Continuous positive airway pressure/pressure support pre-oxygenation of morbidly obese patients.

BACKGROUND: Morbidly obese patients are more prone to desaturation of arterial blood during apnea with induction of anesthesia than are non-obese. This study aimed to assess the effect of low-pressure continuous positive airway pressure (CPAP) with pressure support ventilation (PSV) during pre-oxygenation on partial oxygen pressure in arterial blood (PaO2 ) immediately after tracheal intubation (post-intubation PaO2). METHODS: Forty-four adult patients scheduled for laparoscopic gastric bypass surgery were pre-oxygenated with 80% O2 for 2 min, randomized either to CPAP 5 cm H2O + PSV 5 cm H2O (CPAP/PSV, n = 22) or neutral-pressure breathing without CPAP/PSV (control, n = 22). Anesthesia was induced in a rapid-sequence protocol and the trachea was intubated without prior mask ventilation. Arterial blood gases were measured before pre-oxygenation, before induction of anesthesia, and immediately following intubation, before the first positive pressure breath. RESULTS: After pre-oxygenation, partial carbondioxide pressure was significantly lower in the CPAP/PSV group (4.9 ± 0.5 kPa), (mean ± standard deviation) than in the control group (5.2 ± 0.7 kPa) (P = 0.025). Post-preoxygenation PaO2 did not differ between the groups, but post-intubation PaO2 was significantly higher in the CPAP/PSV group (32.2 ± 4.1 kPa) than in the control group (23.8 ± 8.8 kPa) (P < 0.001). In the control group, nadir oxygen saturation was lower (median 98%, range 83-99%) than in the CPAP/PSV group (median 99%, range 97-99%, P = 0.011). CONCLUSIONS: In morbidly obese patients, low-pressure CPAP combined with low-pressure PSV during pre-oxygenation resulted in better oxygenation, compared with neutral-pressure breathing, and prevented desaturation episodes.

Simultaneous transesophageal atrial pacing and transesophageal echocardiography in cardiac surgical patients.

OBJECTIVES: To measure the effect of inserting a transesophageal echocardiography (TEE) probe on the pacing threshold of a previously inserted transesophageal pacing stethoscope, and to examine whether an indwelling pacing stethoscope influences the feasibility and image quality of a TEE examination. DESIGN: Prospective, open study using each patient as his/her own control. SETTING: Cardiac operating room of an academic medical center. PARTICIPANTS: Twenty adult patients in sinus rhythm and anesthetized for cardiac surgery. INTERVENTIONS: After induction of anesthesia and endotracheal intubation, a pacing stethoscope was inserted into the esophagus. A 5-MHz TEE probe was inserted to the four-chamber-view position. A full echocardiographic examination was performed, noting image quality, ease of probe manipulation, and loss of pacing. The pacing stethoscope was removed, and image quality assessed again. MEASUREMENTS AND MAIN RESULTS: The initial mean pacing threshold +/- 1 standard deviation (SD) was 19 +/- 8 mA (range, 10 to 37 mA). After placement of the echocardiography probe, the mean threshold had increased to 24 +/- 8 mA (range, 11 to 40 mA; p < 0.01). Loss of pacing with probe manipulation was noted in 15 of 20 patients (transient in 10 patients, permanent in 5 patients). Problems manipulating the probe because of sticking to the pacing stethoscope were noted in 10 of 20 patients. Poor image quality, resolving after stethoscope removal, was seen in two patients. CONCLUSION: Placement of a TEE probe results in a modest increase of the transesophageal pacing threshold. An indwelling pacing stethoscope frequently interferes with the ability to perform a full echocardiographic examination, and probe manipulation commonly causes loss of pacing.

Crystalloid infusion increases plasma hyaluronan.

OBJECTIVE: To investigate the changes in plasma hyaluronan concentrations after intravenous infusion of crystalloid solution in healthy subjects. DESIGN: Crossover, controlled study. SETTING: General intensive care unit in a university hospital. SUBJECTS: Twelve healthy medical students. INTERVENTIONS: Infusion of 1000 mL i.v. Ringer's acetate solution during a 40-min period. MEASUREMENTS AND MAIN RESULTS: Plasma hyaluronan concentrations were measured before, during, and after infusion, and under the same conditions without the infusion in a separate session. Hemoglobin, hematocrit, and serum albumin concentrations were measured before and after infusion. Plasma volume at baseline and the volume of Ringer's acetate retained in the intravascular space after infusion were calculated. Plasma hyaluronan values increased from baseline mean of 12 +/- 5.8 (SD) to 20 +/- 13.1 micrograms/L (p < .01) at 30 mins and 25 +/- 13.0 micrograms/L (p < .001) at 40 mins after start of the infusion. Plasma hyaluronan concentrations peaked at 10 mins after the end of the infusion: 27 +/- 13.9 micrograms/L (p < .001). No changes in plasma hyaluronan concentrations were seen during the control period. A volume of 230 to 250 mL of Ringer's acetate solution was calculated to be retained within the intravascular space. CONCLUSIONS: Infusion of crystalloid solution increases plasma hyaluronan, probably through a washout of interstitial hyaluronan by way of increased lymph flow. The consequences of the interstitial loss of hyaluronan on tissue function are unknown.

Influence of surgery on serum concentrations of hyaluronan.

OBJECTIVE: To investigate the changes in serum hyaluronan concentrations in response to surgery. DESIGN: A prospective case series evaluating serum hyaluronan concentrations before, during, and after surgery. SETTING: Operating room and recovery room of a university hospital. PATIENTS: Twelve consecutive patients undergoing vascular surgery because of arterial insufficiency of the lower extremities. MEASUREMENTS AND MAIN RESULTS: Serum hyaluronan concentrations were measured before and after induction of anesthesia and before, during, and after surgery. Routine chemical analyses of blood samples were made before and after surgery. Blood loss and fluid volumes infused were registered. Mean serum hyaluronan concentrations increased from baseline 25 +/- 10 (SD) to 36 +/- 15 micrograms/L (p < .05) during surgery, and increased further at 1 hr after the end of surgery to 52 +/- 38 micrograms/L (p < .001 compared with baseline), but had decreased nearly to baseline levels at 2 hrs postoperatively. A positive correlation was seen between peak hyaluronan concentrations and baseline serum hyaluronan levels (r2 = .73; p < .001), but no strong relationship was seen between serum hyaluronan concentrations and other parameters studied. CONCLUSIONS: Surgery is accompanied by a small increase in serum hyaluronan concentrations in humans. The major increase is seen in the postoperative period, and is probably due to increased influx of interstitial hyaluronan when the returning muscular tone activates lymph flow.

A new ventilator converter with the Siemens Servo Ventilator--evaluation in a lung model.

A ventilator converter device (Anmedic) for connecting a non-rebreathing ventilator (Servo Ventilator 900 B; Siemens-Elema) to a circle anaesthesia system was evaluated in a lung model. Recorded minute ventilation was slightly lower than dialled in most cases. We furthermore found inadequate expiratory expansion of the ventilator converter bellows, with progressive loss of tidal volume and consequently recorded minute volume, when fresh gas flow to the circle system was low (1 l.min-1), expiratory time was short (less than 40%) and respiratory obstruction was present.

Protein C, protein S and C4b-binding protein in severe infection and septic shock.

We measured concentrations of the natural anticoagulant protein C; its cofactor, protein S; and the carrier protein C4b-binding protein (C4BP), in 24 patients with severe infection and 13 with septic shock. Decreased antithrombin III levels were found in 16 of 24 infection patients and all shock patients; high thrombin-antithrombin (TAT) complexes were present in 16 of 24 infection and 12 of 13 shock patients. Protein C concentrations were significantly reduced compared to healthy blood donors, to 60 +/- 14% (infection) and 47 +/- 20% (septic shock) (mean +/- 1 SD). Total protein S levels were not reduced (119 +/- 36.7 and 88 +/- 20.0%, normal value 96 +/- 15%). Free protein S was also normal (27 +/- 9.4 and 30 +/- 8.7%, normal value 29 +/- 9%). The percentage free of total protein S was normal in shock patients (35 +/- 8.5%), but significantly reduced in patients without shock (23 +/- 5.3%). C4BP was significantly higher than normal in the latter group (135 +/- 43%), but not in the shock group (118 +/- 40%), possibly due to increased consumption. Thus, no deficiency of total or free protein S was found in these patients, who had evidence of activated coagulation but no clinical DIC.

Coagulation, fibrinolysis, and kallikrein systems in sepsis: relation to outcome.

Fatal multiple organ failure after severe infection may be related to an early activation of protease cascade systems. This study aimed to relate changes in coagulation, fibrinolysis, and kallikrein to shock and outcome. Of 53 patients with severe infection, 30 did not develop shock, 12 survived septic shock, and 11 died from organ failure after septic shock. No patient had overt disseminated intravascular coagulation. We measured 17 components of the coagulation/fibrinolysis/kallikrein pathways on admission and on the next 2 days. High values for fibrinogen, factor VIII:C, von Willebrand factor antigen, and D-dimer were seen in all patients; factor XII, prekallikrein, factor VII, antithrombin, protein C, and fibronectin were low. The patients thus appeared to be hypercoagulable. These disturbances were more pronounced in septic shock survivors, who also had low plasminogen and antiplasmin, indicating ongoing fibrinolysis. Nonsurvivors of sepsis were distinguished mainly by high plasminogen activator inhibitor values; this suggests an impaired functional fibrinolysis in fatal sepsis, with possible therapeutic implications. Cryoprecipitate infusion increased the fibronectin concentration, but did not influence the other factors studied.

Local anesthesia prevents hypertension following application of the Mayfield skull-pin head holder.

A marked hypertensive response is often seen when the Mayfield skull-pin device is applied to stabilize the head of the anesthetized patient for neurosurgery. In a prospective, blinded and randomized trial, 10 patients received an infiltration block of 0.5% mepivacaine with epinephrine 5 micrograms/ml (3 ml at each pin site) 1 min before the Mayfield holder was applied. Ten patients received normal saline and served as controls. All patients were under general anesthesia induced with sodium pentothal, fentanyl and pancuronium, and maintained with isoflurane in nitrous oxide/oxygen and increments of fentanyl. In the control group, there were significant increases in mean arterial pressure (mean increase 43%, P less than 0.001) and heart rate (15%, P less than 0.01) at 0.5, 1 and 2 min after application. In the mepivacaine group, no significant changes occurred. Infiltration of local anesthetic with epinephrine can thus safely protect against potentially dangerous increases in arterial pressure when the Mayfield holder is used.

Plasma fibronectin levels in sepsis: influencing factors.

Low plasma levels of the opsonic glycoprotein fibronectin (Fn) have been suggested to imply an impaired host defense against sepsis. However, the mechanism(s) behind Fn depletion in sepsis are obscure. We measured the Fn plasma concentration in 32 patients 12 to 24 h after the diagnosis of septic shock. Although the average plasma level was low (214 +/- 80 [SD] mg/L) compared to that of a reference material (p less than .001), the range was great (60 to 403 mg/L). A multivariate analysis of some possible influencing factors showed significant (p less than .01) positive correlations to the prothrombin level (r = .62) and the amount of insulin infused per 24 h (r = .63). The relationships to disseminated intravascular coagulation-related variables, hemodilution, and outcome were weak. Cryoprecipitate was infused into 16 patients; Fn levels increased by 52 +/- 18% of the expected increase. The most severely ill patients displayed the lowest rates of increase. The postinfusion decrease in Fn plasma concentration indicated that the plasma half-life of cryoprecipitate Fn was about 25 h. The results support the concept that decreased Fn synthesis, probably in the liver, is the major reason for Fn depletion in sepsis, rather than an increased rate of consumption.