Risk factors and interventions associated with mortality or survival in adult COVID-19 patients admitted to critical care: a systematic review and meta-analysis

Background: Patients with confirmed COVID-19 admitted to intensive care units have a high mortality rate, which appears to be associated with increasing age, male sex, smoking history, hypertension and diabetes mellitus. Methods: A systematic review to determine risk factors and interventions associated with mortality/survival in adult patients admitted to an intensive care unit (ICU) with confirmed COVID-19/SARS-CoV-2 infection. The protocol was registered with PROSPERO (CRD42020181185). Results: The search identified 483 abstracts between 1 January and 7 April 2020, of which nine studies were included in the final review. Only one study was of low bias. Advanced age (odds ratio [OR] 11.99, 95% confidence interval [CI] 5.35–18.62) and a history of hypertension were associated with mortality (OR 4.17, 95% CI 2.90–5.99). Sex was not associated with mortality. There was insufficient data to assess the association between other comorbidities, laboratory results or critical care risk indices and mortality. The critical care interventions of mechanical ventilation (OR 6.25, 95% CI 0.75–51.93), prone positioning during ventilation (OR 2.06, 95% CI 0.20–21.72), and extracorporeal membrane oxygenation (ECMO) (OR 8.00, 95% CI 0.69, 92.33) were not associated with mortality. The sample size was insufficient to conclusively determine the association between these interventions and ICU mortality. The need for inotropes or vasopressors was associated with mortality (OR 6.36, 95% CI 1.89–21.36). Conclusion: The studies provided little granular data to inform risk stratification or prognostication of patients requiring intensive care admission. Larger collaborative research is needed to address this limitation.

Point-of-Care Clinical Ultrasound for Medical Students

PURPOSE

Our institution has recently implemented a point-of-care (POC) ultrasound training program, consisting of an e-learning course and systematic practical hands-on training. The aim of this prospective study was to evaluate the learning outcome of this curriculum.

MATERIALS AND METHODS

16 medical students with no previous ultrasound experience comprised the study group. The program covered a combination of 4 well-described point-of-care (POC) ultrasound protocols (focus assessed transthoracic echocardiography, focused assessment with sonography in trauma, lung ultrasound, and dynamic needle tip positioning for ultrasound-guided vascular access) and it consisted of an e-learning course followed by 4 h of practical hands-on training. Practical skills and image quality were tested 3 times during the study: at baseline, after e-learning, and after hands-on training.

RESULTS

Practical skills improved for all 4 protocols; after e-learning as well as after hands-on training. The number of students who were able to perform at least one interpretable image of the heart increased from 7 at baseline to 12 after e-learning, p<0.01, and to all 16 students after hands-on-training, p<0.01. The number of students able to cannulate an artificial vessel increased from 3 to 8 after e-learning and to 15 after hands-on training.

CONCLUSION

Medical students with no previous ultrasound experience demonstrated a considerable improvement in practical skill after interactive e-learning and 4 h of hands-on training.

Assessment of nociceptin/orphanin FQ and micro-opioid receptor mRNA in the human right atrium

BACKGROUND

The expression of micro (mu: MOP) and nociceptin/orphanin FQ (NOP) receptors in the human myocardium is controversial. In this polymerase chain reaction (PCR)-based study using human right atrial biopsies, we have (i) probed for mRNA encoding NOP receptor and its endogenous peptide precursor, ppN/OFQ, and mRNA encoding MOP and (ii) attempted to correlate expression with cardiac function.

METHODS

mRNA encoding MOP, NOP, and the precursor for NOP (ppN/OFQ) was assessed by quantitative real-time PCR (Q-PCR) using validated TaqMan primers and compared with a housekeeper (glyceraldehyde-3-phosphate dehydrogenase, GAPDH). Q-PCR data are expressed as the difference in cycle threshold (DeltaC(t)=C(tGene of interest)-C(tGAPDH): high value, low expression) and patients were grouped according to left ventricular ejection fraction (LVEF).

RESULTS

Forty patients were recruited; NOP, MOP, and ppN/OFQ mRNA were measured in 38, 29, and 10 patients, respectively. DeltaC(t) (median and range) values for NOP and MOP were 10.9 (7.8-13.7) and 16.0 (12.3-18.9), respectively, representing low expression of MOP and approximately 34-fold more NOP. MOP mRNA was not detected in seven samples and with DeltaC(t) values of approximately 20, ppN/OFQ was considered absent. When patients were grouped into normal (>50%) and impaired (<50%) LVEF, there was no difference between the groups for either NOP or MOP. In some patients, intraoperative LVEF was estimated using transoesophageal echocardiography, and there was no correlation with either NOP or MOP.

CONCLUSIONS

The human right atrium of patients with coronary artery disease and heart failure expresses mRNA encoding NOP and possibly low levels of MOP. This does not correlate with degree of cardiac dysfunction. In addition, the atrium does not express ppN/OFQ mRNA.

High transvalvular pressure gradients on intraoperative transesophageal echocardiography after aortic valve replacement: what does it mean?

Intraoperative transesophageal echocardiography is now used routinely during aortic valve replacement, allowing immediate evaluation of replaced or repaired valves. It is well recognised that high transvalvular pressure gradients can be detected immediately after implantation of a prosthetic aortic valve which may be due to multifactorial confounding variables, including functional phenomena, pressure recovery and prosthesis-patient mismatch. This review article explores the variety of methods available for assessing prosthetic aortic valve function and considers causative factors which may contribute to high transvalvular gradients in an attempt to determine whether a physical problem with the valve exists, or whether the valve is functioning normally.

Comparison of double-lung jet ventilation and one-lung ventilation for thoracotomy

BACKGROUND AND OBJECTIVE

Thoracic surgery requires immobilization of the operating area. Usually, this is achieved with one-lung ventilation (OLV), however this may still lead to some movement. High-frequency jet ventilation (HFJV) may be an alternative way of ventilation in thoracic surgery. The purpose of this study was to determine the effectiveness of HFJV as an alternative option to OLV for thoracic procedures.

METHODS

Sixty patients were randomized to receive either HFJV (n = 29) or OLV (n = 31) during the operation. During the course of the study 10 patients were excluded (4 patients in HFJV group and 6 patients in OLV group). The following haemodynamic and ventilatory parameters were recorded: heart rate, systolic and mean blood pressure, ventricular stroke volume, cardiac index, systemic vascular resistance, peak inspiratory pressure, oxygen saturation, PaO2 and PaCO2. Overall parameters were documented before the initiation of the chosen mode of ventilation every 15 min during the operation.

RESULTS

Patients in both groups showed comparable cardiovascular function. Mean values of peak inspiratory pressure were significantly higher in the OLV group. Oxygen saturation values were statistically higher in the HFJV group. PaCO2 values were similar in both during surgery, but were higher in the OLV group after awakening. Mean values of shunt fraction were lower in the HFJV group. Lower values of peak inspiratory pressure were therefore associated with higher partial pressure of carbon dioxide levels in the HFJV group. In the OLV group, 44% of patients experienced a postoperative sore throat. Operating conditions were comparable.

CONCLUSION

HFJV is safe option, comparable to OLV and offers some advantages for open-chest thoracic procedures.

The use of the stroke risk index to predict neurological complications following coronary revascularisation on cardiopulmonary bypass

The aim of this study was to investigate the validity of the stroke risk index (SRI) in identifying patients who develop a stroke following coronary artery bypass grafting on cardiopulmonary bypass. Retrospective data were analysed from 6846 patients who underwent adult coronary artery surgical procedures on cardiopulmonary bypass between 1997 and 2003. Patients were risk stratified pre-operatively using the SRI assessment model into low (Group A < or = 50), medium (Group B, 51-100) and high risk (Group C, > 100). A total of 217 patients (3.2%) with a mean age 65.9 +/- 11.7 years developed adverse neurological events following surgery. The CNS injury risk was 4% in Group A, 23% in Group B, and 8% in Group C. Pre-operatively, patients in Group B were older (p < 0.05), had a greater proportion of redo operations (OR 3.02; p < 0.001), diabetes mellitus (OR 2.51; p < 0.05), hypertension (OR 1.64; p < 0.01), myocardial infarction (OR 3.79; p < 0.05), ejection fraction < 30% (OR 1.46; p < 0.01) and absence of sinus rhythm (OR 2.52; p < 0.05) when compared with their counterparts. CNS events increased the patients' hospital stay by 40% in Groups A and C (p = 0.04) and 72% in Group B (p < 0.001). Only 31% returned home, compared with 85% of patients without cerebral complications (p < 0.001). These findings demonstrate that factors such as a pre-operative history of redo procedures, myocardial infarction, ejection fraction < 30% and absence of sinus rhythm play an important role in identifying the at-risk population. We conclude, therefore, that a further refinement and validation of the SRI is necessary.

The influence of transoesophageal echocardiography on intra-operative decision making. A European multicentre study. European Perioperative TOE Research Group

The role of transoesophageal echocardiography (TOE) in anaesthesia remains controversial because it is a rapidly evolving technique with few proven benefits and considerable cost. Recently, the Society of Cardiovascular Anaesthesiologists has published practice guidelines for the use of peri-operative TOE. To determine the current role of transoesophageal echocardiography and the relative impact of category-based transoesophageal echocardiographic indications the present study investigated its use in seven Western European countries. The study sample was taken from a prospective cohort of 224 patients with acute or chronic haemodynamic disturbances or at risk of myocardial ischaemia. All patients were monitored with two-lead electrocardiography and radial and pulmonary artery catheters, as well as biplane or multiplane transoesophageal echocardiography. A total of 2232 clinical interventions were made in these patients. The most frequently observed intervention was the administration of a fluid bolus (45% of all interventions). Overall, transoesophageal echocardiography was the most important guiding factor in 560 (25%) interventions. It was the most important monitor in guiding the following therapeutic interventions: anti-ischaemic therapy--207 of 372 interventions (56%); fluid administration--275 of 996 (28%) interventions; vasopressor or inotrope administration--56 of 316 (16%) interventions; vasodilator therapy--six of 142 (4%) interventions and depth of anaesthesia--four of 211 (2%) interventions. We found that transoesophageal echocardiography is frequently influential in guiding clinical decision making and is used most frequently for category II indications but category I indications were associated with more frequent change in management.

Biplane transoesophageal echocardiographic detection of myocardial ischaemia in patients with coronary artery disease undergoing non-cardiac surgery: segmental wall motion vs. electrocardiography and haemodynamic performance

Intra-operative segmental wall motion abnormalities (SWMA) detected by transoesophageal echocardiography (TOE) have been shown to be a sensitive indicator of myocardial ischaemia. To determine the incidence and characteristics of segmental wall motion abnormalities and to relate these changes to perioperative myocardial ischaemia, biplane TEE, electrocardiogram (ECG) (II+V5) and pulmonary capillary wedge pressure (PCWP) were continuously monitored in 62 consecutive patients with ischaemic heart disease undergoing non-cardiac surgery. Short-axis view at mid-papillary level in transverse scan (T-scan) and long-axis in longitudinal (L-scan) two-chamber view were used for wall motion analysis. New segmental wall motion abnormalities were detected in 16 of 64 patients (25%) using biplane transoesophageal echocardiography. Monoplane transoesophageal echocardiography showed a sensitivity of 75% and a specificity of 100%, electrocardiogram two lead showed a sensitivity of 56% and a specificity of 98%, whereas pulmonary capillary wedge pressure had a sensitivity of 25%, and a specificity of 93% and pressure rate quotient (PRQ) < 1 demonstrated sensitivity of 19% and a specificity of 92% in the detection of myocardial ischaemia. It is concluded that the long-axis view of the left ventricle provides additional information for the detection of segmental wall motion abnormalities. Neither changes in haemodynamic performance nor in electrocardiography leads II and V5 match those of transoesophageal echocardiography for the identification of myocardial ischaemia.

Gas exchange indices--how valid are they?

OBJECTIVE

This study examined the arterial-alveolar oxygen tension difference (AaDO2), arterial oxygen tension to inspired oxygen fraction ratio (PaO2/FiO2) and alveolar to arterial oxygen tension ratio (PAO2/PaO2) with regard to: (i) their correlation with the calculated pulmonary shunt in critically ill patients; and (ii) the influence of the inspired oxygen fraction on these indices before, during and after general anaesthesia.

DESIGN

This study comprised two sections: (i) retrospective analyses of blood gas data retrieved from the intensive care computerised database; and (ii) analyses of arterial blood gases before, during and after abdominal and orthopaedic surgery in patients subjected to various inspired fractions of oxygen.

SETTING

The study was conducted at an academic hospital.

PATIENTS

The first section of the study was a retrospective analysis of blood gases retrieved from a computerised database from the surgical and respiratory intensive care units. Blood gases which indicated hypoxaemia (arterial haemoglobin saturation less than 90%) were collected from patients who suffered from adult respiratory distress syndrome. The calculated pulmonary shunt was correlated with the AaDO2, PaO2/FiO2 and PAO2/PaO2. In the second section of this study, 15 patients of American Society of Anesthesiologists status 1, scheduled to undergo peripheral orthopaedic and intra-abdominal surgery, were exposed to various concentrations of inspired oxygen before, during and after general anaesthesia. At the end of a 15-minute period of exposure to a particular level of inspired oxygen (which was varied at random), arterial blood gases were analysed. A correlation was attempted between the inspired oxygen fraction and the various indices of pulmonary gas exchange.

INTERVENTION

Patients were subjected to the various inspired fractions of oxygen before, during and after general anaesthesia. A radial artery cannula, inserted under local anaesthesia, allowed the researchers to collect arterial blood gas analysis.

RESULTS

The correlation between the calculated pulmonary shunt and indices of gas exchange showed r = 0.35 for the AaDO2, r = 0.08 for the PaO2/FiO2 and r = 0.40 for the PAO2/PaO2. Stepwise variable selection demonstrated that the FiO2, PaCO2, PAO2 and shunt were the main components of the final models. The inspired oxygen fraction had an effect on the indices of gas exchange inasmuch as they all varied directly with the change in inspired oxygen concentration. Furthermore, the slope of this relationship was less steep during anaesthesia than in the case of values obtained before and after anaesthesia.

CONCLUSIONS

The so-called non-invasive indices of pulmonary gas exchange do not correlate well with the calculated pulmonary shunt, which is regarded as the gold standard that reflects the various components of gas exchange. We speculate that the poor performance of these indices can be explained by the fact that they do not take into account the mixed venous saturation and, except for the alveolar to arterial oxygen tension ratio, ignore the effects of alveolar ventilation. The effect of the inspired oxygen fraction on these ratios makes them difficult to interpret if similar inspired oxygen fractions are not used. The effect of the FiO2 on these indices could possibly be explained by the denitrogenation and collapse of alveoli with low ventilation perfusion ratios. The change in the slope of the FiO2 and the indices that was demonstrated during anaesthesia could possibly be explained by the expected change in the mixed venous saturation that occurs during anaesthesia.