Vasopressor Use and Effect on Blood Pressure After Severe Adult Traumatic Brain Injury

Background  

We describe institutional vasopressor usage, and examine the effect of vasopressors on hemodynamics: heart rate (HR), mean arterial blood pressure (MAP), intracranial pressure (ICP), cerebral perfusion pressure (CPP), brain tissue oxygenation (PbtO₂), and jugular venous oximetry (SjVO₂) in adults with severe traumatic brain injury (TBI).     

Application of P(jv-a) CO2 in monitoring cerebral oxygen supply-demand balance in injured brain

Transcranial Doppler sonography (TCD) assayed cerebral blood flow (CBF) may vary between different intracranial pathologies. Blood gas analysis of the jugular bulb provides a novel way to estimate the global relationship between CBF and oxygen metabolism. In this study, 25 patients with brain trauma, spontaneous intracerebral hemorrhage, and acute cerebral infarction were recruited. Jugular venous oxygen saturation (SjvO₂) increased significantly at different time points after hyperventilation (p < 0.05). A negative correlation between the partial pressure of CO₂ between jugular venous bulb and radial artery blood (P(jv-a)CO₂) and CBF could be observed in acute brain injury and spontaneous intracerebral hemorrhage groups, while P(jv-a)CO₂ and CBF show positive correlation in acute cerebral infarction group. Our results suggest that serial P(jv-a)CO₂ analysis combing with SjvO₂ can be utilized to monitor the change of CBF for patients undergoing craniocerebral surgery.     

Effects of hyperoxia, glycerol and ventricular drainage on ICP and CBF in patients with increased ICP due to CSF circulatory-absorbance disturbance

The effects of hyperoxia, glycerol and ventricular drainage on intracranial pressure (ICP) and cerebral blood flow (CBF) were studied in cases with cerebrospinal fluid (CSF) circulatory-absorbance disturbance due to subarachnoid hemorrhage (SAH) or intraventricular hematoma. Ventricular fluid pressure (VFP) was monitored through a controlled ventricular drainage (CVD) tube using a Statham P-50 pressure transducer. CBF was measured by the 10mCi133Xe intravenous injection method using a Valmet BI-1400 rCBF analyzer. ISI (initial slope index) was used for the CBF value. Studied cases were 19 SAH patients and 2 hypertensive intracerebral hematoma cases with intraventricular hematoma. Hyperoxia included hyperbaric oxygen (HBO), reduced ICP and CBF. During pure oxygen inhalation at atmospheric pressure (1ATA . O2), there was a tendency toward a relationship showing that the higher the resting state ICP, the lesser the likelihood of a CBF decrease. This may indicate that increased ICP impairs cerebral vascular reactivity to hyperoxia in relation to the degree of elevation. The effects of hyperoxia on ICP and CBF were temporary and they promptly returned to the resting state after cessation of oxygen inhalation. In some cases, there was a rebound phenomenon in ICP after HBO. Glycerol administration reduced ICP and increased CBF. There was no clear correlation between resting state ICP and CBF increase after glycerol administration. The effects of glycerol were also temporary. ICP control by opening CVD increased CBF. There was a correlation between the level of resting state ICP and the CBF increase after the opening of CVD. In cases with CSF circulatory-absorbance disturbance, elevated ICP reduced CBF and may further worsen the cerebral damage.(ABSTRACT TRUNCATED AT 250 WORDS)     

Brain Multimodality Monitoring: Updated Perspectives

The challenges posed by acute brain injury (ABI) involve the management of the initial insult in addition to downstream inflammation, edema, and ischemia that can result in secondary brain injury (SBI). SBI is often subclinical, but can be detected through physiologic changes. These changes serve as a surrogate for tissue injury/cell death and are captured by parameters measured by various monitors that measure intracranial pressure (ICP), cerebral blood flow (CBF), brain tissue oxygenation (PbtO₂), cerebral metabolism, and electrocortical activity. In the ideal setting, multimodality monitoring (MMM) integrates these neurological monitoring parameters with traditional hemodynamic monitoring and the physical exam, presenting the information needed to clinicians who can intervene before irreversible damage occurs. There are now consensus guidelines on the utilization of MMM, and there continue to be new advances and questions regarding its use. In this review, we examine these recommendations, recent evidence for MMM, and future directions for MMM.     

Cerebral blood flow autoregulation during intracranial hypertension: a simple, purely hydraulic mechanism?

Objective  In this paper, we re-propose the role of a hydraulic mechanism, acting where the bridging veins enter the dural sinuses in cerebral blood flow (CBF) autoregulation. Materials and methods  We carried out an intraventricular infusion in ten albino rabbits and increased intracranial pressure (ICP) up to arterial blood pressure (ABP) levels. We measured CBF velocity by an ultrasound probe applied to a by-pass inserted in a carotid artery and recorded ICP by an intraventricular needle. Diastolic and pulsatile ICP and ABP values were analyzed from basal conditions up to brain tamponade and vice versa. Conclusions  A biphasic pattern of pulsatile intracranial pressure (pICP) was observed in all trials. Initially, until the CBF velocity remained constant, pICP increased (from 1.2 to 5.4 mmHg) following a rise in diastolic intracranial pressure (dICP); thereafter, in spite of a further rise in dICP, pICP decreased (2.87 mmHg) following CBF velocity reduction until intracranial circulation arrest (pICP = 1.2 mmHg). A specular pattern was observed when the intraventricular infusion was stopped and CBF velocity returned to basal levels. These findings can be interpreted as indicating a hydraulic mechanism. Initially, when CBF is still constant, pICP rise is due to an increase in venous outflow resistance; subsequently, when CBF decreases following a further increase in venous outflow resistance, the vascular engorgement produces an arteriolar vasodilation. This vasodilation determines an increase in vascular wall stiffness, thus reducing pulse transmission to surrounding subarachnoid spaces. Commentaries on this paper are available at doi: and doi: .     

Alpha-Stat Versus pH-Stat Guided Ventilation in Patients with Large Ischemic Stroke Treated by Hypothermia

Background  Moderate hypothermia (MH) is a therapeutic approach for ischemic stroke as well as cardiac arrest. Two different technical strategies of ventilation during MH called alpha- and pH-stat dramatically influence cerebral blood flow (CBF). In turn this might influence neuronal damage and intracranial pressure (ICP). Therefore, effects of ventilation on CBF and ICP were measured in patients undergoing MH because of large ischemic stroke to address optimal ventilation management. Methods  Eight patients (n = 8) with large ischemic stroke in the territory of the middle cerebral artery (MCA) were treated by MH of 33°C within 24 h after symptom onset. MH was applied at least for 72 h. Each day, patients were ventilated repetitively with either alpha-stat or pH-stat for 60 min periods. Alpha-stat was applied between the measurements. ICP, CBF, and mean arterial blood pressure (MABP) were measured. The xenon clearance method was used to assess CBF at the bedside. Results  There were no significant differences between ICP values for alpha-stat or pH-stat during days 1 and 2 after induction of hypothermia. However, ICP was higher in the pH- as compared to the alpha-stat group (P < 0.05) and exceeded a mean of 20 mmHg on day 3. pH-stat led to a significant increase of CBF in all measures (P < 0.05), while MABP was unaffected. Conclusions  pH-stat implies a better CBF to the injured brain, while it might be dangerous by elevating ICP in more subacute stages.     

Reflectance spectrophotometry, cerebral blood flow and congestion in young rabbit brain

Reflectance spectrophotometry was applied to examine experimental cerebral oxygenation and hemodynamics in young rabbits. The estimated brain tissue SO2 level (ISO2) showed a prompt response to acute hypoxemia. The estimated brain tissue hemoglobin concentration (IHb) showed good correlation with CBF changes, estimated by the H2 clearance method, on hypoxemia or hypercarbia, and with cerebral congestion on neck venous compression. Moreover, trend recording of IHb and ISO2 was useful for monitoring the cerebral oxygenation and hemodynamic changes, including CBF as well as congestion.     

Pressures,Flow, and Brain Oxygenation During Plateau Waves of Intracranial Pressure

Background

Plateau waves are common in traumatic brain injury. They constitute abrupt increases of intracranial pressure (ICP) above 40 mmHg associated with a decrease in cerebral perfusion pressure (CPP). The aim of this study was to describe plateau waves characteristics with multimodal brain monitoring in head injured patients admitted in neurocritical care.

Methods

Prospective observational study in 18 multiple trauma patients with head injury admitted to Neurocritical Care Unit of Hospital Sao Joao in Porto. Multimodal systemic and brain monitoring of primary variables [heart rate, arterial blood pressure, ICP, CPP, pulse amplitude, end tidal CO₂, brain temperature, brain tissue oxygenation pressure, cerebral oximetry (CO) with transcutaneous near-infrared spectroscopy and cerebral blood flow (CBF)] and secondary variables related to cerebral compensatory reserve and cerebrovascular reactivity were supported by dedicated software ICM+ (www.neurosurg.cam.ac.uk/icmplus). The compiled data were analyzed in patients who developed plateau waves.

Results

In this study we identified 59 plateau waves that occurred in 44 % of the patients (8/18). During plateau waves CBF, cerebrovascular resistance, CO, and brain tissue oxygenation decreased. The duration and magnitude of plateau waves were greater in patients with working cerebrovascular reactivity. After the end of plateau wave, a hyperemic response was recorded in 64 % of cases with increase in CBF and brain oxygenation. The magnitude of hyperemia was associated with better autoregulation status and low oxygenation levels at baseline.

Conclusions

Multimodal brain monitoring facilitates identification and understanding of intrinsic vascular brain phenomenon, such as plateau waves, and may help the adequate management of acute head injury at bed side.     

Comparison Between Cerebral Tissue Oxygen Tension and Energy Metabolism in Experimental Subdural Hematoma

Background  

An experimental swine model (n = 7) simulating an acute subdural hematoma (ASDH) was employed (1) to explore the relation between the brain tissue oxygenation (PbtO₂) and the regional cerebral energy metabolism as obtained by microdialysis, and (2) to define the lowest level of PbtO₂ compatible with intact energy metabolism.     

动脉瘤早期手术夹闭后术区继发性脑内血肿的分析

目的 探讨早期手术成功夹闭动脉瘤之后,术区形成继发性脑内血肿的原因.方法 134例颅内动脉瘤开颅夹闭的患者中5例(3.7%)形成术后继发脑内血肿需二次开颅处理,分析术中(包括减压后)额叶挫裂伤程度、创面渗血和术中止血情况、脑压板对脑组织造成的损伤程度.1例难以止血者先留取部分脑挫裂伤组织提前送病理检查;4例第二次开颅清除血肿同时留取出血脑组织送病理检查,综合了解出血的原因.结果 5例手术中均发现蛛网膜下腔出血,脑肿胀明显,脑组织外观呈"紫红色";术中均有不同程度脑压板造成的损伤;病理主要表现为局部出血.出血周围可见"异常血管集中区",主要为细小静脉及毛细血管,血管呈弥漫扩张,部分血栓形成,一些血管壁明显厚薄不一,壁内见有少量中性白细胞浸润.结论 这种脑内血肿的发生与动脉瘤出血所致的早期脑肿胀、患者本身存在脑组织内小血管畸形及术中脑压板牵拉伤有关,术后严密观察能够早期发现,及时处理,效果良好.     

Independent compartment phenomena: characteristics of dynamics in cerebral tissue oxygen metabolism under increased intracranial pressure in immature brain: an experimental study

The aim of this study is to clarify the specific pathophysiology of increased intracranial pressure in an immature brain in relation to its unique cerebral blood flow dynamics and brain tissue oxygen metabolism. Thirteen puppies were used for an experimental model of brain herniation due to a massive intracerebral hematoma. Along with increasing size of the hematoma, the intracranial pressure (ICP), carotid blood flow (CBF) and cerebral tissue oxygen (CTPO2) were measured simultaneously and continuously. The tolerance capacity for an acutely expanding mass lesion, or intracranial compliance, was studied. The ratio of hematoma volume/body weight was obviously higher by more than 200% in a group of younger puppies with open cranial sutures. Dynamic changes of CTPO2 were noted to be independent in the cerebral subcortical region and the medulla oblongata, when Doppler detection of arterial pulsations showed no flow in the anterior circulation in association with increased intracranial pressure caused by a supratentorial expanding mass lesion. A case with open cranial sutures (1,500 g of body weight) clearly demonstrated this and survived over 24 hours. With acutely increasing ICP CTPO2 was elevated modestly in the cerebral subcortical region (p < 0.1) and prominently in the medulla oblongata (p < 0.005). In conclusion, the posterior fossa structure (brain stem and cerebellum) in the immature age group is protected from an acutely expanding mass lesion in the supratentorial compartment. The posterior fossa behaves as an independent compartment with more prominent CBF and CTPO2 reactivity in the dynamic changes. The author proposed to name these findings as "independent compartment phenomena".     

Fibrinolysis and aspiration of experimental intracerebral hematoma reduces the volume of ischemic brain in rats

Abstract

The hypothesis was tested in rats that brain ischemia by an intracerebral hematoma can be ameliorated by fibrinolysis and aspiration of the hematoma. Intraparenchymal blood clots were generated by the injection of 50μI of autologous blood into the right caudate nucleus in two portions seven minutes apart. Thirty or 120 min later 12 fil recombinant tissue plasminogen activator (rtPA) or 0.9% NaCI were injected and after 30 min the resolved hematoma was aspirated. Six hours later cerebral blood flow (CBF) was determined by 14C-iodoantipyrine autoradiography. Tissue volumes of CBF < 10 ml 1 00 g^–1 min-1 and CBF < 30 ml g"1 min’1 were determined. Clot and lesion volume were quantified histologically from serial sections stained for succinate-dehydrogenase (SDH) activity. In rtPA-treated rats the major part of the hematoma could be evacuated 30 min as well as 120 min after production of the clot. The volume of ischemic brain (CBF < 10) was significantly reduced fp<0.05) in the rtPA group compared to saline- treated and control groups irrespective of the time of treatment. In contrast, no difference was found between the control group and the experimental groups when the volumes of brain tissue surrounding the lesion were compared which had values of CBF<30 ml lOOgmin^–1. In a rat model of intracerebral hemorrhage, treatment by local fibrinolysis followed by aspiration of the hematoma is effective in reducing the volume of ischemic brain tissue and of the remaining clot volume. [Neurol Res 1999; 21: 517–523]     

Consistent Changes in Intracranial Pressure Waveform Morphology Induced by Acute Hypercapnic Cerebral Vasodilatation

Background  

Intracranial pressure (ICP) remains a pivotal physiological signal for managing brain injury and subarachnoid hemorrhage (SAH) patients in neurocritical care units. Given the vascular origin of the ICP, changes in ICP waveform morphology could be used to infer cerebrovascular changes. Clinical validation of this association in the setting of brain trauma, and SAH is challenging due to the multi-factorial influences on, and uncertainty of, the state of the cerebral vasculature.     

Effects of High-frequency Oscillatory Ventilation on Systemic and Cerebral Hemodynamics and Tissue Oxygenation: An Experimental Study in Pigs

Background

In this study, we compare the effects of high frequency oscillatory ventilation (HFOV) with those of lung-protective volume-controlled ventilation (VCV) on cerebral perfusion, tissue oxygenation, and cardiac function with and without acute intracranial hypertension (AICH).

Methods

Eight pigs with healthy lungs were studied during VCV with low tidal volume (V_T: 6 ml kg⁻¹) at four PEEP levels (5, 10, 15, 20 cmH₂O) followed by HFOV at corresponding transpulmonary pressures, first with normal ICP and then with AICH.

Systemic and pulmonary hemodynamics, cardiac function, cerebral perfusion pressure (CPP), cerebral blood flow (CBF), cerebral tissue oxygenation, and blood gases were measured after 10 min at each level. Transpulmonary pressures (TPP) were calculated at each PEEP level. The measurements were repeated with HFOV using continuous distending pressures (CDP) set at TPP plus 5 cmH₂O for the corresponding PEEP level. Both measurement series were repeated after intracranial pressure (ICP) had been raised to 30–40 cmH₂O with an intracranial balloon catheter.

Results

Cardiac output, stroke volume, MAP, CPP, and CBF were significantly higher during HFOV at normal ICP. Systemic and cerebral hemodynamics was significantly altered by AICH, but there were no differences attributable to the ventilatory mode.

Conclusion

HFOV is associated with less hemodynamic compromise than VCV, even when using small tidal volumes and low mean airway pressures. It does not impair cerebral perfusion or tissue oxygenation in animals with AICH, and could, therefore, be a useful ventilatory strategy to prevent lung failure in patients with traumatic brain injury.

     

Fibrinolysis and aspiration of experimental intracerebral hematoma reduces the volume of ischemic brain in rats.

The hypothesis was tested in rats that brain ischemia by an intracerebral hematoma can be ameliorated by fibrinolysis and aspiration of the hematoma. Intraparenchymal blood clots were generated by the injection of 50 microliters of autologous blood into the right caudate nucleus in two portions seven minutes apart. Thirty or 120 min later 12 microliters recombinant tissue plasminogen activator (rtPA) or 0.9% NaCl were injected and after 30 min the resolved hematoma was aspirated. Six hours later cerebral blood flow (CBF) was determined by 14C-iodoantipyrine autoradiography. Tissue volumes of CBF < 10 ml 100 g-1 min-1 and CBF < 30 ml g-1 min-1 were determined. Clot and lesion volume were quantified histologically from serial sections stained for succinate-dehydrogenase (SDH) activity. In rtPA-treated rats the major part of the hematoma could be evacuated 30 min as well as 120 min after production of the clot. The volume of ischemic brain (CBF < 10) was significantly reduced (p < 0.05) in the rtPA group compared to saline-treated and control groups irrespective of the time of treatment. In contrast, no difference was found between the control group and the experimental groups when the volumes of brain tissue surrounding the lesion were compared which had values of CBF < 30 ml 100 g-1 min-1. In a rat model of intracerebral hemorrhage, treatment by local fibrinolysis followed by aspiration of the hematoma is effective in reducing the volume of ischemic brain tissue and of the remaining clot volume.     

脑静脉血栓的治疗方法探讨

目的 探讨脑静脉血栓的治疗方法。方法对133例脑静脉血栓单独或联合采用经颈动脉溶栓、静脉窦内留置微导管连续溶栓、静脉窦成形（支架置入或球囊扩张）等方法进行治疗，同时辅以全身抗凝治疗。结果治疗后颅内压均明显下降，除１例ICP降至350mmH2O者失明，1例行静脉窦球囊扩张成形者（拒绝接受静脉窦支架置入）由术前760mmH2O降至450mmH2O外．其余病人ICP基本稳定在200-260mmH2O。颅内出血严重致脑疝死亡2例。溶栓后发生脑出血3例．均经手术治愈。结论同时应用血管内溶栓和全身抗凝是治疗脑静脉血栓较为可靠和安全的方法；血栓部位不同者治疗方案应个性化。     

Influence of cerebral oxygenation following severe head injury on neuropsychological testing

Abstract

Despite recent advances in the management of severe head injury the mortality and morbidity remains high. Intracranial pressure (ICP) and cerebral perfusion pressure (CPP) are crucial parameters for the correct management at the intensive care unit, due to their therapeutic and prognostic importance. In addition, regional brain tissue oxygenation (p_tiO₂) seems to be of importance. While different studies demonstrated the impact of cerebral hypoxia on outcome (mortality), no data are available focusing on morbidity (neuropsychological deficits). Therefore, our study is carried out to demonstrate a possible relationship between amount of cerebral oxygenation during acute stage after severe head injury and neuropsychological outcome. Besides ICP and CPP, p_tiO₂ was monitored in 40 severely head injured patients during the ICU stay from the day of admission until day 10. Monitoring data were stored and amount of hypoxic episodes were calculated. Besides outcome using the Glasgow Outcome Scale neuropsychological testing was performed 2–3 years after injury. Analysing the quality of brain tissue oxygenation, a relationship to the performance in neuropsychological tests could be found. Patients with low brain tissue oxygenation had a worse outcome in neuropsychological testing, especially concerning intelligence and memory. Associated with these deficits patients showed a reduced performance in their profession. Our data suggest a possible predictive value of brain tissue oxygen on morbidity analysing neurocognitive function after head injury. This may implicate monitoring and treatment of cerebral hypoxia.     

Intracranial pressure and cerebral oxygenation changes after decompressive craniectomy in a child with traumatic brain swelling

Case report The authors present the case of a 5-year-old child with severe traumatic brain injury in whom decompressive hemicraniectomy was performed for progressive increased intracranial pressure (ICP) unresponsive to medical treatment. Data from ICP and cerebral tissue oxygenation monitoring in the contralateral hemisphere were recorded, which demonstrated the immediate and delayed mechanical and physiological changes occurring after bony and dural decompression. Discussion The role of the procedure and that of the monitoring approach are discussed.     

Neuromonitoring: Brain oxygenation and microdialysis

Patients with cerebral lesions run a high risk of developing cerebral hypoxic and ischemic damage due to secondary insults. To minimize the risk of secondary cerebral hypoxia and ischemia, new monitoring techniques of cerebral oxygenation and metabolism have been developed and may help to understand the pathophysiology of secondary brain damage for a better treatment and outcome in critical patients. Cerebral microdialysis is a relatively new technique for measuring brain molecules of the extracellular space. The technical aspects, the interpretation of the commonly measured parameters, the use of the two commonly used oxygenation parameters (jugular venous oxygen saturation and monitoring of brain tissue PO₂ and the microdialysis technique to monitor cerebral metabolism in patients with head injury), subarachnoid hemorrhage, and ischemic stroke are considered. Pitfalls of the techniques and their future potential are discussed.     

Alterations in the intracranial venous sinuses in spontaneous nontraumatic chronic subdural hematomas

Occlusion of the cerebral venous system is frequently associated with intraparenchymal or subarachnoid hemorrhage. There are few reports of cerebral venous thrombosis associated with nontraumatic chronic subdural hematoma (CSH). We aimed to evaluate the intracranial venous system in patients with spontaneous nontraumatic CSH and to identify alterations in their venous sinuses. In this study, eight patients with spontaneous, nontraumatic CSH were followed for a 7-year period (mean: 2.2 years, range: 1–7 years). Neuroradiological images were taken at the onset of symptoms and during follow-up. Venous angiography or magnetic resonance venography was used to evaluate the cerebral venous system of patients. In all patients, medical or surgical treatments were based on clinical symptoms. In seven of the eight patients, the CSH was in the left hemisphere, whereas one patient had bilateral CSH. In one of the eight patients, thrombosis of the transverse sinus and sigmoid sinus was found, but recanalization was observed at follow-up. In a further three patients, the superior sagittal sinus, the straight sinus, and the vein of Galen were markedly reduced in diameter compared to normal or were not visible at presentation, but normal flow was observed at follow-up. In the remaining four patients, the transverse sinus was not observed at symptom onset or during long-term follow-up. A nontraumatic CSH can occur secondary to a venous thrombosis or it can be associated with the inability to image some of the venous sinuses. Venous flow was restored at long-term follow-up. Increased intravenous pressure is thought to be the pathogenic factor that causes a nontraumatic CSH.