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Biomedical subjects

R M Nowak

Publications and source records attributed to R M Nowak.

At least 37 records · Page 2Linked to original sources
PubMed1991

The effect of standard- and high-dose epinephrine on coronary perfusion pressure during prolonged cardiopulmonary resuscitation.

We studied the effect of standard and high doses of epinephrine on coronary perfusion pressure during cardiopulmonary resuscitation in 32 patients whose cardiac arrest was refractory to advanced cardiac life support. Simultaneous aortic and right atrial pressures were measured and plasma epinephrine levels were sampled. Patients remaining in cardiac arrest after multiple 1-mg doses of epinephrine received a high dose of 0.2 mg/kg. The increase in the coronary perfusion pressures was 3.7 +/- 5.0 mm Hg following a standard dose, not a statistically significant change. The increase after a high dose was 11.3 +/- 10.0 mm Hg; this was both statistically different than before administration and larger than after a standard dose. High-dose epinephrine was more likely to raise the coronary perfusion pressure above the previously demonstrated critical value of 15 mm Hg. The highest arterial plasma epinephrine level after a standard dose was 152 +/- 162 ng/mL, and after a high dose, 393 +/- 289 ng/mL. Because coronary perfusion pressure is a good predictor of outcome in cardiac arrest, the increase after high-dose epinephrine may improve rates of return of spontaneous circulation.

Aorta↗
PubMed1991

Effects of arterial and venous volume infusion on coronary perfusion pressures during canine CPR.

Intraarterial (IA) volume infusion has been reported to be more effective than intravenous (IV) infusion in treating cardiac arrest due to exsanguination. A rapid IA infusion was felt to raise intraaortic pressure and improve coronary perfusion pressure (CPP). The purpose of this study was to determine if IA or IV volume infusion could augment the effect of epinephrine on CPP during CPR in the canine model. Nineteen mongrel dogs with a mean weight of 26.3 +/- 4.2 kg were anesthetized and mechanically ventilated. Thoracic aortic (Ao), right atrial (RA) and pulmonary artery catheters were placed for hemodynamic monitoring. Additional Ao and central venous catheters were placed for volume infusion. Ventricular fibrillation was induced and Thumper CPR was begun after 5 min (t = 5). At t = 10, all dogs received 45 micrograms/kg IV epinephrine. Six animals received epinephrine alone (EPI). Five dogs received EPI plus a 500 cc bolus of normal saline over 3 min intravenously (EPI/IV). Another group (n = 8) received EPI plus the same fluid bolus through the aortic catheter (EPI/IA). Resuscitation was attempted at t = 18 using a standard protocol. There was a significant increase in CPP over baseline in all groups. The changes in CPP from baseline induced by EPI, EPI/IV and EPI/IA were 20.6 +/- 3.7, 22.8 +/- 4.2 and 22.2 +/- 2.4 mmHg, respectively. Volume loading did not augment the effect of therapeutic EPI dosing. By increasing both preload and afterload, volume administration may in fact be detrimental during CPR.

Animals↗
PubMed1991

Cerebral lactate uptake during cardiopulmonary resuscitation in humans.

Animal studies have shown cerebral lactate uptake under conditions of anoxia and ischemia. Cerebral lactate uptake in humans during cardiopulmonary resuscitation (CPR) has not been previously reported in the literature. Forty-five patients receiving CPR underwent simultaneous sampling through jugular venous bulb, right atrial, and central aortic catheterization. The mean net cerebral lactate uptake (central aortic minus jugular venous bulb) was 0.76 +/- 1.86 and 0.80 +/- 2.03 mM on initial measurement and 10 min later, respectively. Both measurements were statistically significant (p = 0.01) compared to normal controls who have net cerebral output of lactate of -0.18 +/- 0.1 mM. Seventy-one percent of all patients had a cerebral uptake on initial sampling and this gradient persisted upon sampling 10 min later in 68% of the remaining 40 patients who did not have a return of spontaneous circulation. Among multiple variables measured, patients who exhibited a cerebral lactate uptake were 13.2 years younger (p = 0.004), received an additional 7.6 min of CPR (p = 0.05), and had a mean arterial lactate concentration of 4.8 mM higher (p = 0.005) than the nonuptake group. The pathophysiologic explanation of cerebral lactate uptake during CPR is multifactorial and includes utilization and/or diffusion.

Aged↗
PubMed1991

Aortic-carotid artery pressure differences and cephalic perfusion pressure during cardiopulmonary resuscitation in humans.

OBJECTIVE: Animal studies have shown an aortic-carotid artery pressure difference during cardiopulmonary resuscitation (CPR), which compromises cerebral perfusion. This pressure difference is most marked with prolonged CPR and can be abolished with administration of high doses of epinephrine. To better understand the mechanism of cerebral blood flow during CPR in humans, we determined the aortic-carotid artery pressure difference, the cephalic perfusion pressure (the carotid artery-jugular vein pressure difference), and thoracic inlet venous "valving" (the central venous-jugular vein pressure difference), while administering standard doses of epinephrine. DESIGN: Prospective study with randomization as to which side the carotid artery was catheterized. SETTING: The resuscitation room of a large urban hospital's emergency department. PATIENTS: Fifteen adults in normothermic, nontraumatic prehospital cardiac arrest treated according to Advanced Cardiac Life Support guidelines, including administration of 1 mg epinephrine iv every 5 mins. INTERVENTIONS: The descending aorta, cervical common carotid artery, internal jugular vein, and central venous system were catheterized. Pressures were recorded during standard CPR for 5 mins after administration of 1 mg epinephrine iv. MEASUREMENTS AND MAIN RESULTS: Most patients received CPR for greater than 20 mins before the first epinephrine dose and for greater than 45 mins before pressure recording as described above. There was no significant difference between aortic and carotid artery compression and relaxation phase pressures. The mean +/- SD compression central venous-jugular vein pressure difference was 22.1 +/- 15.0 mm Hg, and the mean cephalic perfusion pressure was 20.8 +/- 19.5 mm Hg. CONCLUSIONS: There is no clinically important aortic-carotid artery pressure difference during human CPR using the standard dose of epinephrine, even with prolonged CPR. Despite carotid artery patency and thoracic inlet venous valving, the cephalic perfusion pressure is low during CPR in humans.

Aged↗
PubMed1991

Plasma chromogranin A as a marker of sympathochromaffin activity in humans.

The extent to which the sympathochromaffin system compared with other endocrine/neuroendocrine tissues contributes to the plasma chromogranin A pool has not been defined. To test the hypothesis that the sympathochromaffin system is the major source of circulating chromogranin A only when that system is activated markedly, we measured chromogranin A concentrations in 200 human plasma samples known to have a broad range of norepinephrine and epinephrine concentrations, reflecting therefore a broad range of sympathochromaffin activity at the time of sampling. Plasma chromogranin A and norepinephrine concentrations were highly correlated when the sympathochromaffin system was activated markedly (cardiac arrest samples, n = 13, r = 0.8392, P less than 0.0005) and when there was release of large amounts of norepinephrine from tumors (pheochromocytoma samples, n = 17, r = 0.8132, P less than 0.001). However, when the sympathochromaffin system was activated less markedly, resulting in plasma catecholamine concentrations that spanned the physiological and lower pathophysiological range (nonpheochromocytoma noncardiac arrest samples, n = 170), correlations between plasma chromogranin A and norepinephrine (r = 0.2877, P less than 0.0001) and epinephrine (r = 0.3814, P less than 0.0001) levels were relatively weak, although still statistically significant. Thus, at basal through moderate stress levels, norepinephrine and epinephrine concentrations accounted for only approximately 10-15% of the variance in plasma chromogranin A levels. We conclude that, although plasma chromogranin A concentrations are a valid marker of sympathochromaffin activity in humans, they are not a sensitive marker under physiological conditions.

Adrenal Gland Neoplasms↗
PubMed1991

Nuclear magnetic resonance spectroscopy study of human brain after cardiac resuscitation.

We used 31P nuclear magnetic resonance spectroscopy to study the cerebral metabolic function of eight patients with severe postischemic anoxic encephalopathy secondary to cardiac arrest. Spectroscopy was performed at 18 +/- 13 and 64 +/- 20 hours after resuscitation. Glasgow Coma Scale scores at the time of initial and repeat spectroscopy were 3.6 +/- 1.2 and 3.5 +/- 1.2, respectively. In those patients whose spectra were of adequate quality to monitor pH, all demonstrated tissue alkalosis in at least one brain region. The mean brain pH at initial spectroscopy was 7.14 +/- 0.09 and was significantly alkalotic when compared with age- and sex-matched normal controls (pH = 6.98 +/- 0.04, p less than 0.0001). Five of the eight patients showed at least one region of persistent alkalosis at repeat spectroscopy, whereas one patient demonstrated severe acidosis with a pH of 6.42. Spectra demonstrated marked metabolic heterogeneity, ranging from normal in appearance to complete obliteration of all high-energy phosphates with only inorganic phosphate remaining.

Aged↗
PubMed1991

Prehospital care of acute myocardial infarction: a review.

Each year more than 1 million people in the United States suffer from acute myocardial infarction (MI) with most of the deaths occurring within hours of symptom onset. Over the last 25 years, different prehospital systems have evolved throughout the world which allow early cardiac monitoring and treatment of acute MI patients. Thrombolytic therapy in acute MI has been shown to decrease mortality and preserve left ventricular function when administered early after onset of symptoms. The potential role of Emergency Medical Services or Mobile Coronary Care Units in achieving early thrombolysis is under investigation. Several studies of prehospital interventions to achieve early thrombolysis are reviewed. The use of thrombolytics by prehospital personnel has been found to be feasible, safe, and effective in reducing time delays. However, whether this translates into clinical benefit remains to be seen.

Emergency Medical Services↗
PubMed1990

Coronary perfusion pressure and the return of spontaneous circulation in human cardiopulmonary resuscitation.

Coronary perfusion pressure (CPP), the aortic-to-right atrial pressure gradient during the relaxation phase of cardiopulmonary resuscitation, was measured in 100 patients with cardiac arrest. Coronary perfusion pressure and other variables were compared in patients with and without return of spontaneous circulation (ROSC). Twenty-four patients had ROSC. Initial CPP (mean +/- SD) was 1.6 +/- 8.5 mm Hg in patients without ROSC and 13.4 +/- 8.5 mm Hg in those with ROSC. The maximal CPP measured was 8.4 +/- 10.0 mm Hg in those without ROSC and 25.6 +/- 7.7 mm Hg in those with ROSC. Differences were also found for the maximal aortic relaxation pressure, the compression-phase aortic-to-right atrial gradient, and the arterial PO2. No patient with an initial CPP less than 0 mm Hg had ROSC. Only patients with maximal CPPs of 15 mm Hg or more had ROSC, and the fraction of patients with ROSC increased as the maximal CPP increased. A CPP above 15 mm Hg did not guarantee ROSC, however, as 18 patients whose CPPs were 15 mm Hg or greater did not resuscitate. Of variables measured, maximal CPP was most predictive of ROSC, and all CPP measurements were more predictive than was aortic pressure alone. The study substantiates animal data that indicate the importance of CPP during cardiopulmonary resuscitation.

Aorta↗
PubMed1990

Effect of epinephrine on end-tidal carbon dioxide monitoring during CPR.

End-tidal carbon dioxide (ETCO2) has been shown to correlate with coronary perfusion pressure (CPP) during CPR and has been proposed as a useful noninvasive monitor of CPR efficacy. The effects of therapeutic epinephrine dosing on ETCO2 and CPP in six dogs were examined. Ventricular fibrillation was induced and left untreated for five minutes before CPR was initiated. After five minutes of CPR, epinephrine 0.045 mg/kg IV was administered. CPP and ETCO2 were compared immediately before and two minutes after epinephrine administration. There was a significant increase in CPP from 12.2 +/- 9.6 to 26.8 +/- 7.1 mm Hg (P = .006) after epinephrine. This was accompanied by a significant decrease in ETCO2 from 8.2 +/- 2.9 to 3.8 +/- 2.0 mm Hg (P = .01). These data indicate that after epinephrine administration, caution must be exercised in using ETCO2 as an indicator of CPP.

Animals↗
PubMed1990

Characterization of cerebral energetics and brain pH by 31P spectroscopy after graded canine cardiac arrest and bypass reperfusion.

Recovery of cerebral energy metabolism is used to indicate CNS viability after ischemia. This study utilized 31P nuclear magnetic resonance (NMR) spectroscopy to measure cerebral energy state and intracellular pH in dogs subjected to 8, 12, or 16 min of cardiac arrest and reperfusion using cardiopulmonary bypass. Spectra were obtained throughout ischemia and initial reperfusion and repeated at 30 and 144 h post ischemia. Neurologic deficit scoring was performed at 12 and 24 h post insult and then daily. High-energy phosphates were depleted by the end of all ischemic intervals. Recovery occurred within 60 min of reperfusion and persisted with no differences in the rate of return between groups (p greater than 0.05). Brain pH (pHb) decreased by the end of ischemia in all groups (p less than 0.0001). Neither the pHb nadir nor its recovery differed between groups (p greater than 0.05). Although longterm neurologic outcome differed between groups, the spectra were similar. Assessment of cerebral energy state using 31P NMR spectroscopy does not appear to be a sensitive indicator of neurologic outcome after global ischemia in dogs. Return of high-energy phosphates may be a necessary but not sufficient condition for cerebral recovery after ischemia. The return of high-energy phosphates after a 16-min cardiac arrest, however, indicates a potential for neurological recovery.

Acid-Base Equilibrium↗
PubMed1990

Plasma epinephrine levels in resuscitation with cardiopulmonary bypass.

Since the highest plasma epinephrine levels have been recorded during resuscitation, we evaluated the isolated effect of cardiac arrest upon adrenomedullary secretion. We determined plasma epinephrine in dogs resuscitated with cardiopulmonary bypass (CPB) after cardiac arrest periods of 12 (CPB-12; n = 4) or 16 min (CPB-16; n = 5). Through 2 h of CPB and the following 6 h of critical care, there was no difference between CPB-12 and CPB-16 regarding most cardiopulmonary functional variables. Plasma epinephrine was markedly elevated immediately after initiation of CPB (p less than .01 at 1 min CPB vs. basal) and returned rapidly to basal concentrations. Comparison of plasma epinephrine levels between CPB and standard CPR groups showed that responses to cardiac arrest were similar (p greater than .05 at 1 min CPB vs. 11.5 min CPR). We conclude that cardiac arrest is the main or sole determinant of the plasma epinephrine elevation of resuscitation.

Animals↗
PubMed1989

The effect of cardiopulmonary bypass resuscitation on cardiac arrest induced lactic acidosis in dogs.

The adequacy of end organ blood flow following a cardiac arrest varies depending on the artificial reperfusion technique utilized and may critically affect patient outcome. Both oxygen consumption (VO2) and arterial lactate values have previously been used to assess tissue perfusion. Cardiopulmonary bypass resuscitation (CPB) is a reperfusion technique capable of providing near normal end organ blood flow. The purpose of this investigation was to study the effect of femoro-femoral veno-arterial CPB resuscitation compared to standard CPR on VO2 and arterial lactic acid values after a prolonged cardiac arrest. Ten mongrel dogs were electrically fibrillated and left in cardiopulmonary arrest without therapy for 12 min. Resuscitation was attempted according to a standardized protocol utilizing either CPB (n = 5) or standard external CPR (n = 5). Oxygen consumption values and arterial lactic acid samples were obtained at baseline, at timed intervals throughout resuscitation and after return of spontaneous circulation in successfully resuscitated dogs. Baseline hemodynamic and biochemical measurements were similar in both treatment groups (P greater than 0.05). Oxygen consumption (440 +/- 50 ml/min/M2) and mean arterial lactic acid values (7.44 +/- 2.25 mmol/l) were significantly higher at 1 min of resuscitation in CPB-treated dogs compared to dogs treated with CPR (60 +/- 10 ml/min/M2) (3.16 +/- 0.69 mmol/l) respectively (P less than 0.05). Mean arterial lactic acid values rose significantly at each sampling interval during CPR (P less than 0.05) but began to decrease after 5 min of resuscitation in the CPB animals and were not significantly different than baseline after 60 min of bypass (P greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis, Lactic↗
PubMed1989

The effect of CO2 and non-CO2-generating buffers on cerebral acidosis after cardiac arrest: A 31P NMR study.

There is controversy regarding the use of alkalinizing agents during reperfusion after cardiac arrest. The potential deleterious effects of sodium bicarbonate (bicarb) administration, including paradoxic cerebral acidosis, have led to the search for alternative agents. Tromethamine (tris) is a non-CO2-generating buffer that has been proposed for use during cardiopulmonary resuscitation. The purpose of this experiment was to compare the ability of tris with bicarb to correct brain pH (pH B) during reperfusion after a 12-minute cardiac arrest. Adult mongrel dogs were instrumented and placed in the bore of a Bruker Biospec 1.89 tesla superconducting magnet system. Ventricular fibrillation was induced; after 12 minutes, cardiopulmonary bypass was initiated and maintained for two hours with minimum flows of 80 mL/kg/min. Bicarb (n = 5) or tris (n = 5) were administered to correct arterial pH as rapidly as possible. 31P NMR spectra were obtained at baseline and throughout ischemia and reperfusion. The pH B was determined with the inorganic phosphate relative to the phosphocreatine resonance signal shift. Profile analysis indicates a difference between groups (P less than .02) related to an initial delay in pH B correction in the tris group. By 48 minutes of reperfusion, pH B did not differ between the groups. Moreover, there was no evidence of paradoxic cerebral acidosis in the bicarb group. Although tris corrects blood pH as quickly as bicarb, it is less effective in correcting pH B. Absence of paradoxic acidosis may be caused by efficient elimination of CO2 by cardiopulmonary bypass.

Acidosis↗
PubMed1989

CPR-dependent consciousness: evidence for cardiac compression causing forward flow.

We present the case of a patient with cardiac arrest and resuscitation in whom, consistent with direct cardiac compression, large aortic-to-right atrial systolic pressure gradients occurred. Forward blood flow during CPR was sufficient for the patient to maintain consciousness. Although aortic-to-right atrial diastolic gradients adequate to maintain coronary perfusion in experimental models were generated, in our patient, cardiac function could not be restored and the resuscitation was ultimately unsuccessful.

Blood Circulation↗
PubMed1989

Simultaneous aortic, jugular bulb, and right atrial pressures during cardiopulmonary resuscitation in humans. Insights into mechanisms.

Pressure gradients across and between the head and chest were studied during mechanical cardiopulmonary resuscitation (CPR) in 22 humans. Patients in medical cardiac arrest, managed by ACLS guidelines, underwent placement of aortic arch (Ao), jugular venous bulb (JVB), and right atrial (RA) catheters. Simultaneous pressures were measured, and intercatheter gradients were calculated. The JVB to RA pressure difference is the gradient between the cervical and central venous circulations. It was negative when averaged throughout the CPR cycle and was more negative during compression than relaxation, -19 +/- 12 and -2 +/- 6 mm Hg, respectively. This indicates that the intrathoracic pressure rise was not transmitted to the jugular venous system, supporting the concept of a competent jugular valve mechanism during CPR. It is consistent with the thoracic pump model of cerebral perfusion. JVB to RA was positive only during early relaxation, allowing blood return from the head. The Ao to JVB gradient, although not equal to cerebral perfusion pressure, is the maximum potential pressure gradient for blood flow across the cerebral vasculature. It was positive throughout CPR, 25 +/- 17 during compression, and 9 +/- 10 mm Hg during relaxation. The Ao to RA gradient during the relaxation phase is CPR coronary perfusion pressure. In most patients, it was minimally positive in both phases of the CPR cycle: 7 +/- 14 in compression and 7 +/- 9 mm Hg during relaxation. This appears to be inadequate in providing sufficient blood flow to meet the metabolic needs of the myocardium. Four patients had larger gradients during compression suggestive of cardiac compression.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Evaluation of a new chemical dip strip for detecting ketonemia in the emergency setting.

The utility of a new urine dipstick, Chemstrip uK, was evaluated using serum in place of urine to quantify serum ketones in 29 acutely ill patients with suspected ketosis treated in the emergency department. The serum Chemstrip uK method accurately predicted the level of ketonemia as assessed by the Acetest tablet method (r = .94; P less than .0001). There were no false-negative and no false-positive results. The use of this strip is recommended for evaluating subjects with suspected ketosis.

Adolescent↗
PubMed1987

Cardiopulmonary bypass vs CPR as treatment for prolonged canine cardiopulmonary arrest.

Although in vitro studies have demonstrated functional recovery of neurons after prolonged ischemia, in vivo experience with patients resuscitated from cardiopulmonary arrest demonstrates much less cerebral resistance to global ischemia. The purpose of our investigation was to compare the effectiveness of femoro-femoral veno-arterial cardiopulmonary bypass (CPB) to standard cardiopulmonary resuscitation in the treatment of prolonged cardiopulmonary arrest. Ten mongrel dogs were electrically fibrillated and left in cardiopulmonary arrest without any therapy for 12 minutes. Subsequently, either CPB (n = 5) or CPR (n = 5) was initiated and resuscitation attempted according to a standardized protocol that included administration of the calcium channel blocker lidoflazine in an effort to optimize cerebral and myocardial recovery. If there was return of spontaneous circulation, the animal was managed in an intensive care setting with invasive hemodynamic monitoring and ventilatory support for up to nine hours. Neurologic function was graded using a standardized neurologic deficit scoring (NDS) system at 12 hours after insult and daily for one week or until death. Prearrest hemodynamic and metabolic parameters were comparable in both groups (P greater than .05). All CPB animals were resuscitated successfully and alive at 24 hours after insult as opposed to none in the CPR group (P less than .005). In addition, three of the CPB animals were neurologically normal at final grading with NDS scores of zero. The other two CPB animals had persistent severe neurologic impairment and a mean NDS score of 51%. Thus CPB is more effective than CPR in the treatment of prolonged cardiopulmonary arrest. The improved outcome probably results primarily from improvement in blood flow with CPB.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗