الفهرس 
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Abstract
93.
Head injury is an ancient cosmopolitan problem and actual references were made as early as the era of the Pharoes. About 26.24 % of comtatosed patients, admitted to Alexandria Main University Hospital, were due to head injuries in a recent study. Although every effort is done in the way of management yet mortality and morbidity rates are high. The optimal management should involve an aggressive multisystem and multidisciplinary approach to diagnosis and treatment. Arterial blood gases should be obtained in all unconscious patients including those who display grossly normal spontaneous ventilation.
The present study aimed at detecting changes in blood gases and acid base status that possibly may alter the prognosis, and to give an explanation about the underlying causes in a trial to avoid their dangerous sequellae.
Twenty comatosed patients due to head injury had been studied prospectively. Patients had undergone a complete physical and clinical examination. The degree of coma was assessed according to Glasgow Coma Scale. Respiratory rate was recorded by observation and tidal volume by Wright’s repirometer. Minute ventilation was
.
obtained by multiplying the respiratory rate by tidal volume. Mean
arterial blood pressure was calculated from the following equation:
~. -. . Pulse pressure
= Diastolic pressure + S
Arterial blood gases and acid base parameters were obtained using ABL2 Acid Base Laboratory of Radiometer-Copenhagen. Mean values and standard deviation of all parameters were obtained for comparative study. ”F” test and ”t” test were used as tests of significance.
A group of 10 patients were included in our study as a control. They were admitted for minor surgical operations and they proved to be clinically free.
The average age of our patients was 25 years with 3/1 male/female ratio. Such low average age compared to other countries was because 55 % of our patients were young people under 20. Three-quarters of head injuries were resulted from motor vehicle accidents. Twenty percent of patients had other associated injuries mostly long bone fractures, Fifty five percent of patients were transported by ambulance in an average of 88 minutes/patient and 45 % of patients by private means in an average of 46 minutes/patient. Prolonged time showed by ambulance was because ambulance was used in transporting patients from far distances. Fifteen percent of patients had a clear wairway and all of them survived. The rest were presented by symptoms and signs of respiratory obstruction.
Aspiration had been assumed in 55 % of patients. None of the aspirated patients has survived. Wrong head positioning during transportation in the unconscious patients made aspiration very likely to occur. X-ray was not helpful in diagnosis of aspiration in the majority of cases.
We had 60 % mortality rate. The worst outcome related to the age was encountered in victims under 20, which was not the case in other countries. Young people met in this study seemed to have more severe head injuries than their fellows in other studies.
The mean pH of all comatosed patients was 7.456. Such significant higher difference from control and accompanied low (XL 31.89 mm Hg located most of our patients in the area of acute hypocapnia in Siggaard-Andersen Chart. The degree of respiratory alkalosis in our study was directly proportional with the depth of coma and heighest mean pH value was recorded in the non survived group 7.481. Such respiratory alkalosis has been emphasized by other authors. Hyperventilation was explained as the more severe the brain damage and hypoxia both will lead to accumulation of lactate in CSF. Association between such brain acidosis and development of compensatory pulmonary hyperventilation has been emphasized by many authors.
Mixed respiratory alkalosis and metabolic acidosis was reported in a number of patients. Metabolic acidosis was explained by the hypotensive state which had accompanied some patients or due to seizure activity. Hypoxia was a feature between the different: groups of our patients and was crucial in determining their outcome. Survivors had PaO,-, 76.6 mm Hg significantly higher than that of non survivors 63.9 mm Hg. Such hypoxia was due to airway obstruction and aspiration. Central mechanism-induced hypoxia was also suggested but could not be proved in this study.
Hypocapnia was prevalent in all groups of patients included in the present study. The mean PaCCL was 31.89 mm Hg. The difference of PaCO„ inbetween the different grades of coma was insignificant. The direct reason for such obvious hypocapnia can be attributed to spontaneous hyperventilation as a common feature after head trauma.
Tachypnea was observed in most of patients. Respiratory rate was higher and was directly proportional to the depth of coma but the difference was not significant. Patients with obstructed airway had insignificant higher respiratory rate than the non obstructed patients. All the studied groups of patients showed a non significant low minute volume in relation to the control.The only exception was in the group of patients who recovered with deficit.
Mean arterial blood pressure was almost around normal in most of our patients. The groups which showed slight increase of mean arterial blood pressure were patients in deep coma and that was explained by the increase in intracranial pressure. The othe group was patients transported by ambulance from other hospitals at which they received intravenous replacement therapy.<br