Effects of therapeutic hypothermia on left ventricular function assessed by ultrasound imaging.

BACKGROUND: Therapeutic hypothermia is used after cardiac arrest. The aim of this study was to investigate the effects of therapeutic hypothermia on left ventricular (LV) function assessed by ultrasonic imaging. METHODS: In 10 pigs, LV volumes, ejection fractions, and longitudinal strain were measured using two-dimensional echocardiography. Midwall fractional shortening and end-systolic wall stress were calculated. Wall thickness was continuously measured using an epicardial ultrasonic transducer placed on the LV anterior wall. Wall thickening velocity (S') and pressure-wall thickness loops were used to assess systolic function. Diastolic function was assessed by echocardiographic transmitral flow and mitral annular velocity (e') measurements, calculation of the LV relaxation constant, and determination of LV stiffness and restoring forces using the end-diastolic pressure-wall thickness relation during volume unloading. Early wall thinning velocity (e'wt) and early diastolic wall thinning were calculated. Measurements were done at 38°C and 33°C, at spontaneous heart rate and at atrial pacing at 100 beats/min. RESULTS: End-diastolic volume, stroke volume, midwall fractional shortening, and longitudinal strain remained unchanged during hypothermia, but end-systolic wall stress, S', and pressure-wall thickness loop area decreased. A shift from early to late diastolic LV filling occurred during hypothermia, with concurrent decreases in e', e'wt, and early wall thinning fraction. Relaxation was prolonged, LV stiffness was increased, and restoring force was decreased during hypothermia. Hypothermia induced a decrease in relative diastolic duration at spontaneous heart rate, which was further reduced during pacing. During paced heart rate at 33°C, stroke volume, ejection fraction, and strain were reduced. CONCLUSIONS: Hypothermia induced systolic and diastolic dysfunction, with reduced tolerance to increased heart rate. These findings may have implications for patient management during hypothermia.

Automated detection of myocardial ischaemia by epicardial miniature ultrasound transducers--a novel tool for patient monitoring during cardiac surgery.

OBJECTIVES: Early detection of myocardial ischaemia in cardiac surgery is important. We have developed an ultrasonic system for continuous myocardial monitoring by use of miniature transducers. The aim of this study was to investigate the system's ability to detect ischaemia in patients undergoing off-pump coronary artery bypass grafting (CABG), and whether automated signal analysis could detect ischaemia. METHODS: In 10 patients scheduled for CABG, ultrasound transducers were fixed to the epicardium in the area supplied by left anterior descending artery (LAD), and in a remote area for control. M-mode images with measurements of wall-thickening velocities were presented in real time and systolic (S') and post-systolic velocities (PSVs) were recorded. An automated algorithm for ischaemia detection was developed, using end-systolic wall thickening as a fraction of total wall thickening. Registrations were made at baseline and during LAD occlusion. Echocardiographic strain was used as reference. RESULTS: Nine of 10 patients developed ischaemia during LAD occlusion, with resulting decrease in systolic and increase in post-systolic wall-thickening velocities (P<0.001). In these nine patients, Vdiff shifted below zero with no overlap between baseline and LAD occlusion (P<0.001). The automated wall-thickening fraction was reduced from 0.93±0.05 to 0.57±0.15 (P=0.001). A cut-off value of 0.85 could completely separate normal from ischaemic myocardium in all patients. CONCLUSION: The ultrasonic system detected regional ischaemia during LAD occlusion. An automated analysis algorithm demonstrated excellent ability to detect ischaemia. This technology can develop into a useful tool to detect ischaemia in cardiac surgery.

[Anaesthesia for open-heart surgery in adults]. / Anestesi ved åpen hjertekirurgi hos voksne.

BACKGROUND: Each year, about 5 000 adults undergo heart surgery (most of them open-heart surgery) in Norway. The purpose of this overview is to address specific problems associated with anaesthesia in these patients. MATERIAL AND METHODS: The paper is based on literature identified through a non-systematic search in PubMed and own experience with clinical work and research. RESULTS: In Norway, general anaesthesia is always used in open-heart surgery. Some patients have such severely impaired heart function that it needs to be supported by inotropic drugs or mechanical devices. The patients are given heparin during surgery, and many also receive preoperative treatment with drugs that affect haemostasis. Profuse bleeding, during or after surgery, is sometimes challenging. The brain is at risk because the blood flow generated by the heart-lung machine is unphysiological, and because air or solid particles may embolize from the heart or aorta during the intervention. Renal failure after heart surgery is a serous complication with high mortality. Some anaesthetics probably have direct cardioprotective effects. Tight control of blood glucose seems to be justified, even if the level of optimal serum blood glucose is still debated. INTERPRETATION: Several organ systems are at risk during heart surgery. In addition to providing pleasant and painless sleep for the patient and good working conditions for the surgeon, the anaesthetist cooperates with the team about securing optimal organ protection.

[Acute renal failure in critically ill patients]. / Akutt nyresvikt hos intensivpasienter.

BACKGROUND: Acute renal failure is common in critically ill patients and is associated with a high mortality rate. This paper reviews current management of patients with acute renal failure admitted to an intensive care unit. MATERIAL AND METHODS: Literature search in databases (Medline, Cochrane database of systematic reviews, UpToDate). RESULTS: The prevalence of acute renal failure is 5-20 % in patients admitted to intensive care units; the associated hospital mortality is 30-60 %. The aetiology is usually multifactorial; inflammation (sepsis, surgery), hypovolaemia and drug toxicity commonly precipitate acute renal failure. There is no effective drug treatment, but early onset of renal replacement therapies with haemodialysis or haemofiltration is likely to prolong survival. INTERPRETATION: Despite modern intensive care, mortality is high in acute renal failure and preventive measures should therefore be vigorously pursued. Haemodialysis and haemofiltration should be introduced early in acute renal failure, and should be available in all intensive care units.