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Biomedical subjects

M C Rogers

Publications and source records attributed to M C Rogers.

At least 73 records · Page 4Linked to original sources
PubMed1984

Comparison of cerebrovascular response to hypoxic and carbon monoxide hypoxia in newborn and adult sheep.

Cerebral blood flow (CBF) responses to two types of isocapnic hypoxia, hypoxic hypoxia (HH) and carbon monoxide hypoxia (COH), were examined in seven unanesthetized adult sheep by the radiolabeled microsphere technique. Comparisons were made with newborn lambs (5-12 days old) previously studied under similar conditions. The arterial O2 content (CaO2) was reduced in a graded manner to 50-60% of the control value. During HH, CBF increased to maintain cerebral O2 delivery (CaO2 X CBF) in both adults and newborns; however, cerebral O2 uptake (CMRO2) did not change. Although CMRO2 was higher in newborns, the responses of CBF/CMRO2 to HH did not differ significantly in newborns and adults. In newborns, regional CBF showed that brainstem areas were particularly responsive to HH. In both age groups, CBF increased to a greater extent with COH than with HH for similar reductions in CaO2. This resulted in an increase in cerebral O2 delivery with COH. The degree to which COH differed from HH correlated with the magnitude of the leftward shift of the oxyhemoglobin dissociation curve that accompanies COH. In adults, CMRO2 fell by 16% with COH but was maintained in newborns. We conclude that maintenance of cerebral O2 delivery during acute, isocapnic HH is a property of CBF regulation common to both newborn and adult sheep. During COH, the position of the oxyhemoglobin dissociation curve is an additional factor that sets the level of O2 delivery. The fetal conditions of low CaO2 and a left-shifted oxyhemoglobin dissociation curve may have provided the newborn with a microcirculation better suited for maintaining CMRO2 during COH.

Animals↗
PubMed1984

Comparison of the effects of positive end-expiratory pressure and jugular venous compression on canine cerebral venous pressure.

The confluent sinus pressure was measured in eight mongrel dogs in the head-up position to compare the effectiveness of positive end-expiratory pressure (PEEP) and jugular venous compression in increasing cerebral venous pressure. When the head was elevated 30 cm above the heart, confluent sinus pressure decreased from 9.6 +/- 1.8 (mean +/- SEM) to -5.3 +/- 0.5 mmHg. At constant arterial carbon dioxide tension (PaCO2 = 28 +/- 2 mmHg), PEEP (20 cmH2O) did not increase cerebral venous pressure. However, when the jugular veins were compressed with a neck tourniquet with pressures of 20-140 mmHg, cerebral venous pressure increased rapidly. When neck tourniquet pressure was maintained at 40 mmHg, confluent sinus pressure in all dogs was increased and sustained at 2.4 +/- 0.8 mmHg. Carotid artery pressure measured distal to the tourniquet was not altered. The efficacy of extrathoracic venous pressure elevation (neck tourniquet) is greater than intrathoracic (PEEP), and this may relate to the Starling resistor effects of neck veins and the presence of jugular venous valves. We conclude that prophylactic use of PEEP in the prevention of air embolism during the sitting position may not be as effective as jugular venous compression.

Animals↗
PubMed1984

Mechanisms by which epinephrine augments cerebral and myocardial perfusion during cardiopulmonary resuscitation in dogs.

The goals of this study were to quantify the effects of epinephrine on myocardial and cerebral blood flow during conventional cardiopulmonary resuscitation (CPR) and CPR with simultaneous chest compression-ventilation and to test the hypothesis that epinephrine would improve myocardial and cerebral blood flow by preventing collapse of intrathoracic arteries and by vasoconstricting other vascular beds, thereby increasing perfusion pressures. Cerebral and myocardial blood flow were measured by the radiolabeled microsphere technique, which we have previously validated during CPR. We studied the effect of epinephrine on established arterial collapse during CPR with simultaneous chest compression-ventilation with the abdomen bound or unbound. Epinephrine reversed arterial collapse, thereby eliminating the systolic gradient between aortic and carotid pressures and increasing cerebral perfusion pressure and cerebral blood flow while decreasing blood flow to other cephalic tissues. Epinephrine produced higher cerebral and myocardial perfusion pressures during CPR with simultaneous chest compression-ventilation when the abdomen was unbound rather than bound because abdominal binding increased intracranial and venous pressures. In other experiments we compared the effect of epinephrine on blood flow during 1 hr of either conventional CPR or with simultaneous chest compression-ventilation with the abdomen unbound. Epinephrine infusion during conventional CPR produced an average cerebral blood flow of 15 ml/min . 100 g (41 +/- 15% of control) and an average myocardial blood flow of 18 ml/min . 100 g (15 +/- 8% of control). In our previous studies, cerebral and myocardial blood flow were less than 3 +/- 1% of control during conventional CPR without epinephrine. Although flows during CPR with simultaneous chest compression-ventilation without epinephrine were initially higher than those during conventional CPR, arterial collapse developed after 20 min, limiting cerebral and myocardial blood flow. The use of epinephrine throughout 50 min of CPR with simultaneous chest compression-ventilation maintained cerebral blood flow at 22 +/- 2 ml/min . 100 g (73 +/- 25% control) and left ventricular blood flow at 38 +/- 9 ml/min . 100 g (28 +/- 8% control). The improved blood flows with epinephrine correlated with improved electroencephalographic activity and restoration of spontaneous circulation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

Augmentation of cerebral perfusion by simultaneous chest compression and lung inflation with abdominal binding after cardiac arrest in dogs.

Recent studies have demonstrated that for the same chest compression force during mechanical cardiopulmonary resuscitation (CPR), the carotid artery-to-jugular vein pressure gradient and carotid blood flow are increased when the phasic rise of intrathoracic pressure is enhanced by abdominal binding and simultaneous ventilation at high airway pressure with each chest compression (SCV). The objective of the present study was to assess whether cerebral blood flow is also enhanced, since it is known that fluctuations in intrathoracic pressure are transmitted to the intracranial space and affect intracranial pressure (ICP). In two series of pentobarbital-anesthetized dogs, one of two CPR techniques was initiated immediately after inducing ventricular fibrillation. Brain blood flow was measured by the radiolabeled microsphere technique immediately before cardiac arrest and at 1 and 3 minutes after commencing CPR. Evidence of adequate mixing of spheres and lack of sedimentation under these low-flow conditions was verified by correlation with brain venous outflow, comparison of the arterial concentration-time profile of spheres and a nonsedimentary marker (thallium-201 in solution), and use of multiple arterial sampling sites. During SCV CPR with abdominal binding, mean carotid artery pressure (60 +/- 3 mm Hg) was higher than that during conventional CPR (25 +/- 2 mm HG). Pulsations of ICP occurred that were in phase with chest compression and greater than jugular venous pressure. Mean ICP was higher during SCV (46 +/- 2 mm Hg) than conventional CPR (20 +/- 2 mm Hg). However, the net brain perfusion pressure gradient (carotid artery pressure - ICP) was greater with SCV (14 +/- 3 mm Hg) than with conventional CPR (5 +/- 0.4 mm Hg). Cerebral blood flow was significantly greater during SCV CPR (32 +/- 7% of prearrest cerebral flow) than during conventional CPR (3 +/- 2%). We conclude that SCV CPR combined with abdominal binding substantially improved brain perfusion by enhancing cerebral perfusion pressure in this experimental model.

Abdomen↗
PubMed1983

Gypsies and acute medical intervention.

Recently, a 7-month-old, terminally ill Gypsy infant was admitted to a pediatric intensive care unit. Treating this child and her extended family was a challenging experience during which numerous culture-related problems were encountered. The Gypsy approach to acute medical care consisted of the presence of a large extended family unit, the lack of decision making by the patient's parents, and several different Gypsy traditions. There were diverse, and often derogatory, reactions and prejudices from the hospital staff. After interviewing family members, this family's needs were easier to understand, and interaction with them in culturally relevant terms was possible. When dealing with Gypsy families, identification of the responsible elder male members of the family, establishment of firm lines of communication with essential family members and the parents, and education of the medical staff concerning Gypsies are recommended.

Acute Disease↗
PubMed1983

Long-term outcome of children with severe head trauma and prolonged coma.

Forty-six children with significant head trauma who remained in coma more than 24 hours were the subjects of this long-term outcome study. Twelve (38%) died. The average length of coma in the 34 survivors was 15.5 days. Follow-up ranged from 9 months to 4 years (mean 21 months). Twenty-nine percent of the survivors were normal at follow-up. An additional 53% had mild cognitive or behavioral problems, but 61% of these had evidence of similar problems prior to the injury. Nine percent of survivors had motor residua but normal intellect. Nine percent had severe intellectual and motor problems. Children less than 2 years of age had a worse outcome. Despite severe injury and prolonged coma after head trauma, most children do well. Intensive medical and surgical care increases the rate of survival and does not result in a large number of severely disabled survivors.

Adolescent↗
PubMed1982

Selective chemical hepatic sympathectomy in the dog.

Intraportal injection of 6-hydroxydopamine (6-OHDA) was used to produce selective hepatic sympathectomy in the dog. Previously reported techniques for 6-OHDA induced hepatic sympathectomy in rats and cats were modified considerably using alpha and beta adrenergic blocking agents to prevent the otherwise intense and fatal sympathomimetic response which has prevented adaptation of the intraportal 6-OHDA injection for dogs. After 6-OHDA injection, histofluorescent staining demonstrated loss of hepatic adrenergic nerves with preservation of normal adrenergic innervation in the heart and pancreas. Tyramine iv was used to further document functional integrity of peripheral sympathetic mechanisms. This technique provides a useful model for evaluation of sympathetic nervous system mediated changes in hepatic metabolic function associated with the neuroendocrine response to hemorrhage in the classic dog model.

Animals↗
PubMed1982

Overestimation of pediatric cardiac output by thermal indicator loss.

The accurate measurement of pediatric cardiac output by thermodilution requires that the quantity of cold indicator introduced into the central circulation be known. This study defines an important source of error in the correction factor for the amount of heat gained by small volumes of cold injectate during passage through pediatric catheter systems. This error may result in significant overestimation of cardiac output (as much as 59%) when blood at body temperature is withdrawn into the injection lumen of the pediatric catheter before the injection.

Age Factors↗
PubMed1980

Intracranial pressure monitoring in the management of the pediatric trauma patient.

Intracranial pressure (ICP) monitoring is an important adjunct in the management of the severely injured child with major head trauma. From a series of 18 patients with multiple trauma, smoke inhalation, and near-drowning, we report an illustrative case of head injury and pulmonary aspiration in which ICP monitoring was vital to appropriate therapy. The two most common techniques of ICP monitoring, the intraventricular catheter and the subarachnoid bolt, are described. Treatment of intracranial hypertension is discussed based on physiological principles. The continuous, objective recording of ICP assumes particular importance when therapy directed at other injured organ systems (ie, institution of positive end-expiratory pressure) could adversely affect the ICP. It is suggested that optimal care of children with multiple trauma and head injury include early ICP monitoring.

Bacterial Infections↗
PubMed1980

Fulminant hepatic failure and hepatic encephalopathy.

Fulminant hepatic failure implies either acute massive destruction of liver tissue or another process that causes rapid deterioration in function of a previously normal liver. The diagnosis in children needs to be differentiated from hepatic failure that occurs as a complication of underlying congenital, anatomical, and metabolic abnormalities.

Acute Disease↗
PubMed1980

Pediatric intensive care unit patients. Effects of play intervention on behavior.

The effects of a 20-min play intervention by a child life teacher on two observed behaviors were investigated in Pediatric Intensive Care Unit (PICU) patients at the Johns Hopkins Hospital Children's Center. Eleven subjects, ranging in age from 2--13 years, were observed using a Preintervention--Intervention--Postintervention design with a 3-min time sampling technique to measure the change occurring when structured play activities were introduced into the PICU environment. Significant positive changes were noted between Preintervention and Intervention in (1) affect and (2) interaction with materials. In the Postintervention period, these behaviors fell close to Preintervention levels, suggesting that the positive changes were not maintained in the absence of the Intervention condition. The results indicate that while play intervention in the PICU environment can have beneficial effects on patient's behavior, the effects of such intervention are short-lived. These data hold important implications for the staffing requirements needed to provide opportunities for the positive behavior changes to occur.

Adolescent↗
PubMed1980

Electrocardiographic abnormalities in infants and children with neurological injury.

Electrocardiographic (ECG) abnormalities were found in 15 of 20 consecutive children (75%) admitted to the Pediatric ICU (PICU) with central nervous system injury produced by trauma or neurosurgical procedures. The ECG abnormalities included prolonged qTc, U waves, and notched T waves as well as ventricular arrhythmias. The high frequency and potential seriousness of this problem in infants and children suggests that neurogenic ECG changes should be looked for in all infants and children with neurological insults.

Adolescent↗