Rosemary A. Craen

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.

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.

Quantitative assessment of cerebral hemodynamics using CT : Stability, accuracy, and precision studies in dogs

PURPOSE The limited clinical availability of currently used methods to measure regional cerebral blood volume (CBV) and cerebral blood flow (CBF) represents an important restriction. We undertook this study to evaluate a new dynamic CT method to measure CBV and CBF in normal and ischemic tissue. METHOD A total of 21 dynamic CT studies were performed in seven male beagles. The contrast enhancement curves of the carotid arteries and of various brain regions were deconvolved to obtain CBV and CBF. The stability of the deconvolution method employed was assessed by comparing three data sets obtained by analyses of one, two, and four regions of interest (ROIs), all covering the entire brain area. The accuracy of CT-derived CBF was analyzed for normal (n = 5 studies) and ischemic (n = 7 studies) brain tissue using fluorescent microspheres. Repetitive CT studies were performed to evaluate the precision of the CT measurements. RESULTS The stability of the deconvolution method was high with variabilities of 2.3% (CBV), 5.9% (CBF), and 8.9% (mean transit time), respectively. The correlation between the CT and the microsphere measurements was good for both normal and ischemia studies (r > 0.78, slope > 0.9). The variability of the CT CBF (30.6%) was higher than that of the CT CBV (12.3%) measurements. CONCLUSION Our novel dynamic CT method is stable with respect to the sizes of ROIs used, allowing for accurate measurements of CBV and CBF in both normal and ischemic tissue. Further studies are necessary to evaluate the variability of this method under controlled physiologic conditions.

Propofol sedation during awake craniotomy for seizures: patient-controlled administration versus neurolept analgesia.

This prospective study evaluated the safety and efficacy of patient-controlled sedation (PCS) using propofol during awake seizure surgery performed under bupivacaine scalp blocks. Thirty-seven patients were randomized to receive either propofol PCS combined with a basal infusion of propofol (n = 20) or neurolept analgesia using an initial bolus dose of fentanyl and droperidol followed by a fentanyl infusion (n = 17). Both groups received supplemental fentanyl and dimenhydrinate for intraoperative pain and nausea, respectively. Comparisons were made between groups for sedation, memory, and cognitive function, patient satisfaction, and incidence of complications. Levels of intraoperative sedation and patient satisfaction were similar between groups. Memory and cognitive function were well preserved in both groups. The incidence of transient episodes of ventilatory rate depression (<8 bpm) was more frequent among the propofol patients (5 vs 0, P = 0.04), particularly after supplemental doses of opioid. Intraoperative seizures were more common among the neurolept patients (7 vs 0, P = 0.002). PCS using propofol represents an effective alternative to neurolept analgesia during awake seizure surgery performed in a monitored care environment. (Anesth Analg 1997;84:1285-91)

Propofol sedation during awake craniotomy for seizures: electrocorticographic and epileptogenic effects.

This prospective study evaluated the effects of propofol sedation on the incidence of intraoperative seizures and the adequacy of electrocorticographic (ECoG) recordings during awake craniotomy performed for the management of refractory epilepsy.Thirty patients scheduled for temporal or frontal lobectomy for epilepsy under bupivacaine scalp block were randomized to receive patient-controlled propofol sedation (PCS) combined with a basal infusion of propofol (n = 15) or neurolept analgesia using an initial bolus dose of fentanyl (0.7 micro g/kg) and droperidol (0.04 mg/kg) followed by a fentanyl infusion (n = 15). Propofol administration was suspended 15 min before ECoG recording in the PCS group. The occurrence of inappropriate intraoperative seizures was noted and, based on blind review, the adequacy of ECoG recordings was compared. A higher incidence of intraoperative seizures was noted among the neurolept patients (6 vs 0, P = 0.008). Intraoperatively, ECoG recordings were adequate to proceed with resection in both groups. Evidence of low spike activity on ECoG did not correlate with the type of sedation administered. Higher frequency background ECoG activity was noted among patients who received propofol, but this did not interfere with ECoG interpretation. The use of propofol sedation does not appear to interfere with ECoG during epilepsy surgery, provided administration is suspended at least 15 min before recording. (Anesth Analg 1997;84:1280-4)

Does hyperventilation improve operating condition during supratentorial craniotomy? A multicenter randomized crossover trial.

BACKGROUND:Hyperventilation has been an integral, but poorly validated part of neuroanesthetic practice. We conducted a two-period, crossover, randomized trial to evaluate surgeon-assessed brain bulk and measured intracranial pressure (ICP) in patients undergoing craniotomy for removal of supratentorial brain tumors during moderate hypocapnia or normocapnia. METHODS:Two-hundred and seventy-five adult patients with supratentorial brain tumors were randomized to one of two treatment sequences: hyperventilation (arterial carbon dioxide tension, Paco2 = 25 ± 2 mm Hg) followed by normoventilation (Paco2 = 37 ± 2 mm Hg) or normoventilation followed by hyperventilation. Ventilation and end-tidal CO2 tension were kept constant for 20 min. Patients were also randomly assigned to receive a propofol infusion or isoflurane anesthesia. At the end of each study period, subdural ICP was measured and the neurosurgeon, blinded to the treatment group, was asked to rate the brain bulk using a four-point scale. RESULTS:Using a generalized estimation equation model, we found that hyperventilation decreased the risk of increased brain bulk by 45%, P = 0.004, 95% confidence intervals 22% to 61%, and the number needed to treat was 8. The mean (±sd) ICP during hyperventilation, 12.3 ± 8.1 mm Hg, was lower than that during normoventilation, 16.2 ± 9.6 mm Hg, P < 0.001. Anesthetic regimen did not affect brain bulk assessment or ICP. CONCLUSIONS:In patients with supratentorial brain tumors, intraoperative hyperventilation improves surgeon-assessed brain bulk which was associated with a decrease in ICP.

Cerebral Blood Volume and Blood Flow at Varying Arterial Carbon Dioxide Tension Levels in Rabbits During Propofol Anesthesia

There are little data on the effects of propofol on cerebral blood volume (CBV). We studied the effects of changes in Paco2 on CBV and cerebral blood flow (CBF) during propofol anesthesia in eight New Zealand white rabbits. We also investigated the effects of propofol over time on CBV and CBF during normocapnia (control group). At normocapnia, the mean (± sd) CBV and CBF values were 2.41 ± 0.68 mL/100 g and 56 ± 28 mL/100 g/min, respectively,. When Paco2 was reduced from 41 to 27 mm Hg, no significant change in either CBV or CBF was observed (P > 0.10). However, increasing Paco2 from 41 to 58 mm Hg resulted in a 30% increase in CBV (3.08 ± 0.86 mL/100 g, P < 0.05) and a 91% increase in CBF (97 ± 39 mL/100 g/min, P < 0.01). In the control group, there were no significant changes in CBV and CBF (P > 0.10) during 2 h of propofol anesthesia. These results indicate that, during propofol anesthesia, cerebrovascular reactivity of blood flow and blood volume is maintained during hypercapnia but is markedly diminished during hypocapnia. Implications During propofol anesthesia in rabbits with normal brains, a reduction in the arterial carbon dioxide level may not always be accompanied by a reduction in brain blood flow and blood volume.

Sedative doses of remifentanil have minimal effect on ECoG spike activity during awake epilepsy surgery.

The use of remifentanil for sedation during awake epilepsy surgery has been described in a case report. However, little information is available regarding the effect of remifentanil on the quality of intraoperative electrocorticography (ECoG). This study was designed to investigate the effect of sedative doses of remifentanil on ECoG interictal spike activity among patients undergoing awake anterior temporal lobectomy for refractory epilepsy. Ten adult patients were studied prospectively. After baseline EcoG recordings were obtained, remifentanil was administered as a continuous infusion at 0.1 &mgr;g/kg/min and the ECoG recorded continuously for 15 minutes. Recordings obtained before and during the administration of remifentanil were compared with respect to spike frequency and location. A trend toward a small decrease in spike frequency was observed as patients became increasingly somnolescent and background ECoG activity slowed. The difference was not statistically significant. Blood pressure and heart rate were not adversely affected by the administration of remifentanil. Respiratory rates decreased in all patients (mean decrease, 8 breaths/min) and one patient transiently developed a respiratory rate of 4 breaths per minute that elicited a decrease in the rate of remifentanil administration. Remifentanil administered at sedation doses does not adversely affect intraoperatively recorded interictal spike activity. Further investigation of the use of this drug during awake epilepsy surgery is warranted.

Cervical spine motion: a fluoroscopic comparison of Shikani Optical Stylet® vs Macintosh laryngoscope

PurposeThe optimal technique to manage the airway in patients presenting with a potential or documented cervical spine (C-spine) injury remains unresolved. Using fluoroscopic video assessment, C-spine motion during laryngoscopy with a Shikani Optical Stylet® (SOS) was compared to C-spine motion during intubation using a Macintosh blade.MethodsTwenty-four healthy surgical patients gave written consent to participate in a crossover randomized controlled trial; all patients were subjected to both Macintosh and Shikani laryngoscopy with manual inline stabilization following induction of anesthesia. The C-spine motion was examined at four areas: the occiput-C 1 junction, C1-C2 junction, C2-C5 motion segment, and C5-thoracic motion segment. The time required for laryngoscopy was also measured (duration > 120 sec was deemed a failure of the laryngoscopy technique).ResultsOn average, C-spine motion was 52% less (P < 0.02) at three of the motion segments studied, occiput-C 1, C2-C5, and C5-thoracic when comparing SOS vs Macintosh laryngoscopy. There was no difference between techniques at the C1-C2 segment. Laryngoscopy with SOS (28 ± 17 sec) took longer than with Macintosh blade (17 ± 7 sec), P < 0.01. There were two failures out of 23 using the SOS, vs none with the Macintosh blade.ConclusionFor patients in whom C-spine movement is undesirable, use of the SOS may limit neck movement, while modestly increasing the time required to intubate, and/or the risk of procedure failure.RésuméObjectifLa question de la technique optimale de prise en charge des voies aériennes des patients présentant une lésion potentielle ou documentée de la colonne cervicale demeure sans réponse. Par le biais d’une évaluation vidéo fluoroscopique, le mouvement de la colonne cervicale durant la laryngoscopie à l’aide d’un stylet optique Shikani® (SOS) a été comparé au même mouvement durant l’intubation effectuée avec une lame Macintosh.MéthodeVingt-quatre patients chirurgicaux sains ont accepté par écrit de participer à une étude randomisée contrôlée croisée; tous les patients ont eu une laryngoscopie avec lame Macintosh et stylet optique Shikani®, avec stabilisation manuelle en ligne, suite à l’induction de l’anesthésie. Le mouvement de la colonne cervicale a été observé à quatre endroits : la jonction occipitale-C1, la jonction C1-C2, le segment de mouvement C2-C5, et le segment de mouvement C5-thoracique. Le temps requis pour la laryngoscopie a également été mesuré (si la durée > 120 sec, nous avons considéré cela comme un échec de la technique laryngoscopique).RésultatsLe mouvement de la colonne cervicale était en moyenne 52 % moins important (P < 0,02) à trois des segments de mouvements étudiés - occiput-C1, C2-C5, et C5-thoracique, en comparant la laryngoscopie avec SOS vs avec Macintosh. Aucune différence entre les techniques n’a été observée au segment C1-C2. La laryngoscopie avec SOS a nécessité 28 ± 17 sec en comparaison d’un temps de laryngoscopie plus court avec la lame Macintosh (17 ±7 sec, P <0,01 vs SOS). Deux échecs sur 23 ont eu lieu lors de l’utilisation du SOS, vs aucun avec la lame Macintosh.ConclusionChez les patients où le mouvement de la colonne cervicale est à éviter, le recours au SOS peut limiter le mouvement du cou tout en augmentant quelque peu le temps nécessaire à l’intubation et/ou le risque d’un échec de la procédure.

Cerebral Blood Volume and Blood Flow Responses to Hyperventilation in Brain Tumors During Isoflurane or Propofol Anesthesia

Using computerized tomography, we measured absolute cerebral blood flow (CBF) and cerebral blood volume (CBV) in tumor, peri-tumor, and contralateral normal regions, at normocapnia and hypocapnia, in 16 rabbits with brain tumors (VX2 carcinoma), under isoflurane or propofol anesthesia. In both anesthetic groups, CBV and CBF were highest in the tumor region and lowest in the contralateral normal tissue. For isoflurane, a significant decrease in both CBV and CBF was observed in all tissue regions with hyperventilation (P < 0.05), but without accompanying changes in intracranial pressure. However, the percent reduction in regional CBF with hypocapnia was two times larger than that observed in the CBV response (P < 0.01). In contrast, there were no significant changes in CBV and CBF in the Propofol group with hyperventilation for all regions (P > 0.10). In addition, there were no differences between CBV values for isoflurane at hypocapnia when compared with CBV values for propofol at normo- or hypocapnia (P > 0.34 and P > 0.35, respectively, in the tumor regions). Our results indicate that propofol increases cerebral vascular tone in both neoplastic and normal tissue vessels compared with isoflurane. CBV and CBF during normocapnia were significantly greater in all regions (tumor, peri-tumor, and contralateral normal tissue) with isoflurane than with propofol. CBV and CBF remained responsive to hyperventilation only with isoflurane.