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Biomedical subjects

J M Dean

Publications and source records attributed to J M Dean.

At least 73 records · Page 4Linked to original sources
PubMed1989

Nonlinear dopamine pharmacokinetics in pediatric patients.

Dopamine steady-state concentrations were determined in 15 pediatric patients from 3 days to eight years of age receiving continuous infusions of dopamine. The first-order kinetic model does not accurately describe the kinetics of dopamine in these patients based on the finding that clearance varied as a function of concentration. A saturable protein binding model is described and provides a more accurate description of the behavior of the data. Using multivariate analysis, changes in dopamine kinetics were found as a function of weight. Furthermore, the co-administration of dobutamine altered the kinetics of dopamine. These data support the use of free dopamine concentrations rather than total concentration for studies of dopamine pharmacokinetics. Evaluation of total clearance of dopamine is of limited value, and changes in protein binding and intrinsic clearance must be considered in future studies of this drug.

Child, Preschool↗
PubMed1987

Age-related changes in chest geometry during cardiopulmonary resuscitation.

We studied alterations of chest geometry during conventional cardiopulmonary resuscitation in anesthetized immature swine. Pulsatile force was applied to the sternum in increments to determine the effects of increasing compression on chest geometry and intrathoracic vascular pressures. In 2-wk- and 1-mo-old piglets, permanent changes in chest shape developed due to incomplete recoil of the chest along the anteroposterior axis, and large intrathoracic vascular pressures were generated. In 3-mo-old animals, permanent chest deformity did not develop, and large intrathoracic vascular pressures were not produced. We propose a theoretical model of the chest as an elliptic cylinder. Pulsatile displacement along the minor axis of an ellipse produces a greater decrease in cross-sectional area than displacement of a circular cross section. As thoracic cross section became less circular due to deformity, greater changes in thoracic volume, and hence pressure, were produced. With extreme deformity at high force, pulsatile displacement became limited, diminishing pressure generation. We conclude that changes in chest geometry are important in producing intrathoracic intravascular pressure during conventional cardiopulmonary resuscitation in piglets.

Adolescent↗
PubMed1986

Lack of validity of diagnosis-related group payment systems in an intensive care population.

Case mix based on diagnosis-related groups (DRGs) was studied over 3 years for duration of stay and mean charges for a pediatric intensive care unit (PICU) and a general ward (WARD) population. Case mix variation for 2403 PICU and 14,552 WARD patients was analyzed, and a subset of 856 PICU and 2222 WARD patients examined for variations in duration of stay and mean charges in nine DRGs. Whereas case mix by DRG was consistent over time for both groups, the PICU case mix differed consistently from WARD case mix (P less than 0.001). After adjustment for inflation and for differences in case mix, average stay for the PICU was 10.7 days, versus 6.1 for the WARD (P less than 0.025), with a mean charge of $7172 per PICU and $2946 per WARD patient (P less than 0.01). Furthermore, the case mix-adjusted differences in duration of stay and mean charge between the PICU and WARD populations increased over time. Pediatricians will need to address DRG-based reimbursement systems that place intensive care units, and their institutions, at a significant financial disadvantage.

Adolescent↗
PubMed1986

Effect of epinephrine on cerebral and myocardial perfusion in an infant animal preparation of cardiopulmonary resuscitation.

We assessed the efficacy of conventional cardiopulmonary resuscitation (CPR) in 2-week-old piglets. We determined intrathoracic vascular pressures, cerebral (CBF) and myocardial blood flows (MBF), and cerebral oxygen uptake during conventional CPR in this infant animal preparation and contrasted these results with those of previous work on adult animals. We further examined the effects of the infusion of epinephrine on these pressures and flows and on cerebral oxygen uptake, which has not been previously evaluated in adult preparations. Conventional CPR was performed on pentobarbital-anesthetized piglets with a 20% sternal displacement with the use of a pneumatic piston compressor. Chest recoil was incomplete, leading to an 18% to 27% reduction in anteroposterior diameter during the relaxation phase. Aortic and right atrial pressures in excess of 80 mm Hg were generated. These pressures are greater than those generally obtained in adult animals with similar percent pulsatile displacements. CBF and MBF were also initially greater than those reported in adult animals undergoing conventional CPR. However, when CPR was prolonged beyond 20 min, aortic pressure fell and CBF and MBF declined to the near-zero levels seen in adult preparations. At 5 min of CPR, CBF and MBF were 24 +/- 7 and 27 +/- 7 ml . min-1 x 100 g-1 (50% and 17% of the values during cardiac arrest), respectively. With the continuous infusion of epinephrine (4 micrograms/kg/min) in another group of animals, MBF was significantly greater at 20 min of CPR and CBF and cerebral O2 uptake were greater at 35 min of CPR as a result of higher perfusion pressures.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Current concepts in brain resuscitation.

In spite of the tremendous amount of effort and money put forth to reduce morbidity and mortality associated with global cerebral ischemia, the outlook for patients suffering an ischemic insult remains dismal. The lack of a sufficient substrate supply during the period of ischemia as well as the production of toxic metabolites in response to ischemia have been incriminated as key factors causing brain damage. As discussed in this article, modes of therapy have included efforts to minimize the duration of ischemia (eg, effective cardiopulmonary resuscitation, hemodilution, heparinization, calcium antagonists) and decrease the production of toxic metabolites (eg, barbiturates, calcium antagonists). Although the barbiturates have also been proposed to decrease the metabolic needs during ischemia, they have no therapeutic value for global cerebral ischemia. The initial evaluation of the calcium antagonists has been more promising.

Animals↗
PubMed1985

Pulse oximetry in critically ill children.

To confirm the clinical applicability of a commercial pulse oximeter, we compared arterial hemoglobin saturation values determined by in-vitro oximetry and pulse oximetry in 15 critically ill children. One hundred ninety-two paired hemoglobin saturations were determined by both noninvasive pulse oximetry and direct measurement of arterial blood samples. The correlation between these two methods of measurement was statistically significant (r = 0.895; p less than 0.001). The mean percentage difference between the two measurements was 1.8%. Pulse oximetry was found to be safe and less cumbersome than other methods of monitoring arterial oxygen content. Overall, pulse oximetry was precise and provided a clinically satisfactory noninvasive method for continuously monitoring arterial hemoglobin saturation in critically ill children.

Child↗
PubMed1985

Beneficial effect of epinephrine infusion on cerebral and myocardial blood flows during CPR.

It is hypothesized that epinephrine improves the ability to resuscitate the heart through a mechanism thought to be related to the increase in aortic pressure. Our results with epinephrine infusion during CPR are consistent with this hypothesis. Epinephrine selectively increased vascular resistance in noncerebral, noncoronary vascular beds, as indicated by a decrease in microsphere-determined blood flow in these areas. This increased vascular resistance raised aortic pressure during the chest compression phase and the relaxation phase of CPR. Because intracranial and right atrial pressures were only slightly higher with epinephrine, cerebral and myocardial perfusion pressures and blood flows were significantly improved. This beneficial effect (compared to no administration of a vasopressor) was more pronounced as CPR progressed beyond ten minutes. Enhanced cerebral and myocardial perfusion occurred with epinephrine when either the conventional or simultaneous compression and ventilation (SCV) mode of CPR was employed in dogs. Similar selective perfusion was sustained for 50 minutes of SCV-CPR with epinephrine, even when the onset of CPR was delayed five minutes. Regional brain blood flow differed in the delayed-CPR group in that cerebellum, brain stem, and thalamic regions initially had higher blood flows. In an infant animal model of CPR using conventional CPR in piglets, epinephrine also was found to increase cerebral and myocardial blood flows. These results show that administration of epinephrine benefits different age groups of different species with different modes of CPR; that benefits occur even with delayed onset of CPR which is associated with additional anoxia and acidosis; and that epinephrine administration is particularly effective in sustaining cerebral and coronary perfusion during prolonged CPR.

Aging↗
PubMed1985

Arterial blood gas derived variables as estimates of intrapulmonary shunt in critically ill children.

Oxygen transport data, prospectively collected from 52 critically ill children, were analyzed to determine whether any derived variable accurately estimated intrapulmonary shunt (Qsp/Qt). Arterial hemoglobin saturation was more closely correlated with Qsp/Qt than was PaO2, alveolar-arterial oxygen gradient, arterial mixed venous oxygen difference (C[a-v]O2), arterial/alveolar oxygen ratio, and the ratio of PaO2 to inspired oxygen (FIO2) (r = 0.8, p less than .0001). When C(a-v)O2 was normal, hemoglobin saturation became a very accurate (r = 0.96) assessment of Qsp/Qt. We conclude that various arterial blood gas derived variables do not accurately reflect Qsp/Qt in critically ill children. In these patients, a pulmonary artery catheter is needed to accurately assess intrapulmonary shunt.

Child↗
PubMed1985

Interaction of CO2 and ammonia on cerebral blood flow and O2 consumption in dogs.

Studies of acutely induced hyperammonemia and chronic hyperammonemia associated with liver dysfunction suggest that cerebral blood flow (CBF) and O2 consumption (CMRO2) become uncoupled and that CMRo2 may depend on arterial CO2 tension (PaCO2). We examined CBF (radiolabeled microspheres) and CMRO2 during hypercapnia (PaCO2 congruent to 74 Torr) and hypocapnia (PaCO2 congruent to 21 Torr) both before and during intravenous ammonium acetate infusion in pentobarbital-anesthetized dogs. Continuous infusion over 120 min produced stable increases of arterial ammonia levels (1,400 mumol/l) by 30 min, whereas CBF, CMRO2, and O2 extraction (measured at sagittal sinus) remained unchanged when PaCO2 was held constant (congruent to 35 Torr). Acute hyperammonemia attenuated the increase in CBF during hypercapnia by 44% and abolished the decrease in CBF during hypercapnia. Regional blood flow to pons and midbrain increased under normocapnic conditions, and midbrain blood flow increased further during hypocapnia. Sodium acetate infusion did not affect CBF responses to CO2. Thus we failed to observe an uncoupling of global CBF and CMRO2 during normocapnic hyperammonemia, or an interaction of CO2 and ammonia on CMRO2, although the increased pons and midbrain blood flow may reflect regional effects of ammonia on reticular activating system metabolism. On the basis of the literature, we suggest that the attenuated hypercapnic CBF response may arise from impaired glial regulation of extracellular potassium and bicarbonate concentrations and that lactic acid production, enhanced by combined alkalosis and hyperammonemia, may contribute to the abolition of hypocapnic vasoconstriction.

Acetates↗
PubMed1985

Cerebral vascular diseases.

Strokes remain an important cause of mortality and morbidity despite recent advances in neurologic intensive care. Although support of ventilation and circulation improves the outcome for stroke patients, the efficacy of cerebral resuscitative measures such as hyperventilation, osmotherapy, fluid restriction, steroids, intracranial pressure control, and barbiturates remains unproven. Current specific therapies (anticoagulation, surgery) are useful in carefully selected patients. New therapies now being researched include fluorocarbons, narcotic antagonists, and calcium blockers.

Cerebral Hemorrhage↗
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↗
PubMed1981

Intracranial pressure monitoring in severe pediatric near-drowning.

Between April 1979 and April 1981, 20 near-drowned children admitted to Childrens Hospital of Los Angeles with a Glasgow coma score of 3 underwent intracranial pressure (ICP) monitoring and brain resuscitative therapy. By the 3rd hospital day, 14 patients had developed ICP elevation above 20 torr, and 11 of these had sustained intracranial hypertension above 30 torr. Ten of these children died, and 4 remain in a persistent vegetative state. Of 6 patients whose ICP never exceeded 20 torr, 3 recovered completely, 1 died, and 2 remain without any cognitive function. The salvage rate for patients with normal ICP after near-drowning accidents is significantly better than that for patients in whom the ICP is elevated (P = 0.017). Intracranial hypertension is associated with a uniformly bad outcome and is frequent in patients who die or suffer permanent, severe central nervous system damage after near-drowning.

Child↗
PubMed1981

Prognostic indicators in pediatric near-drowning: the Glasgow coma scale.

The records of 101 drowning or near-drowning victims admitted to Children's Hospital of Los Angeles (CHLA) between January 1975 and June 1978 were reviewed. The admission Glasgow coma score could be assigned retrospectively to 94 patients. A low score (less than 5) predicted a high risk group of patients with 80% mortality or permanent neurological sequelae. A high score (greater than or equal to 6) defined a low risk group of patients with no deaths or severe neurological sequelae. The Glasgow coma scale may be a useful tool for predicting the outcome of near-drowning victims in the pediatric age group.

Child↗