PubMed Health⌕ Search

Biomedical subjects

R N Sladen

Publications and source records attributed to R N Sladen.

18 recordsLinked to original sources
PubMed1992

The effect of the extended (3-year) anesthesia curriculum on anesthesia subspecialty education.

The purpose of this study was to determine the effect of lengthening the anesthesia residency by the American Board of Anesthesiology on the education of anesthesia subspecialists. A survey of anesthesia residency programs was conducted from 1987 to 1991. The most frequent subspecialty practice in the clinical anesthesia (CA) 3 year is cardiovascular anesthesia. However, the percentage of CA3 residents spending extended time (greater than or equal to 6 months) in subspecialty education has significantly decreased. For example, the percentage of CA3 residents spending 12 months in subspecialty education has decreased 83%. There appears to be a slight increase in the number of CA4 or PGY5 residents (fellows) electing subspecialty practice. It is concluded that the 3-year curriculum has produced a negative impact on the education of anesthesia subspecialists.

Anesthesiology↗
PubMed1992

Use of patient-controlled analgesia to compare the efficacy of epidural to intravenous fentanyl administration.

Fentanyl, unlike morphine, is highly lipophilic and rapidly diffuses out of the epidural space. Respiratory depression is, therefore, unlikely when fentanyl is given epidurally. However, much of fentanyl's analgesic effect is mediated by systemic rather than spinal receptor binding. To test this hypothesis, we performed a prospective, double-blind, cross-over study comparing epidural and intravenous (IV) administration of fentanyl in 16 patients for the first 12 h after lower abdominal or lower extremity surgery. To allow direct comparison of these two routes of administration, patient-controlled analgesia was used so patients could self-titrate their analgesia. Patients were randomized to receive fentanyl initially by an epidural (group A, n = 8) or IV (group B, n = 8) catheter for 6 h, after which they were crossed-over to the alternate route by means of a hidden three-way stopcock. The degree of analgesia was subjectively evaluated by a visual analogue scale, and by an observer rating patient's comfort and sedation. Cumulative dosage of fentanyl was recorded, and plasma fentanyl concentrations were measured. The onset of analgesia and increase in plasma fentanyl concentrations were more rapid with intravenous fentanyl. However, after 60 min, analgesia (visual analogue scale 2-4 cm) or plasma fentanyl concentrations (0.3-0.7 ng/mL) did not differ between the two routes of administration. There were also no significant differences in the cumulative dosage of fentanyl within each group (epidural vs IV) or between the groups. Thus, the analgesic effects of epidural fentanyl appear largely mediated by systemic absorption. Intravenous fentanyl achieves a similar degree of analgesia and a more rapid onset of effect without the need for epidural catheterization.

Aged↗
PubMed1992

Postoperative hypertension: a multicenter, prospective, randomized comparison between intravenous nicardipine and sodium nitroprusside.

OBJECTIVE: To compare the efficacy and safety of iv nicardipine with sodium nitroprusside in the treatment of postoperative hypertension after both cardiac and noncardiac surgery. DESIGN: Multicenter, prospective, randomized, open-label study. SETTING: Six tertiary referral medical centers (recovery rooms and surgical ICUs). PATIENTS: A total of 139 patients with postoperative hypertension: i.v. nicardipine (n = 71), sodium nitroprusside (n = 68). INTERVENTION: Administration of i.v. nicardipine or sodium nitroprusside. MEASUREMENTS: Vital signs (BP, heart rate), hemodynamic variables, medication dosage, total number of dose changes, and time to achieve BP control were recorded. MAIN RESULTS: Both medications were equally effective in reducing BP in both the cardiac and noncardiac surgical groups. Under the conditions of the study, i.v. nicardipine controlled hypertension more rapidly than sodium nitroprusside (i.v. nicardipine 14.0 +/- 1.0 mins and sodium nitroprusside 30.4 +/- 3.5 mins, p = .0029). The total number of dose changes required to achieve therapeutic BP response was significantly less in the i.v. nicardipine-treated patients (i.v. nicardipine 1.5 +/- 0.2 vs. sodium nitroprusside 5.1 +/- 1.4, p < .05). Adverse effects were observed with both drugs (i.v. nicardipine 7% [5/71] and sodium nitroprusside 18% [12/68] [NS]). CONCLUSIONS: Intravenous nicardipine is as effective as sodium nitroprusside in the therapy of postoperative hypertension. Specific advantages have been identified. The use of i.v. nicardipine should be considered in the therapy of postoperative hypertension.

Aged↗
PubMed1990

Labetalol for the control of elevated blood pressure following coronary artery bypass grafting.

In a multicenter study, the efficacy and safety of intravenous (IV) labetalol for the control of elevated blood pressure were studied in the intensive care unit (ICU) in 65 patients within 4 hours following coronary artery bypass grafting (CABG). Patients with pre-existing ventricular dysfunction, bradycardia, bronchospastic disease, or postoperative complications were excluded. All patients were monitored with a thermodilution pulmonary artery catheter. Entry criteria were a systolic blood pressure (SBP) greater than 140 mm Hg or diastolic blood pressure (DBP) greater than 90 mm Hg for at least five minutes. Intravenous labetalol was loaded incrementally (5, 10, 20, and 40 mg at 10-minute intervals) to a maximum cumulative dose of 75 mg, until either SBP decreased 10% or DBP decreased 10% and was less than 90 mm Hg. Responders were entered into a 6-hour maintenance period, and received 5 to 40 mg of IV labetalol every 10 minutes as needed for blood pressure control. Hemodynamic data and temperature were recorded at baseline, just before each dose of labetalol during the loading period, and at the end of the maintenance period. Alternative therapy was given in the case of nonresponse or adverse events. Intravenous labetalol successfully controlled post-CABG hypertension in 55 of 65 patients (85%); of these, 46 responded to 35 mg or less. Although 28 patients required no further labetalol in the maintenance period, in the others dosage varied from 5 to 400 mg. Reductions in SBP and DBP were associated with moderate reductions in pulse pressure (SBP-DBP) and heart rate (HR). Cardiac index decreased by 18.5%, with a 12.5% decrease in stroke index and 8.1% decrease in HR. Systemic vascular resistance did not increase significantly. Four patients (6%) developed hypotension related to IV labetalol. There was one death due to perioperative myocardial infarction, which was unrelated to labetalol use. The mechanism of action of IV labetalol in controlling hypertension after CABG surgery seems to be moderate negative inotropy and chronotropy. Its alpha-blocking effects seem to be important in preventing reflex vasoconstriction. This is directly opposite to the primary vasodilator effect found when IV labetalol is used to control nonsurgical hypertension. Because of these actions, labetalol should be avoided or used with caution in patients with preoperative and postoperative cardiac dysfunction. In patients with normal left ventricular function, IV labetalol appears to be a safe, effective agent in controlling post-CABG hypertension, with the added potential benefit of enhanced myocardial oxygen balance.

Analysis of Variance↗
PubMed1990

Nicardipine infusion for postoperative hypertension after surgery of the head and neck.

The therapy of postoperative hypertension (POH) after head and neck surgery was evaluated in a prospective, randomized, double-blind trial. Nicardipine hydrochloride, a Ca channel-blocker for iv use, was compared with placebo. Patients were initially randomized to receive nicardipine infusion or placebo. Those not responding to placebo were given nicardipine infusion on an open basis. Hypertension was significantly better controlled in patients treated with nicardipine infusion compared with placebo (83% vs. 22%, p less than .002). Subsequently, six (86%) of seven of the placebo failures were successfully treated with nicardipine. There were no significant complications in either group. We conclude that the titratable infusion of nicardipine is an effective and safe method for the control of POH after surgery of the head and neck. Further studies are now warranted comparing nicardipine with other drugs currently used to treat this condition.

Blood Pressure↗
PubMed1990

Colorimetric end-tidal carbon dioxide monitoring for tracheal intubation.

We evaluated a colorimetric end-tidal carbon dioxide (ETCO2) detector (FEF end-tidal carbon dioxide detector, Fenem, New York, N.Y.) during 62 intubations in anesthetized patients who were hemodynamically stable. The intubations were performed during a drill that simulates difficult tracheal intubation and therefore is associated with an increased risk of esophageal intubation. Each intubation attempt was monitored by two anesthesiologists and a research assistant who together used chest auscultation, colorimetric ETCO2, and capnography to confirm tracheal intubation and detect esophageal intubation. The reliability of the monitors was compared with capnography. Colorimetric ETCO2 confirmed tracheal intubations and detected esophageal intubations 100% of the time, as judged by capnography. There were no false-positive or false-negative decisions based on endotracheal tube position; however, one equivocal color change occurred, which was caused by failure to inflate the endotracheal tube cuff. Colorimetric ETCO2 monitoring confirmed tracheal intubation more rapidly than did chest auscultation (P less than 0.001) or capnography (P less than 0.05), and detected esophageal intubation more rapidly than did chest auscultation (P less than 0.05) and as rapidly as capnography did. Confirmation of tracheal intubation was achieved earlier than detection of esophageal intubation with all three monitors (P less than 0.05). We conclude that colorimetric ETCO2 monitoring is a safe, reliable, rapid, simple, and portable method for determining endotracheal tube position for patients who are hemodynamically stable and should be recommended where capnography is not available.

Carbon Dioxide↗
PubMed1989

Blood conservation in cardiac surgery. Preliminary results with an institutional commitment.

To evaluate the effect of blood conservation in cardiac surgery, use of blood products was analyzed in patients undergoing CABG before and after implementation of blood conservation techniques. Age, sex, coronary anatomy, ejection fraction, cardiopulmonary bypass time, and the preoperative hematocrit, platelet count, and clotting studies were similar in both groups. Methods of blood conservation included autologous transfusion of blood withdrawn before bypass, autotransfusion of shed mediastinal blood, strict protocols for transfusion, and acceptance of normovolemic anemia. With blood conservation, 25.5% of patients received no transfusions and 54.9% received blood only. Significant reductions (p less than 0.001) were achieved in the transfusion of blood from 6.8 +/- 2.4 to 2.3 +/- 2.6 units per patient and of plasma from 2.5 +/- 2.2 to 0.6 +/- 2.0 units per patient. Reductions in the use of platelets and cryoprecipitate were substantial, although not significant. Total donor exposure was reduced significantly from 13.1 +/- 7.3 to 4.3 +/- 6.7 donors per patient. The postoperative hematocrit was significantly lower and remained so at discharge. However, 30 days later there was no difference. This reduction in transfusion requirements decreased costs and donor exposure.

Aged↗
PubMed1987

Hematologic effects of cardiac and noncardiac surgery.

The intraoperative and postoperative changes in number and type of WBCs in patients undergoing cardiac surgery were studied. These changes were then compared with those that occurred in patients undergoing four noncardiac surgical procedures (abdominal vascular reconstruction, thoracotomy, cholecystectomy, and carotid thromboendarterectomy). Both cardiac surgery and abdominal vascular surgery resulted in a marked increase in bands and decrease in lymphocytes. Thoracotomy and cholecystectomy resulted in similar but smaller changes. Carotid thromboendarterectomy did not produce hematologic changes. We conclude that the hematologic changes that occur with cardiac surgery are primarily a result of the stress and trauma of major surgery rather than a result of cardiopulmonary bypass itself.

Adult↗
PubMed1987

Effect of anesthesia and surgery on renal function.

Interpretation of the effects of anesthesia and surgery on renal function should be based on careful appraisal of the methodology used. Currently, the most accurate measurement of in vivo RBF is provided by flow probes, although thermodilution techniques show promise. In addition, the many secondary factors that affect renal responses, such as intravascular volume status and positive pressure ventilation, should be taken into consideration in evaluating any study. Normal renal function appears to be regulated by a balance between opposing neurohormonal systems which control vasomotor tone, diuresis, and natriuresis. Surgical stress tips the balance in favor of renal vasoconstriction and salt and water retention, which may last for days after operation. Recent elucidation of the role of atrial natriuretic peptide enhances the concept that these changes can be prevented or modified by maintenance of normal or increased atrial volume. Anesthetic agents generally decrease GFR and urine output. Effects of RBF are variable and probably reflect overall circulatory responses rather than direct actions. All these changes are mild and usually reversed at the end of anesthesia. Positive pressure ventilation depresses renal function through its effects on the central circulation, which can be reversed by administration of fluid or inotropic agents. Controlled hypotensive anesthesia, aortic cross-clamping, and cardiopulmonary bypass represent anticipated renal insults which should be carefully managed.

Anesthetics↗
PubMed1985

Water intoxication and hyponatremic encephalopathy from the use of an oxytocin nasal spray. A case report.

Many nursing women returning to a full-time job and desiring to continue to breast feed are using oxytocin nasal sprays to facilitate breast emptying during the work day. Very few complications have been reported from its use, and the preparation has been assumed to be innocuous. However, we encountered a nursing mother whose life appears to have been jeopardized by the excessive and unmonitored application of such a spray. The patient was hospitalized for a viral illness and given a large quantity of intravenous fluid. In association with excessive self-administration of an oxytocin nasal spray, she developed severe water intoxication, with hyponatremic encephalopathy and convulsions. During the same hospitalization the patient subsequently developed a Guillain-Barré type of peripheral polyneuritis. The syndrome of inappropriate secretion of antidiuretic hormone has been reported to accompany the neurologic manifestations of the Guillain-Barré syndrome and may have been the cause of the convulsions. However, the temporal associations in this case strongly favor the unmonitored use of the oxytocin nasal spray as etiologic.

Adult↗
PubMed1985

Temperature and ventilation after hypothermic cardiopulmonary bypass.

Rewarming in the postoperative period after hypothermic cardiopulmonary bypass is often associated with hemodynamic and ventilatory instability. Temperature changes, PaCO2 values, and delivered mechanical ventilation were observed for the first 12 hr in the intensive care unit in 73 patients who had undergone cardiac surgery with hypothermic cardiopulmonary bypass. Mean rectal temperature increased from 34.7 to 38.3 degrees C over the first 8 hr after admission to the intensive care unit (P less than 0.001). The temperature curve was sigmoid rather than linear, and the most rapid rate of temperature increase occurred 2-4 hr after admission. During rewarming, the most common abnormality of PaCO2 on mechanical ventilation was acute respiratory acidosis (PaCO2 greater than 45 mm Hg, pH less than 7.35), which occurred in 42% of patients. This suggests that ventilatory management in the early postoperative period after hypothermic cardiopulmonary bypass should be carefully adjusted to the increased metabolic rate during rapid rewarming.

Acid-Base Imbalance↗
PubMed1979

Specific afterload reduction with parenteral hydralazine following cardiac surgery.

In a group of seven patients who had had cardiac operations, intravenous (IV) hydralazine was used to provide afterload reduction in situations of severe left ventricular dysfunction. Despite fluid loading, inotropic support with dopamine, and afterload reduction with sodium nitroprusside, the patients had persistent states of low cardiac output and high systemic vascular resistance. Administration of sodium nitroprusside was limited by its effect on preload and blood pressure, so that it necessitated frequent fluid challenges. The addition of IV hydralazine to this regimen caused a mean increase of 44.7% in the stroke index and a mean reduction of 28.6% in systemic vascular resistance without significant change in pulmonary artery wedge pressure, mean arterial pressure, or heart rate. Rapid weaning of sodium nitroprusside and, on occasion, dopamine was facilitated. Frequent fluid challenges to restore preload were unnecessary. Dose requirements of hydralazine were small: 2.5 to 5.0 mg IV initially, and then a maintenance dose of 2.5 to 7.5 mg IV every 4 to 6 hours. These preliminary clinical observations indicate that in patients with low cardiac output--high resistance states and normal or elevated preload, the important benefit of specific afterload reduction may be provided by parenteral hydrolazine in the early period following cardiac surgery. Prospective, controlled studies with this agent in this situation appear warranted.

Administration, Oral↗
PubMed1978

Intermittent mandatory ventilation and controlled mechanical ventrilation without positive end-expiratory pressure following cardio-pulmonary bypass.

In a group of 18 male patients undergoing coronary artery bypass grafting with cardiopulmonary bypass, the overall incidence of post-operative atelectasis was 60%. Nearly three-quarters occurred during anaesthesia. After operation there was no difference whether CMV or IMV without PEEP was provided overnight. Atelectasis already present did not improve and further atelectasis occurred. A role for IMV is not excluded, since it facilitates the use of PEEP. Many factors operate and interact to provoke atelectasis during anaesthesia, which increases post-operative morbidity. Many of these factors are prevertible or reversible if their physiological basis is understood. Optimal post-operative ventilation should be tailored to the needs of the individual patient and demands close co-operation between anaesthetist and surgeon.

Anesthesia↗
PubMedDate not supplied

Simulation technique for difficult intubation: teaching tool or new hazard?

This investigation evaluated the risks of a simulation drill designed to improve the skill of anesthesia personnel in dealing with an unexpected difficult intubation. In a controlled prospective study, 40 patients with normal airways scheduled to undergo noncardiothoracic surgery were randomized into two groups of 20 patients. In the control group, intubation was performed by standard techniques. In the simulation group, intubation of a difficult airway was simulated and performed with the aid of an endotracheal tube introducer. Heart rate (HR); systolic, mean, and diastolic blood pressures (BPs); and arterial oxygen saturation were measured noninvasively during the preinduction period and 1 minute postintubation. A record was kept of all adverse events, including electrocardiogram (EKG) evidence of myocardial ischemia or cardiac arrhythmias, esophageal intubation, pulmonary aspiration, or tracheal injury. There were no significant differences in percent changes in HR, BP, or oxygen saturation between the two groups. There were five uncomplicated esophageal intubations in the simulation group compared with none in the control group (p = 0.001). No other adverse events were recorded. The potential hazards of esophageal intubation should be considered before this simulation drill is performed.

Adult↗