Murali Sivarajan

Three-dimensional echocardiographic assessment of annular shape changes in the normal and regurgitant mitral valve

OBJECTIVES To compare mitral annular shape and motion throughout the cardiac cycle in patients with normal hearts versus those with functional mitral regurgitation (FMR). BACKGROUND The causes of mitral regurgitation without valvular disease are unclear, but the condition is associated with changes in annular shape and dynamics. Three-dimensional (3D) imaging provides a more comprehensive view of annular structure and allows accurate reconstructions at high spatial and temporal resolution. METHODS Nine normal subjects and 8 patients with FMR undergoing surgery underwent rotationally scanned transesophageal echocardiography. At every video frame of 1 sinus beat, the mitral annulus was manually traced and reconstructed in 3D by Fourier series. Annular projected area, nonplanarity, eccentricity, perimeter length, and interpeak and intervalley spans were determined at 10 time points in systole and 10 points in diastole. RESULTS The mitral annulus in patients with FMR had a larger area, perimeter, and interpeak span than in normal subjects (P <.001 for all). At mid-systole in normal annuli, area and perimeter reach a minimum, nonplanarity is greatest, and projected shape is least circular. These cyclic variations were not significant in patients with FMR. Annular area change closely paralleled perimeter change in all patients (mean r = 0.96 +/- 0.07). CONCLUSIONS FMR is associated with annular dilation and reduced cyclic variation in annular shape and area. Normal mitral valve function may depend on normal annular 3D shape and dimensions as well as annular plasticity. These observations may have implications for design and selection of mitral annular prostheses.

Gastroesophageal Perforation after Intraoperative Transesophageal Echocardiography

THE use of transesophageal echocardiography for intraoperative monitoring of cardiac function is increasing. Complications are rare. Oropharyngeal injury and hypopharyngeal perforation during difficult insertion of the echoprobe in anesthetized patients have been reported. 1,2 One case of perforation of the cervical esophagus in an awake patient after multiple attempts at insertion of the echoprobe has been reported.3 Esophageal perforation from an echoprobe in an anesthetized patient, however, has not been published. We observed and report a case of perforation of the gastroesophageal junction in an anesthetized patient after an easy insertion of the echoprobe that yielded good quality transesophageal echocardiograms.

The Position and the State of the Larynx during General Anesthesia and Muscle Paralysis

Based on a chance observation in two patients in whom the larynges could be visualized during direct laryngoscopy using topical anesthesia but not after general anesthesia and muscle paralysis, the authors postulated that there will be a shift in the position of the larynx with the onset of general anesthesia and muscle paralysis. To verify this the authors measured the position of larynx in lateral radiographs of necks taken in human volunteers when they were awake, and after induction of general anesthesia and muscle paralysis. The authors found that the hyoid bone and epiglottis were shifted anteriorly and the supraglottic region or the vestibule of the larynx was enlarged with the onset of general anesthesia and muscle paralysis. In addition, the larynx was also stretched longitudinally with wide separation of the vestibular and vocal folds. The authors conclude that consciousness is associated with tonic muscular activity that folds the larynx and partially closes it and that onset of general anesthesia and muscle paralysis opens the larynx wider and shifts it anteriorly, which might make visualization of the larynx during direct laryngoscopy difficult in some patients.

Systemic and Regional Blood Flow during Epidural Anesthesia without Epinephrine in the Rhesus Monkey

The radioactive-microsphere technique was used to determine distribution of cardiac output and regional blood flow in rhesus monkeys before and 10, 20, 40, and 80 minutes after induction of epidural anesthesia with lidocaine (1 per cent) without epinephrine. Four monkeys were studied during low epidural anesthesia (sensory level T10) and five other monkeys were studied during high epidural anesthesia (sensory level T1). During T10 epidural anesthesia. During T1 epidural anesthesia, blood flow (per 100 g tissue) to the lower extremity was significantly increased 10 minutes after induction of anesthesia. There was no other significant change in regional blood flow during T10 epidural anesthesia. During T1 epidural anesthesia, blood flow to the heart was significantly reduced at 10 minutes, blood flow to the liver was significantly reduced at 10 and 40 minutes, blood flows to kidneys and miscellaneous organs (lymph nodes, salivary glands, etc.) were significantly reduced at 10, 20, and 40 minutes, and blood flow to the brain was significantly reduced throughout anesthesia. Vascular resistance in the lower extremity was reduced in each monkey following epidural anesthesia, indicating arteriolar dilatation. Also, during both levels of anesthesia, the lungs received an increased proportion of the microspheres, suggesting an increased periopheral arteriovenous shunting of microspheres due to the arteriolar dilatation.

Effects of general anesthesia and paralysis on upper airway changes due to head position in humans

Background In supine patients with their heads in flexion, general anesthesia causes posterior displacement of upper airway structures that is associated with airway obstruction, and extension of the head helps restore patency. However, the independent effects of head position, general anesthesia, and muscle paralysis on upper airway structures are not known. Methods Lateral radiographs of the neck were taken in supine patients with the head in flexion and extension, during consciousness, and after induction of general anesthesia and muscle paralysis. The following measurements were made: distances from the horizontal plane to the epiglottis, the hyoid, and the thyroid cartilage to detect anteroposterior displacements; distances from the transverse plane to the hyoid and the thyroid cartilage to detect cephalocaudad displacements; and widths of the oropharynx, the laryngeal vestibule, and the laryngeal sinus. Results With the head in flexion, anesthesia and paralysis compared with the conscious state caused posterior displacement of the epiglottis, narrowing of the oropharynx, and widening of the laryngeal vestibule. With the head in extension, anesthesia and paralysis compared with the conscious state caused anterior displacements of the epiglottis, the hyoid, and the thyroid cartilage, narrowing of the oropharynx, and widening of the laryngeal vestibule and the laryngeal sinus. Conclusion Loss of tonic muscular activity due to anesthesia and paralysis results in anteroposterior displacements of the upper airway structures with flexion and extension of the head that are in the same direction as that of the mandible. Anesthesia and paralysis also widen the dimensions of the larynx. These changes might have implications for instrumentation and protection of the airway during general anesthesia or unconsciousness.

Regional blood flow in dogs during halothane anesthesia and controlled hypotension produced by nitroprusside or nitroglycerin

We used the radioactive microsphere method to measure and compare the effects of sodium nitroprusside (SNP) and nitroglycerin (NTG) on organ blood flow during hypotension induced by each drug. The study was done in 10 dogs anesthetized using 0.7% end-tidal halothane. Each animal received both SNP and NTG to decrease the mean arterial blood pressure (MABP) to 45 mm Hg, but the sequence in which the drugs were administered was alternated. Five of the dogs received SNP first and five received NTG first. Organ blood flow was measured after a stable period of hypotension that was brief by necessity in order to avoid cyanide toxicity due to increasing dose requirements for SNP. Measurements were made before and during hypotension induced with each drug. The mean duration of stable hypotension was shorter (P < 0.05) with NTG (5 ± 1 min) (mean ± sem) than with SNP (7 ± 1 min). During NTG-induced hypotension, blood flows to the brain, kidneys, liver, gastrointestinal tract, pancreas, and skeletal muscle were maintained at control levels. During SNP-induced hypotension, blood flows to the myocardium, liver, gastrointestinal tract, pancreas, and skeletal muscle were maintained at control levels. NTG increased myocardial blood flow (P < 0.05), while SNP decreased blood flow to brain (P < 0.05) and kidneys (P < 0.01). Both drugs decreased blood flow to the spleen (P < 0.001). Our results indicate that during the first few minutes of NTG-induced hypotension, blood flows to all organs except the spleen are well-maintained, while the first few minutes of SNP-induced hypotension are associated with decreases in blood flow to brain and kidney as well as to the spleen

Perioperative Acute Renal Failure Associated with Preoperative Intake of Ibuprofen

NONSTEROIDAL antiinflammatory drugs (NSAIDs) inhibit prostaglandin synthesis. Because renal blood flow depends on prostaglandin, particularly when circulating blood volume is decreased, a recommendation has been made that NSAIDs be withheld before surgery because of the risk of renal dysfunction. 1 However, there has been no report of perioperative renal dysfunction attributable to preoperative administration of NSAIDs, and a recent review has endorsed preoperative administration of NSAIDs for minor outpatient procedures and a combined multimodality drug therapy including NSAIDs after surgery. 2 The authors report a case of perioperative acute renal failure after lumbar discectomy in a young patient who was taking ibuprofen preoperatively.

Costs and wastes in anesthesia care

Purpose of review The current economic climate has put pressure on healthcare systems and providers, including anesthesiologists, to minimize costs without sacrificing patient safety. In this review, we discuss costs associated with anesthesia care, including medications and intraoperative monitoring, and suggest ways to reduce wastes and overall expenditure. Recent findings Significant amount, perhaps 20–50%, of drugs drawn up are never used but discarded as whole ampoules or vials. There has been a progressive shift to using more expensive inhalational agents and total intravenous anesthesia in the last 10 years. Highest drug costs are associated with total intravenous anesthesia protocols, which are five to 10 times more expensive than administering sevoflurane or desflurane with premedication using antiemetics. Among the inhalational agents, usage costs of sevoflurane and desflurane are 10 and 25 times, respectively, that of isoflurane. Bispectral index monitoring, which requires use of an expensive proprietary electrode is no better, perhaps even less effective, than titration of inhalational agents using end tidal anesthetic concentration to monitor depth of anesthesia and prevent intraoperative awareness. Summary Anesthesia medications comprise a significant proportion of hospital pharmacy budgets. Average anesthesia-related cost reductions of US

Halothane, But Not Isoflurane, Impairs the β-adrenergic Responsiveness in Rat Myocardium

13–30 per cases multiplied by 25 million anesthetics administered annually in the USA has the potential to yield savings of US

Jet ventilation using fiberoptic bronchoscopes

350–750 million. Bispectral index monitoring during inhalational anesthesia adds to the cost without providing any benefit.