Laser resistant stainless steel endotracheal tube: experimental and clinical evaluation.

A fire due to endotracheal tube (ET) ignition is a catastrophic event that may occur during laser surgery of the upper airway, regardless of the wavelength utilized. Although methods exist that permit laser surgery without an ET, this is frequently not feasible. The current investigation was undertaken to evaluate the efficacy of a double-cuffed stainless steel ET, first in the laboratory and subsequently in a clinical setting. Bench testing was performed using CO2 (both standard and milliwatt) and KTP/532 lasers. Only the distal polyvinyl chloride cuffed end of the tube was potentially ignitable, however, the appropriate use of saline to fill the cuffs allowed only for cuff perforation without ignition. Canine testing was performed in 10 animals: 4 dogs were intubated from 3 to 4.5 hours with the laser resistant stainless steel endotracheal tube (LRSS-ET) (Laser-Flex Tracheal Tube; Mallinckrodt Anesthesia Products, St. Louis, MO) and 2 with an aluminum tape wrapped red rubber ET. Visual and histological examination were performed in both groups at 3 and 7 days. Four dogs underwent CO2 laser laryngeal surgery with visual and histological examination performed at 7 days postoperatively. No untoward effects could be demonstrated due to the LRSS-ET. A clinical study was then performed in 24 patients who underwent laser surgery of the upper aerodigestive tract with either a CO2 or KTP/532 laser. In all cases ventilation was adequate, the shaft of the LRSS-ET proved impervious to the laser, and the distal end of the tube protected the tracheobronchial tree safely.(ABSTRACT TRUNCATED AT 250 WORDS)

Flumazenil reverses sedation after midazolam-induced general anesthesia in ambulatory surgery patients.

Flumazenil, a specific competitive benzodiazepine antagonist, was evaluated for reversal of residual sedation after midazolam-induced ambulatory general anesthesia. Endotracheal anesthesia was begun with midazolam (mean +/- SD dose 12.4 +/- 2.4 mg), followed by nitrous oxide in oxygen, fentanyl, and succinylcholine, for gynecologic surgery lasting 38.6 +/- 12.5 min. After surgery, 29 women were given repeated injections of small amounts of either flumazenil or placebo until awake and calm. The mean flumazenil dose was 0.83 +/- 0.04 mg. Assessment of recovery was based on psychodiagnostic tests (visual analog sedation scale, Trieger dot, digit symbol substitution), pulse oxygen saturation, and end-expired carbon dioxide tension. Patients given flumazenil scored significantly better than did those given placebo on the psychodiagnostic tests for 5-60 min, but the groups were no longer different 120 and 180 min after the conclusion of surgery. All scores did not return to preoperative values by 180 min. Pulse oxygen saturation and end-expired carbon dioxide tension showed improvement from postoperative levels at 15 min after flumazenil injection. A controllable degree of midazolam reversal was achieved with flumazenil, but the duration of reversal was limited. Caution is needed to avoid premature discharge of ambulatory patients after midazolam-induced general anesthesia during the time that flumazenil is effective.

Comparative analysis of the safety of endotracheal tubes with the KTP laser.

The KTP laser has been used increasingly to treat various disorders of the upper aerodigestive tract. To establish the relative safety of the endotracheal tubes that are currently available, we performed laboratory testing of these tubes by exposing them to the KTP laser in an oxygen-rich environment. Based on our observations, tubes that were all metal or metal-wrapped endotracheal tubes were determined to be the safest. The advantage of using the all-metal tube was that it did not need wrapping. This tube also has a second distal cuff, which would allow for continued ventilation if the proximal cuff becomes disrupted. However, under these circumstances, insertion of a new nondisrupted tube is advised.

Esmolol for control of increases in heart rate and blood pressure during tracheal intubation after thiopentone and succinylcholine.

Esmolol, an ultra-short-acting cardioselective beta-adrenergic blocker, was investigated in a double-blind prospective protocol for its ability to control haemodynamic responses associated with tracheal intubation after thiopentone and succinylcholine. Thirty ASA physical status I patients received a 12-minute infusion of esmolol (500 micrograms X kg-1 X min-1 for four minutes, then 300 micrograms X kg-1 X min-1 for 8 minutes) or saline. Five minutes after the start of the drug/placebo infusion, anaesthesia was induced with 4 mg X kg-1 thiopentone followed by succinylcholine for tracheal intubation. Prior to induction esmolol produced significant decreases in heart rate (HR) (9.3 +/- 1.8 per cent) and rate-pressure product (RPP) (13.1 +/- 1.8 per cent), systolic blood pressure (SAP) (4.3 +/- 1.5 per cent) and mean arterial blood pressure (MAP) (1.7 +/- 2.0 per cent). Increases in HR, SAP and RPP after intubation were approximately 50 per cent less in patients given esmolol compared to patients given placebo. There were highly significant differences in HR (p less than 0.0001), and RPP (p less than 0.0005) and significant differences in SAP (p less than 0.05) when the maximal esmolol post-intubation response was compared to the maximal placebo response. Infusion of esmolol in the dose utilized in this study significantly attenuated but did not completely eliminate cardiovascular responses to intubation.

A clinical sign to predict difficult tracheal intubation: a prospective study.

It has been suggested that the size of the base of the tongue is an important factor determining the degree of difficulty of direct laryngoscopy. A relatively simple grading system which involves preoperative ability to visualize the faucial pillars, soft palate and base of uvula was designed as a means of predicting the degree of difficulty in laryngeal exposure. The system was evaluated in 210 patients. The degree of difficulty in visualizing these three structures was an accurate predictor of difficulty with direct laryngoscopy (p less than 0.001).

Low thoracic epidural anaesthesia for elective cholecystectomy in a patient with congenital heart disease and pulmonary hypertension.

A 52-year-old male with pulmonary hypertension secondary to partial anomalous pulmonary venous return unassociated with atrial septal defect was given thoracic epidural anaesthesia for elective cholecystectomy. Partial anomalous pulmonary venous return is a rare congenital anomaly characterized by increased pulmonary blood flow which in severe cases results in pulmonary hypertension subjecting the right ventricle to strain. An epidural catheter was placed at the T11-T12 interspace and anaesthesia was established to the T4 dermatomal level with bupivacaine (180 mg) and lidocaine (100 mg). Central venous pressure, pulmonary artery pressure, radial artery pressure, and cardiac output were monitored. There was minimal change in pulmonary arterial pressure, although there was a significant drop in systemic arterial pressure. Thoracic epidural block is recommended for upper abdominal surgery in clinical situations with pulmonary hypertension.

Cerebrospinal fluid human chorionic gonadotropin levels in normal pregnancy and choriocarcinoma.

We measured human chorionic gonadotropin levels simultaneously in the serum and cerebrospinal fluid of 36 normal pregnant women and of six patients with choriocarcinoma. During normal pregnancy, human chorionic gonadotropin levels in the cerebral spinal fluid correlated well with those in the serum in both the first and third trimesters. A serum-cerebral spinal fluid human chorionic gonadotropin ratio of less than 60 has previously been reported as a sensitive diagnostic test for trophoblastic central nervous system involvement. However, we found this ratio to be less than 60 in one patient undergoing first trimester abortion and in one patient with nonmetastatic choriocarcinoma. Furthermore, two patients with documented trophoblastic cerebral metastases had serum-cerebral spinal fluid human chorionic gonadotropin ratios in excess of 60. Results of our study, thus, indicate that determination of a single serum-cerebral spinal fluid human chorionic gonadotropin ratio may not conclusively prove or exclude trophoblastic central nervous system metastases. Unless it is corroborated by other diagnostic means, a single decreased serum-cerebral spinal fluid human chorionic gonadotropin ratio is insufficient evidence to initiate multimodality treatment for presumptive central nervous system involvement.