394 CAROL L. LAKE

marizes current knowledge about von Willebrand disease which results from either reduced plasma levels of von Willebrand factor or abnormal structure of vWF. The several subtypes of this disease are described including their distinc- tive features and indicated therapy. Bleeding results from absence of the larger multimeric forms of vWF, probably from reduced synthesis or enhanced degradation of the abnormal protein.

Dureuil B, Viires N, Parienta R, et al: Effects of phrenic nerve cooling on diaphragmatic function. J Appl Physiol63:1763-1769, 1987

Application of iced slush transpericardially to a l-cm segment of canine phrenic nerve for either 5 or 30 minutes decreased the electrical activity of the diaphragm and trans- diaphragmatic pressure (diaphragmatic strength) within 100 seconds of application. Transdiaphragmatic pressure was measured during phrenic nerve stimulation at frequencies of 0.5, 30, and 100 Hz achieved with either intramuscular electrodes or electrodes placed around the phrenic nerve above its pericardial course. Recovery of function (nerve conduction) was rapid with short-term cooling (two minutes), but continued depression of electrical activity and trans- diaphragmatic pressure could be demonstrated four hours after cooling. Although clinical studies are necessary to determine the magnitude of effect in humans, these data suggest that significant diaphragmatic dysfunction may result from myocardial preservation with iced slush.

Stow PJ, Burrows FA: Anticoagulants in Anaesthesia. Can J Anaesth 34:632-649,1987

This excellent review includes not only the historical aspects of the commonly used anticoagulants heparin and warfarin, but also a detailed discussion of their pharmacolo- gy, including methods for antagonism. Controversial aspects of the indications for anticoagulation such as prevention of deep venous thrombosis and pulmonary embolism prophy- laxis are described. Protocols for the administration of antico- agulants in various situations, including cardiopulmonary bypass, and by different routes are listed. After thorough review of the available studies on the use of regional anes- thesia in anticoagulated patients, the authors conclude that considerable risk exists to the performance of either epidural or spinal analgesia. Finally, the management of the anticoag- ulated patient during general anesthesia and cardiopulmo- nary bypass is reviewed. The inadequacies of different proto- cols for anticoagulation during bypass is acknowledged. Both the cardiac anesthesiologist and the general anesthesia prac- titioner will find this a useful and informative review.

Brown MA, Norris RM, Takayama M, et al: Post-systolic shortening: A marker of poten- tial for early recovery of acutely ischaemic myo- cardium in the dog. Cardiovasc Res 21:703-716, 1987

Post-systolic shortening is the magnitude of wall seg- ment shortening occurring after end-systole. Wall thickening can occur in the postsystolic period as well. In experimental animals using ultrasonic crystals to determine wall motion in ischemic and nonischemic areas and radioactive micro-

spheres to measure regional blood flow, a significant correla- tion was found between postsystolic shortening and thicken- ing before and after coronary occlusion. Impairment and abbreviation of systolic shortening was noted within ten seconds of occlusion. Postsystolic shortening occurred con- currently with impaired systolic shortening. Postsystolic shortening was maximal within 5 to 15 minutes after occlu- sion and reached 42% of the magnitude of systolic shortening seen before occlusion. Recovery of systolic shortening on reperfusion also correlated significantly with the magnitude of postsystolic shortening.

Possible mechanisms for these findings, which could serve as markers for potential recovery of function in isch- emia, include active contraction of ischemic myocardium, elastic recoil of dyskinetic segments, or an interaction between normal and ischemic zones. Of these, the latter two are unsupported by experimental data. Increased lengthening velocity could not be demonstrated in the normal zone adjacent to the ischemic segment and postsystolic shortening occurred equally in hypokinetic peripheral segments as in dyskinetic central segments. However, there was a positive correlation between myocardial blood flow and postsystolic thickening, indicating that postsystolic shortening occurred to the greatest extent in segments likely to have the best functional recovery.

Gore JM, Goldberg RJ, Spodick DH, et al: A community-wide assessment of the use of pul- monary artery catheters in patients with acute myocardial infarction. Chest 923721-731,1987

This paper and its accompanying editorial by E. D. Robin suggest that pulmonary artery catheters should not be used in patients with acute myocardial infarction because of increases in mortality rate, length of hospital stay, and catheter-related complications. Case fatality rates were 44.8% with and 25.3% without pulmonary artery catheteriza- tion in patients with congestive heart failure. However, mortality was 74.4% with and 79.1% without catheterization for patients in cardiogenic shock. Other differences noted included increased use of catheters over time in teaching Y nonteaching hospitals, and in larger infarctions (higher peak creatine kinase, Q wave).

However, the results were generated by retrospective chart reviews from 3,263 nonrandomized patients in 1975, 1978, 198 1, and 1984 in Worcester, MA. Since clinical indications were used, there may have been subtle factors that led to insertion of a catheter in a given patient that could not be ascertained from chart review of the criteria defined for cardiogenic shock or congestive failure. Clearly, a pro- spective randomized clinical trial is needed to assess the true efficacy of pulmonary artery catheterization in patients with acute myocardial infarction.

Aronson S, Neff WA, Slogoff S, et al: Venous admixture of radial artery blood samples during cardiopulmonary bypass. Chest 92:836- 838,1987

Another cause of inaccuracy of radial arterial PO, was demonstrated when venous pressure in the same extrem- ity was equal to arterial pressure during cardiopulmonary