Warming Device Research Articles

Relationship between oxygen concentration and temperature in an exothermic warming device

IntroductionActively warming hypothermic patients or preventing hypothermia is critical in optimising outcomes in patients with traumatic injuries. Our aim was to investigate the effect of ambient oxygen concentration on the...

Safety and efficacy of resistive polymer versus forced air warming in total joint surgery

BackgroundForced-air warming is used as a mechanism to prevent hypothermia and adverse outcomes associated with hypothermia among patients undergoing surgery. Patient safety in healthcare includes the use of devices and technology that minimize potential adverse events to patients. The present study sought to compare the capabilities of patient warming between two different devices that use different mechanisms of warming: forced-air warming and non-air warming.MethodsOne hundred twenty patients undergoing total hip or total knee arthroplasty received patient warming via a forced warming device or non-air warming fabric conductive material. The project was part of a quality improvement initiative to identify warming devices effective in maintaining normothermic patient core temperatures during orthopedic surgery.ResultsForced-air warming and non-air warming achieved similar results in maintaining the core temperature of patients undergoing total knee or hip arthroplasty. No adverse events were reported in either group. Operating room staff observed that the non-air warming device was less noisy and appreciated the disposable covers that could be changed after each surgical case.ConclusionsThese findings demonstrate that hypothermia is achieved by both forced-air and non-forced air warming devices among total knee and hip arthroplasty patients. The potential for airflow disruption is present with the forced-air warming device and does not exist with the non-forced air device. The disruption of laminar airflow may be associated with surgical site infections. The disposable covers used to protect the device and patient have potential implications for surgical site infection. Quality improvement efforts aimed to enhance patient safety should include the implementation of healthcare equipment with the least known or suspected risk.

Perioperative management of opioid-tolerant patients

### Key points The assessment and treatment of opioid-tolerant patients in the perioperative and postoperative period can be challenging. Acute pain management can often be inadequate due to a number of factors. Compared with opioid-naive patients, opioid-tolerant patients will typically generate a greater workload for medical and nursing staff. Opioid tolerant patients express higher rest and dynamic pain scores, and two to three times greater opioid use via patient-controlled analgesia (PCA). They require more frequent consultations and prescription alterations.1 Medical and nursing staff may be unaccustomed to managing such patients and may be apprehensive in prescribing or administering large doses of opioids because of a fear of causing harm. Under-treatment of pain may result in opioid-seeking behaviour with the patient perceived as ‘manipulative’ and ‘non-cooperative’. This can have a negative impact on the doctor–patient relationship and overall patient care. Therefore the pain management plan for opioid tolerant patients requires careful consideration in the perioperative period in order to (i) prevent opioid withdrawal, (ii) provide effective analgesia, and (iii) to ensure continuity of care in the community after discharge from hospital. This review considers the various strategies that can be used in such settings. Opioids are prescribed to treat pain from a variety of causes, including chronic non-cancer pain, cancer pain, acute pain, and as substitution therapy in …

Heated intravenous fluids alone fail to prevent hypothermia in cats under general anaesthesia.

Objectives The objective was to evaluate the clinical efficiacy of a constant rate infusion of heated fluid as the sole means of preventing intraoperative hypothermia in cats. Methods This randomised, prospective, clinical study was conducted at a university teaching veterinary hospital. Female cats (American Society of Anesthesiologists [ASA] grade I) undergoing elective surgery by laparotomy under general anaesthesia (acepromazine 0.05 mg/kg SC; morphine 0.2 mg/kg IV; propofol IV titrated, isoflurane 2% in 100% oxygen) were randomised in two groups. Both groups were infused with fluid (NaCl 0.9%, 5 ml/kg/h) either at room temperature (control group) or prewarmed at 43°C (warmed group) using an Astoflo Plus eco (Stihler Electronic) fluid heating device. No other heating device was used. Temperature, heart rate, respiratory rate and SpO2 were evaluated after induction (T0) and every 15 mins for 1 h (T15, T30, T45, T60). Mean arterial blood pressure was recorded every 30 mins (T0, T30 and T60). Results Thirty-four female cats (ASA grade I) were enrolled in the study. There was no difference in age, weight, propofol dose or room temperature (22.4 ± 1.1°C vs 22.0 ± 1.5°C; P = 0.363) between control and warmed groups, respectively. In both groups, oesophageal temperature significantly decreased during anaesthesia ( P <0.0001). The temperature decrease after 1 h was -3.6 ± 0.7°C in the warmed group and was not significantly different from the control group (-3.4 ± 0.7°C; P = 0.307). The slopes of the temperature decrease did not significantly differ between the two groups (-0.058 ± 0.013°C/min vs -0.060 ± 0.010°C/min for the control and warmed groups, respectively; P = 0.624). Conclusions and relevance This study provides clinical evidence that a constant rate infusion of heated fluid alone fails to prevent intraoperative hypothermia in cats. The low infusion rate (5 ml/kg/h) could partly explain the ineffectiveness of this active warming device in minimising or delaying the onset of intraoperative hypothermia.

The effect of humidified heated breathing circuit on core body temperature in perioperative hypothermia during thyroid surgery

Purpose: During general anesthesia, human body easily reaches a hypothermic state, which is mainly caused by heat redistribution. Most studies suggested that humidified heated breathing circuits (HHBC) have little influence on maintenance of the core temperature during early phase of anesthesia. This study was aimed at examining heat preservation effect with HHBC in case of undergoing surgery with less exposure of surgical fields and short surgical duration.Methods: Patients aged 19 to 70 yr - old, ASA-PS I or II who were scheduled for elective thyroidectomy were assigned and divided to the group using HHBC (G1) and the group using conventional circuit (G2) by random allocation. During operation, core, skin, and room temperatures were measured every 5minutes by specific thermometer.Results: G1 was decreased by a lesser extent than G2 in core temperature, apparently higher at 30 and 60 minutes after induction. Skin and room temperatures showed no differences between the two groups (p>0.05). Consequently, we confirmed HHBC efficiently prevented a decrease in core temperature during early period in small operation which has difficulty in preparing warming devices or environments were not usually considered.Conclusions: This study showed that HHBC influences heat redistribution in early period of operation and can lessen the magnitude of the decrease in core body temperature. Therefore, it can be applied efficiently for other active warming devices in mild hypothermia.

Temperature management under general anesthesia: Compulsion or option.

Administration of general anesthesia requires continuous monitoring of vital parameters of the body including body temperature. However, temperature continues to be one of the least seriously monitored parameters perioperatively. Inadvertent perioperative hypothermia is a relatively common occurrence with both general and regional anesthesia and can have significant adverse impact on patients’ outcome. While guidelines for perioperative temperature management have been proposed, there are no specific guidelines regarding the best site or best modality of temperature monitoring and management intraoperatively. Various warming and cooling devices are available which help maintain perioperative normothermia. This article discusses the physiology of thermoregulation, effects of anesthesia on thermoregulation, various temperature monitoring sites and methods, perioperative warming devices, guidelines for perioperative temperature management and inadvertent temperature complications (hypothermia/hyperthermia) and measures to control it in the operating room.

Intraoperative Hypothermia and Surgical Site Infections in Patients with Class I/Clean Wounds: A Case-Control Study

Numerous surgical quality metrics focus on prevention of unintentional perioperative hypothermia due, in part, to the association between hypothermia and surgical site infections (SSI). However, few studies have comprehensively evaluated the relationship between these metrics and SSI. In this study, we evaluated individual components of 1 set of hypothermia metrics to determine their association with SSI. Patients with clean (class I) wounds who developed an SSI within 30 days after surgery, from January 2003 to December 2012, in 1 of 5 surgical specialties, were matched to specialty-specific controls without SSI. Stratified logistic regression models were used to assess the associations between (1) compliance with the Surgical Care Improvement Project (SCIP) Performance Measure, Surgery Patients with Perioperative Temperature Management (SCIP-Inf-10), overall and its components (maintenance of minimum body temperature and use of an active warming device) and SSI and (2) intraoperative hypothermia. In both univariate and adjusted analyses using adjusted odds ratios (OR), SCIP-Inf-10 compliance was not associated with SSI (composite compliance OR 0.89, 95% CI 0.63 to 1.24; temperature compliance OR 0.92, 95% CI 0.78 to 1.09; forced-air warming device compliance OR 0.95, 95% CI 0.76 to 1.19). Higher intraoperative nadir temperature (OR 1.19, 95% CI 1.05 to 1.35) was associated with SSI. Percent of time exposed to a temperature < 36°C (OR 0.98, 95% CI 0.96 to 1.01), and cumulative hypothermic exposure (°C*h <36°C) (OR 0.98, 95% CI 0.90 to 1.05) were not associated with SSI. Intraoperative hypothermia was not significantly associated with SSI. These results suggest that development of compliance metrics may not be an effective strategy for SSI reduction in class I surgical wounds.

Thermal Injury to Reconstructed Breasts from Commonly Used Warming Devices: A Risk for Reconstructive Failure.

Background:Sensation is decreased or absent after breast reconstruction. This leaves reconstructed breasts vulnerable to injury from common household thermal sources such as heating pads and hot water bottles. We sought to categorize these injuries, provide a treatment plan, and prevent these injuries in the future.Methods:A retrospective review of patients who had sustained burns to reconstructed breasts with household devices was performed at a single institution. A PubMed search was performed to identify and summarize articles cataloguing patients who had suffered burns to breast reconstructions.Results:Five patients in our practice were affected. Fifteen articles were identified in the literature search. A total of 40 patients had sustained thermal injury to reconstructed breasts, with the majority being full thickness burns (67.5%). Patients who sustained full thickness burns to reconstructed breasts were more likely to require an operative procedure compared with patients who sustained partial thickness burns (P = 0.0076).Conclusions:Reconstructed breasts are at risk for injury from commonly used household warming devices and ambient heat from the sun. As a result, patients should be counseled about these risks accordingly, to avoid injury or loss of reconstruction. These injuries require immediate vigilant treatment.

Reflective Blankets Are as Effective as Forced Air Warmers in Maintaining Patient Normothermia During Hip and Knee Arthroplasty Surgery

BackgroundThe use of forced air warming devices in the operating room has been shown to cause disruption of laminar airflow and a potential for increase in surgical site contamination. In contrast, conductive warming devices such as reflective blankets do not disrupt airflow and therefore have no potential for this increase in surgical site infection. However, some studies have shown them to be inferior to forced air warming devices in maintaining normothermia. We tested the hypothesis that the use of reflective blankets is as effective as forced air warming devices in maintaining intraoperative normothermia after adequate prewarming. MethodsWe performed a randomized, controlled trial of 50 patients undergoing hip or knee arthroplasty using a protocol of prewarming followed by application of either forced air warming device or a reflective blanket and recording the patients sublingual temperature at a 15-minute interval till arrival in the post-anesthesia care unit. ResultsThere was no significant difference in the sublingual temperatures in the 2 groups at any time point. ConclusionOur study shows that after a period of adequate prewarming, the use of reflective blankets is as effective as the use of forced air warming devices in maintaining normothermia in patients undergoing hip or knee arthroplasty.

Do on-demand irrigation warmers provide an adequate intraoperative rate of irrigation for holmium enucleation of the prostate?

Introduction: On-demand irrigation warmers are widely used to provide a convenient way of irrigating warmed fluids for endoscopic procedure. However, concern has been raised that flow rates via these devices are inadequate for safe operating. Holmium enucleation of prostate (HoLEP) requires significant volume and flow rate of irrigation. Poiseuille’s Law states the resistance of a tube will result in reduced flow and a reduction in pressure across the tube. The aim was to compare the irrigation rates provided by one such warming device compared to a standard giving set whilst simulating HoLEP and to monitor intravesical pressure. Methods: A simulated apparatus was set up to replicate HoLEP surgery. Simulated design rather than ‘real-life’ apparatus was used to allow for repeated testing in a more controlled environment and to avoid other variables due to operative differences. Comparison of irrigation rate and pressure difference was measured whilst using a standard irrigation set (Fresenius Kabi) with pre-warmed fluid and the Ranger irrigation warming system (3M). Pressure was measured using a pressure line passed via the working channel of the laser resectoscope. Results: The standard giving set demonstrated lower resistance and higher irrigation rates. The irrigation rate was 31% higher (7.2 vs 5.5 ml/s). A lower change in pressure across the standard giving set was found (20 vs 38 cm H2O). The resistance therefore is much higher in the Ranger irrigation system, which gave a much slower flow and greater drop in pressure. Conclusion: This unique demonstration has led to a quantitative assessment of commonly used giving sets and has shown irrigation rates via a standard giving set are 31% greater than through the Ranger irrigation warming system. On-demand fluid warmers are felt to result in poor intraoperative vision and pose a potential risk to patient safety during HoLEP and other urological procedures requiring high fluid volumes.

Effect of warming and flow rate conditions of blood warmers on red blood cell integrity.

Fluid warmers are routinely used to reduce the risk of hypothermia and cardiac complications associated with the infusion of cold blood products. However, warming blood products could generate haemolysis. This study was undertaken to compare the impact of temperature of blood warmers on the per cent haemolysis of packed red blood cells (RBCs) heated at different flow rates as well as non-flow conditions. Infusion warmers used were calibrated at 41·5°C ± 0·5°C and 37·5°C ± 0·5°C. Cold RBC units stored at 4°C in AS-3 (n = 30), aged 30-39 days old, were divided into half units before being allocated under two different scenarios (i.e. infusion pump or syringe). Blood warmers were effective to warm cold RBCs to 37·5°C or 41·5°C when used in conjunction with an infusion pump at flow rate up to 600 ml/h. However, when the warmed blood was held in a syringe for various periods of time, such as may occur in neonatal transfusions, the final temperature was below the expected requirements with measurement as low as 33·1°C. Increasing the flow with an infusion pump increased haemolysis in RBCs from 0·2% to up to 2·1% at a flow rate of 600 ml/h regardless of the warming device used (P < 0·05). No relevant increase of haemolysis was observed using a syringe. The use of a blood warmer adjusted to 41·5°C is probably the best choice for reducing the risk of hypothermia for the patient without generating haemolysis. However, we should be cautious with the use of an infusion pump for RBC transfusion, particularly at high flow rates.

Growth under elevated air temperature alters secondary metabolites in Robinia pseudoacacia L. seedlings in Cd- and Pb-contaminated soils

Plant secondary metabolites play a pivotal role in growth regulation, antioxidant activity, pigment development, and other processes. As the global climate changes, increasing atmospheric temperatures and contamination of soil by heavy metals co-occur in natural ecosystems, which alters the pH of rhizosphere soil and influences the bioavailability and mobility of metals. Elevated temperatures in combination with heavy metals are expected to affect plant secondary metabolites, but this issue has not been extensively examined. Here, we investigated secondary metabolites in Robiniapseudoacacia seedlings exposed to elevated temperatures using a passive warming device in combination with Cd- and Pb-contaminated soils. Heavy metals significantly stimulated the accumulation of saponins, phenolic compounds, and flavonoids in leaves and stems; alkaloid compounds increased in leaves and decreased in stems, and condensed tannins fluctuated. Elevated temperatures, alone and in combination with Cd and Pb, caused increases in secondary metabolites in the plant tissues. Phenolic compounds showed the greatest changes among the secondary metabolites and significant interactive effects of temperature and metals were observed. These results suggest that slightly elevated temperature could enhance protective and defense mechanisms of Robinia pseudoacacia seedlings exposed to heavy metals by stimulating the production of secondary metabolites.

Influence of a heating device and adhesive temperature on bond strength of a simplified ethanol-based adhesive system

Abstract Introduction Increased adhesive temperature has been reported to promote solvent evaporation, reduce viscosity, and improve monomeric permeation into dentin. Objective The aim of this study was to determine the influence of different heating methods on the microtensile bond strength of an etch-and-rinse adhesive to dentin. Material and method Twenty-four caries-free extracted human third molars were transversally sectioned to expose a flat dentinal surface. The samples were etched with 37% phosphoric acid gel and divided into three groups (n = 8): 1) Control - the adhesive system (Adper Single Bond 2; 3M ESPE) was applied at room temperature; 2) Warming device - the adhesive was warmed to 37°C in a custom device before application; and 3) Warm air - the adhesive was warmed to 50°C with an air jet after application on dentin. The specimens were restored with a composite resin (Filtek Z250 A2, 3M ESPE) and prepared for microtensile bond strength testing, after 24 h in water storage. The data were subjected to one-way ANOVA and Tukey's test (p &lt; 0.05). Result There was no significant difference among the groups (p &gt; 0.05). The mean bond strength values in the control, the warming device, and the warm air groups were 48.5 (± 5.2), 40.35 (± 4.9), and 47.2 (± 5.3) MPa, respectively (p = 0.05). Conclusion The different heating methods had no significant influence on the immediate microtensile bond strength of an etch-and-rinse ethanol-based adhesive to dentin.

Microwave decontamination of eyelid warming devices for the treatment of meibomian gland dysfunction.

The role of bacteria in meibomian gland dysfunction is unclear, yet contamination of compresses used as treatment may exacerbate this condition. This study therefore determined the effect of heating on bacteria on two forms of compress. Cotton flannels and MGDRx EyeBags (eyebags) were inoculated by adding experimental inoculum (Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa; one species for each set of 3 eyebags and flannels). One of each were then randomised in to 3 groups: no heating (control); therapeutic (47.4±0.7°C); or sanitisation (68±1.1°C). After treatment, bacteria cell numbers were calculated. The experiment was repeated in triplicate. There was a statistically significant difference between each treatment with the eyebag for S. aureus (control=7.15±0.11logC/ml, therapeutic heating=5.24±0.59logC/ml, sanitisation heating=3.48±1.43logC/ml; P<0.001) and S. pyogenes (7.36±0.13, 5.73±0.26, 4.75±0.54; P<0.001). P. aeruginosa also showed a significant reduction (P<0.001) from control (6.39±0.34) to therapeutic (0.33±0.26) and sanitisation (0.33±0.21), but the latter were similar (P=1.000). For the flannels, there was significant difference between each treatment for S. aureus (6.89±0.46, 3.96±1.76, 0.42±0.90; P<0.001). For S. pyogenes, there was a significant reduction (P<0.001) from control (7.51±0.10) to therapeutic (5.91±0.62) and sanitisation (5.18±0.8), but the latter were similar (P=0.07). For P. aeruginosa, there was a significant difference (P<0.001) from control (7.15±0.36) to sanitisation (5.83±0.44); but not to therapeutic (6.84±0.31) temperatures (P=0.07). Therapeutic heating produces a significant reduction in bacteria on the eyebags, but only sanitisation heating appears effective for flannels. However, patients should be advised to heat the eyebag to sanitisation temperatures on initial use.

Towards a Physiological Prandial Insulin Profile: Enhancement of Subcutaneously Injected Prandial Insulin Using Local Warming Devices

The need to develop an insulin delivery system that can closely mimic physiologically induced changes in prandial insulin release has been a major research target since the discovery of insulin. The challenges facing existing insulin delivery systems, related to relatively slow pharmacokinetics and pharmacodynamics, have been further highlighted by rapid advances in diabetes technology and progress in artificial pancreas research. Despite the growing interest in alternative routes of insulin administration, the subcutaneous route remains—at least for now—the preferred route for insulin administration. In this article, we review efforts aimed at developing subcutaneously injected ultrafast-acting insulin and measures aimed at enhancing insulin absorption, focusing on local warming devices.

Comparison of two passive warming devices for prevention of perioperative hypothermia in dogs.

To compare effects of two passive warming methods combined with a resistive heating mat on perioperative hypothermia in dogs. Fifty-two dogs were enrolled and randomly allocated to receive a reflective blanket (Blizzard Blanket) or a fabric blanket (VetBed). In addition, in the operating room all dogs were placed onto a table with a resistive heating mat covered with a fabric blanket. Rectal temperature measurements were taken at defined points. Statistical analysis was performed comparing all Blizzard Blanket-treated to all VetBed-treated dogs, and VetBed versus Blizzard Blanket dogs within spay and castrate groups, spay versus castrate groups and within groups less than 10 kg or more than 10 kg bodyweight. Data from 39 dogs were used for analysis. All dogs showed a reduction in perioperative rectal temperature. There were no detected statistical differences between treatments or between the different groups. This study supports previous data on prevalence of hypothermia during surgery. The combination of active and passive warming methods used in this study prevented the development of severe hypothermia, but there were no differences between treatment groups.

Risk factors for hypothermia in patients under general anesthesia: Is there a drawback of laminar airflow operating rooms? A prospective cohort study

IntroductionThe aim of this study was to estimate the prevalence and risk factors of hypothermia under general anesthesia in a large domestic hospital. MethodAll of the consecutive 1840 patients who underwent scheduled surgery between August and December 2013 were admitted to the study. The nasopharyngeal temperature was measured, and the following variables were also recorded: sex, age, type of surgery, duration of anesthesia, active warming devices and type of operating room. Univariate and multiple regression binary logistic analyses with odds ratios (ORs) and 95% confidence intervals (95% CIs) were used to assess the relationship between each clinical risk factor and hypothermia. ResultsThe prevalence of hypothermia under general anesthesia was 25.7%. In the univariate analysis, the risk factors of hypothermia were age, the duration of anesthesia, the type of operating room and the type of surgery. Sex was not included. In the multiple logistic regression analysis, the significant risk factors of hypothermia were advanced age, laminar airflow operating rooms and general surgeries. ConclusionIntraoperative hypothermia is still common and should therefore receive serious attention. Advanced age, the use of a laminar airflow operating room and general surgeries are high risk factors of hypothermia.

The effect of forced air warming devices compared to other active warming devices on surgical site contamination: a systematic review protocol.

REVIEW QUESTION / OBJECTIVE The objective of this systematic review is to synthesize the best available evidence comparing forced air warming devices to other active warming devices to determine whether or not there is an increased risk of surgical site contamination by microbial emissions during the perioperative period. Specifically the review question is: Do forced air warming devices compared to other active warming devices have an increased risk of surgical site contamination during the perioperative period? INCLUSION CRITERIA Types of participants This review will consider studies that include subjects (patients, volunteers, mannequins) of all ages that were warmed perioperatively in any type of surgery or simulated surgical environment. Types of intervention(s) This review will consider studies that compare only forced air warming devices to other active warming technologies such as a radiant warming blanket. Types of outcomes This review will consider studies that include the following outcome measures: particle counts or neutrally buoyant bubble counts, measured by: a laser particle count device or time-lapse photography.

Human Milk Warming Temperatures Using a Simulation of Currently Available Storage and Warming Methods.

Human milk handling guidelines are very demanding, based upon solid scientific evidence that handling methods can make a real difference in infant health and nutrition. Indeed, properly stored milk maintains many of its unique qualities and continues to be the second and third best infant feeding alternatives, much superior to artificial feeding. Container type and shape, mode of steering, amount of air exposure and storage temperature may adversely affect milk stability and composition. Heating above physiological temperatures significantly impacts nutritional and immunological properties of milk. In spite of this knowledge, there are no strict guidelines regarding milk warming. Human milk is often heated in electrical-based bottle warmers that can exceed 80°C, a temperature at which many beneficial human milk properties disappear. High temperatures can also induce fat profile variations as compared with fresh human milk. In this manuscript we estimate the amount of damage due to overheating during warming using a heat flow simulation of a regular water based bottle warmer. To do so, we carried out a series of warming simulations which provided us with dynamic temperature fields within bottled milk. We simulated the use of a hot water-bath at 80°C to heat bottled refrigerated milk (60ml and 178 ml) to demonstrate that large milk portions are overheated (above 40°C). It seems that the contemporary storage method (upright feeding tool, i.e. bottle) and bottle warming device, are not optimize to preserve the unique properties of human milk. Health workers and parents should be aware of this problem especially when it relates to sick neonates and preemies that cannot be directly fed at the breast.

Blood-Feeding Behaviors of Anopheles stephensi but not Phlebotomus papatasi are Influenced by Actively Warming Guinea Pigs (Cavia porcellus) Under General Anesthesia.

Animal models are often used to study hematophagous insect feeding behavior and evaluate products such as topical repellents. However, when these models are used the study animals often experience significant drops in core body temperature because of the effects of anesthesia. This study used a guinea pig model to investigate whether maintaining a normothermic core body temperature during anesthesia influenced the rate of Anopheles stephensi and Phlebotomus papatasi blood feeding. Experiments were conducted with anesthetized animals that had their body temperatures either maintained with a warming device or were allowed to drop naturally. Results showed that when guinea pigs were actively warmed by a heating device, An. stephensi feeding behavior was similar at the beginning and end of anesthesia. However, when a warming device was not used, fewer An. stephensi took a blood meal after the animals' temperatures had dropped. Phlebotomus papatasi were not as sensitive to changes in temperature and feeding rates were similar whether a warming device was used or not. These results are discussed and it is recommended that warming devices are used when conducting feeding experiments with insects sensitive to changes in host body temperature, such as An. stephensi.