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Biomedical subjects

Mark A Gerhardt

Publications and source records attributed to Mark A Gerhardt.

7 recordsLinked to original sources
PubMed2006

Uvular edema secondary to snoring under deep sedation.

A 57-year-old male with a documented history of obstructive sleep apnea with loud snoring received deep intravenous sedation with midazolam, fentanyl, ketamine, and propofol infusion and a left interscalene brachial plexus nerve block for a left biceps tendon repair. Loud snoring during the case was noted. On the second postoperative day, he was observed to have significant uvular edema. After due consideration of the various elements in the differential diagnosis, it was concluded that negative pressure trauma from deep snoring during the sedation was the most likely etiology.

Anesthetics, Dissociative↗
PubMed2005

Partial support with a centrifugal left ventricular assist device reduces myocardial oxygen consumption in chronic, ischemic heart failure.

BACKGROUND: Left ventricular assist devices (LVAD) are increasingly used for heart failure (CHF); however, the level of optimal support has not been elucidated. We hypothesize that partial LVAD support in an ovine model of microinfarction-induced CHF significantly reduces left ventricular myocardial oxygen consumption (LVVO2). METHODS AND RESULTS: Microembolization of the circumflex coronary artery was used to induce CHF in 5 sheep (ejection fraction 28 +/- 2%). Four months later, animals underwent implantation of a centrifugal LVAD. LVAD flow was incrementally increased from 0% (baseline) to 25%, 50%, and 75% support of the LV. LVVO2 and stroke work (SW) were calculated at each increment. At baseline, LVVO2 (microL/100 g LV/beat) measured 43.2 +/- 3.4. LVVO2 decreased to 26.5 +/- 8.2,* 20.3 +/- 8.9,* and 12.6 +/- 6.3* at 25%, 50%, and 75% support (*P < .05). SW (mm Hg/mL) measured 1933.0 +/- 275.7 at baseline and decreased to 1588.0 +/- 204.1, 1181.0 +/- 157.2,* and 764.5 +/- 171.7* at 25%, 50%, and 75% support. Cardiac output, heart rate, and left main coronary artery blood flow were unaffected with partial support. CONCLUSION: Complete support with a centrifugal LVAD is not necessary for achieving significant reductions in LVVO2 . Partial support of as little as 25% significantly reduces LVVO2 in CHF through comparatively minor reductions in cardiac work. This is the first study to examine partial LVAD support in a CHF model.

Animals↗
PubMed2004

Selective microembolization of the circumflex coronary artery in an ovine model: Dilated, ischemic cardiomyopathy and left ventricular dysfunction.

BACKGROUND: Ventricular remodeling often occurs after myocardial infarction, yet the natural history remains unpredictable because of the chronicity of the process and therapeutic interventions involved. We induced cardiac dysfunction in an ovine model via selective microembolization of the circumflex coronary artery (LCx) to test the hypothesis that ventricular remodeling progresses following coronary microembolization for up to 24 months. Methods and results Sheep underwent weekly selective microembolization of the LCx until left ventricular ejection fraction stabilized <35% for 2 consecutive weeks. In a subgroup carried out to 4 months, the end-systolic pressure-volume relationship slope decreased from 2.3+/-0.6 (baseline) to 1.3+/-0.5 at month 4 (P<.05). In a second group, echocardiography at 24 months, the ejection fraction decreased from 51+/-3% (baseline) to 25+/-2% (month 5) (P<.05) and stabilized through month 24 (23+/-5%, P<.05), whereas left ventricular end-systolic area and left ventricular end-diastolic area increased by 222% and 98%, respectively, through month 24. CONCLUSIONS: Selective microembolization of the LCx induces left ventricular dysfunction followed by dilated, ischemic cardiomyopathy, which continues to progress for up to 2 years despite stabilization of left ventricular ejection fraction. This model of ventricular remodeling secondary to microinfarction may be a useful experimental platform for large animal heart failure investigations.

Animals↗
PubMed2002

Anesthesia for foot and ankle surgery.

Regional anesthesia (RA) is the anesthetic of choice for all foot and ankle surgery. Advances in anesthetic equipment and techniques have made peripheral nerve blocks the perfect anesthetic technique for these patients, who should be educated about them in their surgeon's office. The anesthetic alternative of choice is, in the authors' opinion, a neuraxial (i.e. spinal or subarachnoid) technique, rather than a general anesthesia (GA). GA has a higher morbidity and complication rate compared to RA. Performance of a peripheral nerve block, or PNB, requires proper training, equipment, and support personnel in order to handle any and all complications, including general anesthesia.

Anesthesia↗
PubMed2002

Neuroprotection is associated with beta-adrenergic receptor antagonists during cardiac surgery: evidence from 2,575 patients.

OBJECTIVE: To determine the impact of perioperative beta-adrenergic receptor (betaAR) antagonist administration on neurologic complications. DESIGN: Observational database analysis. SETTING: A clinical investigation at a single tertiary academic medical center. PARTICIPANTS: Elective coronary artery bypass graft surgical patients operated on in the period 1994-1996. INTERVENTIONS: Patients were divided into 2 groups: (1) patients given betaAR antagonist-blocking drugs in the perioperative period, including during operation, and (2) patients not given betaAR antagonists. MEASUREMENTS AND MAIN RESULTS: betaAR antagonist use in 2,575 consecutive patients undergoing coronary artery bypass graft surgery (1994-1996) was determined using the Cardiovascular Database and Anesthesia Information System Database. Outcome variables were postoperative stroke, coma, and transient ischemic attack. Of patients, 113 (4.4%) had postoperative neurologic complications, including stroke (n = 44), coma (n = 12), and transient ischemic attack (n = 3). Of patients, 2,296 (89%) received perioperative betaAR antagonist therapy, and 279 (11%) did not. Adverse neurologic events occurred in 3.9% (n = 90) of patients who received perioperative betaAR antagonists and 8.2% (n = 23) of patients who did not receive betaAR antagonists (odds ratio, 0.45; 95% confidence interval, 0.28 to 0.73; p = 0.003, unadjusted.) Severe neurologic outcomes (stroke and coma) occurred in 1.9% (n = 44) of patients who received betaAR antagonists and 4.3% (n = 12) of patients who did not receive betaAR antagonists (odds ratio, 0.43; 95% confidence interval, 0.23 to 0.83; p = 0.016). CONCLUSION: Use of beta-adrenergic antagonists was associated with a substantial reduction in the incidence of postoperative neurologic complications. A prospective randomized trial is needed to verify this potentially important neuroprotective strategy in cardiac surgery.

Adrenergic beta-Antagonists↗