Roy F. Cucchiara

Outcome Following Posterior Fossa Craniectomy in Patients in the Sitting or Horizontal Positions

Controversy continues to surround the use of the sitting position for neurosurgical procedures. This retrospective review of 579 posterior fossa craniectomies performed over a 4-yr period from 1981 through 1984 examines outcome following these procedures performed with the patients in cither the sitting (n = 333) or horizontal (supine, prone, lateral, park bench) (n = 246) position. Multiple preoperative, intraoperative, and postoperative variables were analyzed. Venous air embolism occurred significantly more often in patients in the sitting position (45% versus 12%). However, no morbidity or mortality was attributed to venous air embolism. The incidence of hypotension with positioning was not different by position (19% in the sitting patients and 24% in the horizontal patients). Average blood replacement was significantly lower in the sitting patients (359 ml versus 507 ml), and the incidence of transfusion of greater than two units of blood was significantly higher in the horizontal patients (13% versus 3%). Postoperative cranial nerve function was significantly better in patients in the sitting group as compared to those in the horizontal group. The incidence of perioperative cardiopulmonary complications was not different between groups. These outcome data suggest that there are potential advantages and disadvantages of both the sitting and horizontal positions without supporting a significantly increased morbidity or mortality associated with either position.

Multicenter Study of General Anesthesia. II. Results

A prospective, stratified, randomized clinical trial of the safety and efficacy of four general anesthetic agents (enflurane, fentanyl, halothane, and isoflurane) was conducted in 17,201 patients (study population). Patients were studied before, during, and after anesthesia for up to 7 days. Nineteen patients died (0.11%), and in seven of these (0.04%) the anesthetic may have been a contributing factor. The rates of death, myocardial infarction, and stroke in the study population were so low (less than 0.15%) that no conclusions regarding the relative rates of these outcomes among the four anesthetic agents could be reached. The rates of 16 of 66 types of adverse outcomes in the study population were significantly different among the four study agents. Most of these outcomes were minor. However, severe ventricular arrhythmia (P less than 10(-6)) was more common with halothane, severe hypertension (P less than 10(-6)) and severe bronchospasm (P = 0.028) were more common with fentanyl, and severe tachycardia (P = 0.001) was more common with isoflurane. Recovery from anesthesia during the first 30 min was slowest in those patients who received halothane (P less than or equal to 0.001). In addition, patients who received fentanyl experienced less pain during the first hour in the recovery room (P less than 10(-6)). In conclusion, clinically important differences do exist for some outcomes among the four study agents.

Isoflurane and Cerebrospinal Fluid Pressure in Neurosurgical Patients

The effect of isoflurane on cerebrospinal fluid pressure (CSFP) was determined in 20 patients undergoing craniotomy for intracranial supratentorial neoplasm or hematoma. In 15 of these patients, following endotracheal intubation, hyperventilation sufficient to result in Paco2 25–30 torr was begun simultaneously with the introduction of 1 per cent isoflurane. In the remaining five patients ventilation was equivalent, but normocapnia was maintained by adding CO2 to the inspired gases. In the hypocapnic patients CSFPs did not increase above awake values (range 5–45 torr) following isoflurane administration. In the normocapnic patients CSFPs consistently increased. In three of these five patients the increases were precipitous, but were corrected rapidly by establishment of hypocapnia. The authors conclude that the known cerebral vasodilator properties of isoflurance can be countered effectively by hypocapnia. Furthermore, unlike the situation with halothane, it is not necessary to establish hypocapnia prior to introducing isoflurane in order to avoid CSFP increases.

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.

The Effects of Isoflurane on Canine Cerebral Metabolism and Blood Flow

The cerebral metabolic and vascular effects of isoflurane (Forane) were investigated in six unmedicated ventilated dogs. At the MAC of this anesthetic (1.4 per cent, end-expired) there was a 23 per cent decrease in the rate of cerebral oxygen consumption (CMRO2) (compared with values at end-expired concentrations of <0.1 per cent). At a higher concentration of isoflurane (2.4 per cent, end-expired), a 30 per cent reduction in CMRO2, was observed. Cerebral blood flow (CBF) increased by 33 and 63 per cent at the 1.4 and 2.4 per cent concentrations, respectively. The increase in CBF was due entirely to a decrease in cerebral vascular resistance (CVR) and occurred despite an accompanying significant decrease in arterial blood pressure. The response of CBF to change in PaCO2 was appropriate during isoflurane anesthesia and was not different from that previously observed during halothane and metboxyflurane anesthesia.

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

Transesophageal echocardiography and transcutaneous O2 and CO2 monitoring for detection of venous air embolism.

The sensitivities of current monitoring methods for detection of air embolism were compared in eight anesthetized dogs. Air was infused at controlled rates of 0.001 and 0.005 ml. k−1.min−1for 1 min; 0.01, 0.05, 0.1, 0.2, and 0.4 ml.kg−1for 6 min; and 5 ml. kg−1bolus injection. Based on the mean quantity of air infused to elicit a positive response, the monitors could be placed into three significantly different sensitivity groups. Transesophageal echocardiography (TEE) and precordial Doppler ultrasound were the most sensitive monitoring methods detecting 0.19 and 0.24 ml. kg−1of air, respectively. TEE detected air during six infusions in which the Doppler failed to do so. The next most sensitive group of monitoring methods included pulmonary artery pressure (PAP), end-tidal CO2 (Ptco2), arterial oxygen tension (Pao2), and transcutaneous oxygen tension (Ptco2). The mean quantity of air infused to elicit a positive response in this group of monitors ranged from 0.61 to 0.76 ml. kg−1. The response of Ptco2, Pao2, PETco2, and PAP equally reflected the quantity of air infused. The least-sensitive group of methods included arterial and transcutaneous carbon dioxide tension and systemic arterial blood pressure. These data indicate that TEE is more sensitive than Doppler ultrasound and that PAP, PETco2, and Ptco2 are equally sensitive in detecting venous air embolism in the dog.

Preoperative and Intraoperative Echocardiography to Detect Right-to-Left Shunt in Patients Undergoing Neurosurgical Procedures in the Sitting Position

In patients undergoing neurosurgical procedures at high risk for venous air embolism (VAE), the presence of a right-to-left shunt adds an additional risk for paradoxical air embolism (PAE). Although this is a rare complication, it can have devastating results. The most common form of right-to-left shunt is a patient foramen ovale (PFO), which can be detected by contrast echocardiography. This study evaluates the efficacy of preoperative precordial and intraoperative transesophageal echocardiography (TEE) to detect right-to-left shunting in patients undergoing neurosurgical procedures while in the sitting position. In 101 patients precordial contrast echocardiography was performed prior to surgery. The Valsalva maneuver was utilized as a provocative maneuver to facilitate demonstration of right-to-left shunting. Fifty-one of these patients also had intraoperative TEE monitoring. Right-to-left shunting was demonstrated in only six of the 101 patients examined. Of these, four were detected by TEE. This is less than the expected incidence based on the known incidence of PFO in the general population. The usefulness of preoperative ECHO as a screening test for PFO in patients undergoing neurosurgical procedures is limited, but when a PFO is found, valuable information is acquired to help manage these patients.

Canine Cerebral Oxygen Consumption during Enflurane Anesthesia and Its Modification during Induced Seizures

The effects of enflurane at <0.1, 2.2, and 4.2 per cent (end-expired) concentrations on cerebral metabolism and circulation were studied in six dogs. A 34 per cent decrease in cerebral oxygen consumption (CMRO2) occurred at 2.2 per cent (approximately MAC), and no further decrease was observed at 4.2 per cent. Cerebral blood flow (CBF) was increased at each of the higher concentrations despite progressive significant decreases in arterial pressure. In four additional dogs, anesthesia was maintained at 1.5 MAC enflurane (3.4 per cent end-expired) and seizures were induced by hyperventilation (PaCO2 20 mm Hg) and intermittent hand clapping. Typical electroencephalographic (EEG) seizure patterns were accompanied by a 48 per cent increase in CMRO2 (mean) and gross skeletal muscle activity. Control conditions were re-established and seizures were again induced by pentylenetetrazol (30 mg/kg). These seizures could not be differentiated from those previously induced by hypocapnia and hand clapping. We conclude that enflurane generally resembles other halogenated anesthetics in its effects on CMRO2 and CBF but differs in producing seizures similar to those produced by a known convulsant.

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)