Key points Although the exercise pressor reflex (EPR) and the chemoreflex (CR) are recognized for their sympathoexcitatory effect, the cardiovascular implication of their interaction remains elusive. We quantified the individual and interactive cardiovascular consequences of these reflexes during exercise and revealed various modes of interaction. The EPR and hypoxia‐induced CR interaction is hyper‐additive for blood pressure and heart rate (responses during co‐activation of the two reflexes are greater than the summation of the responses evoked by each reflex) and hypo‐additive for peripheral haemodynamics (responses during co‐activation of the reflexes are smaller than the summated responses). The EPR and hypercapnia‐induced CR interaction results in a simple addition of the individual responses to each reflex (i.e. additive interaction). Collectively, EPR:CR co‐activation results in significant cardiovascular interactions with restriction in peripheral haemodynamics, resulting from the EPR:CR interaction in hypoxia, likely having the most crucial impact on the functional capacity of an exercising human. Abstract We investigated the interactive effect of the exercise pressor reflex (EPR) and the chemoreflex (CR) on the cardiovascular response to exercise. Eleven healthy participants (5 females) completed a total of six bouts of single‐leg knee‐extension exercise (60% peak work rate, 4 min each) either with or without lumbar intrathecal fentanyl to attenuate group III/IV afferent feedback from lower limbs to modify the EPR, while breathing either ambient air, normocapnic hypoxia (SaO2 ∼79%, PaO2 ∼43 mmHg, PaCO2 ∼33 mmHg, pH ∼7.39), or normoxic hypercapnia (SaO2 ∼98%, PaO2 ∼105 mmHg, PaCO2 ∼50 mmHg, pH ∼7.26) to modify the CR. During co‐activation of the EPR and the hypoxia‐induced CR (O2‐CR), mean arterial pressure and heart rate were significantly greater, whereas leg blood flow and leg vascular conductance were significantly lower than the summation of the responses evoked by each reflex alone. During co‐activation of the EPR and the hypercapnia‐induced CR (CO2‐CR), the haemodynamic responses were not different from the summated responses to each reflex response alone (P ≥ 0.1). Therefore, while the interaction resulting from the EPR:O2‐CR co‐activation is hyper‐additive for blood pressure and heart rate, and hypo‐additive for peripheral haemodynamics, the interaction resulting from the EPR:CO2‐CR co‐activation is simply additive for all cardiovascular parameters. Thus, EPR:CR co‐activation results in significant interactions between cardiovascular reflexes, with the impact differing when the CR activation is achieved by hypoxia or hypercapnia. Since the EPR:CR co‐activation with hypoxia potentiates the pressor response and restricts blood flow to contracting muscles, this interaction entails the most functional impact on an exercising human.

Blocking the tibial and common peroneal nerves in the popliteal fossa separately provides for a faster onset than a prebifurcation sciatic block.

BackgroundChronic postsurgical pain and opioid use is a problem among patients undergoing many types of surgical procedures. A multidisciplinary approach to perioperative pain management known as a transitional pain service (TPS) may lower these risks.MethodsThis retrospective cohort study was conducted at the Salt Lake City VA Medical Center to compare patients undergoing elective primary or revision total knee, hip, or shoulder replacement or rotator cuff repair in the year before (2017) and after (2018) implementation of a TPS. The primary outcome is the proportion of patients taking opioids 90 days after surgery. Secondary outcomes include new chronic opioid use (COU) after surgery as well as the proportion of previous chronic opioid users who stopped or decreased opioid use after surgery.ResultsAt 90 days after surgery, patients enrolled in TPS were significantly less likely to be taking opioids (13.4% TPS vs 27.3% pre-TPS; p=0.002). This relationship remained statistically significant in a multivariable logistic regression analysis, where the TPS group had 69% lower odds of postoperative COU compared with the preintervention group (OR: 0.31; 95% CI: 0.14 to 0.66; p=0.03). Opioid-naive patients enrolled in TPS were less likely to have new COU after surgery (0.7% TPS vs 8.4% pre-TPS; p=0.004). Further, patients enrolled in TPS with existing COU prior to surgery were more likely to reduce or completely stop opioid use after surgery (67.5% TPS vs 45.3% pre-TPS; p=0.037) as compared with pre-TPS.ConclusionsThese data suggest that a TPS is an effective strategy for preventing new COU and reducing overall opioid use following orthopedic joint procedures in a Veterans Affairs hospital.

We sought to investigate the role of group III/IV muscle afferents in limiting endurance exercise performance, independently of their role in optimizing locomotor muscle O2 delivery. While breathing 100% O2 to ensure a similar arterial O2 content ([Formula: see text]) in both trials, eight male cyclists performed 5-km time trials under control conditions (HCTRL) and with lumbar intrathecal fentanyl (HFENT) impairing neural feedback from the lower limbs. After each time trial, common femoral artery blood flow (FBF) was quantified (Doppler ultrasound) during constant-load cycling performed at the average power of the preceding time trial. The assessment of end-tidal gases, hemoglobin content and saturation, and FBF facilitated the calculation of leg O2 delivery. Locomotor muscle activation during cycling was estimated from vastus lateralis EMG. With electrical femoral nerve stimulation, peripheral and central fatigue were quantified by pre- to postexercise decreases in quadriceps twitch torque (ΔQtw) and voluntary activation (ΔVA), respectively. FBF (~16 mL·min−1·W−1; P = 0.6), [Formula: see text] (~24 mL O2/dL; P = 0.9), and leg O2 delivery (~0.38 mL O2·min−1·W−1; P = 0.9) were not different during HCTRL and HFENT. Mean power output and time to completion were significantly improved by 9% (~310 W vs. ~288 W) and 3% (~479 s vs. ~463 s), respectively, during HFENT compared with HCTRL. Quadriceps muscle activation was 9 ± 7% higher during HFENT compared with HCTRL ( P < 0.05). ΔQtw was significantly greater in HFENT compared with HCTRL (54 ± 8% vs. 39 ± 9%), whereas ΔVA was not different (~5%; P = 0.3) in both trials. These findings reveal that group III/IV muscle afferent feedback limits whole body endurance exercise performance and peripheral fatigue by restricting neural activation of locomotor muscle. NEW & NOTEWORTHY Group III/IV muscle afferent feedback facilitates endurance performance by optimizing locomotor muscle O2 delivery but also limits performance by restricting neural drive to locomotor muscle. To isolate the performance-limiting effect of these sensory neurons, we pharmacologically attenuated their central projection during a cycling time trial while controlling for locomotor muscle O2 delivery. With no difference in leg O2 delivery, afferent blockade attenuated the centrally mediated restriction in motoneuronal output and improved cycling performance.

In many countries, liberalisation of the legislation regulating the use of cannabis has outpaced rigorous scientific studies, and a growing number of patients presenting for surgery consume cannabis regularly. Research to date suggests that cannabis can impact perioperative outcomes. We present recommendations obtained using a modified Delphi method for the perioperative care of cannabis-using patients. A steering committee was formed and a review of medical literature with respect to perioperative cannabis use was conducted. This was followed by the recruitment of a panel of 17 experts on the care of cannabis-consuming patients. Panellists were blinded to each other's participation and were provided with rater forms exploring the appropriateness of specific perioperative care elements. The completed rater forms were analysed for consensus. The expert panel was then unblinded and met to discuss the rater form analyses. Draft recommendations were then created and returned to the expert panel for further comment. The draft recommendations were also sent to four independent reviewers (a surgeon, a nurse practitioner, and two patients). The collected feedback was used to finalise the recommendations. The major recommendations obtained included emphasising the importance of eliciting a history of cannabis use, quantifying it, and ensuring contact with a cannabis authoriser (if one exists). Recommendations also included the consideration of perioperative cannabis weaning, additional postoperative nausea and vomiting prophylaxis, and additional attention to monitoring and maintaining anaesthetic depth. Postoperative recommendations included anticipating increased postoperative analgesic requirements and maintaining vigilance for cannabis withdrawal syndrome.