OCTA Signal Quality Augmentation Using the Isometric Handgrip Test to Maximize Vascular Flow (SQUEEZE): A Randomized Crossover Trial

Purpose

To determine if performing the isometric handgrip test (IHGT) can augment optical coherence tomography angiography (OCTA) vascular signal quality in eyes with macular abnormalities.

Methods

A randomized, single-blinded crossover trial was conducted including 36 participants with macular abnormalities, randomized to undergo OCTA with or without the IHGT, then crossed over to the alternate "intervention" after 1 minute. The primary outcome was OCTA signal quality after 1 minute of squeezing at 50% maximum grip strength. Secondary outcomes were other measures of vascular flow and systemic blood pressure (BP), also regressed against person- and eye-level covariables.

Results

Primary analysis of OCTA signal quality with versus without the IHGT was nonsignificant (P = 0.73). Nested analyses showed that the IHGT resulted in increased OCTA B-scan retinal vascular flow signal (2.95 [-1.64 to 7.55] Δ%, P < 0.05) and increased systolic BP, diastolic BP, pulse pressure, and mean arterial pressure (4.94 [0.41 to 9.47] to 12.38 [8.01 to 16.75] mm Hg, P < 0.05). OCTA signal quality and en face vessel density and perfusion changes were associated with sex, refraction, race/ethnicity, and right-hand IHGT use (P < 0.05). Greater increases in systolic and diastolic BP and mean arterial pressure were generally associated with right-hand IHGT use and greater maximum grip strength (P < 0.09).

Conclusions

The IHGT can temporarily increase OCTA B-scan retinal vascular flow signal in participants with macular abnormalities. IHGT-induced changes to systemic BP appear to be linked to absolute (rather than relative) grip strength, implying that the IHGT may be ineffective with low grip strength. Further research in larger populations is warranted.

Translational Relevance

This study provides early validation that the IHGT may augment OCTA output, which may lead to improved noninvasive detection of pathologic vascular changes.

Nebulised fentanyl, dexmedetomidine and magnesium sulphate for attenuation of haemodynamic response to laryngoscopy and tracheal intubation: A double-blinded, randomised comparative study

Background and Aims

Direct laryngoscopy and tracheal intubation cause an increase in heart rate (HR) and blood pressure, called as pressor response. This study aimed to compare nebulised forms of fentanyl, dexmedetomidine and magnesium sulphate to attenuate the haemodynamic response to laryngoscopy and tracheal intubation.

Methods

This double-blinded, randomised study was conducted on 90 patients undergoing elective surgery requiring endotracheal intubation. Nebulisation was done with fentanyl 1 μg/kg (Group A), dexmedetomidine 1 μg/kg (Group B) and magnesium sulphate (MgSO4) (40 mg/kg) (Group C). Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) and HR were recorded before nebulisation (T0), post-nebulisation (T1) and at 2, 5 and 10 min after intubation (T2, T3, T4). The statistical analysis for comparing continuous variables between the groups was performed using analysis of variance (ANOVA), and a P value <0.05 was considered statistically significant.

Results

Compared to T0, an increase in HR at T2 and T3 was seen in Group A only, which reached baseline values at T4 (P values <0.0001 and 0.037, respectively). No HR value was higher than the baseline readings in groups B and C. The decreasing trend of SBP, DBP and MAP was seen in all three groups. Groups B and C had a statistically significant decrease in all the values from baseline (P values <0.0001).

Conclusion

Nebulised form of dexmedetomidine (1 μg/kg) and magnesium (40 mg/kg) seems to be superior to fentanyl (1 μg/kg) in blunting the stress response to laryngoscopy and tracheal intubation.

Angiotensin II: A Review of Current Literature

Up to one-third of all patients admitted to intensive care units carry a diagnosis of shock. The use of angiotensin II is becoming widespread in all forms of shock, including cardiogenic, after the U.S. Food and Drug Administration's (FDA's) initial approval for vasoplegic shock in 2017. Here, the authors review the literature on angiotensin II's mechanism of action, benefits, and future therapeutic opportunities.