Early weight measures and long-term neuropsychological outcome of critically ill neonates and infants: a secondary analysis of the PEPaNIC trial.

Neonates and infants surviving critical illness show impaired growth during critical illness and are at risk for later neuropsychological impairments. Early identification of individuals most at risk is needed to provide tailored long-term follow-up and care. The research question is whether early growth during hospitalization is associated with growth and neuropsychological outcomes in neonates and infants after pediatric intensive care unit admission (PICU). This is a secondary analysis of the PEPaNIC trial. Weight measurements upon PICU admission, at PICU discharge, at hospital discharge, at 2- and 4-year follow-up, and of different subgroups were compared using (paired) t-tests. Multiple linear regression analyses were performed to investigate the association between early growth in weight measures and neuropsychological outcomes at 4-year follow-up. One hundred twenty-one infants were included, and median age upon admission was 21 days. Growth in weight per week was less than the age-appropriate norm, resulting in a decrease in weight-for-age Z-score during hospitalization. Weight is normalized at 2- and 4-year follow-up. Weight gain in kilograms per week and change in weight Z-score were not associated with neurodevelopmental outcome measures at 4-year follow-up. Lower weight-for-age Z-score at PICU admission and at hospital discharge was associated only with lower weight and height Z-scores at 4-year follow-up. CONCLUSION: Growth in weight during hospital stay of young survivors of critical illness is impaired. Worse early growth in weight is associated with lower weight and height but not with neuropsychological outcomes at 4-year follow-up. WHAT IS KNOWN: • Critically ill neonates and infants show impaired early growth during admission and are at risk for later neuropsychological impairments. • Unraveling the association between early growth and later neuropsychological impairments is crucial since the first year of life is critical for brain development. WHAT IS NEW: • Critically ill neonates and infants had age appropriate weight measures at 4-year follow-up. • Poor growth in weight during hospital stay was not associated with poorer cognitive, emotional, or behavioral functioning four years after critical illness.

Early hypophosphatemia in critically ill children and the effect of parenteral nutrition: A secondary analysis of the PEPaNIC RCT.

BACKGROUND & AIMS: Hypophosphatemia during critical illness has been associated with adverse outcome. The reintroduction of enteral or parenteral nutrition, leading to refeeding hypophosphatemia (RFH), has been presented as potential risk factor. We investigated the occurrence of early RFH, its association with clinical outcome, and the impact of early parenteral nutrition (PN) on the development of early RFH in pediatric critical illness. METHODS: This is a secondary analysis of the PEPaNIC randomized controlled trial (N = 1440), which showed that withholding supplemental parenteral nutrition (PN) for 1 week (late-PN) in the pediatric intensive care unit (PICU) accelerated recovery and reduced new infections compared to early-PN (<24 h). Patients with renal replacement therapy or unavailable phosphate concentrations were excluded from this analysis. Early RFH was defined as serum/plasma phosphate <0.65 mmol/L and a drop of >0.16 mmol/L within 3 days of admission to the PICU. The association between baseline characteristics and early RFH, and the association of early RFH with clinical outcome were investigated using logistic and linear regression models, both uncorrected and corrected for possible confounders. To examine the impact of nutritional intake on phosphate concentrations, structural nested mean models with propensity score and censoring models were used. RESULTS: A total of 1247 patients were eligible (618 early-PN, 629 late-PN). Early RFH occurred in 40 patients (3%) in total, significantly more in the early-PN group (n = 31, within-group occurrence 5%) than in the late-PN-group (n = 9, within-group occurrence 1%, p < 0.001). Patients who were older (OR 1.14 (95% CI 1.08; 1.21) per year added, p < 0.001) and who had a higher Pediatric Risk of Mortality (PIM3) score had a higher risk of developing early RFH (OR 1.36 (95% CI 1.15; 1.59) per unit added, p < 0.001), whereas patients in the late-PN group had a lower risk of early RFH (OR 0.24 (95% CI 0.10; 0.49), p < 0.001). Early RFH was significantly associated with a 56% longer PICU stay (p = 0.003) and 42% longer hospital stay (p = 0.007), but not with new infections (OR 2.01 (95% CI 0.90; 4.30), p = 0.08) or length of mechanical ventilatory support (OR 1.05 (95% CI -3.92; 6.03), p = 0.68), when adjusted for possible confounders. Increase of parenteral nutrition intake (in % kcal of predicted resting energy expenditure) decreased phosphate concentrations (c = -0.002 (95% CI -0.002; -0.001). CONCLUSIONS: Early RFH occurred in 3% of critically ill children. Patients randomized to late-PN had a lower chance of developing early RFH, which may be explained by the more gradual build-up of nutrition. As early RFH might impact recovery, it is important to closely monitor phosphate concentrations in patients, especially of those at risk for early RFH.

Technical failure of the EZ-blocker™ causing serious adverse events during one lung ventilation: a case series.

We present a case series of intra-operative adverse events while using a specific type of bronchial blocker, designed to facilitate device positioning and minimise the risk of dislocation. The Rüsch® EZ-blocker™ (Teleflex Life Sciences Ltd., Athlone, Ireland) is a Y-shaped catheter equipped with two separately inflatable cuffs at the tip - one for each bronchial lumen. In this report, we describe four cases where the use of the EZ-blocker was associated with the development of high airway pressures, hypoxaemia and expansion of the non-dependent lung. Bronchoscopic evaluation showed spontaneous inflation of the cuff within the dependent (i.e. ventilated) bronchus, causing bronchial obstruction, and volume loss of the cuff within the non-dependent (i.e. unventilated) bronchus, causing unintended expansion of the non-dependent lung. After removal of the bronchial blocker, the catheter showed no visible defect, but a bench test revealed a functional connection inside the catheter which allowed air to pass slowly from one bronchial cuff to the other. This technical defect relates to the unique design of the EZ-blocker as it is the only bronchial blocker equipped with two bronchial cuffs. Clinicians should be aware of this inherent risk since complications may develop insidiously and affect both lungs simultaneously. Early recognition and prompt intervention can prevent life-threatening intra-operative deterioration.

The accuracy of gap and step-off measurements in acetabular fracture treatment.

The assessment of gaps and steps in acetabular fractures is challenging. Data from various imaging techniques to enable accurate quantification of acetabular fracture displacement are limited. The aim of this study was to assess the accuracy of pelvic radiographs, intraoperative fluoroscopy, and computed tomography (CT) in detecting gaps and step-offs in acetabular fractures. Sixty patients, surgically treated for acetabular fractures, were included. Five observers (5400 measurements) measured the gaps and step-offs on radiographs and CT scans. Intraoperative fluoroscopy images were reassessed for the presence of gaps and/or step-offs. Preoperatively, 25% of the gaps and 40% of the step-offs were undetected on radiographs compared to CT. Postoperatively, 52% of the gaps and 80% of the step-offs were missed on radiographs compared to CT. Radiograph analysis led to a significantly smaller gap and step-off compared to the CT measurements, an underestimation by a factor of two. Approximately 70% of the residual gaps and step-offs was not detected using intraoperative fluoroscopy. Gaps and step-offs that exceed the critical cut-off indicating worse prognosis often remained undetected on radiographs compared to CT scans. Less-experienced observers tend to overestimate gaps and step-offs compared to the more-experienced observers. In acetabular fracture treatment, gaps and step-offs were often undetected and underestimated on radiographs and intraoperative fluoroscopy in comparison with CT scans. This means that CT is superior to radiographs in detecting acetabular fracture displacement, which is clinically relevant for patient counselling regarding treatment decisions and prognosis.

Human adult cardiac autonomic innervation: Controversies in anatomical knowledge and relevance for cardiac neuromodulation.

BACKGROUND: Cardiac sympathetic blockade is a therapeutic approach for arrhythmias and heart failure and may be a beneficial effect of high thoracic epidural anesthesia. These treatments require detailed knowledge of the spatial location and distribution of cardiac autonomic nerves, however, there are controversies on this subject in humans. OBJECTIVE: To provide a systematic overview of current knowledge on human anatomy of the cardiac autonomic nervous system. RESULTS: In contrast to the often claimed assumption that human preganglionic sympathetic cardiac neurons originate mainly from thoracic spinal segments T1-T4 or T5, there is ample evidence indicating involvement of cervical spinal segment C8 and thoracic spinal segments below T5. Whether cervical ganglia besides the stellate ganglion play a role in transmission of cardiac sympathetic signals is unclear. Similarly, there is debate on the origin of cardiac nerves from different thoracic ganglia. Most human studies report thoracic cardiac nerves emerging from the first to fourth thoracic paravertebral ganglia; others report contributions from the fifth, sixth and even the seventh thoracic ganglia. There is no agreement on the precise composition of nerve plexuses at the cardiac level. After years of debate, it is generally accepted that the vagal nerve contributes to ventricular innervation. Vagal distribution appears higher in atria, whereas adrenergic fibers exceed the number of vagal fibers in the ventricles. CONCLUSION: Anatomy of the human cardiac autonomic nervous system is highly variable and likely extends beyond generally assumed boundaries. This information is relevant for thoracic epidural anesthesia and procedures targeting neuronal modulation of cardiac sympathetic innervation.

Impact of supplemental parenteral nutrition early during critical illness on invasive fungal infections: a secondary analysis of the EPaNIC randomized controlled trial.

OBJECTIVE: In the EPaNIC RCT (N=4640), postponing the administration of parenteral nutrition (PN) to beyond 1 week in the intensive care unit (ICU) (late-PN) reduced the number of ICU-acquired infections and the costs for antimicrobial drugs compared with initiation of PN within 24-48 hours of admission (early-PN). In a secondary analysis, we hypothesize that late-PN reduces the odds to acquire an invasive fungal infection (IFI) in the ICU. METHODS: The impact of late-PN (N=2328) versus early-PN (N=2312) on acquired IFI and on the likelihood to acquire an IFI over time was assessed in univariable and multivariable analyses. Subsequently, we performed multivariable analyses to assess the effect of the mean total daily administered calories from admission until day 3, day 5, and day 7 on the likelihood over time of acquiring an IFI. RESULTS: Fewer late-PN patients acquired an IFI compared with early-PN patients (77/2328 versus 112/2312) (p 0.008). After adjusting for risk factors, the odds to acquire an IFI and the likelihood of acquiring an IFI at any time were lower in late-PN (adjusted odds ratio 0.66, 95% CI 0.48-0.90, p 0.009; adjusted hazard ratio (HRadj) 0.70, 95% CI 0.52-0.93, p 0.02). Larger caloric amounts from admission until day 7 were associated with a higher likelihood to acquire an IFI over time (HRadj 1.09, 95% CI 1.02-1.16, p 0.009). CONCLUSION: Postponing PN to beyond 1 week and smaller caloric amounts until day 7 in the ICU reduced ICU-acquired IFIs and the likelihood to develop an IFI over time.

Association of preoperative anaemia with postoperative morbidity and mortality: an observational cohort study in low-, middle-, and high-income countries.

BACKGROUND: Anaemia is associated with poor postoperative outcomes, but few studies have described the impact of preoperative anaemia in low- and middle- (LMICs), and high-income countries (HICs). METHODS: This was a planned analysis of data collected during an international 7 day cohort study of adults undergoing elective inpatient surgery. The primary outcome was in-hospital death, and the secondary outcomes were in-hospital complications. Anaemia was defined as haemoglobin <12 g dl-1 for females and <13 g dl-1 for males. Hierarchical three-level mixed-effect logistic regression models were constructed to examine the associations between preoperative anaemia and outcomes. RESULTS: We included 38 770 patients from 474 hospitals in 27 countries of whom 11 675 (30.1%) were anaemic. Of these, 6886 (17.8%) patients suffered a complication and 198 (0.5%) died. Patients from LMICs were younger with lower ASA physical status scores, but a similar prevalence of anaemia [LMIC: 5072 (32.5%) of 15 585 vs HIC: 6603 (28.5%) of 23 185]. Patients with moderate [odds ratio (OR): 2.70; 95% confidence interval (CI): 1.88-3.87] and severe anaemia (OR: 4.09; 95% CI: 1.90-8.81) were at an increased risk of death in both HIC and LMICs. Complication rates increased with the severity of anaemia. Compared with patients in LMICs, those in HICs experienced fewer complications after an interaction term analysis [LMIC (OR: 0.92; 95% CI: 0.87-0.97) vs HIC (OR: 0.86; 95% CI: 0.84-0.87); P<0.01]. CONCLUSIONS: One-third of patients undergoing elective surgery are anaemic. These patients have an increased risk of complications and death. The prevalence of anaemia is similar amongst patients in LMICs despite their younger age and lower risk profile. CLINICAL TRIAL REGISTRATION: ISRCTN51817007.

Determination of the median effective dose (ED50 ) of spinal chloroprocaine in labour analgesia.

The primary goal of this study was to determine the median effective dose (ED50 ) of spinal chloroprocaine for labour analgesia. Thirty-eight parturients requesting neuraxial analgesia were enrolled. Doses of 1% chloroprocaine were determined by the technique of up-down sequential allocation, with an initial dose of 20 mg and steps of 2 mg. The chloroprocaine spinal dose was given as the spinal component of a combined spinal-epidural, which was then supplemented with an epidural dose of 7.5 µg sufentanil in 7 ml saline. Effective analgesia was defined as a score ≤ 10 mm within 15 min on a 100-mm visual analogue pain scale. Using the isotonic regression estimator method, the ED50 of chloroprocaine for the spinal component of a combined spinal-epidural for labour was calculated to be median (95%CI) 12.0 (9.3-17.0) mg.

In-vivo validation of a new clinical tool to quantify three-dimensional myocardial strain using ultrasound.

Three-dimensional (3D) strain analysis based on real-time 3-D echocardiography (RT3DE) has emerged as a novel technique to quantify regional myocardial function. The goal of this study was to evaluate accuracy of a novel model-based 3D tracking tool (eSie Volume Mechanics, Siemens Ultrasound, Mountain View, CA, USA) using sonomicrometry as an independent measure of cardiac deformation. Thirteen sheep were instrumented with microcrystals sutured to the epi- and endocardium of the inferolateral left ventricular wall to trace myocardial deformation along its three directional axes of motion. Paired acquisitions of RT3DE and sonomicrometry were made at baseline, during inotropic modulation and during myocardial ischemia. Accuracy of 3D strain measurements was quantified and expressed as level of agreement with sonomicrometry using linear regression and Bland-Altman analysis. Correlations between 3D strain analysis and sonomicrometry were good for longitudinal and circumferential strain components (r = 0.78 and r = 0.71) but poor for radial strain (r = 0.30). Accordingly, agreement (bias ± 2SD) was -5 ± 6 % for longitudinal, -5 ± 7 % for circumferential, and 15 ± 19 % for radial strain. Intra-observer variability was low for all components (intra-class correlation coefficients (ICC) of respectively 0.89, 0.88 and 0.95) while inter-observer variability was higher, in particular for radial strain (ICC = 0.41). The present study shows that 3D strain analysis provided good estimates of circumferential and longitudinal strain, while estimates of radial strain were less accurate between observers.

Influence of variations in systemic blood flow and pressure on cerebral and systemic oxygen saturation in cardiopulmonary bypass patients.

BACKGROUND: Although both pressure and flow are considered important determinants of regional organ perfusion, the relative importance of each is less established. The aim of the present study was to evaluate the impact of variations in flow, pressure, or both on cerebral and whole-body oxygen saturation. METHODS: Thirty-four consenting patients undergoing elective cardiac surgery on cardiopulmonary bypass were included. Using a randomized cross-over design, four different haemodynamic states were simulated: (i) 20% flow decrease, (ii) 20% flow decrease with phenylephrine to restore baseline pressure, (iii) 20% pressure decrease with sodium nitroprusside (SNP) under baseline flow, and (iv) increased flow with baseline pressure. The effect of these changes was evaluated on cerebral (Sc(O2)) and systemic (Sv(O2)) oxygen saturation, and on systemic oxygen extraction ratio (OER). Data were assessed by within- and between-group comparisons. RESULTS: Decrease in flow was associated with a decrease in [from 63.5 (7.4) to 62.0 (8.5) %, P<0.001]. When arterial pressure was restored with phenylephrine during low flow, Sc(O2) further decreased from 61.0 (9.7) to 59.2 (10.2) %, P<0.001. Increase in flow was associated with an increase in Sc(O2) from 62.6 (7.7) to 63.6 (8.9) %, P=0.03, while decreases in pressure with the use of SNP did not affect Sc(O2). Sv(O2) was significantly lower (P<0.001) and OER was significantly higher (P<0.001) in the low flow arms. CONCLUSIONS: In the present elective cardiac surgery population, Sc(O2) and Sv(O2) were significantly lower with lower flow, regardless of systemic arterial pressure. Moreover, phenylephrine administration was associated with a reduced cerebral and systemic oxygen saturation.

Milrinone and levosimendan during porcine myocardial ischemia -- no effects on calcium overload and metabolism.

BACKGROUND: Although inotropic stimulation is considered harmful in the presence of myocardial ischaemia, both calcium sensitisers and phosphodiesterase inhibitors may offer cardioprotection. We hypothesise that these cardioprotective effects are related to an acute alteration of myocardial metabolism. We studied in vivo effects of milrinone and levosimendan on calcium overload and ischaemic markers using left ventricular microdialysis in pigs with acute myocardial ischaemia. METHODS: Anaesthetised juvenile pigs, average weight 36 kg, were randomised to one of three intravenous treatment groups: milrinone 50 µg/kg bolus plus infusion 0.5 µg/kg/min (n = 7), levosimendan 24 µg/kg plus infusion 0.2 µg/kg/min (n = 7), or placebo (n = 6) for 60 min prior to and during a 45 min acute regional coronary occlusion. Systemic and myocardial haemodynamics were assessed, and microdialysis was performed with catheters positioned in the left ventricular wall. (45) Ca(2+) was included in the microperfusate in order to assess local calcium uptake into myocardial cells. The microdialysate was analysed for glucose, lactate, pyruvate, glycerol, and for (45) Ca(2+) recovery. RESULTS: During ischaemia, there were no differences in microdialysate-measured parameters between control animals and milrinone- or levosimendan-treated groups. In the pre-ischaemic period, arterial blood pressure decreased in all groups while myocardial oxygen consumption remained stable. CONCLUSIONS: These findings reject the hypothesis of an immediate energy-conserving effect of milrinone and levosimendan during acute myocardial ischaemia. On the other hand, the data show that inotropic support with milrinone and levosimendan does not worsen the metabolic parameters that were measured in the ischaemic myocardium.

Relation between mixed venous oxygen saturation and cerebral oxygen saturation measured by absolute and relative near-infrared spectroscopy during off-pump coronary artery bypass grafting.

BACKGROUND: We hypothesized that previously reported contradictory results regarding the equivalence of mixed venous (Smv(O(2))) and cerebral (rS(c)O(2)) oxygen saturation might be related to time delay issues and to measurement technology. In order to explore these two factors, we designed a prospective clinical study comparing with relative (INVOS(®)) and absolute (Foresight(®)) rS(c)O(2) measurements. METHODS: Forty-two consenting patients undergoing elective off-pump coronary artery bypass grafting were included. Two INVOS and two Foresight sensors continuously registered rS(c)O(2). Smv(O(2)) was measured continuously via a pulmonary artery catheter. Data were assessed by within- and between-group comparisons and correlation analysis. RESULTS: A similar time delay of 19 (4) and 18 (4) s was found for compared with rS(c)O(2) measurements by Foresight and INVOS, respectively, during haemodynamic changes. After adjusting for this time delay, the correlation between Smv(O(2)) and rS(c)O(2) increased from r=0.25 to 0.75 (P<0.001) for Foresight, and from r=0.28 to 0.73 (P<0.001) for INVOS. Comparison of Foresight and INVOS revealed significant differences in absolute rS(c)O(2) values (range 58-89% for Foresight and 28-95% for INVOS). Changes in rS(c)O(2) in response to acute haemodynamic alterations were significantly more pronounced with INVOS compared with Foresight (P<0.001). CONCLUSIONS: Considering the important time delay with Smv(O(2)), rS(c)O(2) seems to reflect more appropriately acute haemodynamic alterations. This might suggest its use as a valid alternative to invasive monitoring of tissue oxygen saturation. Relative and absolute rS(c)O(2) measurements demonstrated significant differences in measured rS(c)O(2) values and in the magnitude of rS(c)O(2) changes during haemodynamic alterations.

Endotracheal intubation using videolaryngoscopy causes less cardiovascular response compared to classic direct laryngoscopy, in cardiac patients according a standard hospital protocol.

INTRODUCTION: Previous studies comparing Glidescope and classic direct laryngoscopy did not show an attenuation of CV responses to endotracheal intubation. In the present study, we hypothesize that indirect videolaryngoscopy can attenuate cardiovascular responses to endotracheal intubation. METHODS: In a randomized cross-over study, eighty adults (ASA PS II-III) were included. Both direct and indirect videolaryngoscopies were used in a random order, in the same patient. Cardiovascular responses to intubation were recorded as a relative change in rate pressure product (RPP = systolic blood pressure times heart rate) from baseline values. A linear mixed model was used to study the association between the outcome variable RPP and the type of laryngoscope used. RESULTS: The relative increase of the RPP at intubation was significantly smaller (i.e. 27%, P < 0.001) using videolaryngoscopy compared to the classic direct laryngoscopy. Cardiovascular responses were blunted by an additional 10.2% (P = 0.029), when the patient was on beta blockade. CONCLUSIONS: Our study shows less hemodynamic responses during endotracheal intubation using indirect videolaryngoscopy compared to classic direct laryngoscopy.

Anaphylactic shock and hyperfibrinolysis measured with thromboelastography.

This case report presents anaphylactic shock in which hyperfibrinolysis was diagnosed with Thromboelastography (TEG). A 45 year old female patient was scheduled for vacuum-assisted wound closure. At induction, she developed an anaphylactic shock that stabilized after standard treatment. TEG analysis revealed hyperfibrinolysis. Surgery was delayed and there were no signs of spontaneous bleeding. A repeat TEG analysis performed 30 minutes later showed a completely normalized coagulation pattern. Few reports have documented the association between anaphylactic shock and hyperfibrinolysis. This case illustrates the transient and short-lived nature of the phenomenon. The mechanisms and potential consequences are discussed.

Prospective evaluation of intraoperative hemodynamics in liver transplantation with whole, partial and DCD grafts.

The interaction of systemic hemodynamics with hepatic flows at the time of liver transplantation (LT) has not been studied in a prospective uniform way for different types of grafts. We prospectively evaluated intraoperative hemodynamics of 103 whole and partial LT. Liver graft hemodynamics were measured using the ultrasound transit time method to obtain portal (PVF) and arterial (HAF) hepatic flow. Measurements were recorded on the native liver, the portocaval shunt, following reperfusion and after biliary anastomosis. After LT HAF and PVF do not immediately return to normal values. Increased PVF was observed after graft implantation. Living donor LT showed the highest compliance to portal hyperperfusion. The amount of liver perfusion seemed to be related to the quality of the graft. A positive correlation for HAF, PVF and total hepatic blood flow with cardiac output was found (p = 0.001). Portal hypertension, macrosteatosis >30%, warm ischemia time and cardiac output, independently influence the hepatic flows. These results highlight the role of systemic hemodynamic management in LT to optimize hepatic perfusion, particularly in LDLT and split LT, where the highest flows were registered.

Anesthesia and perioperative management for a patient with Ullrich syndrome undergoing surgery for scoliosis.

Ullrich syndrome is a rare congenital hypotonic-sclerotic muscular disorder in which affected children develop a slowly progressive scoliosis and contractures and limpness of joints. The disease causes increasingly invalidating contractures and hardening of the muscles of the neck and trunk. While this neuromuscular type of scoliosis is progressive, patients rarely attain the point of surgery due to their compromised general medical condition. This may explain the current lack of outcome data and the paucity of information on perioperative management for patients with Ullrich syndrome undergoing major surgery. The purpose of this report was therefore to describe our first experience with the perioperative and anesthetic management of a 15-year-old boy presenting with Ullrich syndrome and a secondary invalidating scoliosis. The specific challenges of this condition characterized by severe restrictive lung disease and a challenging airway abnormality are discussed.

Recommendations for reporting perioperative transoesophageal echo studies.

Every perioperative transoesophageal echo (TEE) study should generate a written report. A verbal report may be given at the time of the study. Important findings must be included in the written report. Where the perioperative TEE findings are new, or have led to a change in operative surgery, postoperative care or in prognosis, it is essential that this information should be reported in writing and available as soon as possible after surgery. The ultrasound technology and methodology used to assess valve pathology, ventricular performance and any other derived information should be included to support any conclusions. This is particularly important in the case of new or unexpected findings. Particular attention should be attached to the echo findings following the completion of surgery. Every written report should include a written conclusion, which should be comprehensible to physicians who are not experts in echocardiography.

The value of pulse pressure and stroke volume variation as predictors of fluid responsiveness during open chest surgery.

SUMMARY: We investigated the ability of pulse pressure variation and stroke volume variation to predict fluid responsiveness during mechanical ventilation in patients undergoing open chest surgery by comparing their respective correlations with cardiac output changes induced by leg elevation. Serial leg elevation manoeuvres were performed before and after sternotomy in 15 patients scheduled for elective off-pump coronary bypass surgery. Under closed chest conditions, both pulse pressure variation and stroke volume variation correlated well with the induced cardiac output changes (r = 0.856, p = 0.002 and r = 0.897, p = 0.0012, respectively). These correlations were lost for both parameters following sternotomy. Our data show that pulse pressure variation and stroke volume variation are valid predictors of fluid responsiveness under closed chest conditions but that this property no longer holds when the chest is open.

Gravity is an important determinant of oxygenation during one-lung ventilation.

BACKGROUND: The role of gravity in the redistribution of pulmonary blood flow during one-lung ventilation (OLV) has been questioned recently. To address this controversial but clinically important issue, we used an experimental approach that allowed us to differentiate the effects of gravity from the effects of hypoxic pulmonary vasoconstriction (HPV) on arterial oxygenation during OLV in patients scheduled for thoracic surgery. METHODS: Forty patients with chronic obstructive pulmonary disease scheduled for right lung tumour resection were randomized to undergo dependent (left) one-lung ventilation (D-OLV; n=20) or non-dependent (right) one-lung ventilation (ND-OLV; n=20) in the supine and left lateral positions. Partial pressure of arterial oxygen (PaO2) was measured as a surrogate for ventilation/perfusion matching. Patients were studied before surgery under closed chest conditions. RESULTS: When compared with bilateral lung ventilation, both D-OLV and ND-OLV caused a significant and equal decrease in PaO(2) in the supine position. However, D-OLV in the lateral position was associated with a higher PaO2 as compared with the supine position [274.2 (77.6) vs. 181.9 (68.3) mmHg, P<0.01, analysis of variance (ANOVA)]. In contrast, in patients undergoing ND-OLV, PaO2 was always lower in the lateral as compared with the supine position [105.3 (63.2) vs. 187 (63.1) mmHg, P<0.01, ANOVA]. CONCLUSION: The relative position of the ventilated vs. the non-ventilated lung markedly affects arterial oxygenation during OLV. These data suggest that gravity affects ventilation-perfusion matching independent of HPV.

Near-infrared spectroscopy (NIRS) monitoring in contemporary anesthesia and critical care.

Near-infrared spectroscopy (NIRS) is a noninvasive technology that continuously monitors regional tissue oxygenation. Originally used for assessment of oxygen saturation of the brain, its use has now been expanded to evaluation of oxygenation of tissues other than the brain. There is also growing evidence for the larger applicability of NIRS as an estimate of systemic venous saturation in correspondence with the adequacy of the circulatory status. New and promising advances may further this technology to become part of our standard armamentarium, in order to optimize patient care in daily anesthesia practice. The present paper briefly reviews the basic principles of operation, the inherent limitations of the technology and the clinical data that have been acquired with NIRS monitoring in the broad field of acute clinical medicine.