Thomas J. Losasso

Labetalol and esmolol in the control of hypertension after intracranial surgery

The postoperative course of patients emerging from general anesthesia after intracranial surgery is frequently complicated by hypertension. This study examined the comparative efficacy of esmolol and labetalol in treating increases in blood pressure during emergence and recovery from anesthesia after intracranial surgery.Both esmolol and labetalol were equally effective in controlling systolic blood pressure on emergence and in the recovery room in patients undergoing intracranial surgery. However, decreases in heart rate were significantly more frequent in the immediate postoperative period in patients given labetalol. An increase in blood pressure after intracranial surgery appears to be a transitory phenomenon adequately treated with a short-acting antihypertensive agent such as esmolol.

Complication from a nasopharyngeal airway in a patient with a basilar skull fracture

Airway management in patients with craniofacial trauma presents the anesthesiologist with several complex problems. Not only are these patients often in acute respiratory distress, but also disruption of normal anatomic relationships in the head and neck can make placement of artificial airways, laryngoscopy, and tracheal intubation both technically difficult and hazardous. We present a case in which insertion of a nasopharyngeal airway in a patient with head and neck injury may have contributed to further damage to the central nervous system

Fifty percent nitrous oxide does not increase the risk of venous air embolism in neurosurgical patients operated upon in the sitting position.

Although nitrous oxide (N2O) should theoretically increase the severity of venous air embolism (VAE), data confirming this hazard in clinical situations are not available. The effect of 50% N2O on the incidence and severity of VAE and on the emergence time from anesthesia was evaluated in 300 neurosurgical patients operated upon while in the sitting position. Of these, 110 patients underwent craniectomy for posterior fossa pathology and 190 patients underwent cervical spine surgery (CSS). Patients were randomized to receive either 50% N2O in oxygen (O2) (N2O group) or O2 (no-N2O group) as part of an isoflurane-fentanyl-based anesthetic. In patients in the N2O group, N2O administration was discontinued immediately upon Doppler-detection of VAE and was reinstituted in not less than 30 min after resolution of the episode. The incidence of Doppler-detected VAE was significantly greater in the craniectomy group than the CSS group (43% vs. 7%, respectively; P less than 0.001). N2O had no effect on the incidence of VAE or the severity of VAE as judged by the magnitude of the reduction in blood pressure during hemodynamically significant episodes of VAE, the volume of gas aspirated from the right atrial catheter during episodes of VAE, or the magnitude of the decrease in end-tidal carbon dioxide tension during episodes of VAE. Hemodynamically significant episodes of VAE (i.e., episodes associated with a reduction in systolic blood pressure of greater than or equal to 15 mmHg) occurred in 17 of the 61 patients experiencing VAE (28%) and was not different between the N2O and no-N2O groups. Similarly, hemodynamically significant episodes of VAE (n = 18) accounted for 15% of all episodes of VAE (n = 118) and was not different between the N2O and no-N2O groups. Emergence time was not significantly different between the N2O and no-N2O groups, with mean times of 2 +/- 6 and 3 +/- 7 min (+/- SD), respectively. Emergence time was significantly longer in the craniectomy group than in the CSS group (5 vs. 1 min, respectively; P less than 0.001). Within the craniectomy group, the incidence of Doppler-detected VAE was significantly less in patients with previous surgery at the operative site (21%) compared to patients without previous surgery at the operative site (47%). Postoperatively, no complications could be related to the use of N2O or directly attributed to the occurrence of VAE.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of desflurane and isoflurane on cerebrospinal fluid pressure in humans with supratentorial mass lesions

Desflurane, a new volatile anesthetic, produces cerebral vasodilation. The purpose of this study was to compare the effects of 1 MAC desflurane with those of isoflurane on cerebrospinal fluid pressure (CSFP) in patients with supratentorial mass lesions and a mass effect on computerized tomography (CT scan). Twenty adult patients undergoing craniotomy for removal of supratentorial mass lesions were studied. Ten patients received desflurane and 10 patients received isoflurane. Prior to induction of anesthesia, a radial artery catheter was inserted and a 19-G needle was inserted into the lumbar subarachnoid space to measure CSFP. Baseline arterial blood gases and CSFP were measured with the patient awake and unmedicated. Anesthesia was induced with thiopental (6-9 mg/kg) and muscle relaxation achieved with vecuronium (0.2 mg/kg). The lungs of all patients were hyperventilated to achieve an arterial CO2 tension of 24-28 mmHg. Anesthesia was maintained with 1 MAC volatile anesthetic, either 7.0% desflurane or 1.2% isoflurane in an air:O2 mixture to maintain an inspired O2 fraction (FIO2) of 0.50. Patients were not administered any other anesthetic until the dura was incised. Mean arterial pressure was kept within 20% of the patients mean ward values with the use of esmolol or phenylephrine. CSFP, mean arterial pressure, end-tidal CO2 concentration (PETCO2), hemoglobin O2 saturation, and cerebral perfusion pressure were recorded with the patient awake, immediately postinduction with thiopental, postintubation, after institution of the volatile anesthetic, and every 5 min until the dura was incised. There was no difference in the mean (+/- SD) awake CSFP between the desflurane (11 +/- 4 mmHg) and the isoflurane (10 +/- 2 mmHg) groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection and hemodynamic consequences of venous air embolism : does nitrous oxide make a difference ?

Volume expansion of intravascular air by nitrous oxide (N2O) may improve the sensitivity of monitors used to detect venous air embolism (VAE) and/or exacerbate hemodynamic changes following VAE. The purpose of this study was to determine if the administration of N2O alters the sensitivity (i.e., threshold of detection) of monitors used to detect VAE or the hemodynamic consequences of VAE. Twenty-one dogs were monitored for VAE with precordial Doppler ultrasound, transesophageal echocardiography (TEE), changes in end-tidal carbon dioxide tension (ETCO2), and changes in pulmonary artery pressure (PAP). Venous air was infused at rates between 0.005 and 0.4 ml.kg-1.min-1 during 1 MAC (total anesthetic level) of isoflurane with and without 50% N2O (group 1, n = 7) or isoflurane with and without 75% N2O (group 2, n = 7). The mean quantity of infused air necessary to elicit a positive response in both the presence and absence of N2O was calculated for each monitor. Positive responses were defined as follows: unmistakable audible change in frequency on Doppler ultrasound, visualization of densities consistent with air bubbles in the right cardiac chambers or outflow tract on TEE, a decrease in ETCO2 greater than or equal to 2 mmHg, and an increase in mean PAP greater than or equal to 3 mmHg. In group 3 (n = 7), venous air was infused at rates between 0.1 and 0.8 ml.kg-1.min-1 during 1 MAC (total anesthetic level) of isoflurane with and without 50% N2O. In group 3, N2O administration was discontinued immediately upon Doppler detection of VAE and air infusion continued until mean arterial pressure (MAP) decreased by 10 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

Electroencephalographic Monitoring of Cerebral Function During Asystole and Successful Cardiopulmonary Resuscitation

revious studies have documented changes in the electroencephalogram (EEG) that occur secP ondary to cerebral ischemia (1-3). During periods of complete global ischemia, such as occur after cardiac arrest, cerebral blood flow ceases. The functional (electrical) activity of the cerebral cortex, as monitored by the EEG, is abolished as a result of compromised cerebral oxygenation. Initially, there is a reduction in the high-frequency component of the EEG with an apparent increase in the low-frequency component; soon thereafter, the EEG becomes isoelectric. In a patient with generalized EEG suppression that occurs secondary to cardiac arrest, it is appropriate to assume that cerebral oxygenation due to cardiopulmonary resuscitation (CPR) is adequate in the setting of EEG recovery. In this setting, EEG changes associated with cardiac arrest and CPR are of significance. Using seven-channel EEG monitoring in a patient undergoing carotid endarterectomy, Moss and Rockoff (4) described the changes in EEG activity that occurred during a brief period (27 s) of ventricular asystole and the prompt return of EEG activity with restoration of intrinsic cardiac rhythm and blood pressure. Using compressed spectral-array EEG monitoring in a patient undergoing carotid endarterectomy, Young and Ornstein (5) described the changes in spectral edge frequency during cardiac arrest and CPR. As pointed out by these authors, because they lacked a concurrent display of the raw EEG, they could not separate artifact from EEG activity during the time of resuscitation. Neither of these cases describe changes in the raw EEG during manual chest compressions. We describe here a case of intraoperative cardiac arrest (of approximately 2-min duration) and the resulting changes in

Carotid endarterectomy in elderly patients

Between 1971 and 1989, 749 carotid endarterectomies were performed at our institution for symptomatic carotid occlusive disease in patients older than 70 years of age. Of these procedures, 693 were done in patients 71 through 80 years of age, and 56 were done in patients between the ages of 81 and 90 years. The neurologic morbidity and perioperative mortality in the former group were 2.9% and 1.4%, respectively, whereas in the latter group the corresponding values were 5.4% and 0%, respectively. For the entire group, the neurologic morbidity was 3.1% and the mortality was 1.3%. Of the 23 new postoperative neurologic deficits, 19 (83%) occurred in high-risk patients with severe preoperative neurologic or medical risks, and 14 (61%) of these deficits were minor. In selected elderly patients with symptomatic hemodynamically significant carotid occlusive disease, endarterectomy seems to be a safe procedure that is associated with acceptably low perioperative morbidity and mortality.

Ventriculoatrial shunt distal catheter placement using transesophageal echocardiography:technical note.

Accurate placement of the distal end of a ventriculoatrial shunt at the cavo-atrial junction is important for long-term shunt function as well as for avoiding cardiac arrhythmias, thrombus formation, and damage to myocardial tissue. Standard methods of intraoperative localization, including chest x-ray, pressure measurements, and electrocardiogram recording, can be inaccurate. By using intraoperative transesophageal echocardiography, the distal end of the catheter can be localized to the cavo-atrial junction.

Comparison of a transesophageal and precordial ultrasonic doppler sensor in the detection of venous air embolism

The Aloka SSD-870 transesophageal echocardiograph is equipped with a Doppler sensor at the distal end of the probe, thereby providing Doppler ultrasound monitoring for VAE (venous air embolism) in addition to visual monitoring for VAE with echocardiography

Response of fetal heart rate to maternal administration of esmolol

The effect of esmolol on fetal heart rate (FHR) after maternal administration has not been reported previously. We describe the use of esmolol in a 22-week pregnant woman undergoing resection of a cerebellar arteriovenous malformation and its effect on FHR