Karen McRae

Relation of the static compliance curve and positive end-expiratory pressure to oxygenation during one-lung ventilation.

Background Positive end-expiratory pressure (PEEP) is commonly applied to the ventilated lung to try to improve oxygenation during one-lung ventilation but is an unreliable therapy and occasionally causes arterial oxygen partial pressure (Pao2) to decrease further. The current study examined whether the effects of PEEP on oxygenation depend on the static compliance curve of the lung to which it is applied. Methods Forty-two adults undergoing thoracic surgery were studied during stable, open-chest, one-lung ventilation. Arterial blood gasses were measured during two-lung ventilation and one-lung ventilation before, during, and after the application of 5 cm H2O PEEP to the ventilated lung. The plateau end-expiratory pressure and static compliance curve of the ventilated lung were measured with and without applied PEEP, and the lower inflection point was determined from the compliance curve. Results Mean (± SD) Pao2 values, with a fraction of inspired oxygen of 1.0, were not different during one-lung ventilation before (192 ± 91 mmHg), during (190 ± 90), or after ( 205 ± 79) the addition of 5 cm H2O PEEP. The mean plateau end-expiratory pressure increased from 4.2 to 6.8 cm H2O with the application of 5 cm H2O PEEP and decreased to 4.5 cm H2O when 5 cm H2O PEEP was removed. Six patients showed a clinically useful (> 20%) increase in Pao2 with 5 cm H2O PEEP, and nine patients had a greater than 20% decrease in Pao2. The change in Pao2 with the application of 5 cm H2O PEEP correlated in an inverse fashion with the change in the gradient between the end-expiratory pressure and the pressure at the lower inflection point (r = 0.76). The subgroup of patients with a Pao2 during two-lung ventilation that was less than the mean (365 mmHg) and an end-expiratory pressure during one-lung ventilation without applied PEEP less than the mean were more likely to have an increase in Pao2 when 5 cm H2O PEEP was applied. Conclusions The effects of the application of external 5 cm H2O PEEP on oxygenation during one-lung ventilation correspond to individual changes in the relation between the plateau end-expiratory pressure and the inflection point of the static compliance curve. When the application of PEEP causes the end-expiratory pressure to increase from a low level toward the inflection point, oxygenation is likely to improve. Conversely, if the addition of PEEP causes an increased inflation of the ventilated lung that raises the equilibrium end-expiratory pressure beyond the inflection point, oxygenation is likely to deteriorate.

Impact of extracorporeal life support on outcome in patients with idiopathic pulmonary arterial hypertension awaiting lung transplantation

BACKGROUND Our management of patients with idiopathic pulmonary arterial hypertension (iPAH) awaiting lung transplantation changed in 2006 with the introduction of extracorporeal life support (ECLS) as an option to bridge these patients to transplantation (BTT). METHODS To study the effect of this change on waiting list mortality and post-transplant outcome, 21 consecutive iPAH patients listed for lung transplantation between January 2006 and September 2010 (second cohort) were compared with 23 consecutive iPAH patients listed between January 1997 and December 2005 (first cohort). RESULTS Between the first and second cohort, the number of patients admitted to the hospital as BTT increased from 4% (1 of 23) to 48% (10 of 21; p = 0.0009). Six patients were BTT with ECLS in the second cohort, including 4 with the Novalung device (Novalung GmbH, Hechingen, Germany) connected as a pumpless oxygenating right-to-left shunt between the pulmonary artery and left atrium. While on the waiting list, 5 patients (22%) died in the first cohort and none in the second cohort (p = 0.03). Time on the waiting list decreased from 118 ± 85 to 53 ± 40 days between the first and second cohort (p = 0.004). After lung transplantation, the 30-day mortality was 16.7% in the first cohort and 9.5% in the second cohort (p = 0.5). The postoperative intensive care unit stay increased from 17 ± 13 to 36 ± 30 days between the first and second cohort (p = 0.02). The long-term outcome after lung transplantation remained similar between both cohorts. CONCLUSIONS Aggressive management with ECLS of iPAH patients awaiting lung transplantation could have a major impact to reduce the waiting list mortality. This may, however, be associated with longer intensive care unit stay after transplant.

Evidence basis for regional anesthesia in multidisciplinary fast-track surgical care pathways.

Fast-track programs have been developed with the aim to reduce perioperative surgical stress and facilitate patients recovery after surgery. Potentially, regional anesthesia and analgesia techniques may offer physiological advantages to support fast-track methodologies in different type of surgeries. The aim of this article was to identify and discuss potential advantages offerred by regional anesthesia and analgesia techniques to fast-track programs. In the first section, the impact of regional anesthesia on the main elements of fast-track surgery is addressed. In the second section, procedure-specific fast-track programs for colorectal, hernia, esophageal, cardiac, vascular, and orthopedic surgeries are presented. For each, regional anesthesia and analgesia techniques more frequently used are discussed. Furthermore, clinical studies, which included regional techniques as elements of fast-track methodologies, were identified. The impact of epidural and paravertebral blockade, spinal analgesia, peripheral nerve blocks, and new regional anesthesia techniques on main procedure-specific postoperative outcomes is discussed. Finally, in the last section, implementations required to improve the role of regional anesthesia in the context of fast-track programs are suggested, and issues not yet addressed are presented.

Choosing a Lung Isolation Device for Thoracic Surgery: A Randomized Trial of Three Bronchial Blockers Versus Double-Lumen Tubes

BACKGROUND: There is no consensus on the best technique for lung isolation for thoracic surgery. In this study, we compared the clinical performance of three bronchial blockers (BBs) available in North America with left-sided double-lumen tubes (DLTs) for lung isolation in patients undergoing left-sided thoracic surgery. METHODS: One hundred four patients undergoing left-sided thoracotomy or video-assisted thoracoscopic surgery were randomly assigned to one of the four lung isolation groups (n = 26/group). Lung isolation was with an Arndt® wire-guided BB (Cook® Critical Care, Bloomington, IN), a Cohen Flexi-tip® BB (Cook Critical Care) or a Fuji Uni-blocker® (Fuji Systems, Tokyo) or with a left-sided DLT (Mallinckrodt Medical, Cornamadde, Athlone, Westmeath, Ireland). Anesthetic management and lung isolation were performed according to a standardized protocol. Each group was randomly subdivided into two subgroups (n = 13/subgroup): immediate suction (at the time of insertion of the lung isolation device) (Subgroup I) or delayed suction (20 min after insertion of the lung separation device) (Subgroup D) according to when suction was applied to the BB suction channel or the bronchial lumen of the DLT. Using a verbal analog scale, lung collapse was assessed by the surgeons, who were blinded to the lung isolation technique. RESULTS: There was no difference among the lung isolation devices in lung collapse scores at 0 (P = 0.66), 10 (P = 0.78), or 20 min (P = 0.51) after pleural opening. The time to initial lung isolation was less for DLTs (93 ± 62 s) than BBs (203 ± 132) (P = 0.0001). There were no differences among the BBs in the time to lung isolation (P = 0.78). There were significantly more repositions after initial placement of the lung isolation device with BBs (35 incidents) than with DLTs (two incidents) (P = 0.009). The Arndt BB required repositioning more frequently (16 incidents) than the Cohen BB (8) or the Fuji BB (11) (P = 0.032). CONCLUSIONS: The three BBs provided equivalent surgical exposure to left-sided DLTs during left-sided open or video-assisted thoracoscopic surgery thoracic procedures. BBs required longer to position and required intraoperative repositioning more often. The Arndt BB needed to be repositioned more often than the other BBs.

The Toronto General Hospital Transitional Pain Service: development and implementation of a multidisciplinary program to prevent chronic postsurgical pain.

Chronic postsurgical pain (CPSP), an often unanticipated result of necessary and even life-saving procedures, develops in 5–10% of patients one-year after major surgery. Substantial advances have been made in identifying patients at elevated risk of developing CPSP based on perioperative pain, opioid use, and negative affect, including depression, anxiety, pain catastrophizing, and posttraumatic stress disorder-like symptoms. The Transitional Pain Service (TPS) at Toronto General Hospital (TGH) is the first to comprehensively address the problem of CPSP at three stages: 1) preoperatively, 2) postoperatively in hospital, and 3) postoperatively in an outpatient setting for up to 6 months after surgery. Patients at high risk for CPSP are identified early and offered coordinated and comprehensive care by the multidisciplinary team consisting of pain physicians, advanced practice nurses, psychologists, and physiotherapists. Access to expert intervention through the Transitional Pain Service bypasses typically long wait times for surgical patients to be referred and seen in chronic pain clinics. This affords the opportunity to impact patients’ pain trajectories, preventing the transition from acute to chronic pain, and reducing suffering, disability, and health care costs. In this report, we describe the workings of the Transitional Pain Service at Toronto General Hospital, including the clinical algorithm used to identify patients, and clinical services offered to patients as they transition through the stages of surgical recovery. We describe the role of the psychological treatment, which draws on innovations in Acceptance and Commitment Therapy that allow for brief and effective behavioral interventions to be applied transdiagnostically and preventatively. Finally, we describe our vision for future growth.

Emotional numbing and pain intensity predict the development of pain disability up to one year after lateral thoracotomy

Little is known about the factors that predict the transition of acute, time limited pain to chronic pathological pain following postero‐lateral thoracotomy. The aim of the present prospective, longitudinal study was to determine the extent to which (1) pre‐operative pain intensity, pain disability, and post‐traumatic stress symptoms (PTSS) predict post‐thoracotomy pain disability 6 and 12 months later; and (2) if these variables, assessed at 6 months, predict 12 month pain disability. Fifty‐four patients scheduled to undergo postero‐lateral thoracotomy for intrathoracic malignancies were recruited before surgery and followed prospectively for one year. The incidence of chronic post‐thoracotomy pain was 68.1% and 61.1% at the 6 and 12 month follow‐ups, respectively. Multiple regression analyses showed that neither pre‐operative factors nor acute movement‐evoked post‐operative pain predicted 6 or 12 month pain disability. However, concurrent pain intensity and emotional numbing, but not avoidance symptoms, made unique, significant contributions to the explanation of pain disability at each follow‐up (total R2=76.3.0% and 63.9% at 6 and 12 months, respectively, both p<0.0009). The relative contribution of pain intensity decreased, while that of emotional numbing increased with time, indicating a progressive de‐coupling of pain intensity and disability and a concomitant strengthening of the link between emotional numbing and disability. This suggests that pain may serve as a traumatic stressor which causes increased emotional numbing. The results also support recent suggestions that avoidance and emotional numbing constitute separate PTSS clusters. Further research is required to determine the source(s) of emotional numbing after postero‐lateral thoracotomy and effective interventions.

Outcome of patients with pulmonary arterial hypertension referred for lung transplantation: a 14-year single-center experience.

OBJECTIVE To analyze the outcomes of patients with pulmonary arterial hypertension referred for lung transplantation and determine the changes over time. METHODS All patients with pulmonary arterial hypertension referred for lung transplantation in our program from January 1997 to September 2010 were reviewed. Pulmonary arterial hypertension was classified as idiopathic (n = 123) or associated with congenital heart disease (n = 77), connective tissue disease (n = 102), or chronic thromboembolic disease (n = 14). RESULTS After completing their assessment, 61 patients (19%) were found to be unsuitable for lung transplantation, 38 (12%) refused lung transplantation, 65 (21%) were too early to be listed, and 48 (15%) died before their assessment (n = 34) or being listed (n = 14). Of the 100 patients listed for lung transplantation, 57 underwent bilateral lung transplantation, 22 underwent heart-lung transplantation, 18 died while waiting, and 3 were still waiting. The waiting list mortality was the greatest for patients with connective tissue disease-pulmonary arterial hypertension (34% vs 11% in the remaining patients, P = .005). The number of patients admitted to the hospital to be bridged to lung transplantation increased from 7% in the 1997-2004 cohort to 25% in the 2005-2010 cohort (P = .02). After lung transplantation, the 30-day mortality decreased from 24% in the 1997-2004 group to 6% in the 2005-2010 group (P = .007). The 10-year survival was worse for those with idiopathic pulmonary arterial hypertension (42% vs 70% for the remaining patients, P = .01). The long-term survival reached 69% at 10 years in the patients with connective tissue disease pulmonary arterial hypertension. CONCLUSIONS Lung transplantation is an option for about one third of the patients with pulmonary arterial hypertension referred for lung transplantation. The 30-day mortality after lung transplantation improved significantly over time, but the long-term survival remained similar between the two cohorts. Patients with connective tissue disease-pulmonary arterial hypertension have a high mortality on the waiting list but excellent long-term survival.

Volumetric capnography in children : influence of growth on the alveolar plateau slope

Background Lung growth in children is associated with dramatic increases in the number and surface area of alveolated airways. Modelling studies have shown the slope of the alveolar plateau (phase III) is sensitive to the total cross‐sectional area of these airways. Therefore, the influence of age and body size on the phase III slope of the volumetric capnogram was investigated. Methods Phase III slope (alveolar dcCO2/dv) and airway deadspace (VDaw) were derived from repeated single‐breath carbon dioxide expirograms collected on 44 healthy mechanically ventilated children (aged 5 months‐18 yr) undergoing minor surgery. Ventilatory support was standardized (VT = 8.5 and 12.5 ml/kg, [florin] = 8–15 breaths/min, inspiratory time = 1 s, end‐tidal partial pressure of carbon dioxide = 30–45 mmHg), and measurements were recorded by computerized integration of output from a heated pneumotachometer and mainstream infrared carbon dioxide analyzer inserted between the endotracheal tube and anesthesia circuit. Experimental data were compared to simulated breath data generated from a numeric pediatric lung model. Results An increased VDaw, a smaller VDaw/VT, and flatter phase III slope were found at the larger tidal volume (P < 0.01). Strong relationships were seen at VT = 12.5 ml/kg between airway deadspace and age (R2 = 0.77), weight (R2 = 0.93), height (R2 = 0.78), and body surface area (R2 = 0.89). The normalized phase III slopes of infants were markedly steeper than that of adolescents and were reduced at both tidal volumes with increasing age, weight, height, and body surface area. Phase III slopes and VDaw generated from modelled carbon dioxide washout simulations closely matched the experimental data collected in children. Conclusions Morphometric increases in the alveolated airway cross‐section with lung growth is associated with a decrease of the phase III slope. During adolescence, normalized phase III slopes approximate those of healthy adults. The change in slope with lung growth may reflect a decrease in diffusional resistance for carbon dioxide transport within the alveolated airway resulting in diminished acinar carbon dioxide gradients.

Prognostic significance of thymomas in patients with myasthenia gravis

BACKGROUND The presence of thymoma may be a negative prognostic factor with respect to the outcome of myasthenia gravis (MG). METHODS Of 122 consecutive patients with MG undergoing thymectomy between August 1994 and September 2000, 37 had a thymoma. Postoperative radiation was administered to all patients with stage II thymoma and higher. To determine differences in presentation and outcome, thymoma patients were compared with patients with atrophic (n = 49) or hyperplastic (n = 36) thymus gland on final pathology. RESULTS Thymoma patients were significantly older (52 +/- 14 vs 36 +/- 15 years, p < 0.0001) and included a significantly higher proportion of males (54% vs 28%, p = 0.006) than patients without thymoma. However, the preoperative Osserman grade and the duration of symptoms before surgery were not significantly different between groups. Mean follow-up after thymectomy was not significantly different between patients with or without thymoma (32 +/- 23 vs 37 +/- 19 months, respectively, p = 0.3). At last follow-up, the proportion of asymptomatic patients (63% vs 70%, respectively, p = 0.5) and the mean Osserman grade (0.6 +/- 0.9 vs 0.5 +/- 0.9, respectively, p = 0.6) were similar in both groups. In addition, the rate of complete remission reached 36% at 5 years in patients with or without thymoma (p = 0.8). CONCLUSIONS Although myasthenic patients with thymoma are significantly older and include a greater proportion of males, the overall outcome, including the rate of complete remission, was similar between patients with or without thymoma. Therefore, the presence of a thymoma should not necessarily be viewed as a negative prognostic factor regarding recovery from myasthenia gravis.

PAIN MANAGEMENT IN CARDIOTHORACIC PRACTICE

All analgesia regimens have benefits and side effects, and personal expertise can greatly influence the efficacy of regional techniques. A multimodal approach to analgesic management allows physicians to achieve maximum analgesic efficacy while limiting side effects. An appropriate analgesic plan takes into account the extent of pain associated with the type of incision and adjusts this according to each patients individual needs. As we enter the new millennium, thoracic and cardiac surgery is becoming more innovative, and the life expectancy of people in the first world is constantly increasing. Older people with less physiologic reserve and more multisystem dysfunction are undergoing more major surgical procedures, and adequate pain control in the postoperative period is becoming increasingly important.