J. Schulte am Esch

Cardiovascular and metabolic responses to anesthetic-induced malignant hyperthermia in swine

Background Several cardiovascular disturbances, such as tachycardia and hypotension, are observed during human and porcine malignant hyperthermic (MH) crises. However, the pathophysiologic mechanisms responsible for the deterioration of cardiovascular function during MH are not completely known. The purpose of this study was to elucidate the changes in left ventricular (LV) function and metabolism and the systemic and regional hemodynamics during anesthetic-induced MH in swine.

Alterations in Brain Electrical Activity May Indicate the Onset of Malignant Hyperthermia in Swine

The time course of changes in brain electrical activity during halothane anesthesia was examined in 12 malignant hyperthermia-susceptible (MHS) and 14 normal (nMHS) swine. Power densities in selected frequency bands were calculated from the electroen-cephalogram (EEG). EEG and systemic variables were determined over a period of 60 min after starting halothane (1% inspired). Malignant hyperthermia (MH) was triggered in all susceptible pigs. Initial changes in the EEG during development of MH consisted of a decrease in total power and a shift to lower frequencies (delta-theta activity) in all animals. These EEG alterations were noted when there was an increase in heart rate, but other systemic variables were still normal. EEG changes in all MHS animals started at an arterial oxygen tension (PaO2) greater than 90 mmHg and an arterial carbon dioxide tension (PaCO2) less than 50 mmHg. In 5 MHS animals EEG became isoelectric at a PaO2 of 61-82 mmHg and a PaCO2 of 53-68 mmHg. Mean arterial blood pressure at this time was 54-66 mmHg. To determine the effects of hypoxia on the EEG in 7 nMHS animals, oxygen was decreased over a period of 45-60 min to 7% inspired. In 7 other nMHS animals, hypercarbia was produced by admixture of carbon dioxide to the fresh gas supply to achieve incremental increases of PaCO2 to 110-120 mmHg. Significant EEG changes during hypoxia comparable to those seen at the onset of MH were noted at a PaO2 below 40 mmHg and during hypercarbia at a PaCO2 greater than 68 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

DETECTION OF VENOUS EMBOLISM DURING INTRAOPERATIVE MONITORING BY TWO-DIMENSIONAL TRANSESOPHAGEAL ECHOCARDIOGRAPHY

12 patients (mean age: 81 +/- 9 years) undergoing total hip replacement because of transcervical femoral fractures were studied intraoperatively by two-dimensional transoesophageal echocardiography (TEE). The purpose of this study was to evaluate the ability of this new technique for detection of embolic events in the right heart by intraoperative 2D-TEE monitoring during hip surgery. In all patients (pts) we observed a transient increase of contrast intensity in the right atrium immediately after insertion of the acetabulum prosthesis (snow flurry). Contrast was maximal 15-20 seconds after insertion and persisted for approximately 2 min. While contrast intensity decreased in the minutes thereafter, in 3 pts contrast became more heterogeneous:we detected structures like flakes passing the right heart, sometimes circulating for some seconds in the right atrium respectively the right ventricle. Detected embolism was followed by a transient decrease of arterial pO2 (greater than 10 mmHg) in 5 pts. However, haemodynamic responses occurred infrequently; 4 pts experienced no changes at this moment. During insertion of the femoral prosthesis the contrast events were even more pronounced and persistent. In all pts we observed the appearance of flake-like structures passing the right atrium and the right ventricle, some measuring up to 6 cm in length. This was accompanied in 10 pts with a decrease (greater than 10 mmHg) of arterial pO2 and in 8 pts with a decrease (greater than 5 mmHg) of endtidal CO2.(ABSTRACT TRUNCATED AT 250 WORDS)