| It is the focal point for the prevention and therapeutics of the secondary insults factors such as shock, hypoxemia, hyperpyrexia, disturbance of water-electrolyte, and acid-base balance after the severe head injury. The respiratory failure, one of the most common complications resulting in severe hypoxemia, mainly contributes to the high mortality rate and poor outcome. For these patients application of breathing apparatus is usually inevitable. However there are different viewpoints for the effects of varying mechanical ventilation modes on the intracranial pressure (ICP) and cerebral hemodynamics. It has significance to investigate how to operate the breathing apparatus reasonably in order to improving the oxygen supply, minimizing the negative effects on the ICP and cerebral perfusion pressure (CPP), and building a better internal environment for the recovery of cerebral function.We introduced intracranial hematoma in dogs by autologous blood-clotting injection into the frontal white matter then produced the hypoxemia by lipopolysaccharide (LPS) intravenously infusion. The static pressure-volume curve of total respiratory system was measured and the effects of varying levels of positive end-expiratory pressure (PEEP) on ICP and CPP were investigated. In addition a clinical study was performed on 6 patients who suffered from the respiratory insufficiency after severe head injuries. This research consists of two parts:Part I Animal ExperimentObjective: To investigate the compliance variation of respiratory system in dogs with hypoxemia after intracerebral hematoma and the effects of varying levels of PEEP on hemodynamics (HD), ICP and CPP.Methods: 32 anaesthetized dogs were randomly divided into four groups: I brain injury group: autologous blood clotting was injected into the right frontal lobe to replicate an intracerebral hematoma resulting in intracranial hypertention; II brain injury plus endotoxin group: after the intracerebral hematoma was induced low dose lipopolysaccharide (LPS) was infused (20μg/kg); III endotoxin group: LPS was infused; IV contral group. The static pressure-volume curve of respiratory system was measured in initial (all groups), intracranial hypertension (group I and group II), hypoxemia (group II and group III). A protocol entailing variation of PEEP to 0, 3, 6, 9, 12, 15, 18, OcmH2O was performed. Mean arterial blood pressure (MAP), ICP, heart rate (HR), CVP, blood gas were recorded.Results: ①In group I and group II ICP (initial 17.91±3.98 mmHg) went rapidly up to a peak of volume of 73.36 ±17.34 mmHg and then descended to 41.91 ±9.66 mmHg in 30 minutes after blood were injected ( Volume of injected blood was 4.8-11.5ml , mean 8.48 ml). The ICP still remained in a high level of 30.27 ±8.26 mmHg in 4 hours (comparing to initial .P<0.01) whereas the ICP of contral group had no notable change (initial 14.67±2.08 mmHg, in 5 hours 14.00±2.65mmHg). ②In the infusion process of group I and II MAP increased slightly, ICP raised sharply thus CPP decreased significantly. MAP descended gradually to a little lower level than pre-injection blood after the infusion while CPP decreased concomitantly. CVP decreased after the LPS infusion in group III. PaO2 was found obviously descent following the blood injection in group I and II (initial 128 ± 32.35mmHg vs. 98.93 ±8.7mmHg). ③In the group II and III PaO2 decreased gradually after the LPS administration. It did not reach the ARDS criteria (PaO2/FiO2<200) until 2.5-3 hours later. The descent range in group II is greater than in group III. ④ The P-V curve of respiratory system shifted to right in group I and II after induced intracranial hypertension. In group II further shift was found after LPS infusion. This shift in group III occurred similarly. The average compliance of respiratory system in all three groups was significantly decreased (comparing within group P<0.01). At the corresponding time the compliance had notobviously changed in control group. (5) After the administration of LPS th...
|
PDF Full Text Request