Thrombosis as complication of MAST use.
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Aged↗
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Anterior tibial compartment syndrome with use of MAST.
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Anterior Compartment Syndrome↗
Effects of pneumatic antishock trousers on canine intracranial pressure.
The military antishock trouser (MAST) has become an accepted prehospital treatment modality for hypovolemic shock. Our interest in the effect of MAST on intracranial pressure (ICP) was aroused by the manufacturer's written warning that use of the device was contraindicated in patients with suspected head injury. This study was undertaken to determine the effect of MAST device inflation on intracranial pressure in dogs with normal and artificially elevated ICP in both normovolemic and hypovolemic states. The largest increase in hemodynamic parameters was seen in mean arterial pressure (MAP) in hypovolemic animals. Although the ICP did increase with MAST inflation, it never reached levels of clinical significance. Furthermore, the cerebral perfusion pressure (MAP--ICP) was calculated and shown to be improved in all groups when the MAST device was inflated. Data from this study support clinical use of the MAST garment in hypovolemic patients even in the presence of suspected head injury.
Animals↗
Blood volume displacement with inflation of antishock trousers.
Eleven healthy male volunteers were studied to determine the amount of blood displaced by the inflation of the antishock trousers (AST) at pressures of 40 and 100 mm Hg. Radioisotope scans were used to determine the blood volume distribution and the change in the volume of distribution with inflation of the AST. The volunteers were then phlebotomized approximately one liter of blood and the study was repeated. Less than 5% of the total blood volume was displaced with inflation of the AST. It is unlikely that the clinical improvement seen with inflation of the AST in hypovolemic shock is due to autotransfusion of blood alone.
Adolescent↗
MAST use in atrial arrhythmia questioned.
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Atrial Flutter↗
Efficacy of pneumatic trousers in refractory prehospital cardiopulmonary arrest.
Persons refractory to early application of advanced cardiac life support have a dismal prognosis. New modalities are needed to treat this almost universally lethal condition. We have evaluated pneumatic trousers in the treatment of refractory cardiopulmonary arrest. To date 136 patients have been entered into this controlled, prospective, randomized study. All patients were more than 20 years old and in cardiac arrest of apparent cardiac etiology. Patients were excluded if they had arrested secondary to trauma or overdose, or if an IV could not be started. In addition, patients had to be refractory to therapies included in our paramedic standing orders. If at the end of these standing orders the patient remained in arrest, he was entered into the study and pneumatic trousers were applied or not according to a randomized list. The attempted resuscitation was then continued with no other preset variables. The resuscitation and discharge rates for the control group were 21% and 4%, respectively. With pneumatic trousers, resuscitation increased to 33%, and discharge to 9%. The control group in ventricular fibrillation (VF) had a 27% resuscitation rate and a 5% discharge rate. The pneumatic trousers group with VF had a 35% resuscitation rate and a 12% discharge rate. In pulseless idioventricular rhythm (PIVR), the control group had a 0% resuscitation rate and a 0% discharge rate. In marked contrast, for PIVR the pneumatic trousers group had a 35% resuscitation rate and a 9% discharge rate. The control group in asystole (AS) had a 25% resuscitation rate and a 0% discharge rate. The pneumatic trousers group in AS had a 27% resuscitation rate and a 0% discharge rate. The improvement in resuscitation rate with pneumatic trousers was statistically significant only for the initial rhythm of PIVR (P less than .05). The pneumatic trousers improved resuscitation and discharge rates for refractory VF, but not to a statistically significant degree. These somewhat enhanced resuscitation and discharge rates with the pneumatic trousers make it an adjunct to be considered in refractory arrest.
Adult↗
Hemodynamic effects of pneumatic external counterpressure in canine hemorrhagic shock.
To assess the effects of external counterpressure in a hypovolemic canine model, mean right atrial pressure (RA), left ventricle end-diastolic pressure (LVEDP), mean aortic pressure (Ao), and cardiac output (CO) (indicator dilution technique or electromagnetic ascending aortic flow) were measured in eight closed-chest mongrel dogs following phlebotomy to an Ao of 50 to 60 mm Hg. Inferior vena cava (IVC) flow was measured electromagnetically with a cannulating probe in four animals. The antishock garment was inflated to pressures of 40, 60, 80, and 100 mm Hg. An extended shock "control" period preceded inflation to minimize the effect of reflex circulatory responses to acute blood loss. IVC flow (2 +/- 1 mL/min/kg) during and immediately following antishock garment inflation was not significantly different from control (3 +/- 1 mL/min/kg) regardless of inflation pressure. Ao, RA, and LVEDP measured 30 seconds and 15 minutes after garment inflation were increased, but CO was not significantly different from control values at each inflation pressure. Garment inflation significantly increased peripheral vascular resistance (PVR) at all inflation pressures, and there was a significant correlation (r = .53; P less than .001) between the change in Ao and PVR. These results indicate that the change in arterial pressure produced by external counterpressure is the result of an increase in PVR and not the result of an autotransfusion and subsequent increased left heart outflow in the canine shock model.
Animals↗
Clinical evaluation of the antishock trouser: prospective study of low-pressure inflation.
We designed a prospective study to address the question of the adequacy of low-pressure (20 to 30 mm Hg) inflation of pneumatic anti-shock trousers when in use on hypotensive patients in the prehospital and emergency department settings. For an eight-month period, all patients who were candidates for pneumatic trousers received a two-stage inflation process. Of 120 patients who received trousers, 91 survived more than 24 hours, and their response to low-pressure inflation was analyzed. The majority (70%) did not respond at low pressure. Those patients who did respond were characterized by a higher initial systolic pressure (P less than .05), indicating that their degree of shock was relatively mild. In responding patients, the response varied, affirming the importance of full clinical assessment. Gauges showing intrasuit pressure are not necessary to evaluate patient condition.
Emergencies↗
Prehospital use of dexamethasone in pulseless idioventricular rhythm.
We investigated the prehospital use of 100 mg dexamethasone for the treatment of cardiac arrest patients with pulseless idioventricular rhythms (PIVR). In the 86 patients studied in this prospective, randomized, double-blind investigation, four of the 46 patients receiving saline and two of the 37 patients receiving dexamethasone survived long enough to be admitted to the hospital intensive care unit. There were no long-term survivors. No benefit from the field use of 100 mg dexamethasone in PIVR could be identified in this study.
Arrhythmias, Cardiac↗
Successful treatment of paroxysmal supraventricular tachycardia with MAST.
We have noted that inflation of the military antishock trousers (MAST) successfully converted five of six patients with paroxysmal supraventricular tachycardia to normal sinus rhythm. In all patients the usual "vagal" maneuvers were tried first and were unsuccessful. MAST inflation may be a safe and useful addition to the traditional vagal maneuvers used to treat paroxysmal supraventricular tachycardia.
Adult↗
Thoracic stab wound with delayed pneumoperitoneum and pneumomediastinum.
A 21-year-old man with an innocent-appearing, self-inflicted stab wound to the left upper anterior chest developed pneumoperitoneum and pneumomediastinum seven hours after the injury. At laparotomy he had lacerations of the left hemidiaphragm and anterior wall of the stomach, which were surgically repaired. He recovered without complications. Although brief (four- to six-hour) outpatient observation of patients with seemingly superficial thoracic stab wounds recently has been recommended, this case suggests that longer observation periods for such injuries may be appropriate.
Adult↗
Effect of the pneumatic antishock garment on intramuscular pressure.
Recent case reports implicate pneumatic antishock garment (PASG) usage in subsequent development of compartment syndromes. The anterior tibial compartment pressures of eight healthy volunteers were selected for study at varying PASG inflation pressures. A wick catheter method provided continual intramuscular compartment pressure (IMP) monitoring throughout the period of study. A linear correlation between PASG pressure and IMP exists, with more than 90% of the externally applied pressure being transmitted to the muscle compartment. All subjects developed IMP greater than 50 mm Hg at PASG inflation of 60 mm Hg. Externally applied pressure appears to create a condition that may stimulate or lead to a compartment syndrome. Inflation pressure should be monitored closely during PASG application, because IMP can be assumed to be at least as high as inflation pressure. The lowest effective PASG pressure should be used.
Adult↗
Lower extremity ischemia associated with use of military antishock trousers.
A 58-year-old man was admitted to a community hospital following an overdose of nifedipine. Military antishock trousers (MAST) were applied to combat severe hypotension. Blood pressure was restored to 110/50 mm Hg three hours after admission, but the patient remained comatose. Subsequent to MAST garment removal, ischemia of both legs and scrotum was observed; at surgery, both iliofemoral systems were occluded from the aortic bifurcation to the feet. The patient never regained consciousness and died from recurrent ventricular tachycardia. The possible contributing role of the MAST garment in producing lower extremity ischemia is discussed.
Blood Pressure↗
Effect of antishock trouser inflation on plasma renin activity during hemorrhagic shock.
The effect of antishock trouser inflation on plasma renin activity during hypovolemic shock was studied in dogs. Following anesthesia, six dogs were bled to a systolic blood pressure of 60 mm Hg. Antishock trousers were inflated to 40 to 100 mm Hg for 20 minutes each. Plasma renin activity was measured before phlebotomy, after phlebotomy, and after each 20-minute period of antishock trouser inflation. Three dogs without antishock trousers served as controls. Experimental animals had a significant rise in blood pressure when the antishock trousers were inflated to 100 mm Hg. Plasma renin activity showed a marked increase following phlebotomy (experimental, 1.55 ng/mL/h to 13.63 ng/mL/h; control, 2.71 ng/mL/h to 19.7 ng/mL/h). Both groups had a continued small, statistically insignificant rise in plasma renin levels throughout the remainder of the experiment. Plasma renin level changes did not explain the observed rise in blood pressure following antishock trouser inflation. Plasma renin levels remained elevated in spite of improvement of blood pressure after application of antishock trousers.
Animals↗
Circulatory support during cardiac arrest using a pneumatic vest and abdominal binder with simultaneous high-pressure airway inflation.
Animal and clinical studies suggest that blood flow during closed-chest cardiopulmonary resuscitation (CPR) results from phasic intrathoracic pressure fluctuations produced by rhythmic sternal depressions rather than from cardiac compression. Using physiologic observations made in animals and human beings during circulatory collapse and vigorous coughing, a pneumatic thoracic vest garment and abdominal binder device has been designed to emulate "cough CPR." Hemodynamic findings and microsphere regional perfusion observed during cardiac arrest and airway/vest/binder inflation are comparable to those observed during simultaneous chest compression and pulmonary ventilation CPR (SCV-CPR). Resuscitation and survival using the device has been compared to survival rates using conventional closed-chest CPR. The vest/binder apparatus significantly improved the coronary perfusion gradient and survival. Further studies are in progress to determine the clinical utility of this promising resuscitation adjunct.
Abdomen↗
MAST usage in cardiopulmonary resuscitation.
The medical antishock trouser (MAST) has been advocated as potentially beneficial in the resuscitation of patients in cardiac arrest. Currently available data indicate that the MAST will increase the blood pressure generated by external cardiopulmonary resuscitation. In addition, there may be an increased survival of patients found in cardiac arrest with an initial cardiac rhythm of pulseless idioventricular rhythm when the MAST is used. The physiologic parameters affected by the MAST may be similar to those caused by vasopressor agents in animal studies and implicated in increased survival rates. The clinical implications of these data and their relation to future investigations are discussed.
Gravity Suits↗
Effect of a pneumatic antishock garment on drug delivery via distal venous access.
We examined the effect of an inflated pneumatic antishock garment (PASG) on simulated drug delivery through a distally placed venous catheter, during both normal flow and cardiopulmonary resuscitation (CPR). A PASG device was applied to anesthetized mongrel dogs and was inflated to 60 mm Hg. A small bolus of radionuclide was injected through an intravenous catheter placed distal to the PASG. Emission counts were made over both ventricles during conditions of normal flow and then during CPR following cardiac arrest. Mean times from injection to peak counts were determined. A control group of animals with central venous catheters but no PASG was studied similarly. There were no clinically appreciable differences between groups during normal flow. During CPR the PASG animals showed a mean delay of 90 seconds to the left ventricle peak. This difference was not statistically significant. We conclude that, in this canine model, acceptable delivery of drugs can be obtained by venous infusion into a limb with a PASG inflated.
Animals↗
Science and shock: a clinical perspective.
In spite of all the scientific and technical advances in recent years, shock that is not rapidly correctable with fluid can have a morbidity rate exceeding 80%. Consequently awareness of such precipitating factors as sepsis and early diagnosis and treatment are essential. Treatment should be rapid and should follow a previously outlined protocol. Such protocols should include correction of the precipitating problem and aggressive resuscitation to assure adequate ventilation and oxygenation of the blood and optimal oxygen delivery to the tissues. Fluid and blood should be given as needed until filling pressures begin to rise rapidly with further fluid infusion. With hemorrhagic shock in previously healthy individuals, a hemoglobin level of 10.0 g/dL is usually adequate. In older, septic, or cardiogenic shock patients, a hemoglobin level of 12.5 to 14.0 may be preferable. If an optimal preload does not increase cardiac output to normal or higher levels, inotropic agents should be used. If shock still persists, one must be sure that the arterial pH is not excessively high or low. Glucocorticoids may then be given in low dose (200 mg hydrocortisone) in case some degree of adrenal insufficiency is present. They can also be given in high doses (equivalent to 150 mg/kg hydrocortisone) early in septic shock primarily to prevent excess complement activation and to preserve membrane integrity. Vasopressors may occasionally be required if there is excessive vasodilation, especially if there is persistent hypotension in the presence of high-grade coronary or cerebral artery stenosis. Vasodilators may be used to try to correct myocardial ischemia (nitroglycerin), excessive preload (nitroglycerin), or excessive afterload (nitroprusside or hydralazine). Combinations of vasodilators and inotropic agents may be required in some patients with high systemic vascular resistance and persistently low cardiac outputs. Mechanical assist with IABP can be of great value in persistent cardiogenic shock. Diuretics may occasionally help prevent renal failure in patients who are persistently oliguric after blood flow and pressure are restored. Heparin is occasionally of value if DIC develops with no concomitant fibrinolysis. Antibiotics are important in septic shock and may also be important if persistent shock has reduced gastrointestinal mucosal integrity so that bacteria and bacterial products can enter the portal system.(ABSTRACT TRUNCATED AT 400 WORDS)
Acidosis, Respiratory↗