Lithium Dilution Cardiac Output Research Articles

The Effect of Mannitol and Hypertonic Sodium Administration on Hemodynamic Parameters Under LiDCO Monitoring in Patients Undergoing Elective Craniotomy

In craniotomy surgery, it is important to maintain hemodynamics and prevent the increase of intracranial pressure. Using semi-invasive methods such as LiDCO monitoring is a good option in this situation. This study aimed to evaluate the effectiveness of mannitol and hypertonic sodium on hemodynamic parameters in patients undergoing elective craniotomy. This randomized clinical trial was done on 40 patients of both genders. Patients whose ages were between 18-65 years, who had American Society of Anesthesiologists (ASA) score I and II, and who underwent craniotomy surgery were eligible for this study. Participants were divided into two groups receiving hypertonic sodium and mannitol. Hemodynamic parameters were evaluated before surgery, 20 minutes, and 60 minutes after surgery in both groups, under Lithium dilution cardiac output (LiDCO) monitoring. The results showed that there was no difference between groups in terms of the average fluid intake, the duration of the operation, the amount of urinary output, and the primary hemodynamic characteristics. Significant differences were recorded in the evaluation of hemodynamic parameters. The results demonstrated a reduction in systolic, diastolic, and mean arterial blood pressure during 20 to 60 minutes after mannitol injection compared to hypertonic sodium injection. Additionally, the effectiveness of both therapies on maintaining cardiac function was similar, but the use of mannitol led to a greater decrease in arterial and peripheral vascular resistance. It can be concluded that mannitol may be more effective than hypertonic sodium during craniotomy procedures in terms of reducing blood pressure monitored with LiDCO.

Effects of two alveolar recruitment manoeuvres (sustained inflation and stepwise) followed by positive end-expiratory pressure on cardiac output (measured with lithium dilution), invasive blood pressure and arterial oxygen tension in isoflurane-anaesthetised goats

Alveolar recruitment manoeuvres (ARM) performed during general anaesthesia improve oxygenation; however cardiovascular depression may be observed. The aim of the study was to compare the effects of sustained inflation (SI) and stepwise ARMs on cardiac output (CO), mean arterial blood pressure and arterial oxygen tension (PaO2) in ten mechanically ventilated goats anaesthetised with isoflurane.In the SI ARM, peak inspiratory presure (PIP) was increased to 30 cmH2O and sustained for 20 s. In the stepwise ARM, the PIP was increased by 5 cmH2O each minute for three minutes from 10 to 25 cmH2O. Both ARMs were followed by positive end-expiratory pressure of 5 cmH2O. Paired lithium dilution CO measurements and arterial blood samples were obtained before and after each ARM. The order of the ARM was randomised and each goat was subjected to both techniques. Data was reported as median and interquartile range (IQR). Significance was set at 0.05.The median change in CO (measured by subtracting values after and before ARM) was −0.15 L min−1 (IQR -0.51; 0.03) and − 0.90 L min−1 (IQR -1.69; −0.58) for SI and stepwise ARM respectively (p = 0.04). The median change in PaO2 was 3 kPa (IQR -2.7; 7.6) and 0.4 kPa (IQR -3.4; 5.5) for SI and stepwise ARM respectively (p = 0.03).In conclusion, SI ARM causes less impact on CO and provides a better improvement in PaO2 compared to stepwise ARM in goats.

Elective lower limb orthopedic arthroplasty surgery in patients with pulmonary hypertension.

Patients with pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension (PH) are at increased risk when undergoing anesthesia and major surgery. Data on outcomes for elective orthopedic surgery in patients with PH are limited. A patient pathway was established to provide access to elective lower limb arthroplasty. This included assessment of orthopedic needs, fitness for anesthesia, preoperative optimization, and intra‐ and postoperative management. Patient data were retrospectively retrieved using patient's hospital records. Between 2012 and 2020, 29 operations (21 total hip replacements [THRs], 7 total knee replacements [TKRs], 1 total hip revision) were performed in 25 patients (mean age: 67 years). Perioperatively, 72% were treated with low‐dose intravenous prostanoid. All had arterial lines, and central access and perioperative lithium dilution cardiac output monitoring was used in 86% of cases. Four patients underwent GA, 21 spinal anesthesia, and 4 CSE anesthesia. Supplemental nerve blocks were performed in all patients undergoing general, and 12 of 21 undergoing spinal anesthesia. All were managed in high dependency postoperatively. Hospital length of stay and complication rates were higher than reported in non‐PH patients. Perioperative complications included hypotension requiring vasopressors (n = 10), blood transfusion (n = 7), nonorthopedic infection (n = 4), and decompensated right heart failure (n = 1). There was no associated mortality. All implants were functioning well at 6 weeks and subsequent follow‐up. EmPHasis‐10 quality of score decreased by 5.5 (±2.1) (p = 0.04). A dedicated multiprofessional pathway can be used to safely select and manage patients with PH through elective lower limb arthroplasty.

Association of plasma and urine NGAL with acute kidney injury after elective colorectal surgery: A cohort study

BackgroundAcute kidney injury (AKI) is common in surgical patients. We aimed to investigate the validity of plasma and urine neutrophil gelatinase-associated lipocalin (NGAL) in the detection of AKI and prediction of outcomes in patients undergoing major colorectal surgery. Materials and methodsThis was a pre-specified post-hoc analysis of a randomized controlled trial comparing oesophageal doppler and Lithium dilution cardiac output monitoring in high risk patients undergoing major colorectal surgery as part of an Enhanced Recovery After Surgery protocol in a tertiary care hospital. Plasma and urine samples for NGAL measurement were taken before surgery (T1), immediately after surgery (T2), and on postoperative day 1 (T3). AKI was defined according to the KDIGO criteria. ResultsA total of 89 patients were included of whom 12 (13.5%) developed AKI. Plasma NGAL significantly increased from T1 to T3 in both AKI (p < 0.001) and non-AKI (p = 0.048) patients, while urine NGAL did not change over time. There were no significant differences in plasma and urine NGAL in patients with and without AKI at all time points. Postoperative day 1 urine NGAL concentrations were significantly higher in non-survivors than survivors (41.2 versus 25 ng/mL, p = 0.026). One-year mortality was significantly higher in AKI patients with a raised urine NGAL compared to AKI patients without elevated urine NGAL levels. ConclusionsPlasma and urine NGAL poorly predicted AKI post-colorectal surgery. Non-survivors had higher urine NGAL results. More research is required to explore the association between NGAL and long-term outcomes.

Body surface area calculation for dogs and cats using LiDCO and PICCO monitors.

Cardiac output, stroke volume, and measurement of other hemodynamic parameters can be useful in the management of critical patients. Given the broad size disparity of veterinary patients, the raw values can vary widely. Their indexed values, however, allow for quick assessment of hemodynamic status and a more standardized target setting by the veterinary care team. Monitors such as lithium dilution cardiac output (LiDCO) and pulse contour cardiac output (PICCO) can display and record the data using indexed values as long as the correct body surface area (BSA) is used. In people, the BSA is calculated using the DuBois formula by entering the patient's weight and height; however, it does not apply to animals because the equivalent relationship is not represented by this formula. Given that the hemodynamic monitors are manufactured for use in human patients, the calculations need to the adapted for veterinary use. As such, the Dubois formula has been rearranged to calculate an assumed height to be entered in the monitor software along with the patient's weight. Once the information is entered, a correct BSA will be calculated by the monitor, and indexed data will be readily available for analysis. Tables with the calculated heights for dogs and cats were generated. The weights and calculated heights were computed into the LiDCO and PICCO monitors for verification, and the correct BSAs were displayed as a result. The information supplied here allows clinicians and researchers to quickly input patient data into the hemodynamic monitor and obtain indexed data. Indexed data facilitates advanced hemodynamic monitoring by standardizing targets (goal-directed therapy) and allowing for quicker comparison between patients. The table could be used with any monitor that utilizes the DuBois formula for BSA calculation, but the resulting BSA should be validated before proceeding with hemodynamic monitoring.

Does Preoperative Beta-blocker Use Influence Intraoperative Hemodynamic Profile and Post-operative Course of Liver Transplantation?

ObjectiveWe compared the intraoperative hemodynamic profiles and outcomes of liver transplant (LT) patients receiving preoperative beta-blockers for portal hypertension with those of patients not receiving beta-blockers. MethodsBeat-to-beat hemodynamic data were recorded with the use of a lithium dilution cardiac output monitor, including heart rate (HR), cardiac output (CO), cardiac index (CI), systemic vascular resistance (SVR), SVR index, mean arterial pressure, stroke volume (SV), and SV index. Perioperative data included age, sex, etiology of cirrhosis, Model of End-Stage Liver Disease score, warm and cold ischemia times, and intraoperative blood and blood products replacement. Postoperative data included Acute Physiology and Chronic Health Evaluation II score, Intensive Care National Audit and Research Centre (ICNARC) score, length of intensive care unit stay, renal replacement treatment, and mortality. ResultsAfter exclusion, 215 patients not receiving and 93 patients receiving beta-blockers for portal hypertension were included. There was no significant difference between groups in demographic data. HR, CO, and CI were significantly lower in the beta-blocker group (P = .0001). Regarding outcomes, the ICNARC score was significantly higher in the beta-blocker group (P < .05). ConclusionsPreoperative administration of beta-blockers attenuates the hyperdynamic circulation in LT patients; this is clearly seen through a reduction in intraoperative CO, CI, and HR. This decreased hyperdynamic state was not shown to relate to outcomes in any of the variables except for a higher ICNARC score reported in the group treated with beta-blockers.

Haemodynamic Monitoring of Pericardial Effusion with Cardiac Tamponade in a Patient with Colorectal Cancer

Metastatic cardiac malignancies mainly come from breast, lung, esophagus and lymphoreticular system. Metastasis from colorectal cancer to the heart or pericardium is seldom reported and only sporadic antemortem cases have been reported. We report an unusual case of malignant pericardial effusion with cardiac tamponade caused by metastatic adenocarcinoma of colon in a 58 year old patient and haemodynamic monitoring with lithium dilution cardiac output (LiDCO) method of measuring cardiac output due to prepare patient for surgery of subileus.

Effect of dantrolene premedication on various cardiovascular and biochemical variables and the recovery in healthy isoflurane-anesthetized horses.

To determine the effect of dantrolene premedication on various cardiovascular and biochemical variables and recovery in isoflurane-anesthetized horses. 6 healthy horses. Each horse was anesthetized twice with a 21- to 28-day washout period between anesthetic sessions. Food was not withheld from horses before either session. During each session, dantrolene (6 mg/kg in 2 L of water) or water (2 L) was administered via a nasogastric tube 1 hour before anesthesia was induced. Anesthesia was maintained with isoflurane for 90 minutes, during which blood gas analyses and lithium-dilution cardiac output (CO) measurements were obtained every 10 minutes. Serum creatine kinase activity was measured before and at 4, 8, and 12 hours after anesthesia. When horses were premedicated with dantrolene, CO at 25, 35, and 45 minutes after induction of anesthesia was significantly lower than that when horses were premedicated with water after which time difficulty in obtaining valid measurements suggested a continued decrease in CO; plasma potassium concentration progressively increased during anesthesia, whereas serum creatine kinase activity remained fairly stable and within reference limits through 12 hours after anesthesia; and 2 of 6 horses developed cardiac arrhythmias that required medical intervention. The quality of anesthetic recovery was slightly better when horses were premedicated with dantrolene versus water, although the time required for recovery did not differ significantly between treatments. Results suggested that dantrolene premedication prevented muscle damage without affecting anesthetic recovery but impaired CO and precipitated hyperkalemia and cardiac arrhythmias in healthy isoflurane-anesthetized horses.

Voltage changes in the lithium dilution cardiac output sensor after exposure to blood from horses given xylazine

BackgroundIn a previous in vitro study using saline medium, the authors showed that certain drugs changed the voltages of lithium dilution cardiac output (LiDCO) sensors and also influenced their accuracy in measuring lithium concentrations. These two parameters correlated and so we examined whether such drug–sensor interaction exists when LiDCO sensor was exposed to xylazine in blood. MethodsFive healthy adult warm-blood horses were injected with 0.5 mg kg−1 xylazine i.v. Physiological saline solution and venous blood were consecutively sampled through the same LiDCO sensor at 60, 45, 30, 15, and 0 min before and then 5, 15, 30, 45, and 60 min after xylazine injection. Sensor voltages were recorded and the differences between saline- and blood-exposed sensor voltages were compared at each time point. ResultsSaline-exposed sensor voltages continuously increased in a non-linear pattern during the experiment. Blood-exposed sensor voltages also increased in a similar pattern, but it was interrupted by an abrupt increase in voltage after xylazine injection. The differences between saline- and blood-exposed sensor voltages were 7 (6.1–8) mV [median (range)] before xylazine but decreased significantly at 5 and 15 min after xylazine treatment. The highest drug-induced voltage change was 3.4 (1.6–7) mV. ConclusionsThis study showed that exposure of a LiDCO sensor to blood after a single clinically relevant dose of xylazine in horses changed the voltages of the sensors for 15 min. Comparison of saline- and blood-exposed sensor voltages could become a tool to detect drug–sensor interactions.

The Cardiovascular Effects of Sevoflurane and Isoflurane After Premedication of Healthy Dogs Undergoing Elective Surgery

Sevoflurane and isoflurane are commonly used in veterinary anesthesia. The objective of this prospective, randomized, open-label clinical study was to compare the cardiovascular effects of sevoflurane and isoflurane via direct arterial blood pressure measurements and the lithium dilution cardiac output (LDCO) on premedicated healthy dogs undergoing elective tibial plateau leveling osteotomy (TPLO). Nineteen client-owned dogs were included. All dogs were premedicated with hydromorphone (0.05 mg/kg IV and glycopyrrolate 0.01 mg/kg subcutaneously). Ten dogs were anesthetized with sevoflurane and nine dogs were anesthetized with isoflurane. Eighteen dogs were instrumented with a dorsal pedal arterial catheter, and one dog had a femoral arterial catheter. All dogs had continuous, direct systolic (SAP), diastolic (DAP), and mean arterial (MAP) blood pressure readings as well as heart rate (HR), cardiac output (CO), cardiac index (CI), systemic vascular resistance (SVR), systemic vascular resistance index (SVRI), stroke volume variation (SVV), and pulse pressure variation (PPV) recorded q 5 min during the surgical procedure. There was no significant statistical difference in all parameters between the sevoflurane and isoflurane treatment groups. Both sevoflurane and isoflurane inhalant anesthetics appear to have similar hemodynamic effects when used as part of a multimodal anesthetic protocol in premedicated healthy dogs undergoing an elective surgical procedure.

Reliability of lithium dilution cardiac output in anaesthetized sheep

Cardiac output (CO) measurement with lithium dilution (COLD) has not been fully validated in sheep using precise ultrasonic flow probe technology (COUFP). Sheep generate important cardiovascular research models and the use of COLD has become more popular in experimental settings. Ultrasonic transit-time perivascular flow probes were surgically implanted on the pulmonary artery of 13 sheep. Paired COLD readings were taken at six time points, before and after implantation of a left ventricular assist device (LVAD) and compared with COUFP recorded just after lithium injection. The mean COLD was 5.7 litre min(-1) (range 3.8-9.6 litre min(-1)) and mean COUFP 5.9 litre min(-1) (range 4.0-9.2 litre min(-1)). The bias (standard deviation) was 0.3 (1.0) litre min(-1) [5.1 (16.9)%] and limits of agreement (LOA) were -1.7 to 2.3 litre min(-1) (-28.8 to 39.0%) with a percentage error (PE) of 34.4%. Data to assess trending [rate (95% confidence intervals)] included a 78 (62-93)% concordance rate in the four-quadrant plot (n=27). In the half moon polar plot (n=19), the mean polar angle was +5°, the radial LOA were -49 to +35° and 68 (47-89)% of data points fell within 22.5° of the mean polar angle. Both tests indicated moderate to poor trending ability. COLD is not precise when evaluated against COUFP in sheep based on the statistical criteria set, but the results are comparable with previously published animal studies.

Fluid Therapy LiDCO Controlled Trial—Optimization of Volume Resuscitation of Extensively Burned Patients through Noninvasive Continuous Real-Time Hemodynamic Monitoring LiDCO

This pilot trial aims at gaining support for the optimization of acute burn resuscitation through noninvasive continuous real-time hemodynamic monitoring using arterial pulse contour analysis. A group of 21 burned patients meeting preliminary criteria (age range 18-75 years with second- third- degree burns and TBSA ≥10-75%) was randomized during 2010. A hemodynamic monitoring through lithium dilution cardiac output was used in 10 randomized patients (LiDCO group), whereas those without LiDCO monitoring were defined as the control group. The modified Brooke/Parkland formula as a starting resuscitative formula, balanced crystalloids as the initial solutions, urine output of 0.5 ml/kg/hr as a crucial value of adequate intravascular filling were used in both groups. Additionally, the volume and vasopressor/inotropic support were based on dynamic preload parameters in the LiDCO group in the case of circulatory instability and oligouria. Statistical analysis was done using t-tests. Within the first 24 hours postburn, a significantly lower consumption of crystalloids was registered in LiDCO group (P = .04). The fluid balance under LiDCO control in combination with hourly diuresis contributed to reducing the cumulative fluid balance approximately by 10% compared with fluid management based on standard monitoring parameters. The amount of applied solutions in the LiDCO group got closer to Brooke formula whereas the urine output was at the same level in both groups (0.8 ml/kg/hr). The new finding in this study is that when a fluid resuscitation is based on the arterial waveform analysis, the initial fluid volume provided was significantly lower than that delivered on the basis of physician-directed fluid resuscitation (by urine output and mean arterial pressure).

Evaluation of the sedative and cardiovascular effects of intramuscular administration of dexmedetomidine with and without concurrent atropine administration in dogs

To evaluate degree of sedation and cardiovascular, respiratory, acid-base excess, and electrolyte variables in response to IM administration of dexmedetomidine or dexmedetomidine with atropine. Randomized crossover study. Animals-5 healthy 1- to 2-year-old sexually intact male Treeing Walker Coonhounds. Dogs were instrumented with catheters placed in the dorsal pedal artery and lateral saphenous vein. All dogs received dexmedetomidine (10 μg/kg [4.5 μg/lb], IM) or dexmedetomidine with atropine (0.02 mg/kg [0.009 mg/lb], IM). Variables were measured at baseline (time 0) and 5, 15, 30, and 60 minutes after drug administration. In all dogs, lithium dilution cardiac output decreased from a mean ± SD baseline value of 5.07 ± 1.0 L/min to 2.1 ± 0.9 L/min. Cardiac output was not different between dexmedetomidine group dogs and dexmedetomidine-atropine group dogs. Mean arterial pressure increased from baseline in both groups but was significantly higher in dexmedetomidine-atropine group dogs, compared with dexmedetomidine group dogs. Heart rate in dexmedetomidine group dogs decreased from 110 ± 14.2 beats/min to 49.4 ± 10.4 beats/min by 15 minutes. No differences were seen in blood gas values, electrolyte concentration, or hemoglobin values over time or between groups. Arrhythmias were detected in dexmedetomidine-atropine group dogs and included atrioventricular block, ventricular premature contractions, and ventricular bigeminy. Administration of atropine at 0.02 mg/kg, IM, with dexmedetomidine at 10 μg/kg, IM, resulted in an increase in mean arterial blood pressure and heart rate; deleterious cardiac arrhythmias were also observed. Use of atropine with dexmedetomidine is not recommended in dogs.

Statistical Modeling of Hemodynamic Changes During Orthotopic Liver Transplantation: Predictive Value for Outcome and Effect of Marginal Donors

Aim This study analyzed hemodynamic recordings collected on a beat-to-beat basis during orthotopic liver transplantation (OLT). The first aim was to construct a graphic that will represent hemodynamic profile during OLT. The second aim was to compare the intraoperative hemodynamic pattern of survivors versus nonsurvivors and those who received a liver from normal versus marginal donors. Methods Hemodynamic data (including cardiac output, cardiac index, stroke volume [SV] and SV index, systemic vascular resistance [SVR] and SVR index, mean arterial pressure, and heart rate) were collected from 100 consecutive adult OLT patients with the use of a lithium dilution cardiac output (LiDCO plus) monitor. A LOESS (Robust Locally Weighted Regression and Smoothing Scatterplots) smoother was used to give a more easily interpreted graph. Patients were grouped with respect to survival at 30 days (survivors vs nonsurvivors) and quality of graft (marginal vs normal). Results We constructed graphics that represented all intraopetarive hemodynamic data during OLT for 100 consecutive procedures. It confirmed hyperdynamic circulation during OLT. Statistical analysis did not reveal significant differences regarding intraoperative hemodynamic data between survivors and nonsurvivors, or between patients receiving normal versus marginal grafts. Conclusion This study shows changes in the hemodynamic profile during OLT, measured on a beat-to-beat basis. Intraoperative hemodynamic changes did not predict patients who did not survive OLT. Beat-to-beat monitoring did not reveal significant hemodynamic instability following transplantation of marginal grafts.

National survey of the use of cardiac output monitoring tool in general adult ICUs in the United Kingdom

Haemodynamic monitoring is essential for the management of critically ill patients. Currently there are various techniques available in clinical practice to measure cardiac output (CO) in ICUs including pulmonary artery catheter (PAC), oesophageal Doppler, lithium dilution cardiac output (LiDCO) and pulse-induced contour cardiac output (PiCCO) studies. In recent times PAC has been used less with less invasive methods becoming more popular. We conducted a telephone survey of the current CO monitoring practices in adult ICUs in the United Kingdom.

Reversal of Heparin by Novel Synthetic Antagonist PMX-60056 Exhibits a Linear Dose-Response Relationship

AbstractAbstract 3329PMX-60056 is a small-molecule first-in-class new chemical entity designed to bind to the pentasaccharide group in unfractionated heparin (UFH) and low-molecular-weight heparins (LMWH), and reverse their anticoagulation effects. It has been shown to reverse UFH and the LMWH tinzaparin to date, and without rebound anticoagulation.When no UFH or LMWH is present, PMX-60056 dosing has been limited by transient hypotension at doses over 0.4 mg/kg in volunteers, but its use for heparin reversal should eliminate this effect as PMX-60056 preferentially binds to heparin. A study with UFH at 70 U/kg and reversal with 0.3 mg/kg PMX-60056 showed full efficacy, and mild blood-pressure reductions in half the subjects that suggested excess PMX-60056.Therefore, we examined the dose-response, efficacy, and safety at higher doses of UFH as used in cardiac surgery. Hemodynamic effects were recorded with lithium-dilution cardiac output, and blood pressures were continuous intra-arterial measurements. PMX-60056 dose was titrated using activated clotting times (ACTs), and protamine requirements were also estimated by heparin-protamine titrations to determine heparin levels.350 U/kg of heparin was reversed in 6 normal volunteers, after an initial 10-minute infusion of 0.7 mg/kg PMX-60056 and subsequent smaller doses as needed to normalize ACT. Hemodynamics were unaffected until total PMX-60056 dose exceeded 1 mg/kg – the initial dose of 0.7 mg/kg never produced a change. When a hemodynamic effect did occur (in 3 of the 6), it was initiated by a fall in systemic vascular resistance. Only 1 of these 6 subjects had a clinically significant hypotension, which lasted 15 minutes with pressor agents and limb elevation; this subject was subsequently found to have a past history suggestive of vaso-vagal instability. The other 5 subjects had no appreciable change in blood pressure.Per protocol the antagonist doses were in discrete amounts, so some overshoot was inevitable. Therefore, the total dose of PMX-60056 to the point immediately preceding full reversal of ACT was correlated with ACT, with initial protamine requirement according to heparin levels, and with estimated residual heparin (calculated from dose given and time elapsed). These data were highly correlated with a straight line from zero: R-squared was 0.90 with initial ACT, 0.96 with initial protamine requirement according to heparin levels, and 0.97 with estimated residual heparin (calculated).These data suggest that measurements routinely available during cardiac surgery are sufficient for predicting a single reversing dose of PMX-60056 that will safely and effectively neutralize UFH-induced anticoagulation.After reversal, the ability to re-anticoagulate is sometimes important. The same study also established that reversal of anticoagulation with PMX-60056 did not inhibit subsequent repeat anticoagulation with heparin a few minutes later, which was then also reversed with PMX-60056.This study was conducted according to cGCP at Duke University's Anesthesiology Research Unit. More results will be forthcoming as the analysis proceeds. Disclosures:McAllister:PolyMedix, Inc.: Employment.

The hemodynamic effects of medetomidine continuous rate infusions in the dog

ObjectiveTo characterize the hemodynamic effects of continuous rate infusions (CRI) of medetomidine administered at doses ranging from 0 to 3 μg kg−1 hour−1. Study designProspective, blinded, randomized experimental trial. AnimalsSix adult purpose-bred mongrel dogs. MethodsAnesthesia was induced with sevoflurane for placement of arterial and venous catheters. Dogs recovered from anesthesia after which baseline hemodynamic measurements were obtained via lithium dilution cardiac output (CO) determination, with subsequent measurements via pulse power analysis to provide continuous CO determinations. Medetomidine, 1, 2, or 3 μg kg−1 hour−1 or a volume equivalent placebo, was administered via CRI for 60 minutes. Systolic, mean, and diastolic arterial pressure, heart rate (HR), CO and stroke volume were measured and stroke index (SI), cardiac index (CI), total peripheral resistance (TPR), and total peripheral resistance index (TPRI) were calculated at 3, 7, 10, 20, 30, 45, 60, 90, and 120 minutes from the start of the infusion. ResultsIncrease in dose decreased SI by 25%, 19%, and 30%, HR by 33%, 57%, and 60%, CI by 50%, 65%, 70% and increased TPRI by 109%, 235%, and 222% from baseline to the 60-minute measurement for the 1, 2, and 3 μg kg−1 hour−1 doses, respectively. HR, TPRI, and CI all showed significant differences over the duration of the study from the placebo treatment. ConclusionsMedetomidine CRI produces clinically relevant changes in CO, TPR, and HR. The demonstrated decrease in CO is largely because of bradycardia and the degree of cardiovascular depression appears to be dose-dependent. These findings are consistent with previously described hemodynamic changes with single bolus administration of medetomidine. Clinical relevanceLow-dose medetomidine CRIs produce clinically relevant hemodynamic depression at doses as low as 1 μg kg−1 hour−1 and should be used cautiously in dogs.

A hybrid hierarchical decision support system for cardiac surgical intensive care patients. Part II. Clinical implementation and evaluation

Patients emerging from cardiac surgery can display varying degrees of cardiovascular instability arising from potentially complex, multi-factorial and interlinked causes. Stabilization and control of the cardiovascular system are currently managed by healthcare experts using experiential knowledge, and, in some centers, manually inputted decision pathway algorithms. This paper describes a clinical trial undertaken to determine the basic functioning of a clinical decision support system (CDSS) designed and constructed by the authors to facilitate the control of the major cardiovascular components in the early post-operative phase. Part II follows Part I's description of the software and simulation testing of the CDSS, and describes the hardware setup of a patient monitoring and CDSS. The system is evaluated on three post-cardiac surgery intensive care patients whom had all undergone cardio-pulmonary bypass. The study was approved by the Sheffield Teaching Hospitals National Health Service (NHS) Foundation Trust Research Ethics Committee and conducted at the North Trent cardio-thoracic surgical unit and cardiac intensive care unit (CICU), Northern General Hospital, Sheffield (UK). Patients considered as 'very likely' to require active intervention to support the cardiovascular function following routine cardiac surgery were recruited during pre-operative surgical and anesthetic assessment, giving written informed consent when admitted for their operation. These patients underwent routine induction and maintenance of anesthesia by a non-study consultant anesthetist and the operation performed. There were no restrictions placed on the types of invasive monitoring used, on the use of trans-oesophageal echocardiography, drug selection, or the anesthetic agents selected by the clinicians performing the operations. All patients had full, routine invasive and non-invasive monitoring applied, including electrocardiography, central venous and peripheral arterial catheterisation, urine outputs and central temperature. After chest closure the patients were transferred to the CICU, sedated and ventilated, and the study commenced by the study anesthetist (1st author). The patients were in a clinically stable condition when admitted to the unit, and were attended by the treating clinicians until the handover to the study anesthetist occurred. The LiDCOplus (lithium dilution cardiac output) monitor (LiDCO Limited, Flowers Building, Granta Park, Cambridge CB1 6GU, United Kingdom) was calibrated after attachment to the patient's arterial line, and the patient's beat-to-beat hemodynamic data transferred to the host laptop computer. The CDSS graphical interface displays the patient's clinical details and specific cardiovascular data and prompts the anesthetist to input the target ranges for each parameter, and select a suitable advisor frequency. This is the frequency with which the therapeutic advice is displayed on screen with an audible prompt for a control inputs from the anesthetist. In each case this was selected to be 30s. When the study anesthetist agreed with the CDSS advice (administration of fluid, commencing a drug, altering the drug infusion rate) the syringe motif on the "Advisor Infusion Rates" panel of the graphical interface was 'clicked' on and the infusion rate immediately and manually inputted to Graseby 3400 pumps. If any disagreement between the anesthetist and the computer's advice arose, the syringe motif on the "Expert Infusion Rates" panel of the preferred drug was 'clicked' on and the expert's therapeutic decision (e.g. infusion rate) was entered in the corresponding data field and then applied to the pump. During all trials, data was stored for off-line analysis. The CDSS successfully selected suitable drug therapies for each case and advised reasonable and appropriate infusion rates such that the study anesthetist did not have to override the suggested CDSS instructions and infusion rates. Under differing clinical conditions the system was able to maintain clinically appropriate and stable control of the cardiovascular system (CVS), with good profiles under noisy physiological measurements, and was readily able to regain control following transient deterioration of the patient hemodynamic parameters (coughing, or during blood sampling).

Lithium dilution cardiac output measurement in the critically ill patient: determination of precision of the technique

Lithium dilution cardiac output by LiDCOplus (LiDCO, Cambridge, UK) is a validated methodology for measuring cardiac output. It is used to calibrate a pulse pressure analysis algorithm (PulseCO) for the continuous measurement of subsequent changes in this variable. The variability of measurements, or precision, within patients of lithium dilution cardiac output has not previously been described. Thirty-five hemodynamically stable patients in intensive care, with no significant variability in heart rate, mean arterial pressure or central venous pressure, were recruited. Fifty-three determinations of cardiac output were made, each using four lithium dilution measurement curves performed consecutively within a maximum period of 10 min. The coefficient of variation of the measurements was determined and used to derive the least significant change in cardiac output that this technique could reliably detect. For a single measurement, the coefficient of variation was 8%. This equates to the technique being able to detect a change (least significant change) between two measurements of 24%. Averaging two lithium dilution measurements improved the coefficient of variation to 6% with a least significant change of 17%. Using the average of three curves reduced the coefficient of variation to 5% with a least significant change of 14%. To achieve a good precision with this technique, three lithium dilution measurements should be averaged. This will allow changes in cardiac output of more than 14% to be reliably detected. The understanding of the precision of this technique allows the user to know when a real change has happened to their patient.

Lithium dilution cardiac output and oxygen delivery in conscious dogs with systemic inflammatory response syndrome

AbstractObjective: Compare cardiac index (CI) and oxygen delivery index (DO2I) in conscious, critically ill dogs to control dogs; evaluate the association of CI and DO2I with outcome.Design: Prospective non‐randomized clinical study.Setting: Veterinary teaching hospital.Animals: Eighteen client‐owned dogs with systemic inflammatory response syndrome (SIRS) and 8 healthy control dogs.Measurements and Main Results: CI of dogs with SIRS was measured using lithium dilution at times 0, 4, 8, 16, and 24 hours. Data collected included physical exam, arterial blood gas (ABG) and hemoximetry. CI of control dogs was measured 3 times with 1 measurement of ABG. Mean CI ± SE in SIRS patients was 3.32 ± 0.95 L/min/m2; lower than controls at 4.18 ± 0.22 L/min/m2 (P&lt;0.001). Mean DO2I ± SE in SIRS patients was 412.91 ± 156.67 mL O2/min/m2; lower than controls at 785.24 ± 45.99 mL O2/min/m2 (P&lt;0.001). There was no difference in CI (P=0.49) or DO2I (P=0.51) for dogs that survived to discharge versus those that did not. There was no difference in mean CI (P=0.97) or DO2I (P=0.50) of survivors versus non‐survivors for 28‐day survival. Survivors had lower blood glucose (P=0.03) and serum lactate concentrations (P=0.04) than non‐survivors.Conclusions: CI and DO2I in conscious dogs with SIRS were lower than control dogs, which differs from theories that dogs with SIRS are in a high cardiac output state. CI and DO2I were not significantly different between survivors and non‐survivors. Similar to previous studies, lactate and glucose concentrations of survivors were lower than non‐survivors.