Effect of irrigation fluid temperature on core temperature and hemodynamic changes in transurethral resection of prostate under spinal anesthesia.

BACKGROUND: Hypothermia is a frequent observation in elderly males undergoing transurethral resection of prostate (TURP) under spinal anesthesia. The use of irrigating fluids at room temperature results in a decrease body temperature. Warmed irrigating solutions have shown to reduce heat loss and the resultant shivering. Such investigation was not much tried in low resource settings. AIM: To compare the resultant change in core temperature and hemodynamic changes among patients undergoing TURP surgery under spinal anesthesia using warm and room temperature irrigation fluids. SETTINGS AND
DESIGN: Randomized prospective study at a tertiary care center.
METHODS: This study was conducted on 40 male patients aged 50-85 years undergoing TURP under spinal anesthesia. Of which, 20 patients received irrigation fluid at room temperature 21°C and 20 patients received irrigation fluid at 37°C after random allocation. Core temperatures and hemodynamic parameters were assessed in all patients at preoperative, intra-operative, and postoperative periods. Intra-operative shivering was also noted in both groups. STATISTICAL ANALYSIS: Unpaired and Paired Student's t-test.
RESULTS: For patients who underwent irrigation with fluid at room temperature Core temperature drop from 36.97°C in preoperative to 34.54°C in postoperative period with an effective difference of 2.38°C. Among patients who received warmed irrigation fluid at 37°C had core temperature drop from 36.97°C to 36.17°C and the effect of fall was 0.8°C. This difference was statistically significant (P < 0.001). Shivering of Grades 1 and 2 was observed in nine patients, of Group 1 while only three patients had Grades 1 and 2 shivering in Group 2. The hemodynamic parameters were similar in the two groups and did not reach significant difference.
CONCLUSION: Use of warm irrigation fluid during TURP reduces the risk of perioperative hypothermia and shivering.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Body temperature is a vital sign and 37°C is the mean core temperature of a healthy human.[1] Perioperative hypothermia is an unintentional drop in core body temperature <36°C during or immediately following an operation.[2] Even perioperative mild hypothermia defined as a 1-3° decrease in normal core temperature (37°C) has been reported to have an adverse effect.[3]

The reported prevalence of perioperative hypothermia ranges from 50%-90%.[4] Most patients undergoing transurethral resection of the prostate (TURP) are elderly and have co-morbid cardiac or pulmonary diseases. Inadvertent hypothermia is common in patients undergoing surgical procedures. This is thus a concern as TURP has been associated with perioperative hypothermia and subsequent shivering. In addition, the TURP procedure requires a large amount of irrigating fluids, which may further increase the incidence of shivering. Hypothermia-induced shivering increases total body oxygen consumption and may cause hypoxemia.[5] On the other hand, spinal anesthesia, the technique of choice in TURP, causes impairment of the thermoregulatory function of the autonomic system.[6] Because core temperature monitoring remains rare during regional anesthesia, substantial hypothermia commonly goes undetected.[7] Use of warm irrigation fluid has been shown to be efficacious in reducing heat loss and thus leading to decreased hemodynamic response.[8] In the absence of continuous fluid warmer, prewarmed fluid can be used to prevent hypothermia during TURP. Such measures in the knowledge of the authors were not used earlier in low resource settings. This study was planned to compare the effect of warm or room temperature irrigation fluid in terms of degree of hypothermia and hemodynamic variations in patients undergoing TURP surgery under spinal anesthesia.

METHODS

This randomized prospective study of 40 patients undergoing TURP was conducted after taking approval from institutional ethics committee and written informed consent was obtained from all the patients over a period of 12 months. American Society of Anesthesiologists (ASA) II-III patients in the age group of 50-85 years scheduled for elective TURP under spinal anesthesia were selected. Patients with a history of preexisting severe cardiovascular, respiratory and endocrinal disease, severe anemia requiring blood transfusion, deranged serum electrolytes, and on anticoagulant therapy were excluded from the study. After thorough preoperative check-up all patients were kept fasting for 6 h. Preoperatively diazepam (tablet diazepam 10 mg) was administered a night before and on the morning of surgery with a sip of water.

In the operating room (OR) after establishing intravenous (IV) access, all patients were preloaded with 10 ml/kg of Ringer lactate. All IV fluid used during operation was stored at room temperature. Routine preoperative monitoring was established with electrocardiogram (ECG), noninvasive blood pressure (NIBP) and pulse oximetry (SpO2). Core temperature of the patient was noted with the use of nasopharyngeal temperature probe introduced after thoroughly lubricating the probe and connected to a multi-parameter (Larsen and Toubro, Lunar) L and T anaesthesia monitor, India The temperature of the OR was also noted (electronic operation theater temperature indicator electro expo system, industrial module no. 62, electronic city sector-18, Gurgoan, Haryana, India).

And, it was maintained at 21°C. The patients were then randomly divided into two groups. Randomization was carried out by sealed envelope technique.

Group 1 Patients received Irrigation fluid at room temperature 21°C

Group 2 Patient received Irrigation fluid at 37°C.

All the patients were given subarachnoid block in the sitting position, using 23G Quincke spinal needle and 12.5 mg, 0.5% hyperbaric bupivacaine (Heavy Anawin) by Neon Laboratories Limited, 28 Mahal Ind. Est. M Caves Rd. Andheri (East), Mumbai, India was administered. The patients were then turned to supine position and level of the block was checked by pinprick method. They were covered with theater linen at room temperature during the procedure and were not actively heated. Room temperature was maintained at 21°C When the level of the block reached T10, monopolar resection was performed using cautery with cutting and coagulation setting of 100 and 60 W respectively.

A well-lubricated resectoscope (Olympus winter and Ibe GmbH, Kuchnstr 61, 22045 Hamburg, Germany) and the telescope was used for resection of the prostate. The height of the irrigation fluid was 60 cm in all cases. The temperature of the distilled water as irrigating fluid in Group 1 was similar to room temperature while in Group 2, irrigation fluid was warmed by using incubator (YARCO B.O.D) Yarco sales Pvt. Ltd., New Delhi, India. Before use irrigation fluid was put into irrigation fluid reservoir (sew water bath, scientific equipment works, (India) New Delhi) which was also prewarmed up to 37°C. The temperature of the irrigation fluid was measured with a mercury thermometer put inside the reservoir. All the patients were covered from level of the neck to umbilicus to protect against the heat loss during the procedure. Nasopharyngeal temperature, NIBP, heart rate, SpO2 and ECG were continuously monitored pre-, intra- and postoperatively in each case. The total duration of surgery, amount of irrigation fluid used, and patient's satisfaction was also noted both intra-operatively and postoperatively by the anesthetist who was blinded to the temperature of the fluids selected.

During surgery, shivering score was recorded at 5 min interval. Shivering was graded using a scale similar to that validated by Tsai and Chu.[9] In which Grade 0: No shivering, Grade 1: Piloerection or peripheral vasoconstriction but no visible shivering, Grade 2: Muscular activity in only one muscle group, Grade 3: Muscular activity in more than one muscle group, but not generalized and Grade 4: Shivering involving the whole body.

Sample size

Calculation of sample size was done on the basis of previous studies.[101112] Considering a statistical power (β) of 80%, and α error of 5% and clinically significant of temperature difference of 1°C, a total 16 samples was found in each group. In order to allow for potential data loss, it was planned to recruit 20 patients to each group.

Statistical analysis

Data were represented in the form of mean ± standard deviation. The paired and unpaired t-test was used to compare the mean of two groups and mean within groups at different time interval. P < 0.05 was considered to be statistically significant. Data analysis was performed utilizing SPSS-version 22 (SPSS, Software, IBM Corporation, Amrok, Newyork).

RESULT

There was no statistically significant differences in the two groups concerning base line parameters such as age, height, weight, ASA grade, duration of surgery, amount of irrigation fluid used, and ambient temperature in the OR [Table 1]. The mean block height was T10 in both groups and did not differ between the groups.

Table 1

Baseline characteristics of the patients

Findings indicated that patients who received ambient fluids experienced statistically significant decreases in perioperative temperature when compared to patients who received warmed irrigation fluid. The mean preinduction nasopharyngeal temperature was 36.97 ± 0.054°C (Group 1) and 36.97 ± 0.041°C (Group 2), respectively [Table 2]. The mean final intra-operative core temperature was 34.59 ± 0.142°C (Group 1) and 36.17 ± 0.890°C in (Group 2). The core temperature fall [Figure 1] in the Group 1 was found to be 2.38°C, while temperature fall in the Group 2 was approximately 0.8°C (P < 0.001).

Table 2

Temperature changes of the patients in study groups

Figure 1

Temperature changes from preinduction to postsurgery in study groups. Group 1: Patients received irrigation fluid at room temperature 21°C, Group 2: Patient received irrigation fluid at 37°C

Decreases in heart rate, systolic, diastolic and mean blood pressure were noted in patients of both study groups [Table 3]. The hemodynamic variables including heart rate, systolic/diastolic and mean blood pressure, were comparable between the groups [Figures 2-5]. No significant difference in the hemodynamic parameters was observed between the groups. A significant decrease in systolic blood pressure was observed (P < 0.05) at the end of the surgery. The incidence of shivering was higher in Group 1 (45%), as compared to Group 2 (15%). Shivering of Grades 1 and 2 was observed in nine patients, of Group 1, while only three patients had Grades 1 and 2 shivering in Group 2.

Table 3

Hemodynamic changes at different time interval between the study groups

Figure 2

Changes in heart rate from preinduction to postsurgery in study groups. Group 1: Patients received irrigation fluid at room temperature 21°C, Group 2: Patient received irrigation fluid at 37°C

Figure 5

Changes in mean blood pressure from preinduction to postsurgery in study groups. Group 1: Patients received irrigation fluid at room temperature 21°C, Group 2: Patient received irrigation fluid at 37°C

Changes in systolic blood pressure from preinduction to postsurgery in study groups. Group 1: Patients received irrigation fluid at room temperature 21°C, Group 2: Patient received irrigation fluid at 37°C

Changes in diastolic blood pressure from preinduction to postsurgery in study groups. Group 1: Patients received irrigation fluid at room temperature 21°C, Group 2: Patient received irrigation fluid at 37°C

DISCUSSION

Hypothermia during TURP has received relatively little attention in the urology literature.[13] Irrigating fluids are used widely in endoscopic manipulation of the genitourinary tract in order to dilate the mucosal spaces and to clear the operating field of blood and cut tissue.[14] Use of irrigation fluid for endoscopic surgeries were first reported as a cause of hypothermia that was attributed to greater absorption of fluid contributing to temperature changes.[15]

Our study demonstrates the effectiveness of perioperative warm irrigation fluid in core temperature fall as well as reducing the intra-operative shivering during TURP under spinal anesthesia. We observed core temperature fall in both groups, the changes been less in those patients where irrigation fluid was used at 37°C. The core temperature fall in the group irrigated with fluid at room temperature was found to be 2.38°C, while temperature fall in the group irrigated with warm fluid was approximately 0.8°C at the end of the surgery. In none of the patients, the core temperature fell below 34°C. Mild hypothermia was noted in patients given room temperature irrigant fluid, whereas no patients had hypothermia in other group.

Inadequate warmed irrigation fluid and use of regional anesthesia techniques serve as additional factors for development of hypothermia.[16] Absorption of irrigating fluid at room temperature was postulated as the cause of hypothermia by various authors. Winter has reported a 63% incidence of hypothermia in patients who underwent TURP with room temperature irrigation fluid, compared with only 20% in patients who received warm irrigation fluid.[17]

A study by Okeke[18] and Pit et al.,[8] have demonstrated that patients who received isothermic irrigation fluids had significantly smaller changes in body temperature than those who received them at room temperature. Our findings closely agree with them.

There has been contrasting observations in the literature available regarding use of warm irrigating fluid, and a few studies provide contradictory evidences. Jaffe et al. demonstrated that, irrigation fluid temperature is not a factor responsible for altering the core body temperature in patients undergoing TURP.[19] The factors, which might influence differences in the incidence of hypothermia between our results and other studies could be a different age groups and the difference in the temperature of warm irrigating fluid (33.05°C vs. 37°C) along with no active patient warming and use of unwarm IV fluid.

A further difference between the reported studies and our study is that we did not use in line fluid warmer to maintain the temperature of the irrigation fluid. Similarly no such attempt was made by Kelly et al., who failed to find a positive association between body temperature and irrigation fluid, as the fluid delivered to the patients cooled as the procedure proceeded.[20] Specifically designed warming devices for irrigation fluid rates have been shown to effectively maintain warmed fluid temperature during arthroscopy[6] and laparoscopy.[21] Utilization of such a device would have benefitted the current study by preserving the intended warmed fluid temperature throughout the administration period.

Studies in the literature have shown a figure of approximately a fall of 3°C with irrigation fluid at room temperature. The result of a study by Davoudi et al.,[22] reported a less than 0.5°C decrease in body temperature during the 60-min study period, when used IV and irrigating fluids at room temperature. However, they did not compare the amount of IV or irrigating fluid between groups and did not suggest the relationship of these factors with the fall in temperature. Associated factors like choice of in local anesthetics, sensory block levels, and differences in the temperature of IV fluids between the Davoudi et al.,'s study and our study, which could have influenced body temperature.

Indeed, even when irrigating fluid is warmed up to body temperature, there are studies that show a greater decrease in temperature in TURP when compared to transurethral resection of bladder tumor, probably due to greater absorption of fluid occurring in TURP, indicating that absorption of fluid contributes to temperature change in TURP.[10]

It is common for patients to complain their worst memory from the recovery room is the intense cold sensation and uncontrollable shivering. The study showed that the use of warm irrigation fluid none of our patient had core temperature fall below 36°C. Decrease in number of patients feeling cold and having shivering thus increasing the overall satisfaction of the patient. Our results are in accordance with others.[142324]

Unintended hypothermia can result in adverse consequences to the cardiovascular system.[25] Most of the previous studies that had found a positive effect of warm irrigating fluid on core temperature did not consider hemodynamic status in their observations. Evan in their study, observed a reduction in the heart rate, it could be because they used a large amount of irrigating fluid >11 L/patient at room temperature of 20°C and not at body temperature, which could have resulted in a decrease in core temperature.[26] In our study, in patients of Group 1 and Group 2, changes in the hemodynamic parameters such as heart rate, systolic, diastolic and mean blood pressure was present, but had not reached a significant level. Literature shows that in patients who absorb more fluid in TURP, 75% experienced perioperative hypertension, 25% experienced chest pain and 17% actually had ST-depression on ECG.[14] Our patients in the both groups did not differ in the amount of irrigant fluid required. Decreases in systolic blood pressure and heart rate were noted in patients of both study and that were probably due to the sympathetic block effect of spinal anesthesia.[22] There was no major fall in blood pressure as patient in both groups were preloaded with 10 ml/kg of lactated Ringer, 10 min prior to shifting the patient to operation theater.

For the purposes of temperature monitoring during anesthesia and surgery, the best monitoring sites are those that are closest to blood temperature, which is considered the “true” core temperature. Besides blood temperature in the pulmonary artery, nasopharyngeal, and esophageal temperatures are the most accurate estimates of core temperature.[27] In this study, nasopharyngeal temperature was measured.

Intra-operative hypothermia prevention costs are lower than the cost to treat negative outcomes, such as the need for blood transfusion, that patients are affected due to their hypothermic condition. A meta-analysis demonstrated that, on average, a body temperature drop of more than 1.5°C below normal entailed accumulated negative outcomes, adding between $2.500 and $7.000 of hospital costs per surgical patient.[28]

Limitations of our study are: (1) The benefits to patients in employing continuous fluid warming devices and other external measures to limit heat loss. (2) We did not estimate the concentration of stress response hormones. They might have given us a better understanding of the changes in stress level with hypothermia. (3) When the irrigation fluid is warmed from 17°C-37°C there is a corresponding change in the density and dynamic fluidity of the fluid used for irrigation and this is accompanied by an increase in the mean absorption of the fluid by as much as 54% and this may lead to decrease in the safe period of time for surgery by as much as 65%.[29] In our study, we did not look into this aspect and this is likely to influence our results.

CONCLUSION

This study suggests that using either room temperature or warmed irrigating fluid during TURP could decrease core body temperature. Warmed irrigation fluids are one measure that can be implemented to decrease the magnitude of hypothermia and shivering. Considering the potential of room temperature irrigation fluids to contribute toward significant hypothermia, we recommend warming of irrigation fluids in low resource setting by this simple and uncostly method to normal body temperature before use in an elderly patient.