Ahmed Hasanin

The plethysmographic peripheral perfusion index (PPI) is a very useful parameter with various emerging utilities in medical practice. The PPI represents the ratio between pulsatile and non-pulsatile portions in peripheral circulation and is mainly affected by two main determinants: cardiac output and balance between sympathetic and parasympathetic nervous systems. The PPI decreases in cases of sympathetic predominance and/or low cardiac output states; therefore, it is a useful predictor of patient outcomes in critical care units. The PPI could be a surrogate for cardiac output in tests for fluid responsiveness, as an objective measure of pain especially in un-cooperative patients, and as a predictor of successful weaning from mechanical ventilation. The PPI is simple to measure, easy to interpret, and has continuously displayed variables, making it a convenient parameter for detecting the adequacy of blood flow and sympathetic-parasympathetic balance.

OBJECTIVES: Evaluation of pain in critically ill intubated patients is difficult and subjective. This study aimed to evaluate the accuracy of oximetry-derived peripheral perfusion index (PPI) in pain assessment in critically ill intubated patients using the behavioral pain scale (BPS) as a reference.

MATERIALS AND METHODS: This prospective observational study included 35 adult mechanically ventilated surgical patients during their first 2 postoperative days in the intensive care unit. Values of PPI, BPS, Richmond Agitation Sedation Scale (RASS), heart rate, and blood pressure were obtained before and after a standard painful stimulus (changing the patient position) and the ratio between the second and the first reading was calculated to determine the change (Δ) in all variables. The outcomes were the correlation between ΔBPS and ΔPPI as well as other hemodynamic parameters. The ability of the PPI to detect pain (defined as BPS ≥6) was analyzed using the area under receiver operating characteristic curve.

RESULTS: Paired readings were obtained from 35 patients. After the standard painful stimulus, the PPI decreased while the BPS and the Richmond agitation sedation scale increased. The Spearman correlation coefficient (95% confidence interval) between Δ PPI and Δ BPS was 0.41 (0.09-0.65). PPI values showed poor accuracy in detecting pain with area under receiver operating characteristic curve (95% confidence interval): 0.65 (0.53-0.76), with best cutoff value of ≤2.7.

CONCLUSION: The PPI decreased after application of a standard painful stimulus in critically ill intubated patients. ∆PPI showed a low correlation with ∆BPS, and a PPI of ≤2.7 showed a low ability to detect BPS ≥6. Therefore, PPI should not be used for pain evaluation in critically ill intubated surgical patients.

Supraclavicular nerve block (SCB) is a commonly used regional block for upper extremity surgery. The most common form of failure of SCB is ulnar segmental sparing. We aimed to evaluate the accuracy of perfusion index (PI) in early detection of segmental sparing of the ulnar component of SCB. A prospective observational study included adult patients scheduled for surgery under ultrasound-guided SCB. PI was simultaneously measured at the index finger and little finger. PI was recorded every minute for the first 10 min after SCB. PI ratio was calculated at every measurement point as PI/baseline PI. The area under the receiver operating characteristic (AUROC) curve was calculated for the ability of PI ratio to detect segmental ulnar sparing with comparison of little finger readings to the index finger readings. Forty-nine patients were available for the final analysis. Nine patients (18%) had segmental ulnar sparing. PI ratio at the little finger showed excellent predictive ability for ulnar sparing starting from the fifth minute (AUROC 0.92 [0.8-0.98], cutoff value ≤ 1.71) and reached the highest value at the seventh minute (AUROC 0.96 [0.86-1], cutoff value ≤ 1.35), whereas PI ratio at the index finger showed poor predictive ability. When using the PI for evaluation of successful SCB, segmental ulnar sparing could be accurately detected when the PI was measured at the little finger and not at the index finger. An increase of 71% in PI at the little finger 5 min after SCB could accurately rule out ulnar sparing.Clinical trial identifier NCT03880201. Clinical trial registration https://clinicaltrials.gov/ct2/show/NCT03880201?term=NCT03880201&draw=2&rank=1 .

BACKGROUND: In obese patients, non-invasive blood pressure monitoring in the arm is difficult due to the arm size and morphology. We compared the non-invasive oscillometric wrist blood pressure measurement with the arm and forearm in obese patients monitored with invasive radial blood pressure (reference standard).

METHODS: This prospective observational study included adult obese patients scheduled for bariatric surgery. Non-invasive blood pressure was measured at the arm, upper forearm and wrist of one upper extremity, while invasive blood pressure was simultaneously measured through a radial arterial catheter in the contralateral upper extremity. The accuracy of non-invasive blood pressure reading at each site was evaluated for absolute and trending values using the Bland-Altman analysis and Spearman's correlation coefficient.

RESULTS: In 40 patients, 262, 259, and 263 pairs of non-invasive blood pressure readings were obtained from the arm, forearm, and wrist sites, respectively. As primary outcome, the correlation coefficient for systolic blood pressure was higher for the wrist (0.92, 95% confidence interval (CI) [0.9-0.94]) than for the arm (0.74, 95% CI [0.68-0.79]) and the forearm (0.71, 95% CI [0.64-0.76]) (P<0.05). The non-invasive systolic wrist blood pressure showed the least mean bias and the narrowest limits of agreement (-0.3±7.6mmHg) when compared with forearm (4.3±16) and arm measurements (14.2±13.6) (P<0.05). For trending values, the correlation coefficient was the highest at the wrist.

CONCLUSION: In obese patients undergoing bariatric surgery, non-invasive blood pressure measured at the wrist showed the highest accuracy in comparison with the arm and forearm.

BACKGROUND: Data on the best norepinephrine bolus dose for management of hypotension are limited. The aim of this study was to compare the efficacy and safety of two norepinephrine bolus doses in the rescue management of maternal hypotension during cesarean delivery.

METHODS: This randomized, controlled trial included mothers scheduled for cesarean delivery with spinal anesthesia with a prophylactic norepinephrine infusion. Following spinal anaesthesia administration, a participant was considered hypotensive if systolic blood pressure was ≤80% compared to the baseline reading. Participants were allocated to receive either 6 mcg or 10 mcg norepinephrine bolus for the management of hypotensive episodes. The hemodynamic response after administration of norepinephrine bolus was recorded. The episode was considered successfully managed if systolic blood pressure returned to within 80% from the baseline reading within 2 min after norepinephrine bolus administration, and did not drop again within 6 min after the norepinephrine bolus. The primary outcome was the incidence of successful management of the first hypotensive episode. Other outcomes included systolic blood pressure, heart rate, incidence of maternal bradycardia, and reactive hypertension.

RESULTS: One hundred and ten mothers developed hypotensive episodes and received norepinephrine boluses for management. The number of successfully managed first hypotensive episodes was 50/57 (88%) in the 6 mcg-treated episodes and 45/53 (85%) in the 10 mcg-treated episodes (p = 0.78). Systolic blood pressure was comparable after administration of either bolus dose. Heart rate was lower after administration of 10 mcg bolus compared to 6 mcg bolus, without significant bradycardia requiring atropine administration. The incidence of reactive hypertension was comparable between both groups.

CONCLUSION: In mothers undergoing elective cesarean delivery under prophylactic norepinephrine infusion at 0.05 mcg/kg/min, there was no advantage to the use of 10 mcg norepinephrine bolus over 6 mcg norepinephrine bolus for the rescue management of first hypotensive episode. Neither of the 2 bolus doses reached a 100% success rate. The incidences of bradycardia and reactive hypertension were comparable between both norepinephrine doses.

TRIAL REGISTRATION: At clinicaltrial.gov registry system on January 4, 2019 Clinical trial identifier: NCT03792906.

BACKGROUND: Deliberate hypotension is used to provide a bloodless field during functional endoscopic sinus surgery; however, the impact of controlled hypotension during anesthesia on peripheral tissue perfusion has not been extensively evaluated. The aim of this study was to compare the impact of nitroglycerin- versus labetalol-induced hypotension on peripheral perfusion.

METHODS: The present randomized, double-blinded, controlled trial included adult patients undergoing endoscopic sinus surgery. Patients were allocated to one of two groups according to the drug received for induction of deliberate hypotension: nitroglycerin (n = 20) or labetalol (n = 20). Mean arterial pressure was maintained at 55-65 mmHg in both groups. Both study groups were compared according to pulse oximeter-derived peripheral perfusion index (primary outcome), serum lactate level, mean arterial pressure, heart rate, surgical field score, and intraoperative blood loss.

RESULTS: Forty patients were included in the final analysis. The nitroglycerin group exhibited a higher peripheral perfusion index at nearly all records (p < 0.0001) and lower postoperative serum lactate levels (1.3 ± 0.2 mmol/L vs. 1.7 ± 0.4 mmol/L; p = 0.001) than the labetalol group. The peripheral perfusion index was higher in the nitroglycerin group than at baseline at most intraoperative readings. The median surgical field score was modestly lower in the labetalol group than in the nitroglycerin group in the first 20 min (2 [interquartile range (IQR) 2-2.5] versus 1.5 [IQR 1-2]; p = 0.001). Both groups demonstrated comparable and acceptable surgical field scores in all subsequent readings.

CONCLUSION: Nitroglycerin-induced deliberate hypotension was accompanied by higher peripheral perfusion index and lower serum lactate levels than labetalol-induced deliberate hypotension during sinus endoscopic surgery.

TRIAL REGISTRATION: The study was registered at clinicaltrials registry system with trial number: NCT03809065. Registered at 19 January 2019. This study adheres to CONSORT guidelines.

BACKGROUND: Noninvasive measurement of blood hemoglobin could save time and decrease the risk of anemia and infection. The accuracy of CO-oximetry-derived noninvasive hemoglobin (Sp-Hb) had been evaluated in pediatric population; however, its accuracy in children with congenital heart disease has not been studied till date. We evaluated the accuracy of Sp-Hb in relation to laboratory-measured hemoglobin (Lab-Hb) in children with congenital heart disease.

METHODS: This prospective observational study included children with congenital heart disease undergoing procedural intervention. Sp-Hb measurements were obtained using Radical-7 Masimo pulse CO-oximeter and were compared against simultaneous Lab-Hb measurements obtained from the arterial line. Children were divided in cyanotic and acyanotic, and separate analysis was performed for each group. The values of both measurements were analyzed using Spearman's correlation coefficient and Bland-Altman analysis. Correlation was performed between Sp-Hb and Lab-Hb bias and each of arterial oxygen saturation and perfusion index.

RESULTS: One-hundred and eleven pairs of readings were obtained from 65 children. The median (quartiles) age and weight of the children were 1 (1.2-4) years and 11 (8-17) kg, respectively. There was moderate correlation between Lab-Hb and Sp-Hb with a correlation coefficient (95% confidence interval [CI]) of 0.75 (0.63-0.83) in acyanotic children and 0.62 (0.37-0.79) in cyanotic children. The mean bias (95% limits of agreements) was -0.4 g/dL (-2.4 to 1.6 g/dL) and 1 g/dL (-2.7 to 4.6 g/dL) in acyanotic and cyanotic children, respectively. The mean bias between Sp-Hb and Lab-Hb showed a weak negative correlation with oxygen saturation (r [95% CI]): (-0.36 [-0.51--0.18]), and a weak positive correlation with the perfusion index (r [95% CI]): (0.19 [0.01-0.37]).

CONCLUSION: The large bias and the wide limits of agreement between Sp-Hb and Lab-Hb denote that Masimo-derived Sp-Hb is not accurate in children with congenital heart disease especially in the cyanotic group; the error in Sp-Hb increases when oxygen saturation decreases.

BACKGROUND: Endotracheal intubation requires optimum position of the head and neck. In obese females, the usual ramped position might not provide adequate intubating conditions. We hypothesized that a new position, termed modified-ramped position, during induction of anesthesia would facilitate endotracheal intubation through bringing the breasts away from the laryngoscope and would also improve the laryngeal visualization.

METHODS: Sixty obese female patients scheduled for general anesthesia were randomly assigned into either ramped or modified-ramped position during induction of anesthesia. In the ramped position (n = 30), the patient head and shoulders were elevated to achieve alignment of the sternal notch and the external auditory meatus; while in the modified-ramped position (n = 30), the patient shoulders were elevated using a special pillow, and the head was extended to the most possible range. Our primary outcome was the incidence of failed laryngoscopic insertion in the oral cavity (the need for patient repositioning). Other outcomes included time till vocal cord visualization, time till successful endotracheal intubation, difficulty of the mask ventilation, and Cormack-Lehane grade for laryngeal view.

RESULTS: Fourteen patients (47%) in ramped group required repositioning to facilitate introduction of the laryngoscope in the oral cavity in comparison to one patient (3%) in the modified-ramped position (p < 0.001). Modified-ramped position showed lower incidence of difficult mask ventilation, shorter time for glottic visualization, and shorter time for endotracheal tube insertion compared to the ramped position. The Cormack-Lehane grade was better in the modified-ramped position.

CONCLUSION: Modified-ramped position provided better intubating conditions, improved the laryngeal view, and eliminated the need for repositioning of obese female patients during insertion of the laryngoscope compared to ramped position.

CLINICAL TRIAL REGISTRATION: Identifier: NCT03640442. Date: August 2018.

The evolution of non-invasive hemoglobin measuring technology would save time and improve transfusion practice. The validity of pulse co-oximetry hemoglobin (SpHb) measurement in the perioperative setting was previously evaluated; however, the accuracy of SpHb in different volume statuses as well as in different perfusion states was not well investigated. The aim of this work is to evaluate the accuracy and trending of SpHb in comparison to laboratory hemoglobin (Lab-Hb) during acute bleeding and after resuscitation. Seventy patients scheduled for major orthopedic procedures with anticipated major blood loss were included. Radical-7 device was used for continuous assessment of SpHb, volume status [via pleth variability index (PVI)] and perfusion status [via perfusion index (PI)]. Lab-Hb and SpHb were measured at three time-points, a baseline reading, after major bleeding, and after resuscitation. Samples were divided into fluid-responsive and fluid non-responsive samples, and were also divided into high-PI and low-PI samples. Accuracy of SpHb was determined using Bland-Altman analysis. Trending of SpHb was evaluated using polar plot analysis. We obtained 210 time-matched readings. Fluid non-responsive samples were 106 (50.5%) whereas fluid responsive samples were 104 (49.5%). Excellent correlation was reported between Lab-Hb and SpHb (r = 0.938). Excellent accuracy with moderate levels of agreement was also reported between both measures among all samples, fluid non-responsive samples, fluid-responsive samples, high-PI samples, and low-PI samples [Mean bias (limits of agreement): 0.01 (- 1.33 and 1.34) g/dL, - 0.08 (- 1.27 and 1.11) g/dL, 0.09 (- 1.36 and 1.54) g/dL, 0.01 (- 1.34 to 1.31) g/dL, and 0.04 (- 1.31 to 1.39) g/dL respectively]. Polar plot analysis showed good trending ability for SpHb as a follow up monitor. In conclusion, SpHb showed excellent correlation with Lab-Hb in fluid responders, fluid non-responders, low-PI, and high PI states. Despite a favorable mean bias of 0.01 g/dL for SpHb, the relatively wide levels of agreement (- 1.3 to 1.3 g/dL) might limit its accuracy. SpHb showed good performance as a trend monitor.

OBJECTIVE: Bleeding is a leading cause of death among trauma patients. Delayed assessment of blood hemoglobin level might result in either unnecessary blood transfusion in nonindicated patients or delayed blood transfusion in critically bleeding patients. In this study, we evaluate the precision of noninvasive hemoglobin monitoring in trauma patients with low hemoglobin levels.

METHODS: We included trauma patients with low hemoglobin levels (less than 8 g/dL) scheduled for surgical intervention. Blood samples were obtained on admission and after each blood unit with concomitant measurement of serum hemoglobin using radical-7 Masimo device. The change in blood hemoglobin after every transfused blood unit was also assessed by both methods (change in noninvasive Masimo hemoglobin [Delta-Sp-Hb] and change in laboratory hemoglobin [Delta-Lab-Hb]). The precision of Masimo hemoglobin level (Sp-Hb) compared with Laboratory hemoglobin level (Lab-Hb) was determined using both Bland-Altman and Pearson correlation analyses.

RESULTS: One hundred eighty-four time-matched samples were available for final analysis. Bland-Altman analysis showed excellent accuracy of Sp-Hb compared with Lab-Hb with mean bias of 0.12 g/dL and limits of agreement between -0.56 g/dL and 0.79 g/dL. Excellent correlation was reported between both measures with Pearson correlation coefficient of 0.872. Excellent agreement was also reported between both Delta-Sp-Hb and Delta-Lab-Hb with mean bias of -0.05 and limits of agreement from -0.62 to 0.51 CONCLUSIONS:: Sp-Hb showed accurate precision in both absolute values and trend values compared with Lab-Hb measurement in trauma patients with low hemoglobin levels.

BACKGROUND: Post-spinal hypotension is a common maternal complication during cesarean delivery. Aortocaval compression by the gravid uterus has been assumed as a precipitating factor for post-spinal hypotension. The role of left lateral tilting position in improving maternal cardiac output after subarachnoid block (SAB) is unclear. The aim of this work is to investigate the effect of left lateral tilting on maternal hemodynamics after SAB.

METHODS: A prospective observational study was conducted including 105 full term pregnant women scheduled for cesarean delivery. Mean arterial pressure, heart rate, cardiac output (measured by electrical cardiometry), stroke volume, and systemic vascular resistance were recorded in three positions (supine, 15, and 30left lateral positions) before SAB, after SAB, and after delivery of the fetus.

RESULTS: Before SAB, no significant hemodynamic changes were reported with left lateral tilting. A significant decrease was reported in mean arterial pressure, cardiac output, stroke volume, and systemic vascular resistance after SAB (in supine position). When performing left lateral tilting, there was an increase in cardiac output, heart rate, and mean arterial pressure. No difference was reported between the two tilt angles (15and 30).

CONCLUSIONS: Changing position of full term pregnant woman after SAB from supine to left lateral tilted position results increased cardiac output and mean arterial pressure. There is no difference between the two tilt angles (15and 30).

TRIAL REGISTRATION: clinicaltrials.gov ( NCT02828176 ) retrospectively registered.

Background: Supraclavicular nerve block is a popular approach for anaesthesia for upper limb surgeries. Conventional methods for evaluation of block success are time consuming and need patient cooperation. The aim of this study was to evaluate whether the perfusion index (PI) can be used to predict and provide a cut-off value for ultrasound-guided supraclavicular nerve block success.

Methods: The study included 77 patients undergoing elective orthopaedic procedures under ultrasound-guided supraclavicular nerve block. After local anaesthetic injection, sensory block success was assessed every 3 min by pinprick, and motor block success was assessed every 5 min by the ability to flex the elbow and the hand against resistance. The PI was recorded at baseline and at 10, 20, and 30 min after anaesthetic injection in both blocked and non-blocked limbs. The PI ratio was calculated as the PI after 10 min divided by the PI at the baseline. Receiver operating characteristic curves were constructed for the accuracy of the PI in detection of block success.

Results: The PI was higher in the blocked limb at all time points, and this was paralleled by a higher PI ratio compared with the unblocked limb. Both the PI and the PI ratio at 10 min after injection showed a sensitivity and specificity of 100% for block success at cut-off values of 3.3 and 1.4, respectively.

Conclusions: The PI is a useful tool for evaluation of successful supraclavicular nerve block. A PI ratio of > 1.4 is a good predictor for block success.