Douglas R. Bacon

Blood product use in cardiac revascularization: comparison of on- and off-pump techniques.

BACKGROUND Cardiac revascularization on a beating heart avoids the side effects of cardiopulmonary bypass (eg, neurologic injury, hemodilution, and coagulopathy). We examined perioperative bleeding and use of blood products during coronary artery bypass grafting using either on-pump or off-pump techniques. METHOD The charts of 126 patients who had coronary artery bypass grafting were reviewed. Data from 66 patients revascularized off pump and 60 patients with cardiopulmonary bypass (on pump) were analyzed using unpaired Students t test. RESULTS Average age was 62.5 years in either group. More patients received heparin preoperatively in the off-pump group that resulted in mild elevation of preoperative partial thromboplastin time and activated clotting time (40.4 +/- 2.9 seconds and 150.1 +/- 5.3 seconds, respectively). However, the off-pump group had less perioperative (intraoperative or postoperative) bleeding (2312 +/- 212 mL versus 3251 +/- 155 mL, p < 0.05) and required fewer blood products compared with the on-pump group. Hemoglobin and platelets decreased more in the conventional on-pump group. CONCLUSIONS Avoiding cardiopulmonary bypass decreases perioperative bleeding and, consequently, reduces the use of blood products after coronary artery bypass grafting, which might result in fewer transfusion-related complications.

Finite amplitude distortion of the pulsed fields used in diagnostic ultrasound

A simple theoretical model of the non-linear propagation of pulsed focused acoustic beams is described. It enables the distortion of the peak cycle of the pulse to be calculated from a few experimentally measured parameters. The model is discussed, and justified for application to the fields from medical ultrasonic diagnostic equipment. It is particularly relevant for specifying the degree of distortion present, as might be required by future written standards for diagnostic equipment performance. Preliminary experimental verification of the model is reported.

Pressure waveforms generated by a Dornier extra-corporeal shock-wave lithotripter.

Pressure waveforms in the acoustic field generated by a Dornier (HM3) shock-wave lithotripter have been measured using a bilaminar shielded PVDF membrane hydrophone in water. Using these waveforms, values of the peak-positive (p+) and peak-negative pressure (p-) at various positions in the field have been estimated. At the focus, p+ is 38.6 MPa (standard deviation = 9.0 MPa) and p- is 10.1 MPa (standard deviation = 1.0 MPa) at 20 kV discharge potential and an electrode separation in the range 1.3 to 2.4 mm. The peak-positive pressure is found to fall to 50% (-6 dB level) at about 60 mm either side of the focus on the major axis of the reflector and on a 10 mm radius circle around the focus in the focal plane. A shot-to-shot variation of +/- 25% in p+ is attributed to the inherent variability of the electrical discharge which may result in changes in the exact position and strength of the acoustic field. The results reported are considered to be more accurate than those of previous measurements due to the relatively flat frequency response of this type of hydrophone.

Succinylcholine and the open globe. Tracing the teaching.

A CURRENT anesthesia text states that “. . .management of emergency anesthesia for a patient having a full stomach and an open eye injury requires balancing the need to prevent aspiration of gastric contents against prevention of sudden significant increases in IOP [intraocular pressure] that may cause further eye damage and loss of vision.” Referring to a standard technique for the rapid induction of anesthesia (precurarization, thiopental, and succinylcholine), the text also states that “. . .although IOP may increase with this method, no published reports have described further eye damage after rapid sequence induction of anesthesia with d-tubocurarine, thiopental, and succinylcholine.” Nonetheless, it is a common belief among practitioners that the use of succinylcholine for induction in patients with open globe injuries is relatively or absolutely contraindicated. This belief is based on the known effects of succinylcholine on IOP and the perception that well-documented cases of the extrusion of ocular contents have been reported. Nondepolarizing neuromuscular blocking drugs that duplicate the rapid onset and offset of succinylcholine are not yet available, and this remains a question of clinical relevance for many anesthesiologists. The relative rarity of catastrophic complications such as extrusion of vitreous contents makes it difficult to apply research tools such as randomized clinical trials to guide practice. In this article, we explore the origins of the teaching that succinylcholine is contraindicated in patients with open eye injuries. It is not our purpose to provide a review of anesthetic effects on IOP but rather to present the history of how this knowledge has been combined with outcome reports to develop clinical recommendations. We believe that this is an instructive example of how clinical recommendations regarding the prevention of low-frequency events in the practice of anesthesiology can arise and evolve.

Archie Brain: celebrating 30 years of development in laryngeal mask airways

The practice of anaesthesia was revolutionised by the ideas of Archie Brain. The routine use of a facemask to manage the airway was not a hands‐free technique, despite the development of various harnesses, and made adequate record‐keeping difficult. The tracheal tube was associated with some morbidity, which some felt was unsuitable for day surgery. Brain developed an airway management device that was less stressful to the patient than tracheal intubation, and was, however, as safe as using a facemask and airway. Brain also hoped his device would function for cases where mask ventilation was particularly difficult and thus give anaesthetists a safer alternative to a complex intubation, especially in emergency scenarios.

Interpleural analgesia for the treatment of severe cancer pain in terminally ill patients

Interpleural analgesia was used to alleviate acute, severe exacerbations of chronic pain unrelieved by pharmacologic therapy in ten terminally ill cancer patients. Pain from metastatic disease to the neck, arms, chest, brachial plexus, thorax, or abdomen was effectively eliminated between 7 hr and 40 days in nine patients, who died with minimal or no pain. The technique was performed primarily using bupivacaine. No side effects were detected. Interpleural analgesia appears to be effective in rapidly controlling acute exacerbations of cancer pain in terminally ill patients. Moreover, it may also be a suitable therapy for moribund patients when used as a continuous-infusion technique.

To define a specialty: A brief history of the American Board of Anesthesiology's first written examination

The initial written examination of the American Board of Anesthesiology, a division of the American Board of Surgery, was given on March 28, 1939. For all anesthesiologists, this date has double significance. First, what was meant by anesthesiology as a medical specialty was defined through the questions posed on the first examination. Second, the physicians being tested that day were among the first physician-anesthetists to exploit the newly created path to recognition as specialists in the science and art of anesthesia by the American medical hierarchy. Gaining the support of organized medicine was an involved and arduous struggle that consumed most of the 1930s. A triumvirate of visionaries, Paul Wood, John Lundy, and Ralph Waters, was necessary to crystalize the goal of specialty recognition of physician-anesthetists. The first written examination was the consummation of this dream of equal status for anesthesia. The examination would not become repetitious, and within the first decade of testing, the style would change from an essay format to multiple-choice questions similar to the current form.

A historical perspective on use of the laryngoscope as a tool in anesthesiology

EACH year, one of the first skills anesthesia residents must master is direct visualization of the vocal cords to safely and successfully intubate the trachea of surgical patients. Debates have raged in teaching centers about the superiority of one laryngoscope over another or the merits of a straight versus a curved blade. However, this yearly debate is a phenomenon of the twentieth century, as anesthesiologists sought better tools to facilitate patient care. Physician interest in visualizing the vocal cords can be traced to at least the mid-1700s. However, controversy remains as to who deserves historical credit for the development of the laryngoscope. An appreciation of the contributions of several innovative scientists involved with the development of the laryngoscope over more than 250 yr may be of greater importance. Although the laryngoscope was initially a tool developed solely for the otolaryngologist, advances in anesthesia during the early 20th century made the addition of the laryngoscope and development of the skills to use it successfully essential to the anesthesiologist. The introduction of the laryngoscope into the practice of clinical anesthesia is best described by considering these advances in the “surgeon” and “anesthesiologist” periods.

An unexplained death: Hannah Greener and chloroform.

HANNAH Greener of Winlaton, near Newcastle in the United Kingdom, died more than 150 yr ago, on January 28, 1848, after receiving a chloroform anesthetic for the removal of a toenail. She was a healthy 15-yr-old girl who had successfully undergone an anesthetic with diethyl ether several months before for the removal of another toenail. Hers was the first death (fig. 1) attributed to the new and wondrous blessing of anesthesia for surgical pain relief. Various authors have ascribed her death to an anesthetic overdose, aspiration of the water and brandy used in attempts to resuscitate her, or some combination of secondary complications that will never be determined. During the past century and a half, understanding of the etiology of perioperative deaths has increased remarkably. What can be learned from another analysis of the facts surrounding the death of Hannah Greener? Is pulmonary aspiration as the proximal cause of her death a realistic possibility? Did she receive an overdose of chloroform as many of the contemporary physicians argued, or using our 21st-century knowledge, is there a better explanation of her untimely death?

Gaston Labat, John Lundy, Emery Rovenstine, and the Mayo Clinic: the spread of regional anesthesia in America between the world wars

The spread of regional anesthesia in America was greatly facilitated by the work of Gaston Labat. Recruited to work at the Mayo Clinic, Dr. Labat there published his seminal textbook, Regional Anesthesia, in which he laid out his techniques to the next generation of physician specialists, notably John Lundy, Ralph Waters, and Emery Rovenstine. It was Rovenstine who was responsible for creating the specialty of anesthesiology in the 1920s and 1930s. John Lundy continued Labats work at the Mayo Clinic when Labat left for Bellevue Hospital in New York. There, while teaching, Labat further developed and refined his techniques for delivering regional anesthesia.