Effects of Circuit Leak Development Over Time and Response During Low-Flow Volume and Pressure-Controlled Ventilation.

Study Objective: To study the effects of circuit leak development over time and response during volume and pressure controlled ventilation using low flow in human patient simulator and to examine the minimum fresh gas flow needed to compensate for such a leak. Design/Setting: Prospective study using a patient Simulation Lab at Wayne State University. Measurements: A human patient simulator was endotracheally intubated. The endotracheal tube (ETT) was connected to the Datex-Ohmeda AS/3 Anesthesia machine. The tidal volume was set to 500ml in the volume controlled trial and the pressure to 6cm H2O in the pressure controlled trial. A hole was created in each experiment placed 10 cm after the inspiratory valve. Leaks were simulated from holes using 4 different needle diameters: 25, 21, 18 and 16G. A series of data were collected using fresh gas flow at 4 different flow rates (0.5, 1, 1.5 and 2 liters.min-1). Data was measured at different time points (baseline, 1, 3 and 5 minutes) in the series of simulated leaking breathing circuits. Results: Leak alarms were only detected with 16G hole at 5 minutes in the volume control mode versus leaks at 3 minutes with 16G hole and at 5 minutes with 18G hole in the pressure control mode. Conclusion: When a very low flow of 0.5 L/min is used, volume control is safer than pressure control modes.

Music and ambient operating room noise in patients undergoing spinal anesthesia.

Previous studies have indicated that music decreases intraoperative sedative requirements in patients undergoing surgical procedures under regional anesthesia. In this study we sought to determine whether this decrease in sedative requirements results from music or from eliminating operating room (OR) noise. A secondary aim of the study was to examine the relationship of response to intraoperative music and participants' culture (i.e., American versus Lebanese). Eighty adults (36 American and 54 Lebanese) undergoing urological procedures with spinal anesthesia and patient-controlled IV propofol sedation were randomly assigned to intraoperative music, white noise, or OR noise. We found that, controlling for ambient OR noise, intraoperative music decreases propofol requirements (0.004 +/- 0.002 mg . kg(-1) . min(-1) versus 0.014 +/- 0.004 mg . kg(-1) . min(-1) versus 0.012 +/- 0.002 mg . kg(-1) . min(-1); P = 0.026). We also found that, regardless of group assignment, Lebanese patients used less propofol as compared with American patients (0.005 +/- 0.001 mg . kg(-1) . min(-1) versus 0.017 +/- 0.003 mg . kg(-1) . min(-1); P = 0.001) and that, in both sites, patients in the music group required less propofol (P < 0.05). We conclude that when controlling for ambient OR noise, intraoperative music decreases propofol requirements of both Lebanese and American patients who undergo urological surgery under spinal anesthesia.

Alarming hypoxemia during one-lung ventilation in a patient with respiratory bronchiolitis-associated interstitial lung disease.

PURPOSE: To report a patient with respiratory bronchiolitis-associated interstitial lung disease (RB-ILD) who developed severe hypoxemia during one-lung ventilation (OLV). CLINICAL FEATURES: A 27-yr-old female, ex-smoker presented with productive cough and dyspnea of 18-month duration. The chest x-ray revealed diffuse abnormalities involving both lungs consisting of interstitial emphysema with irregular shadowing. Preoperative PaO(2) was 88 mmHg and pulmonary function tests showed moderate obstructive disease. The patient underwent right open lung biopsy. After induction of anesthesia, a left double lumen tube was inserted and its position verified with auscultation and fibreoptic bronchoscopy. Upon initiation of OLV, the patient developed severe hypoxemia and the PaO(2) dropped from 500 mmHg during two-lung ventilation (TLV) to 50 mmHg. Hypoxemia was readily corrected by resuming TLV. CONCLUSION: The severe hypoxemia during OLV in this patient with RB-ILD may be attributed to impaired hypoxic pulmonary vasoconstriction. Other causes were not excluded. Caution is warranted when initiating OLV in these patients.

Advancing the tracheal tube over a flexible fiberoptic bronchoscope by a sleeve mounted on the insertion cord.

UNLABELLED: The advancement of an endotracheal tube (ETT) over a flexible fiberoptic bronchoscope (FOB) is often impeded at the glottis. This is attributed to the creation of a cleft by the difference in the outer diameter of the fiberscope and the internal diameter of the tube. We designed a conical-shaped polyvinyl chloride sleeve to fit the insertion cord. This report compares the ease of advancement of the tube over a sleeved versus a nonsleeved bronchoscope. General anesthesia was induced, and one anesthesiologist introduced the FOB (a 3.8-mm Olympus LF2). Patients were randomly assigned to undergo tracheal intubation with the regular bronchoscope (25 patients) or the sleeved bronchoscope (25 patients). The FOB was advanced to approximately 1 cm above the carina. A blinded operator advanced the tube over the bronchoscope. The ETT was successfully advanced over the nonsleeved bronchoscope into the trachea on the first attempt in 64% of the patients, whereas tracheal intubation succeeded from the first attempt in 96% of patients when the sleeved FOB was used (P < 0.05). Advancement of the ETT over the fiberscope can be facilitated by using a conically shaped sleeve mounted on the insertion cord. IMPLICATIONS: This report shows that a conical sleeve mounted on the insertion cord of a fiberoptic bronchoscope will facilitate advancing the endotracheal tube into the trachea.

Variable hemodynamic fluctuations during resection of multicentric extraadrenal pheochromocytomas.

PURPOSE: To report the perioperative management and the serious hemodynamic fluctuations during manipulation of an organ of Zuckerkandl tumour in a patient undergoing resection of multicentric extraadrenal pheochromocytomas. CLINICAL FINDINGS: A 28-yr-old man who had undergone at age 12 a laparotomy for excision of an extraadrenal pheochromocytoma complained of paroxysmal headache, occasional sweating and palpitations. The arterial blood pressure (BP) was 200/100 mmHg. A 24-hr-urine collection showed catecholamines 5076 microg x 24 hr(-1) (normal < 25 microg x 24 hr(-1)). Computed tomography of the abdomen revealed two retroperitoneal masses, one adjacent to the lower pole of the right kidney and a second larger mass located at the aortic bifurcation in the region of the organ of Zuckerkandl. The patient was scheduled for excision of multiple extraadrenal pheochromocytomas. He was prepared preoperatively for two weeks with prazosin 1 mg po q six hours and propranolol 10 mg tid. Manipulation of the infrarenal tumour was uneventful but manipulation of the Zuckerkandl tumour resulted in severe hypertensive episodes with BP ranging from 200/100 to 320/120 mmHg. Surgery was interrupted temporarily; the hypertensive crisis was controlled by the infusion of sodium nitroprusside and by iv phentolamine and esmolol. CONCLUSION: In a patient undergoing resection of recurrent multicentric extraadrenal pheochromoctyomas, severe hypertensive episodes occurred during manipulation of one tumour but not during manipulation of the other. This may be attributed to inadequate preparation of the patient, difficult surgical dissection of the large Zuckerkandl pheochromocytoma, and/or secondary to an excessive and different pattern of release of catecholamines during manipulation of the Zuckerkandl tumour.