i) the reasons behind the scheme
ii) some of the criteria by which the various schemes operate and
iii) some technical issues that are relevant to the nursing process.
Because this is a Masters level essay I have dealt with a few areas in depth rather than many areas superficially.
Title
Nursing knowledge and theory in relation to respiratory assessment from the perspective of a critical care outreach nurse.
Introduction
The critical care outreach team is a concept that had been used in sporadic and largely experimental circumstances in various parts of the country during the mid to late 90s. To a large extent, these sporadic experiments were formalised with both the publication of the Government report Comprehensive Critical Care ( CCC 2001) and the Intensive Care Society's Standards and Guidelines (ICS 2002) (see on) . These documents recognised the need for both investigating, instigating and regulating change in the critical care environment by extending its horizons beyond the hitherto narrow confines of a super-select medico-surgical-anaesthetic speciality. (Stenhouse et al 2002)
In addition to the questions of potential efficacy, there was also the issue of whether such teams were actually cost effective(Cuthbertson 2003)
The fundamental reform in Comprehensive Critical Care paper, (CCC 2001) was the implementation of a number of teams whose main function was to assess, maintain contact with, and to support the patient at home in their immediate post-discharge period from the critical care unit. These teams came under the umbrella term of critical care outreach teams. The thinking was to not only improve the quality of care given to these patients, but also to allow a greater flexibility and more efficient usage of the beds in the critical care units throughout the country. (McDonnell et al.2005)
One of the catalysts for this transition came from a realisation, again in the late 90s, that some of the management of the critically ill, but recovering, patient was sporadic once they had left the hospital and was perhaps not as good as it might otherwise have been. Some authors (McQuillan et al 1998) politely described the care as sub-optimal.
Another was the parallel realisation that there was a certain inertia in transferring some patients who were already in hospital beds from the general wards into the CCU beds because of the consideration that the general wards could provide a higher standard of care than was actually realistic (McGloin 1999). The recommendations in this paper relate specifically to the Trusts in England and Wales. The Scottish Executive conducted its own investigation and concluded paradoxically that outreach teams and follow up would not significantly optimisepatient care or affect the workload of intensive care units (Scottish Executive 2000)
Discussion
The paper by Ball (et al. 2003) is a good place to start our considerations on the subject. It is a comparatively recent study into the value and the effect of the critical care outreach teams on clinical practice and patient outcome indices. It is a well written and instructive paper and therefore suitably informative for inclusion into a evidence-based appraisal of the issues (Sackett, 1996).
By the nature of the type of study, it should be noted that this is actually a non-randomised trial. Clearly it would be completely unethical to have a randomisation element if the authors believed that they were investigating an issue that was of potential benefit to the patients (Sugarman J & Sulmasy 2001).
The overall results showed that the critical care outreach teams studied managed to produce an overall improvement in survival rate of 6.8% and also, in the study period, a reduction in the readmission rate of 6.4%. On the one hand, one may observe that these percentages are single figures but, consideration of the overall type of problems and the care that such patients receive in the critical care environment, one has to suggest that these results are significant in their own right. (Harvey et al. 2005).
It is fair to observe that the bulk of the paper is a detailed dissection of the results obtained together with an equally detailed description of the statistical methods applied to derive the results. In short, this paper probably provides the definitive raison d'être for the existence of the critical care outreach team.
Because of the nature of our considerations here, it is worth considering the structure and results of this particular paper in rather more detail.
The specified outcome measures were simple and stark. They were measurement of survival time after discharge and the readmission rate. These were measured over a one year period (as a control) immediately preceding the inception of the critical care outreach team, and then the year immediately following it's inception.
The authors point to previous studies (Buist et al. 2002) & (Bristow et al. 2000) that had been done in the Antipodes with similar (but strategically different) Medical emergency teams. They were introduced in the early 90s, and therefore have had the opportunity to amass a greater experience an statistical evidence base. The significant difference however, is that they tend to be physician-led whereas the critical care outreach teams tend to be nurse led. However, they tend to respond to broadly the same clientele and broadly the same altered physiology. It is therefore possible to consider their results, but not to extrapolate directly from one situation to another.
Pathophysiology
The authors of the Ball paper (et al.2003) set out the clinical criteria by which their concerns were triggered:-
Respiratory rate < 8 breaths/min or > 25 breaths/min
Pulse oximetry < 90% on > 35% fractional inspired oxygen
Pulse < 50 beats/min or > 125 beats/min
Systolic blood pressure < 90 mm Hg, > 200 mm Hg, or > 40 mm Hg; less than patient's normal values
Urine output < 30 ml/h for more than two hours; unless normal for patient
Sustained alteration in level of consciousness or fall in Glasgow coma scale score of > 2 in past hour
Concerns about the patient
The latter criteria was overriding in all circumstances.
Because this essay is specifically concerning the respiratory aspect of the critical care outreach team, we will consider this aspect in rather greater detail. It must, of course, be recognised that in the context of critical care, there is frequently multi-organ involvement and pathology, as, by the very nature of the patients dealt with, they tend to all have pathophysiology of the more severe kind where organ systems are seldom affected in isolation and the co-existence of respiratory, metabolic and cardiac system abnormalities is commonplace. (Hamilton et al. 2002). To some extent it is therefore rather artificial to consider respiratory pathology in isolation, but for the purposes of this exercise we shall isolate it in this way.
The whole literature on the subject of respiratory critical care is enormous and clearly cannot be reflected in one essay. In this section we shall therefore focus on some specific issues that are relevant.
Pulse oximetry is a vital tool in assessing the respiratory (and perfusion) status of the patient. It is a vital tool in the decision-making process essential to the determination of the cardio-respiratory status of the critically ill (or perhaps post-critically ill) patient. (Secker et al. 1997)
Its actual determination is an assessment of the difference in the light absorption ratio between oxygenated and de-oxygenated haemoglobin.
(Van de Louw et al 2001). From this estimation the machine can make an assessment of the arterial oxygen saturation.
Technically, the machine has two LEDs which emit light of differing wavelengths which emit bursts of light about 400 times a second intermittently. A single detector samples each burst as it arrives. The machine takes readings over a complete pulse cycle and thereby is able to calculate the constant absorption of the wavelengths from both the tissue and the venous blood and subtract it from the variable absorption element of the arterial pulse. (Ralston et al. 1991)
Any variation of the pulse to pulse difference is averaged out over several beats and displayed as a constantly changing approximation. The actual derivation of the corresponding oxygenation value of the blood is an estimation based on the comparison with the readings from healthy volunteers and therefore there is some theoretical approximation to the possible true value. (Tittle et al. 1997)
From this explanation one can therefore clearly see that the method only actually measures the percentage of haemoglobin that is oxygenated. It does not reflect any measure of anaemia, or the efficiency with which that oxygenated haemoglobin is actually being perfused around the tissues (Grap MJ 2002)
For these (and other) reasons, there is considerable debate in the recent literature relating to the accuracy of the pulse oximeter. (Seguin et al. 2000)
The current consensus of opinion suggests that, with values above 70% the machine is accurate to within 2%, which certainly is as accurate as clinical decision making needs it to be. It is also relevant to note that the inventor of the pulse oximeter (Aoyagi et al. 2002), suggests that it is at its most accurate when the reading is about 85% and that the errors progressively increase as the readings deviate from this level
Similarly it is also considered accurate over pule rate ranges of about 25 -250 ppm. with an accuracy of greater than 2%. Again, this is well within the tolerance range of clinical need. (Maneker et al 1995)
In terms of relevance to our hypothetical critical care outreach nurse, we should also observe that the meter is highly portable and capable of detecting degrees of hypoxia more accurately and faster than virtually any other instrument that can be transported to a domicillary setting. (Aoyagi et al 2002)
In the clinical setting, the nurse must also be aware of the potential causes of clinically significant anomalies of reading. Two common variants of haemoglobin have quite different light absorbent spectra to oxygenated haemoglobin. Carboxyhaemoglobin is universally found in smokers (to a degree) and those with carbon monoxide poisoning (to a greater degree) and this can cause a degree of overestimation of oxygenation of the arterial blood to clinically significant levels.(Vegfors et al 1991)
Methaemoglobin is also found in conditions including the clinical use of lidocaine and nitrates (both commonly used in cardiac conditions) and this may cause clinically significant underestimation of arterial oxygenation.
(Varon 1992)
We have discussed (above) the potential for misleading readings in the presence of anaemia. Profound anaemia may take the readings below the clinically significant 70% levels. (Severinghaus et al 1990)
The nurse must also be aware of other potential sources of error including using the detector probe on fingers that have false nails or coloured nail varnish. As the basic measurement is one of colorometric evaluation, clearly such factors will add as huge and unacceptable variable into the readings.
(Ralston et al. 1991)
In the light of the consideration of the essay title, although such background knowledge is clearly desirable for the critical care outreach nurse, it is not as important as the knowledge of how to interpret the results from the patient.
In broad terms, readings in excess of 95% are considered to be both optimal and acceptable. Readings of 90% and below reflect a degree of desaturation. These comments are not absolute however, and reflect the importance of assimilating the readings alongside an assessment of the overall clinical condition of the patient. (Rutherford KA 1989)
Other potential pitfalls include significant anomalies of acid-base metabolism which affects the Henderson-Hasslebach relationship and therefore the oxygen/haemoglobin disassociation curve. Medications that are peripherally vasoactive may also impair or enhance perfusion profiles thereby importing elements of clinically significant anomaly into the readings. (Withington et al 1991)
The other major source of error is the fact that the detector is quite motion sensitive. This can also lead to anomalies of reading which can be clinically significant, particularly if associated with a significant bradycardia. (Wildman et al 1998)
On a final clinical note on this topic, some authors (Kelly et al. 2001) have pointed to the fact that patients with acute exacerbations of chronic obstructive pulmonary disease can give rise to spurious or anomalous readings. The normal cut-off for clinical suspicion of hypoxaemia is generally taken to be about 92%. The authors suggest that, in these specific circumstances, a reading of 95% is a better threshold to instigate treatment for this group of patients.
Within these parameters, the critical care outreach nurse can find that the oximeter is a very valuable, portable and easy to use tool that gives a huge amount of information very quickly and on a real time basis and will allow the nurse to make important value judgements on the overall condition of the patient.
Further discussion
Although we have considered the Ball paper in some detail, one should be aware of a further danger of extrapolation from it on too general a basis. Despite the comments made in the introduction regarding the seminal Government report (CCC. 2001) the actual nature, structure and remit of critical care outreach teams in different parts of the country have been quite disparate. On one extreme, some operate on a basis of one Consultant nurse to the other extreme of much larger multiprofessional teams (Goldhill et al. 2002).
It is instructive to consider the Standards and Guidelines suggested by the Intensive Care Society (ICS 2002) for the critical care outreach teams.
They are:-
i) To avert admission to CCUs
ii) To facilitate timely admission to the CCU and subsequent discharge back to the wards or patient's home
iii) Share critical care skills and experience through education and partnership
iv) Promote continuity of care
v) Ensure thorough audit and evaluation of the outreach scheme
It is salutary to note that there is suitable emphasis placed on the educative and audit processes that are associated with the whole critical care outreach team scheme.(Rowan et al 2004). It is, of course, important for all healthcare professionals to engage in the proper professional promotion (Langham et al 1996) of their particular specialist knowledge in the area and also to audit it to ensure that there is a proper evidence base for their activities. (Young et al 1996). It is vital for the continuance of the scheme to be able to demonstrate the fact that the scheme is both useful and cost effective.
Conclusions
In this essay we must accept that it is simply not possible to cover all aspects of the issues that are relevant to the question. This is no more than a simple recognition of the fact that the area is so broad in its scope that huge amounts of literature have already been written on the subject. (Hillman 2003)
We have therefore chosen to consider a few areas in some depth. >From our reading and investigation of the issues we have been able to point to evidence that the critical care outreach teams are both cost effective and clinically useful. In the interests of a balanced argument we must also present the opposing opinions of other authors. Subbe (2004) produces arguments that a simplistic view of the beneficial effects of the critical care outreach team is not appropriate, and that other factors may actually be responsible for the apparent improvement in patient outcomes. The author also suggests that the fact that there is an associated reduction in readmission rates, is actually a reflection of the fact that there is a devolution of responsibility. This may, of course, be a valid viewpoint.
The overall conclusions must be that, as in most fields of human research, if there is significant diversity of opinion, then this usually represents the fact that there is not enough firm information available to settle the argument one way or the other. This can only be realistically resolved by careful and objective audit and evaluation of the results from the critical care outreach teams as they become a more established element of the NHS service provision. (Parker 2004)
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