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Biomedical subjects

S C Dronen

Publications and source records attributed to S C Dronen.

At least 37 records · Page 2Linked to original sources
PubMed1989

A continuous hemorrhage model of fatal hemorrhagic shock in swine.

We studied the effect of bleed rate on survival time and hemodynamics in a continuous hemorrhage model of fatal hemorrhagic shock in lightly anesthetized swine. Fasted immature swine (12-16 kg) were sedated with intramuscular (i.m.) ketamine, endotracheally intubated, anesthetized with halothane (0.75%), nitrous oxide, and oxygen, and then prepared for experimentation by placement of a pulmonary artery thermodilution catheter, femoral arterial and venous catheters, and by splenectomy. After instrumentation, halothane was discontinued and sedation was maintained with nitrous oxide and intravenous lorazepam. Thirty minutes later, the animals were bled continuously at 1.0 ml/kg per min (n = 8, Group I) or 1.25 ml/kg per min (n = 8, Group II) by a roller pump connected to the femoral arterial catheter. Hemodynamic parameters were recorded every 15 min until death occurred. Mean survival time was 50.2 +/- 3.0 min in Group I and 39.8 +/- 3.2 min in Group II (P less than 0.001). There was a stepwise decrease in blood pressure and cardiac index consistent with progressive hemorrhagic shock. This model results in reproducible survival times with small standard deviations. Although the animals are lightly anesthetized and the experiments are performed acutely, the hemodynamic responses and survival times observed are similar to those reported in previous studies of chronically instrumented, unanesthetized swine. This model may be more practical than unanesthetized, chronically instrumented swine models for evaluating the effects of various interventions on survival time and hemodynamics in acute hemorrhagic shock.

Animals↗
PubMed1989

Intravenous fluid therapy in the prehospital management of hemorrhagic shock: improved outcome with hypertonic saline/6% Dextran 70 in a swine model.

The small quantities of 7.5% hypertonic saline (HTS) in 6% Dextran 70 (DEX 70; Travenol Laboratories, Deerfield, IL) required to produce marked improvement in tissue perfusion may make it an ideal solution for the prehospital management of hypotensive trauma patients. This study shows that the initial treatment of porcine hemorrhagic shock with 7.5% HTS/6% DEX 70 results in significantly improved hemodynamics and higher survival rates than those seen in animals treated with normal saline. These results are very encouraging and dictate the need for evaluation in human trials.

Animals↗
PubMed1989

Aeromedical transport of patients with post-traumatic cardiac arrest.

Patients experiencing cardiac arrest secondary to trauma make up 8% to 15% of air ambulance scene flights in reported series. Our study examined the role of aggressive physician intervention at the accident scene in conjunction with rapid air transport to a trauma center in reducing the mortality after post-traumatic cardiac arrest. We retrospectively studied 67 patients who experienced cardiac arrest before the arrival of the flight team. Fifty-eight patients were victims of blunt trauma, and nine sustained penetrating trauma. Forty-seven patients were transported to the base hospital; 20 were pronounced dead at the scene after resuscitation attempts were made. Six patients developed a pulse and blood pressure and were hospitalized; none survived to hospital discharge. Review of autopsy data revealed that the majority of patients had head or thoracoabdominal injuries or both that were incompatible with life. We conclude that physician intervention at the scene and rapid aeromedical transport are not likely to improve mortality after traumatic cardiac arrest.

Adolescent↗
PubMed1989

Early versus late fluid resuscitation: lack of effect in porcine hemorrhagic shock.

The benefit of IV fluid therapy in the prehospital management of hemorrhagic shock is unproven. We used a reproducible, lightly anesthetized model of porcine continuous hemorrhage to evaluate the usefulness of pre-hospital IV fluid therapy. Incorporated into the model were time delays associated with ambulance request and dispatch, patient evaluation and treatment, and transport to the hospital in the average urban prehospital care system. Treatment occurred concurrently with hemorrhage. Twenty-eight immature swine (15 to 20 kg) were bled at a rate of 1.25 mL/kg/min. Animals in the prehospital IV group (n = 14) received fluid resuscitation at 1 mL/kg/min beginning 20 minutes after initiation of hemorrhage; those in the in-hospital IV group (n = 14) received fluid at a rate of 3 mL/kg/min beginning 35 minutes after hemorrhage. Both groups received blood and saline at 3 mL/kg/min 45 minutes after hemorrhage began, and both groups had hemorrhage controlled 25 minutes after simulated hospital arrival. Survival was 57% in both groups, and there were no statistically significant differences seen in measured hemodynamic or biochemical parameters. We conclude that early administration of IV normal saline has no effect on hemodynamics or survival in this porcine hemorrhagic shock model simulating an urban prehospital care system.

Animals↗
PubMed1989

The safety of fentanyl use in the emergency department.

Fentanyl citrate is a synthetic narcotic 1,000 times as potent as meperidine. It produces minimal hemodynamic effects and is characterized by a rapid onset of sedation and analgesia, a relatively short duration of action (approximately 30 to 40 minutes), and rapid reversal with opiate antagonists. These properties make fentanyl an ideal drug for emergency department use. The safety of fentanyl use in an adult ED population has not previously been studied. We retrospectively reviewed the charts of 841 patients who received fentanyl at the University of Cincinnati Center for Emergency Care between January 1985 and June 1988. The study population included 497 (59%) men and 344 (41%) women, with an average age of 33 years. The average dose of fentanyl was 180 micrograms (range, 25 to 1,400 micrograms). Six patients (1%) experienced mild side effects including nausea (one), emesis (two), urticaria (one), and pruritus (two). Nine patients (1%) developed more serious complications including six cases (0.7%) of respiratory depression and three cases (0.4%) of hypotension. Two of 183 patients (1%) who received midazolam and two of nine patients (22%) who received haloperidol developed respiratory depression. Four of the six patients with respiratory depression and two of the three patients with hypotension were intoxicated. All of the complications were transient, and none resulted in hospitalization. We conclude that fentanyl is a safe drug for use in the ED. To maximize safety, we recommend careful dosing and titration, close patient monitoring, and the availability of naloxone hydrochloride and resuscitation equipment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Prehospital use of neuromuscular blocking agents in a helicopter ambulance program.

We prospectively studied the use of succinylcholine chloride and pancuronium bromide by the physician/nurse flight team of our hospital-based helicopter ambulance service. Patients who received these agents at the scene of an accident (prehospital group, n = 39) were compared with patients who were paralyzed by the flight team in the emergency department of transferring hospitals (control group, n = 35). By protocol, succinylcholine was used primarily for endotracheal intubation and pancuronium for prolonged paralysis after endotracheal intubation. Seventy-four patients received one or both agents. Overall, 61 of 74 patients had intracranial pathology as their primary diagnosis (82%). Endotracheal intubation was the primary indication for paralysis in the majority of patients (67 of 74), although intracranial pressure control, ventilation, agitation control, and seizure control were frequent secondary indications. Prior intubation attempts had failed in 40 of 74 patients (54%). After paralysis, intubation was successful in 68 of 71 patients (96%). Serious complications (ie, dysrhythmia requiring drug therapy) occurred in three patients but resolved with appropriate therapy in each case. Minor complications (ie, dysrhythmia not requiring drug therapy, histamine flush, infiltrated IV line) occurred in 18 patients. There was no significant difference in successful intubation or complication rate between the prehospital and control group. Paralysis allowed airway stabilization in a significant number of critically ill patients who could not otherwise be endotracheally intubated, with a lower incidence of complications than has been previously reported for ED patients. These results suggest that neuromuscular blocking agents can be used safely and effectively at accident scenes by a physician/nurse team.

Adolescent↗
PubMed1988

Succinylcholine-assisted intubations in prehospital care.

Although endotracheal intubation is considered the optimal technique for airway management in critically ill patients, performance of this task in the prehospital setting is at times difficult due to increased masseter muscle tone, vocal cord spasm, or patient combativeness. Use of short-acting paralyzing agents by paramedics to facilitate intubation in these situations is an uncommon practice. We report the recent experience of an emergency medical service system that has used succinylcholine (SUX) for more than ten years. We reviewed prehospital patient intubations for two years; 215 patients were intubated by paramedics without the use of SUX and 95 patients were intubated with the use of SUX. The patient group intubated with SUX was characterized by a greater percentage of women (48% vs 35%; P less than .05), a higher mean Glasgow Coma Scale score (8.6 vs 3.4), fewer intubations for cardiac arrest (3% vs 81%), and more hospital survivors (58% vs 24%; P less than .005). The groups were not different with respect to mean age or frequency of trauma. Paramedics chose to use SUX in 69% of nonarrested patients requiring intubation. SUX-assisted intubation was used most often for the indications of airway protection and respiratory distress. Review of hospital records showed no difference between the groups for frequency of either aspiration pneumonia or mechanical ventilation in patients surviving to hospital admission. No patient receiving SUX required emergency cricothyrotomy, nor was esophageal intubation noted in either group. Succinylcholine-assisted intubation was used safely and selectively by the paramedics in this EMS system to permit airway control and ventilation of patients with more difficult intubations.

Adolescent↗
PubMed1988

The effect of ethanol on survival time in hemorrhagic shock in an unanesthetized swine model.

Controversy exists as to whether ethanol intoxication causes exaggerated hypotension or increased mortality during hemorrhagic shock. Previous studies have used anesthetized animals. This limits data interpretation as anesthetic agents, particularly pentobarbital, have well-documented effects on hemodynamics and the response to hemorrhage. We studied the effects of moderate ethanol intoxication on blood pressure and survival time during fatal hemorrhagic shock in unanesthetized swine. Immature female swine weighing 15 to 20 kg were splenectomized and instrumented with chronic indwelling aortic catheters, right atrial catheters, and gastrostomy tubes. Four to seven days later the unanesthetized animals underwent hemorrhagic shock. Thirty minutes prior to the start of hemorrhage, the experimental group (n = 8) received 3 mL/kg of 100% ethanol mixed as a 1:3 solution with water through a gastrostomy tube. The control group (n = 8) received an equal amount of water. The distal aortic catheter was connected to a roller pump and blood was removed at a rate of 1 mL/kg/min until the animal died. Arterial pressure, heart rate, lactate ethanol and glucose levels, hematocrit, and arterial blood gases were measured in both groups at baseline and every 15 minutes thereafter. A mean ethanol level of 1,500 to 1,700 micrograms/mL was produced in the experimental group from baseline through 60 minutes. Data were analyzed using Student's two-tailed t test, and analysis of variance for repeated measures. There was no significant difference in survival time between the control (63.1 +/- 2.8 min) and ethanol (59.9 +/- 5.9 min) groups. Systolic blood pressure was significantly lower in the ethanol group after 15 minutes of hemorrhage (81 +/- 22 to 59 +/- 14 mm Hg, P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Hemodynamic and metabolic effects of ethanol in canine hemorrhagic shock.

Ethanol has been reported to cause myocardial suppression, exaggerated hypotension, and increased mortality in various animal models of hemorrhagic shock. Previous studies have not used a fixed-volume graded hemorrhage model and have not monitored cardiac output or metabolic parameters such as serum glucose and lactate levels. We studied hemodynamic and metabolic changes after administration of ethanol in a 50% graded hemorrhage model in conditioned, anesthetized beagles after orogastric ethanol loading. The hemorrhage was done over a 60-min period followed by a 90-min stabilization period. The ethanol group (n = 6) had significantly higher heart rates during the stabilization period. Mean arterial pressures (MAP) were lower in the ethanol group during the stabilization period. The change from baseline MAP 30 min after hemorrhage was -31% in the control group and -53% in the ethanol group (P less than .05 using Wilcoxon ranked sum test). Serum glucose and lactate levels were higher in the ethanol group. These results indicate that ethanol impairs hemodynamics and alters glucose and lactate metabolism in dogs in the fixed-volume graded hemorrhage model. The effect of these changes on morbidity and mortality remains to be determined.

Animals↗
PubMed1988

Effects of splenectomy on hemodynamic performance in fixed volume canine hemorrhagic shock.

Studies of canine hemorrhagic shock commonly use a splenectomized fixed-pressure model. Splenectomy is recommended in this model to avoid variable degrees of autotransfusion that reduce the reliability of mortality estimates and blood volume measurements. The effects of splenectomy on a non-lethal fixed-volume canine hemorrhage have not been established. The purpose of this study was to investigate cardiovascular and biochemical effects of splenectomy in fixed-volume canine hemorrhagic shock. Nineteen beagles of uniform size and weight were bled 50% of their estimated blood volumes over 1 hr and then left without therapeutic intervention for a 90 min stabilization period. Arterial blood pressure (MAP), central venous pressure, pulmonary artery pressure, heart rate (HR), cardiac output, glucose, lactate, arterial and mixed venous blood gases, and hematocrit (HCT) were measured at regular intervals. Cardiac index (CI), stroke volume, and oxygen saturation (O2SAT), delivery (O2DEL) and consumption (O2CON) were calculated at these intervals. Results from ten control animals were compared to those from nine animals that had been splenectomized 2 wk prior to hemorrhage. During the hemorrhage period, there were no significant differences observed between groups for HR, MAP, or O2DEL. CI remained higher (P less than 0.025) and HCT lower (28.9 +/- 4.7 vs 39.8 +/- 4.5) (P less than 0.001) in splenectomized animals. Immediately following hemorrhage there were no significant differences in the mean values for HR, CI, MAP, or serum lactate. O2DEL however, was significantly higher in control animals (P less than 0.05). During stabilization MAP, CI, and O2DEL rose while HCT fell in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Effects of dichloroacetate in spinal stroke in the rabbit.

High levels of brain lactate may contribute to cellular death and dysfunction in acute cerebral ischemia. Although sodium dichloroacetate (DCA) has been shown to lower brain lactate in incomplete cerebral ischemia, functional outcome has not been assessed with DCA. We examined the effects of DCA treatment on functional neurologic outcome using a previously developed model for "spinal stroke" in the rabbit. Thirty male New Zealand white rabbits weighing 1.3-2.8 kg were studied. After anesthesia with 15-40 mg/kg pentobarbital IV, a laparotomy was performed and the aorta exposed. A metal clamp was placed on the aorta just distal to the left renal artery for 20 minutes and then removed. The abdominal wound was closed in two layers. Animals then received either 2cc normal saline (n = 15) or 300 mg/kg DCA in 2cc normal saline (n = 15) over 10 minutes. The animals were returned to their cages when awake and were examined at 24 hours, 48 hours, and 72 hours for neurologic assessment. The exams were performed by a blinded examiner who was unaware of the treatment given. A three point ambulatory score (0 = can't walk, 1 = walk but not hop, 2 = hopping) and a two point activity score (0 = inactive, 1 = active) were used. At 24 hours, 67% of the DCA-treated animals were actively moving about compared to only 27% of the controls (P = 0.03; Fisher Exact Test). Ten of fifteen control animals were unable to walk, while only five of fifteen DCA-treated animals were unable to walk (P = 0.07). Sixty percent of the DCA animals were able to hop compared to 27% of controls (P = 0.06). These results suggest that DCA can reduce morbidity from spinal cord ischemia in the rabbit.

Acetates↗
PubMed1987

Naloxone does not improve hemodynamics following graded hemorrhage in a canine model.

Two recent studies have demonstrated no improvement in hemodynamic parameters or survival following naloxone administration in hemorrhagic shock. This finding is in contrast to those of earlier studies, which consistently demonstrated a beneficial effect. The current study evaluated naloxone's ability to improve hemodynamics when administered following a fixed-volume hemorrhage, during a period of partial hemodynamic compensation. Thirteen conditioned beagles were anesthetized with pentobarbital (25 mg/kg intravenously), endotracheally intubated, and instrumented with a femoral arterial line and a pulmonary artery thermodilution catheter. Animals were then subjected to an estimated 50% graded hemorrhage (45 ml/kg) over one hour. Following hemorrhage, animals were observed for 90 minutes, then reinfused with shed blood over 30 minutes, and finally observed for an additional 60 minutes. Six animals received naloxone (2 mg/kg intravenously) 30 minutes after completion of hemorrhage and then 2 mg/kg/hr for the duration of the study. Seven control animals received an equivalent volume of saline. Heart rate, mean arterial pressure, central venous pressure, cardiac output, arterial and mixed venous blood gases, and serum lactate level were measured at regular intervals throughout the study. Cardiac index and systemic vascular resistance index were calculated at the same intervals. Overall, there were no statistically significant differences in the mean data values for mean arterial pressure, cardiac index, systemic vascular resistance index, or lactate, although lactate values were consistently higher in the naloxone group (two-tailed independent Student's t test). We conclude that naloxone does not significantly improve hemodynamics when administered after a fixed-volume hemorrhage.

Animals↗
PubMed1987

A comparison of blind nasotracheal and succinylcholine-assisted intubation in the poisoned patient.

In the patient obtunded by drug intoxication, the optimal method of airway protection prior to gastric emptying is not clear. We report a prospective randomized trial of two methods of intubation in this patient population. Fifty-two overdose patients with Glascow Coma Scale scores of 12 or less were intubated either orotracheally after succinylcholine administration or nasotracheally. Success rate, time to intubate, difficulty, and complications of intubation were compared for the two groups. We found a success rate of 100% (23 of 23) for succinylcholine assisted intubation (SAI) versus 65% (19 of 29) success with blind nasotracheal intubation (BNI). Mean time to intubate was 64 seconds and 276 seconds in the SAI and BNI groups, respectively. Eighty-six percent (19 of 22) of patients were intubated successfully in less than 120 seconds in the SAI group versus 37% (10 of 27) in the BNI group (P less than .005). In the SAI group, the mean number of attempts was 1.3 per patient, (range, one to three) with 96% (22 of 23) having two or fewer attempts. No complications were identified. In the BNI group, the mean number of attempts was 3.7 per patient, (range, one to 13) with 45% (13 of 29) having two or fewer attempts (P less than .005). Sixty-nine percent of the BNI group experienced epistaxis, 17% had vomiting, and 10% aspirated. We conclude that SAI is a safe and effective method of airway protection in the obtunded poisoned patient. Complications and difficulty in intubation were significantly less with SAI than with blind nasotracheal intubation.

Adult↗
PubMed1987

Effects of dichloroacetate administration during fatal hemorrhagic shock in immature swine.

During hemorrhagic shock, decreased perfusion and poor tissue oxygenation lead to increased lactate production. Previous animal studies have suggested that sodium dichloroacetate (DCA), an agent that decreases lactate production, can improve hemodynamics and survival when administered after severe hemorrhage. We used an unanesthetized porcine hemorrhagic shock model to assess the effect of DCA on survival time when administered during fatal hemorrhage. Immature female swine weighing 14 to 20 kg were splenectomized and instrumented with chronic indwelling aortic and right atrial catheters one week prior to hemorrhage. On the day of the experiment, the unanesthetized animals' aortic catheter was connected to a roller pump and blood was removed at a rate of 1.0 mL/kg/min until death occurred. Experimental animals (n = 8) received sodium dichloroacetate (25 mg/mL distilled water) 100 mg/kg IV bolus beginning 15 minutes after the start of hemorrhage followed by a 3 mg/kg/min constant IV infusion. Control animals (n = 8) received an equal volume of normal saline. Arterial pressure, heart rate, blood gases, serum lactate, and serum glucose were measured at baseline and every 15 minutes during hemorrhage. There were no significant differences in survival time (controls, 63 +/- 2.8 min; DCA-treated, 60 +/- 3.7 min), lactate levels, or blood pressures between the two groups. These results suggest that DCA does not decrease serum lactate or improve survival time when administered during ongoing severe hemorrhagic shock. Further study should be directed at the effects of DCA as an adjunctive treatment after hemorrhage has been controlled and tissue perfusion restored.

Acetates↗
PubMed1986

Vivax malaria.

Malaria occurs in the United States infrequently and is found exclusively among immigrants and travelers returning from areas where the disease is endemic. Cases of acute relapses of Plasmodium vivax infection can present to the emergency department. Patients are often immigrants from developing countries who were symptom-free in this country for weeks or months preceding their illness. The clinical presentation and current treatment of malaria are reviewed. Malarial infection may become apparent months after leaving endemic areas despite adherence to prophylactic regimens. The disease usually responds to appropriate drug therapy with rapid and often dramatic results, but it can be fatal if unrecognized.

Acute Disease↗
PubMed1986

Lack of efficacy of naloxone in a fixed-volume hemorrhage model.

Animal studies using a reservoir model of hemorrhagic shock have shown the narcotic antagonist naloxone to be of value in reversing the hemodynamic effects of severe hemorrhage. We conducted a study to evaluate the ability of naloxone to limit the deleterious effects of a fixed-volume hemorrhage. Fifteen mongrel dogs were bled 50% of their estimated blood volumes during one hour. This was followed by a one-hour stabilization period; reinfusion during a 30-minute period; and finally, an additional one-hour monitoring period. Eight dogs received 2 mg/kg IV naloxone 30 minutes prior to hemorrhage and 2 mg/kg/hr for the duration of the study. Seven control dogs received an equivalent volume of saline without naloxone. Pulmonary capillary wedge pressure, central venous pressure, cardiac output, heart rate, blood pressure, arterial and mixed venous blood gases, and serum lactate were measured at 19 intervals throughout the study period. Mean arterial pressure, cardiac index, and systemic vascular resistance were calculated for each sampling period. With the exception of serum lactates, which were higher in the naloxone group, there were no significant differences between the groups in the mean values calculated for each sampling interval (P less than .05, two-tailed independent t test). Furthermore, the changes in hemodynamic parameters observed during the hemorrhage, stabilization, reinfusion, and monitoring periods were not significantly different. We conclude that in this fixed-volume hemorrhage model, naloxone does not prevent or reverse hemodynamic deterioration.

Animals↗
PubMed1985

Transcutaneous oxygen tension measurements during graded hemorrhage and reinfusion.

Measurement of transcutaneous oxygen tension (PtCO2) has been suggested as a useful monitoring tool in the hypovolemic patient. Our study was undertaken to evaluate changes in PtCO2 that occur during graded hemorrhage and reinfusion, and to compare PtCO2 values to standard cardiorespiratory and biochemical parameters during hypovolemia. Seven mongrel dogs were bled 50% of their estimated blood volume (44 mL/kg) over one hour. This was followed by a one-hour monitoring period, a 30-minute reinfusion period, and an additional one-hour monitoring period. Pulmonary capillary wedge pressure (PCWP), central venous pressure (CVP), cardiac output (CO), mean arterial pressure (MAP), mixed venous oxygen tension (MvO2), arterial blood gases, and PtCO2 were measured serially throughout the study period. Cardiac index (CI), peripheral vascular resistance (PVR), O2 consumption, delivery, and percentage of extraction were calculated for each sampling period. A statistically significant fall in CI, MvO2 and PCWP occurred following the first 10% of blood loss; PtCO2 and MAP fell significantly after 20% hemorrhage; CVP fell after 30% hemorrhage. PtCO2 rose significantly after the first 10% of reinfusion, and it continued to rise during the entire reinfusion period, as did MvO2, CO, MAP, CVP, and PCWP. In contrast to the other measured variables, the elevations in PtCO2, and MvO2 were more pronounced early in the reinfusion period. During postreinfusion monitoring, PtCO2, MvO2, CO, and PCWP fell significantly despite maintenance of prehemorrhage MAP and CVP. Overall PtCO2 correlated well with MvO2 and the O2 extraction ratio, and to a lesser extent with CI, MAP, and O2 delivery.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗