The failure of negative pressure rewarming (Thermostat) to accelerate recovery from mild hypothermia in postoperative surgical patients.

UNLABELLED: The Thermostat device (Aquarius Medical Corp., Phoenix, AZ) is used in a new technique to accelerate recovery from hypothermia by mechanically distending blood vessels in the hand, thereby increasing transfer of exogenous heat to the body core. We evaluated the use of the Thermostat device in patients with mild postoperative hypothermia (< 36 degrees C). We studied adult patients undergoing elective surgery, general anesthesia, and neuromuscular blockade. Patients with an initial postoperative tympanic membrane temperature < 36 degrees C were randomized into two groups: 1) Thermostat, which consisted of a hypothermia warming mitt/seal and thermal exchange chamber for 60 min, and 2) conventional treatment, which consisted of warm blankets and/or radiant heat. Of the 191 patients enrolled, 60 (31%) developed hypothermia and were randomized to receive the Thermostat (n = 30) or conventional methods (n = 30). Fourteen patients in the Thermostat group and 17 patients in the conventional group rewarmed to 36 degrees C before discharge from the recovery room (P is not significant). There were no differences in vital signs, rewarming time, time to discharge from the recovery room, or postoperative temperature between groups. We conclude that patients with mild postoperative hypothermia rewarmed in a similar fashion, regardless of whether the Thermostat or conventional methods were used. IMPLICATIONS: We found that a commercially available negative pressure rewarming device (Thermostat; Aquarius Medical Corp., Phoenix, AZ) was not effective in accelerating rewarming in postoperative hypothermic surgical patients after general anesthesia.

Taping methods and tape types for securing oral endotracheal tubes.

PURPOSE: To evaluate tapes and taping methods with respect to the minimum force required to dislodge endotracheal tubes (ETTs). METHODS: A simulated face model consisting of a section of PVC pipe was used. The ETT was attached to a piezo-electric force transducer and pullout force was manually applied in a vertical, right or left direction. Five tape types were tested: Curity, Leukosilk, Hy.tape, Leukopore, and Transpore, Seven taping methods were used to secure the ETT. The methods differed with respect to tape width and whether the tape was split along its longitudinal axis. Each taping condition was replicated 20 times (7 methods x 5 tapes x 3 directions) for a total of 2100 pullout tests. RESULTS: Minimum forces to dislodge ETTs were higher (P < 0.05) with Curity tape (mean +/- SD; 135 +/- 75 N) than with the other tapes (Leukosilk: 93 +/- 51 N, Hy.tape: 78 +/- 34 N, Leukopore: 47 +/- 32, and Transpore: 37 +/- 23 N). The most secure taping method was achieved by taping the ETT, using 2.5 cm wide Curity tape, in a circumferential fashion to both the upper and lower borders of the simulated mouth opening, and reinforcing these tapes with two strips applied longitudinally across the borders of the mouth opening (method 7). Taping methods which involved splitting the tape along its longitudinal axis resulted in lower minimal pullout forces whenever the pullout force was directed towards the side of attachment (P < 0.05 vs right and vertical direction). CONCLUSION: There are differences in ETT pullout forces and mechanisms of dislodgement depending on taping method and tape type.

Evaluation of different methods of securing intravenous catheters: measurement of forces during simulated accidental pullout.

The purpose of the study was to compare the relative effectiveness of several combinations of tapes and taping methods with respect to the force required to pull out intravenous catheters. A simulated forearm model consisting of a section of firm PVC pipe was used for the first and second series of experiments. In the third experiment, one method of taping catheters was compared in the PVC model and in volunteers. Pullout forces were measured with a force transducer and recorded on paper. In the first experiment, catheters secured with Curity tape resisted pullout to a greater extent than those with Transpore tape and provided approximately twice the force advantage (P < 0.05). In the second experiment using Curity tape, minimum forces to dislodge the catheters were (means +/- SD) 53 +/- 13, 82 +/- 13, 113 +/- 29, 124 +/- 24, 176 +/- 29 and 141 +/- 46 N, for methods 1-6, respectively. In the third series, the minimum pullout forces were higher for Curity than with Transpore tape for both the human and simulated PVC forearm surfaces (63 +/- 11 and 55 +/- 12 N vs 52 +/- 7 and 44 +/- 12 N, P < 0.01), and the pullout forces were higher for the simulated vs. the human skin surface for both tape types (P < 0.01). Compared with Curity tape, Transpore tape was more likely to fail by tape fracture in both the simulated and human skin surfaces (P < 0.05). The data suggest that there are important differences in pullout forces and mechanisms of dislodgement depending on taping method and tape type.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of tape type and of skin preparation on the force required to dislodge angiocatheters.

The study evaluated the effects of different techniques used to secure intravenous (i.v.) catheters. An angiocatheter attached to standard i.v. tubing was taped to human forearm using a standard taping method. A calibrated piezoelectric force transducer was attached to the i.v. tubing. The force applied along the longitudinal axis to pull out the taped catheter was measured and recorded on paper. Three tape types, Curity, Leukopor and Transpore, were evaluated alone, with benzoin skin pretreatment and with mastisol pretreatment. A randomized 3 x 3 block design with 20 replications per block was utilized, and a total of 180 pullout tests were performed on two adult volunteers. Without pretreatment, the forces required to dislodge catheters were (means +/- SEM) 46 +/- 2, 37 +/- 2 and 38 +/- 2 Newtons for Curity, Leukopor and Transpore tape, respectively. Corresponding values for mastisol pretreatment (64 +/- 1, 64 +/- 3 and 52 +/- 3 Newtons) were greater (P < 0.05) for each tape compared with benzoin (54 +/- 3, 53 +/- 2 and 40 +/- 2 Newtons) and no pretreatment. The most frequent failure mode for Transpore tape was by tape fracture, for Curity tape was by separation from the skin of tape and catheter as a single unit, and for Leukopor tape was by catheter separation while tape remained attached to skin (P < 0.001). The data suggest that the application of mastisol prior to taping i.v. catheters with Curity or Leukopor tape helps to minimize the risk of accidental dislodgement.

Dye circulation times during cardiac arrest.

Dye dilution curves have been used to calculate cardiac output under conditions of normal circulation. Unfortunately, these curves cannot be integrated easily to determine cardiac output under the low flow states of CPR. The time to initial dye appearance (circulation time), may be useful in judging relative changes in flow when studying experimental resuscitation techniques. The purpose of this study was to investigate the relationship between dye circulation times and other hemodynamic measures during CPR. Repeated measurements of coronary perfusion pressure, dye circulation times, blood gases, and end-tidal CO2 (ETCO2) were made in dogs undergoing CPR. Dye circulation time was significantly associated with the systolic, diastolic, and coronary perfusion pressures. The correlation between circulation time and ETCO2 was -0.70 (P less than 0.0001). There was no correlation with the arterial-venous PO2 gradient. There were significant correlations between the circulation time and both the A-V PCO2 and the A-V pH gradients. We conclude that dye circulation times may be used to gauge relative changes in blood flow during CPR, particularly in laboratory investigations involving repeated measurements.

Chest wall acceleration and force measurements in simulated manual and mechanical cardiopulmonary resuscitation.

During CPR, the dynamics of the chest compression process play a major role in determining the outcome of the resuscitation effort. To quantify chest wall motion during CPR, a number of important variables must be determined, including maximum downward acceleration and velocity of the chest wall, time during which the wall is held in compression, and maximum depth and rate of chest compression. In this study, miniature accelerometers were used to record chest wall motion during simulated CPR with standard training manikins. One series of CPR tests included force measurements from a three-dimensional force platform placed under the manikin. The results of this investigation showed that American Heart Association (AHA)-certified rescuers are able to produce a consistent pattern of chest wall displacement during a manikin training exercise, and only small differences in displacement recordings are found when comparing one certified rescuer to another. Any given rescuer will usually generate a consistently repeatable acceleration pattern during CPR. However, these cyclical acceleration patterns differ markedly when comparing different certified rescuers. Mechanical CPR with a standard device produced larger peak accelerations than manual CPR. However, the maximum downward velocity was usually higher with manual CPR. In comparison with trained but clinically inexperienced individuals, rescuers with extensive in hospital experience produced relatively larger downward accelerations, longer "hold" times with the chest in compression, and maximum chest displacements that exceeded the current AHA recommendations. Measurements of the force transmitted through the manikin to a force platform clearly indicated the presence of a "hold" phase (if present) and the existence of large force components in the horizontal plane.

Flow-monitoring system for high-frequency ventilation.

With the addition of appropriate logic circuitry and a single-board microcomputer, a thermistor flowmeter becomes a clinically useful ventilation monitor. The microcomputer calculates upper and lower reference (voltage) levels from the baseline (normal) flow signal generated by the thermistor bridge. If the flow signal fails to pass repetitively through one or both of these reference levels, visual and audio alarms are generated. Tests performed with both high-frequency (3 Hz) and low-frequency (0.2 Hz) ventilator systems show the usefulness of this system in sensing a variety of malfunctions, including endotracheal tube occlusions, leaks, changes in flow or tidal volume, and hose disconnects.

Beat frequencies in high-frequency positive-pressure ventilation.

Amplitude modulation of the waveforms of several cardiovascular variables was investigated during high-frequency (1.3 to 3.3 Hz) positive-pressure ventilation (HFPPV). The amplitude modulation of the pulmonary artery pressure wave was most prominent and its beat frequency (BF) was equal to the difference between the heart rate and the ventilation rate. Spectral analysis of the pulmonary artery pressure demonstrated well-defined peaks associated with the BF. No significant physiologic changes in either cardiovascular or pulmonary function were attributable to the presence of the beat phenomenon.

Transferrin loss into the urine with hypochromic, microcytic anemia.

Anemia developing during the course of chronic renal disease is a frequent complication often necessitating periodic transfusion therapy. A number of etiologic factors have been implicated, including decreased production of erythropoietin; decreased erythrocyte life span secondary to uremia and splenomegaly; increased bleeding tendency due to platelet dysfunction; and acquired lack of folic acid and iron. This paper concerns the problem of acquired hypochromic, microcytic anemia secondary to heavy urinary loss of iron and transferrin in a child with the nephrotic syndrome. The patient had microcytic, hypochromic anemia with serum iron, 12 mug. per dl. and a serum iron-binding capacity of 12 mug. per dl. There was no evidence of major bleeding resulting in a chronic hemorrhagic anemia. Urinary iron was 64 mug. per dl., with a urinary iron-binding capacity of 366 mug. per dl. Renal biopsy showed mesangio-proliferative glomerulonephritis. Evaluation of any patient with the nephrotic syndrome should include careful analysis of the various serum and urinary proteins and determination of serum and urinary iron and iron-binding capacity. This information would offer a more precise evaluation of the underlying cause of anemia in the nephrotic patient who may develop urinary loss of iron and transferrin and subsequent hypochromic, microcytic anemia.

Adenosquamous carcinoma of the liver.

A rare case of adenosquamous carcinoma of the liver is reported. An 85-year-old white man presented with a 6-month history of weight loss and an enlarged liver. A biopsy demonstrated a squamous cell carcinoma which was presumed to be metastatic with an occult primary. At autopsy, the liver was partially replaced by a focally cystic tumor. Histologically, the neoplasm demonstrated both malignant squamous and glandular contradistinctionmponents as well as foci of transition between the two. This is in co to the 5 previous reported cases of primary hepatic squamous cell carcinomas or tumors containing a squamous component. It is suggested that this neoplasm arose from malignant transformation of squamous metaplasia in a pre-existing cholangiocarcinoma.