Biomedical subjects
J Ehrenwerth
Publications and source records attributed to J Ehrenwerth.
Electrical safety in the operating room: important old wine, disguised new bottles.
Explore the source record for details and available documents.
Facilitation of fiberoptic orotracheal intubation with a flexible tracheal tube.
Advancement of a tracheal tube (TT) over a flexible fiberoptic bronchoscope (FOB) is often impeded by obstruction at the arytenoid cartilage or epiglottis. We tested the hypothesis that the use of a flexible, spiral-wound TT, rather than the standard, preformed TT would facilitate tube passage into the trachea over the FOB. Forty patients scheduled to undergo general anesthesia with tracheal intubation were randomized to two groups. Then the trachea was intubated with a FOB, followed by passage of either a standard, preformed TT or a flexible, spiral-wound TT over the FOB. Ease of TT advancement over the FOB into the trachea was graded on a 1 (easy) to 3 (difficult) scale, and differences between the two groups were compared with chi 2 analysis. The overall scores were compared with Wilcoxon's ranked sum test. Statistical significance was defined as P < 0.05. In patients randomized to the regular TT, only 35% (7/20) of first attempts to advance the TT over the FOB were successful. In the patients randomized to the spiral-wound TT, 95% (19/20) of first attempts were successful (P < 0.0001). Of the 13 regular TTs that were not successfully advanced on the first attempt, seven could not be passed after the second or third attempt (necessitating the use of the cross-over spiral-wound TT). In the only instance in which a spiral-wound tube was not successfully passed into the trachea on the first attempt, passage also was not achieved after the second or third attempt.(ABSTRACT TRUNCATED AT 250 WORDS)
Assessment of residual curarization using low-current stimulation.
The present study employed train-of-four (TOF) stimulation at a current of 20 mA to assess the incidence and degree of residual neuromuscular blockade in 64 randomly selected Post Anesthesia Care Unit (PACU) patients. Group C (Control, n = 10) had received anaesthesia without nondepolarizing muscle relaxant; Group V (n = 25) had received vecuronium; and Group P (n = 29) had received pancuronium. At the end of surgery, each patient had been considered by his anaesthetist to have adequate neuromuscular function on the basis of clinical signs and tactile or visual evaluation of responses to TOF stimulation. However, upon testing in the PACU 15 min later, 45% (13 of 29) of Group P patients and 8% (2 of 25) of Group V patients had a TOF ration less than 0.70. This study indicates that residual curarization may be commonly encountered following long-acting relaxants despite qualitative intraoperative TOF monitoring. The present incidence, detected at a current of 20 mA, is consistent with previous reports which employed supramaximal TOF stimulation. We conclude that despite intraoperative monitoring, residual curarization following long-acting nondepolarizing agents is common and that it may be detected with TOF at a low stimulating current (20 mA).
Depth of placement of left double-lumen endobronchial tubes.
Data on the normal depth of insertion of double-lumen tubes have not been published. We studied 101 adult patients undergoing thoracic operations whose tracheas were intubated with a left double-lumen tube. A fiberoptic bronchoscope was introduced into the tracheal lumen, and the tube position was adjusted until the cephalad surface of the bronchial cuff was immediately below the carinal bifurcation. The average depth of insertion for both male and female patients 170 cm tall was 29 cm, and for each 10-cm increase or decrease in height, average placement depth was increased or decreased 1 cm. The correlation between depth of insertion and height was highly significant (P less than 0.0001) for both male and female patients. As depth of DLT insertion at any given height was normally distributed, a technique to confirm correct double-lumen tube position always should be used after initial placement.
Stimulation with submaximal current for train-of-four monitoring.
The present study evaluated responses to train-of-four (TOF) stimulation at a range of stimulating currents. Traditionally TOF has been applied with a supramaximal stimulus but this may be quite uncomfortable for the awake patient. In the first part of this study, 12 healthy volunteers quantified (by 10-cm visual analog scale) the discomfort associated with TOF stimulation at 20, 30, and 50 mA. The median VAS scores were 2, 3, and 6, respectively (P less than 0.05 for differences between each group). In the second part, single twitch and TOF responses were compared at 20, 30, and 50 mA in 64 postoperative and in 19 intraoperative patients who had ratios of the fourth to the first twitch (T4/T1) ranging from 0.15-1.03. In all patients, neuromuscular responses to nerve stimulation were recorded by a mechanogram, and the T4/T1 ratios were calculated. Although single twitch heights increased significantly as amperage was increased, there was no statistical difference in the T4/T1 ratios at the three different currents. The mean +/- SD T4/T1 ratios at 20, 30, and 50 mA were 0.795 +/- 0.247, 0.798 +/- 0.237, and 0.802 +/- 0.233, respectively (P = ns). It is concluded that TOF monitoring using a submaximal stimulus is more comfortable for the awake patient who is suspected of residual weakness, and that T4/T1 testing can be reliably accomplished intraoperatively as well as postoperatively using submaximal stimuli.
Pro: proper positioning of a double-lumen endobronchial tube can only be accomplished with endoscopy.
Explore the source record for details and available documents.
Pulse oximetry in the postanesthesia care unit.
Explore the source record for details and available documents.
What is the normal work of breathing.
Explore the source record for details and available documents.
Placement of double-lumen endobronchial tubes. Correlation between clinical impressions and bronchoscopic findings.
Double-lumen endobronchial tubes were placed "blindly" in 23 patients undergoing thoracotomy. Clinical criteria suggested satisfactory positioning in all cases; however, subsequent fibreoptic bronchoscopy revealed malposition in 48%. Bronchoscopic findings included the inability to view the bronchial cuff, narrowing of the bronchial lumen of the tube at the level of the cuff and herniation of the cuff over the carina. The potential hazards associated with these findings are discussed.
Transport of critically ill adults.
Interhospital transport can be hazardous because of rapid changes in a patient's physiologic status and the use of monitoring systems. A retrospective study evaluated the first 204 critically ill adult patients transported from community hospitals to Stanford Medical Center by a special transport team. To relate the risk of transport to severity of illness, a retrospective scoring system was devised. Sixty-one percent (n = 125) of the patients were at high risk for transport. The patients were stabilized at the referring hospital, and invasive monitoring was used as mandated by the patient's condition. The average transport distance was 133 km, and the average duration of transport was 4.38 h. One hundred and five patients (51.5%) were transported by air, and the remaining patients were transported by surface ambulance. All patients survived the transport, and 71.6% were eventually discharged from the hospital. Hospital mortality correlated with the risk-scoring system (p less than .01) and increased five-fold as severity of illness increased. This study demonstrates that, with appropriate hemodynamic stabilization and monitoring, severely ill patients can be transported safely.
Prolonged neuromuscular blockade in a parturient associated with succinylcholine.
Explore the source record for details and available documents.
One-lung anesthesia in morbidly obese patients.
Explore the source record for details and available documents.
Postoperative muscle pains and suxamethonium.
Two matched groups of patients with Hodgkin's disease undergoing a staging laparotomy received thiopentone, pancuronium bromide or suxamethonium 1.0 mg kg-1 (group 2) to facilitate tracheal intubation. There were no differences in the sites or degree of postoperative myalgia between the groups. It is concluded that efforts to reduce the frequency of suxamethonium muscle pains in patients having major abdominal operations are not justified.