|Year : 2015 | Volume
| Issue : 2 | Page : 182-188
A comparison between nitroprusside and nitroglycerine for hypotensive anesthesia in ear, nose, and throat surgeries: A double-blind randomized study
Abhishek Mishra, Raj Bahadur Singh, Sanjay Choubey, Rajni K Tripathi, Arindam Sarkar
Department of Anaesthesiology and Critical Care, Era's Lucknow Medical College and Hospital, Lucknow, Uttar Pradesh, India
|Date of Web Publication||13-Mar-2015|
Raj Bahadur Singh
Department of Anaesthesiology, Era's Lucknow medical College and Hospital, Lucknow - 226 003, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
Context: Blood obscures the operative field and makes precise technique difficult, and to the anesthetist, when the volume of blood lost is large. Practice of induced hypotension in the otolaryngology is a common practice owing to its benefits in providing a better visibility and preventing blood loss. Aims: The aim was to compare controlled induced hypotension for facilitating surgical exposure, and reducing intraoperative blood loss using sodium nitroprusside and nitroglycerin in ear, nose, and throat surgeries under general anesthesia. Settings and Design: A prospective, randomized, double-blind study. Materials and Methods: The study was carried out in 60 adults, American Society of Anesthesiologists grade I and II patients, allocated randomly in to three groups: group A was control group, group B patients received nitroprusside (0.5-10 μg/kg/min) and group C patients received nitroglycerine (1-10 μg/kg/min). Mean arterial pressure was maintained in the range of 50-60 mmHg. Statistical Analysis Used: Statistical Package for Social Sciences version 17.0 (ANOVA) followed by independent samples t-test and Chi-square test. Results: The results of the present study indicate that the use of controlled hypotension provides a better surgical field and reduces the blood loss. Of the two modalities under question, use of sodium nitroprusside gives the desired results in a significantly, shorter time as compared to nitroglycerin; however, the use of sodium nitroprusside must be carried out with caution as it has toxic effects. Conclusions: (1) The achievement of target level was quicker in sodium nitroprusside group as compared to nitroglycerin group. (2) Reflex tachycardia was the main side effect of the nitroglycerin group. (3) Rebound hypertension was the associated side effect of the sodium nitroprusside group.
Keywords: Hypotensive anesthesia, nitroglycerin, nitroprusside
|How to cite this article:|
Mishra A, Singh RB, Choubey S, Tripathi RK, Sarkar A. A comparison between nitroprusside and nitroglycerine for hypotensive anesthesia in ear, nose, and throat surgeries: A double-blind randomized study. Med J DY Patil Univ 2015;8:182-8
|How to cite this URL:|
Mishra A, Singh RB, Choubey S, Tripathi RK, Sarkar A. A comparison between nitroprusside and nitroglycerine for hypotensive anesthesia in ear, nose, and throat surgeries: A double-blind randomized study. Med J DY Patil Univ [serial online] 2015 [cited 2019 Dec 10];8:182-8. Available from: http://www.mjdrdypu.org/text.asp?2015/8/2/182/153153
| Introduction|| |
Ever since surgery began, bleeding has been a problem both to the surgeon, when blood obscures the operative field and makes precise technique difficult, and to the anesthetist, when the volume of blood lost is large. The difficulties for the surgeon are greater, when the operation involves very small structures, often located in confined cavities, like the middle ear. In such situations, even small amount of blood makes successful reconstructive surgery very difficult or, sometimes, impossible. It is generally, agreed that a reduction in blood pressure (BP) is useful, though often essential, in these types of surgery.
The aim of our study was to compare controlled induced hypotension for facilitating surgical exposure and reducing intraoperative blood loss, using sodium nitroprusside and nitroglycerin in ear, nose, and throat (ENT) surgeries under general anesthesia.
| Materials and Methods|| |
The present study was a prospective, randomized, double-blind study carried out in 60 adults of American Society of Anesthesiologists (ASA) grade I and II after obtaining the requisite Hospital Ethics Committee approval. ASA grade III and IV patients, patients with a significant coronary artery disease or ischemic myocardial disease, patients with chronic pulmonary disease, renal failure, hepatic dysfunction, patients with history of hypertension, and patients sensitive to nitroprusside and nitroglycerin were excluded. Patients were allocated randomly into three groups: Group A (control group), group B (nitroprusside-controlled hypotension), and group C (nitroglycerin-controlled hypotension)
Mandatory monitoring included direct intra-arterial BP monitoring, heart rate (HR), oxygen saturation (SpO 2 ), electrocardiogram, and urine output, if required. Direct intra-arterial monitoring was done by cannulating the radial artery.
The patients were visited a day prior for preanesthetic review, and the standard institutional preoperative advice was given. For evaluating the visibility of the operative field during ENT surgeries, the quality scale Fromm and Boezzart  was used [Table 1].
After wheeling the patients into the operation theatre, they were connected to all noninvasive monitors for baseline parameters including HR, arterial noninvasive blood pressure, and SpO 2 . Invasive blood pressure monitoring was done by cannulating the radial artery, and connecting it to the transducer. Before the induction of anesthesia, all patients were premedicated on table with a standardized protocol using glycopyrrolate 6 μg/kg and fentany l 2 μg/kg intravenously. All patients were preoxygenated with 100% oxygen for 3 min, thereafter induced with propofol 2 mg/kg body weight. Intubation was carried out with succinylcholine 2 mg/kg. All patients were mechanically, ventilated with a fresh flow of oxygen and nitrous oxide (40:60 ratio). Hypotensive agents were started just after intubation. In group A, patients underwent surgery without being given any hypotensive agent, and it served as a control group. In group B, hypotension was maintained with nitroprusside in the range of 0.5-10 μg/kg/min, while in group C, nitroglycerin was administered in the range of 1-10 μg/kg/min, through infusion pumps. The aim was to maintain mean arterial pressure (MAP) in the range of 50-60 mmHg, without any complications. First bolus dose of atracurium 0.5 mg/kg was given on the return of respiration followed by 0.1 mg/kg as clinically indicated (on return of respiration). The effect of hypotension was recorded comparing the change in the HR and BP at 5-min intervals. Hypotensive agent infusion was discontinued 15 min before surgeries were over. Patients were reversed with neostigmine 50 μg/kg and glycopyrrolate 10 μg/kg intravenously. Patients were then extubated and transferred to the postoperative ward for further monitoring.
| Results|| |
The patients were comparable to each other in terms of the demographic profile [Table 2]. Immediately after infusion, the mean HR of groups B and C showed an increment, which continued till 65 min postinfusion time. At 70 and 75 min postinfusion intervals, no statistically significant difference in mean HR among groups was observed (P > 0.05). While shifting the patients, none of the groups showed any significant difference in HR [Table 3]. When the three groups were compared, the mean HR in groups B and C was found to be significantly, higher as compared to that in group A, from immediately after starting infusion till 65 min postinfusion (P < 0.001). From 20 min postinfusion till 60 min postinfusion interval, the mean HR in group B was found to be significantly higher as compared to group C (P ≤ 0.001) [Table 4].
In all three groups, the mean MAP did not show a significant difference till the time of infusion. After infusion, the mean MAP in groups B and C showed a significantly, lower mean value as compared to that in the group A [Table 5]. On the comparison between the three groups, the mean MAP of group A was significantly higher as compared to groups B and C, respectively, from 5 min postinfusion interval till 60 min postinfusion. Mean MAP of group B was found to be significantly lower as compared to that of group C from 5 min postinfusion to 30 min postinfusion, whereas mean MAP of group B was significantly higher as compared to group C from 30 min postinfusion to 65 min postinfusion except at 35 min postinfusion when the difference between two groups was not significant statistically (P = 0.252).
At all-time intervals, the SpO 2 in the range of 98-100%. At none of the time intervals, a statistically significant difference among groups was observed (P > 0.05) [Table 6].
Mean time to achieve hypotension was 18.25 ± 2.45 min in group B, whereas, in group C, it was 30.00 ± 5.13 min. The time to achieve hypotension was significantly lower in group B as compared to group C (P < 0.001). In group A, at no time interval, the MAP was in the range 50-60 mm of Hg [Graph 1 [Additional file 1]].
Mean score for surgical ease (Fromm and Boezzart criteria) was observed to be 3.50 ± 0.51 in group A, followed by 2.65 ± 0.49 in group C, and minimum for group B (2.40 ± 0.50). The difference was found to be significant among groups (P < 0.001) [Graph 2].
Intergroup comparisons revealed that both groups B and C had significantly a better quality of the surgical field as compared to the group A (P < 0.001). However, no statistically significant difference was observed between groups B and C (P = 0.183) [Table 7].
None of the patients in any group had toxicity. Reflex tachycardia was observed in three patients of group C and rebound hypertension was observed in three patients of Group B. Statistically, a significant difference among groups was seen for reflex tachycardia and rebound hypertension (P = 0.042) [Graph 3].
| Discussion|| |
Tympanoplasty surgeries involve various methods and agents administered to minimize bleeding in the surgical area. If inhaled anesthetics are used to decrease BP, larger inspired concentrations are used than required to provide surgical anesthesia, and this can result in more bleeding because of the peripheral vasodilator effects of these anesthetics.  Therefore, use of additional medications with hypotensive effects is more appropriate.
Use of controlled hypotension to obtain better surgical conditions during tympanoplasty has been well-reported in the literature. , Although some researchers have raised doubt on the efficiency of induced hypotension in reducing blood loss, there is enough evidence to support that controlled/induced hypotension significantly decreases blood loss.  In the present study, we observed that compared to the control group (group A), both study groups (groups B and C) had significantly lower blood loss and significantly a better surgical conditions. Between the two study groups, though no significant difference was observed for surgical conditions, yet the time to achieve the desired level of hypotension was significantly shorter in group B (sodium nitroprusside) as compared to group C (nitroglycerin). Similar findings have been made by Porter et al.  and Yaster et al.,  who reported sodium nitroprusside to be more effective in inducing hypotension as compared to nitroglycerin in patients undergoing spinal surgery. In another study comparing nitroprusside, nitroglycerin, and deep isoflurane anesthesia for induced hypotension, Maktabi et al.  did not find a clear superiority of any agent over the other to induce hypotension, although nitroprusside appeared to be better than nitroglycerin in inducing hypotension. However, Tobias  compared nitroprusside and nitroglycerin to produce induced hypotension during coronary artery surgery and found that both drugs significantly, decreased arterial pressure without affecting the HR or cardiac output.
Beierholm et al.  in their study found that HR, central venous pressure, and pulmonary vascular resistance did not change significantly following infusion of sodium nitroprusside. However, Landauer found that the infusion of sodium nitroprusside was accompanied by a 22.5% increase in HR. In the present study, an increase in HR was observed both in sodium nitroprusside and nitroglycerin groups. But HR in the nitroglycerin group remained at a significantly higher level than in the sodium nitroprusside group. Suttner et al.  also made similar observations, though the extent of the rise in HR was not up to the extent as observed in the present study. Similar findings have been observed in animal models too. 
In group C (nitroglycerin), three cases with reflex tachycardia (15%) were reported. Khan and Carleton  have cautioned the use of nitroglycerin for induction of hypotension owing to its role in the causation of reflex tachycardia.
As in our study, Rodrigo  also reported absence of rebound hypertension with nitroglycerin. In our study, three cases with rebound hypertension were reported with nitroprusside. It has been reported that if an adequate reduction in BP is not achieved in 10-15 min at the highest recommended dose of sodium nitroprusside, the infusion should be stopped to prevent cyanide toxicity.  However, in the present study, no such toxicity was noticed, though the time to achieve desired hypotension reached 25 min. This might be due to rational use of the dose instead of using the maximum permissible dose.
The mean time of onset was observed to be 18.25 ± 2.45 min in the sodium nitroprusside group, whereas, in the nitroglycerin group, this time was 30.00 ± 5.13 min. At the highest dose, the time to achieve the target level of hypotension in the sodium nitroprusside group has been reported to be 10-15 min. However, in the present series, the earliest onset was 15 min. There are different reports regarding the time to achieve controlled hypotension by using sodium nitroprusside. Halpern et al.  have reported a mean time of 30 min. The time taken to achieve the desired level of hypotension generally depends on the dose being used. Owing to the known toxic effects of sodium nitroprusside, the present study adopted an approach of optimal use instead of maximum use. However, even this optimum approach produced significantly better results as compared to nitroglycerin.
The results of the present study indicate that the use of controlled hypotension provides better surgical field and reduces blood loss. Of the two modalities under question, use of sodium nitroprusside gives the desired results in a significantly shorter time as compared to nitroglycerin; however, the use of sodium nitroprusside must be carried out with caution as it has toxic effects. One of the shortcomings of the controlled hypotension is the time taken to achieve the desired MAP level. However, this could be offset with the fact that it reduces blood loss to a significant degree, and thus provides a better surgical field, which not only reduces the overall surgical time but also provides scope for a better surgical outcome. Although in the present study, no attempt was made to compare the results of surgical outcomes, it was observed that the overall surgical time despite a substantial time being taken to achieve the desired MAP levels, was shorter in the two study groups as compared to the control group.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]