Andrea Rigamonti

Transcranial Doppler monitoring in subarachnoid hemorrhage: a critical tool in critical care.

Purpose: To review the literature regarding the use of transcranial Doppler ultrasonography (TCD) for monitoring cerebral vasospasm following subarachnoid hemorrhage (SAH).Source: We searched Medline (1980 to August 2007) and Embase (1980 to August 2007) and reviewed all relevant manuscripts regarding TCD and SAH.Principal findings: Currently, the gold standard for vasospasm diagnosis is cerebral angiography, replaceable by computed tomography angiography, only when angiography is not available. Obviously, it is not feasible to perform such investigation as frequently as bedside clinical assessment. Repeated clinical assessments of a patient’s neurological status carry the problem of detecting the clinical signs and symptoms of vasospasm, which occur only after vasospasm has already manifested its deleterious effects on the cerebral parenchyma. Transcranial Doppler ultrasonography is a relatively new, non-invasive tool, allowing for bedside monitoring to determine flow velocities indicative of changes in vascular calibre. Transcranial Doppler ultrasonography can be useful pre-, intra- and post-operatively, while helping to recognize the development of cerebral vasospasm before the onset of its clinical effects.Conclusion: Vasospasm following SAH is a very important source of morbidity and mortality. Too often, the first sign is a neurologic deficit, which may be too late to reverse. Transcranial Doppler ultrasonography assists in the clinical decision-making regarding further diagnostic evaluation and therapeutic interventions. When performed in isolation, the contribution of TCD to improving patient outcome has not been established. Nevertheless, TCD has become a regularly employed tool in neurocritical care and perioperative settings.RésuméObjectif: Passer en revue la littérature concernant l’utilisation de l’échographie Doppler transcrânienne (TCD) pour surveiller un vasospasme cérébral survenu à la suite d’une hémorragie sous-arachnoïdienne (SAH).Source: Nous avons effectué des recherches sur Medline (1980 à août 2007) et Embase (1980 à août 2007) et révisé tous les manuscrits pertinents concernant la TCD et la SAH.Constatations principales: À l’heure actuelle, l’angiographie est l’étalon or pour diagnostiquer un vasospasme. Celle-ci peut être remplacée par l’angiographie par tomodensitométrie seulement lorsqu’une angiographie n’est pas disponible. Il est évident qu’il n’est pas possible d’effectuer de telles recherches aussi fréquemment que les évaluations cliniques au chevet du malade. Des évaluations cliniques répétées de l’état neurologique d’un patient donné ont pour objectif primaire la détection des signes et symptômes cliniques du vasospasme, lesquels ne surviennent qu’après que le vasospasme a manifesté ses effets nuisibles sur le parenchyme cérébral. L’échographie Doppler transcrânienne est un outil relativement nouveau et non invasif qui permet un monitorage au chevet du patient afin de déterminer les vitesses du débit qui indiquent les changements dans le calibre vasculaire. L’échographie Doppler transcrânienne peut être utile avant, pendant et après l’opération tout en constituant un outil précieux pour identifier le développement d’un vasospasme cérébral avant que ses effets cliniques ne se manifestent.Conclusion: Le vasospasme à la suite d’une SAH est une cause majeure de morbidité et de mortalité. Trop souvent, le premier signe visible d’un vasospasme est un déficit neurologique, et il pourrait être trop tard déjà pour qu’il soit réversible. L’échographie Doppler transcrânienne est un outil qui assiste la prise de décision clinique concernant une évaluation diagnostique approfondie et des interventions thérapeutiques. Il n’a pas été démontré que la TCD, utilisée seule, améliore le suivi des patients. Cependant, la TCD est devenue un outil régulièrement employé dans des contextes de soins intensifs neurologiques et périopératoires.

Hemoglobin levels and transfusions in neurocritically ill patients: a systematic review of comparative studies

IntroductionAccumulating evidence suggests that, in critically ill patients, a lower hemoglobin transfusion threshold is safe. However, the optimal hemoglobin level and associated transfusion threshold remain unknown in neurocritically ill patients.MethodsWe conducted a systematic review of comparative studies (randomized and nonrandomized) to evaluate the effect of hemoglobin levels on mortality, neurologic function, intensive care unit (ICU) and hospital length of stay, duration of mechanical ventilation, and multiple organ failure in adult and pediatric neurocritically ill patients. We searched MEDLINE, The Cochrane Central Register of Controlled Trials, Embase, Web of Knowledge, and Google Scholar. Studies focusing on any neurocritical care conditions were included. Data are presented by using odds ratios for dichotomous outcomes and mean differences for continuous outcomes.ResultsAmong 4,310 retrieved records, six studies met inclusion criteria (n = 537). Four studies were conducted in traumatic brain injury (TBI), one in subarachnoid hemorrhage (SAH), and one in a mixed population of neurocritically ill patients. The minimal hemoglobin levels or transfusion thresholds ranged from 7 to 10 g/dl in the lower-Hb groups and from 9.3 to 11.5 g/dl in the higher-Hb groups. Three studies had a low risk of bias, and three had a high risk of bias. No effect was observed on mortality, duration of mechanical ventilation, or multiple organ failure. In studies reporting on length of stay (n = 4), one reported a significant shorter ICU stay (mean, -11.4 days (95% confidence interval, -16.1 to -6.7)), and one, a shorter hospital stay (mean, -5.7 days (-10.3 to -1.1)) in the lower-Hb groups, whereas the other two found no significant association.ConclusionsWe found insufficient evidence to confirm or refute a difference in effect between lower- and higher-Hb groups in neurocritically ill patients. Considering the lack of evidence regarding long-term neurologic functional outcomes and the high risk of bias of half the studies, no recommendation can be made regarding which hemoglobin level to target and which associated transfusion strategy (restrictive or liberal) to favor in neurocritically ill patients.

Anesthetic approach to high-risk patients and prolonged awake craniotomy using dexmedetomidine and scalp block.

Background: Awake craniotomy with intraoperative speech or motor testing is relatively contraindicated in cases requiring prolonged operative times and in patients with severe medical comorbidities including anxiety, anticipated difficult airway, obesity, large tumors, and intracranial hypertension. The anesthetic management of neurosurgical patients who possess these contraindications but would be optimally treated by an awake procedure remains unclear. Methods: We describe a new anesthetic approach for awake craniotomy that did not require any airway manipulation, utilizing a bupivacaine-based scalp nerve block, and dexmedetomidine as the primary hypnotic-sedative agent. Using this technique, we provided optimal operative conditions to perform awake craniotomy facilitating safe tumor resection, while utilizing intraoperative electrocorticography for motor and speech mapping in a cohort of 10 patients at a high risk for airway compromise and complications associated with patient comorbidities. Results: All patients underwent successful awake craniotomy, intraoperative mapping, and tumor resection with adequate sedation for up to 9 hours (median 3.5 h, range 3 to 9 h) without any loss of neurological function, airway competency, or the need to provide any active rescue airway management. We report 4 of these cases that highlight our experience: 1 case required prolonged surgery because of the complexity of tumor resection and 3 patients had important medical comorbidities and/or relative contraindication for an awake procedure. Conclusions: Dexmedetomidine, with concurrent scalp block, is an effective and safe anesthetic approach for awake craniotomy. Dexmedetomidine facilitates the extension procedure complexity and duration in patients who might traditionally not be considered to be candidates for this procedure.

Storage of strain-specific rat blood limits cerebral tissue oxygen delivery during acute fluid resuscitation

BACKGROUNDnThe effect of blood storage on tissue oxygen delivery has not been clearly defined. Some studies demonstrate reduced microvascular oxygen delivery, whereas others do not. We hypothesize that storage of rat blood will limit its ability to deliver oxygen to cerebral tissue.nnnMETHODSnAnaesthetized rats underwent haemorrhage (18 ml kg(-1)) and resuscitation with an equivalent amount of fresh or 7 day stored strain-specific whole blood. Arterial blood gases, co-oximetry, red cell counts and indices, and blood smears were performed. Hippocampal tissue oxygen tension (PBr(O2)), regional cerebral blood flow (rCBF), and mean arterial pressure (MAP) were measured before and for 60 min after resuscitation (n=6). Data [mean (SD)] were analysed by anova.nnnRESULTSnAfter 7 days, there was a significant reduction in pH, Pa(O2), an increase in Pa(CO2), but no detectable plasma haemoglobin in stored rat blood. Stored red blood cell morphology demonstrated marked echinocytosis, but no haemolysis in vitro. MAP and PBr(O2) in both groups decreased after haemorrhage. Resuscitation with stored blood returned MAP [92 (SD 16) mm Hg] and PBr(O2) [3.2 (0.7) kPa] to baseline, whereas rCBF remained stable [1.2 (0.1)]. Resuscitation with fresh blood returned MAP to baseline [105 (16) mm Hg] whereas both PBr(O2) [5.6 (1.5) kPa] and rCBF [1.9 (0.4)] increased significantly (P<0.05 for both, relative to baseline and stored blood group). There was no evidence of haemolysis in vivo.nnnCONCLUSIONSnAlthough resuscitation with stored blood restored cerebral oxygen delivery to baseline, fresh blood produced a greater increase in both PBr(O2) and rCBF. These data support the hypothesis that storage limits the ability of RBC to deliver oxygen to brain tissue.

The Impact of Red Blood Cell Transfusion on Cerebral Tissue Oxygen Saturation in Severe Traumatic Brain Injury

BackgroundThere are a range of opinions on the benefits and thresholds for the transfusion of red blood cells in critically ill patients with traumatic brain injury (TBI) and an urgent need to understand the neurophysiologic effects. The aim of this study was to examine the influence of red blood cell transfusions on cerebral tissue oxygenation (SctO2) in critically ill TBI patients.MethodsThis prospective observational study enrolled consecutive TBI patients with anemia requiring transfusion. Cerebral tissue oxygen saturation (SctO2) was measured noninvasively with bilateral frontal scalp probes using near-infrared spectroscopy (NIRS) technology. Data were collected at baseline and for 24xa0h after transfusion. The primary outcome was the applicability of a four-wavelength near-infrared spectrometer to monitor SctO2 changes during a transfusion. Secondary outcomes included the correlation of SctO2 with other relevant physiological variables, the dependence of SctO2 on baseline hemoglobin and transfusion, and the effect of red blood cell transfusion on fractional tissue oxygen extraction.ResultsWe enrolled 24 patients with severe TBI, of which five patients (21xa0%) were excluded due to poor SctO2 signal quality from large subdural hematomas and bifrontal decompressive craniectomies. Twenty transfusions were monitored in 19 patients. The mean pre- and post-transfusion hemoglobin concentrations were significantly different [74xa0g/L (SD 8xa0g/L) and 84xa0g/L (SD 9xa0g/L), respectively; p value <0.0001]. Post-transfusion SctO2 was not significantly greater than pre-transfusion SctO2 [left-side pre-transfusion 69xa0% (SD 7) vs. post-transfusion 70xa0% (SD 10); pxa0=xa00.68, and right-side pre-transfusion 69xa0% (SD 5) vs. post-transfusion 71xa0% (SD 7); pxa0=xa00.11]. In a multivariable mixed linear analysis, mean arterial pressure was the only variable significantly associated with a change in SctO2.ConclusionsThe bifrontal method of recording changes in NIRS signal was not able to detect a measurable impact on SctO2 in this sample of patients receiving red blood cell transfusion therapy in a narrow but conventionally relevant, range of anemia.

Prognostication in critically ill patients with severe traumatic brain injury: the TBI-Prognosis multicentre feasibility study

Objective Severe traumatic brain injury is a significant cause of morbidity and mortality in young adults. Assessing long-term neurological outcome after such injury is difficult and often characterised by uncertainty. The objective of this feasibility study was to establish the feasibility of conducting a large, multicentre prospective study to develop a prognostic model of long-term neurological outcome in critically ill patients with severe traumatic brain injury. Design A prospective cohort study. Setting 9 Canadian intensive care units enrolled patients suffering from acute severe traumatic brain injury. Clinical, biological, radiological and electrophysiological data were systematically collected during the first week in the intensive care unit. Mortality and functional outcome (Glasgow Outcome Scale extended) were assessed on hospital discharge, and then 3, 6 and 12u2005months following injury. Outcomes The compliance to protocolised test procedures was the primary outcome. Secondary outcomes were enrolment rate and compliance to follow-up. Results We successfully enrolled 50 patients over a 12-month period. Most patients were male (80%), with a median age of 45u2005years (IQR 29.0–60.0), a median Injury Severity Score of 38 (IQR 25–50) and a Glasgow Coma Scale of 6 (IQR 3–7). Mortality was 38% (19/50) and most deaths occurred following a decision to withdraw life-sustaining therapies (18/19). The main reasons for non-enrolment were the time window for inclusion being after regular working hours (35%, n=23) and oversight (24%, n=16). Compliance with protocolised test procedures ranged from 92% to 100% and enrolment rate was 43%. No patients were lost to follow-up at 6u2005months and 2 were at 12u2005months. Conclusions In this multicentre prospective feasibility study, we achieved feasibility objectives pertaining to compliance to test, enrolment and follow-up. We conclude that the TBI-Prognosis prospective multicentre study in severe traumatic brain injury patients in Canada is feasible.

Awake craniotomy using dexmedetomidine and scalp blocks: a retrospective cohort study

PurposeAnesthetic and surgical considerations for awake craniotomy (AC) include airway patency, patient comfort, and optimization of real-time brain mapping. The purpose of this study is to report our experience of using dexmedetomidine and scalp blocks, without airway intervention, as a means to facilitate and optimize intraoperative brain mapping and brain tumour resection during AC.MethodsWe conducted a retrospective cohort study of 55 patients who underwent AC from March 2012 to September 2016. The incidence of critical airway outcomes, perioperative complications, and successful intraoperative mapping was determined. The primary outcome was the incidence of a failed AC anesthetic technique as defined by the need to convert to general anesthesia with a secured airway prior to (or during) brain mapping and brain tumour resection. Secondary outcomes were the intraoperative incidence of: 1) altered surgical management due to information acquired through real-time brain mapping, 2) interventions to restore airway patency or rescue the airway, 3) hemodynamic instability (> 20% from baseline), 4) nausea and vomiting, 5) new onset neurologic deficits, and 6) seizure activity.ResultsThere were no anesthesia-related critical events and no patients required airway manipulation or conversion to a general anesthetic. Multimodal language, motor, and sensory assessment with direct cortical electrical stimulation was successfully performed in 100% of cases. In 24% (13/55) of patients, data acquired during intraoperative brain mapping influenced surgical decision-making regarding the extent of tumour resection. Nine (16%) patients had intraoperative seizures.ConclusionsDexmedetomidine-based anesthesia and scalp block facilitated AC surgery without any requirement for urgent airway intervention or unplanned conversion to a full general anesthetic. This approach can enable physiologic testing before and during tumour resection facilitating real-time surgical decision-making based on intraoperative brain mapping with patients awake thereby minimizing the risk of neurologic deficit and increasing the opportunity for optimal surgical resection.RésuméObjectifLes considérations anesthésiques et chirurgicales faisant envisager une craniotomie sur patient éveillé (CE) sont notamment la perméabilité des voies aériennes, le confort du patient et l’optimisation de la cartographie cérébrale en temps réel. L’objectif de cette étude est de rapporter notre expérience de l’utilisation de la dexmédétomidine et des blocs des nerfs du scalp, sans intervention sur les voies aériennes, afin de faciliter et d’optimiser la cartographie cérébrale peropératoire et la résection de tumeurs cérébrales au cours d’une CE.MéthodesNous avons mené une étude de cohorte rétrospective sur 55xa0patients ayant subi une CE entre marsxa02012 et septembrexa02016. L’incidence des événements critiques sur les voies aériennes, des complications périopératoires et des succès de la cartographie cérébrale peropératoire a été déterminée. Le critère d’évaluation principal était l’incidence de l’échec de la technique anesthésique par CE, défini par la nécessité de la convertir en anesthésie générale avec sécurisation des voies aériennes avant (ou pendant) la cartographie cérébrale et la résection de la tumeur. Les critères d’évaluation secondaires étaient des mesures de la survenue peropératoire des événements suivantsxa0: 1) modification de la gestion chirurgicale en raison d’informations acquises au cours de la cartographie cérébrale en temps réel, 2) interventions visant à restaurer la perméabilité des voies aériennes ou libérer l’accès aux voies aériennes, 3) instabilité hémodynamique (>xa020xa0% par rapport à l’inclusion), 4) nausées et vomissements, 5) apparition de nouveaux déficits neurologiques, et 6) convulsion.RésultatsIl n’y a pas eu d’événements critiques liés à l’anesthésie et aucun patient n’a nécessité d’intervention sur les voies aériennes ou de conversion à une anesthésie générale. Une évaluation multimodale du langage, de la motricité et de la sensibilité avec stimulation électrique corticale a été réalisée avec succès dans 100xa0% des cas. Chez 24xa0% des patients (13/55), les données acquises au cours de la cartographie cérébrale peropératoire ont influencé la prise de décision concernant l’étendue de la résection tumorale. Neuf patients (16xa0%) ont présenté des convulsions peropératoires.ConclusionsL’anesthésie basée sur la dexmédétomidine et le bloc des nerfs du scalp a facilité l’intervention de CE sans nécessiter aucune intervention urgente sur les voies aériennes ou conversion non prévue en anesthésie généralisée complète. Cette approche autorise la réalisation de tests physiologiques avant et pendant la résection de la tumeur, facilitant la prise de décision chirurgicale en temps réel basée sur la cartographie cérébrale peropératoire chez des patients éveillés, minimisant ainsi le risque de déficit neurologique et augmentant les chances de résection chirurgicale optimale.

Transcranial Doppler and Transcranial Color-Coded Duplex Sonography

Transcranial Doppler (TCD) is a safe, noninvasive, bed-side technique for the measurement of cerebral arteries blood flow velocity, and it is commonly used in standard care of neurocritical care patients. TCD-derived indices, including flow velocities and pulsatility index, allow to assess cerebrovascular dynamics and to calculate secondary indices including noninvasive intracranial pressure, cerebral perfusion pressure, vasospasm, and cerebral autoregulation, which can facilitate clinical management of cerebral pathologies.