[Acute myocardial infarction as an incidental finding: reflections on the preanesthesia evaluation]. / Infarto agudo de miocardio como hallazgo casual: consideraciones sobre la evaluación preanestésica.

A preoperative electrocardiogram in a 16-year-old boy scheduled for surgery for a fractured radius and mandibular condyle after a motorcycle accident showed signs of myocardial ischemia as an incidental finding. Coronary arteriography revealed complete occlusion of the anterior descending artery, confirming a diagnosis of acute coronary syndrome with ST elevation, with no myocardial viability. As the patient's general condition was acceptable, to prevent severe functional sequelae, surgery was rescheduled for 17 days later. An axillary block was well tolerated at that time. While indiscriminate ordering of preoperative tests is not recommended in the literature, such testing continues to be practiced in many hospitals, possibly for reasons of organization and legal cover. In our case, the electrocardiogram made it possible to diagnose a severe lesion and adjust the anesthetic technique to suit this situation, thereby possibly preventing devastating consequences. We recommend performing an electrocardiogram on all patients with suspected blunt chest trauma, regardless of the severity of the lesions, particularly in patients scheduled for surgery.

Infarto agudo de miocardio como hallazgo casual: consideraciones sobre la evaluación preanestésica / Acute myocardial infarction as answer finding: reflections on the preanesthesia evaluation

Un varón de 16 años, propuesto para cirugía por fracturade radio y cóndilo mandibular tras caída de motopresentó, en el electrocardiograma preoperatorio, signosde isquemia miocárdica como hallazgo casual. La coronariografíadetectó una obstrucción completa de la ramadescendente anterior y se confirmó el diagnóstico de síndromecoronario agudo con elevación de ST, sin viabilidadmiocárdica. Dado que el paciente mantenía un aceptableestado general, y con el fin de evitar secuelasfuncionales graves, se intervino en el 17º día de evolución,bajo bloqueo axilar, con buena tolerancia.Aunque la solicitud indiscriminada de pruebas preoperatoriasno está recomendada por la literatura médica,se sigue realizando en muchos centros, posiblementepor motivos organizativos y de cobertura legal. En elcaso presentado, el electrocardiograma permitió el diagnósticode una lesión grave y el ajuste de la técnica anestésicaa esta condición, lo que posiblemente evitó consecuenciasdevastadoras.Como conclusión, se sugiere la conveniencia de realizarun control electrocardiográfico a cualquier pacientecon sospecha de haber sufrido un traumatismo torácicocerrado, independientemente de la gravedad de las lesiones,especialmente si va a ser sometido a intervenciónquirúrgica(AU)

A preoperative electrocardiogram in a 16-year-oldboy scheduled for surgery for a fractured radius andmandibular condyle after a motorcycle accident showedsigns of myocardial ischemia as an incidental finding.Coronary arteriography revealed complete occlusion ofthe anterior descending artery, confirming a diagnosis ofacute coronary syndrome with ST elevation, with nomyocardial viability. As the patient’s general conditionwas acceptable, to prevent severe functional sequelae,surgery was rescheduled for 17 days later. An axillaryblock was well tolerated at that time. Whileindiscriminate ordering of preoperative tests is notrecommended in the literature, such testing continues tobe practiced in many hospitals, possibly for reasons oforganization and legal cover. In our case, theelectrocardiogram made it possible to diagnose a severelesion and adjust the anesthetic technique to suit thissituation, thereby possibly preventing devastatingconsequences. We recommend performing anelectrocardiogram on all patients with suspected bluntchest trauma, regardless of the severity of the lesions,particularly in patients scheduled for surgery(AU)

Cerebral hemodynamic changes during sustained hypocapnia in severe head injury: can hyperventilation cause cerebral ischemia?

Hyperventilation (HV) is routinely used in the management of increased intracranial pressure (ICP) in severe head injury. However, this treatment continues to be controversial because it has been reported that long-lasting reduced cerebral blood flow (CBF) due to profound sustained hypocapnia may contribute to the development or deterioration of ischemic lesions. Our goal in this study was to analyze the effects of sustained hyperventilation on cerebral hemodynamics (CBF, ICP) and metabolism (arterio jugular differences of lactates = AVDL). CO2-reactivity and CBF was estimated using AVDO2 (arteriojugular differences of oxygen content). Global cerebral ischemia and increased anaerobic metabolism were considered according to AVDO2 and AVDL respectively. Thirty-three patients with severe and moderate head injury and increased ICP were included. Within 72 hours after accident, patients were hyperventilated for a period of 4 hours. During this time jugular oxygen saturation (SjO2), arterial oxygen saturation (SaO2), ICP, mean arterial blood pressure (MABP), AVDO2 and AVDL were recorded. In our study, most patients preserved CO2-reactivity (88.2%). In these cases HV was very effective in lowering ICP. Our findings showed that this reduction was due to a CBF decrease. According to basal AVDO2 twenty-five patients (75.7%) were considered as hyperemic and eight (24.2%) as not hyperemic. Global ischemia and increased anaerobic metabolism were detected in one case in the non-hyperemic group. According to AVDO2 and AVDL, no adverse effects were found during four hours of HV in hyperemic patients. Nevertheless, AVDO2 and AVDL are global measurements and might not detect regional ischemia surrounding focal lesions such as contusions and haematomas. We suggest that monitoring of AVDO2 or other haemometabolic variables should be mandatory when sustained HV is used in the management of head injury patients.

Effects on intracranial pressure of fentanyl in severe head injured patients.

Despite opioids are routinely used for analgesia in head injured patients, the effects of such drugs on ICP and cerebral hemodynamics remain controversial. Cerebrovascular autoregulation (CAR) could be an important factor in the ICP increases reported after opioid administration. In order to describe the effects on intracranial pressure of fentanyl and correlated such effects with autoregulation status, we studied 30 consecutive severe head injury patients who received fentanyl (2 micrograms/kg) intravenously over one minute. Prior to study, CAR was assessed. Monitoring included MAP, HR, SaO2, ETCO2, SjO2 and ICP. Changes in cerebral blood flow (CBF) were estimated from relative changes in AVDO2. Patients mean GCS was 5.7 +/- 1.7 (mean +/- STD) and mean ICP on admission was 23.8 +/- 16.3 mmHg. Fentanyl caused significant increases in ICP and decreases in MAP and CPP, but CBF remained unchanged when estimated by AVDO2. In patients with preserved CAR (34.5%), opioid-induced ICP increase was greater (but not statistically significant) than in those with impaired CAR (65.5%). We conclude than fentanyl moderately increased ICP and decreased MAP and CPP. Our data suggests that in patients with preserved CAR, potent opioids could cause greater increases of ICP, probably due to activation of the vasodilatadory cascade.

Arterio-jugular differences of oxygen (AVDO2) for bedside assessment of CO2-reactivity and autoregulation in the acute phase of severe head injury.

Autoregulation and CO2-reactivity can be impaired independently of each other in many brain insults, the so-called 'dissociated vasoparalysis'. The theoretical combination of preserved CO2-reactivity and impaired or abolished autoregulation can have many clinical implications in the daily management of brain injured patients. To optimize their treatment, a bedside assessment of autoregulation and CO2-reactivity is desirable. When cerebral metabolic rate of oxygen is constant, changes in arterio-jugular differences of oxygen (AVDO2) reflect changes in CBF. In these situations relative changes in AVDO2 can be viewed as inverse changes in CBF and used as an evaluation method of CO2-reactivity and autoregulation. In 39 consecutive severe head injury patients with a mean age of 28 +/- 17 years and a diffuse brain injury, cerebrovascular response to changes in pCO2 was tested in the acute phase after injury (18 +/- 8 hours). In 28 of those cases autoregulation was also assessed. A relative CBF value (1/AVDO2) was calculated from baseline AVDO2 and was expressed as 100%. Changes in 1/AVDO2 after inducing pCO2 changes give a good estimate of changes in global CBF. Two different indexes were calculated for CO2-reactivity: 1) absolute CO2-reactivity (CO2RABS) and 2) percentage reactivity (CO2R%). CO2R% was used to separate patients with impaired/abolished CO2-reactivity from those with preserved CO2-reactivity. Patients with CO2R% above 1% were considered in the intact CO2-reactivity group and patients in whom CO2R% was below or equal to 1% were included in the impaired/abolished CO2-reactivity group. Only five cases (12.8%) presented an impaired/abolished CO2-reactivity. AVDO2 response to induced hypertension was studied in a subset of 28 patients. Phenylephrine was used to increase MABP about 25%. All AVDO2 values were corrected for changes in pCO2. Patients with changes in 1/AVDO2 less than or equal to 20% were included in the intact autoregulation group. Patients with estimated CBF changes above 20% were classified as having an impaired autoregulation (impaired/abolished). In 12 patients (43%) autoregulation was intact. In the remaining 16 patients (57%) autoregulation was imparied. Of the 28 cases, CO2-reactivity was impaired in only five cases. All patients with an impaired CO2-reactivity also had an impaired autoregulation. Monitoring relative changes in AVDO2 permits a reliable study of CO2-reactivity and autoregulation at the bedside. Introducing these variables into the day-to-day management should be considered in treatment protocols.