Genomics of Plasmodium vivax in Colombia reveals evidence of local bottle-necking and inter-country connectivity in the Americas

Colombia aims to eliminate malaria by 2030 but remains one of the highest burden countries in the Americas. Plasmodium vivax contributes half of all malaria cases, with its control challenged by relapsing parasitaemia, drug resistance and cross-border spread. Using 64 Colombian P. vivax genomes collected between 2013 and 2017, we explored diversity and selection in two major foci of transmission: Chocó and Córdoba. Open-access data from other countries were used for comparative assessment of drug resistance candidates and to assess cross-border spread. Across Colombia, polyclonal infections were infrequent (12%), and infection connectivity was relatively high (median IBD = 5%), consistent with low endemicity. Chocó exhibited a higher frequency of polyclonal infections (23%) than Córdoba (7%), although the difference was not significant (P = 0.300). Most Colombian infections carried double pvdhfr (95%) and single pvdhps (71%) mutants, but other drug resistance mutations were less prevalent (< 10%). There was no evidence of selection at the pvaat1 gene, whose P. falciparum orthologue has recently been implicated in chloroquine resistance. Global population comparisons identified other putative adaptations. Within the Americas, low-level connectivity was observed between Colombia and Peru, highlighting potential for cross-border spread. Our findings demonstrate the potential of molecular data to inform on infection spread and adaptation.

State of Artemisinin and Partner Drug Susceptibility in Plasmodium falciparum Clinical Isolates from Colombia

Delayed parasite clearance time observed in Southeast Asia provided the first evidence of Plasmodium falciparum resistance to artemisinins. The ex vivo ring-stage survival assay (RSA) mimics parasite exposure to pharmacologically relevant artemisinin concentrations. Mutations in the C-terminal propeller domain of the putative kelch protein Pf3D7_1343700 (K13) are associated with artemisinin resistance. Variations in the pfmdr1 gene are associated with reduced susceptibility to the artemisinin partner drugs mefloquine (MQ) and lumefantrine (LF). To clarify the unknown landscape of artemisinin resistance in Colombia, 71 patients with uncomplicated P. falciparum malaria were enrolled in a non-randomized observational study in three endemic localities in 2014-2015. Each patient's parasite isolate was assessed for ex vivo RSA, K13-propeller mutations, pfmdr1 copy number, and pfmdr1 mutations at codons 86, 184, 1034, 1042, and 1246, associated with reduced susceptibility, and 50% inhibitory concentration (IC₅₀) for other antimalarial drugs. Ex vivo RSAs were successful in 56% (40/71) of samples, and nine isolates showed survival rates > 1%. All isolates had wild-type K13-propeller sequences. All isolates harbored either of two pfmdr1 haplotypes, NFSDD (79.3%) and NFSDY (20.7%), and 7.1% of isolates had > 1 pfmdr1 gene. In vitro IC₅₀ assays showed that variable proportions of isolates had decreased susceptibility to chloroquine (52.4%, > 100 nM), amodiaquine (31.2%, > 30 nM), MQ (34.3%, > 30 nM), and LF (3.2%, > 10 nM). In this study, we report ex vivo RSA and K13 data on P. falciparum isolates from Colombia. The identification of isolates with increased ex vivo RSA rates in the absence of K13-propeller mutations and no positivity at day three requires further investigation.

Impact of inspired gas mixtures on preoperative infants with hypoplastic left heart syndrome during controlled ventilation

BACKGROUND

Management strategies for preoperative infants with hypoplastic left heart syndrome (HLHS) include increased inspired nitrogen (hypoxia) and increased inspired carbon dioxide (hypercarbia). There are no studies directly comparing these 2 therapies in humans. This study compares the impact of hypoxia versus hypercarbia on oxygen delivery, under conditions of fixed minute ventilation.

METHODS AND RESULTS

Ten anesthetized and paralyzed preoperative infants with HLHS were evaluated in a prospective, randomized, crossover trial comparing hypoxia (17% FIO(2)) with hypercarbia (2.7% FICO(2)). Each patient was treated in a random order (10 minutes per condition) with a recovery period (15 to 20 minutes) in room air. Arterial (SaO(2)) and superior vena caval (SvO(2)) co-oximetry and cerebral oxygen saturation (ScO(2)) measurements were made at the end of each condition and recovery period. ScO(2) was measured by near infrared spectroscopy. Hypoxia significantly decreased both SaO(2) (-5.2+/-1.1%, P=0.0014) and SvO(2) (-5.6+/-1.7%, P=0.009) compared with baseline, but arteriovenous oxygen saturation (AVO(2)) difference (SaO(2)-SvO(2)) and ScO(2) remained unchanged. Hypercarbia decreased SaO(2) (-2.6+/-0.6%, P=0.002) compared with baseline but increased both ScO(2) (9.6+/-1.8%, P=0.0001) and SvO(2) (6+/-2.2%, P=0.022) and narrowed the AVO(2) difference (-8.5+/-2.3%, P=0.005). Both hypoxia and hypercarbia decreased the balance between pulmonary and systemic blood flow (Qp:Qs) compared with baseline.

CONCLUSIONS

In preoperative infants with HLHS, under conditions of anesthesia and paralysis, although Qp:Qs falls in both conditions, oxygen delivery is unchanged during hypoxia and increased during hypercarbia. These data cannot differentiate cerebral from systemic oxygen delivery.

Cerebral oxygen saturation before congenital heart surgery

BACKGROUND

In congenital heart disease (CHD), neurologic abnormalities suggestive of hypoxia-ischemia are often apparent before cardiac surgery. To evaluate preoperative cerebral oxygenation, this study determined cerebral O2 saturation (ScO2) in CHD and healthy children.

METHODS

Ninety-one CHD and 19 healthy children aged less than 7 years were studied before surgical or radiologic procedures. Arterial saturation (SaO2) and ScO2 were measured by pulse-oximetry and near infrared cerebral oximetry. Cerebral O2 extraction (CEO2) was calculated (SaO2-ScO2). SaO2, ScO2, and CEO2 were compared among diagnoses. Multivariable regression was performed between ScO2 and clinical variables.

RESULTS

In healthy subjects, ScO2 (68%+/-10%) and CEO2 (30%+/-11%) were similar to patients with ventricular septal defect, aortic coarctation, and single ventricle after Fontan operation. ScO2 was significantly decreased in patients with patent ductus arteriosus (53%+/-8%), tetralogy of Fallot (57%+/-12%), hypoplastic left heart syndrome (46%+/-8%), pulmonary atresia (38%+/-6%), and single ventricle after aortopulmonary shunt (50%+/-7%), or bidirectional Glenn operation (43%+/-6%). CEO2 was significantly different only in patent ductus arteriosus (46%+/-8%) and hypoplastic left heart syndrome (38%+/-12%). In multivariable regression, only SaO2 was related to ScO2 (R = 0.63, p < 0.001).

CONCLUSIONS

Cerebral oxygenation in CHD varies with anatomy and arterial saturation, and in some patients, it is very low compared with healthy subjects.

Arterial and venous contributions to near-infrared cerebral oximetry

BACKGROUND

Cerebral oximetry is a noninvasive bedside technology using near-infrared light to monitor cerebral oxygen saturation (Sco2) in an uncertain mixture of arteries, capillaries, and veins. The present study used frequency domain near-infrared spectroscopy to determine the ratio of arterial and venous blood monitored by cerebral oximetry during normoxia, hypoxia, and hypocapnia.

METHODS

Twenty anesthetized children aged < 8 yr with congenital heart disease of varying arterial oxygen saturation (Sao2) were studied during cardiac catheterization. Sco2, Sao2, and jugular bulb oxygen saturation (Sjo2) were measured by frequency domain near-infrared spectroscopy and blood oximetry at normocapnia room air, normocapnia 100% inspired O2, and hypocapnia room air.

RESULTS

Among subject conditions, Sao2 ranged from 68% to 100%, Sjo2 from 27% to 96%, and Sco2 from 29% to 92%. Sco2 was significantly related to Sao2 (y = 0. 85 x -17, r = 0.47), Sjo2 (y = 0.77 x +13, r = 0.70), and the combination (Sco2 = 0.46 Sao2 + 0.56 Sjo2 - 17, R = 0.71). The arterial and venous contribution to cerebral oximetry was 16 +/- 21% and 84 +/- 21%, respectively (where Sco2 = alpha Sao2 + beta Sjo2 with alpha and beta being arterial and venous contributions). The contribution was similar among conditions but differed significantly among subjects (range, approximately 40:60 to approximately 0:100, arterial:venous).

CONCLUSIONS

Cerebral oximetry monitors an arterial/venous ratio of 16:84, similar in normoxia, hypoxia, and hypocapnia. Because of biologic variation in cerebral arterial/venous ratios, use of a fixed ratio is not a good method to validate the technology.

Early survival of infants weighing 2.5 kilograms or less undergoing first-stage reconstruction for hypoplastic left heart syndrome

BACKGROUND

Results of staged palliation for hypoplastic left heart syndrome (HLHS) have improved in recent years; however, certain risk factors have been associated with decreased survival rates.

METHODS AND RESULTS

We retrospectively reviewed the medical records of 67 patients weighing </=2.5 kg undergoing the first stage of reconstructive surgery at our institution between January 1, 1990, and December 31, 1997. HLHS was present in 45 patients, complex double-outlet right ventricle in 10, unbalanced AV canal in 5, tricuspid atresia with transposition of the great vessels in 4, and other diagnoses in 3. Mean age at surgery was 10.1+/-10.7 days (median, 8 days), and mean weight was 2.2+/-0.3 kg (median, 2.2 kg). Fourteen patients weighed </=2.0 kg, and 2 patients weighed </=1.5 kg. Early mortality (death within 30 days or before hospital discharge) was 51% (34 of 67). No patient, procedural, or time-related variables correlated with increased mortality. However, there was a trend toward increased mortality with increased cardiopulmonary bypass time (P=0.076) and decreased preoperative ventricular performance (P=0.139).

CONCLUSIONS

These findings suggest that low weight alone in a patient with HLHS or an anatomic variant should not be considered a contraindication to staged reconstructive surgery.

Usefulness of intraoperative transesophageal echocardiography in predicting the degree of mitral regurgitation secondary to atrioventricular defect in children

The objectives of this study were to determine the validity of the grade of mitral regurgitation (MR) as imaged by intraoperative transesophageal echocardiography (TEE) in predicting the grade of MR at follow-up. Intraoperative TEE and corresponding follow-up transthoracic studies were retrospectively reviewed and the regurgitant jet area to left atrial area ratio was used to quantify the MR. Patient records were reviewed to identify factors contributing to the development of a certain grade of MR. Intraoperative TEE was useful in detecting severe MR that required further repair at the same time. However, discrepancy in the grade of MR at follow-up was noted in 47% of patients (21 of 47) and unchanged grade of MR was found only in 53% of patients (26 of 47). Blood pressures were significantly lower and heart rates higher intraoperatively. Initial preoperative grade of MR and type of atrioventricular canal defect did not predispose for a particular grade of MR at follow-up. The grade of MR by intraoperative TEE does not predict the grade of MR at follow-up as imaged by transthoracic echocardiography.

New directions in perioperative management for pediatric solid organ transplantation

Advances in pediatric solid organ transplantation have furthered the understanding of end-organ failures and refined the strategies for perioperative management of these otherwise lethal diseases. As the donor pool expands, the number of transplantations increases and long-term survival continues to improve, more complete knowledge of the immunologic and pathologic processes will be gained. A thorough understanding of the principles of transplantation medicine remains essential for physicians to provide optimal perioperative care of pediatric organ transplant patients.