The cardiovascular effects of positive pressure ventilation

Causes of Perioperative Cardiac Arrest: Mnemonic, Classification, Monitoring, and Actions

Perioperative cardiac arrest (POCA) is a catastrophic complication that requires immediate recognition and correction of the underlying cause to improve patient outcomes. While the hypoxia, hypovolemia, hydrogen ions (acidosis), hypo-/hyperkalemia, and hypothermia (Hs) and toxins, tamponade (cardiac), tension pneumothorax, thrombosis (pulmonary), and thrombosis (coronary) (Ts) mnemonic is a valuable tool for rapid differential diagnosis, it does not cover all possible causes leading to POCA. To address this limitation, we propose using the preload-contractility-afterload-rate and rhythm (PCARR) construct to categorize POCA, which is comprehensive, systemic, and physiologically logical. We provide evidence for each component in the PCARR construct and emphasize that it complements the Hs and Ts mnemonic rather than replacing it. Furthermore, we discuss the significance of utilizing monitored variables such as electrocardiography, pulse oxygen saturation, end-tidal carbon dioxide, and blood pressure to identify clues to the underlying cause of POCA. To aid in investigating POCA causes, we suggest the Anesthetic care, Surgery, Echocardiography, Relevant Check and History (A-SERCH) list of actions. We recommend combining the Hs and Ts mnemonic, the PCARR construct, monitoring, and the A-SERCH list of actions in a rational manner to investigate POCA causes. These proposals require real-world testing to assess their feasibility.

Airway pressure release ventilation (APRV) versus pressure support ventilation (PSV)-A prospective intervention trial comparing haemodynamic parameters in intensive care patients

BACKGROUND AND AIM

Assisted mechanical ventilation may alter the pressure profile in the thorax compared to normal breathing, which can affect the blood flow to and from the heart. Studies suggest that in patients with severe lung disease, airway pressure release ventilation (APRV) may be haemodynamically beneficial compared to other ventilator settings. The primary aim of this study was to investigate if APRV affects cardiac index in intubated intensive care patients without severe lung disease when compared to pressure support ventilation (PSV). The secondary aim comprised potential changes in other haemodynamic and ventilatory parameters.

METHODS

Twenty patients were enrolled in the intensive care unit (ICU) at Sahlgrenska University Hospital. Eligible patients met the inclusion criteria; 18 years of age or above, intubated and mechanically ventilated, triggering and stable on PSV mode, with indwelling haemodynamic monitoring via a pulse-induced continuous cardiac output (PiCCO) catheter. The study protocol started with a 30-min interval on PSV mode, followed by a 30-min interval on APRV mode, and finally a 30-min interval back on PSV mode. At the end of each interval, PiCCO outputs, ventilator outputs, arterial and venous blood gas analyses, heart rate and central venous pressure were recorded and compared between modes.

RESULTS

There was no significant difference in cardiac index (3.42 vs. 3.39 L/min/m2) between PSV and APRV, but a significant increase in central venous pressure (+1.0 mmHg, p = .027). Furthermore, we found a significant reduction in peak airway pressure (-3.16 cmH2O, p < .01) and an increase in mean airway pressure (+2.1 cmH2O, p < .01). No statistically significant change was found in oxygenation index (partial pressure of O2 [pO2]/fraction of inspired oxygen) nor in other secondary outcomes when comparing PSV and APRV. There was no significant association between global end-diastolic volume index and cardiac index (R2 = 0.0089) or central venous pressure (R2 = 0.278). All parameters returned to baseline after switching the ventilator mode back to PSV.

CONCLUSION

We could not detect any changes in cardiac index in ICU patients without severe lung disease during APRV compared to PSV mode, despite lower peak airway pressure and increased mean airway pressure.

Benefits of intratracheal and extrathoracic high-frequency percussive ventilation in a model of capnoperitoneum

Abdominal inflation with CO2 is used to facilitate laparoscopic surgeries, however, providing adequate mechanical ventilation in this scenario is of major importance during anesthesia management. We characterized high-frequency percussive ventilation (HFPV) in protecting from the gas exchange and respiratory mechanical impairments during capnoperitoneum. In addition, we aimed to assess the difference between conventional pressure-controlled mechanical ventilation (CMV) and HFPV modalities generating the high-frequency signal intratracheally (HFPVi) or extrathoracally (HFPVe). Anesthetized rabbits (n = 16) were mechanically ventilated by random sequences of CMV, HFPVi, and HFPVe. The ventilator superimposed the conventional waveform with two high-frequency signals (5 Hz and 10 Hz) during intratracheal HFPV (HFPVi) and HFPV with extrathoracic application of oscillatory signals through a sealed chest cuirass (HFPVe). Lung oxygenation index ([Formula: see text]/[Formula: see text]), arterial partial pressure of carbon dioxide ([Formula: see text]), intrapulmonary shunt (Qs/Qt), and respiratory mechanics were assessed before abdominal inflation, during capnoperitoneum, and after abdominal deflation. Compared with CMV, HFPVi with additional 5-Hz oscillations during capnoperitoneum resulted in higher [Formula: see text]/[Formula: see text], lower [Formula: see text], and decreased Qs/Qt. These improvements were smaller but remained significant during HFPVi with 10 Hz and HFPVe with either 5 or 10 Hz. The ventilation modes did not protect against capnoperitoneum-induced deteriorations in respiratory tissue mechanics. These findings suggest that high-frequency oscillations combined with conventional pressure-controlled ventilation improved lung oxygenation and CO2 removal in a model of capnoperitoneum. Compared with extrathoracic pressure oscillations, intratracheal generation of oscillatory pressure bursts appeared more effective. These findings may contribute to the optimization of mechanical ventilation during laparoscopic surgery.NEW & NOTEWORTHY The present study examines an alternative and innovative mechanical ventilation modality in improving oxygen delivery, CO2 clearance, and respiratory mechanical abnormalities in a clinically relevant experimental model of capnoperitoneum. Our data reveal that high-frequency oscillations combined with conventional ventilation improve gas exchange, with intratracheal oscillations being more effective than extrathoracic oscillations in this clinically relevant translational model.

Assessing the Influence of Intraoperative Core Body Temperature on Postoperative Venous Thromboembolism after Abdominal Wall Reconstruction

Background

Venous thromboembolism (VTE) is a dangerous postoperative complication after abdominal wall reconstruction (AWR). Intraoperative core body temperature has been associated with thrombotic events in other surgical contexts. This study examines the effects of intraoperative temperature on VTE rate after AWR.

Methods

A retrospective study was performed on AWR patients. Cohorts were defined by postoperative 30-day VTE. Intraoperative core body temperature was recorded as the minimum, maximum, and mean intraoperative temperatures. Study variables were analyzed with logistic regression and cutoff analysis to assess for association with VTE.

Results

In total, 344 patients met inclusion criteria. Fourteen patients were diagnosed with 30-day VTE for an incidence of 4.1%. The VTE cohort had a longer median inpatient stay (8 days versus 5 days, P < 0.001) and greater intraoperative change in peak inspiratory pressure (3 mm H2O versus 1 mm H2O, P = 0.01) than the non-VTE cohort. Operative duration [odds ratio (OR) = 1.32, P = 0.01], length of stay (OR = 1.07, P = 0.001), and intraoperative PIP difference (OR = 1.18, P = 0.045) were significantly associated with 30-day VTE on univariable regression. Immunocompromised status (OR = 4.1, P = 0.023; OR = 4.0, P = 0.025) and length of stay (OR = 1.1, P < 0.001; OR = 1.1, P < 0.001) were significant predictors of 30-day VTE on two multivariable regression models. No significant associations were found between temperature metrics and 30-day VTE on cutoff point or regression analysis.

Conclusions

Intraoperative core body temperature did not associate with 30-day VTE after AWR, though operative duration, length of stay, immunocompromised status, and intraoperative PIP difference did. Surgeons should remain mindful of VTE risk after AWR, and future research is warranted to elucidate all contributing factors.

Ventilator-assisted preoxygenation in an aeromedical retrieval setting

OBJECTIVE

Ventilator-assisted preoxygenation (VAPOX) is a method of preoxygenation and apnoeic ventilation which has been tried in hospital setting. We aimed to describe VAPOX during intubation of critically unwell patients in aeromedical retrieval setting.

METHODS

Retrospective observational study of VAPOX performed at LifeFlight Retrieval Medicine (LRM) between January 2018 and December 2022 across Queensland, Australia. Demographic and clinical data were recorded. Descriptive statistics and paired Student's t-tests were used to evaluate the efficacy of VAPOX on oxygen saturation (SpO2 ).

RESULTS

VAPOX was used in 40 patients. Diagnoses included pneumonia (n = 11), COPD (n = 6) and neurological (n = 7). Patients were intubated in hospital (n = 36), in helicopter (n = 2) and ambulance (n = 2). Median VAPOX settings were: positive end-expiratory pressure 6 (IQR 5-9), pressure support 10 (IQR 10-14) and back up respiratory rate 14 (IQR 11-18). Twelve agitated patients underwent delayed sequence induction with ketamine. There was a statistically significant increase in SpO2 after application of VAPOX (P < 0.001), followed by a slight decrease after intubation (P = 0.006). Mean SpO2 were significantly improved after intubation compared with on arrival of LRM (P = 0.016). Hypotension was present prior to VAPOX (n = 13), during VAPOX (n = 2) and post-intubation (n = 15). Two patients had cardiac arrest. Three patients were started on VAPOX but subsequently failed. There were no significant oxygen depletion or aspiration events.

CONCLUSION

VAPOX can be considered for pre-intubation optimisation in the retrieval environment. The incidence of post-intubation critical hypoxia was low, and hypotension was high. Pre-intubation respiratory physiology can be optimised by delivering variable pressure supported minute ventilation, achieving a low incidence of critical hypoxia.

Right Ventricular Dysfunction on Transthoracic Echocardiography and Long-Term Mortality in the Critically Unwell: A Systematic Review and Meta-Analysis

OBJECTIVE

Right ventricular dysfunction (RVD) is common in the critically ill. To date studies exploring RVD sequelae have had heterogenous definitions and diagnostic methods, with limited follow-up. Additionally much literature has been pathology specific, limiting applicability to the general critically unwell patient.

METHOD AND STUDY DESIGN

We conducted a systematic review and meta-analysis to evaluate the impact of RVD diagnosed with transthoracic echocardiography (TTE) on long-term mortality in unselected critically unwell patients compared to those without RVD. A systematic search of EMBASE, Medline and Cochrane was performed from inception to March 2022. All RVD definitions using TTE were included. Patients were those admitted to a critical or intensive care unit, irrespective of disease processes. Long-term mortality was defined as all-cause mortality occurring at least 30 days after hospital admission. A priori subgroup analyses included disease specific and delayed mortality (death after hospital discharge/after the 30th day from hospital admission) in patients with RVD. A random effects model analysis was performed with the Dersimionian and Laird inverse variance method to generate effect estimates.

RESULTS

Of 5985 studies, 123 underwent full text review with 16 included (n = 3196). 1258 patients had RVD. 19 unique RVD criteria were identified. The odds ratio (OR) for long term mortality with RVD was 2.92 (95% CI 1.92-4.54, I2 76.4%) compared to no RVD. The direction and extent was similar for cardiac and COVID19 subgroups. Isolated RVD showed an increased risk of delayed mortality when compared to isolated left/biventricular dysfunction (OR 2.01, 95% CI 1.05-3.86, I2 46.8%).

CONCLUSION

RVD, irrespective of cause, is associated with increased long term mortality in the critically ill. Future studies should be aimed at understanding the pathophysiological mechanisms by which this occurs. Commonly used echocardiographic definitions of RVD show significant heterogeneity across studies, which contributes to uncertainty within this dataset.

Anaesthesia Management for Giant Intraabdominal Tumours: A Case Series Study

BACKGROUND

Due to a lack of randomised controlled trials and guidelines, and only case reports being available in the literature, there is no consensus on how to approach anaesthetic management in patients with giant intraabdominal tumours.

METHODS

This study aimed to evaluate the literature and explore the current status of evidence, by undertaking an observational research design with a descriptive account of characteristics observed in a case series referring to patients with giant intraabdominal tumours who underwent anaesthesia.

RESULTS

Twenty patients diagnosed with giant intraabdominal tumours were included in the study, most of them women, with the overall pathology being ovarian-related and sarcomas. Most of the patients were unable to lie supine and assumed a lateral decubitus position. Pulmonary function tests, chest X-rays, and thoracoabdominal CT were the most often performed preoperative evaluation methods, with the overall findings that there was no atelectasis or pleural effusion present, but there was bilateral diaphragm elevation. The removal of the intraabdominal tumour was performed under general anaesthesia in all cases. Awake fiberoptic intubation or awake videolaryngoscopy was performed in five cases, while the rest were performed with general anaesthesia with rapid sequence induction. Only one patient was ventilated with pressure support ventilation while maintaining spontaneous ventilation, while the rest were ventilated with controlled ventilation. Hypoxemia was the most reported respiratory complication during surgery. In more than 50% of cases, there was hypotension present during surgery, especially after the induction of anaesthesia and after tumour removal, which required vasopressor support. Most cases involved blood loss with subsequent transfusion requirements. The removal of the tumor requires prolonged surgical and anaesthesia times. Fluid drainage from cystic tumour ranged from 15.7 L to 107 L, with a fluid extraction rate of 0.5-2.5 L/min, and there was no re-expansion pulmonary oedema reported. Following surgery, all the patients required intensive care unit admission. One patient died during hospitalization.

CONCLUSIONS

This study contributes to the creation of a certain standard of care when dealing with patients presenting with giant intraabdominal tumour. More research is needed to define the proper way to administer anaesthesia and create practice guidelines.

Anesthetic management in patients having catheter-based thrombectomy for acute pulmonary embolism: A narrative review

Pulmonary embolism is the third leading cause of cardiovascular death. Novel percutaneous catheter-based thrombectomy techniques are rapidly becoming popular in high-risk pulmonary embolism - especially in the presence of contraindications to thrombolysis. The interventional nature of these procedures and the risk of sudden cardiorespiratory compromise requires the presence of an anesthesiologist. Facilitating catheter-based thrombectomy can be challenging since qualifying patients are often critically ill. The purpose of this narrative review is to provide guidance to anesthesiologists for the assessment and management of patients having catheter-based thrombectomy for acute pulmonary embolism. First, available techniques for catheter-based thrombectomy are reviewed. Then, we discuss definitions and application of common risk stratification tools for pulmonary embolism, and how to assess patients prior to the procedure. An adjudication of risks and benefits of anesthetic strategies for catheter-based thrombectomy follows. Specifically, we give guidance and rationale for use monitored anesthesia care and general anesthesia for these procedures. For both, we review strategies for assessing and mitigating hemodynamic perturbations and right ventricular dysfunction, ranging from basic monitoring to advanced inodilator therapy. Finally, considerations for management of right ventricular failure with mechanical circulatory support are discussed.

Mechanical Ventilation, Past, Present, and Future

Mechanical ventilation (MV) has played a crucial role in the medical field, particularly in anesthesia and in critical care medicine (CCM) settings. MV has evolved significantly since its inception over 70 years ago and the future promises even more advanced technology. In the past, ventilation was provided manually, intermittently, and it was primarily used for resuscitation or as a last resort for patients with severe respiratory or cardiovascular failure. The earliest MV machines for prolonged ventilatory support and oxygenation were large and cumbersome. They required a significant amount of skills and expertise to operate. These early devices had limited capabilities, battery, power, safety features, alarms, and therefore these often caused harm to patients. Moreover, the physiology of MV was modified when mechanical ventilators moved from negative pressure to positive pressure mechanisms. Monitoring systems were also very limited and therefore the risks related to MV support were difficult to quantify, predict and timely detect for individual patients who were necessarily young with few comorbidities. Technology and devices designed to use tracheostomies versus endotracheal intubation evolved in the last century too and these are currently much more reliable. In the present, positive pressure MV is more sophisticated and widely used for extensive period of time. Modern ventilators use mostly positive pressure systems and are much smaller, more portable than their predecessors, and they are much easier to operate. They can also be programmed to provide different levels of support based on evolving physiological concepts allowing lung-protective ventilation. Monitoring systems are more sophisticated and knowledge related to the physiology of MV is improved. Patients are also more complex and elderly compared to the past. MV experts are informed about risks related to prolonged or aggressive ventilation modalities and settings. One of the most significant advances in MV has been protective lung ventilation, diaphragm protective ventilation including noninvasive ventilation (NIV). Health care professionals are familiar with the use of MV and in many countries, respiratory therapists have been trained for the exclusive purpose of providing safe and professional respiratory support to critically ill patients. Analgo-sedation drugs and techniques are improved, and more sedative drugs are available and this has an impact on recovery, weaning, and overall patients' outcome. Looking toward the future, MV is likely to continue to evolve and improve alongside monitoring techniques and sedatives. There is increasing precision in monitoring global "patient-ventilator" interactions: structure and analysis (asynchrony, desynchrony, etc). One area of development is the use of artificial intelligence (AI) in ventilator technology. AI can be used to monitor patients in real-time, and it can predict when a patient is likely to experience respiratory distress. This allows medical professionals to intervene before a crisis occurs, improving patient outcomes and reducing the need for emergency intervention. This specific area of development is intended as "personalized ventilation." It involves tailoring the ventilator settings to the individual patient, based on their physiology and the specific condition they are being treated for. This approach has the potential to improve patient outcomes by optimizing ventilation and reducing the risk of harm. In conclusion, MV has come a long way since its inception, and it continues to play a critical role in anesthesia and in CCM settings. Advances in technology have made MV safer, more effective, affordable, and more widely available. As technology continues to improve, more advanced and personalized MV will become available, leading to better patients' outcomes and quality of life for those in need.

Evaluation of myocardial work changes after lung resection-the significance of surgical approach: an echocardiographic comparison between VATS and thoracotomy

OBJECTIVE

Considering the controversial benefits of video-assisted thoracoscopic surgery (VATS), we intended to evaluate the impact of surgical approach on cardiac function after lung resection using myocardial work analysis.

METHODS

Echocardiographic data of 48 patients (25 thoracotomy vs. 23 VATS) were retrospectively analyzed. All patients underwent transthoracic echocardiography (TTE) within 2 weeks before and after surgery, including two-dimensional speckle tracking and tissue Doppler imaging.

RESULTS

No notable changes in left ventricular (LV) function, assessed mainly using the LV global longitudinal strain (GLS), global myocardial work index (GMWI), and global work efficiency (GWE), were observed. Right ventricular (RV) TTE values, including tricuspid annular plane systolic excursion (TAPSE), tricuspid annular systolic velocity (TASV), right ventricular global longitudinal strain (RVGLS), and RV free-wall GLS (RVFWGLS), indicated greater RV function impairment in the thoracotomy group than in the VATS group [TAPSE(mm) 17.90 ± 3.80 vs. 21.00 ± 3.48, p = 0.006; d = 0.84; TASV(cm/s): 12.40 ± 2.90 vs. 14.70 ± 2.40, p = 0.004, d = 0.86; RVGLS(%): - 16.00 ± 4.50 vs. - 19.40 ± 2.30, p = 0.012, d = 0.20; RVFWGLS(%): - 11.50 ± 8.50 vs. - 18.31 ± 5.40, p = 0.009, d = 0.59; respectively].

CONCLUSIONS

Unlike RV function, LV function remained preserved after lung resection. The thoracotomy group exhibited greater RV function impairment than did the VATS group. Further studies should evaluate the long-term impact of surgical approach on cardiac function.

The results of inspiratory muscle training on cardiac, respiratory, musculoskeletal, and psychological status in patients with stable angina: a randomized controlled trial

PURPOSE

To determine the effect of inspiratory muscle training (IMT) on respiratory and peripheral muscle strength, functional exercise capacity, health-related quality of life (HRQoL), fatigue, depression, and cardiac functions in patients with stable angina.

METHODS

A randomized, controlled, single-blinded study. Twenty patients (59.95 ± 7.35 y, LVEF = 58.77 ± 7.49) with stable angina received IMT at the lowest load (10 cmH2O), and 20 patients (55.85 ± 7.60 y, LVEF = 62.26 ± 7.75) received training at 30% of maximal inspiratory pressure (MIP) seven days/8 weeks. Respiratory muscle strength (MIP; maximal expiratory pressure, MEP), peripheral muscle strength, pulmonary functions, functional exercise capacity (6-min walking test; exercise test), fatigue, HRQoL, depression, and cardiac functions were evaluated before and after.

RESULTS

A statistical difference was found between groups in terms of respiratory and peripheral muscle strength, pulmonary functions, functional exercise capacity (p < 0.05). The results of fatigue, depression, HRQoL, and cardiac functions were similar between the groups (p > 0.05).

CONCLUSIONS

This study is the first to demonstrate the positive effects of IMT in patients with stable angina. IMT is a safe and effective method and is recommended to be added to cardiopulmonary rehabilitation programs and guidelines, as it results in increased peripheral muscle strength and functional exercise capacity in stable angina patients.Implications for rehabilitationInspiratory muscle training (IMT) is a safe and effective method for coronary artery disease (CAD) patients with stable angina.IMT improved respiratory and peripheral muscle strength, functional exercise capacity, pulmonary functions, and health-related quality of life in CAD patients with stable angina.Perception of depression and fatigue were decreased with IMT in CAD patients with stable angina.

Sepsis Management in the Cardiac Intensive Care Unit

Septic shock management in the cardiac intensive care unit (CICU) is challenging due to the complex interaction of pathophysiology between vasodilatory and cardiogenic shock, complicating how to optimally deploy fluid resuscitation, vasopressors, and mechanical circulatory support devices. Because mixed shock portends high mortality and morbidity, familiarity with quality, contemporary clinical evidence surrounding available therapeutic tools is needed to address the resultant wide range of complications that can arise. This review integrates pathophysiology principles and clinical recommendations to provide an organized, topic-based review of the nuanced intricacies of managing sepsis in the CICU.

Mitral regurgitation in the critically ill: the devil is in the detail

Mitral regurgitation (MR) is common in the critically unwell and encompasses a heterogenous group of conditions with diverging therapeutic strategies. MR may present acutely with haemodynamic instability or more insidiously with failure to wean from mechanical ventilation. Critical illness is associated with marked physiological stress and haemodynamic changes that dynamically influence the severity and implication of MR. The expanding role of critical care echocardiography uniquely positions the intensivist to apply advanced bedside valvular assessment to recognise haemodynanically significant MR, manipulate and optimise cardiopulmonary physiology and identify patients requiring urgent cardiology and surgical referral. This review will consider common clinical scenarios, therapeutic strategies and the pearls and pitfalls of echocardiographic assessment and quantification in the critically unwell.

Understanding cardiopulmonary interactions through esophageal pressure monitoring

Esophageal pressure is the closest estimate of pleural pressure. Changes in esophageal pressure reflect changes in intrathoracic pressure and affect transpulmonary pressure, both of which have multiple effects on right and left ventricular performance. During passive breathing, increasing esophageal pressure is associated with lower venous return and higher right ventricular afterload and lower left ventricular afterload and oxygen consumption. In spontaneously breathing patients, negative pleural pressure swings increase venous return, while right heart afterload increases as in passive conditions; for the left ventricle, end-diastolic pressure is increased potentially favoring lung edema. Esophageal pressure monitoring represents a simple bedside method to estimate changes in pleural pressure and can advance our understanding of the cardiovascular performance of critically ill patients undergoing passive or assisted ventilation and guide physiologically personalized treatments.

Pulmonary arterial hypertension confirmed by right heart catheterization following COVID-19 pneumonia: A case report and review of literature

BACKGROUND

Pulmonary arterial hypertension (PAH) is a disease of the arterioles resulting in an increased resistance in pulmonary circulation with associated high pressures in the pulmonary arteries, causing irreversible remodeling of the pulmonary arterial walls. Coronavirus disease 2019 (COVID-19) has been associated with development of new onset PAH in the literature leading to symptoms of dyspnea, cough and fatigue that persist in spite of resolution of acute COVID-19 infection. However, the majority of these cases of COVID related PAH were diagnosed using echocardiographic data or via right heart catheterization in mechanically ventilated patients.

CASE SUMMARY

Our case is the first reported case of COVID related PAH diagnosed by right heart catheterization in a non-mechanically ventilated patient. Right heart catheterization has been the gold standard for diagnosis of pulmonary hypertension. Our patient had right heart catheterization four months after her initial COVID-19 infection due to persistent dyspnea.

CONCLUSION

This revealed new onset PAH that developed following her infection with COVID-19, an emerging sequela of the infection

Effect of oral administration of gabapentin on the minimum alveolar concentration of isoflurane in cats

Objective

To determine if oral gabapentin decreases the minimum alveolar concentration (MAC) of isoflurane in cats.

Study design

Prospective, randomized, blinded, crossover, and experimental study.

Animals

A total of six healthy adult cats (three male, three female) aged 18-42 months, weighing 3.31 ± 0.26 kg.

Methods

Cats were randomly given oral gabapentin (100 mg cat^-1) or placebo 2 h before starting MAC determination, with the crossover treatment given at least 7 days apart. Anesthesia was induced and maintained with isoflurane in oxygen. Isoflurane MAC was determined in duplicate using an iterative bracketing technique and tail clamp method. Hemodynamic and other vital variables were recorded at each stable isoflurane concentration and were compared between gabapentin and placebo treatments at lowest end-tidal isoflurane concentration when cats did not respond to tail clamping. A paired t-test was used to compare normally distributed data, and a Wilcoxon signed-rank test was applied for non-normally distributed data. Significance was set at p < 0.05. Data are mean ± standard deviation.

Results

Isoflurane MAC in the gabapentin treatment was 1.02 ± 0.11%, which was significantly lower than that in the placebo treatment (1.49 ± 0.12%; p < 0.001), decreasing by 31.58 ± 6.94%. No significant differences were found in cardiovascular and other vital variables between treatments.

Conclusion and clinical relevance

Oral administration of gabapentin 2 h before starting MAC determination had a significant isoflurane MAC-sparing effect in cats with no observed hemodynamic benefit.