This Month in Anesthesiology

Ultrasound-guided percutaneous cryoneurolysis is an analgesic technique in which exceptionally low temperatures are applied to reversibly ablate peripheral nerves, resulting in prolonged pain relief. The hypothesis that the severity of surgically related pain measures would be lower on postoperative day 2 with the addition of cryoanalgesia to standard-of-care treatment than with standard-of-care treatment alone was tested in a randomized controlled study of 60 patients undergoing unilateral or bilateral mastectomy with single-injection and continuous paravertebral nerve block for postoperative analgesia. On postoperative day 2, patients who had received active cryoneurolysis had a median [interquartile range] average level of pain, measured using the 11-point numeric rating scale, of 0 [0 to 1.4] while that in patients receiving sham treatment was 3.0 [2.0 to 5.0]; the difference (97.5% CI) was –2.5 (–3.5 to –1.5). Worst and average pain scores were lower for the active treatment group from days 1 to 21. Cryoneurolysis lowered cumulative opioid use during the first 3 weeks by 98%. No cryoneurolysis-related systemic side effects or complications were identified. See the accompanying Editorial on page 521.

The hypothesis that an unhealthy air quality index (greater than 100) due to wildfire smoke would increase the risk of an adverse respiratory event under general anesthesia in the pediatric population was tested in a retrospective double-cohort study of 625 pediatric patients aged 0 to 18 yr who presented for elective surgery before and after two wildfire events. An adverse respiratory event was defined as a composite of laryngospasm, bronchospasm, desaturation, and reintubation. In children without a history of reactive airway disease, the risk of adverse respiratory events was 40.3% (102 of 253) during periods with unhealthy air and 42.0% (95 of 226) during periods with healthy air; the relative risk (95% CI) was 0.96 (0.77 to 1.19). In children with a history of reactive airway disease, the risk of adverse respiratory events was 55.1% (43 of 78) during periods with unhealthy air and 36.8% (25 of 68) during periods of healthy air; the relative risk was 1.50 (1.04 to 2.17). The effect of air quality on adverse respiratory events was modified by reactive airway disease status with a relative risk of 1.56 (1.02 to 2.40). See the accompanying Editorial on page 524.

Risk prediction models can facilitate patient evaluation. This systematic review described and evaluated studies in which patient-specific multispecialty risk prediction scores for perioperative (up to 30 days postoperatively) mortality in pediatric populations were developed, modified, or externally validated. Ten studies were included; nine reported the development and validation of models while one focused on the external validation of an existing model. The unadjusted rate of mortality in the included studies ranged from 0.3 to 1.5% in development datasets using the full pediatric population and 3.6% in a population of neonates. An ideal model would present data on both calibration and discrimination in model development, be validated in a sample with a sufficiently high incidence of the outcome, be easily calculated, and have undergone comprehensive external validation in diverse patient populations. Comparing the risk prediction models using a variety of metrics, no model emerged as qualitatively better than any other. Although all models had good discrimination upon validation, none was recommended for use at this time due to a lack of external validations. See the accompanying Editorial on page 526.

The hypothesis that performance of models using both electronic health record and physiologic waveform data to predict postoperative deterioration 8 h before the event is superior to that of models using either modality alone was tested using intensive care unit (ICU) data collected after elective cardiac surgical procedures. A postoperative deterioration event was defined as a composite of cardiac index less than 2.0 ml · min^–1 · m^–2, mean arterial pressure less than 55 mmHg for at least 120 min, new or increased inotrope/vasopressor infusion, epinephrine bolus greater than or equal to 1 mg, or ICU mortality. All patients with at least one postoperative deterioration event were compared to a random sample of control patients not experiencing such events. Among 1,555 cases meeting inclusion criteria, 185 (12%) patients experienced 276 deterioration events between 24 h after postoperative ICU admission and discharge from the ICU. The positive predictive value of the best performing combined model in the 2013–2017 training/validation set was 63.6% but decreased to 33.9% in the 2017–2020 temporal holdout test set. The positive predictive values of models limited to either electronic health record or waveform data were 32.2% and 32.9%, respectively.

Etomidate, barbiturates, alphaxalone, and propofol allosterically potentiate receptor activation by γ-aminobutyric acid (GABA) and at high concentrations activate receptors without GABA. The hypothesis, based on two-state allosteric coagonist models, that pairs of four anesthetics (etomidate, the potent barbiturate R-mTFD-MPAB, alphaxalone, and propofol) acting through distinct sets of GABA type A (GABA_A) receptor sites would interact synergistically was tested in both zebrafish larvae hypnosis assays and electrophysiologic measures of activation of human α1β3γ2L GABA_A receptors expressed in Xenopus oocytes. Anesthetic interactions in GABA_A receptors were not consistently explained by two-state allosteric coagonism. These models qualitatively predicted synergistic interactions in both zebrafish and synaptic GABA_A receptors for four hypnotic drug pairs, propofol plus R-mTFD-MPAB and the three pairs containing alphaxalone, at low concentrations. However, this mechanism quantitatively approximated only the interaction of alphaxalone plus etomidate at higher concentrations. These findings suggest that allosteric coagonist models best describe interactions of agonists and coagonists that selectively bind in β+/α– subunit interfaces: GABA, etomidate, and alphaxalone.

Perioperative erythrocyte transfusions in pediatric patients are indicated for various reasons but can put patients at risk for transfusion-related adverse outcomes. Adoption of restrictive transfusion strategies in adult surgical patients has reduced allogeneic erythrocyte transfusions, adverse events, and hospital costs. This Clinical Focus Review begins by summarizing the evidence or expert consensus guidelines addressing use of restrictive versus liberal transfusion strategies in pediatric patients with massive hemorrhage or critical bleeding and in those undergoing noncardiac or cardiac surgery as well as in term and preterm neonates. Despite a lack of robust outcome data, several trials and expert guidelines recommend using a restrictive transfusion strategy in many pediatric populations and consensus statements recommend not using a single hemoglobin concentration transfusion trigger. This review then considers the rationale for incorporating physiologic parameters with hemoglobin concentration thresholds to guide transfusion management decisions. Such physiologic parameters could include hemodynamics, serial measurements of biochemical markers indicative of adequacy of tissue perfusion, and oxygen delivery and consumption quantified by novel technologies such as cerebral and somatic dynamic near infrared spectroscopy.

The anesthesia provider is likely to encounter patients with existing vision impairment given the increasingly aging population and rising prevalence of chronic degenerative diseases including cataracts, glaucoma, diabetic retinopathy, and age-related macular degeneration. Existing ophthalmic disease may affect the perioperative care of the patient undergoing nonocular surgery. In addition, perioperative injuries to the eye can occur, ranging from corneal injuries producing pain and reversible blurred vision, to serious disorders of the retina or optic nerve causing permanent blindness. Some of these injuries are easily preventable and treatable, such as exposure keratopathy—which is the most common cause of postoperative ocular complaints—while others, such as ischemic optic neuropathy—which is the most common cause of perioperative vision loss—have no recognized effective treatment. This review provides a best evidence-based approach to delivering anesthesia to patients with chronic ophthalmic disease and the prevention, diagnosis, and treatment of vision-affecting complications of nonocular surgery.