Zirka H. Anastasian

Radiation Exposure of the Anesthesiologist in the Neurointerventional Suite

Background:Scatter radiation during interventional radiology procedures can produce cataracts in participating medical personnel. Standard safety equipment for the radiologist includes eye protection. The typical configuration of fluoroscopy equipment directs radiation scatter away from the radiologist and toward the anesthesiologist. This study analyzed facial radiation exposure of the anesthesiologist during interventional neuroradiology procedures. Methods:Radiation exposure to the forehead of the anesthesiologist and radiologist was measured during 31 adult neuroradiologic procedures involving the head or neck. Variables hypothesized to affect anesthesiologist exposure were recorded for each procedure. These included total radiation emitted by fluoroscopic equipment, radiologist exposure, number of pharmacologic interventions performed by the anesthesiologist, and other variables. Results:Radiation exposure to the anesthesiologists face averaged 6.5 ± 5.4 &mgr;Sv per interventional procedure. This exposure was more than 6-fold greater (P < 0.0005) than for noninterventional angiographic procedures (1.0 ± 1.0) and averaged more than 3-fold the exposure of the radiologist (ratio, 3.2; 95% CI, 1.8–4.5). Multiple linear regression analysis showed that the exposure of the anesthesiologist was correlated with the number of pharmacologic interventions performed by the anesthesiologist and the total exposure of the radiologist. Conclusions:Current guidelines for occupational radiation exposure to the eye are undergoing review and are likely to be lowered below the current 100–150 mSv/yr limit. Anesthesiologists who spend significant time in neurointerventional radiology suites may have ocular radiation exposure approaching that of a radiologist. To ensure parity with safety standards adopted by radiologists, these anesthesiologists should wear protective eyewear.

Statins Reduce Neurologic Injury in Asymptomatic Carotid Endarterectomy Patients

Background and Purpose— Statins are neuroprotective in a variety of experimental models of cerebral injury. We sought to determine whether patients taking statins before asymptomatic carotid endarterectomy exhibit a lower incidence of neurological injury (clinical stroke and cognitive dysfunction). Methods— A total of 328 patients with asymptomatic carotid stenosis scheduled for elective carotid endarterectomy consented to participate in this observational study of perioperative neurological injury. Results— Patients taking statins had a lower incidence of clinical stroke (0.0% vs 3.1%; P=0.02) and cognitive dysfunction (11.0% vs 20.2%; P=0.03). In a multivariate regression model, statin use was significantly associated with decreased odds of cognitive dysfunction (odds ratio, 0.51 [95% CI, 0.27–0.96]; P=0.04). Conclusions— Preoperative statin use was associated with less neurological injury after asymptomatic carotid endarterectomy. These observations suggest that it may be possible to further reduce the perioperative morbidity of carotid endarterectomy. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00597883

Factors that correlate with the decision to delay extubation after multilevel prone spine surgery.

Background: Multilevel spinal decompressions and fusions often require long anesthetic and operative times, which may result in airway edema and prolonged postoperative intubation. Delayed extubation can lead to bronchopulmonary infections and other complications. This study analyzed which factors correlated with the decision to delay extubation after multilevel spine surgery. Methods: We reviewed the records of 289 patients who underwent multilevel spine surgery lasting ≥8 hours in the prone position from 2006 to 2012. Variables hypothesized to affect the decision of the anesthesiologist to delay extubation at the end of the surgery were collected. These included preoperative factors (age, sex, ASA class, history of obstructive sleep apnea, BMI, previous spine surgery, current cervical surgery, anterior in addition to posterior spine surgery, emergency surgery) and intraoperative factors (difficult intubation, number of surgical levels, case time, estimated blood loss, fluid and blood administration, attending handoff and resident handoff, and case end time). We also compared the incidence of pulmonary postoperative complications between patients extubated at the end of the case to patients who had a delayed extubation. Results: A total of 126 patients (44%) were kept intubated after multilevel spine surgery. Multiple linear regression analysis showed factors that correlated with prolonged intubation which included age, ASA class, procedure duration, extent of surgery, total crystalloid volume administered, total blood volume administered, and the case end time. Patients who had a delayed extubation had a 3-fold higher rate of postoperative pneumonia. Conclusions: Our study found that age, ASA class, procedure duration, extent of surgery, and total crystalloid and blood volume administered correlate with the decision to delay extubation in multilevel prone spine surgery. It also finds that the time the case ends is an independent variable that correlates with the decision not to extubate at the end of a long multilevel spinal surgery. The incidence of postoperative pneumonia is higher in patients who had a delayed extubation after surgery.

Evoked Potential Monitoring Identifies Possible Neurological Injury During Positioning for Craniotomy

Somatosensory-evoked potential (SSEP) monitoring is commonly used to detect changes in nerve conduction and prevent impending nerve injury. We present a case series of two patients who had SSEP monitoring for their surgical craniotomy procedure, and who, upon positioning supine with their head tilted 30 degrees-45 degrees, developed unilateral upper extremity SSEP changes. These SSEP changes were reversed when the patients were repositioned. These cases indicate the clinical usefulness of monitoring SSEPs while positioning the patient and adjusting position accordingly to prevent injury.

Arterial Blood Pressure Management During Carotid Endarterectomy and Early Cognitive Dysfunction

BACKGROUND A common practice during cross-clamp of carotid endarterectomy (CEA) is to manage mean arterial pressure (MAP) above baseline to optimize the collateral cerebral blood flow and reduce the risk of ischemic stroke. OBJECTIVE To determine whether MAP management ≥20% above baseline during cross-clamp is associated with lower risk of early cognitive dysfunction, a subtler form of neurological injury than stroke. METHODS One hundred eighty-three patients undergoing CEA were enrolled in this ad hoc study. All patients had radial arterial catheters placed before the induction of general anesthesia. MAP was managed at the discretion of the anesthesiologist. All patients were evaluated with a battery of neuropsychometric tests preoperatively and 24 hours postoperatively. RESULTS Overall, 28.4% of CEA patients exhibited early cognitive dysfunction (eCD). Significantly fewer patients with MAP ≥20% above baseline during cross-clamp exhibited eCD than those managed <20% above (11.6% vs 38.6%, P < .001). In a multivariate logistic regression model, MAP ≥20% above baseline during the cross-clamp period was associated with significantly lower risk of eCD (odds ratio [OR], 0.18 [0.07-0.40], P < .001), whereas diabetes mellitus (OR, 2.73 [1.14-6.61], P = .03) and each additional year of education (OR, 1.19 [1.06-1.34], P = .003) were associated with significantly higher risk of eCD. CONCLUSION The observations of this study suggest that MAP management ≥20% above baseline during cross-clamp of the carotid artery may be associated with lower risk of eCD after CEA. More prospective work is necessary to determine whether MAP ≥20% above baseline during cross-clamp can improve the safety of this commonly performed procedure.

What matters during endovascular therapy for acute stroke: anesthesia technique or blood pressure management?

P ATIENTS who experience acute ischemic stroke increasingly are undergoing treatment with endovascular revascularization procedures. Davis et al. present a retrospective review encompassing their 6 yr experience treating 96 stroke patients with endovascular arterial revascularization, half receiving local anesthesia or sedation, and the remainder receiving general anesthesia. A number of recently published studies have implicated general anesthesia as a factor in poor outcome. All these studies have a common problem. The patients receiving general anesthesia had the confounding factor of being “sicker” at baseline than patients receiving local anesthesia and/or sedation: they had higher baseline values on their neurologic stroke scale, which would lead one to expect a higher postprocedure stroke volume, morbidity, and mortality. For example, in Davis et al., patients who received general anesthesia presented with higher baseline National Institutes of Health Stroke Scale scores (worse strokes), lower levels of consciousness, and higher rates of preprocedural aspiration. In this and other studies, general anesthesia was administered because of a lack of patient cooperation. Davis et al. postulated that “... [d]espite the likelihood that these patients are sicker ... there may be additional factors that contribute to poor outcome .... Specifically ... that peri-procedural blood pressures may have been influenced by anesthetic management and could plausibly have contributed to the observed differences in neurologic outcome.” In addition, the correlation analysis identified the possibility that general anesthesia and blood pressure were colinear variables. The authors present two models to examine the effect of either the type of anesthesia or the blood pressure nadir; they found both to correlate with poor outcome. This study underlines the importance of blood pressure management during anesthetic management in patients experiencing acute stroke. It is the first study to find that systolic blood pressures less than 140 mmHg significantly contributed to poor outcome. In our opinion, this is the most important result of this study. Induction of general anesthesia frequently causes a decrease in blood pressure. Intraoperative hypotension has been shown to affect cognitive outcome in patients undergoing cardiac surgery, and it may have effects on cognitive functioning that can be seen immediately after spine surgery in patients with a history of hypertension. In the studies published on the outcomes of anesthesia type in patients experiencing acute ischemic stroke, a decrease in blood pressure may have exaggerated consequences because of the loss of cerebral autoregulation and reliance on collateral circulation. Seventy percent (70%) of patients experiencing acute thromboembolic stroke present with hypertension, some without a history of hypertension, which gradually decreases during the next 24 h to various degrees depending on the type of stroke; a smaller percentage present with hypotension, which has a significantly worse prognosis. Data from the International Stroke Trial demonstrates a U-shaped relationship between baseline systolic blood pressure and death or dependency: “... early death increased by [18%] for every 10 mmHg below 150 mmHg (P less than 0.0001) and by [4%] for every 10 mmHg above 150 mmHg (P 0.023).” As Davis et al. discuss, the hemodynamic goals for the care of patients experiencing acute stroke are controversial. Although hypotension during the acute phase of ischemic stroke is associated with poor neurologic outcome, induced hypertension is clearly not the remedy for every patient. There probably is a subgroup of

Effect of atropine dose on heart rate during electroconvulsive therapy.

Introduction Transient bradycardia during the stimulation phase of electroconvulsive therapy (ECT) is a well-known clinical observation. The optimal dose of atropine needed to prevent bradycardia has not been determined. This study was designed to investigate the effect of low doses of atropine on heart rate during ECT. Methods Patients who received at least 2 different doses of atropine over their series of right unilateral ECT were included in the analysis. The anesthetic consisted of 0, 0.2, 0.3, or 0.4 mg of atropine, methohexital, and succinylcholine. Heart rate was measured by the RR interval, the time between sequential R waves on the electrocardiogram. Analysis was performed using logistic multivariate regression and repeated-measures multivariate analysis of variance. Results One hundred eighteen ECT sessions were identified from 19 patients. Patients were grouped into 4 groups by atropine dose (0, 0.2, 0.3, or 0.4 mg) with 9, 33, 13, and 63 ECT sessions identified for each dose, respectively. Patients who received atropine had significantly less bradycardia after electrical stimulus and a faster heart rate through the seizure than patients who did not receive atropine. There was no significant difference in heart rate between patients receiving 0.2, 0.3, and 0.4 mg of atropine at any time point. There was no significant difference in heart rate at time points after the seizure conclusion in any group of patients. Conclusion Low-dose atropine results in significantly less bradycardia after electrical stimulus. There was no significant difference in heart rate across low doses of atropine.

The effect of antihypertensive class on intraoperative pressor requirements during carotid endarterectomy.

BACKGROUND: Certain classes of antihypertensive drugs have been associated with intraoperative hypotension, and frequently, patients are receiving multiple classes of antihypertensive medications. We sought to determine whether one class of antihypertensive medication either alone, or in combination with other classes of antihypertensive medications, increased the probability of intraoperative hypotension, determined by the amount of vasopressor required during carotid endarterectomy (CEA) performed under general anesthesia with specific arterial blood pressure management. METHODS: This is a post hoc analysis of 252 patients scheduled for elective CEA under general anesthesia, all of whom participated in a prospective evaluation of cognitive dysfunction. Patients were characterized by class and number of preoperative antihypertensive medications taken. A predetermined anesthetic regimen was administered to all patients, with a phenylephrine infusion titrated to maintain mean arterial blood pressure at baseline before clamping the carotid artery, and approximately 20% above baseline during clamping. Computerized anesthesia records were used to record hemodynamics and to quantify medication administered intraoperatively. RESULTS: Patients taking diuretics as part of their antihypertensive regimen required significantly more (1.6 times) total intraoperative phenylephrine than those not taking diuretics, independently of the number of other antihypertensive medications. This difference in the phenylephrine requirement occurs only during the preclamp period, i.e., from induction to application of carotid artery clamping for the maintenance of preoperative blood pressure. However, in contrast to this result, there is no difference in pressor requirement comparing classes of antihypertensive medications to increase the mean arterial blood pressure 20% above baseline during the period when the carotid artery is clamped. CONCLUSION: Diuretics are associated with increased vasopressor requirements in patients having a CEA under general anesthesia in the preclamp period, which is likely true for any patient having a general anesthetic.

Assembly of a multichannel video system to simultaneously record cerebral emboli with cerebral imaging.

Stroke remains a significant risk of carotid revascularization for atherosclerotic disease. Emboli generated at the time of treatment either using endarterectomy or stent-angioplasty may progress with blood flow and lodge in brain arteries. Recently, the use of protection devices to trap emboli created at the time of revascularization has helped to establish a role for stent-supported angioplasty compared with endarterectomy. Several devices have been developed to reduce or detect emboli that may be dislodged during carotid artery stenting to treat carotid artery stenosis. A significant challenge in assessing the efficacy of these devices is precisely determining when emboli are dislodged in real time. To address this challenge, we devised a method of simultaneously recording fluoroscopic images, transcranial Doppler data, vital signs, and digital video of the patient/physician. This method permits accurate causative analysis and allows procedural events to be precisely correlated to embolic events in real time.

Attending Handoff Is Correlated with the Decision to Delay Extubation After Surgery.

BACKGROUND:Factors including ASA physical status, blood loss, and case length have been described as correlating with the decision to delay tracheal extubation after specific surgical procedures. In this retrospective study, we investigated whether handoffs by anesthesia attendings were associated with delayed extubation after general anesthesia for a broad range of surgical procedures. METHODS:We reviewed the records of 37,824 patients who underwent general anesthesia with an endotracheal tube for surgery (excluding tracheostomy surgery, cardiac surgeries, and liver and lung transplant surgeries) from 2008 to 2013 at Columbia University Medical Center. Our primary outcome was whether the patient was extubated at the end of the surgical case. We hypothesized that attending handoff was a factor that would independently affect the decision of the anesthesiologist to extubate at the end of the surgical case. In addition, we investigated whether the association between handoff and extubation was affected by the timing of the procedure (ending in the daytime versus evening hours) by including an interaction term in the analysis. We adjusted for other variables affecting the decision to delay extubation. RESULTS:Patients (5.4%, n = 2033) were not extubated in the operating room after the completion of their surgery. Cases with an attending handoff appeared to have a greater risk of delayed extubation with an adjusted risk ratio (aRR) of 1.14 (95% confidence interval [CI], 1.03–1.25). Further analysis demonstrated that the attending handoff had a significant effect in daytime cases (aRR, 1.62; 95% CI, 1.29–2.04) but not in evening cases (aRR, 1.07; 95% CI, 0.97–1.19). CONCLUSIONS:Attending handoff was an independent significant factor that increased the risk for the delay of extubation at the end of a surgical case.