Biomedical subjects

H C Blake

Publications and source records attributed to H C Blake.

3 recordsLinked to original sources

PubMed1999

Adrenal dysfunction in hemodynamically unstable patients in the emergency department.

OBJECTIVE: Adrenal failure, a treatable condition, can have catastrophic consequences if unrecognized in critically ill ED patients. The authors' objective was to prospectively study adrenal function in a case series of hemodynamically unstable (high-risk) patients from a large, urban ED over a 12-month period. METHODS: In a prospective manner, critically ill adult patients presenting to the ED were enrolled when presenting with a mean arterial blood pressure < or =60 mm Hg requiring vasopressor therapy for more than one hour after receiving fluid resuscitation (central venous pressure of 12-15 mm Hg or a minimum of 40 mL/kg of crystalloid). Patients were excluded if presenting with hemorrhage, trauma, or AIDS, or if steroids were used within the previous six months. An adrenocorticotropic hormone (ACTH) stimulation test was performed and serum cortisol was measured. Treatment for adrenal insufficiency was not instituted. RESULTS: A total of 57 consecutive patients were studied. Of these, eight (14%) had baseline serum cortisol concentrations of <20 microg/dL (<552 nmol/L), which was considered adrenal insufficiency (AI). Three additional patients (5%) had subnormal 60-minute post-ACTH-stimulation cortisol responses (<30 microg/dL) and a delta cortisol < or =9 microg/dL, which is the difference between the baseline and 60-minute levels. This is functional hypoadrenalism (FH). There were no laboratory abnormalities that distinguished patients with AI or FH from those with preserved adrenal function (PAF). Rates of survival to discharge did not differ between the AI group (7 of 8) and PAF patients (21 of 46; p = 0.052). CONCLUSIONS: Adrenal dysfunction is common in high-risk ED patients. Overall, it has a frequency of 19% among a homogeneous population of hemodynamically unstable vasopressor-dependent patients. The effect of physiologic glucocorticoid replacement in this setting remains to be determined.

Adrenal Insufficiency↗

PubMed1994

Biphasic extrathoracic pressure CPR. A human pilot study.

HYPOTHESIS: Alternating intrathoracic pressure by means of a chest cuirass can cause perfusion and ventilation equal to or better than standard cardiopulmonary resuscitation (CPR) for humans in cardiac arrest. DESIGN: Nonrandomized, nonblinded, crossover pilot study. SETTING: Large urban emergency department. SUBJECTS: Five adult normothermic, nontraumatic, out-of-hospital cardiac arrest patients unresponsive to standard advanced cardiac life support. METHOD: Right atrial and aortic catheters were inserted for pressure measurement and blood gas analysis while the patient was receiving standard CPR by a pneumatic compression device (Thumper). The Thumper was then replaced by a chest cuirass (Hayek Oscillator). Pressure and blood gas measurements were then repeated. RESULTS: The coronary perfusion pressure increased from -1.2 +/- 8.6 mm Hg to 6.2 +/- 6.9 mm Hg for a mean change of 7.4 +/- 3.1 mm Hg (p = 0.006). The compression phase gradient increased 10.0 +/- 21.9 mm Hg (p = 0.364). The venous to arterial PCO2 gradient decreased 44.5 +/- 32.3 mm Hg (p = 0.070). The oxygen extraction ratio increased 1.6 +/- 9.4 percent (p = 0.761). The mean arterial PO2 and PCO2 changed from 252 to 240 mm Hg (p = 0.836) and from 53 to 66 (p = 0.172) mm Hg, respectively. CONCLUSION: The Hayek Oscillator chest cuirass produced a significant improvement in the coronary perfusion pressure. There was a trend for improved systemic perfusion as indicated by an improved compression phase gradient and venous to arterial PCO2 gradient, although this was not supported by the lack of improvement in the oxygen extraction ratio. The cuirass also adequately oxygenates and ventilates unassisted by positive pressure ventilation.

Cardiopulmonary Resuscitation↗

PubMed1994

The effect of the total cumulative epinephrine dose administered during human CPR on hemodynamic, oxygen transport, and utilization variables in the postresuscitation period.

BACKGROUND: Studies evaluating the dose of epinephrine required to optimize return of spontaneous circulation and survival after CPR have shown that doses greater than recommended by advanced cardiac life support (ACLS) improve coronary perfusion pressure and short-term resuscitation rates. Since survival has not improved, it is possible that higher doses of epinephrine may be physiologically detrimental in the postresuscitation period. OBJECTIVE: The object of this study is to measure the effect of the total cumulative dose of epinephrine given during ACLS on the hemodynamic, oxygen transport, and utilization variables in the postresuscitation period. DESIGN: A prospective nonrandomized control trial of inception cohorts. SETTING: A large urban emergency department and intensive care unit. PATIENTS: Forty-nine successfully resuscitated witnessed, normothermic, nontraumatic, out-of-hospital patients, who had suffered cardiac arrests. INTERVENTIONS: All patients were treated according to ACLS guidelines; however, the epinephrine dose (0.01 to 0.2 mg/kg or 1 to 14 mg) was selected at the clinician's discretion and given through central venous access every 3 to 5 min. Hemodynamic, oxygen transport, and utilization variables were measured on a return of spontaneous circulation, and at least every 30 min thereafter under a standardized postresuscitation protocol. MAIN OUTCOME MEASURES: Hemodynamic, oxygen transport/utilization variables, and mortality in patients resuscitated from cardiac arrest. The total cumulative dose of epinephrine given during ACLS until a return of spontaneous circulation was recorded. RESULTS: A total cumulative epinephrine dose of 15 mg was found to best predict 24-h mortality. Of the 49 patients, 20 received less than 15 mg (group 1) and 29 received greater than 15 mg (group 2). Age, premorbid health status, sex, presenting rhythm, and duration of cardiac arrest were similar in both groups. The 24-h survival was 17 of 20 (85%) and 12 of 29 (41%) in group 1 and 2, respectively (p < 0.002). Over the first 6 h of the postresuscitation period, both groups had similar mean arterial pressure (MAP), mixed venous oxygen saturation, and systemic oxygen extraction ratio (all p > 0.1). Group 2, however, had a significantly lower cardiac index (CI), systemic oxygen consumption (VO2), and systemic oxygen delivery (DO2) (all p < 0.01). Systemic vascular resistance index (SVRI), initial and 6-h lactic acid levels were significantly higher in group 2 (all p < 0.03). CONCLUSIONS: The administration of all doses of epinephrine during the resuscitation of out-of-hospital cardiac arrest is associated with impairment of DO2 and VO2 in the postresuscitation period. Both duration and severity of these impairments correlate with the total cumulative epinephrine dose given during the resuscitation. Thus, inadvertent catecholamine toxicity represents a further complicating factor in the production of postresuscitation disease. Diagnostic and therapeutic interventions addressed toward mitigating these potentially reversible adverse effects may impact morbidity and mortality in out-of-hospital cardiac arrests.

Adult↗