Point-of-care haemoglobin accuracy and transfusion outcomes in non-cardiac surgery at a Canadian tertiary academic hospital: protocol for the PREMISE observational study

INTRODUCTION

Transfusions in surgery can be life-saving interventions, but inappropriate transfusions may lack clinical benefit and cause harm. Transfusion decision-making in surgery is complex and frequently informed by haemoglobin (Hgb) measurement in the operating room. Point-of-care testing for haemoglobin (POCT-Hgb) is increasingly relied on given its simplicity and rapid provision of results. POCT-Hgb devices lack adequate validation in the operative setting, particularly for Hgb values within the transfusion zone (60-100 g/L). This study aims to examine the accuracy of intraoperative POCT-Hgb instruments in non-cardiac surgery, and the association between POCT-Hgb measurements and transfusion decision-making.

METHODS AND ANALYSIS

PREMISE is an observational prospective method comparison study. Enrolment will occur when adult patients undergoing major non-cardiac surgery require POCT-Hgb, as determined by the treating team. Three concurrent POCT-Hgb results, considered as index tests, will be compared with a laboratory analysis of Hgb (lab-Hgb), considered the gold standard. Participants may have multiple POCT-Hgb measurements during surgery. The primary outcome is the difference in individual Hgb measurements between POCT-Hgb and lab-Hgb, primarily among measurements that are within the transfusion zone. Secondary outcomes include POCT-Hgb accuracy within the entire cohort, postoperative morbidity, mortality and transfusion rates. The sample size is 1750 POCT-Hgb measurements to obtain a minimum of 652 Hgb measurements <100 g/L, based on an estimated incidence of 38%. The sample size was calculated to fit a logistic regression model to predict instances when POCT-Hgb are inaccurate, using 4 g/L as an acceptable margin of error.

ETHICS AND DISSEMINATION

Institutional ethics approval has been obtained by the Ottawa Health Science Network-Research Ethics Board prior to initiating the study. Findings from this study will be published in peer-reviewed journals and presented at relevant scientific conferences. Social media will be leveraged to further disseminate the study results and engage with clinicians.

Phlebotomy resulting in controlled hypovolemia to prevent blood loss in major hepatic resections (PRICE-2): study protocol for a phase 3 randomized controlled trial

INTRODUCTION

Blood loss and red blood cell (RBC) transfusion in liver surgery are areas of concern for surgeons, anesthesiologists, and patients alike. While various methods are employed to reduce surgical blood loss, the evidence base surrounding each intervention is limited. Hypovolemic phlebotomy, the removal of whole blood from the patient without volume replacement during liver transection, has been strongly associated with decreased bleeding and RBC transfusion in observational studies. This trial aims to investigate whether hypovolemic phlebotomy is superior to usual care in reducing RBC transfusions in liver resection.

METHODS

This study is a double-blind multicenter randomized controlled trial. Adult patients undergoing major hepatic resections for any indication will be randomly allocated in a 1:1 ratio to either hypovolemic phlebotomy and usual care or usual care alone. Exclusion criteria will be minor resections, preoperative hemoglobin <100g/L, renal insufficiency, and other contraindication to hypovolemic phlebotomy. The primary outcome will be the proportion of patients receiving at least one allogeneic RBC transfusion unit within 30 days of the onset of surgery. Secondary outcomes will include transfusion of other allogeneic blood products, blood loss, morbidity, mortality, and intraoperative physiologic parameters. The surgical team will be blinded to the intervention. Randomization will occur on the morning of surgery. The sample size will comprise 440 patients. Enrolment will occur at four Canadian academic liver surgery centers over a 4-year period. Ethics approval will be obtained at participating sites before enrolment.

DISCUSSION

The results of this randomized control trial will provide high-quality evidence regarding the use of hypovolemic phlebotomy in major liver resection and its effects on RBC transfusion. If proven to be effective, this intervention could become standard of care in liver operations internationally and become incorporated within perioperative patient blood management programs.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03651154 . Registered on August 29 2018.

Phlebotomy resulting in controlled hypovolaemia to prevent blood loss in major hepatic resections (PRICE-1): a pilot randomized clinical trial for feasibility

BACKGROUND

Major liver resection is associated with blood loss and transfusion. Observational data suggest that hypovolaemic phlebotomy can reduce these risks. This feasibility RCT compared hypovolaemic phlebotomy with the standard of care, to inform a future multicentre trial.

METHODS

Patients undergoing major liver resections were enrolled between June 2016 and January 2018. Randomization was done during surgery and the surgeons were blinded to the group allocation. For hypovolaemic phlebotomy, 7-10 ml per kg whole blood was removed, without intravenous fluid replacement. Co-primary outcomes were feasibility and estimated blood loss (EBL).

RESULTS

A total of 62 patients were randomized to hypovolaemic phlebotomy (31) or standard care (31), at a rate of 3·1 patients per month, thus meeting the co-primary feasibility endpoint. The median EBL difference was -111 ml (P = 0·456). Among patients at high risk of transfusion, the median EBL difference was -448 ml (P = 0·069). Secondary feasibility endpoints were met: enrolment, blinding and target phlebotomy (mean(s.d.) 7·6(1·9) ml per kg). Blinded surgeons perceived that parenchymal resection was easier with hypovolaemic phlebotomy than standard care (16 of 31 versus 10 of 31 respectively), and guessed that hypovolaemic phlebotomy was being used with an accuracy of 65 per cent (20 of 31). There was no significant difference in overall complications (10 of 31 versus 15 of 31 patients), major complications or transfusion. Among those at high risk, transfusion was required in two of 15 versus three of nine patients (P = 0·326).

CONCLUSION

Endpoints were met successfully, but no difference in EBL was found in this feasibility study. A multicentre trial (PRICE-2) powered to identify a difference in perioperative blood transfusion is justified. Registration number: NCT02548910 ( http://www.clinicaltrials.gov).

Treatment of Frostbite With Hyperbaric Oxygen Therapy: A Single Center's Experience of 22 Cases

INTRODUCTION

Frostbite is well documented in the military and countries with extreme temperatures, and it is most likely due to increased exposure to cold temperatures and/or risk-taking behavior. Severity of injury depends on absolute temperature, wind chill, duration of exposure, wet or dry cold, immersion, clothing quality, and substance use. Hyperbaric oxygen therapy (HBOT) has been described as a treatment option but only in small case series.

OBJECTIVE

The aim of this retrospective study is to describe the usage patterns, side effects, and outcomes of HBOT used as an adjunct to wound care at a single major Canadian university hospital.

MATERIALS AND METHODS

A retrospective review of patients with frostbite injury admitted and treated with HBOT between January 2000 and March 2015 was performed. A total of 22 patients were studied. Available data included patient demographics, duration of exposure to cold temperature, severity of injury, time to HBOT, duration of therapy, side effects of therapy, concurrent therapies (dressing, anticoagulation, antibiotics), bone scan results, and consequent level of amputation.

RESULTS

The cohort consisted mostly of men (18, 81.8%) and patient mean age of 40 years (range, 13-70 years). Ten patients (45.5%) were intoxicated at the time of injury, and psychiatric illness was implicated in 9 (40.9%) patients. Of the presented injuries, 17 (77.3%) had frostbite to the upper extremity. Bone scans were performed on 16 (72.7%) patients. In 4 patients, the absence of radiotracer activity correlated with a protective effect on subsequent amputation levels. All patients received anticoagulant therapy. Of the 22 patients, 16 (72.7%) experienced at least 1 side effect of HBOT, including otologic barotrauma, nausea, vomiting, anxiety, oxygen toxicity seizure, and myopic changes. All study patients recovered without permanent sequelae; it is unclear whether HBOT reduced soft-tissue damage or amputation rates.

CONCLUSIONS

This is the largest cohort reported in the literature of patients with frostbite injuries treated with HBOT. Hyperbaric oxygen therapy may show positive impact on the demarcation level of frostbite and, despite the common side effects, it generally causes no long-term sequelae.

Hypovolemic phlebotomy in liver surgery is associated with decreased red blood cell transfusion

BACKGROUND

Perioperative red blood cell (RBC) transfusion is associated with poor outcomes in liver surgery. Hypovolemic phlebotomy (HP) is a novel intervention hypothesized to decrease transfusion requirements. The objective of this study was to examine this hypothesis.

METHODS

Consecutive patients who underwent liver resection at one institution (2010-2016) were included. Factors found to be predictive of transfusion on univariate analysis and those previously published were modeled using multivariate logistic regression.

RESULTS

A total of 361 patients underwent liver resection (50% major). HP was performed in 45 patients. Phlebotomized patients had a greater proportion of primary malignancy (31% vs 18%) and major resection (84% vs 45%). Blood loss was significantly lower with phlebotomy in major resections (400 vs 700 mL). Nadir central venous pressure was significantly lower with HP (2.5 vs 5 cm H₂O). On multivariate logistic regression, HP (OR 0.20, 95% CI 0.068-0.57, p = 0.0029), major liver resection (OR 2.91, 95% CI 1.64-5.18, p = 0.0003), preoperative hemoglobin < 125 g/L (OR 6.02, 95% CI 3.44-10.56, p < 0.0001), and underlying liver disease (OR 2.24, 95% CI 1.27-3.95, p = 0.0051) were significantly associated with perioperative RBC transfusion.

CONCLUSION

Hypovolemic phlebotomy appears to be strongly associated with a reduction in RBC transfusion requirements in liver resection, independent of other known risk factors.

Safety and feasibility of phlebotomy with controlled hypovolemia to minimize blood loss in liver resections

BACKGROUND

Liver resection can be associated with significant blood loss and transfusion. Whole blood phlebotomy is an under-reported technique, distinct from acute normovolemic hemodilution, the goal of which is to minimize blood loss in liver operation. This work sought to report on its safety and feasibility and to describe technical considerations.

METHODS

Consecutive patients who had an elective liver resection and concurrent phlebotomy between 2013 and 2016 were examined prospectively. Formal Inclusion and exclusion criteria were defined a priori. All surgical indications were allowed. All procedures were carried out with a stated goal of low central venous pressure anesthesia (<5 cm H₂O). The target phlebotomy volume was 7-10 mL/kg of patient body weight. The removed blood was not replaced by intravenous fluid. Removed blood was returned back to the patient after parenchymal transection. Safety end points were examined. A historic cohort (2010-2014) of major resections was included for comparison.

RESULTS

A total of 37 patients underwent liver resection with phlebotomy (86% major) and 101 without. Half had metastatic colorectal cancer. The median phlebotomy volume was 7.2 mg/kg (4.7-10.2), yielding a median drop in central venous pressure of 3 cm H₂O (0-15). Median blood loss was 400 vs 700 mL (P = .0016), and the perioperative transfusion rate was 8.1% vs 32% (P = .0048). There was no difference between the 2 groups in overall complications, mortality, intensive care admission, duration of stay, or end-organ ischemic complications.

CONCLUSION

Whole blood phlebotomy with controlled hypovolemia prior to liver resection seems to be safe and feasible. Comparative studies are required to determine its effectiveness.

Cognitive dysfunction after total knee arthroplasty: effects of intraoperative cerebral embolization and postoperative complications

Cerebral emboli identified as high-intensity transient signals (HITS) occur during total knee arthroplasty (TKA). Their effects on cognitive outcome remain speculative. Intraoperative HITS and postoperative complications were correlated with the cognitive function of TKA patients. Cognitive function was assessed both before and after surgery (1 week and 3 months). High-intensity transient signals occurred in 22 of 37 patients. Counts of HITSs were higher in patients with sonographically detected intracardiac shunts. Cognitive dysfunction was found in 41% of patients at 1 week, but in only 18% at 3 months. High-intensity transient signal counts were not associated with the prevalence of cognitive deficits. At 1 week, 58% of patients with cognitive deficits had at least 1 postoperative complication (6% in nondeficit patients). All cognitively impaired patients at 3 months had complications (17% in the nondeficit group). This raises the possibility that postoperative complications might be associated with cognitive dysfunction in TKA patients.

Hyperbaric oxygen in the treatment of calciphylaxis: a case series

BACKGROUND

Calciphylaxis, also referred to as calcific uraemic arteriolopathy, is a syndrome associated with end-stage renal disease (ESRD), and causes necrotic skin ulcers, often leading to a fatal outcome. Hyperbaric oxygen (HBO(2)) therapy has been used to enhance wound healing, but its role in the treatment of calciphylaxis is unclear.

METHODS

We undertook a retrospective study of patients on renal replacement therapy with biopsy-proven calciphylaxis who were treated with HBO(2) between March 1997 and February 2000.

RESULTS

Five patients were treated with HBO(2): three patients were on continuous ambulatory peritoneal dialysis (CAPD) and two were on chronic haemodialysis therapy. None of the patients had uncontrolled hyperparathyroidism and none underwent parathyroidectomy. The patients each received 25-35 treatments of HBO(2) at 2.5 atmospheres for 90 min per treatment. Two of these patients had complete resolution of extensive necrotic skin ulcers, with no adverse effects of HBO(2) therapy. Both had improvement in wound area transcutaneous oxygen pressure (P(tc)O(2)) with administration of 100% oxygen when measurements were taken at normobaric and hyperbaric pressures. In the other three patients receiving HBO(2), the skin lesions did not resolve. P(tc)O(2) was measured in two of these patients, neither of whom showed improvement with 100% oxygen administered at normobaric pressure.

CONCLUSIONS

The data support a role for HBO(2) in the treatment of some patients with calciphylaxis, particularly as in the absence of uncontrolled secondary hyperparathyroidism there are few therapeutic options.

Systemic fat and thrombus embolization in patients undergoing total knee arthroplasty with regional heparinization

A double-blind, randomized, controlled study was undertaken to determine if a technique of intraoperative anticoagulation would decrease the incidence or severity of venous embolization after tourniquet release during total knee arthroplasty. Sixty-six patients were randomized to receive either the heparin or placebo treatment. Transesophageal echocardiography was performed before and after tourniquet release to detect embolic material in the right atrium. Transient opacification of the right atrium was observed in all patients within the first 30 seconds after tourniquet release. Regional limb heparinization is not effective in reducing the intensity of right atrium opacification because much of the echogenic material was composed of fat rather than thrombus.

Cumulation characteristics of cisatracurium and rocuronium during continuous infusion

PURPOSE

The dissimilar pharmacokinetic properties of cisatracurium (CIS) and rocuronium (ROC) predict different potential for drug cumulation when these drugs are administered by continuous infusion. A study was therefore undertaken to compare cumulation potential of CIS and ROC during surgical procedures of relatively long duration (2-4 hr).

METHODS

Sufentanil/propofol-N2O anesthesia was administered to 40 ASA I and II adults. In a double-blind protocol, patients were randomly allocated to receive a continuous i.v. infusion of either CIS or ROC, titrated in progressive increments or decrements as required to achieve and maintain 95 +/- 5% depression of the T1 response of the adductor pollicis muscle, using a Datex NMT-100 Relaxograph EMG monitor applied at the wrist. At the end of surgery, 60 microg x kg(-1) neostigmine plus 15 microg x kg(-1) atropine were administered for reversal.

RESULTS

The duration of infusion was 104 +/- 33 min in group CIS and 110 +/- 23 min in group ROC (P=NS). In both groups, a progressive decrease in potency-adjusted infusion rates was observed after 30 min, then stabilized beyond 60 min. When allowing for an initial period of stabilization, mean potency-adjusted infusion requirements were: CIS 0.81 +/- 0.02 microg x kg(-1) x min(-1) and ROC 5.58 +/- 1.94 microg x kg(-1) x min(-1). There were no differences between groups at any time with regard to potency-adjusted infusion requirements necessary to maintain 90-99% block (P=NS). However, drug costs/hr for maintenance of neuromuscular block were less with CIS ($3.57 +/- 0.09) than with ROC ($6.03 +/- 0.27), P < 0.001.

CONCLUSION

When adjusted to equipotency, infusion requirements of CIS and ROC vary at similar rates during general anesthesia. Despite pharmacokinetic differences, neither drug demonstrates cumulation for infusion lasting up to 3.5 hr.