Depth of insertion of the ProSeal laryngeal mask airway.

BACKGROUND: The depth of insertion of the ProSeal laryngeal mask airway (PLMA) is unknown. We measured depth of insertion in satisfactorily positioned PLMAs. METHODS: All women received size 4 masks and men size 5 masks. We measured the position of the integral bite block in relation to the upper incisors documented in patients over a 6-month period. Depth of insertion was scored by dividing the integral bite block into quarters. Satisfactory positioning of the ProSeal itself was determined by (i) positive 'suprasternal notch test', (ii) no venting via the drain tube during maximal lung inflation, and (iii) an unobstructed airway. RESULTS: We studied 274 patients (147 women and 127 men). The midway point of the bite block was proximal to the incisors (e.g. within the oropharynx) in 78% of women (95% CI 71-85%) and 92% of men (95% CI 87-97). The standard deviation for the depth distribution in women was 0.8 cm and for men was 1.0 cm. CONCLUSIONS: Usually most of the integral bite block lies within the oropharynx. It was never normal for the entire bite block to stick out of the mouth (4 SD from the mean for both men and women). The position of the integral bite block relative to the upper incisors gives valuable information during assessment of PLMA position.

Esophageal aspiration of air through the drain tube of the ProSeal laryngeal mask.

IMPLICATIONS: Two patients experienced partial upper airway obstruction while breathing spontaneously with the ProSeal laryngeal mask airway. This resulted in esophageal aspiration of air through the drain tube.

Learning to exchange an endotracheal tube for a laryngeal mask prior to emergence.

PURPOSE: To present a stepwise training method, first critiquing laryngeal mask (LM) insertion difficulty and malpositioning, then learning how to exchange an endotracheal tube (ETT) for a LM during emergence from anesthesia. METHODS: "Learning phase:" sixty adults were enrolled in a preliminary study in which ETT / LM exchange was not performed - only LM insertion difficulty and malpositioning in the presence of an oral ETT were evaluated. After induction of anesthesia and oral intubation, a classic LM size 4 was inserted using the standard recommended technique. Number of insertion attempts and fibreoptically determined malpositions were recorded. "ETT / LM exchange phase:" we performed airway exchange in 50 patients selected from our individual practices. RESULTS: "Learning phase:" the LM was satisfactorily positioned, on first attempt, in 95% of cases. With multiple insertion attempts it was possible to place the LM in all 60 intubated patients. Unsuccessful initial placement of the LM was always due to insufficient insertion depth (5%). When fully inserted into the hypopharynx, the epiglottis could be viewed fibreoptically in 13% of cases. "ETT / LM exchange phase:" the LM was inserted successfully in all 50 patients on first attempt. No complications occurred during any exchange. CONCLUSION: We found it is easy to learn how to insert a LM in the presence of an oral ETT. The most serious malposition, occurring in 5% of first attempts, was insufficient insertion depth. The only other malposition we encountered, fibreoptic visualization of the epiglottis, is not likely to result in complete airway obstruction following endotracheal extubation under anesthesia.

Epidural catheter and increased prothrombin time after right lobe hepatectomy for living donor transplantation.

IMPLICATIONS: Donor right hepatic lobectomy for the purpose of living liver transplantation may be associated with postoperative abnormalities in tests of clotting function. This study explores the possible causes and anesthetic implications of this phenomenon.

A modified intubating laryngeal mask for endotracheal tube exchange.

IMPLICATIONS: It is often necessary to change a patient's breathing tube (endotracheal tube). This can be a risky procedure. This report describes a technique for changing an endotracheal tube by using a modified "intubating laryngeal mask" (a commonly used airway and breathing device) and a fiberoptic bronchoscope.

Heparin extracorporeal LDL precipitation (HELP): an effective apheresis procedure for lowering Lp(a) levels.

Heparin-induced extracorporeal low-density lipoprotein precipitation (HELP) is based on the precipitation of apolipoprotein B (apo B) containing lipoproteins with heparin at low pH (4.85). In in vitro experiments we could show that Lp(a) is quantitatively (> 99%) precipitated from plasma by heparin in the pH range 4.6-5.2. The acute changes in Lp(a) after a single HELP-LDL apheresis were investigated in twelve patients with Lp(a) concentrations > 30 mg/dl. A single treatment caused a highly significant decrease (62%) in the concentration of Lp(a), similar to the decrease (60%) observed for LDL-cholesterol. Analysis of the data from ten patients with different apo(a) phenotypes indicated that Lp(a) is eliminated with almost 100% efficiency in the extracorporeal circulation, irrespective of apo(a) phenotype and plasma concentration. The mean rate of recovery of Lp(a) following HELP-LDL apheresis was slightly slower than that of LDL-cholesterol. Plasma Lp(a) concentrations were monitored in seven patients over 2 years. Mean Lp(a) concentrations after 2 years were lower than pre-treatment levels, indicating that repeated elimination of the lipoprotein does not lead to an induction in its synthesis. HELP-LDL apheresis should be particularly suitable for treatment of patients with elevated LDL-cholesterol levels who are also at increased coronary risk because of high Lp(a) concentrations.

Phase-plane analysis of passively mode-locked dye lasers.

A simplified model is presented of passively mode-locked dye lasers with self-phase modulation and group-velocity dispersion. The model treats pulse width and chirp as dynamical variables and follows their evolution in a pulse-width-chirp phase plane as they approach steady state. The model allows the separate dynamical effects of pulse shortening, pulse broadening, chirp buildup, and chirp decay to be examined in detail.