Rate-Dependent Left Bundle Branch Block in an Ambulatory Surgery Patient: A Case Report

A 52-year-old woman, ASA II (American Society of Anesthesia classification II) scheduled for cholecystectomy in an ambulatory center, exhibited a wide-complex tachycardia with ectopy on the monitor after induction with propofol and succinylcholine. Blood pressure remained stable; amiodarone was administered for presumed ventricular tachycardia. A 12-lead electrocardiogram (ECG) showed a new left bundle branch block (LBBB) at 98 beats per minute (bpm), which resolved when the heart rate slowed. Surgery was postponed, and both the LBBB and ectopy recurred frequently during the next 24 hours in the intensive care unit, particularly at heart rates >90 bpm. Troponins were normal, and the patient was diagnosed with a rate-dependent LBBB and cleared for surgery.

Performance outcomes in anesthesiology residents completing categorical (anesthesia) or advanced (nonspecific) internship training

BACKGROUND

The internship or first year (PGY 1) of anesthesiology training may be categorical (within anesthesiology), or obtained in more diverse settings. Revisions recently proposed in the training requirements incorporated the PGY 1 into the existing curriculum.

PURPOSES

We studied whether this change improved measurable outcomes.

METHODS

There were 518 residents studied retrospectively from four institutions that offered entry following both "Categorical" and "Other" internships. Thus the training in clinical anesthesia was identical.

RESULTS

No differences were observed in percentile scores on the Anesthesiology In-Service Training Examination during clinical anesthesia training, the receipt of awards, board certification or time to certification, or in reports of unsatisfactory performance to the American Board of Anesthesiology. "Categorical" residents were more frequently appointed chief resident.

CONCLUSIONS

Easily accessible performance measures may function as valuable aids in decision making, particularly when significant changes in curricula are contemplated. Data do not support the proposed changes in anesthesiology.

Coping with disaster: relocating a residency program

In September 2005, in the aftermath of Hurricane Katrina, the Tulane University School of Medicine relocated temporarily from New Orleans to the Baylor College of Medicine in Houston, Texas. For Tulane's residency program in anesthesiology, a training consortium was formed in Texas consisting of the University of Texas at Houston, Baylor College of Medicine, the University of Texas Medical Branch at Galveston, and the M.D. Anderson Cancer Center. The authors explain the collaborative process that allowed the consortium to find spaces to accommodate Tulane's 30 anesthesiology residents within 30 days after they left New Orleans, and they offer reflections and recommendations. The residents were grateful to continue training close to home, and for maintaining the Tulane program. The consortium successfully provided an administrative and academic framework, logistical support, clinical capacity for the residents to complete the required numbers and types of cases, and integration into preexisting didactic programs. Communications represented a major challenge; the importance of having an up-to-date disaster plan, including provisions for communication using more than one modality or provider, cannot be underestimated. Other challenges included resuming a training program without basic information regarding medical credentials or training status, competing for resources with businesses that had also relocated, maintaining a coordinated decision-making process, and managing the behavioral sequelae after the disaster. Of the original 30 Tulane residents, 23 (77%) relocated to Houston. Seventeen (74%) of those who relocated either graduated or returned with the program to New Orleans. The program has retained its status of full accreditation.

Increasing the value of time reduces the lost economic opportunity of caring for surgeries of longer-than-average times

Anesthesiology groups that provide care for surgical procedures of longer-than-average duration are economically disadvantaged by both increased staffing costs and reduced revenue. Under the current billing system, anesthesia time is valued the same regardless of the total case duration. In this study, we evaluated the effect on four academic anesthesiology departments of two hypothetical scenarios by changing the anesthesia care billing system to make more valuable either 1) all time units or 2) just second-hour and subsequent time units. From the four departments, case-specific data (anesthesia Current Procedural Terminology code and minutes of care) were collected for all anesthesia cases billed for 1 yr. Basic units were determined from the American Society of Anesthesiologists (ASA) relative value guide. The average time for each case was defined as the average anesthesia time for that specific Current Procedural Terminology code, as published by the Center for Medicare and Medicaid Services (CMS). The actual total ASA units per hour (tASA/h) was determined by adding all the basic units and time units and dividing by hours of anesthesia care (minutes of anesthesia care divided by 60). We then calculated a hypothetical CMS tASA/h for each group by substituting the CMS average time for each anesthesia procedure time for the actual time reported by each group and using 15-min time units. For each group, the Actual (Act) tASA/h and CMS tASA/h were calculated for both options-changing the interval for all time units or only for second and subsequent hours. Intervals were 15, 12, 10, 7, 6, or 5 min. When changing all time units, Act tASA/h and CMS tASA/h were never equal for all groups. The two productivity measures became approximately equal if only time units after the first hour were changed to 6- to 7-min intervals. When changes were applied only to the Act tASA/h (with CMS tASA/h remaining at 15-min intervals), at the 12-min interval either option resulted in a similar or higher Act tASA/h than CMS tASA/h. Both options increase the value of time and help compensate for the lost economic opportunity of longer-than-average surgical durations.

IMPLICATIONS

Longer-than-average surgical durations result in less potential revenue per hour under current billing methodology. This study quantifies the increase in billing productivity when the value of time is increased, when evaluating the billing productivity of four academic anesthesiology groups.

Comparing clinical productivity of anesthesiology groups

BACKGROUND

Intergroup comparisons of clinical productivity are important for strategic planning and evaluation of clinical and business operations. However, in a preliminary study, comparisons of two anesthesiology groups using "per full-time equivalent" measurements were confounded by different concurrencies or staffing ratios, whereas measurements based on "per operating room (OR) site," "per case," and "billed American Society of Anesthesiologists (ASA) units per hour of care" permitted meaningful comparisons despite differing concurrencies. The purpose of this study was to determine whether these measurements would allow for meaningful comparisons when applied to multiple groups.

METHODS

Annual totals of total ASA units (tASA), 15-min time units, and the number of cases billed, as well as the average number of daily anesthetizing sites (OR sites) staffed and the average number of anesthesiologists required to the staff sites, were collected from each group that participated. All anesthesia care billed with ASA units was included, except for obstetric care. Any clinical service not billed using ASA units was excluded. Productivity measurements (concurrency, tASA/OR site, hours billed per OR site per day, hours billed per case, tASA billed per hour of anesthesia care, and base units per case) were calculated. Median and range for all groups and for private-practice and academic groups were determined.

RESULTS

Eleven private-practice and nine academic groups from 12 states participated in the study. Productivity measurements that are influenced by duration of surgery (hours billed per case, tASA billed per hour of anesthesia care) differed significantly between groups, with private-practice groups having shorter duration than academic groups (median hours billed per case, 1.5 2.6, respectively). Although tASA/OR site measurements were similar in private-practice and academic groups, academic groups worked significantly longer hours billed per OR site per day (median, 6.0 h 7.8, respectively) to achieve the same level of tASA/OR site. Hourly billing productivity (tASA billed per hour of anesthesia care) correlated highly with surgical duration (hours billed per case).

CONCLUSION

This study demonstrates a method of comparing departmental clinical productivity between anesthesiology groups. Private-practice groups provided care for cases of shorter duration than academic groups. This difference was evident in several productivity measurements.

Postoperative nausea and vomiting after total intravenous anesthesia with propofol and remifentanil or alfentanil: how important is the opioid?

STUDY OBJECTIVE

To compare the frequency and duration of postoperative nausea and vomiting (PONV) following total intravenous anesthesia (TIVA) with propofol and either remifentanil or alfentanil in outpatients undergoing arthroscopic surgery of the extremities.

DESIGN

Randomized, third-party blinded study.

SETTING

University medical center.

PATIENTS

100 ASA physical status I and II patients scheduled for arthroscopic surgery of the knee or shoulder.

INTERVENTIONS

The anesthesia regimen consisted of a bolus followed by continuous infusion of propofol (2 mg/kg followed by 120 microg/kg/min) and the opioid (remifentanil 0.5 microg/kg followed by 0.1 microg/kg/min or alfentanil 10 microg/kg followed by 0.25 microg/kg/min). Patients breathed 100% oxygen spontaneously through a Laryngeal Mask Airway (or an endotracheal tube when medically indicated). Opioids were titrated to maintain blood pressure and heart rate within 20% of baseline and a respiratory rate of 10 to 16 breaths/min. Propofol was titrated downward as low as possible without permitting patient movement.

MEASUREMENTS

Nausea was determined by an 11-point categorical scale and was recorded before surgery and multiple time points thereafter. The times of emetic episodes were recorded. Treatment of PONV was at the discretion of the postanesthesia care unit (PACU) nurses who were blinded to the identity of the opioid used.

MAIN RESULTS

Nausea scores were 0 at all time points in over 70% of the patients in each group. None of the 100 patients vomited while in the hospital, and only one patient required antiemetic therapy.

CONCLUSION

When propofol-based TIVA is used for arthroscopic surgery, short-acting opioids do not significantly affect the risk of PONV.

The impact of longer-than-average anesthesia times on the billing of academic anesthesiology departments

Academic anesthesiology departments provide clinical services for surgical procedures that have longer-than-average surgical times and correspondingly increased anesthesia times. We examined the financial impact of these longer times in three ways: 1) the estimated loss in revenue if billing were done on a flat-fee system by using industry-averaged anesthesia times; 2) the estimation of incremental operating room (OR) sites necessitated by longer anesthesia times; and 3) the estimated potential gain in billed units if the hours of productivity of current anesthesia time were applied to surgical cases of average duration. Health Care Financing Administration average times per anesthesia procedure code were used as industry averages. Billing data were collected from four academic anesthesiology departments for 1 yr. Each claim billed with ASA units was included except for obstetric anesthesia care. All clinical sites that do not bill with ASA units were excluded. Base units were determined for each anesthesia procedure code. The mean commercial conversion factor (US$45 per ASA unit) for reimbursement was used to estimate the impact in dollar amounts. In all four groups, anesthesia times exceeded the Health Care Financing Administration average. The loss per group in billed ASA units if a flat-fee billing system were used ranged from 18,194 to 31,079 units per group, representing a 5% to 15% decrease (estimated billing decrease of US$818,719 to US$1,398,536 per group). The number of excess OR sites necessitated by longer surgical and anesthesia times ranged from 1.95 to 4.57 OR sites per group. The potential gain in billed units if the hours of productivity of current anesthesia time were applied to surgical cases of average duration was estimated to be from 13,273 to 21,368 ASA units. Longer-than-average anesthesia and surgical times result in extra hours or additional OR sites to be staffed and loss of potential reimbursement for the four academic anesthesiology departments. A flat-fee system would adversely affect academic anesthesiology departments.

IMPLICATIONS

We examined the economic impact of longer-than-average anesthesia times on four academic anesthesiology departments in three ways: the estimated loss in revenue under a flat-fee system, the excess operating room sites staffed, and the potential gain in revenue if the surgeries were of average length. These results should be considered both in productivity measurements and strategies for operating room management.

Effects of hemorrhagic hypotension on tyrosine concentrations in rat spinal cord and plasma

Tyrosine is the precursor for catecholamine neurotransmitters. When catecholamine-containing neurons are physiologically active (as sympathoadrenal cells are in hypotension), tyrosine administration increases catecholamine synthesis and release. Since hypotension can alter plasma amino acid composition, we examined the effects of an acute hypotensive insult on tyrosine concentrations in plasma and spinal cord. Rats were cannulated and bled until the systolic blood pressure was 50 mmHg, or were kept normotensive for 1 h. Tyrosine and other large neutral amino acids (LNAA) known to compete with tyrosine for brain uptake were assayed in plasma and spinal cord. The rate at which intra-arterial [3H]tyrosine disappeared from the plasma was also estimated in hemorrhaged and control rats. In plasma of hemorrhaged animals, both the tyrosine concentration and the tyrosine/LNAA ratio was elevated; moreover, the disappearance of [3H]tyrosine was slowed. Tyrosine concentrations also increased in spinal cords of hemorrhaged-hypotensive rats when compared to normotensive controls. Changes in plasma amino acid patterns may thus influence spinal cord concentrations of amino acid precursors for neurotransmitters during the stress of hemorrhagic shock.

[Propofol suppresses sympathetic activity and inhibits the baroreceptor reflex in waking rats]

The effects of propofol on sympathetic nerve activity and on the baroreceptor reflexes were examined in male Wistar rats. Sympathetic nerve activity was recorded directly from a renal nerve electrode placed earlier; baroreceptor reflex activity was estimated by changes in blood pressure (BP) and heart rate (HR) induced by the vasopressor phenylephrine, or the vasodilator, nitroprusside. Awake animals were anesthetized with propofol (10 mg/kg iv bolus, followed by approximately 35 mg/kg/hr by infusion) for 30 min. During the first 3 minutes, propofol increased sympathetic nerve activity by 113%, while mean arterial pressure was lowered to 85% of control. After 20 minutes, both sympathetic nerve activity and blood pressure had declined by 14% below baseline. Heart rate was stable at the level of approximately 110% throughout. Propofol also attenuated the sensitivity of chronotropic and sympathetic components of the baroreceptor reflex (i.e., to 23-43% and 25-34%, respectively). Thus, propofol lowers blood pressure by a central mechanism attenuating sympathetic nerve activity and sensitivity of baroreceptor reflex.

Exercise and neuromodulators: choline and acetylcholine in marathon runners

Certain neurotransmitters (i.e., acetylcholine, catecholamines, and serotonin) are formed from dietary constituents (i.e., choline, tyrosine and tryptophan). Changing the consumption of these precursors alters release of their respective neurotransmitter products. The neurotransmitter acetylcholine is released from the neuromuscular junction and from brain. It is formed from choline, a common constituent in fish, liver, and eggs. Choline is also incorporated into cell membranes; membranes may likewise serve as an alternative choline source for acetylcholine synthesis. In trained athletes, running a 26 km marathon reduced plasma choline by approximately 40%, from 14.1 to 8.4 uM. Changes of similar magnitude have been shown to reduce acetylcholine release from the neuromuscular junction in vivo. Thus, the reductions in plasma choline associated with strenuous exercise may reduce acetylcholine release, and could thereby affect endurance or performance.

Effects of running the Boston marathon on plasma concentrations of large neutral amino acids

Plasma large neutral amino acid concentrations were measured in thirty-seven subjects before and after completing the Boston Marathon. Concentrations of tyrosine, phenylalanine, and methionine increased, as did their "plasma ratios" (i.e., the ratio of each amino acid's concentration to the summed plasma concentrations of the other large neutral amino acids which compete with it for brain uptake). No changes were noted in the plasma concentrations of tryptophan, leucine, isoleucine, nor valine; however, the "plasma ratios" of acid patterns may influence neurotransmitter synthesis.

Endogenous adenosine and hemorrhagic shock: effects of caffeine administration or caffeine withdrawal

Plasma adenosine concentrations doubled when rats were subjected to 90 min of profound hemorrhagic shock. Administration of caffeine (20 mg per kg of body weight), an adenosine-receptor antagonist, attenuated the hemorrhage-induced decrease in blood pressure. In contrast, chronic caffeine consumption (0.1% in drinking water), followed by a brief period of caffeine withdrawal, amplified the hypotensive response to hemorrhage. These data suggest that endogenous adenosine participates in the hypotensive response to hemorrhage and that caffeine may protect against, and caffeine withdrawal may exacerbate, this response.

Spinal cord noradrenergic neurons are activated in hypotension

Although norepinephrine-containing nerve terminals in the spinal cord synapse in the vicinity of sympathetic preganglionic cells, their effect on sympathetic outflow has remained unclear. Since survival during hypotension necessitates sustaining maximal sympathetic activity, we used experimental hypotension as a physiological stimulus to determine whether such activity is associated with an increase or a decrease in spinal cord norepinephrine turnover. Male Sprague-Dawley rats (500 g) were anesthetized with chloralose and urethane and their left carotid arteries were cannulated for blood pressure measurements and blood removal. Control animals remained normotensive during the 1-h study period; hypotensive animals were bled to a 50 mm Hg systolic pressure. Catecholamine release, as indicated by methoxyhydroxyphenylethyleneglycol sulfate (MHPG-SO4) concentrations, was greater in spinal cords of hypotensive rats than in normotensive controls. Apparent catecholamine synthesis also increased: norepinephrine concentrations did not change even though those of MHPG-SO4 doubled and the accumulation of dihydroxyphenylalanine (in other animals pretreated with NSD 1015) also doubled. These studies show that catecholamine-containing neurons in the spinal cord are stimulated in hypotension, and suggest that they may function physiologically to increase sympathetic outflow and thus blood pressure.

Tyrosine accelerates catecholamine synthesis in hemorrhaged hypotensive rats

Tyrosine, the amino acid precursor of catecholamines, increases blood pressure (BP) in rats made hypotensive by hemorrhage. Since this amino acid also accelerates catecholamine synthesis in and release from frequently-firing neurons, we tested the hypothesis that tyrosine's pressor action resulted from this mechanism. Male Sprague-Dawley rats (500 g) were anesthetized with chloralose (50 mg/kg) and urethane (500 mg/kg) and tracheostomized. The carotid artery was cannulated allowing BP to be recorded continuously. Blood was removed until systolic BP fell to half of each animal's starting value; 45 min later, animals received tyrosine or other treatments in volumes of 1 ml/kg. Tyrosine (100 mg/kg) increased BP by 58%, while saline caused an insignificant increase. Pretreatment with carbidopa, which inhibits tyrosine's conversion to catecholamines, blocked the amino acid's effect. Tyrosine also failed to increase BP in rats made hypotensive with phentolamine, suggesting that it acts via catecholamine receptors. Adrenal epinephrine significantly (P less than 0.02) and splenic norepinephrine slightly (P less than 0.07) increased in rats receiving tyrosine after 1 h of hypotension when compared with tissue-catecholamine contents in similar rats. These observations show that tyrosine increases BP during hemorrhagic hypotension by accelerating catecholamine synthesis.

Tyrosine's pressor effect in hypotensive rats is not mediated by tyramine

Tyrosine, the amino acid precursor of catecholamines, increases blood pressure (BP) in hemorrhaged hypotensive rats. Since tyrosine may also be decarboxylated to form tyramine, which releases norepinephrine from sympathetic terminals, we tested the hypothesis that tyramine formation might mediate tyrosine's ability to increase BP. Three lines of evidence indicate that tyrosine does not act via this mechanism: pretreatment with reserpine blocked tyramine's but not tyrosine's pressor activity; pretreatment with hexamethonium left tyramine's effect intact but blocked the pressor response to tyrosine; and plasma tyramine did not increase after an hemodynamically-active dose of tyrosine (100 mg/kg).

Chronic caffeine consumption potentiates the hypotensive action of circulating adenosine

Mean arterial blood pressure was correlated with arterial plasma adenosine levels during intravenous adenosine infusion in unanesthetized, unrestrained rats. Elevation of plasma adenosine to 5 to 6 microM (normal range 1.6 to 4.6 microM) depressed mean arterial pressure by 20 to 30 percent: this was blocked by a single caffeine injection (15 mg/kg). In contrast, caffeine consumption for 3 weeks, followed by a 1-day washout, markedly potentiated responses to adenosine, plasma levels in the 2 to 4 microM range causing 30 to 40 percent reductions in mean arterial pressure. These observations suggest that chronic occupancy of cardiovascular adenosine receptors by caffeine can enhance tissue responsiveness to adenosine, and that endogenous adenosine might act as a circulating hormone.

Tyrosine's vasoactive effect in the dog shock model depends on the animal's starting blood pressure

We examined the effect of tyrosine (10-200 mg/kg given intravenously) or placebo on blood pressure (BP) in dogs made hypotensive (systolic BP = 50 mm Hg) by bleeding one hour previously. Animals which, prior to induction of hypotension, had been normotensive (mean arterial pressures, [MAP] less than or equal to 145 mm Hg) subsequently exhibited a dose-related increase in BP after tyrosine administration. In contrast, dogs which had been hypertensive prior to bleeding exhibited a fall in BP after tyrosine. These observations indicated that prior cardiovascular status may be an important factor influencing responses to exogenous tyrosine, and to endogenous catecholamines produced from the tyrosine.

Neurotransmitter precursors and brain function

Brain function can be affected by the availability of dietary precursors of neurotransmitters. This occurs because the rate-limiting synthetic enzymes are not "saturated" with substrate under normal circumstances. Tyrosine affects catecholaminergic neurons that fire rapidly, whether in the brain stem to decrease blood pressure in hypertension or in the adrenal gland to increase blood pressure in hypotension, and has been used in the treatment of Parkinson's disease and depression. Choline forms acetylcholine and has been used successfully in the treatment of tardive dyskinesia and memory disorders. Tryptophan, which forms serotonin, has been used for chronic pain therapy, sleep disorders, depression, and appetite control. Although these substances may lack the potency of traditionally used agonists, they offer an increase in specificity because the enzymes necessary to convert them to neurotransmitters are found only in neurons. Precursors are also "physiological"; they are consumed as foods and, therefore, should be relatively safe therapeutic agents.

Tyrosine increases blood pressure in hypotensive rats

Administration of tyrosine, the amino acid precursor of catecholamines, increased blood pressure 38 to 49 percent in rats made acutely hypotensive by hemorrhage; other large neutral amino acids were ineffective. Tyrosine's effect was abolished by adrenalectomy, suggesting that, in hypotensive animals, it acts by accelerating the peripheral synthesis and release of catecholamines.

Phenformin and hyperamylasemia in lactic acidosis

All cases of lactic acidosis occurring during a 23-month period in a metropolitan teaching hospital were reviewed to ascertain the frequency of hyperamylasemia. Serum amylase activity had been measured in 12 of 26 patients and was elevated in eight (67%). Hyperamylasemia was not significantly more frequent in patients with phenformin-associated lactic acidosis than in patients with lactic acidosis who had not received phenformin. Serum amylase activity did not correlate with the severity of acidosis (arterial pH) or with renal function (serum creatinine).

Serum phenformin concentrations in patients with phenformin-associated lactic acidosis

Phenformin concentrations were measured in serum from seven patients with phenformin-associated lactic acidosis, and initial values ranging from 20 to 625 ng./ml. were obtained. Five of the seven patients had serum concentrations within the usual therapeutic range of up to 241 ng./ml. Serum phenformin concentrations were measured serially, and apparent half-lives of 5, 25, and 30 hours were obtained in three patients with serum creatinine concentrations of 1.7, 7.6, and 6.0 mg./dl., respectively. Although the half-life of phenformin was prolonged in azotemic patients, no correlation between serum creatinine concentration and serum phenformin could be demonstrated; furthermore, the severity of lactic acidosis as measured by arterial pH and lactate concentration did not correlate with the serum creatinine concentration.

Phenformin and lactic acidosis

All patients admitted with severe lactic acidosis to a university teaching hospital during a 17-month period were taking phenformin hydrochloride. Serum phenformin concentration was measured in one patient and found to be four to nine times the usual therapeutic concentration. Prerenal azotemia was present at the time of admission in all but one of these patients, but renal function was normal at the time of discharge in those patients with phenformin-associated lactic acidosis who survived. Phenformin-associated lactic acidosis accounted for 7% of the episodes of metabolic acidosis and 27% of deaths due to metabolic acidosis in diabetics.