Adrian W. Gelb

Cardiovascular effects of human insular cortex stimulation

Recent investigations indicate a site of cardiac representation within the left insular cortex of the rat. Moreover, the results of lesion studies suggest left-sided insular dominance for sympathetic cardiovascular effects. It is unclear whether similar representation exists within the human insular cortex. Five epileptic patients underwent intraoperative insular stimulation prior to temporal lobectomy for seizure control. On stimulation of the left insular cortex, bradycardia and depressor responses were more frequently produced than tachycardia and pressor effects (p < 0.005). The converse applied for the right insular cortex. We believe this to be the first demonstration of cardiovascular changes elicitable during insular stimulation in humans, and of lateralization of such responses for a cortical site. In humans, unlike the rat, there appears to be right-sided dominance for sympathetic effects. These findings may be of relevance in predicting the autonomie effects of stroke in humans and in the explanation of sudden unexpected epileptic death.

Myocardial Infarction after Noncardiac Surgery

Background In this study, the authors intensively monitored isoenzyme and electric activity of the heart for the first 7 days after noncardiac surgery in a large group of patients at risk for postoperative myocardial infarction (PMI). Methods After institutional review board approval and written informed consent were received, 323 patients, aged 50 yr or older, who had ischemic heart disease and presented for noncardiac surgery, were enrolled in this prospective, blinded study. After operation, patients had daily clinical assessments, electrocardiograms, and measurements of creatine kinase (CK), CK‐2 (mass and activity), and Troponin‐T on the operative night, twice daily on postoperative days 1–4, and then daily on days 5–7. A diagnosis of PMI was made if the total CK was > 174 U/l and in the presence of two of the following: (1) CK‐2/CK (mass or activity) > 5%, (2) new Q waves lasting >or= to 0.04 s and 1 mm deep in at least two contiguous leads, (3) Troponin‐T was > 0.2 micro gram/l, or (4) a positive result of pyrophosphate scan. Results Eighteen of the 323 patients (5.6%) had a PMI, of which 3 (17%) were fatal. Only 3 of 18 patients had chest pain, whereas 10 of 18 patients (56%) had other clinical findings. The electrocardiographic classification of the PMI was Q wave in 6, non‐Q wave in 10, and indeterminate in 2. The PMIs occurred on the day of operation in 8, on day one in 6, on day two in 3, and on day four in 1 patient. Conclusions This study determined that PMI was an early event, only occasionally associated with chest pain, and usually non‐Q wave in nature.

Mild Hypothermia as a Protective Therapy during Intracranial Aneurysm Surgery: A Randomized Prospective Pilot Trial

OBJECTIVE To conduct a pilot trial of mild intraoperative hypothermia during cerebral aneurysm surgery. METHODS One hundred fourteen patients undergoing cerebral aneurysm clipping with (n = 52) (World Federation of Neurological Surgeons score < or =III) and without (n = 62) acute aneurysmal subarachnoid hemorrhage (SAH) were randomized to normothermic (target esophageal temperature at clip application of 36.5 degrees C) and hypothermic (target temperature of 33.5 degrees C) groups. Neurological status was prospectively evaluated before surgery, 24 and 72 hours postoperatively (National Institutes of Health Stroke Scale), and 3 to 6 months after surgery (Glasgow Outcome Scale). Secondary outcomes included postoperative critical care requirements, respiratory and cardiovascular complications, duration of hospitalization, and discharge disposition. RESULTS Seven hypothermic patients (12%) could not be cooled to within 1 degrees C of target temperature; three of the seven were obese. Patients randomized to the hypothermic group more frequently required intubation and rewarming for the first 2 hours after surgery. Although not achieving statistical significance, patients with SAH randomized to the hypothermic group, when compared with patients in the normothermic group, had the following: 1) a lower frequency of neurological deterioration at 24 and 72 hours after surgery (21 versus 37-41%), 2) a greater frequency of discharge to home (75 versus 57%), and 3) a greater incidence of good long-term outcomes (71 versus 57%). For patients without acute SAH, there were no outcome differences between the temperature groups. There was no suggestion that hypothermia was associated with excess morbidity or mortality. CONCLUSION Mild hypothermia during cerebral aneurysm surgery is feasible in nonobese patients and is well tolerated. Our results indicate that a multicenter trial enrolling 300 to 900 patients with acute aneurysmal SAH will be required to demonstrate a statistically significant benefit with mild intraoperative hypothermia.

Preoperative anxiety: detection and contributing factors

The purpose of this study was to determine whether there is a correlation between anxiety the night before surgery and that existing immediately preoperatively, whether anaesthetists can detect preoperative anxiety and to establish the presence of any factors that might assist in the determination of preoperative anxiety. Anxiety was measured objectively using the Spielberger State-Trait Anxiety Inventory (STAI), and the Multiple Affect Adjective Check List (MAACL). Anxiety was found to be higher infemales and those not having had a previous anaesthetic, and to remain constant from the afternoon before surgery to the immediate preoperative period. Anaesthetists were found to be poor assessors of anxiety unless they specifically questioned their patients about this.RésuméLe but de cette étude est de déterminer s’il existe une corrélation entre l’anxiété la veille de la chirurgie et celle existant immédiatement en période préopératoire, si les anesthésistes peuvent détecter l’anxiété préopératoire et établir la présence de facteurs qui peuvent assister à la détermination de cette anxiété. L’anxiété a été mesurée objectivement par le test de «Spielberger State-Trait Anxiety Inventory (STAJ)»et le «Multiple Affect Adjective Check List (MAACL)». L’anxiété fut trouvée supérieure chez les femmes ainsi que chez ceux qui n’ont pas eu d’anesthésie au préalable et fut trouvée constante à partir de l’après midi avant la chirurgie à la période préopératoire immédiate. Les anesthésistes furent trouvés comme des pauvres évaluateurs de l’anxiété sauf quand celle-ci fut exprimée par les patients lors du questionnaire.

Cervical spine motion: a fluoroscopic comparison during intubation with lighted stylet, GlideScope, and Macintosh laryngoscope.

The question of which is the optimum technique to intubate the trachea in a patient who may have a cervical(C)-spine injury remains unresolved. We compared, using fluoroscopic video, C-spine motion during intubation for Macintosh 3 blade, GlideScope®, and Intubating Lighted Stylet, popularly known as the Lightwand or Trachlight®. Thirty-six healthy patients were randomized to participate in a crossover trial of either Lightwand or GlideScope to Macintosh laryngoscopy, with in-line stabilization. C-spine motion was examined at the Occiput-C1 junction, C1-2 junction, C2-5 motion segment, and C5-thoracic motion segment during manual ventilation via bag-mask, laryngoscopy, and intubation. Time to intubate was also measured. C-spine motion during bag-mask ventilation was 82% less at the four motion segments studied than during Macintosh laryngoscopy (P < 0.001). C-spine motion using the Lightwand was less than during Macintosh laryngoscopy, averaging 57% less at the four motion segments studied (P < 0.03). There was no significant difference in time to intubate between the Lightwand and the Macintosh blade. C-spine motion was reduced 50% at the C2-5 segment using the GlideScope (P < 0.04) but unchanged at the other segments. Laryngoscopy with GlideScope took 62% longer than with the Macintosh blade (P < 0.01). Thus, the Lightwand (Intubating Lighted Stylet) is associated with reduced C-spine movement during endotracheal intubation compared with the Macintosh laryngoscope.

Continuous lidocaine infusion and focal feline cerebral ischemia.

We measured somatosensory evoked potentials, infarct size, and cerebral blood flow in 20 cats subjected to occlusion of the middle cerebral artery for 3 hours, followed by an equal period of reperfusion. The cats were randomized into a treatment group that received a continuous infusion of 2 mg/kg lidocaine hydrochloride or a control group that received an equivalent volume of normal saline. All 10 treated cats retained measurable evoked potentials throughout the experiment. In five control cats, evoked potentials disappeared completely at some point during the occlusion (difference between groups significant at p less than 0.001). Mean amplitude of the major cortical wave in the nine treated cats with cerebral infarcts was higher than that of the nine corresponding controls (p less than 0.05). Lidocaine reduced the mean +/- SEM size of the infarcts from 30.1 +/- 6.0% in the control group to 14.7 +/- 4.9% in the treated group (p less than 0.05). As blood flow was reduced in the infarct and peri-infarct zones in the control but not the treated cats, our results suggest that the beneficial effects of lidocaine may be due to preservation of blood flow in the ischemic zone.

Comparison of the Bullard and Macintosh Laryngoscopes for Endotracheal Intubation of Patients with a Potential Cervical Spine Injury

Background: In the emergency trauma situation, in‐line stabilization (ILS) of the cervical spine is used to reduce head and neck extension during laryngoscopy. The Bullard laryngoscope may result in less cervical spine movement than the Macintosh laryngoscope. The aim of this study was to compare cervical spine extension (measured radiographically) and time to intubation with the Bullard and Macintosh laryngoscopes during a simulated emergency with cervical spine precautions taken. Methods: Twenty‐nine patients requiring general anesthesia and endotracheal intubation were studied. Patients were placed on a rigid board and anesthesia was induced. Laryngoscopy was performed on four occasions: with the Bullard and Macintosh laryngoscope both with and without manual ILS. Cricoid pressure was applied with ILS. To determine cervical spine extension, radiographs were exposed before and during laryngoscopy. Times to intubation and grade view of the larynx were also compared. Results: Cervical spine extension (occiput‐C5) was greatest with the Macintosh laryngoscope (25.9 [degree sign] +/‐ 2.8 [degree sign]). Extension was reduced when using the Macintosh laryngoscope with ILS (12.9 +/‐ 2.1 [degree sign]) and the Bullard laryngoscope without stabilization (12.6 +/‐ 1.8 [degree sign]; P < 0.05). Times to intubation were similar for the Macintosh laryngoscope with ILS (20.3 +/‐ 12.8 s) and for the Bullard without ILS (25.6 +/‐ 10.4 s). Manual ILS with the Bullard laryngoscope results in further reduction in cervical spine extension (5.6 +/‐ 1.5 [degree sign]) but prolongs time to intubation (40.3 +/‐ 19.5 s; P < 0.05). Conclusions: Cervical spine extension and time to intubation are similar for the Macintosh laryngoscope with ILS and the Bullard laryngoscope without ILS. However, time to intubation is significantly prolonged when the Bullard laryngoscope is used in a simulated emergency with cervical spine precautions taken. This suggests that the Bullard laryngoscope may be a useful adjunct to intubation of patients with potential cervical spine injury when time to intubation is not critical.

Isoflurane for refractory status epilepticus: a clinical series

General anesthesia has been recommended to control convulsive status epilepticus that is refractory to conventional anticonvulsant therapy. Halothane has been the recommended agent, but without experimental justification. Isoflurane, which has no reported organ toxicity and produces electrographic suppression at clinically useful concentrations in normal humans, should be a better volatile anesthetic for this purpose. The efficacy and safety of isoflurane administered to control convulsive status epilepticus were assessed on 11 occasions in nine patients in seven North American hospitals. Isoflurane, administered for 1-55 h, stopped seizures in all patients and was able to be titrated to produce burst-suppression patterns on electroencephalograms. Blood pressure support with iv fluids and/or pressor infusions was required in all of the patients. Seizures resumed upon discontinuation of isoflurane on eight of 11 occasions. Six of the nine patients died. The three survivors sustained cognitive deficits. In one patient urine fluoride concentrations were elevated, although not to nephrotoxic levels. These cases suggest that isoflurane 1) is an effective, rapidly titratable anticonvulsant; 2) does not reverse underlying causes of the refractory seizures; and 3) usually necessitates hemodynamic support with fluids and/or pressors. Isoflurane may be administered for seizures, but only when iv agents in anesthetic doses are ineffective or produce unacceptable side effects.

Perfusion Mapping Using Computed Tomography Allows Accurate Prediction of Cerebral Infarction in Experimental Brain Ischemia

Background and Purpose— We have developed a dynamic CT method to measure absolute cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). In this study we evaluated the ability of CT-derived functional maps to detect infarction in a rabbit model of focal cerebral ischemia. Methods— Sequential dynamic CT studies were performed at 2 different slices in 5 control rabbits and another 8 after induction of focal cerebral ischemia. The size of critically ischemic tissue was correlated to size of infarction measured by postmortem 2,3,5-triphenyltetrazolium chloride staining. In the control rabbits, short-term variability of the parameters was assessed by ANOVA analysis. Results— In 7 of 8 animals of the ischemia group, cerebral infarction was visible on 2,3,5-triphenyltetrazolium chloride staining, constituting 16.7±10.6% of the ipsilateral hemisphere. Good agreement of CBF functional maps with tissue specimens was found with respect to size and location of infarction. Best prediction of infarction was found for thresholds of CBF <10 mL/100 g per minute (mean size, 17.5±13.4%;r =0.95) and MTT >6 seconds (mean size, 15.6±13.5%;r =0.85), with regression slopes close to unity. CBV maps were less predictive of occurrence of infarction, especially in cases of small infarction. The short-term variability of CBF, CBV, and MTT in the control group was 10.9%, 15.2%, and 19.9%, respectively. Conclusions— Functional CT measurements of absolute CBF and MTT early after onset of ischemia allow prediction of the size and location of cerebral infarction with good accuracy.

Free radicals, antioxidants, and neurologic injury: possible relationship to cerebral protection by anesthetics.

Oxygen-centered free radicals cause brain injury associated with trauma and stroke. These reactive oxygen species may be detoxified by endogenous antioxidants, but cell death occurs after antioxidants become depleted. General anesthetics penetrate into brain parenchyma, where they may abrogate oxidative injury to neurons by several mechanisms that prevent the initiation of free radical chain reactions or terminate the propagation of highly reactive radicals. First, general anesthetics may inhibit free radical generation because these drugs slow cerebral utilization of oxygen and glucose, inhibit oxidative metabolism in neutrophils, and prevent redox changes in hemoglobin. Second, antioxidant anesthetics, such as thiopental and propofol, directly scavenge reactive oxygen species and inhibit lipid peroxidation. Finally, anesthetics may prevent the elevation of extracellular glutamate concentration and inhibit the activation of excitatory glutamatergic receptors that augment oxidative stress after ischemia.