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Biomedical subjects

M F Roizen

Publications and source records attributed to M F Roizen.

At least 145 records · Page 8Linked to original sources
PubMed1983

Ketamine, catecholamines, and uterine tone in pregnant ewes.

Blood levels of ketamine, measured in both mother (1,230 ng/ml at 1 minute) and fetus (470 ng/ml at 1 minute) illustrate not only rapidly decreasing levels of the drug after its intravenous administration but also its transplacental passage. Concentrations of norepinephrine, epinephrine, and dopamine did not change in the mother or fetus after ketamine, with the exception of maternal levels of epinephrine, which were significantly higher at 45 minutes than control values (p less than 0.05). Maternal effects of ketamine consisted of increases in mean arterial pressure (7% p less than 0.05), cardiac output (16% p less than 0.01), and respiratory acidosis, all of which were slight and transitory. Although resting uterine tone increased (39% p less than 0.01), the uterine blood flow remained constant. None of the physiologic alterations could be correlated with changes in catecholamine levels. Therefore, the cardiovascular and uterine stimulating properties of ketamine at a dose of 0.7 mg/kg are small and are not the result of increased catecholamine levels in plasma. Further studies are necessary to elucidate the mechanism.

Acidosis, Respiratory↗
PubMed1983

Post-ganglionic chemical sympathectomy of the cat nictitating membrane following systemic epinephrine: degeneration of nerve terminals followed by regeneration.

The present study was designed to provide further evidence that high doses of systemically administered epinephrine can result in a post-ganglionic chemical sympathectomy and to look for evidence of regeneration of nerve terminals. Three days following the systemic administration of a high dose of epinephrine a prolapse of the cat nictitating membrane was observed. Examination of the inferior smooth muscle associated with the membrane revealed ultrastructural evidence of nerve terminal destruction which was associated with a marked depletion of endogenous norepinephrine as measured with a catecholamine radioenzyme assay. Three weeks following treatment, appearance of nerve terminals and endogenous norepinephrine levels in the contralateral nictitating membrane were indistinguishable from untreated controls. High doses of epinephrine appear to result in nerve terminal degeneration, followed by regeneration, similar to that reported following 6-hydroxydopamine.

Animals↗
PubMed1983

Effect of thiopental induction on sympathetic activity.

Several recent studies with different anesthetic agents have reported increases in plasma norepinephrine concentration during induction. To determine if induction with intravenous injection of thiopental also is associated with initial sympathetic activation, 24 ASA class I patients were assigned randomly to receive one of the following anesthetics: Group I, thiopental 3 mg/kg, iv, followed by inhalation of 100% oxygen and a continuous intravenous infusion of thiopental 0.2-0.3 mg X kg-1 X min-1; Group II, thiopental 3 mg/kg followed by inhalation of halothane (1.5% end-tidal concentration) in oxygen; and Group III, thiopental 3 mg/kg followed by inhalation of 70% nitrous oxide in oxygen. After thiopental injection, ventilation was controlled to maintain PCO2 near control levels. In Group I, plasma norepinephrine concentration decreased with continued administration of thiopental. This decrease became statistically significant (P less than 0.05) 10 min after injection. Plasma epinephrine concentration did not change. For Groups II and III, both plasma norepinephrine and epinephrine concentration did not change. For Groups II and III, the stability of the catecholamine concentrations during induction may have been caused by the circumvention of the second stage of anesthesia, equal depression of both inhibitory and excitatory synapses, or the combined effects of the agents. Regardless of the cause, the use of a modest induction dose of thiopental appears to allow the induction of anesthesia without sympathetic activation. When it is important to prevent sympathetic activation, administering a modest dose of thiopental before the inhalation of halothane or nitrous oxide may be preferable to inducing anesthesia with inhalation agents or narcotics alone.

Adult↗
PubMed1983

Ptosis in the rat following topically administered 2% epinephrine.

Commercially available 2% epinephrine instilled twice daily in one eye of 15 rats resulted in ptosis after 4 weeks treatment. The ptosis was indistinguishable from that observed following topical treatment with 6-hydroxydopamine 20% and surgical sympathectomy. Ptosis in both epinephrine- and 6-hydroxydopamine-treated rats was associated with a statistically significant depletion of ocular norepinephrine, as determined by a sensitive catecholamine radio enzyme assay. Ultrastructural evidence of nerve terminal degeneration was present near the smooth muscle of Müller within the eyelid of rats treated with epinephrine. This study provides further evidence epinephrine administration can result in chemical sympathectomy as has been described following 6-hydroxydopamine.

Administration, Topical↗
PubMed1983

The effect of alpha-adrenergic blockade on cardiac performance and tissue oxygen delivery during excision of pheochromocytoma.

To establish criteria for administration of the optimal dose of alpha-adrenergic receptor blocking drugs, we studied cardiac performance and tissue oxygen tension in three patients who underwent excision of pheochromocytoma. Subcutaneous oxygen tension was measured by the method of Niinikoski and Hunt. Cardiac function was assessed by thermodilution cardiac output, systemic and pulmonary arterial blood pressures, and continuous two-dimensional transesophageal echocardiography of a cross section of the left ventricle at the level of the papillary muscles. Despite large changes in cardiac output and systemic, pulmonary, and wedge pressures, intraoperative tissue oxygen tensions and ejection fractions remained normal (even at times of peak catecholamine excretion and very abnormal wedge pressures). Studies of healthy animals that received no alpha-adrenergic receptor blocking drugs showed major decrements of tissue oxygen in response to modest doses of epinephrine. We conclude that progressive administration of alpha-adrenergic receptor blocking drugs does not absolutely protect the patient from major changes in blood pressure during operation for pheochromocytoma, but that cardiac performance and oxygen supply to the tissues are unimpaired.

Adrenal Gland Neoplasms↗
PubMed1982

A comparison of T4 and T7 dermatomal levels of analgesia for caesarean section using the lumbar epidural technique.

We compared analgesia to the T4 dermatomal level with analgesia to the T7 level with and without prophylactic intramuscular administration of ephedrine 25 mg to determine the adequacy and side effects of such analgesia for caesarean section. Unmedicated patients were prehydrated (727 +/- 303 ml of saline solution) and kept in a left lateral tilt position. Sufficient three per cent chloroprocaine was given to obtain analgesia to the T7 (T6-T8) dermatomal level (455 +/- 128 mg) or to the T4 (T3-T5) dermatomal level (758 +/- 168 mg). Patients who received analgesia to the higher level required less narcotic than those who received analgesia to the lower level (21 per cent versus 48 per cent) (p less than 0.05). The incidence of hypotension in patients with analgesia at the T4 level was 21 per cent for those receiving ephedrine and 64 per cent for those who did not receive ephedrine (p less than 0.05). Intramuscular administration of ephedrine 25 mg was not associated with increased plasma levels of norepinephrine, epinephrine or dopamine. There was no difference in Apgar score, behavioural test scores, neonatal acid-base status or oxygenation in children of mothers in the different groups. We conclude that a T4 dermatomal level of analgesia combined with intramuscular administration of ephedrine 25 mg, provides more maternal comfort than a T7 level of analgesia does, with or without ephedrine, and is without significant maternal or foetal side effects.

Acid-Base Equilibrium↗
PubMed1982

Induction of anesthesia with halothane increases plasma norepinephrine concentrations.

In seven unstimulated, unmedicated patients given halothane/O2 via face mask, plasma norepinephrine concentration increased 15 min after induction and returned to control at 45 to 60 min. Changes in plasma norepinephrine levels did not correlate with changes in cardiovascular variables. In 10 additional awake, unpremedicated patients, plasma norepinephrine concentration did not change during 5 min of application of 100 per cent oxygen via face mask, but rose with subsequent administration of halothane and nitrous oxide. Again, changes in plasma norepinephrine did not correlate with changes in cardiovascular variables. The authors perfused seven isolated cat spleens with a Krebs-Ringer's lactate solution. Addition of 0.01 atm halothane to the perfusate initially increased release of norepinephrine into the effluent. The authors conclude that halothane or halothane-nitrous oxide initially increases plasma norepinephrine during induction of anesthesia. This increase is not due to the placement of a face mask, but may relate to an effect of halothane at sympathetic nerve endings.

Adolescent↗
PubMed1981

Anesthetic doses blocking adrenergic (stress) and cardiovascular responses to incision--MAC BAR.

The reaction to stress, while vital to the conscious animal, may be detrimental to the surgical patient. To assess the stress-ablating action of different anesthetics (halothane, enflurane, morphine, and spinal) and anesthetic doses, we studied the responses in plasma norepinephrine, muscle movement, pupil diameter, heart rate, and blood pressure to induction of anesthesia and incision in 170 unpremedicated healthy adults. The age-adjusted dose (mean +/- SD) of anesthesia that blocked the adrenergic response in 50 per cent of individuals who had a skin incision (MAC BAR) was 1.45 +/- 0.08 MAC for halothane, 1.60 +/- 0.13 MAC for enflurane, or 1.13 +/- 0.09 +/- mg/kg for morphine sulfate (each anesthetic was given with 60 per cent nitrous oxide). No patient with a level of spinal anesthesia that blocked the pain of incision had an adrenergic response to incision. Increasing doses of halothane and morphine were associated with less of a cardiovascular response to incision (as measured by rate-pressure product); this was not true for enflurane. No patient with an adequate level of spinal anesthesia had a cardiovascular response to skin incision. The changes in heart rate, blood pressure, rate-pressure product, and plasma norepinephrine content that occurred with induction of anesthesia tended to equalize these values between patients, regardless of anesthetic dose, and for all individual and combined anesthetics. That is, if a patient's heart rate while awake was below 63 beats/min, heart rate tended to rise 58 per cent of the difference between heart rate while awake and 63 beats/min, and vice versa. Similarly, the change in blood pressure with induction averaged 75 per cent of the difference between systolic blood pressure while awake and 88 torr. The average for the change in rate-pressure product with induction was 79 per cent of the difference between rate-pressure product while awake and 5917 torr.beats/min. It was concluded that all the anesthetics tested can prevent the neuroendocrine response to skin incision at clinically attainable doses. Thus, comparisons of neuroendocrine stress during surgery require quantitation of anesthetic dose. If adverse effects of surgery are related to the neuroendocrine stress that surgical manipulations induce, the hypothesis "the less anesthetic the better" may be wrong.

Adolescent↗
PubMed1980

Localization of functioning pheochromocytomas by venous sampling and radioenzymatic analysis.

The authors describe a sensitive radioenzymatic technique for determining blood catecholamines which is very effective in localizing occult functioning pheochromocytomas. It appears to be more consistent than any other technique in demonstrating theirapproximate location. Combined with other noninvasive studies such as CT, it should greatly facilitate demonstration of extra-adrenal pheochromocytomas, thereby reducing the need for more invasive procedures such as arteriography.

Adolescent↗
PubMed1980

Postoperative respiratory care: a controlled trial of early and late extubation following coronary-artery bypass grafting.

Sequelae of early versus late extubation of the trachea in patients following coronary-artery bypass grafting were compared prospectively in 38 patients randomly assigned to one of the two groups. The times to extubation were 2 +/- 2 and 18 +/- 3 hours after operation for the two groups. Comparisons were made between groups for the following five variables: time spent in the intensive care unit; drug utilization in the intensive care unit; cardiopulmonary morbidity; hemodynamic performance; patient stress (plasma norepinephrine levels). The anesthetic technique consisted of induction with thiopental, nitrous oxide, and halothane, followed by maintenance with nitrous oxide and halothane. Pancuronium was the only muscle relaxant administered. Patients whose tracheas were extubated early had muscle relaxants reversed prior to the application of extubation criteria. There was no significant difference between the groups in times spent in the intensive care unit, hemodynamic performances, or plasma norepinephrine levels; however, the patients whose tracheas were extubated early received less morphine and diazepam and suffered significantly less cardiopulmonary morbidity.

Aged↗
PubMed1980

Operating room temperature prior to surgical draping: effect on patient temperature in recovery room.

Assessment was made of whether a cold-room environment prior to surgical draping affected patient temperature or the incidence of shivering in the recovery room in patients undergoing major vascular surgery when warming blankets and warmed fluids were used to maintain intraoperative temperature. Forty-two patients scheduled to undergo major vascular surgery were randomly assigned in equal numbers to a "cold or "warm" room. Temperatures in the "warm" rooms were 22.2 C or above (range 22.8-25.6 C) until draping, and in "cold" rooms, 18.9 C or below (ranged 13.9-17.8 C). Once surgical drapes were placed, the room temperature control was set at its minimum, 17 C. All intravenous fluids and blood were warmed to 37.5 C, and a heating blanket was maintained at 37.8 C before and during the operative procedure. Patient temperatures initially did not differ between groups. Despite significantly greater heat loss prior to draping in the cold-room group (0.63 +/- 0.14 C) than in the warm-room group (0.32 +/- 0.10 C) (p < 0.01), there were no differences in temperature in the recovery room, shivering, myocardial, renal CNS, pulmonary, or graft morbidity in the two groups. In major intra-abdominal vascular operations the use of warming blankets and the practice of warming all fluids for infusion allow a comfortable room temperature without detriment to patient care.

Body Temperature↗