Initiation Of Ventilatory Support Research Articles

Central Venous Oxygen Saturation Behavior In Patients Under General Anesthesia

Introduction: Venous oxygen saturation is a metabolic variable that complements the information provided by hemodynamic parameters and globally evaluates the oxygen delivery and consumption by bodily tissues. Its precise values under general anesthesia are unknown, and constitutes an area of great interest for research. Objectives: To evaluate the effect of general anesthesia on Central Venous Oxygen Saturation (SvcO_2) in patients undergoing major surgical procedures. Methods: Aquasi-experimental before-after study in which central venous oxygen saturation (SvcO_2) values were obtained by gasometry and compared before the induction of anesthesia and 30 minutes after initiation of ventilatory support. The study included 111 patients undergoing major surgery under general anesthesia, grouped into 3 age groups. Results: There is a statistically significant increase in SvcO_2 from baseline values of 66.29% to 76.89% (15.99%, p＜0.05) in patients under general anesthesia. Conclusion: SvcO_2 increases significantly in patients of all ages under general anesthesia. The aforementioned results are important when re-evaluating the pre-established reference values in the various clinical settings requiring general anesthesia.

Treatment of respiratory impairment in patients with motor neuron disease in the Netherlands: patient preference and timing of referral

We assessed the first evaluation at a large ventilation clinic in the Netherlands to: (i) determine what proportion of patients with motor neuron disease would benefit from earlier referral; and (ii) examine the patient preferences regarding ventilatory support. Observational study at a single centre with a catchment area of 7.6 million inhabitants. Data on disease status, the referral process and patients' preferences regarding ventilatory support were collected during the first home ventilation services (HVS) assessment and analysed for correlation with the presence of daytime hypercapnia and suspected nocturnal hypoventilation. The latter conditions require immediate (within 48 h) or subacute (within 3 weeks) initiation of ventilatory support. Vital capacity (in percentage of predicted value, VC%pred) was assessed by referring physicians in 84% of the 217 referred patients; the mean VC%pred was 69% (SD 16). One-hundred and ninety-one patients attended the first HVS assessment without ventilatory support, at a median of 21 days following referral: 18% had respiratory failure (daytime hypercapnia), 19% had normocapnia but were suspected of nocturnal hypoventilation, and 63% had normocapnia without symptoms. Following the HVS assessment, 25 patients (13%) declined home mechanical ventilation; this occurred more often in patients with (14/70) compared with patients without respiratory impairment (11/121; P < 0.05). A meaningful proportion of patients who desire ventilatory support are referred to a ventilation clinic after already developing respiratory failure. Future studies could examine means, including more sensitive respiratory measures, to detect those patients who could benefit from earlier referral.

Respiratory support during the influenza A (H1N1) pandemic flu in Sweden

Acute respiratory insufficiency characterised critically ill patients during the influenza A (H1N1) pandemic 2009-2010. Detailed understanding of disease progression and outcome in relation to different respiratory support strategies is important. Data collected between August 2009 and February 2010 for a national intensive care unit influenza registry were combined with cases identified by the Swedish Institute for Infectious Disease Control. Clinical data was available for 95% (126/136) of the critically ill cases of influenza. Median age was 44 years, and major co-morbidities were present in 41%. Respiratory support strategies were studied among the 110 adult patients. Supplementary oxygen was sufficient in 15% (16), non-invasive ventilation (NIV) only was used in 20% (22), while transition from NIV to invasive ventilation (IV) was seen in 41% (45). IV was initiated directly in 24% (26). Patients initially treated with NIV had a higher arterial partial pressure of oxygen/fraction of oxygen in inspired gas ratio compared with those primarily treated with IV. Major baseline characteristics and 28-day mortality were similar, but 90-day mortality was higher in patients initially treated with NIV 17/67 (25%) as compared with patients primarily treated with IV 3/26 (12%), relative risk 1.2 (95% confidence interval 0.3-4.0). Critical illness because of 2009 influenza A (H1N1) in Sweden was dominated by hypoxic respiratory failure. The majority of patients in need of respiratory support were initially treated with NIV. In spite of less severe initial hypoxemia, initiation of ventilatory support with NIV was not associated with improved outcome.

An unexpected cause of post-operative shock

A 66-year-old woman, admitted for day-case laser excision of a T1N0 laryngeal squamous cell carcinoma, suddenly became dyspnoeic while in the recovery ward ∼20 min after successful completion of an uneventful procedure. Arterial blood gas analysis confirmed acute type II respiratory failure which prompted emergency re-intubation, initiation of ventilatory support and transfer to the intensive care unit. A portable chest X-ray showed bilateral alveolar filling defects consistent with severe pulmonary oedema and on 12-lead electrocardiogram (ECG), 1 mm of new ST segment elevation across leads V2–V4 was noted. Progressively worsening hypotension necessitated the initiation of inotropic support. Although the patient was not known to have ischaemic heart disease, her pro-atherosclerotic risk factors included current cigarette smoking, type 2 diabetes mellitus, hypertension and dyslipidaemia. Accordingly, an acute coronary syndrome (ACS) …

Continuous Flow Ventilatory Support (Clinical Experience)

Background. The world literature contains no reports on the clinical application of continuous flow ventilatory support by an insufflation catheter. Despite the use of different forms of ventilatory support, disconnection of patients from artificial ventilation is unsuccessful in 10—30% of cases despite the fact that the clinical and biochemical criteria are met. Objective: to discuss the efficiency of the new ventilation regime — continuous flow ventilatory support in the clinical setting. Methods: continuous flow ventilatory support with an original licensed multi-jet insufflation catheter or a terminal one-orifice catheter nasally inserted into the trachea was applied to 70 patients. It was used in a subgroup of 64 patients with chronic obstructive lung disease (COLD) due to the occurrence of global respiratory insufficiency caused by infectious complications and in a group of 6 patients as a ventilatory regime for their disconnection from long-term artificial ventilation, whose disconnection other ventilatory regimens being used were unsuccessful. Results. None patient with COLD should be intubated, and just 30 minutes after the initiation of ventilatory support with a multi-jet catheter, there were decreases in the mean respiration rate from 33±2.8 to 27±2.5 cycles/min and in paCo 2 from 11.9±1.7 to 10.8±1.6 kPa and an increase in paCo 2 from 5.7±1.1 to 6.8±1.3 kPa at FiO 2 =0.3. Within 24 hours after the initiation of ventilatory support, blood gas levels changed in response to the values typical of partial respiratory insufficiency. The spontaneous ventilation rate decreased to 20±2.2, paCO 2 reduced to 6.4±1.2 kPa and pO 2 continuously increased up to the value 8.9±1.4 kPa (FiO 2 =0.3) at hour 24 of ventilatory support. Ventilatory support lasted an average of 5 days. Statistical comparison of the study parameters showed a significant improvement (p&lt;0.05) just 6 hours after ventilatory support and a marked improvement of the parameters (p&lt;0.01) following 72 hours. In the other group of patients, continuous flow ventilatory support was used due to failing disconnection of the patients from long-term artificial ventilation. After extubation and 30 minutes after the initiation of continuous flow ventilatory support, the ventilation rated decreased to 27±2.5 cycles/min, there was a continuous reduction in paCO 2 to 3.9±0.9 kPa as a manifestation of hyperventilation that had been likely to be induced by a continuous decrease of paCO 2 to 8.8±1.4 kPa. Only 60 minutes after the initiation of ventilatory support, with the equal ventilation rate, the values of blood gases (paO 2 =9.9±1.5 kPa, paCO 2 =5.2±1.1 kPa) increased, as did VT (0.38±0.30), which permitted one to proceed with continuous flow ventilatory support that could be interrupted following 48 hours. Conclusion. The findings lead to the conclusion that continuous flow ventilatory support is an effective ventilation regimen that is applicable to patients with chronic obstructive lung disease in global respiratory insufficiency and makes it possible to overcome the period of, for example, infectious complications without intubation and artificial ventilation. It may also be used as a non-invasive ventilation regime in the disconnection of patients from long-term artificial ventilation. Its application in acute respiratory failure (acute respiratory failure, acute respiratory distress syndrome) requires further prospective studies.

Causes and effects of hyperchloremic acidosis

Gunnerson and colleagues [1] found in their retrospective study that critically ill patients with lactate acidosis had a higher mortality compared to patients with hyperchloremic acidosis, whose mortality was not significantly different from patients with no acidosis. Because of its iatrogenic etiology the authors commented that it is reassuring that hyperchloremic acidosis is not associated with an increased mortality. Previous randomized controlled trials have, however, generated concerns regarding the adverse effects of hyperchloremic acidosis associated with rapid isotonic saline administration. Rapid isotonic saline infusion predictably results in hyperchloremic acidosis [2]. The acidosis is due to a reduction in the strong anion gap by an excessive rise in plasma chloride as well as excessive renal bicarbonate elimination. In a randomized controlled trial with a mixed group of patients undergoing major surgery, isotonic saline infusion was compared to Hartmann's solution with 6% hetastarch with a balanced electrolyte and glucose solution. Two-thirds of patients in the isotonic saline group but none in the balanced fluid group developed hyperchloremic metabolic acidosis [3]. The hyperchloremic acidosis was associated with reduced gastric mucosal perfusion on gastric tonometry. Another randomized double blind trial of isotonic saline versus lactated Ringer's in patients undergoing aortic reconstructive surgery confirmed this result and the acidosis required interventions like bicarbonate infusion and was associated with the application of more blood products [4]. Hyperchloremia was found to have profound effects on eicosanoid release in renal tissue, leading to vasoconstriction and a reduction of the glomerular filtration rate [5]. The increased eicosanoid release may also explain the findings of reduced gastric perfusion in the hyperchloremia mentioned above [3]. The main adverse effect of saline induced hyperchloremic acidosis, however, may be the action that is taken to correct the abnormality. Acidosis is often seen as a reflection of poor organ perfusion or poor myocardial function and a negative base excess may prompt the application of boluses of more saline containing fluids exacerbating the acidosis, the use of blood products, escalation of inotrope support and initiation of ventilatory support [6,7]. The safety of hyperchloremic acidosis has not been established in prospective studies and in patients with different types of critical illness. Particularly in critically ill patients with other co-morbidities like renal disease, more physiological electrolyte solutions (e.g., Ringers lactate solution) may be preferable to isotonic saline and a slow fluid replacement protocol safer than rapid infusions.

Relationship between supramaximal flow during cough and mortality in motor neurone disease.

The main function of cough is clearance of intrathoracic airways. A normal cough is characterized by a transient increase in expiratory flow above the maximal flow-volume loop envelope, known as cough "spikes". They may be absent in patients with motor neurone disease. The relationship between cough pattern, pulmonary function and survival was studied. Fifty-three patients were recruited (25 bulbar). Vital capacity, maximal inspiratory and expiratory mouth pressures and cough flow/volume curves were performed on all patients, and the presence or absence of spikes were recorded. The primary endpoints were mortality or initiation of ventilatory support over a period of 18 months. Thirty-five patients died over the 18-month period of the study (including the six who were started on noninvasive ventilation). Twelve of the 24 patients with spikes died compared to 23 out of 29 patients without spikes (p<0.05). Patients without spikes were more likely to be bulbar on clinical grounds (p<0.0001) and had poorer lung function. The results showed an association between the absence of cough spikes and increased mortality. However the main determinants of survival in motor neurone disease are age, vital capacity and inspiratory mouth pressure, and it remains to be shown whether regular monitoring of cough conveys any additional advantage.

Outcome of paediatric domiciliary mask ventilation in neuromuscular and skeletal disease.

Noninvasive positive pressure ventilation delivered by nasal mask or facemask has been used widely in the last decade to manage chronic ventilatory failure in adults with neuromuscular and chest wall disease. However, it has been thought that paediatric patients would not be able to tolerate masks, and previous anecdotal reports on the paediatric application of mask ventilation have not assessed the effects on nocturnal and arterial blood gas control. Domiciliary mask ventilation has been used in 40 children with ventilatory insufficiency due to congenital neuromuscular and skeletal disease aged 9 months-16 yrs. Eighteen patients had symptomatic nocturnal hypoventilation, 17 had diurnal ventilatory failure, three were referred for weaning and two had frequent chest infections associated with sleep-disordered breathing. Thirty eight of the 40 patients tolerated mask ventilatory support long-term. Diurnal mean+/-SD oxygen tension in arterial blood (Pa,O2) increased from 8.5+/-1.8-10.9+/-1.7 kPa (p<0.001) and mean carbon dioxide tension in arterial blood (Pa,CO2) fell from 7.0+/-1.6-5.9+/-0.8 kPa (p=0.01) following initiation of ventilatory support. Mean and minimum nocturnal Pa,O2 and peak transcutaneous carbon dioxide tension (Ptc,CO2) (n=21) improved significantly. Mask ventilation can be used successfully in young children and reverses ventilatory insufficiency due to congenital neuromuscular and skeletal disease.

Surgical management of acquired post-intubation tracheo-oesophageal fistulas: 27 patients.

From 1962 to 1987, 27 patients with tracheo-oesophageal fistulae (TOF) were treated at our institution. Mean age was 43 years. The indications for respiratory support were blunt chest trauma (11), neurological dysfunction (8), and acute pulmonary distress syndrome (8). TOF symptoms occurred 12-200 days (mean 43) after initiation of ventilatory support and was caused by tracheostomy tube cuff (17), intubation tube cuff (8), or injury at the site of tracheostomy (2). The size of the fistula ranged from 0.3 to 5 cm (mean 2 cm). Seventeen of the 27 patients were operated upon. A simple repair of the TOF was performed via a cervical approach in 10 patients; tracheal resection and reconstruction was done in 4 patients presenting with tracheal stenosis, while 2 patients with slight tracheal stenosis had a simple repair of the TOF without the need for further tracheal surgery. Three patients underwent primary oesophagostomy, followed later by colon interposition. Five patients died. Ten cases were not operated upon: the TOF closed spontaneously in 1 patient, 1 patient was lost to follow-up and 8 died. In our series, significant tracheal stenosis occurred in only 6 patients (22%), only 4 of whom had tracheal resection. Simple repair of TOF provides excellent results with a low mortality (10%) considering the poor condition of the patients, and should be considered the procedure of choice. Surgical oesophageal diversion (i.e. cervical oesophagostomy and suture of distal oesophagus) is usually unnecessary.

Ventilatory Management in the Critically Ill

A basic understanding of respiratory physiology and ventilator-patient interaction is critical for the initiation of ventilatory support and management of the ventilated patient. A brief review of these subjects is incorporated in this outline of the approach to the patient requiring mechanical ventilation.