Randomised controlled trial to investigate the relationship between mild hypercapnia and cerebral oxygen saturation in patients undergoing major surgery.

OBJECTIVES: The effects of hypercapnia on regional cerebral oxygen saturation (rSO2) during surgery are unclear. We conducted a randomised controlled trial to investigate the relationship between mild hypercapnia and rSO2. We hypothesised that, compared with targeted normocapnia (TN), targeted mild hypercapnia (TMH) during major surgery would increase rSO2. DESIGN: A prospective, randomised, controlled trial in adult participants undergoing elective major surgery. SETTING: A single tertiary centre in Heidelberg, Victoria, Australia. PARTICIPANTS: 40 participants were randomised to either a TMH or TN group (20 to each). INTERVENTIONS: TMH (partial pressure of carbon dioxide in arterial blood, PaCO2, 45-55 mm Hg) or TN (PaCO2 35-40 mm Hg) was delivered via controlled ventilation throughout surgery. PRIMARY AND SECONDARY OUTCOME MEASURES: The primary endpoint was the absolute difference between the two groups in percentage change in rSO2 from baseline to completion of surgery. Secondary endpoints included intraoperative pH, bicarbonate concentration, base excess, serum potassium concentration, incidence of postoperative delirium and length of stay (LOS) in hospital. RESULTS: The absolute difference between the two groups in percentage change in rSO2 from the baseline to the completion of surgery was 19.0% higher in both hemispheres with TMH (p<0.001). On both sides, the percentage change in rSO2 was greater in the TMH group than the TN group throughout the duration of surgery. The difference between the groups became more noticeable over time. Furthermore, postoperative delirium was higher in the TN group (risk difference 0.3, 95% CI 0.1 to 0.5, p=0.02). LOS was similar between groups (5 days vs 5 days; p=0.99). CONCLUSION: TMH was associated with a stable increase in rSO2 from the baseline, while TN was associated with a decrease in rSO2 in both hemispheres in patients undergoing major surgery. This resulted in a clear separation of percentage change in rSO2 from the baseline between TMH and TN over time. Our findings provide the rationale for larger studies on TMH during surgery. TRIAL REGISTRATION NUMBER: The Australian New Zealand Clinical Trials Registry (ACTRN12616000320459).

Predictors and Outcomes of Cardiac Surgery-Associated Delirium. A Single Centre Retrospective Cohort Study.

BACKGROUND: The predictors and independent outcome association of delirium after cardiac surgery are important and yet poorly characterised. METHODS: We performed a retrospective observational study of cardiac surgery patients between January 2009 and March 2016. We defined delirium using ICD-10 diagnostic codes. Multivariable analysis was conducted to find independent associations between baseline variables, delirium, and key clinical outcomes. RESULTS: We studied 2,447 study patients (28.7% female, median age was 66 [IQR 57-74] years). Delirium was coded for in 12.9% of patients overall, and in 22.9% of those aged >75years. Increasing age, Charlson co-morbidity index, admission not from home, peripheral vascular disease, respiratory disease, preoperative atrial fibrillation, duration of cardiopulmonary bypass and nature of surgery were all independent predictors of delirium. Delirium was independently and strongly associated with increased risk of reintubation (OR 8.18 [95% CI 5.24-12.78]), tracheostomy (OR 10.44 [95% CI 5.91-18.45]), and increased length of stay by 113.7 [95% CI 99.7-127.7] ICU hours and 6.95 [95% CI 5.94-7.95] hospital days, but not 30-day mortality (OR 0.78 [95% CI 0.38-1.59]; p=0.5). CONCLUSIONS: Delirium is common in cardiac surgery patients and increases with age. Delirium was the strongest predictor of reintubation, need for tracheostomy, and prolongation of intensive care unit (ICU) and hospital length of stay. Delirium prevention and attenuation are a priority in cardiac surgery patients.

The role of hypothermia in neurosurgical patients.

PURPOSE OF REVIEW: Interest in the therapeutic use of mild hypothermia was rekindled in the 1980s by the publication of promising animal studies. The results of several large clinical trials have become known in the last few years. This paper examines the recent evidence supporting the use of intraoperative hypothermia for neurosurgical patients. RECENT FINDINGS: This article will cover advances made in three key areas: evidence for a clinical benefit from intraoperative hypothermia, advances in cerebral temperature monitoring, and new techniques for cooling the brain. SUMMARY: There is currently insufficient evidence to support the use of mild intraoperative hypothermia for protection against focal cerebral ischaemia. Future investigations should focus on specific patient subgroups, and make use of recent advances in selective brain hypothermia and intracranial temperature monitoring.

Orthostatic hypotension occurs frequently in the first hour after anesthesia.

UNLABELLED: Symptoms of orthostatic intolerance are common after general anesthesia and are associated with an increased risk of postoperative morbidity. The contribution of orthostatic hypotension (OH) has not been well defined. We conducted a head-up tilt test on patients after general anesthesia for minor surgery to assess the incidence of and risk factors for OH after general anesthesia. One-hundred-four patients were enrolled and were prospectively divided into four groups: older female, older male, young female, and young male. The incidence of OH was 76.0%, 72.0%, 45.5%, and 62.5% respectively and was associated with increasing age (P < 0.05) and posttest dizziness (P < 0.05). Body mass index, preoperative blood pressure, ASA class, anesthetic duration, IV fluid administration, and use of analgesics and antiemetics in the postanesthetic care unit were not different in subjects who demonstrated OH compared with those with a normotensive response. Subjects with OH after general anesthesia did not increase their heart rate and diastolic blood pressure with a head-up tilt which may have been caused by persistent effects of anesthetics on reflex cardiovascular control and/or bedrest-induced dysregulation of reflex cardiovascular control. We conclude that OH is common after general anesthesia for minor surgery and may be the major cause of postoperative orthostatic intolerance. IMPLICATIONS: Orthostatic hypotension, a failure to maintain blood pressure on assuming an upright posture, is common after general anesthesia for minor surgery and may be the major cause of postoperative orthostatic intolerance.