Friday, November 19, 2010

ICU Rounds Report - November 19th, 2010

From Lis
How bad is my hemorrhage, Doctor? Drs. Hunt, Hess and Fisher are often employed to help. Since the 1930's physicians have attempted to compile an adequate grading scale for sub-arachnoid hemorrhage. Ideally this scale would guide management decisions affected by severity, provide a working prognosis, allow for treatment research among the various grades, and monitor changes in severity in an individual patient.

Hunt and Hess (used at UVa):
The Hunt and Hess scale is a 1968 modification of an older scale (Botterell, 1956). The scale was designed to assess surgical risk and if patient is a surgical candidate when is the ideal time to operate. Today it is used to evaluate clinical outcome, which according to one study Hunt and Hess was the strongest predictor of clinical outcome at 6 months when compared to GCS/WFNS (Aulmann, 1998). The scale is built on three axes:
a. Intensity of meningeal inflammation reaction
b. Severity of neurological deficit
c. Level of arousal
d. Presence of significant associated systemic disease à increases grade by one level

The benefit of Hunt and Hess lie in its easy administration. Disadvantages include the low inter-rater reliability (κ = 0.42), vague terminology, and requiring the clinician to evaluate all three axes on a single scale. This forces us to choose which axis is most important and contributes to lax category boundaries and relatively arbitrary grading assignments. Finally, data indicates that there are only differences in outcome associated with some of the grades - specifically Grade 2 and 3 and Grade 3 and 4.

1  Asymptomatic or mild headache and slight nuchal rigidity
2  Moderate to severe headache, nuchal rigidity, no neurologic deficit except cranial nerve palsy
3  Drowsy or confused, mild focal neurological deficit
4  Stuporous, moderate or severe hemiparesis, possible early decerebrate rigidity and vegetative  disturbances
5  Coma, decerebrate rigidity, moribund appearance

The Fisher Scale is a 1980 scale designed to predict cerebral vasospasm based on the blood pattern seen on the first post bleed CT scan. The main advantage of the Fisher scale is the high level of inter- rater reliability (κ = 0.90). Since its development, clinicians have started using it as a clinical outcome predictor as well. However the newer scales are combining patient age, Hunt and Hess, and Fisher in order to improve the predictive strength of the scale. One example is the Olgilvy and Carter scale.

1 No blood detected
2 Diffuse deposition or thin layer with all vertical layers (in interhemispheric fissure, insular
cistern, ambient cistern) less than 1 mm thick.
3 Localized clot and/or vertical layers 1 mm or more in thickness
4 Intracerebral or intraventricular clot with diffuse or no subarachnoid blood
Aulmann C, Steudl WI, Feldmann U. [Validation of the prognostic accuracy of neurosurgical admission scales after rupture of
cerebral aneurysms]. Zentralbl Neurochir 1998;59:171–180.
Hunt W, Hess R. Surgical risk as related to time of intervention in the repair of intracranial aneurysms. J Neurosurg 1968;
Rosen DS, Macdonald RL. Subarachnoid hemorrhage grading scales: a systematic review. Neurocrit Care. 2005;2(2):110-8.

STATs note: Kappa scores are generally thought to be a more robust measure than simple percent agreement calculation since κ takes into account that the agreement may be occurring by chance. Recall that if the raters are in complete agreement then κ = 1. If there is no agreement among the raters (other than what would be expected by chance) then κ ≤ 0.
< 0
No agreement
0.0 — 0.20
Slight agreement
0.21 — 0.40
Fair agreement
0.41 — 0.60
Moderate agreement
0.61 — 0.80
Substantial agreement
0.81 — 1.00
Almost perfect agreement


No comments:

Post a Comment