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Background The benefits of hypothermia for preventing ischemic injury are well known, but its application in surgery to protect the whole body during procedures requiring circulatory arrest is currently limited to Methods and Results With the use of extracorporeal cardiac bypass, 14 adult dogs were exsanguinated during cooling; 11 dogs were blood substituted using in combination the “purge” and “maintenance” solutions (group 1), and 3 dogs were perfused throughout with the “purge” solution alone as controls (group 2). After cardiac arrest, the solutions were continuously circulated for 3 \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\frac{1}{2}\) \end{document} hours by the extracorporeal pump (flow rate, 40 to 85 mL · kg −1 · min −1 ; mean arterial blood pressure, 25 to 40 mm Hg). The temperature was maintained at P P P =.03), and for CK-BB, the group 1 value was 108±22 versus 617±154 for group 2 ( P =.03). Neurological evaluation using deficit scores (NDS) was based on a modification of the Glasgow Coma Scale score: 0, normal; 1, minimal abnormality; 2, weakness; 3, paralysis; 4, coma; and 5, death. At days 1 and 2 after surgery, NDS (mean±SEM) were 0±0 for the experimental group versus 1.5±0.5 for the control group. At days 3 and 7 after surgery, NDS were 0±0 for group 1 versus 1.0±1.0 for group 2. Conclusions The faster neurological recovery of dogs treated with the “intracellular-type” maintenance solution supports the biochemical data showing the benefits of this type of blood substitute for extending the safe limits of hypothermic cardiac arrest procedures to >3 hours.

This study compared the effects of 3 hours of cardiac arrest performed at 2 different levels of profound hypothermia in totally exsanguinated, blood substituted dogs. Dogs (N = 10) were anesthetized and esophageal temperature was lowered to 24 degrees at which time exsanguination began. Once exsanguination was complete and the heart had arrested, continuous whole body perfusion of an oxygenated blood substitute solution was performed for 3 hours. Core temperature during this period remained below 10 degrees C and reached nadirs of 1.3 degrees C in Group 1 (N = 5) versus 7.3 degrees C in Group II (N = 5). Once the dog was allowed to rewarm to 10 degrees C replacement of the perfusate with blood was begun. All dogs survived the procedure but 2 dogs from each group died by 4 days following the experiment. The remaining 6 dogs were observed for between 10 and 85 days. The group perfused with blood substitute at the warmer nadir had a faster recovery of motor behavior and showed smaller changes from normal in several biochemical and hematological parameters. These findings indicate that profound hypothermia and total blood substitution can be successfully achieved at either temperature nadir, but the warmer level appears to be associated with a faster recovery.

Direct facial nerve stimulation and monitoring during cerebellopontine angle (CPA) tumor surgery are critical for identification and preservation of function. Electrically evoked facial nerve monitoring was compared with ulnar train-of-four monitoring under progressive neuromuscular blockade. Using a rabbit model, the facial nerve function of six controls was compared to that of six specimens with acute or chronic injuries. Eight of 18 patients who had undergone CPA tumor resection during one year were also studied. Regression analysis correlated between ulnar nerve monitoring and facial electromyographic (EMG) peak voltage in all groups. Facial EMG was measurable, even with 75 percent receptor blockade. The results of this study support the hypothesis that high degrees of neuromuscular blockade do not preclude satisfactory EMG monitoring of the facial nerve during CPA tumor surgery. This study did demonstrate that chronically injured facial nerves may show greater sensitivity to the effects of neuromuscular blockade. Lower levels or avoidance of neuromuscular blockade should be employed under these circumstances.

Rewarming, a key event in resuscitation from accidental, experimental and clinical hypothermia, is sometimes followed by neurologic, cardiac, and respiratory sequelae and may lead to death. The rate of rewarming has been implicated but not quantified as etiologic in these sequelae. Under anesthesia fifteen dogs were cannulated and connected to an extracorporeal circuit for oxygenation, core cooling and rewarming. They were subjected to ultra-profound hypothermia with a core (esophageal) temperature as low as 1.3 degrees C, cardiac arrest, blood substitution, and continuous low flow perfusion. After 2-3 hours of cardiac arrest, rewarming began. Mechanical activity of the heart was seen between 10 degrees and 28 degrees C and respiration resumed at 29 degrees C. The rewarming rates of the 15 dogs were retrospectively studied. They were placed into three categories (G) based on the outcome. G-I (N=2):no neurological complications, G-II (N=8):transient neurological problems, and G-III (N=5):death, mainly from cardiovascular and respiratory complications confirmed at death by autopsy. Heat gain by each animal was recorded as a function of time for all experiments. The time it took each dog to reach 35 degrees C was determined and a mean was calculated (rewarming rate). Normal body temperature for a dog is 37.8 degrees C. Statistical analysis (ANOVA) was performed ex post facto to determine the relationship between rewarming rate and outcome. Our data contradicts the notion that slow core rewarming from nadir to normal temperature offers better outcome.(ABSTRACT TRUNCATED AT 250 WORDS)

Priming fluids for cardiopulmonary bypass have been extremely varied, with resultant hemodilution. Furthermore, major surgeries utilizing cardiopulmonary bypass require multiple postoperative transfusions of blood and blood products. The appeal of having a readily available blood substitute for major cardiovascular and neurosurgical operations could prove to be a life saver, while also eliminating the risk of diseases transmitted by transfusion. Blood substitutes could also lessen the reported complications resulting from blood damage due to prolonged circulation of the blood by the extracorporeal pump. A technique was examined in 15 dogs using hypothermia for maximum metabolic suppression, incorporating an aqueous blood substitute (Cryomedical Sciences, Inc., Rockville, MD). The anesthetized animals were cannulated for extracorporeal pump oxygenation. As temperature was lowered the dogs were exsanguinated and volume replaced with blood substitute to lower the hematocrit to less than 1%. After 3 hours of cardiac arrest and continuous perfusion at a core temperature less than 10 degrees C, rewarming began. When temperature reached greater than or equal to 10 degrees C, the blood substitute was drained and the animals were autotransfused. The heart was started at 15 degrees C and spontaneous respiration resumed at 29 degrees C. Using the first generation blood substitute the survival rate was maximal (100%) at 2.5 hrs under 10 degrees C and 3 hours of cardiac arrest. Research is underway on a new blood substitute, which is to serve as a universal hypothermic preservation solution (in situ organ preservation).(ABSTRACT TRUNCATED AT 250 WORDS)

The picture we get of this region from 9.0.0.0.0 to 9.12.10.0.0 (435 A.D. to 682 A.D.) is that of a considerable number of more or less independent communities united by the use of the same calendar, the same general system of hieroglyphic writing, and similar lunar calendars. Their lunar calendars all agree at any given date, within a day or two, on the age of the moon. They may differ on whether the moon is 19 or 20 days old at a given date, but the agreement is as close as we could expect if the statement of the age of the moon is based on observation and not on a fixed calendar. At least there is no evidence of an uncorrected cumulative error. There is, however, a wide difference in their statements regarding the position of the moon in the lunar year. Whether at a given date the moon is the first or the third or the sixth moon of a lunar half year differs from city to city.

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