Anestesia para el Tratamiento Quirúrgico de Aneurismas Cerebrales / Anesthesia for the surgical treatment of cerebral aneurysms

Although most cerebral aneurysms are asymptomatic and discovered incidentally, their rupture often results in significant morbidity and mortality. The anesthesiologist may become involved in surgical clipping of aneurysms either before aneurysm rupture or after subarachnoid hemorrhage. After subarachnoid hemorrhage, a multisystemic preoperative evaluation is mandatory because both neurological complications (elevated intracranial pressure, rebleeding, hydrocephalus, vasospasm) and non-neurological complications (respiratory insufficiency, cardiac dysfunction, electrolyte abnormalities, endocrine disturbances) might influence anesthetic management. Besides being prepared for potential sudden profuse bleeding, the anesthesiologist caring for craniotomy for aneurysm clipping should follow four main principles. First, acute increase in the aneurysm transmural gradient (mean arterial pressure minus intracranial pressure) should be avoided to prevent rupture or rebleeding. Second, the cerebral perfusion pressure should be maintained with euvolemia and vasopressors to avoid brain ischemia caused either by brain retractors or temporary clipping of the feeding vessel. Third, surgical exposure should be optimized by providing brain relaxation with normal cerebral oxygenation, normal ventilation or transient hyperventilation, appropriate anesthetic choice, mannitol and perhaps lasix, and occasionally cerebrospinal fluid drainage. Fourth, early emergence is favored to allow recognition of potentially reversible complications. By being vigilant and achieving these goals, the anesthesiologist will contribute to optimal patient outcomes. The following article provides information to guide the anesthesiologist in optimal management of surgical clipping of aneurysms.

A pesar de que la mayoría de los aneurismas cerebrales son asintomáticos y se describen incidentalmente, su ruptura suele resultar en una morbilidad y mortalidad significativas Por lo tanto, el anestesiólogo pudiera intervenir realizando un clipaje quirúrgico del aneurisma, bien sea de manera electiva o posterior a una hemorragia subaracnoidea. Luego de una hemorragia subaracnoidea es indispensable hacer una evaluación preoperatoria sistémica porque el manejo anestésico puede verse afectado tanto por las complicaciones neurológicas (presión intracraneal elevada, repetición de la hemorragia, hidrocefalia, vasoespasmo) y complicaciones no neurológicas (insuficiencia respiratoria, disfunción cardíaca, anomalías electrolíticas, alteraciones endocrinas). Además de estar preparado para una hemorragia profusa súbita, el anestesiólogo a cargo de una craneotomía para clipaje de un aneurisma debe adherirse a cuatro principios fundamentales. Primero, debe evitarse el incremento agudo en el gradiente transmural del aneurisma (presión arterial media menos la presión intracraneal) para impedir una ruptura o recurrencia de hemorragia. Segundo, la presión de perfusión cerebral debe mantenerse con euvolemia y vasopresores para evitar isquemia cerebral, bien sea con separadores cerebrales o clipaje temporal del vaso nutriente. Tercero, debe optimizarse la exposición quirúrgica con relajación cerebral mediante oxigenación y ventilación cerebral normal, selección apropiada del anestésico, manitol y tal vez lasix, drenaje de líquido cefalorraquídeo o hiperventilación transitoria. Cuarto, se recomienda el despertar temprano de la anestesia para reconocer precozmente las complicaciones potencialmente reversibles. Siendo vigilantes y logrando estas metas, el anestesiólogo contribuirá al logro de desenlaces óptimos para el paciente. El siguiente artículo ofrece información para orientar al anestesiólogo para el óptimo manejo del clipaje quirúrgico de aneurismas.

Complications of single-injection ultrasound-guided infraclavicular block: a cohort study.

INTRODUCTION: In recent studies on ultrasound-guided infraclavicular block (ICB), the authors have favoured a single injection posterior to the axillary artery rather than multiple injections; however, procedural complications and success rates associated with single-injection ultrasound-guided ICB are not well known. We undertook an observational study to evaluate the success rates of experienced and non-experienced operators performing ICBs and to identify the complications associated with ultrasound-guided single-injection ICB. METHODS: We conducted an observational cohort study of all ultrasound-guided single-injection ICBs performed over a two-year period (2008-2010). We identified the subjects for our study using a local database and excluded patients younger than 18 yr and those who received a continuous ICB. Complications (non-neurological and neurological) and ICB success rates were the primary and secondary end points, respectively. We collected the following data from patients' charts: patient demographics, types of complications and their respective frequencies, and the experience of the clinician performing the ICBs, and we identified potential late complications by telephone interview. Using a seven-point Likert scale, two experts in regional anesthesia evaluated the likelihood of a relationship between the identified neurological signs or symptoms and the ICB. A neurologist then evaluated the complications identified as being potentially related to the ICB. Summary data were collated, and 95% confidence intervals (CI) were calculated. RESULTS: We reviewed 627 ICB procedures, and 496 (79%) patients received telephone interviews. Most patients were males who had undergone either plastic or orthopedic surgery. Mepivacaine 1.5% was used in 96% of cases with a median volume of 30 mL [interquartile range 30-38]. We identified 131 cases of neurological signs or symptoms. Four cases were retained as possible links to the ICB, but they underwent complete resolution of symptoms at the time of evaluation. Two possible cases of local anesthetic toxicity were observed. There was a 93% success rate (95% CI 91 to 95) and the results were comparable between the experienced and the non-experienced operators (94% vs 93%, respectively). DISCUSSION: We observed few complications associated with a single-injection ultrasound-guided ICB and a high success rate regardless of the operator's expertise. The technique appears to be reliable, easy to perform, and safe.