ABSTRACTS-TENTH ANNUAL MEETING 511

At higher concentrations of DMSO a loss of cell potassium and increase in sodium and liquid vol- ume results. It is concluded that DMSO probably does not penetrate the cell membrane freely and completely, and that the extent of its penetration is influenced by associated solutes. (Supported in part by National Institutes of Health Grant No. GM 17959. )

18. An Instrument for Monitoring Tissue Per/u- sion Rates in Isolated Organs. H. F. BOW- MAN AND T. A. BALASUBRAMANIAM (Me- chanical Engineering Department, North- eastern University, Boston, Massachusetts 02115).

If tissues and organs are to be preserved by freezing, they must be perfused first with nutrients and then with eryophylactie agents prior to the start of the freezing protocol. In order to prevent osmotic damage to the cells during perfusions it is important to maintain a proper balance between the rate of change of concentration of cryophylac- tie agent in the perfnsate and the rate at which the cryophylactie agent is transported across the cell membrane. In each ease, the proper perfusion rate can be established by trial and error; how- ever, measurement of the perfusion volume rate through the organ provides little or no information about the rate at which the perfusate permeates the tissue. An insrmnent has been developed which allows the measurement of tissue perfusion rate in isolated organs. The instrument consists of a prolate spheroid .055 in. equivalent sphere di- ameter) thermistor bead which is threaded through an 18-gauge hypodermic needle and is inserted into the tissue of interest through a 14-gauge can- nula. The power required to maintain the thermis- tor bead at a fixed temperature above the tissue temperature is monitored continuously and is a function of the thermal conductivity of the me- dium. The thermal conductivity is in turn a func- tion of the eoneentraiton of cryophylactic agent. Under isothermal conditions and a given perfusate flow rate the rate of change in steady state power is proportional to the rate of change of concen- tration of cryophylaetic agent. The instrument has been tested in isolated rat hearts. (SnDoorted in part by USPHS Grant 1 P01 HL 14322-02.)

19. An Apparatus for the Perfusion, Freezing. and Thawing of Isolated Rat Hearts. E. G. CIIAVALHO, K. R. DILLEll AND C. E. HUG- tINS (Cryogenic Engineering Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139: and De- partment of Surgery, Harvard Medical School, Surgical Low Temperature Unit

and Blood Bank Transfusion Service, Mas- sachusetts General Hospital).

Perfusion, freezing, and thawing of isolated rat hearts have been carried out in a single system. The central element of the system is a cylindrical, stainless steel chamber 2.5 cm in diameter and 4 cm long. The excised rat heart is suspended from the top cover plate of the chamber by cannulae inserted in the aorta and puhnonary artery. Ther- mally conditioned perfusate enters the heart through the aorta cannula and is discharged through the pulmonary artery cannula. The heart is immersed completely in a thermally conditioned perfnsate bath which is maintained at a constant level by a steady How of perfusate through the chamber. The top of the chamber is fitted also with ECG electrodes, thermocouple instrumenta- tion, and a fiber optic light source. With the aid of this light source, heart function and perfusate phase can be observed through a window fitted in the wall of the chamber. The walls and the floor of the chamber also form part of a forced convec- tion heat exchanger in which an ethyl alcohol- water mixture is used as the working fluid. By the use of a countercurrent heat exchanger, external to the heart chamber, this same working fluid is used to control perfusate temperature, and hence, heart temperature as well. The temperature of the working fluid is controlled by a combined refrig- eration-heating system also external to the heart chamber. A supplementary apparatus also has been developed that permits cryophylactic agent to be added to the perfusate at controlled rates such that the concentration of cryophylactic agent in the perfusate is a linear function of time until steady state is established. Associated instrumen- tation permits continuous monitoring of all tem- peratures pressures, flow rates, and concentrations, as well as the electrical activity of the heart. ( Sup- ported in part by USPHS Grant 1 P01 I-IL14322- 01 from NIH.)

20. Cryos~urgery of Parathyroid Glands. Lois M. BREmENBACrI AND WILLIAM G. PACE (De- partment of Surgery, The Ohio State Uni- versity Hospitals, 410 West 10th Avenue, Columbus, Ohio 43210).

Parathyroid ,disease managed by surgical exci- sion may result in irreversible injury to one or both recurrent laryngeal nerves. This is a report of the effectiveness of cryosurgery in destruction of parathyroid tissue in rats without thyroldeetomy or permanent injury to the recurrent laryngeal nerves. Adult male albino rats were comrmred in four groups: Cryosurgery of rm-athwoid glands, exicision of thyroid and parathyroid glands en

512 ABSTRACTS-TENTH ANNUAL MEETING

bloc, sham operation, or no treatment. The cryo- surgery group was divided into subgroups accord- ing to three patterns of repetitive freezing: appli- cation of the cryoprobe for 20 sec three times, 30 sec two times, or 60 see two times. Serum calcium concentration was determined in all four groups at 1-wk intervals after the operative procedures. Then the animals were sacrified for histological examination of the parathyroid tissue. Serum cal- cium concentration correlated with the microscopic appearance of residual parathyroid tissue in all groups. In the cryosurgery subgroups the serum calicum levels and residual parathyroid tissue cor- related with the number of applications of the cryoprobe independent of total freezing time. None of the rats exhibited severe respiratory dis- tress or loss of voice following the operative pro- cedures. Based upon this work and other reports of freezing of peripheral nerves, it is concluded that loss of function would be temporary and that early return of function would occur if the nerve were frozen inadvertently or intentionally during eryosurgical treatment. This study indicates that the extent of destruction of parathyroid glands in rats can be controlled by specific cryosurgical techniques without thyroidectomy or risk of per- manent injury to the recurrent laryngeal nerves. (Supported by a Grant from The John A. Hart- ford Foundation, Inc.)

SYMPOSIUM II--CRYOBIOLOGY IN NEUROLOGICAL SURGERY

21. Prolonged Suspended An~matlon in Puppies. YosrlIO KONDO, OSAMU KUWAI-IAlaA,* M. DON TURNER, AND JAMES D. HARDY o ( De- partment of Surge*y, University of Missis- sippi Medical Center, Jackson, Mississippi 39216).

Altnough 60-90 min of total circulatory arrest during deep hypothermia (TCADH) has been safely achieved, data concerning the permissible duration of TCADH are scant. This study was de- signed to analyze the body responses to recovery from 2.5 hr of TCADH and various measures to afford possible protection were added empirically in an attempt to obtain normal survivors. Surface- induced hypothermia (9-13 ° C) was used in 10 puppies (Series 1), and limited left-heart bypass combined with surface-induced hypothermia (10- 11 ° C) in 6 puppies (Series 2). Additional pro- phylactic modalities included intravenous adminis- tration of Pluronic-F68 and methylprednisolone, and prior flushing of the coronary and cerebral ar- teries with a solution approximating the intracel- lular electrolyte composition (IC-solution). Car- diac resuscitation succeeded uniformly. However,

brain damage (7 puppies ) and respiratory insuffi- ciency of the alveolar collapse type (7 puppies) were the main causes of death; only one of the first series survived without complications. In Se- ries 2, all died of respiratory failure within 2 days, indicating that the lung required still further protection. In a third series of 10 puppies, induc- tion of deep hypothermia was modified as follows: Ether anesthesia was discontinued at about 20 ° C, low molecular weight dextran was given intra- venously, and the pulmonary artery was also flushed with IC-solution. All of these animals re- sumed stable blood pressures, intact pupillary re- flexes, and spontaneous respiration in the innne- diate post-TCADH period. Three dogs had mild brain damage, 4 had temporary loss of vision, and all dogs evidenced hindquarter weakness; these symptoms were reversible. Severe but temporary metabolic derangements presented consistently, as reported in a separate paper. Respiratory distress was the major complication, and was the cause of death in 4 dogs. The remaining 6 dogs resumed normal activity and became chronic survivors. These results indicate that at least 2.5 hr of TCADH is possible. (Supported by USPHS Grants HL 06163 and HL 11730.)

22. Primate Survial After Deep Hypothermia (5- 8 ° C) and Ischemia (1 hr) of Brain. ROBERT J. Wriiax, LEE R. WOLIN,* NOR- MAN TASLITZ, • YOSHIRO TAKOATO, ~ JAMES C. AUSTIN', ~ AND PAUL E. AUSTIN, JR.* (Department of Neurosurgery at Cleveland Metropolitan General Hospital, Case West- ern Reserve University School of Medicine, Cleveland, Ohio 44109, and the Neuro- psychiatric Laboratory at Cleveland Psychi- atric Institute, Cleveland, Ohio 44109).

The development of techniques designed to pro- duce deep brain temperatures (below 10 ° C) for use in operative neurosurgery has been severely retarded because of the belief that thermal reduc- tions of this degree of magnitude were of them- selves injurious to cerebral tissue. As a conse- quence, the potential increase in protection which would be afforded brain at these extremely low temperatures following trauma or during purpose- ful prolonged cerebral circulatory arrest is un- established. To assist in answering these questions, the following studies were designed to examine the recoverability of the subhuman primate after 1 hr of cerebral ischemia at intracerebral tem- peratures of 5-8 ° C. Five nembutalized rhesus monkeys were traeheally intubated and" instru- mented for: arterial pressure, EEG, EGK, intra- cerebral and rectal temperatures, and lateral sinus (venous blood) sampling. Profound differential