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Biomedical subjects

S Muravchick

Publications and source records attributed to S Muravchick.

At least 19 recordsLinked to original sources
PubMed2000

Preoperative assessment of the elderly patient.

Organ system functional reserve variability increases progressively with age. In elderly patients, cardiopulmonary, central nervous system, and metabolic functional reserve seem to be the most important predictors of the ability to undergo surgery. Directed testing for the assessment of organ system functional reserve and identification of organs at risk, rather than the diagnosis of disease itself, is the primary goal of preoperative evaluation prior to surgery and is essential to the formulation of an effective anesthetic plan. The risks of adverse drug interaction, already high in the elderly, make a thorough review of the indications and dosage of perioperative medication an important part of the preoperative assessment process.

Aged↗
PubMed1998

The effects of aging on anesthetic pharmacology.

Aging alters both the pharmacokinetic and the pharmacodynamic aspects of anesthetic requirement. Studies of the relationship between drug concentration and effect in older adults clearly demonstrate a decline in median effective dose requirement for agents that act within the central nervous system, but there appears to be little change in the dose required for peripheral effects such as neuromuscular blockade. Most drugs also undergo somewhat slower biotransformation and demonstrate prolonged clinical effects if they require hepatic or renal degradation, although many newer agents such as remifentanil and cisatracurium have organ-independent pathways that are not affected by age. In some cases, however, the appearance of increased sensitivity to a given dose of anesthetic or opiate may actually reflect higher-than expected plasma concentrations of drug following a rapid intravenous injection. Therefore, it is impossible to completely separate the interactions between pharmacodynamic and pharmacokinetic factors associated with aging. The use of pharmacological sympathectomy with intrathecal agents and with sympatholytic adrenergic agonists may further improve outcome in a patient population at high risk because of reduced functional reserve, increased incidence of polypharmacy, and the consequences of age-related disease.

Adrenergic Agonists↗
PubMed1998

The aging process: anesthetic implications.

Recent improvement in our understanding of the physiology and pharmacology of aging has occurred in large part because investigators have been able to separate the effects of aging from the consequences of age-related disease. As a group, elderly patients are at increased risk of perioperative morbidity and mortality because of the high incidence of coexisting age-related disease. Even in the absence of chronic disease, organ function remains adequate to meet the basal metabolic requirements of older adults, but the functional reserve and maximal capacity of all major organ systems are significantly reduced and may not meet the increased demands associated with acute illness surgery. Increased rate and severity of perioperative complications may specifically reflect decreased autonomic homeostasis, impaired immune functions, and reduced aerobic capacity to tolerate or compensate for imposed pathology or surgical stress. Age-related chronic disease and, to a lesser extent, progressive erosion of functional capacity explain the increase in perioperative complications seen in an elderly surgical patient population. Therefore, optimal anesthetic management of elderly patients requires adequate diagnosis and treatment of concurrent diseases, meticulous attention to the details of preparation and positioning, and use of monitoring techniques that permit adjustments of drug dosage appropriate for their altered requirements for anesthetic and adjuvant drugs.

Acute Disease↗
PubMed1996

Intraoperative air embolism with pulse irrigation device.

Venous air embolism is a potentially fatal complication. In a patient undergoing extensive debridement of an open perineal wound, hemodynamically significant air embolization occurred during use of a pulsatile saline irrigation device. We describe another intraoperative setting in which venous air embolism is a risk.

Adult↗
PubMed1994

Localized hypothermia influences assessment of recovery from vecuronium neuromuscular blockade.

The purpose of this study was to determine the extent to which localized hypothermia of a monitored extremity alters the assessment of recovery from vecuronium-induced neuromuscular blockade. Bilateral integrated evoked electromyographic (IEMG) responses were measured in the ulner distribution of 14 anaesthetized patients who had differing upper extremity temperatures as measured at the adductor pollicis to determine whether localized hypothermia alters the clinical assessment of spontaneous recovery from vecuronium-induced neuromuscular blockade. All patients received general anaesthesia with thiopentone, N2O/O2 and opioid; 11/14 patients received isoflurane for blood pressure control. Bilateral adductor pollicis, oesophageal and ambient temperatures, and IEMG evoked response (t1) expressed as percent unparalyzed control were recorded during the anaesthetic. The difference in evoked response between the warmer and the colder upper extremity was calculated at 25%, 50% and 75% spontaneous recovery from neuromuscular blockade in the warm extremity. Differences in temperature between extremities ranged from 0.2-11 degrees C. The difference in IEMG-evoked response between extremities was proportional to the difference in temperature, and there was a direct correlation (r = 0.78) between IEMG response and extremity temperature; IEMG response was absent when extremity temperature was less than 25 degrees C. We concluded that localized hypothermia in the monitored extremity decreases the IEMG-evoked response to vecuronium neuromuscular blockade; the greater the temperature decrease, the less the evoked response.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Monitoring technique affects measurement of recovery from succinylcholine.

To compare recovery time from neuromuscular blockade after the administration of a single intravenous bolus of succinylcholine (1 mg/kg), we measured, both mechanically and electromyographically, the evoked twitch responses in the hand muscles of 10 patients. Electromyographic data were obtained, electronically integrated, and recorded by a newly available clinical monitoring device. Using both the mechanical and the electromyographic devices, we recorded the times for first return of twitch, as well as for 25% and 75% recovery of twitch height compared with prerelaxant twitch baseline values and compared the values by calculating least-squares regression lines. Times given by the electromyographic device for these measures of returning neuromuscular function were notably longer than those given by the mechanical evoked force monitor. No such findings have been reported in previous studies that compared these two techniques for monitoring of muscle recovery from nondepolarizing relaxants. The specific reasons for the differences found in this study are unknown.

Adult↗
PubMed1986

A departmental policy addressing chemical substance abuse.

Substance abuse is a major socioeconomic problem. However, the ready availability of potent narcotic and sedative drugs probably constitutes a unique risk for anesthesiologists. Until recently, few anesthesia departments were prepared to recognize or safely manage afflicted colleagues. Because we felt it important to educate our staff and residents and to have a response mechanism established prior to the advent of a substance abuse problem, a departmental committee was formed to develop a Substance Abuse Policy. The policy has served to increase our general awareness and to direct our actions effectively when dealing with physician impairment. It is presented here in the belief that other departments might find it useful in tailoring their approach to this problem.

Anesthesiology↗
PubMed1986

Electrical and mechanical train-of-four responses during depolarizing and nondepolarizing neuromuscular blockade.

Simultaneous measurements of train-of-four (TOF) responses by integrated electromyography (IEMG) and twitch force were compared for atracurium, vecuronium, and succinylcholine in 30 subjects during nitrous oxide-fentanyl anesthesia. Determinations of TOF were made during neuromuscular blockade (NMB) onset and recovery. Scattergrams and least squares regression lines were plotted, and z-tests for parallel slope and common intercept were used to compare lines. Data for atracurium and vecuronium were indistinguishable in all groups (z less than 0.05), and therefore pooled to represent nondepolarizing blockade. During onset of nondepolarizing NMB, TOF showed a linear relationship indistinguishable from the line of identity (slope 0.93, intercept -0.06, z less than 0.05). During recovery the intercept was unchanged (z greater than 0.05), but the slope was significantly changed, indicating mechanical TOF lags behind IEMG during recovery. This finding is important for interpretation of IEMG when used for clinical monitoring. Comparison of data for depolarizing NMB shows more complex relationships. Integrated electromyography is found to be convenient and reliable for monitoring nondepolarizing NMB.

Adult↗
PubMed1981

Temperature correction of arterial blood-gas parameters: A comparative review of methodology.

The need for accurate clinical diagnosis and appropriate intervention requires that a modern blood-gas laboratory have the means to correct for significant discrepancies between patient temperature and the temperature at which in vitro blood samples are analyzed. Recent advances in mini- and microcomputer technology permit application of any or all of the correction formulas above at modest cost and minimal inconvenience (See the Appendix). An expanded program for a TI-59 desk-top calculator and P-100C printer which gives labeled hard-copy readout of temperature-corrected pH, PCO2, PO2, and hemoglobin saturation values, as well as bicarbonate concentration and in vivo base excess is in daily clinical use in our operating room and is available from the authors upon request.

Bicarbonates↗
PubMed1981

Arterial oxygenation in conscious patients after 5 minutes and after 30 seconds of oxygen breathing.

This study compares continuously measured arterial oxygen tension (PaO2) in normal unanesthetized patients after four maximally deep breaths of 100% O2 within 30 seconds, to (PaO2) values observed after 5 minutes of spontaneously breathing 100% O2 at normal rates and tidal volumes. Mean (PaO2) after 5 minutes of O2 breathing was 350 +/- 36 (SD) torr, not significantly higher (p greater than 0.05) than after four breaths of O2 (339 +/0 34 torr). Mean arterial oxygen content was 19.6 +/- 2.1 vol % in both periods. For purposes of increasing arterial oxygenation before anesthetic induction the four-breath, 30-second technique and 5 minutes of oxygen breathing are equally effective.

Adult↗
PubMed1981

Arterial oxygenation during laryngoscopy and intubation.

Arterial oxygenation during laryngoscopy and tracheal intubation was studied in 37 patients, 22 taking four maximally deep breaths of O2 within 30 seconds, and 15 breathing air immediately before anesthetic induction. In both groups of patients induction was followed by ventilation with 100% O2 by face mask before laryngoscopy, which was followed by intubation. Both mean arterial O2 tension (PaO2) and mean arterial O2 content (CaO2) increased significantly after four breaths of O2 in 30 seconds (339 +/- 34 (SD) vs 77 +/- 5, p less than 0.05, and 19.6 +/- 2.1 vs 18.8 +/0 2.1, respectively, p less than 0.05). At the end of laryngoscopy, mean PaO2 remained significantly greater in preoxygenated patients than in air-breathing patients (353 +/- 33 torr vs 319 +/- 26 torr, respectively, p less than 0.05). After intubation, mean PaO2 in preoxygenated patients remained higher than in air-breathing patients (332 +/- 34 vs 289 +/- 23 torr, p less than 0.05). Calculated mean CaO2 was not significantly different for the two groups during either maneuver. We conclude that four breaths of O2 in 30 seconds before anesthetic induction elevates PaO2 but provides insignificant improvement in CaO2 during laryngoscopy and intubation when the anesthetic routine includes ventilation of the patient with O2 by face mask after induction and before laryngoscopy.

Adult↗