La concepción de comunidad desde la dialéctica

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Emergency procedure 5

Table 4.7 Breakdown of the physiological variables with contribution to the APACHE II

score. APACHE II, Acute Physiology and Chronic Health Evaluation II; COPD, chronic obstructive pulmonary disease.

While clinical outcomes did not differ by treatment modality in the less

physiologically deranged population (APACHE II ≤15), for those with more

profound physiological derangement (APACHE II >15) there was a significant

difference in clinical outcome by treatment modality. Within this population there

tended to be more poor grade (WFNS ≥4) patients in the SC group, but on

multivariate analysis both poor grade and SC were predictors of poor outcome. Furthermore, functional outcome differences by treatment modality for the good

grade subgroup (WFNS grades 1–2) tended to significance (perhaps not reaching

significance as the study was underpowered), suggesting an effect independent of

presenting grade. In keeping with this, outcomes in the EVC group were improved

despite having a significantly greater number of older patients. SC was associated

with a marked increase in inotropic support (total norepinephrine dose), and hospital and ventilated days, suggesting a more profound physiological impact. This may

have been confounded by a higher incidence of vasospasm in the SC group but the incidence of severe vasospasm was similar, and on multivariate analysis, clipping

and poor WFNS grade were significant predictors of poor outcome of similar

magnitude in these patients, whereas vasospasm was not.

Functional outcomes for SC and EVC patients appeared to diverge with increasing APACHE II grouped scores along with degree of inotropic support, time ventilated, and hospital stay. The findings do suggest that the impact of the clipping procedure relative to a coiling procedure on deranged physiology may result in worse clinical outcomes.

These findings may give a clue as to why EVC is associated with better outcomes following treatment of aneurysmal SAH. Nevertheless, a clear underlying reason for these differences is uncertain. In one study, surgical and endovascular aneurysm therapies were associated with similar risks of cardiac injury and

dysfunction after SAH (Miss et al, 2004). Rates of postoperative pulmonary oedema

were also similar when the treatment modalities were compared (Horie et al, 2014).

Craniotomy and SC is associated with longer procedural times but whether it results in a greater systemic inflammatory response (which is known to complicate SAH)

(Yoshimoto et al, 2001) remains to be demonstrated. Immunodepression is also

known to complicate SAH (Sarrafzadeh et al, 2011)and predisposes to pneumonia

but the impact of aneurysm securing procedure has not been studied. Could a more minimally invasive aneurysm securing procedure limit these processes in some patients?

Common non-neurological complications of SAH include anaemia, hypertension, cardiac arrhythmia, fever, electrolyte changes, pulmonary oedema, pneumonia, hepatic dysfunction, renal dysfunction, and thrombocytopenia (Solenski

et al, 1995). Pneumonia, sepsis, fever, anaemia, and hyperglycaemia independently

predict poor outcome and death (Wartenberg et al, 2006). Medical complications are

linked to severity of presenting grade (Solenski et al, 1995). Additionally, a large

Canadian multicentre study demonstrated that SC patients more commonly suffered medical complications, such as urinary tract infection, pneumonia, cardiorespiratory arrest, and seizures, and that these complications were linked to poor outcome

(Vergouwen et al, 2011c). Our finding that SC patients with more profound

increased total norepinephrine dose, days ventilated, and hospital stay is consistent with this finding.

Many authors have attempted to explain the differences in outcome between patients undergoing EVC and SC through assessing the rates of cerebral vasospasm or delayed ischemia. Although there is some controversy regarding this, the general consensus is that that clipping results in more vasospasm and delayed ischemia

(Dumont et al, 2010; Dorhout Mees et al, 2012). Naidech et al, (2006) have also

demonstrated an association between baseline physiological derangement and rates

of infarction on CT. We demonstrated a significantly increased incidence of

moderate–severe vasospasm in the SC population with more deranged physiology (APACHE II >15) but not in the SC population with an APACHE II score of ≤15, which suggests that a possible synergistic effect may exist, with both physiological derangement and craniotomy/clipping combining to result in a greater risk of vasospasm. However, the rate of vasospasm in the coiled population with an APACHE II score ≤15 was higher than in the population with an APACHE II score >15, suggesting that physiological derangement did not necessarily contribute to the development of vasospasm. Furthermore, we did not demonstrate a difference in the rate of severe vasospasm between treatment modalities. Interestingly, vasospasm failed to represent an independent predictor of poor outcome but the majority of patients in this study were managed using a paradigm employing angiographic screening and pre-emptive hypertensive and endovascular management on

identification of significant angiographic vasospasm (Mortimer et al, 2015b),which

may limit its clinical impact.

The results of this study have implications for daily practice: the choice of whether to clip or coil an aneurysm has traditionally been made on the basis of morphological criteria, such as aneurysm location, size, and neck anatomy. We

suggest, on the basis of these findings, that as well as anatomical criteria it is worth

considering the physiological condition of the patient as one of the primary factors in assigning treatment modality. For example, is it preferable to clip a complex aneurysm in a medically unwell patient or would it be preferable to treat with partial

coiling of the dome (Waldau et al, 2012)in order that the patient can be brought back

than undergo an acute clipping procedure? This approach has not been answered by this study but certainly warrants future investigation.

This was a small explorative analysis, and although the data suggest some interesting findings, it is necessary to explore these concepts in a larger population. The data were not collected specifically to answer the impact of physiological derangement relative to aneurysm securing procedure on outcome. Dichotomising APACHE II score based on the available data introduces bias, and the assignment of treatment modality was not randomised so there is an inherent selection bias with respect to this also. The procedural complication rate was not specifically recorded. There were more posterior circulation aneurysms in the coiling group, and Fisher grade was not taken into account; it is plausible that the results were therefore biased by patients needing surgical haematoma evacuation being selected into the clipping group. However, in a recent prospective study of 381 consecutive SAH patients,

haematoma evacuation was a reason for SC in only 3% of patients (Cognard et al,

2014). Furthermore, in this study, SC was a significant predictor of poor outcome of

similar magnitude to poor WFNS grade (indicative of acute neurological injury) on multivariate analysis, and there also tended to be more favourable outcomes in the good grade (WFNS 1-2) subgroup with more deranged physiology (APACHE II >15) when coiled rather than clipped, suggesting an interaction between treatment modality and physiological derangement independent of the acute neurological injury.

An additional criticism of this study is that the short follow-up period of 90 days is likely to show a poorer outcome when assessing a more invasive intervention, such as a craniotomy. Ideally, if a future study were to be constructed to explore the interaction between deranged physiology, treatment modality, and outcome, a longer follow-up period would be needed. On the other hand, it could be argued that this is precisely the point; patients undergoing a more invasive procedure may require more inotropic support, more time ventilated, and more time in hospital. They could therefore take much longer to recover and are therefore more at risk of nosocomial infection and other medical complications. The results do therefore give an interesting insight into the role that physiological assessment could have in shaping the design of future prospective investigations.

4.6 Conclusion

In summary, we have demonstrated that in this population, more marked physiological derangement at baseline is a strong predictor of eventual poor outcome. These preliminary results also suggest that clinical outcomes for patients with more severe baseline physiological derangement could possibly be improved if undergoing a coiling rather than a clipping procedure but this should be investigated using a prospective approach in the future.

CHAPTER 5

THE NEGATIVE PREDICTIVE VALUE OF CT ANGIOGRAPHY IN