cyclic-gmp and Coma

To determine the role of cerebral vasoconstriction in the delayed hypoperfusion phase in comatose patients after cardiac arrest.. Prospective study.. Medical intensive care unit in a university hospital.. 10 comatose patients (Glasgow Coma Score +/- 6)successfully resuscitated from a cardiac arrest occurring outside the hospital.. We measured the pulsatility index (PI) and mean blood flow velocity (MFV) of the middle cerebral artery, the cerebral oxygen extraction ratio and jugular bulb levels of endothelin, nitrate, and cGMP during the first 24 h after cardiac arrest.. The PI decreased significantly from 1.86 +/- 1.02 to 1.05 +/- 0.22 (p = 0.03). The MFV increased significantly from 29 +/- 10 to 62 +/- 25 cm/s (p = 0.003). Cerebral oxygen extraction ratio decreased also from 0.39 +/- 0.13 to 0.24 +/- 0.11 (p = 0.015). Endothelin levels were high but did not change during the study period. Nitrate levels varied widely and showed a slight but significant decrease from 37.1 mumol/l (median; 25th-75th percentiles: 26.8-61.6) to 31.3 mumol/l (22.1-39.6) (p = 0.04). Cyclic guanosine monophosphate levels increased significantly from 2.95 mumol/l (median; 25th-75th percentiles: 2.48-5.43) to 7.5 mumol/l (6.20-14.0) (p = 0.02).. We found evidence of increased cerebrovascular resistance during the first 24 h after cardiac arrest with persistent high endothelin levels, gradually decreasing nitrate levels, and gradually increasing cGMP levels, This suggests that active cerebral vasoconstriction due to an imbalance between local vasodilators and vasoconstrictors plays a role in the delayed hypoperfusion phase.

Topics: Adult; Aged; Aged, 80 and over; Brain Ischemia; Cardiopulmonary Resuscitation; Cerebrovascular Circulation; Coma; Critical Care; Cyclic GMP; Endothelin-1; Female; Heart Arrest; Humans; Male; Middle Aged; Nitrates; Prospective Studies; Vascular Resistance

Topics: Coma; Cyclic AMP; Cyclic GMP; Humans; Hydrocephalus

The effects of insulin-induced hypoglycemic stupor and subsequent treatment with glucose on mouse cerebral cortical, cerebellar and brain stem levels of glucose, glycogen, ATP, phosphocreatine, glutamate, aspartate and GABA and on cerebral cortical and cerebellar levels of cyclic AMP and cyclic GMP have been measured. Hypoglycemia decreased glucose, glycogen and glutamate levels and had no effect on ATP levels in all three regions of brain. GABA levels were decreased only in cerebellum. Aspartate levels rose in cerebral cortex and brain stem, and creatine phosphate increased in cerebral cortex and cerebellum. In the hypoglycemic stuporous animals, cyclic GMP levels were elevated in cerebral cortex and depressed in cerebellum whereas cyclic AMP levels were unchanged from control values. Intravenous administration of 2.5-3.5 mmol/kg of glucose to the hypoglycemic stuporous animals produced recovery of near normal neurological function within 45 s. Only brain glucose and aspartate levels returned to normal prior to behavioral recovery. These results suggest that of the several substances examined in this study, only glucose and perhaps aspartate have important roles in the biochemical mechanisms producing neurological abnormalities in hypoglycemic animals.

Topics: Adenosine Monophosphate; Adenosine Triphosphate; Amino Acids; Animals; Aspartic Acid; Behavior, Animal; Central Nervous System; Coma; Cyclic AMP; Cyclic GMP; gamma-Aminobutyric Acid; Glucose; Glutamic Acid; Glycogen; Hypoglycemia; Insulin; Male; Mice; Phosphocreatine; Recovery of Function

A previous study showed that cerebrospinal fluid from the lateral ventricle of patients without disturbance of sensorium or intracranial pressure contains 15 to 30 nm 3', 5' cyclic adenosine monophosphate. We measured the concentration of this cyclic nucleotide by radioimmunoassay in cerebrospinal fluid from the lateral ventricle of six patients with prolonged coma (20 days or longer) after head trauma (four), or spontaneous intracranial hemorrhage (two). Coma was graded IV to I in order of decreasing severity. Fluid was removed at intervals of six to 72 hours from a Rickham reservoir placed in the lateral ventricle. Concentration of the cyclic nucleotide (mean +/- S.E.M.) in coma of Grades IV, III, II and I was 2.1 +/- 0.3, 4.6 +/- 0.5, 6.3 +/- 1.4 and 12.5 +/- 2.4 nM respectively. After sensorium became normal, cAMP was 21.0 +/- 1.4 nM. Correlation between grade of coma and concentration was -0.89 (P less than 0.01). Thus, prolonged coma appears to be associated with a disturbance of cyclic AMP metabolism within the central nervous system.

Topics: Adult; Cerebral Hemorrhage; Cerebral Ventricles; Coma; Craniocerebral Trauma; Cyclic AMP; Cyclic GMP; Female; Humans; Intracranial Pressure; Male; Middle Aged; Time Factors; Unconsciousness