Nutritional optimization in liver transplant patients: from the pre-transplant setting to post-transplant outcome

Background and study aims

malnutrition and its clinical phenotypes, sarcopenia, and frailty, are prevalent conditions that affect patients with cirrhosis awaiting liver transplantation. The link between malnutrition, sarcopenia, and frailty and a higher risk of complications or death (before and after liver transplantation) is well established. Accordingly, the optimization of nutritional status could optimize both access to liver transplantation and the outcome following the surgery. Whether optimization of nutritional status in patients awaiting LT is associated with improved outcomes after transplant is the focus of this review. This includes the use of specialized regimens such as immune-enhancing or branchedchain amino-acids-enhanced diets.

Results and conclusion

we discuss here the results of the few available studies in the field and provide an expert opinion of the obstacles that have led, so far, to an absence of benefit of such specialized regimens as compared to standard nutritional support. In the next future, combining nutritional optimization with exercise and enhanced recovery after surgery (ERAS) protocols could help optimize outcomes following liver transplantation.

Insuffisance rénale aiguë et syndrome hépatorénal chez le patient cirrhotique : actualités diagnostiques et thérapeutiques

La survenue d’une insuffisance rénale aiguë ou AKI (acute kidney injury) chez un patient cirrhotique est un événement de mauvais pronostic. Parmi les AKI, une entité spécifique au patient cirrhotique décompensé est le syndrome hépatorénal (SHR) dont la définition ainsi que la stratégie thérapeutique ont été réactualisées récemment. La prise en charge de l’AKI hors SHR n’est pas spécifique au patient cirrhotique. La prise en charge du SHR repose sur l’association d’un traitement vasoconstricteur intraveineux et d’un remplissage vasculaire par sérum d’albumine concentrée. Cette association thérapeutique permet d’améliorer le pronostic des patients répondeurs. En contexte d’AKI chez le patient cirrhotique, l’épuration extrarénale (EER) peut être envisagée en cas de non-réponse au traitement médical. La décision de débuter une prise en charge invasive avec EER dépend principalement de la présence d’un projet de transplantation hépatique (TH). En l’absence d’un tel projet, cette décision devrait être prise après évaluation du pronostic à court terme du patient dépendant du nombre de défaillance d’organes et d’autres variables telles que l’âge ou les comorbidités. L’objectif de cette mise au point est de discuter des récentes modifications de la définition de l’AKI et en particulier du SHR chez les patients cirrhotiques, de détailler la prise en charge spécifique du SHR et d’évoquer les processus décisionnels menant ou non à l’instauration d’une EER chez les patients non répondeurs au traitement médical en milieu réanimatoire.

Early-onset ventilator-associated pneumonia incidence in intensive care units: a surveillance-based study

Background

The incidence of ventilator-associated pneumonia (VAP) within the first 48 hours of intensive care unit (ICU) stay has been poorly investigated. The objective was to estimate early-onset VAP occurrence in ICUs within 48 hours after admission.

Methods

We analyzed data from prospective surveillance between 01/01/2001 and 31/12/2009 in 11 ICUs of Lyon hospitals (France). The inclusion criteria were: first ICU admission, not hospitalized before admission, invasive mechanical ventilation during first ICU day, free of antibiotics at admission, and ICU stay ≥ 48 hours. VAP was defined according to a national protocol. Its incidence was the number of events per 1,000 invasive mechanical ventilation-days. The Poisson regression model was fitted from day 2 (D2) to D8 to incident VAP to estimate the expected VAP incidence from D0 to D1 of ICU stay.

Results

Totally, 367 (10.8%) of 3,387 patients in 45,760 patient-days developed VAP within the first 9 days. The predicted cumulative VAP incidence at D0 and D1 was 5.3 (2.6-9.8) and 8.3 (6.1-11.1), respectively. The predicted cumulative VAP incidence was 23.0 (20.8-25.3) at D8. The proportion of missed VAP within 48 hours from admission was 11% (9%-17%).

Conclusions

Our study indicates underestimation of early-onset VAP incidence in ICUs, if only VAP occurring ≥ 48 hours are considered to be hospital-acquired. Clinicians should be encouraged to develop a strategy for early detection after ICU admission.

Estimating attributable mortality due to nosocomial infections acquired in intensive care units

BACKGROUND

The strength of the association between intensive care unit (ICU)-acquired nosocomial infections (NIs) and mortality might differ according to the methodological approach taken.

OBJECTIVE

To assess the association between ICU-acquired NIs and mortality using the concept of population-attributable fraction (PAF) for patient deaths caused by ICU-acquired NIs in a large cohort of critically ill patients.

SETTING

Eleven ICUs of a French university hospital.

DESIGN

We analyzed surveillance data on ICU-acquired NIs collected prospectively during the period from 1995 through 2003. The primary outcome was mortality from ICU-acquired NI stratified by site of infection. A matched-pair, case-control study was performed. Each patient who died before ICU discharge was defined as a case patient, and each patient who survived to ICU discharge was defined as a control patient. The PAF was calculated after adjustment for confounders by use of conditional logistic regression analysis.

RESULTS

Among 8,068 ICU patients, a total of 1,725 deceased patients were successfully matched with 1,725 control patients. The adjusted PAF due to ICU-acquired NI for patients who died before ICU discharge was 14.6% (95% confidence interval [CI], 14.4%-14.8%). Stratified by the type of infection, the PAF was 6.1% (95% CI, 5.7%-6.5%) for pulmonary infection, 3.2% (95% CI, 2.8%-3.5%) for central venous catheter infection, 1.7% (95% CI, 0.9%-2.5%) for bloodstream infection, and 0.0% (95% CI, -0.4% to 0.4%) for urinary tract infection.

CONCLUSIONS

ICU-acquired NI had an important effect on mortality. However, the statistical association between ICU-acquired NI and mortality tended to be less pronounced in findings based on the PAF than in study findings based on estimates of relative risk. Therefore, the choice of methods does matter when the burden of NI needs to be assessed.

Delayed rupture of traumatic aneurysm after civilian craniocerebral gunshot injury in children

BACKGROUND

There are few published large series on civilian craniocerebral gunshot injuries in children. Traumatic intracranial aneurysms (TICAs) are rare and highly unstable lesions. They represent less than 1% of all aneurysms and can either rupture within minutes after formation or remain quiescent for several weeks or years, manifesting with delayed hemorrhage and neurologic deterioration.

CASE HISTORY

We report the case of a 10-year-old girl who was referred for coma after high-velocity craniocerebral gunshot wound and neurological deterioration 7 days after the initial injury. A massive right posterior occipital hematoma caused by the rupture of an unsuspected right posterior cerebral artery TICA was discovered. TICA was treated by coil embolization, with a good neurological recovery at 6-month follow-up.

DISCUSSION

We discuss the pathogenesis and the management of TICA in a child after civilian craniocerebral gunshot injuries.

CONCLUSIONS

TICAs should be suspected in patients with civilian craniocerebral gunshot injuries, presenting with secondary neurological deterioration, to carry out emergent CT scan and angiographic exploration before contemplating definitive endovascular treatment. Endovascular management may be a prompt safe-to-use technique and a valuable option, especially when surgery is highly risky.

Assessment of jugular blood oxygen and lactate indices for detection of cerebral ischemia and prognosis

Levels of jugular blood oxygen saturation (SjvO2) and lactate have been proposed as indicators of cerebral ischemia and prognosis. However, sensitivity and specificity of these markers remain unknown. We retrospectively analyzed records of a series of 43 comatose patients at risk for cerebral ischemia, mainly after head injuries or subarachnoidal hemorrhage. Their SjvO2, jugulo-arterial lactate difference (VADLactate), and lactate-oxygen index (LOI) were determined every 8 hours. An increase in VADLactate and LOI was found, indicative of ischemia on CT scan, with threshold values of 0.30 mmol/L and 0.15, respectively. Sensitivity and specificity were 100% and 64%, respectively, for the VADLactate threshold, and 90% and 55%, respectively, for the LOI threshold. Regarding prediction of a poor outcome, only an increase in VADLactate had a predictive value with a sensitivity of 100% and specificity of 67%. No threshold value with sufficient sensitivity and specificity was found for SjvO2, as indicator of either ischemia or outcome. During progression to brain death, VADLactate and LOI reached abnormal levels earlier than cerebral perfusion pressure or SjvO2. They reacted markedly to focal ischemia due to vasospasm. Hyperlactacidemia rendered VADLactate and LOI uninterpretable by causing a brain lactate influx. Present data, if confirmed by a prospective study, would justify inclusion of intermittent VADLactate and LOI determinations in the multimodal cerebral monitoring.

[Transesophageal echocardiography and air embolism during posterior fossa neurosurgery. Intraoperative detection in the foramen ovale]

Sitting position during neurosurgery is discussed because the risk of venous air embolism and paradoxical air embolism is increased. Preoperative transoesophageal echocardiography is proposed to screen patients with patent foramen ovale to avoid them for the sitting position. This work reported 2 patients in conflict with this screening. It is discussed the physiological principles governing the paradoxical air embolism and the actual recommended monitoring for this position.

Craniocerebral injury resulting from transorbital stick penetration in children

OBJECTS

Two children were admitted to hospital for treatment of craniocerebral injury with transorbital penetration.

METHODS

One child aged 6 years and 6 months had poked a chopstick in his orbit. There was no report of either a palpebral or an ocular wound. He had subsequently developed a meningeal syndrome with a cerebral abscess managed by needle aspiration biopsy and intravenous antibiotics. The other child, aged 4, had fallen onto a metal rod. He presented with a palpebral wound, motor disorders and coma, all due to a frontal intracerebral hematoma. There was an improvement in outcome without complications of an infectious nature or motor sequelae.

CONCLUSIONS

Such head injuries are rare. Clinical, radiological and ophthalmological investigations must be performed, including computed tomography (CT) scan or cerebral magnetic resonance imaging (MRI) with antibiotic treatment for suspected microorganisms.

Hyperacute diffusion-weighted MRI in basilar occlusion treated with intra-arterial t-PA

Basilar artery thrombosis should be diagnosed immediately, as intra-arterial thrombolysis might improve the outcome. Diffusion-weighted (DWI)-MRI and three-dimensional time-of-flight MR angiography (3D TOF Turbo MRA) may provide additional insight into the extent of ischemia and the level of the occlusion. These methods could be helpful in the early classification of vertebrobasilar stroke, thus reserving the use of conventional angiography and possible intra-arterial thrombolysis for patients who had a severe clinical picture explained by preliminary assessments. We report the case of a 74-year-old woman who experienced a basilar artery occlusion; DWI-MRI and 3D TOF Turbo MRA provided noninvasive information concerning the level of arterial occlusion and its parenchymal ischemic impact, this leading to an intra-arterial thrombolytic therapy. These data suggest the feasibility of a noninvasive urgent diagnostic and prognostic approach with DWI-MRI and 3D TOF Turbo MRA in basilar occlusion.

[Cerebral deep vein thrombosis: three cases]

Cerebral internal venous thrombosis are rare and diagnosis is difficult. We report three cases in male adults. Clinical data were headaches, vomiting, dizziness and coma, in relation with an intracranial hypertension, or in a case, cardiocirculatory arrest. Cerebral internal veinous thrombosis was diagnosed by a CT scan and cerebral angiography twenty four hours after the admission in neurosurgical intensive care. CT scan showed hemorrhagic and ischemic lesions of thalami in two cases, diffuse cerebral edema in two patients, early or delayed hydrocephaly in two cases. No patient survived despite intensive treatment including heparinotherapy, ventricular CSF drainage, osmotherapy, dehydration, barbiturate, other antiepileptic drugs and mechanical ventilation. In two cases, general or local illness was found, sickle cell disease or radiotherapy for pineal tumor, and in case 3 clinical signs evoked autoimmune disease, not demonstrated by biological samples.

[Ventriculostomy of the third ventricle and diabetes insipidus]

We report the case of a 2-year-old child who sustained a permanent diabetes insipidus following a third ventriculostomy for hydrocephalus from a Dandy-Walker syndrome. Ventriculostomy, used for therapy of non-communicating hydrocephalus, can cause complications such as diabetes insipidus. The latter has rarely been reported and is usually transient. Following ventriculostomy, a close postoperative surveillance is essential, especially in children.

[Evaluation of ischemic repercussions of intracranial hypertension]

The main risk involved in severe intracranial hypertension is, the occurrence of cerebral ischaemia, either locally during herniation or globally as a consequence of reduced cerebral perfusion pressure (CPP). Neurological features of ischaemia occur at a late stage. A continuous monitoring of brain function with EEG or evoked potential techniques, while largely used in the operating room have not been so far fully evaluated in the intensive care setting. Therefore, ischaemic criteria based on the registration of haemodynamic or metabolic data are gaining importance in management of increased intracranial pressure (ICP). Transcranial Doppler of middle cerebral arteries allows at any time the detection of a decrease in brain perfusion. An increased pulsatility index has been repeatedly demonstrated to correlate with decreased CPP. From these reports, the lower limit of autoregulation in brain injured patients appears to be much higher (70 mmHg) than previously estimated (40 mmHg). However, therapies with a cerebral vasoconstrictor impact and associated vasospasm are to be considered for a correct interpretation of Doppler data. Moreover, as a reduced cerebral blood flow is not necessarily insufficient to meet metabolic requirements, a routine insight in cerebral oxygenation and lactate production must be available. Continuous monitoring of jugular blood oxyhaemoglobin saturation (SjO2) measures the reserve of oxygen extraction and a decrease in SjO2 below 50% is considered as to indicate an impending cerebral ischaemia. Indeed, critically reduced CPP under a 70 mmHg limit is reflected by venous desaturation episodes. Increased cerebral lactate production, routinely appraisable by serial measurements of [(a-v) lactate], may afford confirmation of an existing ischaemia. ICP and CPP monitoring remains the basis for intensive care surveillance during the phase of intracranial hypertension, with alarming settled at admitted critical values (ICP = 30 mmHg; CPP = 70 mmHg). As ischaemic threshold for cerebral blood flow may be different in patients and in normal experimental animals, the reliability of these critical values of ICP and CPP is uncertain. Therefore, transcranial Doppler, jugular metabolic monitoring and, as recently available, cortical tissue PO2 monitoring are mandatory for early detection and assessment of ischaemia.

[Sickle cell anemia and internal cerebral vein thrombosis]

Cerebrovascular disorders are frequently associated with sickle cell disease, mainly in homozygous children. We report the case a 25-old-patient with known sickle cell disease who presented with coma inaugurated by manifestations of intracranial hypertension. CT revealed bilateral thalamic infarcts and angiography confirmed the thrombosis of internal cerebral veins. Treatment included heparin and blood transfusion. Severe cerebral oedema resulted in the lethal outcome three days later.

Low brain tissue oxygen pressure: incidence and corrective therapies

In 16 head injured patients, the monitoring of brain tissue oxygen pressure (ti-pO2) show 22 episodes of low ti-pO2 (< or = 12 mmHg). Mean episode duration was 16 h. At time of the lowest ti-pO2 value, cerebral perfusion pressure (CPP), was < 60 mmHg in 5 cases, 4 of them with impending brain death. Oxygen saturation values of the jugular venous blood (svjO2) remained in the normal range (55-85 mmHg) in 12 cases and exceeded 85 mmHg in 3 cases, 2 of them with impending brain death. Lactate-oxygen index (LOI) was normal (< 0.08) in 7/10 cases and at very high level (> 0.60) in 3 cases including 2 cases of impending brain death. A first group of low ti-pO2 episodes was clearly related to an insufficient CPP level (n = 13), comprising 4 cases of parallel decrease in CPP and ti-pO2 until brain death, and 9 cases in which ti-pO2 was restored along with a significant increase in CPP (p < 0.001). In 5 patients, low ti-pO2 episodes were due to another cause: vasospasm (2 cases), hypoxemia, anemia and premature interruption of anesthesia. Appropriate treatments were effective in restoring ti-pO2 with no change in CPP. In 4 patients, the cause of low ti-pO2 was not identifiable and episodes resolved spontaneously. The results confirm the critical influence of CPP and ti-pO2. Patients in whom elevation of CPP improved ti-pO2 have normal range CPP during the episode. Optimal CPP should therefore be sometimes higher than recommended. ti-pO2 monitoring appears a good method to define the optimal CPP level in individual patient. The duration of the artefactual period after catheter placement is to clarify.

[Effect of anesthetics on sensory evoked potentials]

The authors have reviewed the main effects of anaesthetic agents on sensory evoked potentials (EPs) in the auditory, somatosensory and visual modalities. Knowledge of EP changes induced by anesthetic drugs is important to avoid false alarms when monitoring neural structures at risk during surgery. Intraoperative EP monitoring is all the more efficient as the following points are taken into account: 1) whatever the sensory modality considered, EPs are more attenuated by volatile halogenated agents than by intravenous drugs; 2) the cortical components of EPs are more sensitive to anesthetic drugs than the brainstem components; 3) in each modality, the first component of the "primary cortical complex" is less attenuated by anaesthetic agents than the following cortical waves; 4) continuous administration of anaesthetic agents rather than acute administration (bolus) is preferred during EP monitoring. EPs also represent an objective means to assess the depth of surgical anaesthesia, since they may provide a reliable index of cortical depression. Amplitude changes of middle-latency auditory responses (Pa/Nb) seem to be a good marker for estimating depth of anaesthesia with the aid of EPs.

The combined monitoring of brain stem auditory evoked potentials and intracranial pressure in coma. A study of 57 patients

Continuous monitoring of brainstem auditory evoked potentials (BAEPs) was carried out in 57 comatose patients for periods ranging from 5 hours to 13 days. In 53 cases intracranial pressure (ICP) was also simultaneously monitored. The study of relative changes of evoked potentials over time proved more relevant to prognosis than the mere consideration of "statistical normality" of waveforms; thus progressive degradation of the BAEPs was associated with a bad outcome even if the responses remained within normal limits. Contrary to previous reports, a normal BAEP obtained during the second week of coma did not necessarily indicate a good vital outcome; it could, however, do so in cases with a low probability of secondary insults. The simultaneous study of BAEPs and ICP showed that apparently significant (greater than 40 mm Hg) acute rises in ICP were not always followed by BAEP changes. The stability of BAEP's despite "significant" ICP rises was associated in our patients with a high probability of survival, while prolongation of central latency of BAEPs in response to ICP modifications was almost invariably followed by brain death. Continuous monitoring of brainstem responses provided a useful physiological counterpart to physical parameters such as ICP. Serial recording of cortical EPs should be added to BAEP monitoring to permit the early detection of rostrocaudal deterioration.

[Monitoring of intracranial pressure with intraparenchymal fiberoptic transducer. Technical aspects and clinical reliability]

A fiberoptic intracranial pressure transducer (Camino) was assessed prospectively in 100 patients. In all, 122 sensors were inserted intraparenchymally at the bedside, without the help of a neurosurgeon. Before the procedure, patients were given 2 to 4 mg of phenoperidine. The scalp was opened over a few millimeters in the frontal paramedian area. A burr holc was made with a 2 mm bit. The dura mater was opened and a hollow screw inserted in the diploë. When the zero of the transducer had been obtained, a 5 cm length was inserted within the screw. The transducer was then about 5 mm deep within cerebral parenchyma. The procedure took an average of about 15 min. An intracerebral haematoma around the transducer occurred five times. One had to be drained surgically. There were no infectious complications. The daily baseline drift was about 0.3 mmHg. The system seemed to be reliable: there was close agreement between the intracranial pressure (ICP), neurological status and CT scan findings. In trauma cases, there was also good correlation between mean ICP and the basal cistern obliteration score, finally, ICP became equivalent to mean arterial blood pressure in all brain dead patients. It is concluded that this system may be used in all cases where ICP requires to be monitored, even when the lateral ventricles are no longer visible, or when craniotomy has been performed. This will most probably result in a more extended use of ICP monitoring in neurosurgical intensive care.

[Treatment of ischemic cerebral edema with intracranial hypertension after neurosurgery of intracranial aneurysms]

Ischemic cerebral edema frequently develops after aneurysm surgery and may lead to severe intracranial hypertension. Of prime importance are reducing the level of ICP and preserving oligemic areas from becoming infarcted. Besides correction of factors known to worsen intracranial hypertension, several therapeutics may be of value: external CSF drainage, perfusion of mannitol, induced arterial hypertension and use of anesthetic agents with cerebral vasoconstricting capability. Hyperventilation is not recommended. Arterial hypotension and hypovolemia certainly contribute to aggravate cerebral ischemia and must be corrected. Cerebral ischemia may be reduced by two specific approaches: by improving cerebral oxygen transport in ischemic areas using arterial hypertension and calcium blockers rather than hemodilution or hypervolemia; by reducing cerebral metabolic rates with heavy anesthesia under the cover of a complete cardiovascular monitoring. In view of the large heterogenicity in cerebral lesions and physiopathological stages, a therapeutical trial appears suitable in each individual case. Criteria allowing to know if any therapeutic, used alone or in association, is beneficial include increase in blood flow in ischemic areas, reduction of ICP level and normalizing of indices like CSF or venous jugular blood lactate.

[Hyperthermia in meningeal hemorrhage. Contribution of daily determination of inflammation proteins]

This paper studies the causes of hyperthermias occurring after a subarachnoid hemorrhage by ruptured aneurysm in 54 patients, totalizing 66 febrils episodes. Only 29 episodes bacteriologically proved infections. The profile of thermic curve, the hemodynamical profile, and clinical examination are not convincing. The most convincing elements for the diagnosis of infection are the increasing number of the leucocytes counts, the increasing curve of CRP, and simultaneous decreasing curve of C4. The evolution of these parameters permit to follow the efficiency of antibiotics.

[Intracranial aneurysm and dysplasia of elastic tissue: pre- and postoperative problems]

From two cases of patients presenting a cerebral aneurysm associated with a dysplasia of elastic tissue, one a Marfan's syndrome, the other an anetoderma, this paper relate the post-operative, essentially cardio-vascularly and pulmonary complexities and define the elements of the pre-operative check-up.

[Neurogenic pulmonary edema, complication of meningeal hemorrhage: report of 4 cases]

Neurogenic pulmonary edema (NPE) observed in 4 patients admitted in Neurosurgical Intensive Care au SAH by ruptured a vascular malformation. This complication is unusual (1.9%) and has been observed in comatose patients. For 3 patients, NEP resorption was rapid, from 12 to 72 hours with a treatment by CCPV with a P.E.E.P. and with restoring the hemodynamical parameter. The drug must be discussed according to eventual deleterous side effects on cardiac output and systemic resistances. The early hemodynamical study argues for an essentially hemodynamical mechanism due to the brutal symphatic discharge created by cerebral lesions and increasing. ICP, more than a toxic lesionnal edema, as the Weidner's study shows it in ultrastructural analysis of sheep lungs.

[A rare and severe complication of meningeal hemorrhage: spinal arachnoiditis with paraplegia]

This observation relates a case of spinal arachnoiditis with paraplegia, for a 56 year old patient hospitalized for a S.A.H. by a ruptured aneurysm of the P.I.C.A. This patient present some complications, requiring a prolonged ventilatory support with a tracheostomy, a ventricular shunt for hydrocephalus. The treatment is only surgical, and the corticosteroids delay the evolution, but without successful outcome.

[Blood coagulation disorders in intracerebral hematoma caused by rupture of intracranial angioma. Incidences on hemorrhagic recurrence]

In 34 patients admitted in Neurological Intensive Care Unit, for a cerebral hematoma by ruptured arterio-venous malformation, are present in 26 patients, on the first day. In many cases, the APTT is increased and this can be respected. These disorders do not seem to modify the incidence of delayed hemorrhage, except for the severe perturbances, related to a DIC or an hepatic deficiency. In these cases, the delayed hemorrhage must be prevented by transfusions of platelets and/or freeze fresh plasma.

[Intracerebral hematoma caused by rupture of intracranial angioma. Analysis, prognosis and clinical course of 35 comatose patients admitted to intensive care units]

The outcome of 35 patients in deep coma (GSS less than 7) due to an intracerebral hematoma following ruptured arteriovenous malformation (AVM) and admitted to a neurosurgical intensive care unit is reviewed. Eighty percent of these patients had a cerebral AVM and 20% had an AVM in the posterior fossa. All had a medical treatment of increase intracranial pressure (ICP). Twenty-four patients or 68.6% had an early surgical treatment or some days further and 13 had a good outcome, six had a persistent coma or a residual neurological deficit and five died. Four patients or 11.4% had an endovascular embolisation therapy and three had no satisfactory results and one died; all had a new intracranial hemorrhage with hematoma. Seven patients were not treated: four died before 48 hours of hospitalisation, one is in persistent coma and two are waiting an endovascular embolisation, alive but with a neurological deficit. The results suggest that neurosurgical treatment are a safe and effective means for treatment of these AVM with compressive intracranial hematoma.

A controlled study of Dextran 40: effect on cerebral blood flow and metabolic rates in acute head trauma

A controlled double-blind evaluation of the effects of Dextran 40 at different concentrations on cerebral blood flow (CBF), cerebral oxygen consumption (CMRO2) and cerebral lactate production (CMRLact) was carried out. We studied 40 patients in coma due to recent head injury. Concentrations of Dextran solution were not significantly related to variations in CBF and metabolic rate over the period of infusion. The lack of effect of the Dextran infusion may be explained by the absence of global brain ischemia in these patients at the time of the study. The very low initial CBF values were a consequence of brain metabolic depression and not a sign of global ischaemia. The rheological benefits of treatment with Dextran 40 in head injured patients should preferably be investigated using techniques which permit detection of local changes in CBF and metabolism.

Transient drug-induced abolition of BAEPs in coma

Combined infusion of high doses of lidocaine and thiopental in a comatose patient induced major latency and amplitude BAEP changes, which progressed to complete BAEP abolition. Responses returned to normal after drugs were discontinued. EEGs during the episodes showed long-lasting periods of activity suppression, but were never isoelectric. BAEPs are resistant to hypothermia and barbiturates, but must be interpreted cautiously in patients treated with a combination of anesthetic drugs that includes lidocaine.

Brain-stem monitoring. I. A system for high-rate sequential BAEP recording and feature extraction

A computerized system is proposed for the continuous automatic monitoring of BAEPs in the intensive care unit or in the operating room. A new adaptive optimal digital filtering technique has been developed to allow BAEP recording with 200-400 stimulations, i.e., within 10-20 sec only, every 2 min. This method permits a selective cancellation of the major artifacts as soon as they occur: electrical interference and myogenic activities which are commonly encountered in such environments. An algorithm for automatic peak detection (waves I-V) has been implemented, and the whole system has been evaluated in terms of reduction of the intra-individual variability of latencies and amplitudes. Some clinical examples of comatose patient monitoring are briefly presented to illustrate the performance and the reliability of the system.

Brain-stem monitoring. II. Preterminal BAEP changes observed until brain death in deeply comatose patients

Preterminal BAEP changes were studied until brain death in 8 head-injured patients out of a series of 38 comas monitored by means of a system allowing high-rate sequential recording. Two different modalities of BAEP degradation were disclosed: (1) simultaneous latency increase of all components associated with a decrease of cerebral perfusion pressure (CPP), consistent with ongoing ischaemia of the posterior fossa; (2) deterioration of brain-stem components (waves III-V) with preserved or even enhanced wave I. The latter pattern was not consistently associated with any haemodynamic change and might be related to mechanical factors causing rostro-caudal deterioration of brain-stem function. The time course of BAEP degradation ranged from a few minutes to more than 10 h. In the case of slow preterminal evolution definitely pathological trends were identified even when individual BAEPs were still within normal limits. Such trends would have remained unnoticed in single BAEP records. Hypothermia and anaesthetic drugs were found to induce falsely alarming BAEP changes very similar to those seen during preterminal evolution. Our results suggest that continuous brain-stem monitoring could be helpful for management of comatose head-injured patients.