✓ Near-infrared spectroscopy (NIRS) of the cerebral hemispheres, applied transcranially through the intact scalp and skull, was evaluated for its ability to detect the presence of an intracranial hematoma in 46 head-injured patients. In 40 patients intracranial hematomas (22 subdural, 10 epidural, eight intracerebral) were identified on computerized tomography (CT); in all 40 cases, NIRS demonstrated greater absorption of light at 760 nm on the side of the hematoma. The mean difference in optical density (OD) between the hemisphere with the hematoma and the normal hemisphere was 0.99 ± 0.30 for epidural hematomas, 0.87 ± 0.31 for subdural hematomas, but only 0.41 ± 0.11 for intracerebral hematomas. In 36 patients, the asymmetry in OD resolved after surgical evacuation of the hematoma or with spontaneous resorption of the hematoma. Four patients who developed postoperative or delayed hematomas exhibited persistence of the asymmetry in OD. Six patients had only diffuse injuries and exhibited only minor differences in OD between the hemispheres, similar to 10 patients in the control group with no head injury. It appears that NIRS is useful in the initial examination of the head-injured patient, as an adjunct to CT, and in following patients postoperatively in the intensive care unit.
Shankar P. Gopinath, Claudia S. Robertson, Robert G. Grossman and Britton Chance
Shankar P. Gopinath, Claudia S. Robertson, Charles F. Contant, Raj K. Narayan, Robert G. Grossman and Britton Chance
✓ Delayed intracranial hematomas are an important treatable cause of secondary brain injury in patients with head trauma. Early identification and treatment of these lesions, which appear or enlarge after the initial computerized tomography (CT) scan, may improve neurological outcome. Serial examinations using near-infrared spectroscopy (NIRS) to detect the development of delayed hematomas were performed in 167 patients. The difference in absorbance of light (ΔOD) at 760 nm between the normal and the hematoma side was measured serially during the first 3 days after injury. Twenty-seven (16%) of the patients developed a type of late hematoma: intracerebral hematoma in eight, extracerebral hematoma in six, and postoperative hematoma in 13 patients. Eighteen of the delayed hematomas caused significant mass effect and required surgical evacuation. The hematomas appeared between 2 and 72 hours after admission. In 24 of the 27 patients, a significant increase (> 0.3) in the ΔOD occurred prior to an increase in intracranial pressure, a change in the neurological examination, or a change on CT scan. A favorable outcome occurred in 67% of the patients with delayed hematomas, which suggests that early diagnosis using NIRS may allow early treatment and reduce secondary injury caused by delayed hematomas.
Leslie N. Sutton, Alan C. McLaughlin, William Kemp, M. D. Schnall, Byung-Ku Cho, Thomas W. Langfitt and Britton Chance
✓ In order to study the metabolic events surrounding ischemia induced by the graded increase of cerebrospinal fluid (CSF) pressure, the technique of simultaneous phosphorus-31- and hydrogen-1-enhanced nuclear magnetic resonance spectroscopy was applied to five cats as intracranial pressure (ICP) was gradually raised by the instillation of mock CSF. Threshold lactate rose at an average cerebral perfusion pressure (CPP) of 49 torr, and, in general, preceded a threshold decrease in phosphocreatine, which was observed at an average CPP of 29 torr. There was considerable variation among cats in the CPP at which failure of brain energy metabolism occurred, however, suggesting differences in the autoregulatory curves. It is concluded that, with elevated ICP, there is no universally “safe” CPP at which brain energy metabolism may be assumed to be uncompromised.