Characterization of the anisotropic deformation of the right ventricle during open heart surgery.

Digital Image Correlation (DIC) was used for studying the anisotropic behavior of the thin walled right ventricle of the human heart. Strains measured with Speckle Tracking Echocardiography (STE) were compared with the DIC data. Both DIC and STE were used to measure longitudinal strains of the right ventricle in the beginning of an open-heart surgery as well as after the cardiopulmonary bypass. Based on the results, the maximum end-systolic strains obtained with the DIC and STE change similarly during the surgery with less than 10% difference. The difference is largely due to the errors in matching the longitudinal direction in the two methods, sensitivity of the measurement to the positioning of the virtual extensometer of in both STE and DIC, and physiological difference of the measurements as the DIC measures the top surface of the heart whereas the STE obtains the data from below. The anisotropy of the RV was measured using full field principal strains acquired from the DIC displacement fields. The full field principal strains cover the entire region of interest instead of just two points as the virtual extensometer approach used by the STE. The principal strains are not direction dependent measures, and therefore are more independent of the anatomy of the patient and the exact positioning of the virtual strain gage or the STE probe. The results show that the longitudinal strains alone are not enough to fully characterize the behavior of the heart, as the deformation of the heart can be very anisotropic, and the anisotropy changes during the surgery, and from patient to patient.

An Optical Method for the In-Vivo Characterization of the Biomechanical Response of the Right Ventricle.

The intraoperative in-vivo mechanical function of the left ventricle has been studied thoroughly using echocardiography in the past. However, due to technical and anatomical issues, the ultrasound technology cannot easily be focused on the right side of the heart during open-heart surgery, and the function of the right ventricle during the intervention remains largely unexplored. We used optical imaging and digital image correlation for the characterization of the right ventricle motion and deformation during open-heart surgery. This work is a pilot study focusing on one patient only with the aim of establishing the framework for long term research. These experiments show that optical imaging and the analysis of the images can be used to obtain similar parameters, and partly at higher accuracy, for describing the mechanical functioning of the heart as the ultrasound technology. This work describes the optical imaging based method to characterize the mechanical response of the heart in-vivo, and offers new insight into the mechanical function of the right ventricle.

Hyperglycemic Episodes Are Associated With Postoperative Infections After Cardiac Surgery.

BACKGROUND AND AIMS: To describe the incidence of and risk factors for postoperative infections and the correlation between postoperative hyperglycemia despite tight blood glucose control with infectious and other complications after contemporary cardiac surgery. MATERIAL AND METHODS: The study comprised 1356 consecutive adult patients who underwent cardiac surgery between January 2013 and December 2014 and were followed up for 6 months. Patients surviving the first 2 days were included in the analysis. Preoperative demographic information, medical history, procedural details, and the postoperative course were recorded. The target range for blood glucose levels was 4-7 mmol/L and repeated arterial blood samples were obtained during the intensive care unit stay. The associations of blood glucose levels during the first postoperative day and the occurrence of postoperative infections and other significant complications were analyzed. RESULTS: Of the study cohort, 9.8% developed infectious complications which were classified as major surgical site infections in 2.2%, minor surgical site infections in 1.1%, lung infections in 2.0%, unclear fever or bacteremia in 0.3%, cannula or catheter related in 2.6%, multiple in 1.5%, and other in 0.2%. The incidence of deep sternal wound infection was 2.0%. Repeated hyperglycemia occurred in 39.7% of patients and was associated with increased rates of postoperative infections, 12.1% versus 8.2%, p = 0.019; stroke, 4.9% versus 1.5%, p < 0.001; and mortality, 6.1% versus 2.1%, p < 0.001, when compared to patients with single or no hyperglycemia. CONCLUSION: Every 10th patient develops infectious complications after cardiac surgery. Repeated hyperglycemia is associated with increased rates of infectious complications, stroke, and mortality.

Bedside diagnosis of persistent post-sternotomy pain.

BACKGROUND: The prevalence of persistent post-sternotomy pain (PPSP) varies largely and has been mainly studied using questionnaires. We decided to perform a systematic qualitative and quantitative sensory examination study on a power-calculated sample of patients who had undergone sternotomy for cardiac surgery. Pain was diagnosed as PPSP if the patient complained of sternal pain that had developed after surgery together with corresponding sensory disturbances. PATIENTS AND METHODS: One hundred elective patients undergoing coronary artery bypass via sternotomy were recruited for dynamic sensory mapping 4-6 months after surgery. Sensory testing was performed using thermal rollers, a cotton stick and pinprick. The intensity of sensation was registered as a score on a numeric rating scale. The area of sensory dysfunction on the chest wall was traced onto paper and calculated with the help of a computer-based program. The patient also answered a validated pain questionnaire. RESULTS: Altogether 90 patients took part in the examination. Thirteen (15.4%) of the patients had pain and formed the PPSP group, while the remaining patients formed the non-PPSP group. Both groups had sensory abnormalities over the chest wall (69% of all patients). Sensory disturbances were more common, more profound and extended over a larger skin area in the PPSP group. Furthermore, daily activity performance in the PPSP group was poorer compared to the non-PPSP group. CONCLUSION: PPSP is a clinical diagnosis easily achieved using simple diagnostic tools and a medical history. Severity and extent of sensory abnormalities were found to be greater in the PPSP group.

Postoperative hyperalgesia does not predict persistent post-sternotomy pain; observational study based on clinical examination.

BACKGROUND: Persistent post-sternotomy pain is a common problem, but the risk of developing it varies among patients. We sought to find out whether the risk of persistent post-sternotomy pain could be predicted by measuring the area of acute sensory dysfunction around the sternotomy wound. The secondary aim was to determine risk factors for persistent post-sternotomy pain. PATIENTS AND METHODS: Hundred patients who were scheduled to undergo elective coronary artery bypass surgery were recruited to the study. Patients were excluded if they had undergone previous cardiac surgery or if they lacked co-operation. Preoperative pain scores were determined and the patients filled in questionnaires about depression, anxiety, and pain. The area of sensory dysfunction around the sternotomy wound was assessed by pin prick on postoperative day 4. The presence of persistent post-sternotomy pain was determined at a follow-up evaluation at 4-6 months after surgery. RESULTS: The sizes of the area of hyperalgesia or overall sensory dysfunction were not associated with persistent post-sternotomy pain. Independent risk factors for persistent post-sternotomy pain were found to be smoking and high pain score on postoperative day 1. The prevalence of persistent post-sternotomy pain in our study population was 38% analyzed by only the questionnaire and 15% according to the clinical examination. CONCLUSION: Measuring the area of hyperalgesia in the acute phase does not give any additional information on the risk of developing a persistent post-sternotomy pain. We do thus not recommend measuring the area in this particular group of patients. Evaluation of pain by only a questionnaire risks to overestimate the presence of persistent post-sternotomy pain as compared to clinical examination.

Preoperative and perioperative use of levosimendan in cardiac surgery: European expert opinion.

In cardiac surgery, postoperative low cardiac output has been shown to correlate with increased rates of organ failure and mortality. Catecholamines have been the standard therapy for many years, although they carry substantial risk for adverse cardiac and systemic effects, and have been reported to be associated with increased mortality. On the other hand, the calcium sensitiser and potassium channel opener levosimendan has been shown to improve cardiac function with no imbalance in oxygen consumption, and to have protective effects in other organs. Numerous clinical trials have indicated favourable cardiac and non-cardiac effects of preoperative and perioperative administration of levosimendan. A panel of 27 experts from 18 countries has now reviewed the literature on the use of levosimendan in on-pump and off-pump coronary artery bypass grafting and in heart valve surgery. This panel discussed the published evidence in these various settings, and agreed to vote on a set of questions related to the cardioprotective effects of levosimendan when administered preoperatively, with the purpose of reaching a consensus on which patients could benefit from the preoperative use of levosimendan and in which kind of procedures, and at which doses and timing should levosimendan be administered. Here, we present a systematic review of the literature to report on the completed and ongoing studies on levosimendan, including the newly commenced LEVO-CTS phase III study (NCT02025621), and on the consensus reached on the recommendations proposed for the use of preoperative levosimendan.

Preoperative levosimendan infusion in combined aortic valve and coronary bypass surgery.

BACKGROUND: Cardiopulmonary bypass may have detrimental effects on intestinal function and decrease the concentrations of the active, long-acting metabolites of levosimendan, an inodilator used to improve cardiac function. The aim of this study was to evaluate the haemodynamic effects of preoperative levosimendan in patients undergoing high-risk cardiac surgery. METHODS: Twenty-four patients were randomized to receive levosimendan (12 µg bolus followed by an infusion of 0.2 µg kg(-1) min(-1)) or a placebo 24 h before surgery. The inclusion criteria were left ventricular ejection fraction (LVEF) <50% or LV hypertrophy indicated by a wall thickness of >12 mm. Haemodynamics were recorded every hour for 24 h (pulmonary artery catheter) and daily until postoperative day 4 (whole-body impedance cardiography). Doppler echocardiography with tissue Doppler imaging was used to assess systolic and diastolic cardiac function. RESULTS: The cardiac index (CI) and stroke volume index (SI) were higher in the levosimendan group (LG) for the 4 day postoperative period (P<0.05); on the fourth postoperative day, the CI was 3.0 litre m(-2) min(-1) in the LG compared with 2.4 litre m(-2) min(-1) in the control group (CG) and the SI was 30 vs 25 ml m(-2), respectively. The LVEF measured at baseline and on the fourth postoperative morning decreased in the CG, but was maintained in the LG. CONCLUSIONS: Levosimendan improved haemodynamics compared with a placebo in patients undergoing high-risk cardiac surgery. The concentrations of levosimendan's metabolites were higher compared with earlier studies using perioperative dosing.

Hyper osmolality does not modulate natriuretic peptide concentration in patients after coronary artery surgery.

BACKGROUND: The heart secretes natriuretic peptides (NPs) in response to myocardial stretch. Measuring NP concentrations is a helpful tool in guiding treatment. It has been suggested that sodium ion and hyperosmolality could affect NP excretion. If this is true, peri-operative NP measurements could be inconsistent when hypertonic solutions are used. With different osmolalities but equal volumes of hydroxyethyl starch (HES)--and hypertonic saline (HS)--infusions, this double-blinded study tested the hypothesis that osmolality modulates the excretion of NPs. METHODS: Fifty coronary surgery patients were randomized to receive within 30 min 4 ml/kg either HS or HES post-operatively. Samples for analysis of atrial NP (ANP), brain NP (BNP), plasma and urine sodium and osmolality and urine oxygen tension were obtained before and 60 min after starting the infusions and on the first post-operative morning. The haemodynamic parameters were measured at the same time points. RESULTS: Plasma osmolality and sodium increased only in the HS group. Changes in plasma BNP and ANP levels did not differ between the groups (P=0.212 and 0.356). There were no correlations between NP levels and osmolality or sodium at any time point. In the HS group, urine volume was higher (3295 vs. 2644 ml; P<0.05) and the need for furosemide treatment was less (0.4 vs. 3.8 mg; P<0.01) than in the HES group. CONCLUSIONS: The absence of effects of plasma sodium content or hyperosmolality on NP release validates the value of NPs as a biomarker in peri-operative patients.

Pre-operative oral carbohydrate treatment before coronary artery bypass surgery.

BACKGROUND: Cardiac surgery is a stress that causes insulin resistance, which leads to an increase in insulin requirement. The aim of the present study was to evaluate the effect of a pre-operative oral carbohydrate drink vs. overnight fasting on perioperative insulin requirements in non-diabetic patients undergoing elective coronary artery bypass grafting (CABG) surgery. METHODS: One hundred and one patients scheduled for CABG were enrolled in the study. After fasting overnight, the patients were randomised into two groups. In the control group (C), no drink was given in the morning. In the treatment group (T), the patients ingested 400 ml of carbohydrate fluid 2 h before induction of anaesthesia. Blood glucose and insulin requirement was recorded. Gastric drainage was measured. Post-operative nausea and vomiting was recorded. RESULTS: Neither the number of patients requiring insulin nor the amount of insulin required to maintain normoglycaemia differed between the study groups. More patients in the treatment group experienced nausea post-operatively (26 vs. 16, P=0.044), but vomiting was equally common in the study groups (10 vs. 7). Intra-operative gastric drainage was 26.8+/-57.9 ml in the treatment group vs. 16+/-37.9 ml in the control group (NS). CONCLUSION: In this study patient population, a pre-operative oral carbohydrate drink did not reduce post-operative insulin resistance or post-operative nausea and vomiting. According to our findings, it is safe to allow cardiac surgery patients to drink clear fluids up to 2 h before induction of anaesthesia, because gastric emptying of the drink was almost total and no aspiration occurred.

Effects of hypertonic saline (7.5%) on extracellular fluid volumes in healthy volunteers.

This study evaluated the effects of 7.5% saline on plasma and other extracellular fluid volumes. After baseline measurements, eight healthy postmenopausal female volunteers received 4 ml.kg-1 of hypertonic saline over 30 min. After the fluid infusion, the volunteers were studied for 60 min. Plasma volume was measured using a dilution of 125-iodine-labelled human albumin. Extracellular water and cardiac output were measured by whole body impedence cardiography. The infused volume was 4 ml.kg-1 (average 260 ml). Plasma volume increased rapidly during the infusion (mean +/- standard deviation, 442 +/- 167 ml). At the end of the 1-h follow-up period, plasma volume had increased by on average 465 ml (SD 83). The increase of extracellular water at the end of infusion and at the end of study was 650 ml (SD 93) and 637 ml (SD 192), respectively. The highest serum sodium recorded in the volunteers was 158 mmol.l-1. The effect of 7.5% saline on plasma volume was rapid and lasted for at least 1 h. Plasma volume remained elevated by more than the infused volume at the end of the study. The increase in plasma and extracellular fluid volumes was partly achieved by mobilizing intracellular water to extracellular compartment.

A novel reconstruction technique for chronic lateral ankle instability: comparison to primary repair.

Twenty patients with lateral ankle instability were treated by a novel anatomical reconstruction technique (group A) and the results compared with 20 patients (group B) who, during the same period of time, underwent primary repair of ruptured lateral ligaments of the ankle. We reviewed 15 patients from group A and 17 patients from group B at a mean follow-up of between 2 and 4 years. The mean functional scores were good in both groups without significant difference, and there was no difference in the mean anterior talar translation between the two groups. We therefore conclude that chronic lateral instability of the ankle may be successfully treated, even in the presence of severely damaged, attenuated or absent ligament tissue.

Graft placement after the anterior cruciate ligament reconstruction: a new method to evaluate the femoral and tibial placements of the graft.

In order to evaluate graft placement of the anterior cruciate ligament (ACL) reconstruction and its relationship to the clinical outcome of the patient, 100 patients were examined 7 years after an ACL reconstruction. Clinical assessment was performed using the standard knee ligament evaluation form of the International Knee Documentation Committee (IKDC), and the Lysholm and the Marshall knee scores. We developed a new evaluation method of graft placement after an ACL reconstruction, 'the sum score of the graft placement', which takes into account both the femoral and the tibial positions of the graft simultaneously, and our study showed that 'the sum score of the graft placement' has an association to clinical outcome of patients and that it can better explain the long-term osteoarthritic changes at the injured knee than the separate measurements of the femoral and tibial tunnel placements.

Effects of hypertonic 75 mg/ml (7.5%) saline on extracellular water volume when used for preloading before spinal anaesthesia.

BACKGROUND: Prevention of hypotension during spinal anaesthesia is commonly achieved using fluid preloading. This may result in a substantial amount of excess free water retained in the body after spinal anaesthesia. We aimed to evaluate the effects of 7.5% hypertonic saline on extracellular water volume and haemodynamics when used for fluid preloading before spinal anaesthesia. METHODS: This randomised double-blind study evaluated the effects of 75 mg/ml (7.5%) hypertonic saline (HS) on extracellular water volume and haematocrit in patients undergoing arthroscopy or other lower limb surgery under spinal anaesthesia. Amounts of 1.6 ml/kg of HS (20 patients) or 13 ml/kg of 9 mg/ml normal saline (20 patients) were administered for preloading before spinal anaesthesia with a 10 mg dose of 0.5% hyperbaric bupivacaine. Etilefrine was administered in order to maintain mean arterial pressure (MAP) at >or=80% of its baseline value. Whole-body impedance cardiography-derived cardiac index (CI) and extracellular water (ECW) were measured. RESULTS: There were no significant differences in demographic data or in the number of blocked segments. ECW remained similar in both groups despite the much smaller amount of infused free water in the HS group. There were no significant differences between the groups in CI values during the study. The amount of etilefrine administered was similar in the treatment groups. Dilution of haematocrit was also similar in both groups. CONCLUSION: Hypertonic 75 mg/ml (7.5%) saline is an alternative for preloading before spinal anaesthesia in situations where excess free water administration is not desired. It is effective in small doses of 1.6 ml/kg, which increase the extracellular water, plasma volume and cardiac output, and thus maintain haemodynamic stability during spinal anaesthesia.

Effects of hypertonic saline (7.5%) on extracellular fluid volumes compared with normal saline (0.9%) and 6% hydroxyethyl starch after aortocoronary bypass graft surgery.

OBJECTIVE: To compare the effects of hypertonic (7.5%) saline (HS), normal (0.9%) saline (NS), and 6% hydroxyethyl starch (HES) on extracellular fluid volumes in the early postoperative period after cardiopulmonary bypass. DESIGN: A prospective, randomized, double-blind study. SETTING: University teaching hospital. PARTICIPANTS: Forty-eight patients scheduled for elective coronary artery bypass graft surgery. INTERVENTIONS: Patients were randomly allocated to receive 4 mL/kg of HS, NS, or HES during 30 minutes when volume loading was needed during the postoperative rewarming period in the intensive care unit. Plasma volume was measured using a dilution of iodine-125-labeled human serum albumin. Extracellular water and cardiac output were measured by whole-body impedance cardiography. MEASUREMENTS AND MAIN RESULTS: Plasma volume had increased by 19 +/- 7% in the HS group and by 10 +/- 3% in the NS group (p = 0.001) at the end of the study fluid infusion. After 1-hour follow-up time, the plasma volume increase was greatest (23 +/- 8%) in the group receiving HES (p < 0.001). The increase of extracellular water was greater than the infused volume in the HS and HES groups at the end of the infusion. One-hour diuresis after the study infusion was greater in the HS group (536 +/- 280 mL) than in the NS (267 +/- 154 mL, p = 0.006) and HES groups (311 +/- 238 mL, p = 0.025). CONCLUSION: The effect of HS on plasma volume was short-lasting, but it stimulated excretion of excess body fluid accumulated during cardiopulmonary bypass and cardiac surgery. HS may be used in situations in which excess free water administration is to be avoided but the intravascular volume needs correction.

Hypertonic saline (7.5%) after coronary artery bypass grafting.

BACKGROUND AND OBJECTIVE: Patients undergoing coronary artery bypass grafting often require volume loading after operation. In this situation hypertonic saline may be beneficial in restoring the haemodynamic balance and removing excess extravascular fluid. METHODS: Forty coronary artery bypass grafting patients were randomly assigned to receive either hypertonic saline 7.5% (20 patients) or 0.9% saline (20 patients) as a single dose of 4 mL kg-1 over 30 min in the postoperative rewarming phase in the intensive care unit. RESULTS: Mean arterial pressure increased in the hypertonic saline group from 82 +/- 10 (SD) to 104 +/- 17 mmHg (P = 0.002) vs. the normal saline group), and the cardiac index rose from 2.3 +/- 0.5 to 3.4 +/- 0.8 L min-1 m2 (P = 0.002 vs. the normal group). The haemodynamic effect of hypertonic saline lasted only about 1 h. Diuresis was greater in the hypertonic saline group both at 1 h (hypertonic saline: 490 +/- 274 vs. normal saline: 204 +/- 130 mL; P = 0.001) and 10 h (hypertonic saline: 1952 +/- 554 vs. normal saline: 1421 +/- 514 mL; P = 0.003). CONCLUSIONS: No adverse effects were seen. The hypertonic saline had a strong diuretic effect and may be beneficial in coronary artery bypass graft patients after operations. This is because of its value as a short-term plasma expander and the diuresis eliminates excessive fluid from the body. A larger study is needed to determine whether the benefits outweigh the possible side-effects in these patients.

The comparison of hypertonic saline (7.5%) and normal saline (0.9%) for initial fluid administration before spinal anesthesia.

Hypertonic saline can be used for initial fluid administration before spinal anesthesia. It is effective in small-volume fluid resuscitation. This randomized double-blinded study compared the effects of 7.5% hypertonic saline (HS) and 0.9% normal saline (NS) in doses containing 2 mmol/kg of sodium in 40 ASA physical status I-II patients undergoing arthroscopy or other lower limb surgery under spinal anesthesia. We infused 1.6 mL/kg of HS or 13 mL/kg of NS for initial fluid administration before spinal anesthesia induced with a 10-mg dose of 0.5% hyperbaric bupivacaine. Etilefrine was administered to maintain mean arterial pressure at > or =80% of its control value. Systolic and diastolic blood pressure, heart rate, and cardiac index did not differ between the groups, and the amount of etilefrine administered was similar in the treatment groups. In all our patients, the plasma sodium concentrations were within the normal range after surgery and serum osmolality was within the normal range after spinal anesthesia. The time and the volume of the first micturition were similar in both groups, despite the much smaller amount of infused free water in the HS group. We conclude that 7.5% HS was as good as NS for the initial fluid administration before spinal anesthesia when the amount of sodium was kept unchanged.