Continuous monitoring of cerebrospinal fluid acid-base balance and oxygen metabolism in patients with severe head injury: pathophysiology and treatments for cerebral acidosis and ischemia.
BACKGROUND
Continuous monitoring of cerebral acid-base balance and oxygen metabolism has been introduced in neurointensive care settings. The hypothesis of this study utilizing multimodal neuromonitoring modalities is that hyperventilation and hypothermia improve cerebral acidosis through prevention of cerebral ischemia aggravation in patients with severe head injury.


METHODS
Continuous monitoring of cerebrospinal fluid (CSF) pH, PCO2, HCO3-, base excess (BE), PO2, SO2, temperature, lactate and pyruvate (La and Py) measurements were conducted in 8 patients with severe head injury. Temperature-corrected CSF parameters were correlated with those in the jugular blood including oxygen saturation (SjO2), regional oxygen saturation (rSO2), intracranial pressure (ICP) and cerebral perfusion pressure (CPP), jugular blood temperature (Tjb), and endtidal PCO2 (PetCO2). Therapeutic significance of hyperventilation and hypothermia was evaluated.


RESULTS
1) CSF acidosis was observed in all cases (minimum pH 6.59-7.17) due to increased CSF PCO2 and/or decreased CSF HCO3- and tended to associate with abnormal ICP and/or CPP or ischemic episodes indicated by CSF PO2 and SO2, rSO2, and/or SjO2 during monitoring. 2) It was more obvious in CSF than in jugular blood that increased PCO2, La and Py, and/or decreased HCO3- resulted in decreased BE and pH. 3) Decreased CSF PO2 and SO2 only correlated with severe CSF acidosis. 4) Hyperventilation: Decreased PetCO2 did not always closely correlate with CSF PCO2 decrease and CSFpH increase. 5) Hypothermia: There were negative correlations of Tjb with CSF pH and SO2 in all cases, though correlation coefficients were not always high.


CONCLUSIONS
CSF acidosis caused by increased CSF PCO2, La and Py, and/or decreased HCO3- tended to associate with abnormal ICP and CPP, and desaturation indicated by CSF SO2, rSO2, and/or SjO2. Hypothermia rather than hyperventilation tends to improve cerebral acidosis and ischemia.
Shiogai
T
T
Department of Neurosurgery, Kyorin University School of Medicine, Tokyo, Japan.
Nara
I
I
Saruta
K
K
Hara
M
M
Saito
I
I
D000138:Acidosis / Q000134:cerebrospinal fluid / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000628:therapy; D000293:Adolescent; D000328:Adult; D001930:Brain Injuries / Q000134:cerebrospinal fluid* / Q000150:complications / Q000175:diagnosis*; D002545:Brain Ischemia / Q000134:cerebrospinal fluid / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000628:therapy; D002245:Carbon Dioxide / Q000097:blood; D005334:Fever / Q000175:diagnosis / Q000209:etiology; D015600:Glasgow Coma Scale; D006801:Humans; D006985:Hyperventilation / Q000209:etiology; D007601:Jugular Veins / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D008875:Middle Aged; D008991:Monitoring, Physiologic; D010100:Oxygen / Q000134:cerebrospinal fluid*; D011182:Postoperative Care; D019289:Pyruvic Acid / Q000378:metabolism
D002245:Carbon Dioxide; D019344:Lactic Acid; D019289:Pyruvic Acid; D010100:Oxygen