Why HID headlights bother older drivers.

Driving requires effective coordination of visual, motor, and cognitive skills. Visual skills are pushed to their limit at night by decreased illumination and by disabling glare from oncoming headlights. High intensity discharge (HID) headlamps project light farther down roads, improving their owner's driving safety by increasing the time available for reaction to potential problems. Glare is proportional to headlamp brightness, however, so increasing headlamp brightness also increases potential glare for oncoming drivers, particularly on curving two lane roads. This problem is worse for older drivers because of their increased intraocular light scattering, glare sensitivity, and photostress recovery time. An analysis of automobile headlights, intraocular stray light, glare, and night driving shows that brightness rather than blueness is the primary reason for the visual problems that HID headlights can cause for older drivers who confront them. The increased light projected by HID headlights is potentially valuable, but serious questions remain regarding how and where it should be projected.

Monitoring gastrointestinal intraluminal PCO2: problems with airflow methods.

UNLABELLED: Gastrointestinal intraluminal PCO2 (PiCO2) information is used to assess the adequacy of trauma patient resuscitation and to assist in choosing resuscitative interventions. Therefore, determining the limitations and potential caveats of different PiCO2 monitoring systems is clinically important. This study compared two PCO2 monitoring systems. The airflow device adds and then removes air samples to quantitate PCO2, whereas the fiber-optic device does not. METHODS: Airflow (TRIP Tonometer/Tonocap) and fiber-optic (Neotrend) systems were used. In vitro they were compared with each other and to two end-tidal CO2 monitors measuring the PCO2 of humidified air containing 5% and then 10% CO2. In vivo the two systems' catheters were surgically juxtaposed in 15 dogs' stomachs; paired PiCO2 readings were taken throughout hemorrhage and resuscitation. RESULTS: In vitro, paired PCO2 values from the airflow and fiber-optic devices correlated with each other (r = 0.99) and with end-tidal values (r = 0.99 with airflow, r = 0.95 with fiber-optic). In vivo, paired values differed significantly (P < 0.0001), correlating poorly for two devices simultaneously measuring the same variable (r = 0.61). Fiber-optic PiCO2 values were higher than airflow values (mmHg +/- SEM): 69.3 +/- 4.8 vs. 61.3 +/- 5.6 at the start of hemorrhage, 141.3 +/- 12.9 vs. 87.7 +/- 7.9 by end of hemorrhage, and 104.3 +/- 9.6 vs. 82.8 +/- 7.0 by end of resuscitation for fiber-optic and airflow, respectively. CONCLUSIONS: Despite agreement in vitro, airflow methods can influence PiCO2 values obtained in vivo. Passive sensing methods used to monitor PiCO2, such as fiber-optic methods, are preferable because they neither deliver O2 to, nor remove CO2 from the local microenvironment.

Missed injuries in pediatric trauma.

Missed injuries in trauma continue to be a nemesis to the trauma surgeon. Missed injuries in adult trauma patients range in frequency from 9 to 28 per cent, with some being life threatening or permanently disabling. We report the incidence of missed injuries in pediatric trauma to be 20 per cent, in our retrospective review of 107 severe pediatric trauma patients. These missed injuries, however, were neither life threatening nor permanently disabling. We also found that mechanism of injury and patient age affected the incidence of missed injuries in our population.

The effect of peritoneal contamination on wound strength of small bowel and colonic anastomoses.

Primary bowel repair in the face of peritoneal soilage is still a controversial area. Previous studies using the rat model have demonstrated a difference in new collagen synthesis after 24 hours of peritoneal contamination. Currently, the effect of short-term fecal contamination of the peritoneal cavity on anastomotic healing and strength is not known. This study was designed to evaluate anastomotic wound strength in the face of fecal contamination during this time period. Twenty Sprague Dawley rats were randomized into two groups: twelve-hour control (n = 10) and 12-hour cecal ligation and puncture (CLP; n = 10). Both groups underwent laparotomy with either CLP (12-hour) or cecal manipulation (12-hour control). Animals were allowed to recover for 12 hours, according to their assigned groups. A second laparotomy was subsequently performed in which the CLP groups had partial cecectomy to remove the source of contamination, followed by mid-jejunal and colonic division with associated primary anastomosis. Control groups had a similar procedure without partial cecectomy. All abdomens were irrigated, and all animals received immediate postoperative antibiotics and an initial fluid bolus. Animals were recovered and received 3 days of postoperative antibiotics. On postoperative day 4, animals were sacrificed and anastomotic sites were resected. Specimens were then placed in a tensiometer and disrupted under dynamic stress. Peak load was recorded for each, and maximum standard load was calculated. Hydroxyproline content of each segment was also determined after disruption. CLP values were compared with control values using unpaired Student's t test. Statistical significance threshold was P < 0.5. There was no significant difference in maximum anastomotic wound strength or hydroxyproline content between 12-hour CLP and 12-hour control group for both small bowel and colon anastomoses. Short-term peritoneal soilage (12-hour) does not significantly effect the maximum tensile strength or hydroxyproline content of primary small bowel or colonic anastomoses in this model. This study suggests that short-term fecal contamination of the peritoneal cavity may not be a contraindication to primary bowel anastomosis.

Continuous dose furosemide as a therapeutic approach to acute respiratory distress syndrome (ARDS).

BACKGROUND: Acute respiratory distress syndrome (ARDS) is seen in a variety of clinical settings in critically ill patients. ARDS has been defined as a clinical syndrome characterized by progressive hypoxemia, tachypnea, and generalized patchy bilateral pulmonary infiltrates in the absence of cardiac failure. Furosemide has been shown to improve pulmonary gas exchange and intrapulmonary shunt in animal models of ARDS by preferential perfusion of nonedematous lung units. We hypothesized that continuous dose furosemide would improve lung injury during resuscitation from oleic acid-induced lung injury in canines. METHODS: Ten mongrel dogs were anesthetized and given intravenous oleic acid (0.1 mg/kg) to induce lung injury. Once lung injury was established (2 h) the control animals (n = 6) were continued on standard supportive therapy, and the study animals (n = 4) were started on continuous dose furosemide at 0.2 mg/kg/h. Cardiac filling pressures were maintained in all animals by infusion of isotonic saline solution. Data collected included lung injury score (LIS), cardiac index (CI), stroke volume index (SVI), pulmonary capillary wedge pressure (PCWP), urine output (UO), volume of resuscitation (VR), and pulmonary shunt fraction (Qs/Qt). Data were collected at baseline, established lung injury (2 h), and end of protocol (6 h). Data were compared between groups at various stages of the model using one-way analysis of variance with repeated measures. RESULTS: All 10 animals survived the protocol. There was no difference between the experimental and control groups at baseline or established lung injury (2 h) for CI, SVI, PCWP, or VR. There was a significant improvement in PO2/FIO2 and reduction of PEEP values in the furosemide group. There was also a statistically significant difference between experimental and control groups in LIS, Qs/Qt, and urine volumes. CONCLUSIONS: Continuous dose furosemide therapy improves LIS, PO2/FIO2, and Qs/Qt and decreases PEEP requirements in this oleic acid model of ARDS.

Car surfing: an uncommon cause of traumatic injury.

Car surfing is an infrequent cause of traumatic injuries treated by emergency physicians. This very dangerous activity can result in serious injury or death. We report 5 cases of injuries caused by car surfing seen at our hospital during 1996 and 1997. All involved head injuries after a fall from a moving motor vehicle. There were 3 male and 2 female patients, and 3 cases were fatal. Health care providers should be aware of this type of injury and support efforts to prevent it.

Resolution of experimental pneumothorax in rabbits by graded oxygen therapy.

BACKGROUND: Small pneumothoraces have been treated by observation and tube thoracostomy in asymptomatic patients. Using a rabbit model, we demonstrated previously that inspired oxygen at 60% FiO2 hastened the time to resolution of complete pneumothoraces compared with room air. The present study was designed to evaluate the use of lower levels of inspired oxygen and to establish a dose-response curve for the treatment of experimental pneumothoraces. METHODS: Forty New Zealand White rabbits were divided randomly into four groups: room air (21%) and 30, 40, and 50% FiO2. Experimental pneumothoraces were created in the rabbits, and the animals were placed in cages with the designated level of inspired oxygen. Serial chest radiographs were performed until the pneumothoraces resolved. RESULTS: Pneumothoraces treated with room air resolved in 61.65 +/- 12.30 hours. Those treated with 30% FiO2 resolved in 42.90 +/- 5.97 hours, with 40% FiO2 in 35.80 +/- 4.26 hours, and with 50% FiO2 in 33.80 +/- 4.66 hours. CONCLUSION: These results show a statistically significant (p < 0.01) dose-dependent improvement in the resolution of pneumothoraces with increasing levels of inspired oxygen. Supplemental oxygen therapy may be used to facilitate the resolution of small, uncomplicated pneumothoraces.

An evaluation of the effects of semirigid cervical collars in patients with severe closed head injury.

The use of a semirigid cervical collar has been recommended to prevent further cervical spine injury in the management of trauma patients. These cervical collars are kept on obtunded patients for prolonged periods. We assessed the incidence of cervical collar related decubiti in patients with severe closed head injury (SCHI). We also assessed the utility of fluoroscopy in clearing the cervical spine of patients with SCHI. A retrospective chart review was performed on 52 consecutive patients with SCHI at a community hospital-based Level II trauma center over an 8-month period. Thirteen of 34 patients (38%) who survived >24 hours after admission developed decubiti related to the cervical collar. The patients who developed decubiti had a significantly greater duration of cervical collar placement (21.15 +/- 0.99 days) as compared with patients who did not develop decubiti (4.42 +/- 0.79 days; P = 0.001). Eight patients had their cervical spine assessed for ligamentous injury by bedside fluoroscopy. All eight patients had early collar removal; none of these patients developed decubiti. Patients with SCHI with semirigid cervical collars kept in place for prolonged periods of time are at risk for developing decubiti. Fluoroscopy in addition to standard radiographs may "clear" the cervical spine and allow early removal of these collars.

Assessment of ventilation during the performance of a percutaneous dilatational tracheostomy: hypoventilation is not a common complication.

Percutaneous dilatational tracheostomy (PDT) is becoming an accepted cost-effective alternative to surgical tracheostomy. PDT is performed by progressive dilatation of a tracheal opening placed under bronchoscopic guidance. Case reports of hypoventilation with associated hypercarbia during the performance of PDT have raised concerns about the utility of this procedure in patients in whom hypercarbia is problematic (e.g., patients with closed head injury). In a prospective cohort analysis of 11 critically ill patients, we evaluated the effect of PDT on ventilation during and after the procedure using end tidal capnography. We found that hypercarbia does not occur during or after the performance of PDT as compared to baseline levels.

Utility of a bedside Doppler in tracking left ventricular dysfunction related to hemorrhagic shock.

Treatment of hemorrhagic shock with fluid resuscitation alone results in diastolic dysfunction as measured by peak systolic pressure/end systolic volume ratio (PSP/ESV). The purpose of this study was to test the ability of a simple Doppler device to track diastolic dysfunction in hemorrhagic shock. In this prospective, controlled crossover study, five adult swine were resuscitated from hemorrhagic shock using fluids. Diastolic dysfunction was confirmed using PSP/ESV ratio. The effect of nitroprusside and dobutamine on this diastolic dysfunction was evaluated. Data (PSP/ESV, Doppler-derived acceleration, and oxygen transport parameters) were collected at each stage of the model. Arterial pressure and oxygen transport parameters corrected to baseline values; however, the PSP/ESV and Doppler-derived acceleration failed to correct with fluid resuscitation alone. Treatment with nitroprusside and dobutamine increased oxygen transport parameters, PSP/ESV ratio, and Doppler-derived acceleration significantly. Doppler-derived acceleration tracks left ventricular dysfunction seen in hemorrhagic shock.

Free radical production by Nd:YAG laser photodisruption.

BACKGROUND AND OBJECTIVES: Plasma and cavitation bubble formation during optical breakdown in aqueous media may produce hydroxyl (*OH) radicals. The authors' objectives were to detect *OH produced by a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser photodisruptor and to determine *OH concentration in relation to laser energy. MATERIALS AND METHODS: *OH was assayed by measuring absorbance of triiodide (I3-) in a potassium iodide (KI) solution exposed to optical breakdown by an Nd:YAG laser. The concentration-dependent reduction of radical production in relation to cystamine concentration was evaluated. RESULTS: I3- concentration increased linearly with total irradiation energy and decreased exponentially with increasing cystamine concentration. *OH concentration was calculated using extinction coefficients of I3- and chemical equations relating I3- formation to *OH. CONCLUSIONS: The authors calculated that approximately 4 x 10(-12) moles of *OH are produced in a typical posterior capsulotomy of 100 mJ of total energy. This *OH concentration could produce strand breaks in approximately 0.4% of vitreous hyaluronic acid molecules, but is unlikely to produce clinical effects.

Blunt pancreatic trauma: experience at a rural referral center.

The objective of this study was to compare mechanism of injury, treatment methods, and outcome of blunt pancreas trauma patients transferred from another hospital to those of patients brought directly from the scene. A retrospective review was conducted of 6078 patients treated at a Level I trauma center from 1/1/90 to 12/31/94. Blunt pancreas injury was found in 39 (0.64%) patients (mean age, 33.2 years). Mechanism of injury included 34 (87%) motor vehicle crashes, 3 (8%) motorcycle crashes, and 2 (5%) other injuries. There were 11 transfer patients (28%), and 28 (72%) admitted directly from the scene. Eighty-two per cent of the motor vehicle crash patients were unrestrained, and 35 per cent had ethanol intoxication. Exploratory laparotomy was performed on 32 (82%); eight (25%) required repair or resection; 22 (69%) had trivial injuries, at most requiring drainage; and two (6.3%) exsanguinated. No patients required Whipple resection or pancreatiocojejunostomy. At operation, an average of 2.5 associated intra-abdominal injuries were found. Overall survival was 35 of 39 (90%). Among the patients brought directly to the trauma center, 93 per cent survived, whereas survival among transferred patients was 82 per cent (chi2 = 0.19; P = 0.66). Blunt pancreatic injuries vary in severity, but radical resection is rarely required. Lack of safety restraint and ethanol use are major risk factors. Despite the high likelihood of associated injuries, survivability is high. No difference in outcome was seen between directly admitted and transferred patients.

Changes in oxygenation and compliance as related to body position in acute lung injury.

Body positioning during mechanical ventilation for acute lung injury has not been studied in a detailed manner. We evaluated the relationship between oxygenation, compliance, and body position during mechanical ventilation of patients with acute lung injury (ALI). Sixteen patients on mechanical ventilation with a diagnosis of ALI (partial pressure of oxygen/fraction of inspired oxygen <300 and no clinical evidence of congestive heart failure) were prospectively studied. Each patient was placed in a supine position followed by a 30 degrees head elevation and a 45 degrees head elevation. Data obtained in each position (after a 45-60 minute equilibration time) included static pulmonary compliance and partial pressure of oxygen from arterial blood gas sampling. Oxygenation is not improved and compliance is adversely affected by upright body positioning as compared to the supine position in patients receiving mechanical ventilation for ALI.

Comparison of nonbronchoscopic techniques with bronchoscopic brushing in the diagnosis of ventilator-associated pneumonia.

OBJECTIVE: To determine the diagnostic accuracy of quantitative cultures obtained via nonbronchoscopic protected specimen brushing (PSB) and nonbronchoscopic bronchoalveolar lavage (BAL) compared with quantitative cultures obtained by bronchoscopic PSB in surgical patients suspected of ventilator-associated pneumonia. DESIGN: Prospective, crossover controlled study of 15 ventilated surgical intensive care unit patients in a university teaching hospital. METHODS: Fifteen consecutive ventilated patients suspected of ventilator-associated pneumonia on the basis of leukocytosis, purulent sputum, and appearance of chest roentgenogram were enrolled. All patients underwent nonbronchoscopic PSB and BAL followed by bronchoscopic PSB. The duration of each procedure was noted. Culture results were considered positive only if greater than 10(4) colony forming units (CFU) per milliliter were present. MAIN RESULTS: Perfect concordance was noted between bronchoscopic PSB and nonbronchoscopic BAL (kappa = 1.0). The concordance between bronchoscopic PSB and nonbronchoscopic PSB was 93% ((kappa = 0.86). The nonbronchoscopic procedures were performed in significantly less time than the bronchoscopic procedure. CONCLUSION: Nonbronchoscopic PSB and BAL provide similar microbiologic data to bronchoscopic PSB in the diagnosis of ventilator-associated pneumonia while shortening procedure time significantly.

A novel method for measuring saccade profiles using the scanning laser ophthalmoscope.

Most existing techniques for accurately measuring angular eye position vs time during a saccade (the saccade profile) need either contact to the eye or are restricted in time resolution. In this paper we introduce a new noninvasive method, with high spatial and temporal resolution, for determining saccade profiles using a scanning laser ophthalmoscope (SLO). This method uses the fact that images of a moving object taken with the SLO are not blurred (as are images from video cameras) but show a tilt with respect to images of the same stationary object. A mathematical framework is given that allows determination of a saccade profile from a restricted number of consecutive SLO video fields of the fundus during a saccade. The angular resolution obtained by this method is below 0.1 deg, and the maximum time resolution near 1 msec. Measured saccade profiles could be well approximated by a gamma function, the first derivative of which yields the saccade velocity profile. Measurements of peak saccade velocity as a function of saccade amplitudes (main sequence) using our method show good agreement with results obtained by other authors.

Rectal pH measurement in tracking cardiac performance in a hemorrhagic shock model.

OBJECTIVE AND DESIGN: We evaluated the utility of rectal mucosal pH measurement for tracking cardiac performance in hemorrhagic shock as compared with gastric tonometry. MATERIALS AND METHODS: Hemorrhagic shock was induced in five adult swine to a mean arterial pressure of 45-65 mm Hg. Hypotension was maintained for 30 minutes, resuscitation was accomplished with the shed blood and lactated Ringer's solution (3x blood volume). Gastric tonometry, rectal pH, and oxygen transport data were obtained at baseline, 0, and 30 minutes after onset of hypotension and after resuscitation. RESULTS: Intramucosal pH readings from gastric tonometry and rectal mucosal pH both showed a significant change from baseline to 0 and 30 minutes after onset of hypotension. Data after resuscitation were found to be statistically the same as baseline values. CONCLUSIONS: Rectal mucosal pH tracks cardiac performance as well as does gastric tonometry in hemorrhagic shock without as many limitations.

Load-independent left ventricular function in a hemorrhagic shock model.

Load-independent left ventricular (LV) function has been recently shown to be reversibly depressed in septic shock. The peak systolic pressure to end systolic volume ratio (PSP/ESV) is a load independent measure of LV function. We evaluated PSP/ESV in a porcine model of hemorrhagic shock. Hemorrhagic shock was induced in five adult swine by arterial bleeding to a mean arterial pressure of 45-65 mmHg. This hypotension was maintained for 30 min, and then each animal was resuscitated to baseline mean arterial pressure using shed blood and crystalloid solution. Data (echocardiographically derived ejection fraction and oxygen transport parameters) were collected at baseline, after 30 min of hypotension and postresuscitation. Although the cardiac index, a marker for systolic function, and the mean arterial pressure, as well as oxygen delivery and consumption returned to baseline levels, the PSP/ESV ratio remained low despite adequate fluid resuscitation. This model provides a reproducible hemodynamically stable cardiac dysfunction associated with hemorrhagic shock.

Perforated jejunal diverticula: an analysis of reported cases.

We recently encountered two cases of perforated jejunal diverticula. We analyzed the data from all available cases of perforated jejunal diverticula, including our two cases. Our purpose was to increase awareness of this rare clinical entity as a cause of abdominal pain. An extensive literature review using Medline from its inception in 1972, and a manual review of all previously published reports was performed. Data collected included age, gender, length of symptoms from history and physical exam, operative findings, type of operation, and outcome (survival). Data analysis was performed using student's t test and multivariate analysis. Survival was not influenced by gender or type of operation. When the reports documented the number of diverticula present in the area of perforation (22 cases) a majority (19/22) had multiple diverticula. Perforated jejunal diverticula are a rare clinical entity in which age, type of operation, and gender does not influence outcome, but a longer duration of symptoms before operation trended towards a worse outcome. This clinical diagnosis should be entertained as part of any evaluation of abdominal pain.